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  1. #1
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    Jul 2012
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    Default 40T Hydraulic Press

    A project me and a mate have been chipping away at, and I thought the other day...why dont I make a thread about it!

    My friend lives on a family farm, growing wheat and rice and of course, said farm has a workshop for doing bits and pieces to keep the farm going. My friend hasnt inherited the farm yet, he's only just finished school and is now working his way through a fitting and turning apprenticeship at one of the local engineering firms. One day we got talking about some hydraulic bits and pieces he was working on and I mentioned that Id not played with hydraulics before, something I would like to have a go at though. Long conversation shortened up, he and I decided to make a 20T press for his farm, and dad (the farm) will pay for it. We had a yarn with dad, who agreed to foot the bill and pay for any tooling i required as payment for my time.

    Now, im aware that payment in tooling seems odd, especially given that I designed this thing from scratch and would likely be doing the majority of the making. However, Ive no prior experience in hydraulics, so charging money for "expert" knowledge is a bit of a stretch. Also, this is a hobby for me. I have a job that pays well enough and I dont particularly want the pressure of knowing this is another paid job on top of something that should be enjoyable. All that said, Ive recieved two mitutoyo micrometers that pad out my collection to 125mm range and a 50-150mm mitu bore mic, which is a super awesome thing. There has also been plenty of sundries supplied, inserts and endmills for example. At the end of the job, ill have plenty of gear left over.

    So with all the particulars sorted out, it was time to get the ball rolling...

    Design

    We started out by defining the basic specs. We aimed for as long a stroke as we could manage given the equipment on hand (a Hercus 260 lathe being the limiting factor there) and ended up with 316mm of travel for the ram. With that in mind, I set out speccing the rest of the system required to get that stroke to operate at a minimum of 20T and to operate "fairly quickly". 3ph power is available at the farm, so bigger motors are no problem. Specifying the components from there gets quite technical, and I got sucked right into a rabbit hole of formulas and thousands of combinations of pumps, flow rates, horsepower and peak pressures to juggle to find an adequate solution. I defined more components that were not able to be made any bigger - we had a limit of swing on the lathe to contend with, and so I settled on a cylinder ID of 125mm. This left the cylinder caps with OD's of 150mm and 200mm for top and bottom, which was approaching the useable limit for the little hercus. With a cylinder ID of 125, the required pressure to reach 20T to be around the 2100psi / 145bar mark. Easy, plenty of pumps will do that. However, shopping around found some parker dual stage pumps thatll do 4600psi / 320bar. The dual staging is nice, you get the quick travel of the ram down to the workpiece, then it automagically swaps to the low volume pump to do the heavy pushing. 320bar pumps dont seem to grow on trees though, I couldnt find a whole heap of people making them reach that pressure, but I designed with that pump as the "worst" case scenario. With that pressure on hand, the press would deliver 40T pressing force.

    With those basic specs now defined, the rest of the puzzle came together a bit more easily.

    Ram Sectioned View.JPG

    I designed the ram with high rigidity and long service life in mind. Most presses this size use 50mm ramshafts, I went with 70mm. Most pistons, especially on cheap hydraulics, have one microscopic guide ring. I went with two, and I got the widest ones I could reasonably fit. Im a big fan of overbuilt, overbuilt means nobody has to go to hospital with broken bits of ram sticking out of their arm. Farmers dont tend to service things like this regularly, they tend to wait until it fails and then repair it. When it comes to seals and guides, theyre gunna be waiting a while before that happens.

    A noteable part of the design, perhaps a bit of an odd one compared to most hydraulic cylinders, is the end cap design. There are two common methods used, either thread the cylinder and the cap, or to use tie rods to draw the opposing caps together. I ruled out the former because the little hercus was going to be well out of its depth cutting the female thread in the cylinder. With the length specified, there was little room left on the end of the bed for the carriage to live while doing threading, never mind the demands placed on it thanks to rigidity and the tougher nature of the metals involved. Also problematic was that the fixed steady that comes with the lathe is nowhere near big enough to swallow 150mm of tube. I wanted to go with a tie rod design because all the components could be made in house easily. Id gone with purchased tie rods with rolled threads and made the caps accordingly with the machinery in the shed. However, my mate was not so convinced. He threw out a suggestion that was in use on his workshop's 150T press - why not use a series of small screws to secure the end caps into the cylinder. It ticked a box in that it was achieveable and apart from screws, was manufactureable with equipment on hand. The blind cap was easy to do, 20 M8x1.0 12.9 grade SHCS's secure it in place. Itll survive over 60T with that arrangement.

    The gland end cap was a little more tricky. One of the reasons I liked the tie rod idea was because it made getting fluid into the cylinder (which is double acting, unlike a lot of smaller presses) so much easier. With 20 M8 screws crowding the place, getting fluid in was a lot harder. Also, the choice of a 70mm ram was also squeezing things somewhat. It meant a rod seal that was 85mm OD and a buffer seal that was another 0.5mm bigger again. The design brief stating "fairly quickly" meant that hoses and passageways for hydraulic fluid would be ideally around the 1/2in mark. Some of the walls between features in the cap were awfully thin. With a bit of reasoning, some walls could stay thin - pressure between the groove for the buffer seal and the inlet was going to be equalised, that seal is there to soften the blow on the biggun further down the cap. The walls between the rod seal and the inlet gallery were around 6mm at their thinnest. However, its two tangental round features, so the thin part isnt of a large area. The pressure difference between the two should be minimal also because of the location of the features means they should both see similar pressures at the same time. With equalised pressures, there is no load on that thin section. Finally, if the thin areas did fail, the failure would be internal, meaning nobody had to explain why someone's arm got cut off with a 320bar stream of hydraulic fluid. The gland end cap also lost one of the retaining screws that the blind end has, but because the effective area is smaller, its load is significantly reduced. Also...its only going to see pressure on the upstroke. Nobody presses stuff backwards!

    The workshop drawing ended up something like this...

    Gland End Cylinder Cap WSD.jpg

    The rest of the design for the ram came together pretty easily. the SKF documentation is a lifesaver, they give you all the required machining specs, tolerable radius' and clearances. Interesting to note, hydraulic seals are at serious risk of being extruded out of any available gaps and that inclination to escape only goes up with pressures. Given we were looking at the higher end of regularly used pressures at 40T, tolerances and clearances were pretty tight. Where possible, I used ISO compliant seal sizes so that should someone need to replace all these bits and bobs some time in the future, they were necessarily tied to SKF parts alone.

    The design for the press frame was quite straight forward from there. It uses pretty straight forward materials - large C channel for the top and table, large rectangular barstock for the uprights. Its bolted together so that the press is disassembleable, should that ever be required. Some welded in stiffening ribs here and there to make sure its stays the way it should and it was all done. The frame is capable of a little over 80T, with the table pins failing first. Should they manage to survive, the bolts holding the top in place will go next, but dead set...theres gunna be a lot of warning that youre pushing the friendship.

    Final design:

    40T Press.jpg

    A hair over 500kg without any fluids or the rest of the hydraulic paraphinalia.

    Thatll do for computerin' and noodle scratchin, time to hit the shed and start making chips...

  2. #2
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    May 2011
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    Murray Bridge S Aust.
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    Looking forward to seeing the end results, never heard of someone making their own hydraulic ram!!!!
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
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    Jul 2012
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    Ram

    This was the first component finished and unfortunately, I didnt think to take any photos of it during its creation, so youll have to do with an image of the completed item. (edit, did find some actually!)

    Only a few things to note with the production of this component. First of all, when youre going to machine any chrome ramshaft, youve gotta get underneath the chrome. You can forget plunging into it, aint gunna happen, at least not on any hercus ex-school lathe. It can be done with HSS because the chrome is so brittle and thin, as the tool deforms metal in front of it, the chrome fractures and comes off as dust. That dust, I believe, isnt particularly good for you and isnt particularly good for the lathe bed. My machine is pretty clapped out, so my concern is minimal for the lathe, and if you run a bit of oil on the shaft, itll tame the dust. At this point of the project, I was using a TNMG 160408 insert which has been -ok- with mild steel and fine with aluminium. Chrome ram shaft is 1050 on the inside and its starting to push the friendship with a lathe of this size. I could get the chatter to shut up in softer materials with a higher feed rate, from 0.112 to 0.150mm/rev would usually work nicely. However, with harder metals, its hard to maintain that feedrate and a decent DoC. With these inserts, I was able to achieve something like 0.5mm DoC at best, and it would be boarderline for developing chatter. To be fair though, this would have been amplified due to the long nature of the part and working at the tailstock end, which is nowhere near as rigid as the chuck. For the record and other people's benefit, the ram did have a No.7 centre drill put in each end. I did what plenty of other people have done for years, just grabbed the one centre drill and used it as a do everything item. Its surprising what a difference a larger centre drill hole will make sometimes.

    27591923_1929622737065206_865330707_n.jpg

    This problem got even worse when it came to the static piston seal groove. The static piston seal is there to stop oil passing through the bore of the piston, which is not otherwise effectively sealed with the BFN (big nut). Id planned to cut this groove with a HSS parting tool, but the gods would have none of that. I normally have parting pretty well downpat with my lathe, despite its clapped out nature. This shaft would have none of it. Instant chatter, no matter the tool geometry, speed or which way my tongue was pointed. As above, its more than likely down to the rigidity thats just not available down at the tailstock end. In the end, I ground up a super pointy tool that would cut to the left and plunge in without as much drama. Little by little, I whittled out the groove to spec. The RH shoulder of the groove was still tapered because of the tool, I realigned and did a slight regrind of the tool and that was all fixed.

    Before I did the groove though, I had cut the thread. The BFN specced was an M42 x 3mm, available to you for the princely sum of $90 bucks. Space was getting a bit of a premium down that end of the lathe, the tailstock was already with 20mm of its ass hanging over the end of the bed and if this thread wasnt 3mm pitch, I would have had to be very creative about holding to tool with enough room for the chasing dial to still be in place. Robbing room at the other end was the fixed steady. To aid rigidity, I had the fixed steady in place (with its newly made ball bearing fingers!) right up next to the section to be threaded. The new roller fingers didnt have enough clearance with my fixed stead (a 9in model with adaptor plate) to support the full 70mm ram diameter, so they occupied the area were the groove would be formed later. For the threading process, I cut a landing groove for the tool to stop in at the end of each pass. Im not a fan of winding out the cross slide just in time, especially not on a part thats this burly and expensive. Yes, the neck formed beneath the thread was a weak spot. That weak spot can still support 70 tonnes or so. The pump cant manage that, and even if it could, the cylinder would have given up long before those sorts of pressures were applied.

    27292961_1922677644426382_1773572268_n.jpg

    When cutting a thread this size on a lathe of this size, its best to tackle the problem in stages. I treat the thread a bit like a multistart thread. I complete about half of the required depth as per normal, advancing the compound in to dig deeper. After this, I reposition the tool so that it is cutting a second thread, just ahead of the previous one. Once this second thread catches up to the first, the amount of metal being removed with each pass stays the same, so you can soldier down into deeper depths without demanding more and more of the tool. Once youre at the bottom, one or two very light cuts to merge the two threads together. I got the BFN and used a whiteboard marker to "blue" the inside of the thread a little. When you attempt a fit that is still too snug, the missing whiteboard marker will give you a bit of a hint as to where metal needs to be removed. Thread peaks are usually the problem for me, so some love with a file got a nice radius across the top.

    27583707_1928376743856472_529768891_n.jpg

    Thats all for the ram at this point. We did do some basic features on the other end, just a shoulder and a 20 degree chamfer to allow it to not mash up seals on assembly. We've not reached a decision for how to attach some mandrels on the end of this ram yet, but I suspect itll probably have a M16x2.0 thread tapped in the end of it at some point. For now, it gets a little dip of tectyl to stop it turning back into dirt and stored away.

  4. #4
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    Jul 2012
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    With the ram largely done, I wanted to get stuck into the hardest component of the whole shooting match...

    Gland End Cylinder Cap

    This started as a lump of 1050 hot rolled, 200mm bar. I kinda wish Id got to see the whole bar, she'd be a bit of a monster. It was hard enough lugging 80mm of it around the shed thanks! Work began on it in the milling machine, where I roughed out the bore of the component. This would seem like an odd decision given how many features on the cap need to be completed with the lathe first, but recall that two people are working on this. While the last few features were made on the ram shaft itself, the cap was being readied for its turn on the lathe. Also, 200mm OD is a bit of a stretch for the 4 jaw chuck that comes with the hercus. Its doable, but I wouldnt be betting the house on its holding power. With a 68mm bore ploughed into it with the boring head, I was left with a reasonable face to hold onto for work in the lathe.

    27718776_1929948590365954_667305712_n.jpg

    Also, a tip for young gamers. If you buy the commonly available boring bar set from hafco / ebay / aliexpress, assume that it doesnt come with tips. The "carbide" that it is provided with is, frankly, sh.t. The geometry is all wrong and the metal chips very very readily. Pull them off and braze on trashed tips from the lathe or indexible milling machine cutters, youll actually be able to achieve some work.

    With the lathe cleared, the cap was mounted up in the 4 jaw and external features were machine in. It was at about this time I saw this post HERE, and decided to risk the whopping 14 bucks on a new set of TNMG inserts. This time I went with some 160204 tips...and man, what an improvement that has been. The reduced edge and nose radii has helped my poor little machine to the point where I can get a nicely controlled chip in 1050. With the old tips, you can only hope for long, blue noodles. With the new tips, I was getting perfect chip breakage at 1mm DoC and 0.114mm/rev. Happy days!!!

    27848172_1936320609728752_1929482980_n.jpg

    Keen eyed observers will note the very slight hint of chatter on the cylindrical face behind that o ring groove. Its not actually chatter, its as a result of the motor change that this machine has had. When I first picked up the machine, I had no 3ph to plug into and being a single income at the time, I couldnt justify buying a VFD. A mate had a couple of spare single phase motors kicking around and offered a swap. Naturally, i picked the larger of the options, a 2Kw 1ph whopper. Those of you looking at motor swaps for hercus lathes...this is just too big. The kick it gives on startup is a bit much for pulleys that are located only by grub screws. Over time, im slowly destroying my layshaft, but thatll be a project for another day. The biggest downside, aside from grubscrew slappin' power, is that you get pulses of power. A heavy backplate on my 3 jaw helps mask it somewhat, and youll never notice it on small DoC's, but if youre laying into the ole girl, youll see the surface finish change where the pulses of power come in and leave. I ran my 2um DTI over that face out of interests sake, and the change in height of those "chatter" marks is almost non existant.

    Also, you can see I learned my lesson with regards to parting tools and o ring grooves. Pointy HSS is the go. That photo also shows the two datum faces I used for dialing in the cap for its future moves. This is the cylindrical face that fits into the cylinder tube, and the face is the flange that extends out to allow for mounting of the cylinder to the base plate. The side picture above is the rear of the cap...

    27994805_1938800919480721_1918039354_n.jpg

    ...and thats the front. None of the external features posed any problems. Note that the clamping surface is now the datum face mentioned above, on the outside so that I now had access to finish the bore. I dialed the cap in as best I could, below 0.005mm runout on both datum faces. The bore was then finished out, using my spiffy new bore mic to measure.

    28535333_1962946150399531_108036412_n.jpg

    Yknow how when you use snap guages to measure a bore, theres always the slightest bit of doubt that you maybe didnt get a perfect read on it? Maybe you twisted it a touch? A bore mic removes all doubt. Its super fiddly to work with, yes, but the certainty of the measure is fantastic to have. You can read down to 0.005mm pretty confidently if you have a surface finish good enough to support that. I bored the hole to 70.01 (as pictured) and then used some abrasive paper to get a posh finish, easing it out to 70.03mm. After it cooled down over night, it can come back to 70.02mm. Seriously nice tool!

    So far, this has all been very straight forward. Now its time to start doing the scary bits...

  5. #5
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    Apr 2012
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    nice work scotty,
    when chasing tight or accurate tolerances and i use my bore mic i always measure the bore mic with the mic that i use to measure the bits that are going into the bores, this can iron out some discrepancies between the inside and outside measurements that can sometimes bite you.
    cheers, shed

  6. #6
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    Jul 2012
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    Time to get my groove on!

    There are four grooves to be cut into the bore. From back to front, thats a buffer seal, a guide ring, the main seal and a rod wiper. During the design process, I had a range of sizes to select for all four of those components, but I had to consider the manufacturebility of the grooves with the experience and equipment I had. Given my experiences with the parting tool so far, I considered that any tool profile that looked like that was going to be a no-go for cutting the grooves, so I figured Id be cutting the grooves with a pair of relatively thin and pointy pieces of HSS. All my boring bars up to this point were carbide and grinding them to suit would take an age. Thus, we gave birth to this...

    28536564_1965617633465716_358758029_n.jpg

    18mm shank because the boring bar holder for my lathe swallows that. The rest was 25mm to try and keep some meat on the bone to aid rigidity. I used a 4mm carbide end mill (bought on ebay for a whopping 12 bucks, total trooper of a tool, im buying more) to cut a slot in the end and a flat to allow drilling for the grub screws. Easy peasy, knocked it out after dinner one evening.

    I decided to tackle the hardest one first, the main rod seal. Difficulty of this groove came twofold. One, it was quite deep, and so machining would take a long series of plunging and boring cuts with a relatively thin piece of HSS. This was exacerbated by the second problem...how do you measure the damn thing??!

    20180310_094158 reduced.jpg

    Naturally, I was all excited to bust out the new hotness, the mitu bore mic. That badass would even make a cup of coffee for you, its that cool. My excitement was short lived. The heads of the mic were somewhere over 15mm wide, which is no use when youre measuring a groove thats 12.4mm across. Ok, so perhaps we re-look at the seal specs, maybe we'll get lucky and find a seal that has more favourable dimensions for our measuring gear. SKF did have a seal that was wide enough (in another, slightly less suitable seal design), but it was even deeper again, which made the thickness of the wall between the seal groove and the inlet gallery even more thin. Also the metal surrounding the front side of the seal getting thinner as well was a problem, increasing the risk that the load would push the seal straight out the front of the cap. Bigger seals were out. Some of the other seal types did buy a bit more width without increasing depth, but only by small fractions of a millimetre, not the 2 or 3mm required to make the bore mic applicable. With a tear in my eye, I had to resign myself to the bore mic being no good.

    Ok ok...maybe not THAT bore mic. Ive got a 8x0.5mm tap from when I made a boring head, which would be just the ticket for a home brew job. I mocked up some ideas in solidworks...

    Bore Micrometer.jpg

    And although designing such an animal is harder than youd think, it was doable. I had considered brazing on a pair of ball bearings at each end for a nice, spherical and hard measuring face. While deliberations over measuring methods were underway, my mate went to work and asked a couple of the older fellas how theyve done this in the past. One suggested a pair of spring calipers. Hmmm. I dont own any, but theyre only cheap. I thought the legs were a little short for reaching into a deep groove like the ones in the cap. However, I do have a few spring dividers at work (school) that the kids have trashed. I frankenstined a pair together, then got the oxy out to bend some suitable legs, using the highly technical eyeball method. A bit of grinding and sanding to get the tips to be nice and round, viola!

    20180402_124419 reduced.jpg

    Also in the highly technical solutions dept., take note of my method of lightly locking the thread. Thats blu-tac. I was concerned that once you have the measurement made in the groove, youve got to squeeze the legs in to withdraw it from the bore. When you depress the legs, there is no tension on the nut, which is free to spin as it pleases. The blu-tac was to suppress that, and it seemed to work well. I used the calipers a fair bit as I enlarged the groove diameter and found that once I had a technique downpat, I was able to get predictable measures based on the dials of the machine. Old fella at the engineering shop also suggested that the tolerance of the grooves isnt too tight, other than the bore to rod clearance. The width of the groove was not too important, the seal would simply push back in the groove and seal up anyway. The diameter of the seal is not super picky either, for the same reasons. Obviously, this is within reason, 0.1mm would probably be fine. 1mm would probably not.

    The home brew boring bar worked great. I did make it long enough to reach all the bore's grooves from the one side, but I decided to flip the cap again in the chuck to do the buffer seal and the guide ring grooves from the back, simply for ease of measurement. Before I did that, I did a little graving. I needed a radius on one of the shoulders on the front of the cap, for no reason other than it looks good. I have a little wood lathe style tool rest whipped up for such occasions, and a stick of 1/4in square HSS with a makeshift handle on the back of it. Slowly, caaaarefuling...i whittled a radius onto the cap. I deburred all the edges, internal and external and removed it from the lathe.

  7. #7
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    Quote Originally Posted by shedhappens View Post
    nice work scotty,
    when chasing tight or accurate tolerances and i use my bore mic i always measure the bore mic with the mic that i use to measure the bits that are going into the bores, this can iron out some discrepancies between the inside and outside measurements that can sometimes bite you.
    cheers, shed
    Yep, exactly what I did. Not just so to verify the measurement, but because the bore mic's markings are all weird. Each extension adds a certain amount to it, which means you have to take your shoes off to do the maths. I really used the bore mic to get the decimal places and the regular mic to get the total mm count.

  8. #8
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    Onwards with the cap!

    All turning work was done, so the cap was destined for the mill. A few weeks ago, I posted a thread about doing some cylindrical grinding with a die grinder mounted on the lathe. I used that to restore the pratt burnerd chuck that the hercus arrived with, but thats not what I really wanted it for. The chuck happened to have through face mounting, and I happened to have a 6in rotary table in need of a chuck! Its like it was just made to be! However, I did want to do a small mod to the chuck to improve its useability. I set up the chuck on the rotab and centred it on the body, picked a spot to dig a few holes and dug a few holes. A few M6 screws got a light facing and then some heavy sanding to dome said face, to help stop the screws from scoring up the face of whatever it was I was jacking up. I did drill the holes right out on the periphery because I knew there was plenty of metal there to drill into without accidentally bumping something important, like a scroll plate. I do want to make a set of tiny arms to allow the jacking to take place closer to the centre without having to poke more holes in the chuck's body.

    With the holes tapped in situe, I saw no need to upset the location of the rotary table. Big mistake, which will rear its head later on.

    I mounted the cap onto the chuck, held from the inside and used the jacking screws to dial it in to level. The chuck did need a little nudge to get the cap back on centre, but no big deal. Nothing on the cap was indexed yet, so I just swung the table around to 0 degrees. I swung a dial guage around to centre the x and y axis under the table, then moved out to the centre of the first of 19 holes around the cap. The y axis got locked in place and a travel stop was put in place for the centre of the hole (as it is both the centre of the hole and the slot / counterbore for the SHCS's). Slotting came first.

    20180317_180454 reduced.jpg

    Surprisingly tough to machine, given a 4 flute 15mm end mill. I was expecting a cutter that size to be more rigid and prepared to take abuse than it was. Thankfully, it was only a short slot and so work could progress quick enough. Each pass was 0.25mm DoC and done at 300ish rpm. I was being pretty ginger because I wanted to preserve the end mill as long as possible for future use, especially given that the client paid 70 odd bucks for it. Like a lot of success Ive had with end mills and slotting drills, shallow DoC and faster feed speeds yeilds the best results.

    One became 3...

    20180317_182325 reduced.jpg

    And for the rest of the lap around the block, I measured every 4th slot for depth to make sure the heights were staying on track. Surprisingly, after one correction early on, the HM46 actually proved quite repeatable! I have very little faith in my chinese made casting kit of a milling machine, the table is actually tilted forward a little over 0.1mm...thats another project for another day too, but at least when you know its failings, you can work around them. At least until my surface grinder turns up so that I can level the saddle out a bit.

    Anyway, the whittling continued:

    20180318_113751 reduced.jpg

    the last instance gets skipped because of the fluid inlet gallery. With the slots completed, time to start poking holes through it, starting with a centre drill to spot the holes. If ever I needed some incentive to buy / grind up some spotting drills...

    20180318_114405 reduced.jpg

    ...that'd probably be it. Yknow what they say though, close is clearance!

    20180318_125612 reduced.jpg

    A couple more holes later, she's all done. I am a little over counting 4 turns and 2 degrees. Each hole got a centre drill, a pilot hole of 3mm, then the clearance hole of 9mm, then a touch with a sing flute countersink. Incidently, below is an excel spreadsheet I made up a little while ago. Excel only does decimal degrees out of the box, so that spredsheet contains a macro that converts decimal degree measurements to DMS measures, very useful if your rotary table only does DMS. Enter in the required divisions into the yellow box and itll calculate out each required step on the table. You may need to autofill column three more or less to get one complete revolution. Handy as a pocket in yer undies.

    Degree Conversion Table.xlsm

  9. #9
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    Jul 2012
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    Three features to go on this end cap and she's all done. Of course, two of those are the most high risk of all of the features on the part, the holes for the oil gallery. But first, I have to cut a sizeable slot in the mounting ring.

    Remember how I just slapped on the cap to the rotary table, dialed up 0 degrees and started digging? Whoops. That doesnt affect anything already completed, the holes are all equally and correctly spaced. The problem is that I need to roll the table up on its end to mill this slot, and in doing so, the table's definition of 0 no longer counts. If I had the fore-thought to dial in the base of the table to be parallel to the y axis, id be able to roll the rotary table up onto its base and the 0 degree step would still be correct.

    Bugger.

    Well, first things first, its going to have to be sat up anyway. The back of the table was dialed in so that at least the slot was going to be straight. I decided that the holes were my best bet of being able to realign the rotation of the table back to 0. I stuck a pair of drills into the holes, shank first. Fortunately, Id used a brand new 9mm drill, so the holes were pretty snug.

    29342521_1982093818484764_1721160276461486080_o.jpg29314613_1982093825151430_7036262780063711232_n.jpg

    I swept across the top of the drills and adjusted the rotation until they both showed the same height. I repeated this for a few pairs of holes after I realised that the least resolution would be found in the top pair of holes. I did the widest pair and a couple of others to verify the recalibration and called it good. The table was locked and an end mill fitted, I started digging the slot in the middle (by eye) of the rim.

    As I dug downwards, I needed to figure out how to measure the required depth. A depth mic was no good as the top of the rim was not a dependable location for measuring down from. Looking at the plans, the flat I was plunging down to was only a few millimetres below, 2mm to be exact. I got my dial guage, swept across the top of the 150mm diameter cylindrical face, adjusted the dia to read 3mm. Then, to get the depth correct, the dial would simply have to read 0. Sorted!

    20180321_212355 reduced.jpg

    Which presents the next problem - how do I measure the width and how do I ensure its on centre? Width alone is pretty straight forward, given the required tolerances, vernier calipers will do fine. Where to measure the width to centre is a much more perplexing problem. In the end, I sat a engineers square down on the table of the machine, butted up against the cylinder that extends into the ram tube. Some calculating the distance from the face of the square to the required location of the slot's face and we're set. To measure it, I just used the depth plunger on the verniers. Again, given the use of this slot (clearance for a fitting to be installed), verniers would be fine. It was a slow dig. 0.15mm stepover, 300ish rpm with that 15mm end mill used before. Ten million splintery hairs of 1050 spread from one end of the machine to the other. Bastard of a cleanup job.

    Final operation to be done here was drilling and boring a hole for the 1/2in bsp fitting. The plans show to drill 19mm dia, I ended up going with a 16mm drill to the same depth. Depth is measured to the rim at the bottom of the hole, so by going with a 16mm drill, the centre cone of the drill extends less deep than a 19mm drill. The boring head took care of the rest of the diameter. With that hole bored and no accidental ventilation created through to the nearby gooves, I could breath again!

    But only until the next hole. Last operation on this part!

    29391677_1989178361109643_256377804_o.jpg

    Definitely turning blue on this one. This hole finishes the oil gallery. I drilled a centre drill and a 3mm pilot before stepping up to the final size. I admit, I got a tiny bit chicken here, the plans call for a 13mm hole, but I ended up dropping a mm, just to make sure I wasnt going to break through into the buffer seal groove (which, as per the plans, has a 0.86mm clearance). We all know drills dont necessarily start off real flash like, often leaving an oversized 5 lobed hole. I just wanted to buy a little more space, a little more sanity. More breath holding as drilling happened, until it successfully broke through into the 19mm hole.

    I reached down into the hole with a carbide burr to deburr and slightly port the join between the two holes...and its done. Probably the most complex component ive ever made, and I made it with no mistakes. Hell yeah!

  10. #10
    Join Date
    Jul 2012
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    Griffith NSW
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    Piston

    Compared to the gland end cap, the piston is a walk in the park. It features two shallow grooves for guide rings and one rather deep one in the middle for the piston seal. The key faces for this component are the face that meets up with the shoulder of the ram shaft and the cylinder where the thread for the BFN is. Its important to ensure the guide rings are aligned with these two faces also, otherwise there'll be a twist in the piston relative to the ram rod, or the rod and the piston wont be concentric.

    I did the facing first. Before the top recieved its chamfers, I used the compound slide and a super sharp HSS tool to scribe out all the required grooves. Just so I dont get accused of rounding off all these corners with scribe lines before I even start, I always machined them out in the last few passes. As mentioned before, the width of grooves isnt super important, nowhere near as critical as clearances and somewhat less important than the depth of the groove. I machined the chamfers and moved onto the bore.

    20180325_104651 reduced.jpg

    The boring had to be quite precise, again to avoid extrusion of the piston static seal within. I got it to 50.05 with a very nice surface finish. It got a champfer at 20 degrees and that side was done enough. Some of the bore inside of that was left at 43mm, which is clearance for the M42 thread and of little concern precision wise. With those done, I returned to the outside face and started machining grooves.

    The two guide ring grooves were first simply because they were easy. I used the HSS again to plunge in, get the majority of the profile down to size. I actually shot for a fraction above, with the intent of taking a super fine cut with the parting tool at the end. Yes, not awesome practice to use a parting tool as a longitudinal cutting tool, but we're talking pretty small DoC. I plunged the parting tool in on the tapered end of the groove, then fed across with the barest of cuts being made to bring it to spec. I was aming for 0.05mm clearance with the specificied dimensions so that if there is any errors in concentricity between the gland end cap, the rod and the piston, then there is room to move and not bind everything up. Interestingly, the external clearance of the piston is quite a bit larger than those in the cylinder cap, SKF put the minimum dimension with 0.4mm clearance between the piston and the cylinder. I ended up with less than that, about .25mm total clearance. But hey, if any of it seizes up, i can always take a little off. Very, very very carefully!

    The next step was the large groove for the main piston seal. On a whim, I tried the parting tool. I think it was simply because it was in the toolpost and meh...why not give the cat a swing if youre already holding the tail. It would do short bursts ok, plunge in .1mm and the chatter would start to set it. However, I noticed that if I fed in, then immediately started feeding across, there was zero chatter. Given the narrowness of the groove, it was suprisingly productive and I dug most of the groove in this manner. The tool stickout of the parting blade meant that the walls of the groove were not parallel, so once the depth was achieved, I swapped to the tool that used to live in the home brew boring bar. It needed a little more grinding to achieve the required depth, but it allowed me to reach right down into the corner to face it out.

    Speaking of depth, measurement of the groove was another curly one. In the end, I used a depth mic to find the effective depth of the groove. It was a little fiddly, involving sliding the depth mic back and forth to ensure I was hitting the outer most tangent of the groove, but it worked fine. With the grove completed, I flipped the piston to machine a recess for the BFN and to complete the remaining chamfer. Easy stuff.

    Final step, certainly a satisfying one, was checking the fit onto the ram shaft. Initially it didnt want to play, I established that a bur on the static piston seal groove was holding up proceedings. A little gentle love with a mill file and the piston slid right on like a bought one. The BFN mated up as it was supposed to, and I called another part done.
    Attached Images Attached Images

  11. #11
    Join Date
    Jul 2012
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    Griffith NSW
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    Nothing like typing out a longish post, only to be told that my token had expired...

    Mount Plate

    A slab of a thing, this is. It has a large hole through the middle of it for the cylinder to pass though, plus a little slot cut off the side that allows a right angle fitting and hydraulic hose to pass through. Theres a series of holes around that to hold the cylinder up, via the gland end cap, and a few holes on the outside that where some mounting plates (for some little roller bearings) will live.

    Mount Plate.jpg

    The whole thing is 40mm thick, and there sure as hell isnt any bits of stock around this town where youll be able to slice off a 310 x 350mm slab of it. Naturally, youd be thinking profile cutting. Hell, thats what I thought. Mate's engineering shop has a CNC plasma cutter thatll do 40mm+ plate and mate made the required arrangements. However, he's still a little wet behind the ears sometimes. He didnt think to ask them to rough out the hole though, he just assumed that we'd machine that out.

    Thanks mate.

    20180330_152210 reduced.jpg

    18mm drilled hole started the affair, being the biggest I own at the moment. From there, I managed to open the hole by 1.5mm or so each pass, with varying rpms as the hole enlarged. I made the boring head, and its been a total trooper, Id like to make another smaller one someday for other jobs, but this one has not let me down once yet. The boring bars are the commonly available 18mm shank brazed carbide affairs, available all over ebay, hafco and aliexpress for very little. A warning for new players though, the carbide that ships with these bars is complete garbage. A few of my favourite bars from the set have had a number of new tips brazed on, very easily done with a collection of dead TNMG inserts kicking around. Dont bother with the originals, youre wasting your time.


    One has a lot of time to think about things when youre boring a hole thats 151.5mm across. For example, the thought had crossed my mind that as punishment for leaving me with the worlds most boring job, perhaps Ill send a photo to my mate on messenger after each pass. Or, given the gigantic amount of mess I was making in my shed, maybe id tell him to get his ass over to sweep up the mess. Incidentally, I did wait until the day after the recycling bin got emptied before boring this hole. Worth doing, I half filled the empty large wheelie bin. Missus was not impressed...

    20180331_113128 reduced.jpg

    ...But we got there in the end.

    Oh how Id love to just bust out the trusty 35mm end mill, but I think I left it in my other shorts. I contemplated a few options, perhaps use the boring head to get the radius at the end of the slot done as a hole, then swapping to an end mill to slot out each side of the remaining meat. I ended up going a bit lazier. I had a boring bar in it, it was already on centre...meh, lets just plunge the cut and hack that crap out of there. No problems with the interrupted cut. I eyeballed the radius required with a ruler, shooting for something more like 32 to 30mm so that I had room to open it up with something resembling precision. Once I had a full semi-circular cut going, I used my verniers to measure the effective diameter and opened it out accordingly.

    20180405_174520 reduced.jpg

    And it was at this point, I realised that my mate had made a mistake. I have a recollection of him finding the centre of the slab to drill that initial 18mm hole. Shoulda read the plans champ, that hole was supposed to be a few mm off to the unslotted side. This was so that the resistance to bending would be equally distributed to both ends of the plate. Oh well, I doubt itll be a show stopper.

    And here, gentle reader, I could do with some input from you. While this was going on, I started whittling down a length of ex-antiroll bar. Im intending to make a transfer punch to set a centre for the drilling action to take place on the cylinder tube. It seems pretty damn hard already, and turning it has gotten it awfully hot as I cut it down some. My questions, for those with some experience here, should I bother annealing it first? Will I benefit from hardening it when it is done (ie, go right back up to cherry red and quench, remove any temper that was done at the factory)? Its taking time to cut it down, because after 10 passes at 0.3mm DoC, the part started turning straw coloured...

  12. #12
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    If the transfer punch is only going to be used a few times I would just run with it as is.

  13. #13
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    May 2011
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    Castlemaine
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    Great work Scott.

    Quote Originally Posted by scottyd View Post
    Nothing like typing out a longish post, only to be told that my token had expired... ...
    After suffering the same fate, I now type all long posting in a word document then copy paste.

    Cheers

    Piers

  14. #14
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    Jul 2012
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    Griffith NSW
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    Im thinking what Ill do is place the cap in position and transfer one hole, then mount the cylinder tube up on a rotary table on a drill press, use the punch mark to set the zero position and start rotating from there. The punch will probably survive enough for a handful of hits fine enough, but machining it is super slow. The head that the part is taking on gets out of hand pretty quick. Im thinking im gunna duck out to the shed now, work it for another 10 or 15 minutes and then let it cool until lunchtime :/

  15. #15
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    Jul 2012
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    Griffith NSW
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    Another update to see the end of the mounting plate.

    20180415_102744 reduced.jpg

    This was the end result of the transfer punch mentioned above. Antiroll bars = very nice punches, it has to be said. Hard stuff on tooling when its in its hardened state, though it does machine well enough to be able to control it. Getting the punch from 22mm diameter down to the required 9mm required two corners of an insert. In the end though, ive made it the smallest required size for this project and as required (like for these 6 holes), ill whip up a bush to centre it.

    Incidentally, it was a sunday arvo when I wanted to tap those holes and I only had one M12 tap, which was not as fresh as one would like for a job like this. Id love to whip down to bunnies, the only place left in town thatd come close to providing a tap on a sunday arvo, but alas, they stop at M8. The prices are also eye-watering, but thats what you pay when youre desperate i guess. However, Id recently acquired one of these and figured that I had little to loose in giving it a twiddle on the ole M12 tap. And whaddya know, it actually worked really well. Twisting the tap went from concerningly hard to damn near brand new easy. 10/10, would recommend for a sunday afternoon again.

    20180416_102426 reduced.jpg

    The short sides of the plate are unimportant and theyve been left unfinished at this point, however they might see a file for a little tidying later on. Maybe. The longer sides are the location for some plates that support the hangers, which in turn hold onto a couple of bearings that allow the ram and plate to move side to side. I wanted to skim these faces so theyre presentable and so that I could confidently place the holes. All easily said right? Facing it was no drama, but that head on the mill was getting awfully up there. Then we had to go even higher to allow a drill to clear it...and we're all out of answers. To buy back some Z, the vice was ditched, the hole layout done the ole fashioned way. Drilling was done gingerly with the block held down by my hand. Carefulling...

    20180416_110923 reduced.jpg

    Said holes were tapped and the mounting plate is done.

    Now Id love to be ankle deep in the blind end cylinder cap, because getting it done means the ram can be assembled and taken out of my tiny shed. However, we've hit two snags. One, the piece of barstock that has been sourced is harder than calculus and my lathe was on struggle street trying to machine it. Ive no idea what it is, we've asked for 1050 as with the other cap, but we're not in kansas anymore toto. I took a few cuts at the lowest speed my lathe does, 105rpm and with the lowest feed rate, 0.3mm DoC and all I was getting was bright blue, stringy chips. Forget deeper, chatter central. Forget faster, youll melt the carbide away. Ive got no idea what it is, but its tough tough stuff. I suspect pre-hardened 4140, I cant think of anything else the local mob would have that would behave like this. Now, I could whittle away at it on the lathe and be happy. Itd take forever, but it would get done. My real concern is the mill, for which Ive only got HSS. If its hurting carbide inserts like this, I dont even want to imagine how its going to beat the crap out of some brand new HSS end mills. The disc of tough stuff has been shelved and we're gunna get something else.

    The second problem is seals. When designing the ram, I used SKF catalogues and engineering advice to spec everything out. I picked particular seals based on their size and materials used. Some of it is inconsequential, things like plain O rings are just plain O rings, but some of it has real benefits to picking the right seal for the right application and expected work environment. As such, I developed a list of all the SKF part numbers for all the required seals thinking that we'd go down to the partner in crime's engineering shop, slap the list on the desk and pick up all the required bits. Surely, the largest engineering retailer in town would stock the single largest bearing and seal manufacturers products. SURELY! Nope, turns out they dont...but they'll make a special call just for us and see what they can get. Good stuff, methinks, SKF goodies on their merry way. Nope, they sourced like components from someone else. I dont even recognise the manufacturer, but a quick search reveals theyre fairly generic items. A few of them were close, but not exact matches for size even. Completely unacceptible Im afraid, they were returned. Across the road, a local bearing and seal supplier, has SKF in big ole letters on the building. Sweet, we'll go in there, plonk the list on the table and collect the goods. 'Fraid not. Old mate at the counter gives us some spiel about how some of these might be hard to get, "they might have to machine a few of them up custom". Wut? Someone chime in with some experience here. I got part numbers straight from their cattledog. Hell, a bunch of them are ISO standard sizes. Id have thought a company this size would have them sitting in piles, ready for shipping?!!

    In any event, he's agreed to quote us after attempting to scare the buyer away. If its not insane, we'll go with it. If it is nuts, Im going to start ringing SKF distributors and ask them if Ive lost the plot by designing something with their seals in mind.

    Tis strange, I would have thought that a company would, yknow, WANT my money.

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