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  1. #286
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default

    Hi Guys,

    Rather than play about trying to get both ends of the spindle body square to the bore, I'm going to cut another length of bar and start again. But I will also order some of the slightly larger diameter bearings type 6801ZZ and re-machine the bore for the 21 mm diameter of them, which should get the bore square again.

    I would strongly suggest that anybody wanting to make anything where a truly concentric outer diameter and bore was needed, that they check that the work is true at both the chuck and the tailstock end of the work piece.

    I reckon that I got a set of Friday afternoon jaws in my lathe chuck !

    Thanks Guys.
    Best Regards:
    Baron J.

  2. #287
    Join Date
    Apr 2012
    Location
    Healesville
    Posts
    1,757

    Default

    G/day John, to grind 4 jaw chuck jaws I do one jaw at a time, umm....rather than explain it I will try to find and photo the retaining plate that i made to hold each jaw last time i did one.
    For a 3 jaw chuck you can normally file 2 flats on a thick washer to match the gear teeth on the back of the jaws and gently tighten the inner gear teeth on each jaw against the washer, leaving a bit of clearance for the grinding wheel to just get past the end of the jaw.
    Doing it this way the scroll pushes the jaw ways flush with the chuck ways.

  3. #288
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default

    Hi John,

    Thanks for your post.

    Jobs already done and dusted. I posted pictures of how I did it earlier in the thread. The jaws are spot on now.
    Best Regards:
    Baron J.

  4. #289
    Join Date
    Apr 2012
    Location
    Healesville
    Posts
    1,757

    Default

    okey dokey

  5. #290
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Thumbs up Bore Gauge !

    Hi Guys,

    I decided that I needed a bore gauge when turning and boring for the grinding spindle bearings. I was having problems with getting the bore and outside of the original spindle true because of bad four jaw chuck jaws. I've reground those and at least I can get the test bar to clock true, within less than a thou at either end. Putting the already turned and bored spindle housing in the now true four jaw shows just how bad it was originally.

    If I used the outer diameter to true it up I had more than three thou eccentricity, using the bore to do the same showed more than 5 thou. So I've said stuff that and cut a new piece of bar and trued that up. It was just a couple of thou oval, so I've taken a few cuts off the outside to get it truly round. I've taken it out and turned it 180 degrees and put it back in the chuck. Once trued up at the chuck end it barely shows any runout at the tailstock end. Certainly better than I can measure with a 0.01 mm clock.

    Now that I've got it true I'm going to drill it through 12 mm diameter.

    As far as the other, original spindle housing is concerned, I've ordered four new bearings type 6801ZZ. Which are 21 mm diameter and 5 mm thick with the same 12 mm bore. My plan here is to re-bore the spindle to take the slightly larger diameter bearings. To this end I've decided that It would be a good idea to have a plug gauge that I can use to ensure that I get the bore diameter and depth correct.

    I had a scrap end of hexagon brass bar that I have used to make a plug gauge.

    22-06-2020-002.JPG 22-06-2020-001.JPG 22-06-2020-003.JPG

    These are pictures of the gauge. The different diameters are for the 15 mm through bore, the 21 mm bearing diameter and the thread depth and diameter. I made the bearing diameter 2/100 of a mm smaller than 21 mm so that the bearing should be a good push fit into the housing without binding, so if the plug gauge goes in the bearing should without any play.

    Thanks for staying with me on this project !
    Best Regards:
    Baron J.

  6. #291
    Join Date
    Sep 2009
    Location
    Sydney
    Posts
    426

    Default

    BaronJ are you using a cupped diamond wheel for your grinder? I have an old DC motor and controller off my lathe that I’m going to repurpose as a TC Grinder. Not clear on why/when you would opt for flat diamond wheels vs cupped.

    I assume cupped allows for geometry not possible with a flat wheel.

    Also what dimensions and grits are a good starting point?

  7. #292
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default

    Hi Neevo,

    Thanks for your post.

    I have two diamond wheels, one cupped and one flat, both 100 mm in diameter with a 20 mm bore. They seem to only be in 180 grit. I've not found any that are less than that. The suggested speed is 4500 to 5000 rpm. I have cupped one on my four facet drill grinder that runs at 2850 rpm, it works well.

    A cupped wheel allows you to grind flutes on the face of the wheel without the hub interfering, though I see no real reason not to use the flat edge on the periphery of a wheel.

    As far as motors go I've been looking for a suitable motor for a while ! Ideally something in the 50 mm diameter range and about 3000 rpm. I would like to stick with a 240 volt motor, but getting a high enough power rating is difficult.

    I'm in the process of having my third go at making a grinding spindle at the moment. All good fun
    Best Regards:
    Baron J.

  8. #293
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    343

    Default

    Doing a search for info on types and selection of grinding wheels for T&C grinders didn't reduce the confusion for me when I was searching just before I finished my T&C grinder a while back - like most noobs I was looking to be hand fed ie use a cup wheel grade/grit xxxxxxxxx for end mill teeth, use disc wheel grade grit xxxxx for end mill flutes etc. I could not find anything like that. I learnt through experience that a white wheel 60 grit wheel is used for most end mill sharpening, I tried a 120 grit wheel and found that the wheel tended to glaze and needed frequent dressing to remove the glaze, I'm guessing this is because the finer grit does not powder away as easily and tends to clog with small metal particles, it should get worn down slowly to expose new grit surface. As to the shape, I found that with the type of grinder I have a straight disc wheel is not great for doing end mill teeth it is doable but is it also easy to grind away the cutting edges on either side of the one you are working on moreso with small diam. cutters, it may differ with a different design of cutter grinder.
    Diamond wheels are good and cheap and don't need dressing but most warn that diamond is for carbide and not for HSS, I have heard that the diamond particles can dissolve in the steel at grinding temperatures- fact or fiction - I don't know.
    For HSS a CBN wheel is used - finding a reasonably priced CBN wheel was not easy I didn't want to spend a huge amount of $ in case it turned out to be not suitable, I settled on a combination or hybrid CBN/diamond wheel which by all accounts can be used for HSS and carbide. Looking for a suitable diamond or CBN can be confusing as just about all of them come from China and in many cases the seller has no technical knowledge about the wheel at all, and the wheel description is ambigious.
    For gashing between the teeth I mounted a 1mm thick angle grinder cut off wheel, not very high tech but it works.

    The white grit wheel in the pic is good, the angle between grinding face and OD of the wheel is less than 90deg this one is 60 grit and works well but does need dressing from time to time. The other wheel is (allegedly) a hybrid diamond/CBN I've used it a bit - so far no issues - the grinding face and OD of the wheel are 90deg. After use I find many tiny silvery particles not sure if these are the wheel disintergrating or just bits of HSS from the cutter.
    Attached Images Attached Images

  9. #294
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default Threading

    Hi Guys,

    Sorry its taken so long to get back to this TCG project.

    My new carbide threading inserts turned up yesterday, so I been threading the ends of the grinding spindle body. The third one I might add.

    18-07-2020-005.jpg

    I don't what this steel is but it sure isn't EN1

    18-07-2020-001.JPG 18-07-2020-003.JPG 18-07-2020-002.JPG 18-07-2020-004.jpg

    I've threaded the ends 1 mm pitch for a depth of 6 mm. One end is RH thread and the other is LH. If you look at the last picture you can see where the threading tool has just caught the edge of the bore for the bearings, which I've bored out to take the new 6801ZZ ones that I bought from ARC here in the UK.

    I now need to make the caps for each end.

    Thanks Guys.
    Best Regards:
    Baron J.

  10. #295
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    54
    Posts
    1,613

    Default

    Good to see you’re making progress again John.
    Strangely enough I was thinking only yesterday - wondering if you’d done any more and that I hadn’t seen an update for a while!

    Steve

  11. #296
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default

    Hi Steve,

    Thank you for your post. I hope you are well and have got shut of that cold !

    Yes I'd got a bit lax while waiting for the threading inserts to turn up and a bit p****d off with not being able to get the first two spindle bodies trued up.

    Anyway I've started to machine the spindle and just need to finish it off then I can measure up for the bearing spacers. I've made some test ones and I'm confident that I can make ones as needed to the required thickness and length. So I'll be adding some more to this project later. I need to make the end caps as well.

    Just a quick one on motors ! I've been looking at a Chinese 24 volt DC 600 watt motor for the grinding spindle drive. Its only 55 mm diameter, and I do wonder if it would be sufficiently powerful noting that it quotes 20K rpm which is far too fast without gearing down. I could use a variable voltage power supply but 25 amps would make it a hefty one.
    Best Regards:
    Baron J.

  12. #297
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default

    Hi Steve, Guys,

    Quote Originally Posted by BaronJ View Post
    Hi Steve,
    Just a quick one on motors ! I've been looking at a Chinese 24 volt DC 600 watt motor for the grinding spindle drive. Its only 55 mm diameter, and I do wonder if it would be sufficiently powerful noting that it quotes 20K rpm which is far too fast without gearing down. I could use a variable voltage power supply but 25 amps would make it a hefty one.
    I've just discovered that the motor is only 60 watts ! A missing decimal !
    Best Regards:
    Baron J.

  13. #298
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Thumbs up Spindle caps !

    Hi Guys,

    I've got the end caps made and threaded 1 mm both left and right hand ones. I've left the bore on both at 12 mm diameter so I can machine for the spacer collars and the dust seals.

    24-07-2020-001.JPG

    This is a picture of the spindle housing with the left hand end cap in place. The whole spindle is 1" inch in diameter and 6" long. Machined from EN1L steel as are the end caps. They need castellations machining in the edges so they can be tightened.


    24-07-2020-002.jpg 24-07-2020-003.JPG

    Just a couple of pictures of the parts. If you look closely at the last picture, you can see the marks left by the parting tool when a bit of swarf went down the side.

    I'm about to start machining the spindle itself and then I can try a bearing fit and make the spacers.

    Thanks for following along !
    Best Regards:
    Baron J.

  14. #299
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Default Spacers !

    Hi Guys,

    I've started making some spacers to go between the bearings. At the moment these are just experiential in order to see if I can get the bore and outside diameters correct, also the length. I the past I've found thin wall tube difficult to machine, particularly parting off to length.

    25-07-20-003.jpg

    Here I've turned 5/8" diameter EN1 bar down to 13 mm, and I'm drilling a 10 mm hole up the middle using a 10 mm centre cutting milling cutter. I started the hole with a centre drill and opened it out to allow the cutter to enter. I've gone in 30 mm, roughly to where the shoulder is.

    After drilling I used a miniature boring bar and a plug gauge to accurately get a 12 mm bore.


    25-07-20-002.JPG

    I also had a play with making a 10 thou thick wall sleeve just to see if I could. The other one is a 1 mm thick wall. I actually made several.




    25-07-20-001.JPG

    These are two of the spacers that I cut to length. I made the 10 mm one first and then the thin 10 thou one. I actually used the Dremal and a cut off disk to get it to size.

    The technique I used is very simple. I put it on a mandrel in the lathe three jaw chuck up against a shoulder, and then used the calibrated leadscrew hand wheel on the lathe to set the length, and rotated the spacer on the mandrel by hand.

    The technique works very well but you do need a glove because the sleeve gets a bit warm and if you let it go, it spins and walks into the cutting disk. Either shattering the disc or marking the work. You have to get the cutting disc dead square to the work to prevent this happening.

    I'm going to make a wooden clamp, clothes peg style, to grip the spacer for the next lot I make. Better than toasted fingers.

    That is all for now ! Thanks for looking guys.
    Best Regards:
    Baron J.

  15. #300
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    4,774

    Thumbs up Spindle Machining !

    Hi Guys,

    After spending most of yesterday making a new set of soft jaws for the lathe chuck so that I could accurately machine the grinding spindle for the Brooks TCG, I finally got it almost done ! I say almost, but I'll explain later.

    28-07-2020-009.jpg

    First up a family picture of the parts so far. The spindle at the top of the picture, then the two 15 mm spacers that go between the bearings, then the centre spacer this is the one that keeps every thing apart, then the bearings themselves.

    28-07-2020-007.jpg 28-07-2020-008.jpg

    These pictures show the assembly of the bearings on the spindle as they will be when inside the housing. I hadn't noticed until just now, the "Ford" logo stamped into the centre spacer. I have absolutely no idea what or where this piece of bar came from, but since it was the right size, I just cleaned up the end and drilled it out and bored it 1/2" to go over the 1/2" bar that I used for the spindle.

    Now I said in the first paragraph that I had almost got this done !

    The problem is this "how do I measure and by how much do I need to reduce the spacer length to set the bearing separation" ? There is a shoulder at each end inside the housing that limits how far the inside bearings can go. Currently guessing, I have about 1 millimetre of end play. I don't want to pre-load the bearings excessively, but at the same time I don't want any end float if I can help it, at least any that I can measure.

    Right that all for now folks. Thanks for bearing with me so far.
    Best Regards:
    Baron J.

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