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  1. #76
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    35
    Posts
    1,522

    Default

    Hi Baron. I think you should just scrape the main surfaces of those plates, if you make a simple pull scraper you can just use a broken center drill or any old HSS. Probably only 2 - 3 hours of work as a beginner.

  2. #77
    Join Date
    Mar 2011
    Location
    Dural NSW
    Age
    82
    Posts
    1,203

    Default Scraping

    Quote Originally Posted by caskwarrior View Post
    Hi Baron. I think you should just scrape the main surfaces of those plates, if you make a simple pull scraper you can just use a broken center drill or any old HSS. Probably only 2 - 3 hours of work as a beginner.
    Yes agreed, I would hand scrape, it would rectify the problem.
    Bruce

  3. #78
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Hi Michael,

    Thank you for your reply.

    Quote Originally Posted by Michael G View Post
    Personally, I'd be looking for some small thrust bearings.They are not terribly expensive and certainly a lot more compact - most lathe compounds that I have taken apart seem to be done this way.
    I hadn't thought of those ! I have a very large collection of bearings, but non of them are thrust types. I do know that Arc Euro stock them for the Myford compound screw modification. I will have a word with them.

    I just happen to have a M8 LH tap here, bought for a repair many years ago. I also have some acetal, so if you can provide a sketch of the nut you want, I could whip something up for you, or even just tap a block that you could then finish machine.

    Michael
    Thank you ! That is very kind of you, however if you don't mind I'll see how I get on moulding a nut. If that fails, if its allright with you I'll contact you.

    As far as the nut is concerned I was just going to press fit the acetal into a recess in the saddle. The last nut that I made this way can be seen in the pictures of the hight gauge that I made. Absolutely zero backlash. I don't know what the wear characteristics are like but that one gets little use.

    I know a couple of guys locally that have made replacement mill table drive nuts this way and speak highly of them.
    Best Regards:
    Baron J.

  4. #79
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Hi Phil,

    Thanks for your reply.

    Quote Originally Posted by Steamwhisperer View Post
    I agree John, it would be very nice though you could hand scrape them and I think if you used a lump of wood as a surface plate they would still end up better than what they are.

    Phil
    That is exactly what I'm doing at the moment ! I am using a light oil on the emery paper to reduce clogging. I could do with something more coarse than 600 grit paper though. Its just time consuming and tiring work. I do have a Sanvik carbide scraper that I was given some time ago, but I've never used it.
    Best Regards:
    Baron J.

  5. #80
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Hi Ralph,

    Quote Originally Posted by caskwarrior View Post
    Hi Baron. I think you should just scrape the main surfaces of those plates, if you make a simple pull scraper you can just use a broken center drill or any old HSS. Probably only 2 - 3 hours of work as a beginner.
    Beginner is right ! I have a Sanvik carbide scraper that I was given, I've yet to even try scraping with it.
    Best Regards:
    Baron J.

  6. #81
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Scraping !

    Hi Guys, thank you all for your words of support, its appreciated.

    The consensus seems to be to scrape the bearing support plates flat ! Well there has to be a first time for everything, so I'll have a go.
    Best Regards:
    Baron J.

  7. #82
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Left Hand Nut !

    Hi Guys,

    In between rubbing the bearing mounting plates on 600 grit emery paper, to get them flat, I decided that it was time to make a start on the moulded acetal nut for the leadscrew to run in.

    20-06-2019-002.JPG
    I had been given a couple of inches of black acetal plastic bar. I originally thought that it was 20 mm diameter but it turned out to be 16 mm. Not a problem since the leadscrew is LH M8 X 1.25 pitch. The first job was to cut it in half length ways. I sawed it in half on the vertical band saw using a "V" block stood on end and the bar held into the "V" with my fingers. It cut very quickly indeed, so you need to be careful.

    23-06-2019-003.JPG
    I was initially just going to drill a 7.5 mm hole right through, then realised that I needed to split it first, otherwise my nice round hole would become an oval one.

    23-06-2019-005.jpg
    I have a nice Jones and Shipman boring bar that I think I've only used a couple of times, so I decided to use it. Anyway I set it up to the correct centre hight and then bored out the aluminium bar to 16 mm diameter.

    23-06-2019-001.JPG 23-06-2019-002.jpg
    Having now cut the acetal bar in two, I made a collet from a piece of round aluminium bar, drilling it through with a 12 mm drill, and also so I could fit the boring bar into the hole without it fouling. Also so that I could cut through one edge and then make two other cuts at 120 degrees, so that it would close up more easily in the lathe three jaw chuck. I made the saw cuts using the same method that I used when cutting the acetal rod. Again great care is needed because the saw tries to drag the aluminium tube over when making the first cut. It didn't do that with the plastic.

    23-06-2019-004.JPG
    I actually left the packing in the collet slot because the acetal bar was a very good fit in the bore. I pushed it completely home with the lathe tail stock ram with the tailstock chuck wound fully closed.

    23-06-2019-006.jpg
    Now I simply drilled a 7 mm diameter hole right through.

    23-06-2019-007.jpg 23-06-2019-008.JPG
    These pictures are of the finished collet and the acetal bar drilled out ready for moulding round the M8 LH threaded rod. Surprisingly when taken out of the lathe chuck the acetal just pushed out under finger pressure. I expected to have to press it out. The red ink mark is where the lathe chuck jaw number one sits. So if I have to make another nut it will be accurately centred.

    I will deal with actually moulding the nut in another post.

    Thanks for looking. Your support is appreciated.
    Best Regards:
    Baron J.

  8. #83
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Moulding a LH nut !

    Hi Guys,

    As promised this post deals with moulding and making a suitable acetal nut for the leadscrew.

    IMG_0374.JPG IMG_0375.JPG
    The first thing to do, is to file a pair of spanner flats on one end of the threaded rod. This is needed in order to remove the threaded bar from the moulded on nut. It is important to use some kind of lubricant on the rod. Light oil or grease works. I use "Ambersil" which is a Teflon loaded oil as an anti stick agent. If you do use this be very sparing with it, because if it gets onto the joint faces of the acetal they will not fuse together properly, if at all.

    IMG_0376.JPG
    I next clamp the whole thing in the vise and apply some pressure. The acetal will deform slightly around the threaded rod. Again its important that the acetal fits evenly and that the cut edges are not yet in contact. Ideally both flat surfaces should come together at the same time.

    One experiment that I would like to try sometime is just to just slit one side of the tube and force the threaded rod into the hole in the acetal. Since as the plastic melts it fills any gaps it might work to give a better nut. Indeed there may even be a better plastic material to use that would be more suitable for this purpose.

    IMG_0377.JPG
    I use a butane plumbing torch to heat the rod, I also have a small cooks torch. You can just see it in the background. I used the large one to heat the threaded rod from the long side and the cooks torch to heat the small spanner flats end. It takes a good ten minutes to get the threaded rod hot enough to start to melt the plastic, At this point start to tighten the vise and the edges will meet up and fuse together. The acetal will become slightly oval as well. Now turn off the heat and allow to cool, do not quench at this time. The acetal will shrink as it hardens. Quenching might crack the joint, particularly if any oil or what ever release agent you have used has got between the faces.

    IMG_0379.JPG IMG_0378.JPG
    Before removing the now cold acetal nut, i made it round again in the lathe.

    IMG_0381.JPG IMG_0382.JPG IMG_0380.jpg
    These are pictures of the ends of the nut after removing it from the threaded rod. Not particularly pretty but it still remains to turn it down to size and cut it to length. This piece is 50 mm long and I expect to use about half that length.

    You will find that it is quite stiff to turn on the threaded rod, with absolutely no play or backlash. A spot of light oil helps to ease its movement.

    This is now the third one that I've made and I'm quite happy with this one.

    Thanks for looking.
    Best Regards:
    Baron J.

  9. #84
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    574

    Default

    This is something I hadn't though of, theoretically you should have a perfect nut with zero backlash.

  10. #85
    Join Date
    Nov 2010
    Location
    Gippsland Victoria
    Posts
    733

    Default

    Quote Originally Posted by familyguy View Post
    This is something I hadn't though of, theoretically you should have a perfect nut with zero backlash.
    You can deliberately create a tiny amount of backlash with a piece of plumbers teflon tape wrapped around the thread, this creates a small gap between threaded bar and plastic. Some folk have also used alfoil.

    First time I tried this idea the zero backlash made a very very tight fit and was difficult to turn. 2nd try was better with some deliberate backlash.

    Another way is to cut longitudinal slots in a piece of threaded bar and then use it as a pseudo tap to scrape a tiny bit off the moulded plastic thread.


    Oh yes, .............. thanks for this build thread BaronJ its has been interesting.


    Bil

  11. #86
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Hi Bill,

    Thankyou for your comments.

    thanks for this build thread BaronJ its has been interesting.
    I'm glad the thread is of interest to you ! At the moment I'm dealing with getting the X - Y table part sorted out. The moulded plastic nut is only one part of it.

    I've not tried the teflon tape trick to create a little clearance in the thread. Though I did try the aluminium foil at one time and it wasn't a good result. The foil broke up and stuck to the Acetal causing severe binding. As it happened that was a normal thread and it took a HSS tap to clean it out. Afterwards the thread was as sloppy as if it had just been tapped in the first place. A drop of Teflon based oil, ie Ambersil makes quite a difference.
    Best Regards:
    Baron J.

  12. #87
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Drilling Saddle.

    Hi Guys,

    I've spent some time today setting up the Fobco Star drill press in order to drill a straight 8 mm hole all the way through the width of the saddle plate. And then drilling a 14 mm by 15 mm deep recess in the back of the saddle plate in order for the plastic nut to be inserted and retained.

    26-06-2019-003.jpg
    This is the setup.

    I used a very very old, at least 60 or 70 years, "Criterion" brand, locally made angle plate from the now long defunct "Lightowler" Ferrybridge, foundry that was dug up and recovered from the land where the machine shop used to be.

    Its bolted down to the X - Y table and squared up with the saddle plate clamped to the front face. Knowing that everything would be now be dead square, I piloted the hole and drilled as deep as I could with a small 4 mm drill, then when I couldn't drill any deeper with that one I changed to a longer 6.5 mm drill then used the 8 mm drill to finish off.

    26-06-2019-004.jpg
    This is the 6.5 mm drill. Note that its firmly clamped to the angle plate with the "Kant" style clamps that I made some time ago.

    26-06-2019-005.jpg
    And now the 8 mm one. Actually I used this particular drill because I know that it produces a hole 8.1 mm in diameter and allows clearance for the M8 threaded rod.

    26-06-2019-010.jpg
    Afterwards I turned the saddle block upside down and used a 14 mm drill to make a 15 mm deep recess in order to fit the plastic nut.

    26-06-2019-011.jpg 26-06-2019-012.jpg
    You can see here into the recess that was made.
    26-06-2019-014.jpg 26-06-2019-013.jpg 26-06-2019-015.jpg
    This is a test assembly with the LH threaded rod passed through from the front and out the back.
    You may notice that the threaded rod has had a centre drilled into it. This was done so that the tailstock on the lathe could be used to support it whilst turning the plastic nut down to size.

    26-06-2019-007.jpg 26-06-2019-008.JPG 26-06-2019-009.jpg
    This was the setup on the lathe. The threaded rod is held in a collet and the remote end supported by a live centre. Then the nut trued up, measured and turned down to fit. It is sufficiently tight on the threaded rod that it could be turned without any danger of it moving. When I've got it fully assembled I will apply a little lubrication to the threads.

    Thanks for looking ! Your comments are appreciated.
    Best Regards:
    Baron J.

  13. #88
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Leadscrew nut finished.

    Hi Guys,

    Just an update on what I've been doing today.

    27-06-2019-002.jpg
    I've got the plastic leadscrew nut finished and securely pressed into the recess at the back of the saddle plate.

    One of the critical things was to ensure that the nut was not only securely held but also as truly centred as possible. In order to do this I turned the nut so that it was round but at the same time centred properly. See previous pictures.

    Unfortunately it wasn't quite as secure as it need to be when pressed into the saddle plate hole, the friction from the lead screw caused it to start to spin. Could have done with taking off a couple of thou or so less than I did.

    In order to solve this problem I turned another mm off diameter of the acetal nut and since I had a length of 15 mm diameter brass tube, I bored a piece to suit the new diameter of the acetal plastic nut. I then after turning the 2 mm wall brass tube to be a tight press fit on the acetal plastic, I also used a dab of super glue to lock it in place. Then skimmed the outer diameter of brass tube to be a tight press fit into the hole in the saddle at the same time I machined it to a length of 15 mm to suit the hole depth. This nut is perfectly centred and is not going anywhere.

    27-06-2019-001.jpg
    This picture shows the nut in place in the rear of the saddle plate

    27-06-2019-003.JPG 27-06-2019-005.jpg 27-06-2019-004.jpg
    No pictures of me scraping or rubbing these bearing side plates, supporting the top slide. Needless to say that top plate will move under its own weight now. From end to end with only a light finger push, where as before it was quite tight and took some effort to move it.

    The leadscrew is in the place it will be when the saddle is fitted to the base plate.

    The next job is to machine the front plate and leadscrew for the bearings that are to be fitted. I'm still working on fitting the saddle to the baseplate. At the moment I have 1/2 thou of play or twist in the saddle which is going to have to be removed.

    More news later.
    Thanks for looking. Your comments are appreciated.
    Best Regards:
    Baron J.

  14. #89
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Machining the Leadscrew.

    Hi Guys,

    In between scraping the bearing support plates and the sides of the saddle plate to remove a now almost imperceptible play between the saddle and base plate, I've machined the leadscrew at one end to fit the bearing in the front plate and bored the pocket for the bearing to sit in.

    29-06-2019001.JPG
    I used the same setup on the lathe as I did for turning the plastic nut round and to size.
    Notice that The lathe tool is a left hand tool mounted on the right hand side of the tool holder. I couldn't quite get right up to the end of the threaded rod because of the live centre cone, but it doesn't matter since I just parted that unmachined 6 mm off the end.

    29-06-2019004.jpg 29-06-2019002.jpg 29-06-2019003.JPG
    The bearing bore is 1/4" inch (0.250 thou) diameter, so I had about 60 thou to take off the diameter. The bearing is a good fit on the turned section. I was quite surprised that I could still see and feel the minute patterning where the threads had been rolled into the bar. A quick rub with some 600 grit emery allowed the bearing to slide on with a gentle push and without binding anywhere.

    Sorry about the focus in that last picture. I was trying to get a good picture of the patterning, but couldn't get the camera to focus properly on it. The camera is supposed to be able to focus down to half an inch.

    Thanks for looking. Your support is appreciated.
    Best Regards:
    Baron J.

  15. #90
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Thumbs up Leadscrew machined and fitted.

    Hi Guys,

    I'm starting to get a complex over scraping ! I've got the top slide moving beautifully ! Its smooth, no sticking anywhere and no measurable play or twist. But it is hard work and requires lots of concentration, so I've decided to give it a rest for a while and get on with doing other things. Like the leadscrew for instance.

    02-07-2019-001.jpg 02-07-2019-002.jpg
    In the previous post I mentioned that I had counter bored a recess for the 5/8" inch diameter bearing and machined the leadscrew at one end to suit the 1/4" diameter bore of the bearing. To make the pocket, I basically just plunged a 5/8" inch four flute end mill into the back of the front plate 7 mm deep, after centring it on the existing 4 mm hole. The pocket ended up exactly the right size but about 10 thou higher up than intended. Fortunately it doesn’t matter much, other than I had to open the original 4 mm hole out to 7 mm to clear the end of the leadscrew instead of the 1/4" diameter that I intended .

    02-07-2019-013.jpg 02-07-2019-015.JPG
    These two pictures are of the front end of the leadscrew passing through the bearing and through the front plate. Its difficult to see at this angle but the leadscrew is slightly high in the hole.

    02-07-2019-004.jpg 02-07-2019-006.jpg02-07-2019-005.jpg
    These three pictures are from a test assembly to make sure that the back end of the leadscrew went into the back plate without fouling the edges of the hole. The middle picture also shows a mistake I made putting the bearing support plate in the vise upside down so there are two 8 mm holes in that one. At least when in use it wont be seen since its at the back. At some point I will put a plug in that hole to keep any grit out.

    02-07-2019-007.jpg 02-07-2019-003.JPG 02-07-2019-012.JPG
    These next three pictures show the back of the grinder base. You can see a grub screw sticking out. There is actually a second grub screw in that hole. It is threaded M8 right hand 1.25 mm pitch. The grub screws were made from the offcuts of the M8 CSK screws that I shortened for the front plate.

    02-07-2019-009.jpg 02-07-2019-008.JPG 02-07-2019-010.JPG
    These are the parts that are in that hole. I put a centre in the end of the leadscrew so I could support it with a live centre in the lathe. Well it occurred to me that if I put a grub screw in there and trapped a hardened steel ball bearing in between the end of the leadscrew and grub screw, I could apply a slight preload and take any play out of the movement of the saddle.

    Actually it seems to have worked out very well. The leadscrew is securely held and turns very smoothly without any hint of backlash. Not only that but the leadscrew is level within a couple of thou to the base plate at either end. As the pictures below show.

    There is the merest hint of a bend about a third of the way along its length. I measured between 5 and 7 thou. I'll have to give the threads a quick rub with some emery paper to get rid of the slight roughness on the peaks of the thread. Either way I'm not going to complain about a few thou.

    02-07-2019-014.jpg 02-07-2019-011.jpg
    One issue I did find was that as I tightened the backing grub screw it also caused the one inside to tighten as well. I may just replace both grub screws with a short stud and lock nut. I'll have to play with that later.

    In the meantime I'm trying to get the saddle to run smoothly from back to front without sticking in a couple of places. I did find that one of the bearing support pins had loosened. I tightened it back up and checked all the others. I could loctite it in place, but I don't want to do that at this point. The top slide is brilliant.

    That's all for now folks... Back to a little scraping
    Thanks for looking.
    Best Regards:
    Baron J.

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