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| Thrust bearing modification to mini lathe compond slide. |
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| ian_in_the_midlands:
Since new, I have had problems with the dial sticking on the compound slide. I can not see how the design should work; winding the slide away from the handle relies on contact between the bracket and the dial. The friction will always try to grab the dial. I could never trust the dial so have had to resort to a DRO made from a tyre depth gauge. I wanted to have a go at fixing this with the option of returning to standard if things didn't work out, so I purchased a needle roller bearing, a compound slide feed screw bracket, and dial. The two mounting holes were deepened in the bracket to allow clearance for the screw heads before boring out a recess for the bearing. I did plan to leave a couple thousands of an inch of the bearing proud, but something went wrong as when I tried the bearing for fit, it was flush. :doh: Easily fixed by a small recess around the collar for clearance. Everything assembled, and now slide feels much better. Only .075mm backlash, so wasn't far off depth with the boring. Hopefully the bearing will not suffer from ingress of muck. The gap is tiny so I do not think this will be a problem. |
| Chuck in E. TN:
Ian, can you please post the part #/specs and source of the thrust bearing you used. Chuck |
| ian_in_the_midlands:
I purchased the parts from Arc Euro Trade. http://www.arceurotrade.co.uk/Catalogue/Bearings/Needle-Roller-Thrust-Bearings AXK1226 + AS + AS Needle Roller Thrust Bearings - 12x26x4 AXK1226ASAS £3.84 I have concerns about the modification for 2 reasons: 1. For the price of a £3.84 bearing, why do they not fit them when they build them? 2. Why can I not find details of other people doing this modification? Have I missed something? If it does develop problems, at least parts for the mini lathes are easily available. |
| Manxmodder:
Don't think you have reason to panic Ian,these type of roller thrust or ball thrust cup bearings are common enough in crosslide assemblies. They are fitted to my Harrison L6.......OZ. |
| steampunkpete:
--- Quote ---winding the slide away from the handle relies on contact between the bracket and the dial. --- End quote --- No - The thrust generated by pulling and pushing the slide by turning the handle is countered by the collar on the shaft being contained in a pocket created by the recess in the the back of the bracket. The dials must NOT touch the bracket. If it does, that is why it sticks. It might also stick if a small bit of swarf or grit has got between the dial and bracket. Because the handle turns both ways and both pushes the slide away and pulls it towards the handle, it would need TWO thrust bearings, one to take the thrust in the pull direction, and one in the push direction. If you follow the link in ArcEurotrade's page to the example of how it is done, you will see it calls up TWO needle roller thrust-bearings. By using only one it seems that you have a set up that works in one direction, but in the other works on the same principle as the standard arrangement - but it isn't really clear from your description what you have done. You seem to have machined the dial - is that so? Like other people I have solved the problem of friction and backlash by using a ball-race. Ball-races are not intended to take significant thrust, but for a mini-lathe the forces are low enough not to cause an wear problem. See my post in MadModder showing how it was done on my cross-slide. |
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