marshg246
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I haven't had problems with that but can easily see it happening if someone beats the bearing out of the shell - heat is required!
Sleeve gear installation problem
- Thread starter mdt-son
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marshg246
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1) Bearing races are very hard and would be difficult to sand
2) Residue from sanding could get in the bearing
3) It would be much harder to do evenly.
I asked because it has been my go-to for similar issues outside of motorcycle repair.
I did just this the other day on a sacrificial layshaft bearing taken from an Ebay gearbox. The bearing was trash anyway so nothing to lose there. Whoever installed this bearing into the gearcase got a little carried away with whatever 'bearing set' product they used. As the bearing was put into the gearcase the fluid piled up behind it and some ran into the bearing.
The layshaft was a tight fit into this bearing, would need to drive it into the bearing. I wanted a tight fit but didn't want to need to drive it in by force.
My usual approach is to use a battery powered hand drill, select a suitably sized drill bit (or other similar cylindrical item) then wind a strip of scotchbrite pad tightly around the bit using enough scotchbrite to make a snug fit inside whatever I am sanding/polishing. I cut strips maybe 3 times the depth of the bore I am working on. In cases where I need to do more than just clean the bore I follow up the scothbrite wrap with a strip of silicon dioxide wetordry. I use enough to make say 3 or 4 wraps of each, scotchbrite and sandpaper.
I end up with a DIY hone of sorts.
I probably ran either 320, 600 or 1200 grit for this layshaft bearing and got what I was after. It now can be fitted to the layshaft with strong hand force.
I think my method sort of sidesteps your reasons #1 and #3 but #2 still stands for sure.
marshg246
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Most today use a roller bearing for the layshaft, not a ball bearing. I heat the layshaft inner bearing race and drop it on the layshaft. You don't want it coming loose from the layshaft. To put the outer race in the shall, you heat the shell and drop it in. There no reason to sand anything related to the layshaft bearing unless you're using a ball bearing which I do not recommend.
See: https://andover-norton.co.uk/en/shop-details-2/17267/layshaft-roller-bearing-18337-b2-322-
I spoke of the layshaft only as an example case because I had just done it. And this particular case was not destined for an actual gearbox, just me playing around.
Given all the couragement here, and with the help of a good friend, we clamped the gear wheel in the chuck of his lathe and spent 1+ hour using grade 800 wet (actually de-sharpened grade 400) which resulted in the axle coming down from 31.750 mm to 31.730 mm.
It was a complete success! Mated with a new bearing (also supplied by AN), the sleeve gear could be pushed fully home by applying some gentle knocks, so a transitional fit was achieved, which us perfect.
By the way, I measured a genuine used sleeve gear off a Commando gearbox. The OD was 31.720 mm. Given the possibility of wear and a different bearing ID tolerance, I put my target dimension a little higher.
According to guru John Hudson, the correct fit is a tight clearance fit, allowing the sleeve gear to be pushed out by hand.
I wouldn't have dared using 180 grit, but we might have started with grade 400 dry. Given the cost of a new sleeve gear, I prefer to take it easy and measure often.
One lesson learnt is that the hardened steel surface wears out an emery cloth quickly, even when grinding wet. I think we used 5 strips before reaching the desired dimension.
Thanks to all for your views !
- Knut
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I will definitely send my remarks to AN. Bearing and shaft need to fit right out of the box. If someone tried to force these parts together using a press, the bearing is likely to jam, and the inner race may develop cracks due to circumferential stresses (radial stresses also create circumferential stresses).
- Knut
Prior to grinding, bearing seat of the shaft didn't enter at all, so the "not fully home" remark was somewhat inaccurate.
There is a shoulder at the sleeve gear which needs to mate with the inner ring of the bearing. The clearance btw. gear face and face of the outer race should be in the order of 0.5mm . I measure about 0.7mm now, and will try to push the sleeve gear a little further in. Maybe faces of the inner and outer bearing races are not perfectly in one plane. Your picture suggest this may be so.
- Knut
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