Proper set screws will bite into the shaft and lock it in place tight enough for general use on a wood lathe, yes if there are two threaded holes use two screws. A sharp drill will cut the wood so it should not move the shaft. It is not a bullet proof system but adequate.
My local Home Depot has bins of fasteners which includes Allen set screws so you may may be able to get them locally.
I checked online and found some RSV (stainless steel) ones for 0.20 EUR but shipping was 15 EUR on them. So I stopped at the local DIY store and picked up some 0.10 EUR set screws but the shortest were 45mm which is too long since it they would touch the bearing casing bolts.
You will notice a groove in the shaft for a snap ring. Once you replace this ring...tap the end of the threaded shaft (protect the threads with a wood block) until the ring contacts the bearing, then add the set screws to lock the shaft in place. Align the pulley last and lock in place with set screws.
I fail to locate the groove. If there should be a snap ring it's missing.
The only groove that i can see/feel is right behind the thread.
But placing a snap ring here and tapping until the ring touches the collar of the bearing would locate the shaft in such a way that the grub/set aren't in full contact with the shaft. Since there is a stepdown
Bearing held in place by hand to illustrate set/screw not fitting:
Full shaft to illustrate stepdown
Another option would be that there should be a snap ring on the first shoulder after the thread, which would make more sense. But there is no groove there..
Could you point out where the snap ring should be?
You may also want to clean the rust off of the shaft.
Thank you for the comments I'll take your advise into account when proceeding.
What happend meanwhile...
I wanted to clean the rust on the shaft so it could easily move when not tightened down (as shown in the bearing video posted by FrankC.
Since I couldn't access the shaft properly I decided to take it out to give it a proper cleaning. Whilst doing that I noticed that there is some play in the bearings. Meanwhile (see above) I was having trouble getting the right length set screws.
I could probably get away with the amount of play in the bearing. Since they are self centring bearings some play is normal.
I decided that since I have everything open now I'll replace the bearings while I'm at it. I found the identical sized bearings at SKF (which is known around here for good quality bearings):
Doing so I don't have to worry about the right grub/set screws since they come with the bearing (i hope).
The only potential issue I see right now is that the bearings assume a h6 tolerance shaft, which gives me -0 -13 micrometers of tolerance on the shaft. I'm worried that the rust has damaged the shaft too much.
The bearings aren't that expensive (+- 35 EUR for a set) and I got the lathe for cheap (50 EUR). So I'll just go for it, keeping in mind that I only want to touch up this lathe for get some practical experience to decide on an upgrade later on.
I was checking to get a new spindle shaft (if needed) but couldn't find one (in a fast google search) that has the right dimensions. The advantage would be that I can get one with a more standard thread of M33 X 2.5 (europe standard) instead of the not so common 3/4 inch 10 TPI thread that is on my current one. Allowing me to get accessoires more easily. Right now i'll stick with an adapter so I can mount M33 accessoires so I can keep then once I upgrade.
Anyway next steps will be:
- Clean up the shaft, being careful not to rough it up to much where the bearings should sit.
- Replace the bearings
- Put the shaft in place with a snap ring? If I can locate the right position to put it...
- Lock in place with the set screws
- Fix/replace the pulley (since I noticed some play there also, motor pulley seems fine)