Shaft and bearing fit question

[nervis1]

How much smaller should a shaft be than the bearing ID for a nice tight fit, no play side to side?

[Mcgyver]

you're asking about fits and clearance and tolerances and we need more info. big thing is what dia. then what's a nice tight fit? is it an interference fit? if its not interference then there's clearance so the question becomes how much clearance is nice?

[mxtras]

The easiest way to get a nice press fit without the pressing is to make the shaft the same diameter as the bearing or maybe .0005" larger and then freeze the shaft and heat the bearing. They will slide right together as long as you are quick about it. This is assuming you are talking about an average bearing, not super-precise or large diameter.

Scott

[nervis1]

Ah. OK this would be for a not yet made, still dreaming in my head spindle for a homemade CNC lathe.

Bearing ID maybe 1", not sure what type yet. If you have ideas I'd love to hear them. I don't think I'll be wanting to heat them with a torch though.

I could freeze the spindle shaft though.

[2muchstuff]

The bearings get heated in an oven. Please don't use a torch.

[nervis1]

See good thing I'm here asking eh?

[2muchstuff]

How big of a spindle are thinking of making.

[nervis1]

1" through hole. I have no idea what kind of bearings yet. Just trying to get an idea what king of tolerance I will need to work to. I have a Jet 1340 gear head lathe and to be honest I don't know if I can hold a tenth on the thing over the length of a 6-8" shaft if that's what I need.

So I'm just trying to get an idea if I can do this or if I have to have it made.

[2muchstuff]

I haven't done any research here but this just a thought, how about using the headstock from the Taig lathe. They claim to hold at least .0005".

[2muchstuff]

I just looked it up and The headstock bearings are 1.5748" OD. and .6682" ID. with a .0004" runout. oooops ....too small.

[mxtras]

NO TORCH, darn it!

Put the shaft in the freezer and the bearings in the oven at maybe 180. This will allow a 7/8" bearing to fit very nicely on a .8758" shaft (.0008" interference).

Ok. If this is for a spindle, you need to do a bit more engineering. You can not mount a higher quality bearing in just any ole fashion. The higher precision bearings require to be fit to a specific size range shaft and bore. Fill in the blanks with the sizes and bearing #s and I think we can fix you up as far as your bore and shaft sizes as well as methods to assemble the bearings without any destruction.

Never use a hammer on a bearing! Thermally shrink fit or use controllable force (like a press). ....sorry - just had to throw that in.

Scott

[Old_Man]

You could heat the bearing in motor or transmision oil, just make sure it`s not shielded or sealed bearings, if this is the case (shielded or sealed bearings) the oven method might heat too much the grease contained and even dry out the bearings.