Undersize bore hole should be what?

[JWPAGE]

I am new to machining, and learning as I go.

So I have a question. I need to bore a hole in a part, and attach a shaft to it. It will NOT have a set screw holding the part.
So it will be a press fit.

My question is how much smaller should the hole be compared to the shaft?

So if the shaft is .500", what should be the hole? I tried .499, but it's seems to not be enought, as the shaft can turn.

Thanks,
Jim

 

[irishwoodsman]

depending whats going on the shaft you can cut it 3000ths over and try heating the part in the oven thats going to slide on but make sure you got it where you want it befor it cools, this is the way we did races on tractor axels. the races we heated in boiling oil:thinking:

 

[jgedde]

I am new to machining, and learning as I go.

So I have a question. I need to bore a hole in a part, and attach a shaft to it. It will NOT have a set screw holding the part.
So it will be a press fit.

My question is how much smaller should the hole be compared to the shaft?

So if the shaft is .500", what should be the hole? I tried .499, but it's seems to not be enought, as the shaft can turn.

Thanks,
Jim

If the shaft is indeed 0.500 and the hole is really 0.499, you should have ended up with a press fit. I suspect a measurement issue someplace, a tapered bore, etc. Did you ream the hole? Tell us more about your technique so we can make suggestions as to what went wrong. IMHO, making repeatable and reliable press fits can be challenging. When it doesn't work out, Loctite bearing and sleeve lockinig compund does wonders.

What is the application? Perhaps pinning the shaft could be an option.

John

 

[GK1918]

Try to google "engineers edge" site there is a good chart for all the dims. I cant find a way to save it and attach
here. Many good things there.

 

[12bolts]

...So it will be a press fit.

My question is how much smaller should the hole be compared to the shaft?

Welcome Jim, Hi from downunder,
A couple of questions for you first. Does it have to be a press fit? What sort of loading are you putting on the part? Depending on the load, you may need to consider the overall length of the interference fit to resist the part spinning on the shaft.
There are different levels of press fits.
A press fit bearing race may only need .0005-.001" per 1" diameter to meet its requirement, whereas my windmill crankshaft has the conrod connection press fit with a .006 interference fit on a 1" diameter. That required freezing the shaft, heating the boss, and a 40 ton press to assemble.
What material is the part you made with the hole? Does it have a protruding shoulder? You also need to consider if you have enough material outside the hole to resist expansion and maybe losing your interference.
How did you achieve your .499" hole? did you also turn the .500" shaft, and did you also measure that 'hot' after machining or did you let it normalise to room temp?
Pictures are good. Maybe the application, or the parts you made.

Cheers Phil