Re: [CAD_CAM_EDM_DRO] precision bearing bores
Posted by
Marcus & Eva
on 2002-09-16 19:12:39 UTC
Erik Reikes wrote:
Why don't you just make one?
All it is, is a single knurling wheel mounted on a stubby shaft that can fit
in the boring head.
Buy a straight-cut knurling wheel that's small enough to go into the bore
with as much clearance as possible.
By the way, it is still possible to make an oversized hole with a reamer,
especially in the bigger sizes.
The best way for dead nuts precision is still single point boring, but
boring tools capable of being reliably adjusted to tenths are pretty
expensive.
I have a little boring head that I made once upon a time that uses gauge
blocks for setting.
I can hit a bore size within 0.0002" with it, but only if my boring tools
are set up perfectly.
It gets hard to even measure accurately to tenths with typical home shop
tools.
Most production gaging at this level of precision is done with touch probes
these days.
In the recent past, plug gages were the method of choice, and that's still
the best method for a guy armed with only a lathe and a micrometer.
I usually use a couple of pin gages with a Jo block stack in between because
I'm too lazy to fire up the lathe and turn up a plug gage.
When you're boring a hole to size in the lathe you have some more options.
I believe it was Hoyt who pointed out that you can set the compound slide to
advance a small known amount radially as it is advanced a larger known
amount axially.
This is a pretty good method if the compound slide moves smoothly without
humps or hard spots.
On most "Harbour Fright" class machines though, it does more harm than help
because the compound slide flops around so badly as it moves forward that
you never can tell where the point of the tool is going to go.
Whenever I'm faced with a super precision bore, I try to make it a through
hole if at all possible.
This allows me to lap it to size.
If I need a shoulder, I will cut in a snap ring groove if I can get away
with it.
On cartridge spindles and the like, I bore all the way through, lap to size
and then push in a spacer sleeve and Loctite it in.
I've also ballized bores to size, and that works pretty well too, but you
can't easily get up close to a shoulder.
Hope this helps.
Cheers
Marcus
> I finally went out and bought a proper sized reamer to get the holeHi Erik:
> size exactly right. This cut down on the number of "rigged" bearing
> seats I had to tolerate.
>
> Thanks for the advice. I'll keep my eye out for an internal knurling
> tool. I don't know that I really need one, but it sounds kind of
> neat.
Why don't you just make one?
All it is, is a single knurling wheel mounted on a stubby shaft that can fit
in the boring head.
Buy a straight-cut knurling wheel that's small enough to go into the bore
with as much clearance as possible.
By the way, it is still possible to make an oversized hole with a reamer,
especially in the bigger sizes.
The best way for dead nuts precision is still single point boring, but
boring tools capable of being reliably adjusted to tenths are pretty
expensive.
I have a little boring head that I made once upon a time that uses gauge
blocks for setting.
I can hit a bore size within 0.0002" with it, but only if my boring tools
are set up perfectly.
It gets hard to even measure accurately to tenths with typical home shop
tools.
Most production gaging at this level of precision is done with touch probes
these days.
In the recent past, plug gages were the method of choice, and that's still
the best method for a guy armed with only a lathe and a micrometer.
I usually use a couple of pin gages with a Jo block stack in between because
I'm too lazy to fire up the lathe and turn up a plug gage.
When you're boring a hole to size in the lathe you have some more options.
I believe it was Hoyt who pointed out that you can set the compound slide to
advance a small known amount radially as it is advanced a larger known
amount axially.
This is a pretty good method if the compound slide moves smoothly without
humps or hard spots.
On most "Harbour Fright" class machines though, it does more harm than help
because the compound slide flops around so badly as it moves forward that
you never can tell where the point of the tool is going to go.
Whenever I'm faced with a super precision bore, I try to make it a through
hole if at all possible.
This allows me to lap it to size.
If I need a shoulder, I will cut in a snap ring groove if I can get away
with it.
On cartridge spindles and the like, I bore all the way through, lap to size
and then push in a spacer sleeve and Loctite it in.
I've also ballized bores to size, and that works pretty well too, but you
can't easily get up close to a shoulder.
Hope this helps.
Cheers
Marcus