Restoring damaged toolholder tapers

After regrinding the VN 12 spindle, the thought of placing a slightly marred endmill holder in there is not appealing. I don't want to mess up the fresh taper!

The holders are not real bad, just have some fretting, in some cases so minor it can barely be picked up with a fingernail.

I want to make a lap, that replicates the spindle bore and taper, and use it to do minor cleanup on the endmill holders.


The lap could be soft, like brass, and use an embedding compound like diamond or carborundum, or steel, and use the "timesaver" non embedding compound.

This is a very minor cleanup - I am not going to try to fix badly dented or spun holders.
Your opinions and advice?

Interesting question, I would think just regrinding on a cyl grinder would be better but I am sure that a properly made lap would work just to polish them up. Of course I dont know how to advise what a proper lap for this might be. I hope someone with more experience will contribute. Have a good holiday.

Charles

stoneaxe said:

After regrinding the VN 12 spindle, the thought of placing a slightly marred endmill holder in there is not appealing. I don't want to mess up the fresh taper!

The holders are not real bad, just have some fretting, in some cases so minor it can barely be picked up with a fingernail.

I want to make a lap, that replicates the spindle bore and taper, and use it to do minor cleanup on the endmill holders.


The lap could be soft, like brass, and use an embedding compound like diamond or carborundum, or steel, and use the "timesaver" non embedding compound.

This is a very minor cleanup - I am not going to try to fix badly dented or spun holders.
Your opinions and advice?

Click to expand...

Waste of effort. It's a mill, not an "optical" instrument lathe.

All you really need to do is knock-off any HIGH spots. Usually done "by hand" with a stone.

LOW spots, by definition, will not be in contact, no longer have any impact on your cleaned-up bore.

How critical is it? Not very.

Suppose you got overly aggressive with the stone and created a visible flat spot?

BFD. It is now just one more low spot and harmless.

Is the total contact area reduced? Surely it has been. Not by much, though.

And the OVERALL fit has been improved, so risk of spinning any such "cleaned up" holder in the taper is now lower, not higher.

40-taper, we have the luxury of PLENTY of nice clean new holders cheap enough.

Van Norman? Well.. good mills.

Might have been BETTER mills without the limit of proprietary tooling gone scarce and costly, but they are what they were, not what might have been wished-for.

At least they were good enough mills you can get plenty of sympathy!