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Mpc repair - how round can you get it?
Posted: Mon Jan 22, 2024 4:33 pm
by Bach5G
I received a mpc today - used - and the shank is an little out of round.
How much can you get back into round?
Re: Mpc repair - how round can you get it?
Posted: Mon Jan 22, 2024 4:47 pm
by Burgerbob
Totally depends. Sometimes you can't tell, sometimes it's never right again.
Re: Mpc repair - how round can you get it?
Posted: Mon Jan 22, 2024 5:04 pm
by ithinknot
You can get it pretty close to perfect, but not with just "the tool". The collars that Instrument Innovations sell are a good way for the band director to avoid overshooting and flaring the end, but if you're trying harder it's more a case of using loose mandrels and working the high spots from the outside.
If the backbore ends with a single taper, with a flat edge to the shank end, then you can usually get it very very close. It's harder to camouflage the exterior damage when there's an extra chamfer/countersink at the backbore exit.
The original damage is almost always repairable... other people's repair attempts, less so.
Re: Mpc repair - how round can you get it?
Posted: Mon Jan 22, 2024 5:31 pm
by ghmerrill
^^^
This.
You have to remember that it's not a true cylinder you're dealing with. That makes it harder. And the chamfer/countersink issue may be ultimately insurmountable -- even with a lot more equipment than you're unlikely to see outside a real machine shop. Even then, ...

I have one where I've decided "close enough is good enough".