Cutting down height of Al cased plastic knobs - neatly?

Your lathe needs collets instead of a chuck.

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Unfortunately that would require a complete range of sizes, for future eventualities.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Yes. Collectively, those accessory items are called "tooling." Machine tools without tooling are useless. But, assuming your lathe is equipped to use collets, you can buy them one at a time as the need arises.

"N_Cook" wrote in news:guemd9$1pv$ snipped-for-privacy@news.motzarella.org:

you need some sort of expanding internal shaft to hold the knob from the inside. Lathes do have chucks designed to do that(hold from the inside),but not for the small diameters of a knob's shaft.

I'm thinking of a hollow shaft with the end cross-slotted and a coaxial screw that pulls in a cone to expand the slotted end,which gets inserted into the knob's bore.

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Why not just take the knobs off and put in a separate bag when shipping in the container????

And again, you're describing a collet, this time an internal collet.

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Replacing Jubilee clip screw with a grub screw, no goer, all threads are too fine and needs a bearing surfce flange. But cutting the bolt-head off the existing one, leaving the flange and cutting some off the other end and cutting a slot across for turning with a screwdriver. Cut off the retaining tang parts of the clip to shorten (no longer holds the bolt in place) should work down to about 12mm diameter knob , holding securely in a standard 3-jaw

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Why not just take the knobs off and put in a separate bag when shipping in the container????

I doubt it flies anywhere, used for gig to gig transportation. He had been doing that , I think, but was getting tired of doing it. And each time it would remind him of his mis-measuring.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

:Or presumably plastic knobs also. Owner of Roland piano had a flight case :made up for it but he did not allow for the knobs. Hacking into the foam :still leaves the knobs pressed against the outside face of the case. :Replacement knobs not possible as would have to be only 8mm high and do not :exist that shallow. : :How to mount in a lathe to cut down ? Cutting tool sufficiently sharp but :grip the knob in the jaws too tight and the Al of the knob deforms. Too :loose and it slips of course. Jubilee / hose clip around it and not enough :space between the jaws for the clip boss. :Nylon cable tie worked well enough to form a neat level line to then hand :hack saw / and bench-grind down to, but not enough force to fully lathe cut :the height down. Anyone been here before/ know the secret? for the next time :I'm confronted with the same predicament. :Perhaps an engineering solution, if an oft repeated job. A 5 to 10 mm thick :anulus of aluminium , with a radial cut and dimensions so a tight and :rigidly held grip in the lathe-juck. :Perhaps a smaller ground down boss structure of a jubille clip , for a more :general work-around, replacing the tightener with an Allen key grub screw :(hex set screw) to reduce the size.

I would not recommend using a f*ck-up to fix a f*ck-up... what happens when you have to replace a knob down the track? - more lathe work...

I would go back to the case manf if possible and get a deeper lid made and fitted - surely that is the best solution and you'll waste less time in the long run.

That's called an "expanding arbor". For example:

Best regards, Spehro Pefhany

Remove knobs before placing in case? Remake the case cover this time allowing for the knobs? To me, cutting the knobs is a hack job and I sure the hell wouldn't advise it.

On 5/13/2009 7:01 PM Ross Herbert spake thus:

Ah, but that's "N_Cook"'s preferred way of doing things, dontcha know.

I'd put a couple of layers of electrical tape around it & just throw it in the chuck. The worst that could happen is that the chuck could ding the skirt of the knob, or it could *spung!* out of the chuck.

Buy a £1.29p potentiometer with a long shaft spindle (they're sold like that so they can be cut down to length as required) - cut the spindle to normal length and use the offcut to fit the knob to a lathe chuck.

Cut holes in the case to clear the knobs and stick plywood patches over the holes - if the knobs foul the patches, hole them and stick a second layer of patches over that and so on.....................

It would be easier to file the top of the knob down than fit it in a lathe chuck, its easy to secure the knob in a vice, just buy a potentiometer with a long spindle and cut it down to normal length - the offcut can be inserted in the knob and clamped in the vice.

Good idea!

It'd all depend on how much material he needs to take off, & filing doesn't leave a very nice finish.

That'd depend on whether it's a 'D' section, or just a rod.