A pox on slide potentiometers!

Started by anotherjim, November 28, 2019, 05:02:39 PM

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anotherjim

I have a Router/trimmer, but it failed for this job - it looks like the smaller router slot cutters only have a cutting edge on one side and that's no good in aluminium - it just chatters to death. An end mill bit would work - if I could find a small, 3mm-ish one that would fit in the Router, but that said, all the clamping and jigging to cut x6 parallel slots is not appealing.

The old-fashioned way, to me at least, is to chain drill (series of holes along the centreline) and then saw/file to straight edges. This does rely on fairly accurate drilling so I'm planning to tool-up by getting a drill press and a cross slide table vice. I don't know how I've managed without a drill press for this long.

An unexpected hurdle is in finding the operating caps (I can't think of them as knobs). The typical mixer ones I don't like. The finger-friendly recessed shape means the depth of grip on the slide lever is very shallow. You will notice that many synths have tall caps that fit crosswise. These are a much better fit and don't add an overhang to the front to back travel. The only ones like this that I can find are huge 20mm wide things - even e-bay yielded nothing.
I found some tall mixer style caps that are only 10mm wide, but these still look too big for the slide pots.


This is what a Roland one looks like. They would be perfect. Believe it or not, the only way to get them is as expensive NOS spares or 3d print.
I cannot locate any generic supplies of anything like them.



duck_arse

a router bit to cut thin slots - that would really take the biscuit joiner.
You hold the small basket while I strain the gnat.

anotherjim

I didn't know a biscuit cutter was a special tool, but I don't think I'll invest in one.

Found some slider caps at RScomp...
https://uk.rs-online.com/web/p/potentiometer-knobs/4676077/
They also list a nicer style of Sifam brand, but out of stock, of course.
https://uk.rs-online.com/web/p/potentiometer-knobs/2799061/

PRR

> I didn't know a biscuit cutter was a special tool

So how do you cut biscuits? Hunk of small stove-pipe? They are just a few bucks.

But I think my Google calls what he is talking about a "biscuit jointer". However they are not made to eat metal, could be awkward on a panel instead of board-edge, and would leave a long taper at the end of the slot.

IMHO the way to go is to the pawn shop for some distressed graphic EQ. Use the whole panel slide-pots and all, just replace the electronics (scale values to suit the pots you are stuck with).
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SolderBoy

I guess you could try a cut-off or grinding wheel in a dremel with a remote hand-piece.  Use gloves and goggles though.  Those wheels can shatter and fly apart pretty easily.  And clamp the box to your bench...

anotherjim

The Dremel disc cutters don't do well in ordinary soft aluminium. If it doesn't break, you just get a disc smoothly coated in the metal. Same thing happens in most plastics, they melt through from friction heat rather than cut. But a more physical problem with a Dremel is the girth of the drill prevents side cutting on wide workpieces. I have a flexidrive option, but the one I got turned out to be not up to doing much work.

I could butcher something for a panel, in fact I have a midi controller I don't like or use with 9 faders - but I really am determined to make something that's as commonplace in music gear as slide controls a viable option for my DIY. I want to be able to make panels like this...

I can't imagine working one of those with rotary knobs - it would be totally crappy.


EBK

#26
Instead of cutting slots, why not cut strips of sheet metal and lay them next to each other with an appropriate gap?  Then, these strips can go over (or under) a large rectangular hole in the enclosure.  Again, just a thought.

Or, find someone with a CNC mill to cut the slots.
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Technical difficulties.  Please stand by.

tubegeek

Quote from: anotherjim on December 12, 2019, 10:16:10 AMa disc smoothly coated in the metal.

a/k/a "Hey honey! I bought you some cool new earrings!"
"The first four times, we figured it was an isolated incident." - Angry Pete

"(Chassis is not a magic garbage dump.)" - PRR

anotherjim

I thought of built-up from strip, Eric. A plastic such as styrene or ABS would be especially easy to work with to make a bezel overlay. It could even have graduation lines engraved and filled with paint. If I fail to make a clean job of slotting the panel, it may happen.
If the panel material was thinner and a bit more springy than what I have, I think the following would work...
Mark out the slots and drill them through at each end.
Strap/clamp the panel down around a piece of plastic pipe (rain/waste/drain size) so the slot lines will be running over a convex curve. The pipe will be sacrificed by this.
Use an ordinary hacksaw to cut across along the slot lines to the full length of the slots. Release the panel from the pipe and there should now be straight open slots in between the guide holes. Clean up with needle files.


EBK

A miter box might be handy if you go with that plan.
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Technical difficulties.  Please stand by.

tubegeek

Quote from: anotherjim on December 12, 2019, 04:41:20 PM
Strap/clamp the panel down around a piece of plastic pipe

Clever! I feel like that could work really well with the right material and the right cylindrical object. Lexan or Plexiglas maybe - Plexiglas is a bitch because it gums up saws something awful, though.
"The first four times, we figured it was an isolated incident." - Angry Pete

"(Chassis is not a magic garbage dump.)" - PRR

DIY Bass

With an appropriate fence and starter holes a jig saw or scroll saw could probably do it.  A scroll saw is fine enough that you would need to cut the slot as a rectangle though, not as a slot.  It would take longer but could give a nice finish.