potentiometer shaft cutting

[selloutrr]

Is there a specialisted tool for cutting off the unwanted length of a potentiometer shaft?

I've got a box of Clarostat pots that have a 2" shaft I hate the idea of using a hacksaw or dremel, since the shaft rotates with the cut, heats up, and the pressure causes strain on the shaft.

I'm assuming since clarostat made them so long they probably also made a tool to shorten them?

[Ken Moon]

I wrap the pot body in plastic wrap and a rubber band (even though it's sealed, it keeps it nice and clean), and use a little pony vise with small jaws that can securely grip just the shaft and not the body of the pot.

Then I cut the shaft using a new, fine-toothed hacksaw blade, being careful to stay perpendicular.

If you're not a fast-cutting madman with the hacksaw, it won't heat up enough to hurt anything

...and it's a lot easier than it sounds.

[jaysg]

Dremel cut-off wheel

wear goggles or large glasses...shards fly off when they shatter...and they always shatter after a few goes

[Ken Moon]

Whatever you use, you still should clamp the shaft in a vise. You don't need a fancy one - this one would do just fine:

http://cgi.ebay.com/1-1-2-Mini-Clamp-Be ... 539wt_1137

[selloutrr]

guess I could build a jig so each cut was the same. It just seems like there would be a specialty tool. with factory preset dies for industry standard lengths. Probably a large hydrolic press, not residential friendly.

Last time I used my dremel I was doing some ghetto spay paint powder coating in the garage, door open of course. but as it was baking in the toaster oven it caught fire. My first reaction is to pick it up and put it out on the drive way but the Oven was to hot to touch and the flames started getting out of the glass door front. I unplugged it and grabbed the fire extinguisher. flipped open the door the flames rushed out about 5ft above the work bench. The whole time my 4 year old is on the driveway playing hop scotch yelling "Daddy if you burn the house down i'll tell mommy!" I squeezed the trigger and put a good half of the tank into the oven and the flames out in the process, but there was no where for it all to go so the chemical shot back all over the bench and garage. I was somewhere between Oh shit this is going to burn the house down and damn playing with fire is fun. I dragged the toaster oven outside by the power cord and hosed it out until it was good and wet. When it was cold enough to touch I through it away. I can still taste the chemical just thinking about it. Yuck!

[Ken Moon]

Toaster ovens are evil fire beasts from hell

[martin manning]

Stick the pot's shaft in a drill press, or even an electric hand drill (may not be deep enough to do a 2" shaft in one go). Space it out by the length you want plus allowance for the saw kerf. Run the drill at slow speed and work the saw next to the chuck's jaws. The cut will be nice and square. Cover the pot, especially if it is in a vertical position. An Xacto razor saw will work if the shaft is aluminum or brass, and make a nice cut due to it's fine pitch.

[M Fowler]

I used a mini pipe cutter to get a perfect groove all the way around and then use a large cutoff wheel. The cut off disc will follow the groove then.

Mark

[Structo]

All good ideas.

The drill press idea is interesting.

The one think you want to avoid is of course getting any crap inside the pot but also over heating the shaft to where the wiper or element get damaged from excess heat.
I don't know why they sell those pots with the long shafts but a slow hack saw and a file should make quick work of it unless the shafts are steel.

[David Root]

The Claro, PEC and old A-B pots are all hard steel shafts, I like the drill press solution too, I have one.

Last time I did one I ground it down on my belt sander with a worn down #36 grit belt, the pot shaft got quite hot but I had it clamped in a Vise-Grip over the part of the shaft I wanted to keep. How good a heat sink that might be I don't know.

Only slightly off-topic, has anyone besides me noticed that the PEC audio taper pots that AES is now selling are perfect, short bushing, short shaft, and cheaper than Digikey at $9.95 each?

[Phil_S]

If you mess up a little, a simple mill file will fix it so it's level. square, plumb, whatever is the right word. You can eyeball it. Once you put the knob on it, you won't ever see it again.

[selloutrr]

Awesome ideas! Ok old school it is.... I'm going to summon my inner Omish and saw...


PEC pots are cheap at Antique electronic supply as well.

I'm wondering if the Clarostat RV4 series will allow the ground buss to be soldered on the back of the pot. I believe I read it's an aluminum housing.

Any ideas which series of Clarostat some of the Ken's older Wrecks used?

[ToneMerc]

Only slightly off-topic, has anyone besides me noticed that the PEC audio taper pots that AES is now selling are perfect, short bushing, short shaft, and cheaper than Digikey at $9.95 each?

Yeah, 6 of 8 of those are in my 100W high voltage build and they have a .335 shaft length which is perfect for typical pedal knobs. The other two I purchased locally (NTE rebranded) have .460 shafts and while they fit Marshall knobs perfectly, they of course don't allow the pedal knobs to fit as close to the chassis as the shorter shafts.

PEC produces 4 different shafts lengths, I'm glad someone decided to carry the shortest shafts.

[ToneMerc]

dup

[tubeswell]

+1 for the hacksaw and vice method. Use it all the time - with a little metal file to tidy up/flatten the edges afterwards. Just make sure the ally dust doesn't get into the pot