Pot and knob compatibility

[VidSicious]

Hey guys! So I've been building pedals for over a month now and got a couple finished projects under my sleeve. But now it seems that I am facing an issue with the pots I got. Basically, I got a couple of big orders from Tayda (damn you discount codes!) and stocked up for the next 10 or so projects - making 2 of each. So the problem is that in my last build I used the pots I got from Tayda and I got all of them with smooth shafts. They're all completely round and I realised that the screw knobs have simply nowhere to grip on those shafts. What I ended up doing in my last build is using some heatshrink on the shafts which did work. But it makes it next to impossible to remove the knob without damaging it. And it also requires re-applying the heatshrink because it gets all messed up. I also tried drilling a small hole in the shaft for the knob's screw which didn't seem to help. Neither did blu tac.  I just wanted to ask what would you recommend to keep the knobs in place with these kinds of shafts? I got about 50 of them so can't let it all go to waste...

[davent]

The set screw doesn't need anywhere to grip, it can be tightened anywhere onto the smooth shaft and if  the knob and set screw are any good, will hold just fine. Certain Tayda knobs are known to lack the means to be sufficiently tightened and be of any use but i think that's a different matter.

A super stiff rotary switch shaft may require a knob with a pair of offset set screws to grip tight enough to get the job done, or knurled shaft with mating knob.
dave

[bloxstompboxes]

I have actually used knurled shaft pots with knobs that use a set screw. They fit over the pot shaft and the set screw definitely has something to bite into. I know it's not right but it works.

[davent]

Often times you can see an impression on the shaft, left by the  set screw, so it is to a degree biting into the shaft, but again that's dependent on being able to properly tighten the set screw.

dave

[VidSicious]

Thaks for the replies! Well, my knobs don't hold onto the shafts. They slip out if I turn the knob a bit harder. How would you attach it in this case? Not including glue, don't want any permanent connections between shaft and the knob.

[duck_arse]

find the mark on the shaft left by the set screw. run a flat needle file across the shaft at that point, to make a notch. replace knob, set screw. if the screw comes loose, the knob won't fall off.

(I'm stealing this idea from someone else, posted hereabouts a while back. don't start me on non-matching shafts/knobs.)

[bluebunny]

Tighten the screw enough that it leaves a mark, then drill a small dent at that point? If it's not obvious where it bites, try to paint a little ink on the inside end of the set screw.

[VidSicious]

The knobs hold on the shaft vertically fine. It's just if I rotate my pot to let's say 100% or 0%, the knob doesn't stop. It slips and you can still keep rotating the knob. I did try drilling a little dent with a 2mm drill bit (smallest I've got) but it seems that it leaves too wide of a dent so it doesn't really help.

[davent]

Tighten tighter... if you dare!

[PRR]

The classic interface is a *flat*. Lay the shaft in a vise. Run a coarse file over to remove about a mm of material. Clean with a fine file.

A proper factory flat is flat. Unpracticed hand-filing will taper. Try to work the taper "the wrong way", so even if the screw gets a little loose, it won't come off right away.

[smallbearelec]

I buy certain commodities (mostly capacitors) from Tayda for re-sale because the quality is competitive and the prices are good. That said, I only buy pots, knobs and switches from manufacturers whom I have dealt with for years. I don't argue price, so they have incentive to keep me (and my customers) happy by paying attention to quality. The problem with knob threads stripping out--which I think is what you are describing--is not at all unique to pieces from Tayda; it's a common and often-reported issue with heavily-discounted knobs from numerous on-line sources. To some extent, you get what you pay for. Even I have an occasional QC issue; the diff is that I know the provenance of what I sell and know whose chain needs to be yanked. The higher price that you pay in my shop covers the occasional need to send replacements and my time e-mailing the factories in Taiwan and elsewhere.

Try a few of my 1510 or 1900 series clones and see if you like.
http://smallbear-electronics.mybigcommerce.com/knobs-1/

[VidSicious]

Thanks! I'll try filing my pots. If that doesn't help then I'll stick with the heatshrink method. Smallbear, you are completely right. I've noticed that some items from Tayda don't seem to be of a decent quality but other items are okay. I guess you just have to buy different things from different shops. I'll definitely be placing some orders from small bear after all I've read about it

[deadastronaut]

ive had a few davies 1900h that i just couldn't tighten... , (tayda)

the screw would just shred the plastic.. ...

like steve says, you get what you pay for...

ive got some chicken knobs that have proper allen key screws in, no problem with those at all..

i wish they would put allen screws in ALL knobs, or tougher plastic, or both..

[Cozybuilder]

The great things about the plastic 1900h knobs are the size and wide variety of color selections- but as DA notes they strip. Quality small size knobs (about ½" or 13mm dia) are needed for small box builds, and I like these aluminum ones available from Small Bear. They have 2 set screws, no issues with stripping, and I think you could dye or stain the silver one if you wanted a different color (candy apple knobs anyone?):

http://smallbear-electronics.mybigcommerce.com/aluminum-flat-top/

[davent]

Somewhere i'm sure i've seen 19xx(?), the small ones, with a brass insert, see if i can track that down.

Found;
http://erthenvar.com/store/accessories/knobs/mini-fluted-knob-black
dave

And... i've always used the Small Bear version and never had any tightening issues, they're solid. This on the other hand, i would avoid at all costs, useless junk, from Tayda but i'd imagine typical of the other cheapies out that there not to mention the colours are anemic as well.

[bluebunny]

Thonk in the UK (www.thonk.co.uk) also does the small one, but with the brass insert.

[PRR]

Allen-key or slotted is a small difference. Though Allen may mean this is not the cheapest knob around. (Slotting saw is cheaper than an Allen punch.)

A long screw in good Bakelite will tighten well.

But in most of the modern plastics, screws will strip.

And short screws will strip even in good plastics.

Of course many of the lowest-price knobs are soft plastic with short screws.

The classic design has a brass insert for the screw to hold in.

Other all-metal knobs, like the Aluminum mentioned, are also good design.

Really classy gear has collet knobs. There is a tapered collar inside, somewhat like the chuck on a Dremmel tool, tightened with a screw in the end. Screw head covered with a snap-in cap. These cost $20 or more each, and are not readily available.

[hymenoptera]

The classic interface is a *flat*. Lay the shaft in a vise. Run a coarse file over to remove about a mm of material. Clean with a fine file.

A proper factory flat is flat. Unpracticed hand-filing will taper. Try to work the taper "the wrong way", so even if the screw gets a little loose, it won't come off right away.

Good idea!

This is something I've always struggled with, not because I've had trouble with my methods, I usually just drill a little detent to accept the set screw, but because I've always wondered if there's a "better" or "proper" way.

I think I will try to file a little flat next time, and maybe try to leave a slightly positive slope to the flat so that the knob gets loose before it decides to just come off. Gives a sort of warning before getting lost, right? I like!

[Cozybuilder]

Somewhere i'm sure i've seen 19xx(?), the small ones, with a brass insert,

Found;
http://erthenvar.com/store/accessories/knobs/mini-fluted-knob-black
dave

Sweet! Thank you Dave

[deadastronaut]

cheers marc ...now thats more like it.....bookmarked. nice one..


https://www.thonk.co.uk/shop/knobs-davies-1900h-clone-metal/