# Anyone ever reamed out a 6mm aluminium knob for a 6.35mm shaft? Good idea or not??



## xefned (Sep 25, 2022)

I wanna order these groovy ass knobs for my next envelope filter, but I can't find a 6mm shaft pot in reverse log 100k (not even from Tayda.)





I have a harbor freight drill press and below-average skills with it. Can I ream these out? Is it worth trying? Or am I gonna end up with a case of regret and an emergency room bill?


----------



## Bricksnbeatles (Sep 25, 2022)

Just a heads up— I have a set of those knobs, and they’re incredibly tiny. I’ll snap a pic in a bit, but I was expecting them to be larger (when I bought them no dimensions were listed. Idk if that’s still the case). 
They’re definitely cool, but yeah.


Anyway… if you want a reverse log 100k pot but can’t find it, worry not— if you can combine a 1M linear pot with a 110k resistor to get a 100Kc pot. As long as you can find 1M linear pots with a 6mm shaft, you’ll be golden!


----------



## Bricksnbeatles (Sep 25, 2022)

https://imgur.com/mr5Fc7K




https://imgur.com/BNUHJPW


----------



## peccary (Sep 25, 2022)

6.35 mm is 1/4", so a 1/4" bit will get you there. I use an oversize reamer when I make knobs but a straight up 1/4" drill will almost always drill a hole slightly larger so you should be fine (the knob hole needs to be slightly larger than 6.35 to actually fit on the pot), just make sure to have a small file to de-burr.

I think the hardest part will be finding a secure way to reliably hold it.


----------



## xefned (Sep 25, 2022)

Bricksnbeatles said:


> Anyway… if you want a reverse log 100k pot but can’t find it, worry not— if you can combine a 1M linear pot with a 110k resistor to get a 100Kc pot. As long as you can find 1M linear pots with a 6mm shaft, you’ll be golden!



Super helpful dude. TYSM! 
I was always told, “you can only change the value for a linear pot” to another (smaller) value. I had no idea you could do log or anti-log. I've clearly been misinformed! Thanks. I need to research this and update my knowledge for this century.  Jeez. What a breakthrough.

Thanks for the picture. Wow. They might be actually _too small_ for a 125b. Maybe better on a tiny 1590a build. How do you like them? Are they still usable? (If you've tried them on a pedal.)

Thanks duder.


----------



## xefned (Sep 25, 2022)

Bricksnbeatles said:


> https://imgur.com/BNUHJPW



Them's small AF. Amazon review shows them overshadowed by a _dime_. Yikes! 
Having 2nd thoughts about these. 






peccary said:


> I think the hardest part will be finding a secure way to reliably hold it.



Yeah, I'm thinking some vice grips to hold the knob still. And some cloth fabric to keep from marring the finish. 

I'll report back if anyone's curious.


----------



## swelchy (Sep 25, 2022)

I've drilled aluminum knobs out to fit 6.35 in a pinch and it worked fine


----------



## temol (Sep 25, 2022)

xefned said:


> I can't find a 6mm shaft pot in reverse log 100k (not even from Tayda.)


A-2577 and  A-1952


----------



## xefned (Sep 25, 2022)

swelchy said:


> I've drilled aluminum knobs out to fit 6.35 in a pinch and it worked fine


I'll try it. Thank you!



temol said:


> A-2577 and  A-1952


I'd originally written those 2 off for 1 being not-PCB mount (important) and the other for having a knurled shaft. But I think I can make that work. 

I've used the knurled shaft pots before with set-screw knobs and they usually work. The only time it was really bad was when the set screw was perfectly parallel to the split middle seam. I tightened it too much and crushed the two halves together. But if I'm careful, I can avoid that.

Thanks for making me give those a 2nd look.


----------



## peccary (Sep 25, 2022)

xefned said:


> Them's small AF. Amazon review shows them overshadowed by a _dime_. Yikes!
> Having 2nd thoughts about these.
> 
> View attachment 32877
> ...


Aluminum soda cans work well to protect things. That's what I use on my lathe, at least.


----------



## MichaelW (Sep 25, 2022)

swelchy said:


> I've drilled aluminum knobs out to fit 6.35 in a pinch and it worked fine


Me too, just mind that you're drill is square or use a level. (Been there done that....the wrong way...hahah)


----------



## Bricksnbeatles (Sep 25, 2022)

xefned said:


> Super helpful dude. TYSM!
> I was always told, “you can only change the value for a linear pot” to another (smaller) value. I had no idea you could do log or anti-log. I've clearly been misinformed! Thanks. I need to research this and update my knowledge for this century.  Jeez. What a breakthrough.


I’m trying to create a resource for displaying the effect of tapering resistors on pots in the same style as the Duncan Tone Stack Calculator. Adding a resistor in parallel with lugs 1 and 3 of a pot will always bump the middle of the range, so a log pot will become more linear and a linear pot will become more anti-log. The basic formula I use for linear to anti log (90% resistance @ 50% rotation, since that’s what a C-taper pot is) is 10XΩ Lin pot and (11/10)XΩ resistor. It has the benefit of being a true anti-log curve too, instead of the dual-slope curve of most log and anti-log pots. 



xefned said:


> Thanks for the picture. Wow. They might be actually _too small_ for a 125b. Maybe better on a tiny 1590a build. How do you like them? Are they still usable? (If you've tried them on a pedal.)
> 
> Thanks duder.


Yeah, they’re teeny tiny! I dig them. Haven’t used them on a pedal at all (since no indicator dots), but they’re pretty looking knobs and nice for drone synths. I actually planned on using them on a guitar, but they were way too tiny for that 😂


----------



## Mentaltossflycoon (Sep 25, 2022)

I've reamed aluminum knobs successfully and I've used the black version of those knobs. Comically tiny.


----------



## Joben Magooch (Sep 26, 2022)

Done it a few times on drill press...Hardest part for me is finding a way to securely hold the knob AND keep it at a perfect 90 deg... Have more than my fair share with a slightly tilted hole so that it spins a bit crooked.


----------



## Passinwind (Sep 26, 2022)

xefned said:


> Super helpful dude. TYSM!
> I was always told, “you can only change the value for a linear pot” to another (smaller) value. I had no idea you could do log or anti-log. I've clearly been misinformed! Thanks. I need to research this and update my knowledge for this century.  Jeez. What a breakthrough.





			The Secret Life of Pots


----------



## Alan W (Sep 26, 2022)

How about wrapping the knob with masking tape and putting it in the drill press? (Assuming you have a big enough chuck.) 

First, you’d take the 1/4 inch drill, and drill a hole into a thick (1 inch plus) small scrap of wood. Then, stick the shaft of the bit into the wood. Basically, it would be as if you were doing this on a vertical lathe—spin the part, into a stationary bit. The bit will self center. You’re opening up the diameter 0.35 mm, which is under 1/64th inch, so it’s not by much.


----------



## benny_profane (Sep 26, 2022)

Bricksnbeatles said:


> I’m trying to create a resource for displaying the effect of tapering resistors on pots in the same style as the Duncan Tone Stack Calculator.


You might find this worth checking out:


			Analog Alchemy - EMH
		


It doesn’t have the amount of detail you were talking about nor a visual representation of the sweep, but it’s still handy if you approach it with the understanding that there will be idiosyncrasies involved with altering a pot value with parallel resistors.


----------



## fydo (Sep 26, 2022)

I've also done this before (with a handheld drill) and ended up with slightly crooked knobs because despite my best efforts it was not drilled at a perfect 90 degree angle. In this case, it's hardly noticeable unless you're looking for it but I'd still recommend using a drill press or some kind of jig that would allow you to drill it at a perfect 90.


----------



## xefned (Sep 26, 2022)

fydo said:


> …despite my best efforts…


Mine are guaranteed to be crooked given my experience level but, that's how you learn. 🙃



benny_profane said:


> It doesn’t have the amount of detail you were talking about nor a visual representation of the sweep, but it’s still handy if you approach it with the understanding that there will be idiosyncrasies involved with altering a pot value with parallel resistors.







I'm guessing we can use this graph along with this calculator to do a 2-resistor solution. 
So in my case, a 110kΩ resistor + a 10kΩ resistor if I'm understanding right. (I'll experiment.)


----------



## Passinwind (Sep 26, 2022)

xefned said:


> Mine are guaranteed to be crooked given my experience level but, that's how you learn. 🙃
> 
> 
> 
> ...


If you want to end up at 100K you'll need to start with something like a 1 Meg linear pot and a 110K resistor.

I tend to just throw the whole mess in LTspice, although doing accurate pot log taper sims is sometimes not its strongest point.


----------



## xefned (Sep 26, 2022)

Passinwind said:


> If you want to end up at 100K you'll need to start with something like a 1 Meg linear pot and a 110K resistor.



Oh yeah. I'm dumb AF sometimes. The page even says, "Values are in kiloOhms."
Post above updated. Thank you.


----------



## Passinwind (Sep 26, 2022)

xefned said:


> Oh yeah. I'm dumb AF sometimes. The page even says, "Values are in kiloOhms."
> Post above updated. Thank you.


It happens to all of us sooner or later. Better to catch this stuff before you throw down money for parts!


----------



## HamishR (Sep 27, 2022)

Drilling out the hold in an aluminium knob isn't difficult if you have a drill press. The key is simply to go really slowly. I've used locking pliers with cloth around the pot before and it works ok. The other thing to do is have the base of the drill press wound up nice and close to the drill so you can keep the knob flat on it. Then it's not so hard to keep it all square.


----------



## Fizz (Nov 10, 2022)

Is 16mm 6.35 shaft the usual size everyone uses for pots?


----------



## xefned (Nov 10, 2022)

Fizz said:


> Is 16mm 6.35 shaft the usual size everyone uses for pots?



Yep. Those 2 metrics are what you want: 16mm pot, 6.35mm shaft (aka 1/4" shaft.)

Although you can get away with 6mm shaft if 6.35 is out of stock on a value. But the knob can become _ever so slightly_ off-center if you do, assuming you're using knobs for 1/4" shafts.


----------



## Nic (Nov 10, 2022)

Or if you find some knobs that are not 6.35, you could order the pot with the right shaft. But I found it best to stay 6.35


----------



## SYLV9ST9R (Nov 10, 2022)

xefned said:


> Yep. Those 2 metrics are what you want: 16mm pot, 6.35mm shaft (aka 1/4" shaft.)
> 
> Although you can get away with 6mm shaft if 6.35 is out of stock on a value. But the knob can become _ever so slightly_ off-center if you do, assuming you're using knobs for 1/4" shafts.


That's what brass pot sleeves are for!
I always keep a handful if I can't find a pot value in 6.35mm


----------



## Feral Feline (Nov 12, 2022)

xefned said:


> ... The only time it was really bad was when the set screw was perfectly parallel to the split middle seam. I tightened it too much and crushed the two halves together. But if I'm careful, I can avoid that.
> ...






You know the little tab that you break off to sit the pot flush in the enclosure?





That’s the one…




It’s a snap…




Where’d it go?




Bam! Right up the snout of the ol' Spice Weasel!


It just so happens that, in most cases, the little breakaway tab is the perfect size to jam into the split, thus preventing a knob’s set screw from pushing the split together and wrecking the pot right away or through long-term fatigue.

I've jammed it in and it's usually solid without any additional fuss, BUT...

If you're unsure that the little tab won't stay put or you find a pot with a tab that most definitely shifts around in the split (like the one in the above photos), then just add a dab of solder to keep it in place. This one will require a dab of solder, on either/both side(s), not on top, so the severed tab sits flush with the top of the split, allowing the knob to sit all the way down.



Of course, only do this tab-trick for set-screw knobs, the knobs meant for splined split-shafts don't work so well once you solder the tab in.

I rarely use split-shaft pots, and prefer set screw knobs...


----------



## RetiredUnit1 (Nov 12, 2022)

xefned said:


> I wanna order these groovy ass knobs for my next envelope filter, but I can't find a 6mm shaft pot in reverse log 100k (not even from Tayda.)
> 
> View attachment 32871
> 
> I have a harbor freight drill press and below-average skills with it. Can I ream these out? Is it worth trying? Or am I gonna end up with a case of regret and an emergency room bill?


You'll definitely need the ER unless you use a vise.  Reaming out with a drill going the proper direction will bite the edge and yank that sucker right out of your hands.  However,,,,, if the drill is going the opposite direction there will be no yanking.  It'll take longer but you won't need any bandages.  I'd still use a vise tho, large holes in fingers never quite heal all the way.  I have some that are 20 years old and still kinda sensitive.


----------



## xefned (Nov 14, 2022)

Feral Feline said:


> View attachment 35877



Thanks, Meower. This is the best thing I've learned in a long time. The best tricks are hiding in plain sight.
As well as the phrase "Spice Weasel." Thank you.


----------



## music6000 (Nov 14, 2022)

xefned said:


> Thanks, Meower. This is the best thing I've learned in a long time. The best tricks are hiding in plain sight.
> As well as the phrase "Spice Weasel." Thank you.


I just recently purchased this set for my dremel, They are Great & you can't beat the price!
When working with Aluminium with burrs, Be careful & use wax to stop burr from clogging up & clean regularly with wire brush!





						Double Cut Carbide Rotary Burr Set - 10 Pcs 1/8" Shank, 1/4" Head Length Tungsten Steel for Woodworking,Drilling, Metal Carving, Engraving, Polishing : Amazon.com.au: Home Improvement
					

Double Cut Carbide Rotary Burr Set - 10 Pcs 1/8" Shank, 1/4" Head Length Tungsten Steel for Woodworking,Drilling, Metal Carving, Engraving, Polishing : Amazon.com.au: Home Improvement



					www.amazon.com.au


----------



## Feral Feline (Nov 15, 2022)

xefned said:


> Thanks, Meower. This is the best thing I've learned in a long time. The best tricks are hiding in plain sight.
> As well as the phrase "Spice Weasel." Thank you.



I did not originate the term, as you may well already know.


----------

