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Does anyone here mill their knobs? My guitar builder friend wants me to try making some knobs for him on my CNC Taig mill.

I get a nice finish on the side of things. The knobs he wants are straight-sided. I was thinking of milling thick circles and cutting the recess in the bottom. Then either turning them over and rounding off the top - or talking him into 2 piece knobs. ;->

I'm also looking for these inserts:



Anybody know where to find them???

...Athena

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This guy might be of some help. http://dknob.com/customknob.html It looks like he uses some sort of set screw collar type insert for solid shaft pots and maybe just a nylon insert for split shafts. After a closer look, he says acetal.


Bob

A lot of guys use set screws. I can't use them on these knobs. I saw the dknob site and have been surfing for what he describes to no avail.

I'm going to try e-mailing him and asking where he gets them. He might tell me to get lost. ;->

Thanks,
...Athena

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Athena I made these knobs on this guitar using my cnc router and a hand drill. It took me several tries due to not knowing the wood real well and having a not so good cnc machine and spindle. I know I have run out in the spindle and began programming taking that into consideration. Not knowing the wood cost me several attempts at this due to the wood chipping. Once I realised that I had to model the knob again to overcome that aspect of the wood, I then used the cnc to drill and mill the hole in the knob so that I had a tight press fit on the shafts of the pots. I did not have to use screws or inserts. Your results will surly vary due to wood, machine and a world of other reasons!



Try it on some scrap and see what you come up with. Sorry for not having close up photos.

Mike

I saw that McMaster has acetal tube, but I don't know the size required. Any soft plastic would probably work. I'm assuming that the pot shaft creates the grooves in the tubing and locks them into place. Not sure what kind of adhesive holds the plastic to the knob though. Guess it depends on the plastic.

Strat knobs are inexpensive enough to turn down to an insert like that. Then epoxy into stock.

If you could fixture them accurately you could wax pot shafts and cast epoxy.

We make our own wood knobs and make brass inserts out of tube. I couldn't get a decent finish routing the shape so we do the outside shape on a sander with a fixture.

We also cast our own knobs. Getting the tooling concentric without a lathe is really tough.

Sweet guitar! I love the walnut top. He's been press fitting the knobs so far. I think some of his clients have asked for new knobs to upgrade their older guitars of his and maybe he's concerned about them press-fitting them properly. I didn't really prod him for details. Regardless, he wants the plastic inserts, so I'm trying to track them down or make them.

I've been lucky so far with the small wood items I've made. I have a really small machine - a CNC'd Taig micro mill - so I don't push it or expect much in the speed dept.

I'm successfully making pickup rings now. I did the back of a P90 cover - hogged out the inside and made the holes. I'm waiting for some ball end mills to come to work on rounding over the top. I used an old wood carving ball burr to try my first test 3D part - a carved truss rod cover.



The sharp contrasty lighting shows off the grooves, but to the naked eye some people though it looked sanded already.

So knobs are next!

...Athena

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Thanks guys. I've read about people turning down strat knobs. I guess that's a fallback. I looked through McMaster's online catalog hoping to find pre-splined/grooved ones but had no luck.

I did e-mail David King of King Basses and he's a really nice guy. The acetal tubes are grooved with a broach. He doesn't have any of the type of inserts I think we need. I'm going to look into the broach though.

...Athena

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The casting idea is interesting. I have an e-pal with a Taig who's a jeweler who does a lot of casting. I'll have to talk to him about the possibility. I have a fourth axis I haven't hooked up yet so I might be able to fake some lathe action if necessary.

I noticed how nice your knobs where last time I was cruising your site. Even your black cast knobs are lovely. I wish I could talk this guy into multiple piece wood knobs. You have such lovely photos on your site. Do you shoot them yourself? I used to be a black background only person, but you've converted me... I love your grey background.

Thanks,
...Athena

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I wonder if you could:
A. Grind a piece of tool steel to ream out a tapered groove in the knob hole?
B. Use a dremel pointed bit to ream out a tapered groove in the knob hole?
It would seem that you could rotate the knob material every few degrees and just go up and down in the Z.
It could be worth a try anyway.

With your 4th axis you might be able to make your own broach and use it in a drill press (with the motor turned off). I had a machinist make me a rotating fixture with 18 stops kind of like a simple dividing head. I used this to hold 1/4" brass rod so that I could spline the end using the CNC. These rods went into our knob molds. In retrospect it would have been cheaper and easier to dissassemble pots.

Thanks for the compliments on our photos. They are done in-house with a pretty "ghetto" system that could use an overhaul. I'm kind of black backgrounded out too. I tried white first and thought the guitars looked too washed out.

Interesting discussion, guys, and a lot of the principles apply to making custom tuner knobs.
http://www.luthiersforum.com/forum/viewtopic.php?f=10106&t=26579&p=357345&hilit=tuner+knobs#p357345
I remember making a hardened hex punch years ago to punch an allen socket in a part.
Pre-drilling the hole as large as possible doesn't leave all that much material to shave but there is the question of where to put the "shave".
A blind hole can accomodate the shaving at the bottom or a blind hole with a relief at the bottom might allow them to break off and fall out.
The trick, at least when broaching steel, is to put some back taper on the punch so it doesn't drag all the way.
Nelson

I'm trying to understand why you all find it necessary to have an insert in the knob. From an engineering standpoint there is almost no stress whatsoever that would require an insert when the knob was mounted on a guitar provided the hole size is well controlled. The only reason I can think of to have an insert are the stresses that might be placed on the hole when the knob was turned on a lathe.

I make mine on a cnc and hold it in custom jaws while it's being machined. The hole is raw wood and it holds onto the poles beautifully without an insert. This is because the hole is interpolated, not drilled. For those that don't know; "interpolating" a hole means that a rotating endmill with a smaller diameter than the hole is walked around in a circle to create the hole. This allows extremely precise hole sizes to be created which probably is the reason I can get away with this.

If I ever NEED to: I can mill out the hole way oversized, seal the hole with shellac, fill the hole with epoxy, and stick it back on the mill to mill a new hole out of epoxy. That idea works very well for tuning knobs too.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart, do you find that the epoxy core holds up well long term in a tuner knob application?
That would be a much simpler approach and also the guys mentioned above casting a waxed shaft profile into the wood for a pot knob.

It's not me making the decision. I was just asked to find the suckers.

I talked to my friend about this and he's concerned about slippage and longevity. He does 5-way rotary switches sometimes and I know how tight those are. He doesn't want the knobs eventually slipping on a spirited player at some point in the guitar's future. He does have some pro player customers.

I think he expected I could just order them somewhere online. He has some knobs he got off ebay a long time ago that had these serrated inserts.

...Athena

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I've seen wood knobs go out of round with humidity and get wobbly. I think a stable insert is pretty important.

I'd rather be safe than sorry. Tommy Kessler has a few of his guitars and is on tour with Blondie. Lindsey Buckingham and Neale Heywood of Fleetwood Mac are touring with them. You're got pro players. You know how that is. Touring can be tough on a guitar.

...Athena

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Not enough time to tell really. I just had the idea fairly recently. I made a batch of epoxy filled keys and they turned out very nice but since the ones I made with simple wooden holes from bloodwood seem very well secured to me I haven't needed to use them. I sort of want to try out the "just wood" keys and leave those epoxy keys as a backup in case I need them. I abuse them on purpose by aggressively using a plastic winder but I haven't the heart to bang them against a table or anything. I also have some milled inserts made of aluminum that can work in lieu of the epoxy as a last resort. Out of three solutions...the best one is always the easiest.

One thing I learned when making the epoxy filled holes is to get some shellac in a syringe and fill up the overmilled hole prior to using the epoxy. You let it set maybe ten seconds and then dump it out. This seals the inside of the hole so when using porous woods, the epoxy won't seep through the pores and mess up the surface of the tuning key. This could also be accomplished by applying a seal to the outside too (I think) but sealing the inside of the hole prevents a lot of bubbles from rising during the curing of the epoxy.

You can prepare for some tiny bubbles to rise in the curing cycle by overfilling the hole up to the point of creating a dome above the hole. The surface tension of epoxy is very high. This will allow the bubbles up into the dome so that when you shave it flat it will be bubble free. Or you could just make a throw away section on the key itself - to mill off the surface bubbles later. Either way.....you'll have to address the issue of bubbles rising in the cavities. It's simple if you expect it.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I understand. I'm only thinking about my application.....which is two SD p-rails and two volume knobs. Those rotary switches would require something more, I expect.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I missed the rotary switch part. We have longterm testing results with rotary switches. Unless you use the Stew Mac splined shaft switches you'll need a grub screw. If you're using a grub screw you'll need a brass insert. We tried epoxy and JB weld for molded inserts with grub screws. They eventually stretched and slipped. Look for heavy wall brass tube, threaded inserts and drill them out, bronze bushings etc. What ever you can find locally and cheap. There's not much of a market for $40 knobs so every penny counts. If you have a 3/8" collet on your Taig you could fixture a drill and a reamer in a vise and while you're at it a parting tool held horizontally. Then you could mill solid bar stock by spinning it in the collet and plunging the onto the drill, then the reamer, then a horizontal move to part it off.

Pay attention to the rake angles of your cutting tools when working with brass. It gets really grabby with positive rake tools. Grinding a zero rake onto the tip of your drill and parting tool will make things much smoother and safer. I have the scars to remind me of this.

I'm guessing he uses the Stew Mac ones. He's pretty friendly with them. They're selling his bridge now. But I'll definitely check on this.

I do have a 3/8" collet. I haven't used it yet. That's an interesting idea that gives me more interesting ideas. Thanks for the advice about brass. I appreciate being able to learn from other people's scars. I have some of my own from larger factory automation in the 80's, but even a tiny machine can chew up fingers quite well.

Thanks for all the great info,
...Athena

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Ah, Schroeder?

Here's a video of the process. It's pretty cool just from an entertainment standpoint.

http://www.youtube.com/watch?v=wbfXXeiS ... re=related

Yep.
Crazy setup! That's really cool! Man these Taig owners are really ingenious. I learn something every day about this little beastie.

Thanks!
...Athena

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