# cutting these threads



## kd0afk (Dec 23, 2012)

How would one cut threads on a classical guitar tuning machine so that the thread has no relief and with no cnc? Would I use a retractable tool holder and plunge in when I engage the half nut?


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## kd0afk (Dec 23, 2012)

Forgot the photo.


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## sssfox (Dec 23, 2012)

The only way I can think of doing it is to hand-turn the lathe spindle.
A spindle crank would come in handy.

I'm not nearly coordinated enough to advance the cross slide the right amount on a consistent basis for this type of work..

I imagine they cut them with a hobbing machine.

Steve Fox


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## kd0afk (Dec 23, 2012)

The gears are definitely hobbed and i didn't even think of hand cranking. Go nice and slow for a.really smooth cut. I'll bet there is a machine made just for doing this. Might be an interesting project to build a hand crank worm cutter. Might be a good selling point.


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## MuellerNick (Dec 23, 2012)

These threads were whirled. Unless you do heve a whirling head for your lathe, you can't do it.
Only option would be a live tool in your lathe and mill it.

Nick


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## dave-in-england (Dec 23, 2012)

I have the same tuners on my own guitar.

I can definitely say that these spindles are made on a special purpose grinding machine, with a thin, pre-shaped grinding wheel.
You can see that the thread does not run off the end of the shaft,  the grinding wheel is retracted before it reaches the end of the shaft.
This is probably about 10 T.P.I. pitch, with an odd shaped form.

Even if your lathe has such a rare option, you would have a lot of trouble pulling the turning tool out instantly at the end of the thread.

Maybe a less stressful visit to Ebay  ???  Ha Ha.


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## MuellerNick (Dec 23, 2012)

Who on earth would grind threads like these?
If you know how whirling works, it is obvious how easy it is to start and stop a thread in the middle of any stock.
The end of a whirled thread has a radius of at about 5 to 10 times the thread's Radius. That radius is convex, but you could make a straight disengaging path of the tool if you care.


Nick


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## fltenwheeler (Dec 23, 2012)

MuellerNick said:


> Who on earth would grind threads like these?
> If you know how whirling works, it is obvious how easy it is to start and stop a thread in the middle of any stock.
> The end of a whirled thread has a radius of at about 5 to 10 times the thread's Radius. That radius is convex, but you could make a straight disengaging path of the tool if you care.
> 
> ...


 

Hi Nick

I can find videos on new CNC thread whirling. Did they make older machines (non CNC) that would do it?

Tim


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## MuellerNick (Dec 24, 2012)

Whirling, works om manual lathes to. It only requires a whirling head and low spindle RPM.


Nick


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## kd0afk (Dec 24, 2012)

I think I'll try finesse before I guy a whirling head.


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## kd0afk (Dec 24, 2012)

Why not use a retractable cutting tool that runs along a plate and the ends of the plate curve outwards so that when the cut starts and ends it is eased in and out of the cut consistently. I think that would work.


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## Woodster (Dec 24, 2012)

It could be done with a copy turning attachment and a milled profile.


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## Journeyman (Dec 24, 2012)

If it is for a guitar it would probably be easier to get a new set of tuning heads from a luthier. On the other hand as an exercise it could be made in two parts:- cut the thread as normal working from one end of a bar. A hole up the middle for the thinner shaft and then silver solder  / loctite a fat washer on the open end. Finesse the ends of the thread / worm with a file. Voila... Merry Christmas

John


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## abby (Dec 24, 2012)

If I had to make them I think I would cut the thread in the lathe , enough length for a dozen or so.
Drill through and part off to length .
Make separate parts for the spindles and silver solder the assembly together.


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## dman (Dec 24, 2012)

i'm not sure how they do these but i'm sure it was once done on special machines. they may have been wirled but i don't know anything about wirling, but notice the helix plunges to a point gradually and retracts to roughly match the shape of the gear? this would be difficult to do with a lathe. they may have been hobbed. 

but if you dont care for reproducing the part exactly and would settle for function over form you could use the grooves as your relief and grind your own threading tool. there should be enough surface that i don't think the end of the thread will catch on the hooks that hold the piece in.


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## napoleonb (Dec 25, 2012)

Not sure if it would work but using the same method for creating wormwheels, when you make a hob and put it in the spindle of your lathe and the workpiece attached to your qtcp, reverse this procedure and making a hop which looks like the gear on which you wind your strings and put that in your qtcp.

Seems like an awfull lot of work but its the only easy way I can think of making it in one piece and being able to duplicate.

Another trick which should work is using the headstock and put it off centre and cut the thread half-way, making it conical to the inside. Mind your cutting angle! and then reverse the headstock the other way. I've seen tapered injectionmold spindles been made this way, even with changing pitch (running in from 2 sides with an overlap)


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## mcostello (Dec 25, 2012)

I have a South Bend Lathe with a low gear speed of 40 rpm and a Dial Indicator for a stop. Stopping exactly would not be hard. Starting exactly would be another matter without making a ring around the part.


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## MuellerNick (Dec 25, 2012)

> Stopping exactly would not be hard.



May not hard for you. But hard for the tool and the lathe. Imagine what happens after a few passes when the tool hits the wall (left by previous passes).


Nick


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## n4zou (Dec 25, 2012)

I would put a 10:1 ratio reduction gear box on the motor. This would provide a spindle speed of 5.5 RPM if the lowest speed without the 10:1 box was 55 RPM which is common on most lathes. It would be very easy to start and stop thread cutting at that speed. You might even get bored waiting for the start of the thread to turn the compound dial so you can start each cut.  Backing it out at the end of the cut would be even easier.


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## mcostello (Dec 26, 2012)

Yes that did happen, must be vigilant. Darn half nuts jamb up pretty quickly when that happens, I did know that not everyone has the luxury of a slow speed, but then I have the luxury of a top speed of 800,it's all a compromise somewhere.


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## kd0afk (Dec 26, 2012)

I just found this photo. I think they are also hex broached and on a hex  shaft. I haven't looked yet but can you broached something that small?


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## kd0afk (Dec 27, 2012)

I figured out how I could do it. I would build a machine that was like a miniature lathe with a cariage. Instead of a cutting bit with the work spinning fast under motor power it would be hand cranked with a retractable rotary tool with a profited mill. You would push in on the cutting head and it would engage a screw and you would crank twice, stop where you want the thread to end and pull back. Each piece would be done separate but this would be precise and the action of the thing tune would be like butter.


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## kd0afk (Dec 27, 2012)

I just thought about it and when you push the cutter head forward it would lock in place in an index with a pin You would rotate slowly and then when you got to the end of the thread you would lock the spindle in place and unlock the cutter head by pulling up the pin and push it through.


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## MuellerNick (Dec 27, 2012)

> Instead of a cutting bit with the work spinning fast under motor power it would be hand cranked with a retractable rotary tool with a profited mill



That's called live tool. Posting #5.


Nick


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## kd0afk (Dec 27, 2012)

MuellerNick said:


> That's called live tool. Posting #5.
> 
> 
> Nick



Sorry. What about instead of a rotary tool, use a file in a guide?


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## 3jaw (Feb 23, 2013)

Here are some tuning machines I made a few years ago along with the tooling: http://bbs.homeshopmachinist.net/threads/32324-Tuning-machine-gear-material

Hope this helps.


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## toolroom (Feb 24, 2013)

Go to Frets.com/machine, He is a guitarist and makes all these, plus more. I am sure you will wish to put his site in your favorites.
Dinkin'


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## dman (Feb 24, 2013)

toolroom said:


> Go to Frets.com/machine, He is a guitarist and makes all these, plus more. I am sure you will wish to put his site in your favorites.
> Dinkin'



i dunno if you'll see a way to make tuners but frank ford is a master luthier and has a lot of great stuff on his site for woodworking, basic electronics, and machining.


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## BrianS (Feb 24, 2013)

Interesting thread.  I tried that link given Frets.com/machine but it does not work for me.  Not sure if it's just me or maybe the site is down or the link is incorrect.


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## dman (Feb 24, 2013)

kd0afk said:


> I figured out how I could do it. I would build a machine that was like a miniature lathe with a cariage. Instead of a cutting bit with the work spinning fast under motor power it would be hand cranked with a retractable rotary tool with a profited mill. You would push in on the cutting head and it would engage a screw and you would crank twice, stop where you want the thread to end and pull back. Each piece would be done separate but this would be precise and the action of the thing tune would be like butter.



you could make strait thread with the same form and pitch on a hardenable tool steel shaft in annealed form, cut grooves in it and harden it and use it as a hob to make a gear from the same material and cut a groove in the gear at center height and it may work as a hob to cut threads in the final shaft with the right lead in and lead out... you may need to drive the hob with a threaded shaft geared to the spindle to keep it all timed. i'm not sure how well hobbing works making a screw but it might be easier than making a whole machine to single point it.


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## dman (Feb 24, 2013)

http://www.frets.com/HomeShopTech/hstpages.html

here's the machine shop stuff.. haven't found any tuner parts making yet though


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