Repairing Vintage Kluson Tuning Machines

 Repairing Broken Kluson Tuning Machines

Today we are fixing one of the most common breaks on a set of 3-on-a-plate Kluson "single line" tuners. The D tuner shaft sustained an impact and the cast brass had sheared. These tuners were designed to remain sealed and so opening them seems daunting but they are quite simple in design 

You can seriously disfigure and even ruin your tuners if done improperly and patience is key to success. If you're unsure, STOP, install a set of replacement Klusons, and keep the originals in the case for a proper repair

This is the wrong (but far too common) approach.
If the tuners were simply removed and replaced then these could've been repaired

Shame because these were a rare set of Safe-Ti-String posts with butterfly buttons

What You'll Need

• At least one donor Kluson tuning machine from the same era (I have yet to see if the reissues will work)
• Ball peen or similar small hammer
• Junky wood chisel
• Nail punch (a few different sizes wouldn't hurt)
• Padded bench vise
• Needle-nose pliers
• Soldering Iron
• Thin CA glue with a whip tip

The Process

Using a cheap chrome vanadium chisel, I bend the forward tab upwards where I can use a nail punch and ball peen hammer to carefully bend the tab to a vertical position. Use light taps and try not to lever off the plate! If you stress the tab too much it will snap off and then you're in trouble 

Then tap the tab through the plate and you should be able to carefully bend the casing backwards enough to remove the broken worm gear. 

 Have you ever broken off the tab on a soda can by rocking it back and forth? You don't want that to happen so the fewer times you bend the back tab, the better

Here is the broken brass worm gear and shaft with the replacement I pulled from a 'donor' set of broken Klusons. It doesn't matter if your part comes from the treble or bass side, they will work all the same. I'll use alcohol to clean off the old grease and crud

Seat the replacement worm in the tuner casing and make sure it fits

Now you will gently bend the casing back into place, you may need to bend the front tab so that it is aligned with the hole in the plate.

The plate has become slightly bent, this isn't difficult to fix but I would recommend waiting until the end

Using my padded vise, I compressed on the tuners which seated the casing back into the plate and locked the worm gear in place

Using a nail punch and taking gentle hits, I bend the tabs back into place. If your punch slips you'll scratch the back of the plate which isn't the end of the world but looks cleaner if you avoid it

I'm no machinist so I don't really have a go-to lubricant for these parts (friendly reminder WD-40 is not a good choice) but I use 3-in-one PTFE and it has worked out well for me

Put the broken shaft into your padded vise with gentle pressure and use a soldering iron to apply heat. If you get the shaft too hot, you will melt and distort the button. I typically apply heat for 10-15 seconds, pull on the shaft with needle nose pliers, rinse and repeat until it's free. 

Now the button is free from the broken shaft and we can see two bends which would be consistent with a collision. The tuner button got slightly hotter than desired and the button has formed a small collar of melted material around the hole. I'll use a sharp razor blade to trim it back.

Note that the shaft has a "spear" shape with a "wing" on either side, this cuts into the button and prevents them from spinning freely on the shaft. 

Using your soldering iron again, heat up the worm shaft on your tuners (until the string post is warm) then press the plastic button down on it. Then, acting quickly while everything is warm, put the tuners into a padded vise and push them together. The existing tuner buttons will act as a depth stop so you don't push the button too far.

Important things to note

• Ensure that the "wings" on the shaft and the button are lined up, we don't need to put any more tension on this old plastic than necessary
• If the shaft is too cold then you'll see the button distend or see stress cracks forming
• If the shaft is too hot then you will see it melt and also distend 
• If your button goes on crooked, heat up the shaft again and you should be able to shift it by hand or by holding it a vise.

I flood the inside of the button with thin CA which reinforces the bond between the melted plastic and the brass and fills any gaps

And here is the finished product! The patina on the replacement brass shaft (top left) doesn't match the existing ones but they are functionally identical and I'd call that a rescued set of tuners!

I don't believe the tuner shafts could be brazed back together and remain strong but I hold onto the old parts anyways. Perhaps replicas could be cast 

Finally, if the plate had become bent from the earlier steps, simply place it in a padded vise and apply light pressure with your hand to coax it back into place. The metal is thin and pliable, so it is not hard to correct