Double Bass fitting Rubner tuning machines

[levi kn]

Hello,

Can someone explain me how to fit tuning machines with conical ebony pegs?
The tuning machines look like this:
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The peg measures 18,5mm (+- 3/4 inch) at the base and 17mm (+- 0.67 inch) at the tip.
It tapers very little.
I also contacted the manufacturer (Rubner) and this is what they respond :

Hello Levi,

you´re right you need a special reamer for the holes in the headstock. Unfortunately we do not manafacture such reamers.

Some time ago a customer of us from America had the same problem. So we contacted a company which is able to manafacture such an reamer. We can do this for you, but its expensive. You have to order two reamers and the price for one is 290,00€/ without taxes.

I can't afford buying two reamers that expensive!!

I'm a luthier but not really familiar with double basses.
With the right tools i can handle this task.

Can someone give me helpfull tips???

Thanks,
Levi.

 

[Huy Nguyen]

I suggest you buddy up with a Double Bass luthier and maybe ask him to use his tools in his shop in exchange for something else. Those big reamers are not cheap. I never seen one for less than $300 US.

I wouldn't use a substitute either... it's just asking for trouble.

 

[1st Bass]

The other possibility is to buy a straight 3/4" diameter reamer, made for cutting steel, from a machine tool supplier, and then carefully hone off the .5-to 2mm taper to get the size you need. The flutes are deep enough to allow that, and you could get exactly what you wanted.

If you are not sure how to do all that, talk to a machine shop, and explain what you need. I am quite sure that such a tool can be had fairly cheaply, and then modified the way I described, for not too much labor cost.

 

[uprightben]

If the process is the same as for violins, and I think it is, it can't really be done without the reamer and a matching "sharpener" to true up the pegs, at least it can't be done well. What type of luthier are you? If you want to get into working on db, the reamer is a good investment as it is used to make/fix the endpin socket, really no shop that works on these instruments should be without one. If you are determined to install hatpeg tuners with out buying or borrowing a reamer you could turn some straight pegs. The way these reamers were made before factories and such was to make the sharpener, and then use it to make a wooden cone. Then you put in a groove, or a flute, and you put a metal cutter (like the blade in a power planer) in the flute and voila! you're in business.

 

[pand]

I used
* a common (cylindric) drill
* a round file to make the conical shape of the holes

I dipped the peg (with attached brass plate and cog wheel) into carbon powder and marked where to file.
Each time the peg goes further and further into its hole.
Finally the brass plate will be in contact with the pegbox. Ready!

Attention: The brass plate (= the cog wheel) has to be 100% parallel to the outside plane of the pegbox.

This worked very well - I'm 100% satisfied with my machines.

Cost: € 3.50

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