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Double Bass Endpin Socket Taper?

robobass

robobass

Aug 1, 2005
3,546
1,421
Cologne, Germany
www.basscapos.com
Disclosures
Private Inventor - Bass Capos
#1
I'm working on some socket prototypes, but can't seem to resolve the taper angle issue. I've got a bunch of sockets in the shop, and the tapers are all over the map. The standard taper for reamers seems to be 1:17. If that means that the diameter increases by one unit for every 17 units of length, then I calculate the angle from center line to cutting edge as 1.69°. That is more than any of my sockets, which range from 1.04° to 1.49°. Can anyone out there clue me in? Maybe my math is wrong.
 
#2
Your math is correct as far as I can tell however you might be better off buying a reamer and copying its taper. What they are spec'd at and what they are might vary slightly. When we set up our lathe to cut endpin tapers, we adjusted it much like you would a peg shaver. Make an adjustment to the tool, cut a socket, test it in a hole cut with your reamer, readjust the tool as necessary and repeat until it fits...
 
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#3
JoeyNaeger said:
Your math is correct as far as I can tell however you might be better off buying a reamer and copying its taper. What they are spec'd at and what they are might vary slightly. When we set up our lathe to cut endpin tapers, we adjusted it much like you would a peg shaver. Make an adjustment to the tool, cut a socket, test it in a hole cut with your reamer, readjust the tool as necessary and repeat until it fits...
Click to expand...

Joey,
Thanks for the info. I'm still unsatisfied, though. Even if the reamer doesn't exactly match it's specs, there is still a huge gap between that and the sockets I have as samples. Since I plan to create a socket which you might possibly want to buy, I would hope to carve a taper which fits properly on your instruments, without visiting you personally and measuring your reamer. That would be way too personal:rollno:
 
#4
Joey Naeger has good advice. There's a bit of variation between brands (herdim, Aenelt, Metropolitan) Because wood is the material used between mating surfaces in this case the taper doesn't necessarily have to match absolutely in order to give you an apparent tight fit. Wood will conform somewhat and also swell with the glue used in peghole bushings. But Rob - you know that is NOT the case with the tapers on machine tool toolholders. The fit has to be close to perfect there otherwise the tool could just pull right out.

Measure your reamer to roughly set up the machine, then make a tapered hole with the reamer. Then, as you make plugs adjust your machine to match the test hole taper.
 
#7
james condino said:
Good luck with that one Rob; it is a constant source of frustration for all of us. I'll be excited to see what your end product is!

j.
www.condino.com
www.kaybassrepair.com
Click to expand...

Jim,
Thanks for the support. As I get into this, I'm realizing how difficult it is to set the angle of the cross-feed on the lathe to the necessary accuracy, even if you have a very high quality protractor, which I do. I respect Joey's advice. However, I doubt that the variation between reamers is the real problem here. I'm just going to make a bunch of test holes with my neighbor's reamer, make samples, and set my machine accordingly. This is some crappy work!
 
#8
Rob, good luck with the project. I have two suggestions: 1) 10mm rod, which has become the standard, and 2) a squeezing device, rather than a screw to hold the rod at proper height. That way one could use different rods including carbon fiber without damaging the rod. I've been experimenting with titanium rods, and there is a surprising difference in sound between it and steel.
 
#9
robobass said:
Jim,
Thanks for the support. As I get into this, I'm realizing how difficult it is to set the angle of the cross-feed on the lathe to the necessary accuracy, even if you have a very high quality protractor, which I do. I respect Joey's advice. However, I doubt that the variation between reamers is the real problem here. I'm just going to make a bunch of test holes with my neighbor's reamer, make samples, and set my machine accordingly. This is some crappy work!
Click to expand...

I think you misunderstood me. The source of your problem is the extreme variation in endpin sockets. The reamers, whether they are a true 1:17 taper or not, are going to be much more consistent.
 
#13
I'm curious, are you planning to make the taper out of wood a composite or metal? I experimented with a wooden cello end pin with a carbon fiber extension I made the collet out of nylon, had a hard time getting it tight enough to keep it from slipping partly due to the small diameter and partly due to the natural lubricity of nylon. I suppose you could rib the taper to help resist the torque of tightening.

have fun
 
#15
I don't want to give too much away, but I'm going for a wood socket and a big delrin tightening ring. I don't want to get too mechanical with cam levers and such. Interesting, RC, about the nylon sockets not staying put. That makes sense. I had planned to stick with wood simply because it's wood. I don't like the idea of using plastic on a bass if not necessary, but then you get into the ecological issues of using hardwoods...
 
#17
robobass said:
I don't want to give too much away, but I'm going for a wood socket and a big delrin tightening ring. I don't want to get too mechanical with cam levers and such. Interesting, RC, about the nylon sockets not staying put. That makes sense. I had planned to stick with wood simply because it's wood. I don't like the idea of using plastic on a bass if not necessary, but then you get into the ecological issues of using hardwoods...
Click to expand...

Sounds like a great product. I would love to see a 10mm endpin that is compatible with different endpin rods.
 
#18
We made a run of bass endpins using delrin as the plug material and never had a problem with not having enough friction between the plug and the spruce block. I remember leaving the turned finish a little more coarse and also hitting it with rough sandpaper thinking that would help. But I'm not sure it makes much difference really if the fit is good. The nicer endpins that Shen supplies for example use what looks like nylon for the plug and those seem to work fine.

I'm sure Rob knows all this but one thing that has helped me when turning tapers on a lathe is to either turn between centers or use a nominal dimension on one side so that side can be held in a collet. That way you can remove the piece and check the fit without losing concentricity as you put it back in.

Another thing that helps me is to mark out two marks along the taper with an inch (or any set distance) between. Measure the diameters and subtract the difference. Even as you decrease in diameter overall this difference in diameters amounts to your taper, and you use that to adjust the the machine. Cosign error here but it doesn't matter as you're just using the figure for fitting purposes.

Using the compound rest is the toughest way to make fine adjustments for sure. Turning between centers is less finicky but I have a taper attachment for my Clausing 5900 lathe and that's the slickest way for me. I do have a small wood lathe but I still go back to metal lathe for this kind of thing.
 

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