cutting new threads on hub

Hey all, one of our club riders has a cheapo hub that has the end few threads of one spindle mashed together. (providing me another chance for a new tool)

I have used a tool to cut new threads in the past, looks like a little circle with cutters that you spin around and it rethreads it.

This is probably a tap or a die, but I don’t know for sure.

Anyways, does anybody know the specific info that I would need to purchase a tool for this purpose, like size of a hub spindle, and distance between threads, or anything like that?

Thanks

I’m not a machinist (yet?), but if you wanted to use a die you’d have to go too small, I think. Try using a triangular needle file to clean up the existing threads. That’s what I do with the threads on bolts that I have shortened. If this works you’re all set. It’s a cheaper solution, too.

Here’s a pic.

cleaning up  the threads (small).jpg

U-turn’s right, they are called die(s). Don’t buy one, as you’ll also need the specific tool meant to hold that specific die, and a die big enough to cut those kinds of threads will be really expensive new. Just go to a good machine shop and ask if they’ll re-cut those threads for you. That should be cheaper.

thanks guys

Out of interest are taps for drilling threads just as expensive, or are they a cheaper thing than a die?

Joe

There is a special file that is made to dress damaged threads, It has a different number of threads per inch on each side with four sides and some are different on each end for eight sets of threads per inch.

One of the reasons you use this file is that a triangular file has the wrong angle for the threads. However, it’s actually better to use a flat file to dress the ends, the technique is different.

Taps are more readily available and are usually a little cheaper than dies. For tapping blind holes (rather than through holes) you will ideally need a set of three taps with different profiles for each size of hole.

Price is heavily dependant on quality and the cheap sets are rarely worth the money. I tend to go for good quality used taps and dies (and other tools) rather than cheap new ones.

Dies require an accurately sized shaft. This is hard to do without a lathe. Taps requires an accurately sized hole, this can be done with a good set of drills.

HTH
Nick

Show it to the boys in the local bike shop, they might have the expensive thread cutter, I know the bike shop I worked at twenty years ago had one. carjug

It’s called a Thread Restoring File and retails for about $16. You should be able to order one through your LBS.

For dressing-up a “cheapo hub”, a triangular needle file, or perhaps another common needle file that has pointed edges and a lightly-curved surface, should suffice. Many people have a needle file set at home.

Heli-coils

If you are trying to repair interior threads a tap IS what you need. However, if the threads are completely torched you’ll have to go to a little thing they call the Heli-coil.

You can drill out the old threads and use the corresponding Heli-coil tap to set up your new hole to accept a tiny coil of new threads that you srew into place witha cool little tool.

Auto shops use these to REPLACE the threads on cylinderheads and main bearing bolt holes. You don’t have to go to a bigger bolt or pedal size because your threads and the hole are restored to there original size. A little loc-tite sets everything just fine.
Beener

Re: Heli-coils

The Helicoil thing is a pretty cool trick. The hub Sofa is talking about, though, has external threads and a retaining nut.