Sharpening Old Taps And Dies

MozamPete

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I had some old second hand files and I tried the soaking in sulfuric acid (battery acid from the auto store) trick to sharpen them up on the weekend. Worked surprisingly well so I'm pretty happy with that.

Then I got to thinking (dangerous), I also have a lot of old taps and dies I have picked up over the year - imperial stuff I normally only use to tidy up existing old threads or cut the old one to match an existing part (anything I build from scratch would use metric threads and I have good sets of new taps and dies for those). Would soaking in acid sharpen those up to? Anyone see a reason not to give it a try?
 
It might sharpen them but it would also probably change the size, taps might cut undersize and dies oversize.
 
It would be interesting to see how it works on the different materials. The taps and dies could quite likely be high speed steel, whereas the files are more commonly carbon tool steel.

-frank
 
Somewhere out in cyberspace there is information from old greenfield T&D literature on sharpening taps & dies using a round stone. I cant find it now but I will keep looking. for example on the dies you take a round stone that fits in the circular hole and lightly grind/polish the leading edge.
 
Somewhere out in cyberspace there is information from old greenfield T&D literature on sharpening taps & dies using a round stone. I cant find it now but I will keep looking. for example on the dies you take a round stone that fits in the circular hole and lightly grind/polish the leading edge.

Hmm, I like the sound of that, use the small round stones that came with my die grinder maybe.
 
I don't think using acid to sharpen taps and dies is a good idea. The acid will attack the surfaces of the taps/dies, leaving a matte finish which will increase friction. Also, renewing the dulled edge will necessarily remove metal from the thread, creating a serious fit issue.

If I were going to try it, I would coat the entire tap or die with an acid resist and remove it from just the area I wanted to etch. Remove the resist with a solvent after etching.
 
Decent to excellent previously owned taps and dies are a dime a dozen if you look around for them. It is not worth messing with them beyond cleaning them up. Use the dull ones for HSS stock to make various tools or sell them to someone else for a dime a dozen, probably better than scrap pricing for the smaller ones.
 
While taps & dies can be had for a dime a dozen, as you go up in size that theory goes out the window, so yes it only makes sense to sharpen larger sizes. The reason that split dies are split is so you can micro adjust them either for the size of stock diameter or for the sharpening process . that's the reason that split dies are sloppy/ loose when installed in the holder, you simply adjust the screws on the die holder combined with the screw on the die to enlarge or reduce the diameter of the die and it still fit the die holder. I hope this helps to understand for the purpose of a split and screw on dies. As mrpete says is that clear as mud:boxed in:
 
Decent to excellent previously owned taps and dies are a dime a dozen if you look around for them
That is one of the advantages you have of living in a first world country - not so readily avalable over here.

Anyway the concensus seem to be it won't work, but I might dig out a few of the sizes I have multiples of and give it a try just for kicks. I wouldn't expect to remove enough material to make the size smaller to any meaningful degree, but I'll mic them before and after to check. All else fails, at least they will be clean if I try to practice grinding them to sharpen them up.
 
A tool and cutter grinder, surface grinder, milling machine, or lathe (in descending order of preference), can be used to sharpen taps and dies by using properly dressed wheels on the grinders or -Dremel/die grinder/tool post grinder/or whatever with similar shaped wheels- on the mill and lathe to do the grinding. All that is required is a setup that will accurately move the abrasive along where it is needed at controlled depths. Mills and lathes will of course need to be protected from the grit produced. I would only do that in a pinch, too easy and cheap to find a tap or die here.
 
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