# Making a Tap



## Antman (Feb 25, 2010)

Hi,
  No engines yet nor even plans to make one. I am still busy learning the basics, and using the experience gained making tooling and mods for my very basic lathe and shaper. I want to bolt 2 components together using a differential screw. I thought I might be able to do it with a M8/M10 screw but that will only work if one component is initially free to turn with respect to the other. I think what I need is that the thread with the larger diameter should have a finer pitch than the smaller diameter. To which end I want to make a screw that is M8/M10x1mm. Pretty basic. Then I will need a tap of 10mmx1mm. A standard metric fine 10mm thread has a pitch of 1.25mm, same as M8, so no go. I have found a source for silver steel. Will it be feasible to make such a tap? The only information I have about hardening and tempering silver steel is from an article about D-Bits in Model Engineer No. 3555, free download from their site. I will be tapping into hot rolled plate. 
 Thanks,
  Ant


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## Mainer (Feb 25, 2010)

Check out http://www.victornet.com/subdepartments/Metric-Taps/1310.html

They have all kinds of weird and wonderful tap sizes.

Or, you could make it. Given a chance though, I think I'd buy one.


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## Maryak (Feb 26, 2010)

Ant,

I only found this myself yesterday, but M10x1mm is a standard SAE spark plug tap.

Hope this helps.

Best Regards
Bob


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## Twmaster (Feb 26, 2010)

I'd like to hear how to actually make a tap. If this thread is not appropriate perhaps a new 'how-to' thread could be started.


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## ianjkirby (Feb 26, 2010)

Hi Ant,
 On this page http://www.engineeringtoolbox.com/metric-threads-d_777.html I found that they list 8 x 0.75 and 10 x 0.75 as standard metric fine threads. If you want two different sizes with the same pitch, this seems that it would do the trick, if I understand you correctly.
 As I live in Australia, I cannot suggest how you might actually purchase such taps/dies, but if you talk with a good engineering supplier, and show them a printout of the above page, you might get somewhere!
Regards, Ian.


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## Mainer (Feb 26, 2010)

As far as making a tap....I've made a couple that more or less worked in brass and aluminum. I'm not sure I ever tried one of them in steel. But here's what I did.

Get a piece of appropriate diameter drill rod of tap-length length. Turn a lead-in taper on one end and mill 4 flats on the other. Now comes the Great Debate on whether to mill the flutes first or cut the thread first. If you cut the thread first you don't have an interrupted cut, but if you cut the flutes first you don't raise burrs on the cutting edges. Your choice.

For the flutes, set up in a dividing head or similar, and with an end mill that (ideally) has a small radius on the tips of the flutes, mill as many flutes in the tap as seems reasonable for the diameter. If the remaining lands are fairly narrow the tap will turn more easily. You need a bit of a rake on the front of the teeth, and you can achieve this by milling the flutes "in front of" the tap's center axis.

Cut the thread (if you didn't do it first). Harden the tap by heating and quenching (quench vertically), temper in the kitchen oven at maybe 350F for an hour or so. Ideally, the cutting edges should now be ground to sharpen them. For aluminum and 360 brass, I managed okay by using "Keep-Bryte Anti-Scale Compound" during the heat-treat process, which preserved the as-milled edges sufficiently to work.

It's a lot easier to buy one!


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## Antman (Feb 27, 2010)

Thanks, Mainer, Bob, Ian and Mike
  I had no idea that a 10mmx1mm tap was commercially available. First, I will try to find one locally. Maybe M10x1 is something Somta makes.

http://www.somta.co.za/index.htm

 I would go for it and maybe put together an order from Victor for $100 if I lived in USA, but from where I am, what with bank and government foreign exchange charges, shipping, insurance, customs and then local sales tax I would end up paying over $200 which is a lot of thin flat ZARtjies. Oh well, life is tough on the border.  I get pleasure from my new hobby, making things, having hare-brained ideas, and I reckon the thread cutting, tapering and fluting of a tap that size is within my present capabilities. I believe I would taper the blank first, flute it in my shaper and then thread cut. I dont know about the heat treatment and what comes after. The tap doesnt have to be perfect and if it stands up to a dozen threaded holes that I can cut a screw to fit, Id be more than happy with what I achieved.
  Ant


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## Mainer (Feb 27, 2010)

I just checked your profile. I didn't realize you lived in South Africa! 

I wouldn't be surprised if the tap you want is available from Somta. An inquiry would certainly not be out of place.


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## Xlmyford (Feb 27, 2010)

Hello.
Some usefull downloads,almost any known thread:

http://www.gewinde-normen.de/en/index.html

This one is all about metric fine threads.

http://www.gewinde-normen.de/en/iso-fine-thread.html

Cheers,Ralph


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