Functional difference in thread pitch on tap and die

DMS General
#1

I’m looking into learning how to turn kitless pens, and in my deep dive on YouTube and message boards and everything else, the “celebs” are using tap and die sets that use a 0.8mm pitch on the threads.

In my searching, I’m finding plenty of 0.75mm and 1.0mm pitch; but for 0.8mm the choices are scarce and a significant price jump (the M13 set alone is $220 vs $35-40).

Am I going to notice a significant difference between 0.75 and 0.8? I don’t want to cheap out, but the difference will triple (at least) my budget.

Thanks in advance for any help you can give.

#2

I know nothing about this subject but my quick Googling revealed that the main difference in the “pro” tap and die sets isn’t the thread pitch but the fact that they are “triple start” threads rather than single start.

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#3

.8mm in 13 mm is an odd ball size.

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#4

Functional? No, mechanical properties of the two should be 99% identical.

If you try to use a 0.75mm nut with a 0.80mm thread then yes, it will bind or at the very least not turn smoothly.

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#5

Apparently the reason for using a three-start thread is that the pen will open and close with much less turning. A downside is that you have a two in three chance of your cap and body not lining up if you have a pattern to match on them.

Or something like that.

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#6

Don’t overthink it. a .8mm pitch is a 5mm bolt. should be easy to find a 5mm set.

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#7

In general terms finer thread pitches result in stronger threads, this is only true to a point and is ultimately pretty material specific.

If I were you I would try and steer clear of non-standard thread pitches. Standard thread pitches are very well optimized for machinability and strength in most materials.

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Also spending money on high quality taps and dies is worth every penny IMO.
McMaster is the easiest place to get know good high quality taps and dies.

If McMaster does not sell it, it is not worth using.

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#8

Keep in mind that some of these taps and dies sprung out of the pen-making community and are very specific to their application - not mainstream machine shop work.

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#9

This is the problem I’m having. :slight_smile:

So much of this is taking someone else’s process and trying to learn/adopt/adapt it, which I love - it’s kind of the “maker way”. During some deep dive researching on everything, it looks like people would have custom taps and dies manufactured and have group buys for these; so I think I’m fortunate in the fact that there are at least a few places that sell these (formerly) custom pieces at any price.

There’s a lot of great info in this thread, and I appreciate everyone chiming in with their thoughts. Now I need to incorporate it into my other notes and figure out if I want to just bite the bullet and go with the same tools they use or get a little more adventurous and see if I can adapt the process for tools that are less niche and obscure.

#10

I assume that’s is brass your going to be tapping?

Have you been cleared on the Machine Shop lathe & milling machines? You could single point thread some tool steel, then add the flutes on the milling machine. Obviously you would need to turn a taper to make it a tapered starting tap.

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#11

Right now my main focus is tapping acrylic - but I’m also going to try and get signed off in the Machine Shop so I can make my own mandrels for turning the bodies and the caps; if I can work up the experience to make those, then brass sections and such would be a cool addition to my process.