Tips for tapping threads?

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docboy52

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Apr 6, 2014
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Hi again,

Apologies if this has been asked a thousand times, and for posting so much lately - but as I continue my journey into kitless pen making, I find I am continually hitting stumbling blocks.

I’m having trouble cutting nice, clean threads on the outer tenon of the pen body.

I am using an M10x1 triple start die, as well as a die holder setup from Hinze. I am on a wood lathe,as a metal lathe is not quite in my budget at the moment, and I’m doing the following:

1) I turn down the tenon to be 13.0mm which I double and triple check with digital calipers.

2) I cut a slight relief at the back of the tenon.

3) I am using BLO as a lubricant and keeping everything well lubricated as I cut the threads.

4) I’m taking it nice and slow, doing a few rotations forward, then a slight rotation back to clear the threads.

With that procedure, I am getting results that look like the attached images. That is to say, messy-looking, barely there, gnarled looking threads.

Now... since then, I’ve started to do the following:

- Turning down to slightly below 13mm (about 12.8mm)
- Cutting a slight bevel at the front of the tenon to make starting the cut a little easier

These two things have noticeably “helped”, but I still am not super happy with the threads I am getting.

As far as I can tell, I am doing the same things as what I’ve watched a few guys on YouTube do, but just not getting nearly as good of results. Could it be I just got a bum die? Or do I need to be backing out of my cut completely to clear out every trace of “ribbon” before progressing with my cut? The matching tap cuts inner threads really well. It’s just the outer threads that are giving me problems. Any suggestions on what I could be doing better?

Thanks so much in advance!

B855EF0B-A621-42CA-81AC-07F302E81016.jpeg
95E7B7F4-2164-4EC9-A70D-6CB55D24FF14.jpeg
 
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Penchant 4

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"... doing a few rotations forward, then a slight rotation back to clear the threads." MIGHT be a part of the problem. Try half a rotation and then back off. Yes, it will be slower; but may help. A thicker lubricant might help...try cooking oil. Check the die to be sure the cutting surfaces are in good condition?

Good luck!
 

Jans husband

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It certainly looks like the tenon next to the shoulder is much bigger than at the start of the thread.
I"m no expert-as my previous posts on taps and dies show, but the tenon needs to be the same diameter as the outside diameter of the die, in your case 10mm, with a short chamfer at the end just to get things going. I had to experiment with tapping a lot of spare blank ends before wasting a full blank.

I use WD40 as a lubricant.

My current problem with kitless threads is more to do with the internal thread of the section! Just can't seem to get that right. The videos make it look so easy!

Best of luck
Mike
 

BigShed

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Feb 14, 2008
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Adelaide, SA, Australia.
I did a tutorial on threading some time ago for the IAP library but couldn't find it in there, the search function doesn't find it no matter which words from the title I put in so I have attached it here.

Maybe it has just disappeared in the mists of time!

Anyway, maybe there are some tips in there that will help you.
 

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More4dan

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Katy, TX
A couple of additional points from reviewing your pictures:

The tendon appears too large before threading and the die has sheared off the material. Do some test sizes on scrap.

The finish on the tendon before threading matters too. I will sand and polish before threading. It helps some.

The most important thing is the type of material you’re threading. Again practice with some scraps.

I get better results running the thread to the end in one pass without backing up. Breaking chips with metal is sometimes required, it shouldn’t be with plastic. Again test for your tools and materials.

Check the direction of your die and make sure the tapered section is facing the blank. Then reverse it after threading and run it again to ensure the threads are cut to the end.

I have found this site to be extremely helpful in picking threads and dimensions of tendons and drill sizes.



Danny

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Last edited:

monophoto

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Saratoga Springs, NY
Danny has identified the critical points:

The tendon appears too large before threading and the die has sheared off the material. Do some test sizes on scrap.

- - -

Check the direction of your die and make sure the tapered section is facing the blank. Then reverse it after threading and run it again to ensure the threads are cut to the end.
The overall diameter of an M10x1 thread is 10mm. Starting with a tenon that is larger than 10mm means that you are trying to remove more material with the die than it is designed to handle. The starting diameter of the tenon should be close to the intended final diameter of the thread, or in this instance, 10mm.

Also, dies are designed to produce a slightly tapered thread, which is what you want when threading metal in a machining application. But for pens made of fragile plastic, you need threads that are uniform from one end to the other. Hence, the recommendation to initially thread the tenon with the tapered side of the die facing the tenon, and then reverse the die and run it back over the threads to even them out.

And I think his suggestion of doing some practice threads sounds like advice based on much practical experience.
 

duncsuss

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Please show a photo of the face of the die (the face with the etched size information) and either a photo or link to the die holder you're using.
 

jalbert

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Louisville, KY
2) I cut a slight relief at the back of the tenon.
While not directly related to your question, I would strongly advise not doing this. A thread relief is unnecessary, and creates a weak point, as you have internal threads for the section running on the inside, and tolerances in that area are generally pretty tight. It also lends itself to poor aesthetics and flow between the section and barrel.
 

docboy52

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There are a ton of helpful tips here for me to try out. I'm excited to give it another go with some of these tips in mind.

Pertaining to my original post, I made a mistake. It is not an M10 x 1 die. It is M13x.8. I apologize for the confusion. But, hopefully that clarifies things a bit.

I am going to give it another go tonight, and will let you guys know how it turns out!
 

darrin1200

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Mar 17, 2010
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If that is a triple start tap, one trick I have found is to run the tap and die three times, Turn it to a new thread start each time. I find that this helps to get a more consistent thread feel.
 
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