tap + die folks -- threading issues?

[jjudge]

Anyone else practicing with the taps/die?
Post some observations, lessons learned on this please.

...

Richard Kleinhenz and I are chatting. It makes sense to post it here.

Summary of our email thread
The taps/die we ordered appear to be aimed at cutting metal.
That is, they have a positive rake - where plastic (ductile materials) should have a neutral or slightly negative rake.

This issue is similar to drills/drill bits.
See www.google.com/books title = "Metal Cutting Theory and Practice" and search for positive rake, ductile, etc.

Richard said:
- aluminum (6061) threaded and looked OK.
- water + soap helps lubricate
- e-taps can make 0-rake taps/die on request ("for plastic or soft aluminum"
- taps seem more forgiving
- suggest not to try brittle materials (e.g., inlace acrylester I'd planned to try)
- Metal / Mokume worked well
- in plastic, back-off and clear/break chips often (e.g., after every 1/3 turn)
- Epoxy cuts OK (e.g., cat blank from ed4copies)


I suggested corian (glues up well, is hard, should thread OK).

Notice Richard is working hard, and I only had 1 suggestion

-- joe

 

[Chuck Key]

Originally posted by jjudge



Notice Richard is working hard, and I only had 1 suggestion

-- joe

Here is a link to Richard's hard work.

 

[scubaman]

Here's a better link to what I've been doing which allows navigating.

I'd like to see what people are doing with these tools. I did try an acrylester blank from Ryan at woodturningz, and it actually worked. OTOH the mokume M3 cut OK but the material strength of that stuff is low, the threads always sheared off! On a solid blank, the male thread cut nicely and cleanly with the die. The female thread cut well in a drilled hole using hte tap. But if I had a female thread inside already (M10x1) the piece sheared off very easily. I do not think it is a candidate - even if single-point cut I suspect it's break in use very quickly.

I found it not easy to get a reasonably shaped thread. You have to back out to break chips veyr often! 1/4 turn, back off, etc. Is there a trick to cutting well-shaped male threads? Oil lubing helped, soap and water worked at least as good.

I prepared some corian but did not get a chance to try it before leaving for a business trip.

 

[Texatdurango]

What diameter are ya'll turning the blank to before using the die to cut the male threads? And what size are you drilling the hole for tapping the cap? I'm curious to see if I guessed at the right or close enough size.

You can add Truestone to the list of materials that thread well, I've made several and they turn out nice.

 

[scubaman]

Originally posted by Texatdurango

What diameter are ya'll turning the blank to before using the die to cut the male threads? And what size are you drilling the hole for tapping the cap? I'm curious to see if I guessed at the right or close enough size.

You can add Truestone to the list of materials that thread well, I've made several and they turn out nice.

I drill with 7/16 for femal cap thread. For the main body, I drill with letter T for an M12x1 thread, and turn to .472".

For the main body, I always tap the internal thread first. While the OD is still large.

Are there tricks to polishing threads? I find that sometimes the threads look rough, 'white' really. A polishing wheel does not seem to do a good job to get in there and clean up completely though I expected that.

George, I know you're making sections also. Are you gluing in the nib cartriges, or tapping the inside? I've been using Schmidt cartridges which use an M6.5x0.5 tap which I have. Some learning involved also in cutting fine internal threads...

 

[BRobbins629]

Another material that these work well on is ebonite. I have even used this as a core for a wooden pen, drilling a 1/2 hole in the wood, gluing in a 1/2" diameter piece of ebonite and drilling a 7/16" hole(for the cap) in the center of the ebonite to tap. This essentially leaves an ebonite tube for support 1/32" thick. I do something similar for the bottom section. PR should work equally as well. I chase the male threads several times with the die, trying to start in different positions.

What amazes me the most is how light these pens are.

 

[Texatdurango]

Originally posted by scubaman


...Are there tricks to polishing threads?...

...George, I know you're making sections also. Are you gluing in the nib cartriges, or tapping the inside? I've been using Schmidt cartridges which use an M6.5x0.5 tap which I have...

I don't know about tricks but I found something that works well for me. I use a spray can of Canola cooking oil and lightly spray the area before threading and the difference between white chalky looking threads and nice clean shiny threads is amazing. Look how shiny and clean the threads are in the truestone below, that's how they looked right after using the die! And speaking of truestone the threads cut nicely, even with the metal veins running through the threads.

Yes, I am making my own sections, some I make as one piece including the threads, some I use brass inserts, depending on which nib and feed I am using. In the photo below, the feed housing still screws into the brass insert but for the times I make the entire front section from plastic, I do not thread the feed housing (A), I just turn the housing smooth and add a drop of CA to hold housing (A) into jacket (B). The feed and nib still are able to come out for replacement. I do not use the Schmidt front sections because the ones sent me do not allow the nibs themselves to be removed for replacement, it's the whole front section or nothing leaving the customer no room for upgrading nibs later on.

 

[scubaman]

A couple of quick comments while I have net access:

I'll try the cooking oil. Did you try any other oils? I have used tapping lubricant, it helps.

I'm concerned about material strength with the 'metal' veins. Some of these smear when you polish and aren't careful, I suspect they are a different, soft material. I don't think the threads themselves, the cusps, but the material below.

I've made cumberland (hard rubber) - worked well.

I've used these cat-blanks from ed4copies. They worked oK. I suspect they are an epoxy maybe. Unfortunately, a few days later, they had distorted anisotropically - they are no longer round! Of course I can chase the threads which might fix it (for a while?), but I am surprised and unhappy...

 

[Texatdurango]

Richard, I tried tapping fluid, cutting oil, 3 in 1 oil and WD-40 and none worked as well as the spray cooking oil. Who knows, perhaps there is something in the mixture that gives the plastic a nice shine! All I know is that I ni longer have those powdery white threads.

As far as the truestone goes, I realize the veins aren't metal, I just use that term to describe the different colored veins. That pen is long gone but I stay in contact with the owner who says he uses it frequently. I'll have to check back with him now and then to see how the threads are holding out.

 

[Paul Downes]

crisco might also work. We used it sometimes as diemakers on certain materials. I haven't checked but I wonder if acme thread taps and dies are out there. they would provide a stronger thread in fragile materials. You can oversize the tap drill size and still get adequate threads with less chance of breaking the material. You can also open up a split die and shallow cut the threads and then re-cut them full depth to be more gentle with something like acrylester.

 

[scubaman]

Originally posted by Paul Downes

crisco might also work.

I hope this is not brand-dependent I tried Mazola spray and had problems!

Seriously now. I did try Mazola spray, because I found it in the kitchen. I needed to make a replacement cap, the male thread was previously cut with the die on neutral. The previous cap was threaded using the tap, and probably tapping oil. The old threads worked very well. So I drilled 7/16, and I used the Mazola spay as lubricant on the tap, and in the hole. The threads look really nice. But... they are too tight! I ran the tap in a few more times, there is no debris in the threads, maybe a little remaining Mazola though I tried to wipe that out. I'm a little surprised, and don't know how to fix it, other than compressing the die a little and chasing the male thread.

What's your experience with fit? I've cut a number of the M12x0.8 threads, matching male threads using the die with the set screw just touching i.e. the die fully relaxed, uncompressed. I have not had an issue like this...

 

[BRobbins629]

Rich - I have 2 pens made from the same material (Ebonite) and one definitely threads easier than the other. One thought I had is that maybe its not the threads that are different but the clearance between the section below the cap threads and its mating section on the bottom. I bore my cap out below the threads to .500 on the metal lathe and think there may be some play in the holder such that the bore is tapered. The mating section is .498 on mine, so there's not a lot of room for error. Just another idea to check out.

 

[scubaman]

Originally posted by jjudge
Richard said:
- water + soap helps lubricate

Just a word of warning. Machinist friends suggested soap (dish detergent) and water for all plastics. Unless you're a clean-freak that completely oils a machine after every use I would not really suggest that stuff... DAMHIK! You might find rust on your beautiful lathe, and you might find your tap and die prematurely rusty! I caught it in time but... not for me!

 

[Paul in OKC]

I remember one thing around the first shop I worked in was plain old lard. Didn't do any plastics, but it worked great on some metal. I have heard of the soap and water trick as well.