# 3 Start Threading my way



## skiprat (Nov 23, 2008)

As the tap and die topic is doing the rounds again, I thought I would re-share how I do it. I have a metal lathe but at the time had no real idea how to cut three start threads. I got all my answers right here on IAP.

I do think that before anyone goes down the route of either making or buying their own threading tools, they should decide before hand what it is exactly that you want to achieve in the end. 

Once I understood what was told to me about cutting external 3 start threads, I decided that the threads I would make would be of no particular size and would not match any existing thread on available pen kits.
My reason was that making threads was a big enough learning curve without having to match them to someone elses as well.

First I took a Stainless Steel shaft and turned it to approx 11mm. The shaft was about 330mm long. I cut the 3 threads on the shaft. For about 3/4 of its length.
Next I cut about 3 inches from the threads and this was going to be a tap. I turned half of the threads off of this piece on one end and slightly tapered the other end. I just eyeballed this taper and I guess it takes up the first 4-5 threads.
Milling the flutes was a bit of a mission. I don't have a milling machine so had to do horizontal milling. I did ensure that I ended up with a slight positive rake. 

Of course Stainless Steel is hardly the correct material to make a tap, but I knew I would never be tapping anything harder that plastic or wood, so I'm happy with it. I have a small diamond pocket stone that re-hones the edges when needed.

The remaining thread from the rod is simply cut off as required. I just drill ( and sometimes tap ) a hole down the middle before parting off the piece I want. I will just repeat the whole saga when the rod is used up.

In the pic below you can see the rod, the tap and a piece of thread that was used on the blue pen. The cap on the blue pen is thick enough to support the internal threads. On the other pen, a copper band re-inforces them.

I hope this can help someone


----------



## LEAP (Nov 23, 2008)

Now that is a unique approach. Thanks for sharing.


----------



## BRobbins629 (Nov 23, 2008)

Well done Skip - so are you quoting for the the next group buy?


----------



## Skye (Nov 23, 2008)

I still love that blue pen. Hard to believe what it's made from.


----------



## Daniel (Nov 23, 2008)

Nice solution on the threads. the tap looks really good. If your post was not all about how you made it I would not have noticed is was not store bought. I am glad you mentioned the positive rake when you milled the flutes. I noticed that there is just a slight rake to the tap I have been looking at all morning.


----------



## skiprat (Nov 23, 2008)

LOL Bruce, group buy?? Me???Never. I could sell you some nuts and bolts though:biggrin:
I just found another old pic of the copper one that shows the internal threads in the cap. You can see how the copper ring supports the threads too. The colours of the PR make the threads look chipped, but they're not, I promise


----------



## holmqer (Nov 25, 2008)

excellent job of making your own tooling!


----------



## Paul in OKC (Nov 25, 2008)

There ya go!


----------



## VisExp (Nov 27, 2008)

skiprat said:


> First I took a Stainless Steel shaft and turned it to approx 11mm. The shaft was about 330mm long. I cut the 3 threads on the shaft. For about 3/4 of its length.


 
Steven, thanks for the info.  I was wondering how you cut the 3 threads on the shaft.  Did you use your metal lathe?


----------



## jhs494 (Nov 30, 2008)

Excellent work as always! 
Thanks for sharing your ideas with all of us!


----------



## Ligget (Dec 2, 2008)

Great ideas there Steve, thanks for sharing, I need to try making threads some day. I certainly agree about making your own thread size instead of matching them to a specific size.


----------



## bitshird (Dec 3, 2008)

Now I gotta write a program to cut three lead screws, I've got a bunch of A2 round stock, access to a Haas CNC Lathe and and electric furnace. 
 Steven, there was some discussion about the rake on the teeth of the tap & die from the group buy, the previous one. the thing was that these tools were made for cutting metal, and left a pretty rough surface on wood and plastics. It made no until I started thinking that if the Tap or Die if cut correctly the crest and valley will have a flatted surface unless it's ISO then  it still has a flatted crest and a radius on the valley or the crest if it's internal.
 But by cutting with the teeth left at a sharp point on the crest and valley, and the DIE made with the original turned tap, they should be sharp enough to cut wood or PR  smoothly, Now to figure out the indexing, if I mount a small lathe chuck to my Taig Mill table, I think I can pull up a thread milling program, and not even have to go to the school except to harden it, and for cutting  wood and plastic A2 should do fine as is, but alas and alack I don't have any thread mills any way, besides I realy don't have that kind of time right now, Why you do dat Mon, I thought youz wuz a nice guy :beat-up::beat-up::beat-up::beat-up: you realise your costing me about 5 or 6 hrs of turning time don't you :bulgy-eyes: :bulgy-eyes: :bulgy-eyes:


----------



## bobkeyes (Dec 10, 2008)

The other way to cut them is with a mill and a thread milling tool. Quick, accurate, and easy.


----------

