Trying to understand taps and dies better

[thewishman]

Looking at 10mm taps, options are for:
10 x .5
10 x .75
10 x 1
10 x 1.25
10 x 1.5

I see from the chart that the second number is pitch, and I understand how to select the right drill bit. My questions are, what difference does the pitch make, and which pitch is best for most pen parts?

 

[mredburn]

.75 the .5 is very fine and take a lot of turns to take apart and put back together. It can cross thread easily also. The 1 pitch is ok for certain items where you have a lot of material between inside and outside threads. How ever there is more stress on the parts as you cut the threads. I use the m10 x.5 on certain parts where Im using 12mm outer threads and 10mm inside threads or m10 outside and 8.4 inside. My go to pitch for almost all parts I make is .75 All though I do have them all, the 1.25 and 1.5 from a craftsman metric set. The rest from Victor machiery. THe costs from Victor or almost any of the suppliers is very small considering. I also have bottom taps for the .5 and .75

 

[rherrell]

Maybe this will help...the PITCH is HOW FAR the threaded part will MOVE in ONE REVOLUTION. A .5 pitch will move the part .5mm per revolution, a 1.5 pitch will move the part 1.5mm per revolution....make sense?:biggrin:

 

[Joe S.]

I need metric taps, they make a lot more sense!

 

[cnirenberg]

Chris,
Here is my take. Use what works for you and what you like. WhenI began to thread my own pieces I missed out on the first group buy, so I naturally went out and got whatever worked. I used 1/2x 20 TPI for my caps. That is 20 threads per inch. I liked it but wanted a finer thread. Being impulsive and impatient I bought a 1/2x36 T&D set. I should have gone with the 1/2x32 but they were out of stock. The 1/2x36 thread is fine, and it crossed on me a few times depending on the material I used and other things. I kept a log of what workd and what didn't. You need to take into account the material you want to thread also. I like the 0.75 threads, but mostly still use my old M10x1.

 

[randyrls]

Looking at 10mm taps, options are for:
10 x .5
10 x .75
10 x 1
10 x 1.25
10 x 1.5

I see from the chart that the second number is pitch, and I understand how to select the right drill bit. My questions are, what difference does the pitch make, and which pitch is best for most pen parts?

Chris; I cannot answer the second question, but the pitch does make a difference in the drill size.

The standard method is to subtract the pitch from the size to get the proper drill bit for the inside thread
ie for 10 x 1.5::: 10mm - 1.5mm = 8.5mm

to size an outside thread, add the pitch to the size.
ie 10 x 1.5::: 10mm + 1.5mm = 11.5mm

Added Later; I didn't get that you do know how to size the parts.

 

[dbledsoe]

(to size an outside thread, add the pitch to the size.
ie 10 x 1.5::: 10mm + 1.5mm = 11.5mm)

That sounds strange to me. Not saying you are wrong, but it sounds wrong. When I do a 12mm x.75, I have been turning the material to 12 mm and then threading. Is that wrong?

 

[joefyffe]

Looking at 10mm taps, options are for:
10 x .5
10 x .75
10 x 1
10 x 1.25
10 x 1.5

I see from the chart that the second number is pitch, and I understand how to select the right drill bit. My questions are, what difference does the pitch make, and which pitch is best for most pen parts?

Chris; I cannot answer the second question, but the pitch does make a difference in the drill size.

The standard method is to subtract the pitch from the size to get the proper drill bit for the inside thread
ie for 10 x 1.5::: 10mm - 1.5mm = 8.5mm

to size an outside thread, add the pitch to the size.
ie 10 x 1.5::: 10mm + 1.5mm = 11.5mm

Added Later; I didn't get that you do know how to size the parts.

Randy: I fear I may be missing something here. Are you saying, regarding outside threads, that if you were using a 10 x 1.5 die, you would cut your tenon 11.5 ?

 

[mredburn]

I cut my outside diameter about 0.2mm smaller than the stated size, a 10mm will be cut 9.8mm for external threads. The dies you buy will not cut 100 % thread depth. The cutting action can push material ahead of the cutters and this allows some room for it. You do not add the pitch to the outside diameter of the material for external threads. I also bore my pilot hole slightly larger than the stated diameter of "diameter -pitch" in this case 10mm-.75 =9.25 but tend to drill it 9.4. In most cases your only working with 75% of the stated sizes anyway.

 

[BSea]

to size an outside thread, add the pitch to the size.
ie 10 x 1.5::: 10mm + 1.5mm = 11.5mm

to size an outside thread, add the pitch to the size.
ie 10 x 1.5::: 10mm + 1.5mm = 11.5mm)

That sounds strange to me. Not saying you are wrong, but it sounds wrong. When I do a 12mm x.75, I have been turning the material to 12 mm and then threading. Is that wrong?

That sounds strange to me too. I agree with mredburn. I cut my tenons slightly smaller than the die.

Back to the original Question: I also agree that with most optional threading, I go with .75mm. Mainly because I know PR can handle the stress without breaking (usually). I may buy a few 1mm pitched dies for using with alumilite & other more easily threaded materials. Especially for cap threads. I have 1 triple start tap & die set, and I doubt I'll get another, but there are some pens that I want to make that will use a different size, so I'll pass on buying the triple start for the other size. At least at 1st.

 

[joefyffe]

I cut my outside diameter about 0.2mm smaller than the stated size, a 10mm will be cut 9.8mm for external threads. The dies you buy will not cut 100 % thread depth. The cutting action can push material ahead of the cutters and this allows some room for it. You do not add the pitch to the outside diameter of the material for external threads. I also bore my pilot hole slightly larger than the stated diameter of "diameter -pitch" in this case 10mm-.75 =9.25 but tend to drill it 9.4. In most cases your only working with 75% of the stated sizes anyway.

That's what I was looking for, Mike! I was just thinking, if you go a mil and a half over, you is gonna be twistin off a lot of PR tenons! :at-wits-end:

 

[thewishman]

Thank you, gentlemen! I was threading a lot in the last few weeks and have gone through a great deal more material than I should have. You have clarified my understanding greatly.

 

[rherrell]

Depending on the material the rule of thumb for outside threads is to make the tenon 2% less than the nominal size. Mike is exactly right, 9.8mm is 2% less than 10mm.
However, with soft materials you can go 1% and with steel I go about 5%.

When I thread my toolrests with 1/2-20 threads I make the tenon .475" which is 5% less than 1/2". The TYPE of thread matters too, the finer the thread the more material you need to remove, sounds backwards I know but it works.