# Taps/dies/drill bits?



## keithbyrd (Nov 21, 2018)

I was in on a recent (last year) tap and die group buy.  Just now getting around to trying to figure out how to use them!  Was hoping to produce at least one working pen over the holiday weekend!
I have searched the library and found several articles - they are all using the M12, M10 etc and I have M13, 11, 9 etc
The question I have is how do I determine which drill bit to use with various taps? I have also Googled this and can't find the answers - the charts I found don't even have these sizes on them!  
I don't mind some trial and error  along the way but I would like to eliminate the errors from using wrong bits!  
Thank you in advance for your help!
Any help in guiding me to know which bits etc to use is greatly appreciated!
I have dies:
M13x .8
M11x .8
M9x 0.75

Taps:
M13 x0.8 GD-4
M13 x0.8 GD-5 (what is difference between GD-4 and 5?)
M13-.8
M11-.8
M7.9-.6 D4
M6.4x0.6
M6.5-.5


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## Nikitas (Nov 21, 2018)

I believe its the fit of the thread. For metric. Like a 3A vs a 3B fit in American threads.


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## keithbyrd (Nov 21, 2018)

Nikitas said:


> I believe its the fit of the thread. For metric. Like a 3A vs a 3B fit in American threads.



Brian - are you answering the GD4 vs 5 question?


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## Ed McDonnell (Nov 21, 2018)

There is a chart in the library reference section that will show you drill sizes for different taps.  I generally shoot for 75% thread.  With metric you can subtract the pitch from the size and convert to decimal.  Pick the closest letter, number, imperial or metric drill bit.  Or just use the chart.

I've seen GD# specified as thread limit.  I don't know what that means but have always assumed, like Brian, that it is a class of fit.  Maybe get one of the international members to pull out a metric engineering / machinery handbook and  explain it to us.

Ed


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## chrisk (Nov 22, 2018)

The letters Keith asked for seemingly are related to the Triple Lead for, on my M13X0.8 taps, they read as follows: "GD-5 TRIPLE LD"




IMHO, the conversion chart in the Library is of little use for kitless pen makers. I uploaded a pdf file with more precise data, extracted from Mitutoyo "Engineers' Reference Book". (I only scanned the pages of interest for the kitless penmakers).


Now I understand it's a bit awkward for a US kitless penmaker who, on the one hand, works with metric taps and dies and, on the other hand, has to find the fractional/decimal drill bit equivalent. 

I myself purchase all of my drill bits and precision tools from these guys: https://www.dehaye.be/en/home


Recently they even created a webshop; it is not complete yet but they are working hard to upload about 540 pages of their catalogue. Meanwhile, one can contact them by email.


If there is an interest, I can ask them to apply a rebate for IAP members as they do for me (-20 to -25% for drill bits). For example, for the M9x0.75 section to body tap, they have a HSS drill bit Ø8,25mm for 3,79€ or $US4,32 (retail).


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## chrisk (Nov 22, 2018)

Now for the drill bits on hand for you in the US, if one reads the conversion chart I uploaded, he can find the appropriate or close drill bit for:
M9x0.75 (ideally 8.25mm): drill bit 21/64 (= Ø8.334mm)

M11X0,8 (ideally 10.2mm): drill bit Y (= Ø10.262mm)
M13x0.8 (ideally 12.2mm): drill bit 31/64 (= Ø12.303mm)


For the materials we use (especially PE resin...) it is better to drill larger than narrower. Some colleagues (mredburn, skiprat) even advise to add up to 0.2mm (0.008") to the ideally adequate drill bit. For example, a hole up to Ø10,4mm (instead of 10.2mm) for the M11x0.8.


Hope this helps.


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## keithbyrd (Nov 22, 2018)

Chris,
Thank you so much - this is exactly what I was looking for!  
I don't have an engineering/math background so this really helps.
Follow up question!
does the GD-4 and GD-5 simply mean triple start?  the only visible differences I can see on them is the GD4 has twice the amount of taper on the starting threads.
I will check the prices on some drill bits here and get back to you on the question about rebates!
Thank you for your help!


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## chrisk (Nov 22, 2018)

No engineering background here either...
As I understood, these letters shouldn't be specific to the 3ple lead but instead to the threads as other collegues wrote above. They should refer to pitch diameter limits (internal and external thread tolerances???). Now I can't go further for this is beyond my comprehension. While I have an engineering manual (Machinery's Handbook) I really need a translator... 

For the prices on the Dehaye webshop I think the drill bits of interest for us aren't still uploaded. But if you ask me the sizes you need I can find the prices on their printed catalogue.


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## randyrls (Nov 22, 2018)

To join the Thread;  Keith,   MSC has metric drill bits in metric (odd) sizes like 12.2mm.

They also have a Distribution center near the 81/78 (jonestown exit) split north of Harrisburg and you can order from them with a will call/pickup.  i am just north of Harrisburg and sometimes  I save up and place an order.  A few hours later the items are available and i go pick them up.  I doubt they are open on Thanksgiving.

HAPPY THANKSGIVING EVERYONE!!!


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## keithbyrd (Nov 22, 2018)

Thank you Chris and Randy!

Happy Thanksgiving!!


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## keithbyrd (Nov 22, 2018)

Another question!  To make sure I am correct - it is better to drill slightly larger than required yielding less material for threads but prooducing better threads?  Am I understanding this correctly? 
 Is this also true for dies also?


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## bmachin (Nov 22, 2018)

Victor Machinery has all the decimal metric drills as well and probably substantially cheaper than MSC. They do, however, have a $25 minimum order.

https://www.victornet.com

FWIW,
Bill


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## eharri446 (Nov 22, 2018)

Here is a list of the various drill bit sizes for the taps that we use:

M14X.8 - 13.2mm, M13X.8 - 12.2mm, M12x.8 - 11.2mm, M11x.8 - 10.2mm, 
M7.9x.6 - 7.3mm, M6.4X.6 - 5.9mm, M6.5x0.5 - 6mm, M7.5x0.5 - 7mm, M8.5X1 7.5mm

I was able to order all of these from http://Victornet.com or http://drillsandcutters.com


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## chrisk (Nov 23, 2018)

keithbyrd said:


> Another question!  To make sure I am correct - it is better to drill slightly larger than required yielding less material for threads but prooducing better threads?  Am I understanding this correctly?
> Is this also true for dies also?




Keith here is a quote from a Mike Redburn text: "The general rule of thumb is to cut the tenons for the male threads about .2mm smaller than the thread size you're going to cut. For a m12 thread size that would be the equivalent of 11.8mm (.465) the drill size is determined by the subtracting the pitch from the desired thread size. Or 12mm‐.75=11.25mm. I generally make a hole slightly larger than the exact size say 11.3 to 11.4."


The original Mike Redburn's document: http://content.penturners.org/library/general_reference/taps_dies_kitless.pdf


If I'm not mistaken, I think the first to mention this technique  (0.2mm larger hole/smaller tenon than the standard ones) is one of our  colleagues from the UK, namely skiprat.


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## keithbyrd (Nov 23, 2018)

chrisk said:


> keithbyrd said:
> 
> 
> > Another question!  To make sure I am correct - it is better to drill slightly larger than required yielding less material for threads but prooducing better threads?  Am I understanding this correctly?
> ...



Thank you Chris!


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## keithbyrd (Nov 23, 2018)

Thank you Elwin and Bill!


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## keithbyrd (Nov 23, 2018)

I am trying to make a chart to simplify my decisions on which bit s to use etc 
Some of the info is confusing me so let me try this:
Chris quoted Mike Redburn:
 "The general rule of thumb is to cut the tenons for the male threads about .2mm smaller than the thread size you're going to cut.* For a m12 thread size that would be the equivalent of 11.8mm (.465) the drill size is determined by the subtracting the pitch from the desired thread size. Or 12mm‐.75=11.25mm. I generally make a hole slightly larger than the exact size say 11.3 to 11.4.*"
I may be over thinking this because  I hate to make mistakes and ruin pens or materials!  
1. The bold face line says an M12 is -equivalent to 11.8mm. m12 is 0.4724 and 11.8 is 0.465 - how are they equivalent?
2.If M12 minus the pitch is 11.25 how is that equal to the statement M12 is equivalent to 11.8mm?
3.general rule is to cut the tenons for male threads about .2mm smaller than threads you are going to cut.......I generally make a hole slightly larger.  - cutting a tenon isn't a hole.  why is the reference to making the hole slightly larger in the discussion about tenons? When making a tenon I don't make a hole or use a drill.  
I know I must be missing something simple!


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## monophoto (Nov 23, 2018)

keithbyrd said:


> I know I must be missing something simple!



Keith -

It's not you - the information you have been given really is confusing .  It seems to be a jumble between guidance for cutting tenons and drilling holes.

My understanding is as follows:

When cutting a tenon that will subsequently become a male thread, the tenon should be about 0.2mm smaller than the major diameter of the thread.  That is, if the objective is an M12-0.75 thread, start with an 11.8mm diameter tenon.  

When drilling a hole that will subsequently become a female thread, the hole diameter should be equal to the difference between the major diameter of the thread, and the pitch of the thread.  Again, if the thread is to be M12-0.75, then the hole diameter should be 11.25mm.


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## chrisk (Nov 23, 2018)

Keith, I apologize if I contributed to add some confusion.

What Mike Redburn tried to explain is that some materials we use for kitless pens (like Polyester resin), due to their brittleness, require some tolerance when we make our threads, male or female. Hence, he advises to substract up to 0.2mm when we turn the tenon (for the male thread) and add up to 0,2mm when drilling the hole.

If you read this specific post by skiprat you'll understand the meaning of all this (post 21 + two pictures on post 29):
http://www.penturners.org/forum/f30/dummies-guide-tapping-lathe-59693/index3.html#post999180


To summarize, if I was you, I would *first *proceed with *standard *male and female *threads *respectively, or in other words apply the theory. Thats is, for a M13x0.8 thread (as you have this set of tap and die):

 - a 13mm (0.512") tenon for the male thread
- a 12.2mm (0.48") hole in order to tap the female thread (theory: thread Ø - pitch or Ø13-0.8=12.2)

 If these *standard threads* work fine don't change anything. But if you encounter any issues with some fragile materials, then you could experiment with the bigger hole/smaller tenon technique, explained by MRedburn and skiprat.


Again I apologize if I introduced some confusion by referring to this technique but we began our discussion about the appropriate imperial drill bits when working with metric taps and dies. Hence my digression related to the benefit of some tolerances.


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## duncsuss (Nov 23, 2018)

I buy my metric drill bits from Victor Machinery -- they sell the 8.25mm for $2.50.

Last time I bought from them, they had a $25 minimum order (not that I've ever had difficulty reaching that minimum!)

In case it hasn't become obvious from preceding posts, the drill bit to use for a metric thread is "diameter - thread pitch" ... for example:

9mm x 0.75 : use 8.25mm drill bit
10mm x 1 : use 9mm drill bit
12mm x 0.8 : use 11.2mm drill bit

Have fun playing in the world of kitless!


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