New to Kitless - Tap Drill Sizes

[egnald]

Greetings from Nebraska. I'm just getting set up and started doing Kitless. I have a good selection of Taps and Dies but I don't really have any Tap Drills yet. I'm hoping for confirmation and/or alternatives based on your experience.

Here is what I have figured out so far.
I hope someone can confirm or suggest alternatives before I buy a bunch of Drills.

M13 x 0.8 Triple Start - 31/64" Drill?
M12 x 0.8 Triple Start - 11.25mm Drill?
M12 x 0.75 Single Start - 11.25mm Drill?
M12 x 1.0 Single Start - 11mm Drill?
M11 x 1.0 Single Start - 10mm Drill?
M10 x 1.0 Single Start - 9mm Drill?
M10 x 0.75 Single Start - Letter U Drill?
M9 x 0.75 Single Start - Letter P Drill?
M7.9 x 0.6 Single Start - 19/64 Drill?
M6.5 x 0.5 Single Start - 6mm Drill?
M6.4 x 0.6 Single Start - #1 Drill?

Thanks,
Dave

 

[duncsuss]

Dave, the standard choice for metric is to drill the hole the tap diameter minus the tap pitch.

You correctly chose 9mm for tap M10 x 1.0 - it's (10-1.0)

Apply the same arithmetic to all the taps you own, and you'll have a list of metric sized drill bits. Many of them have very close equivalents either in the (n times 1/64") series or in the letter/number bit ranges.

If I don't have the exact metric size, I allow myself to get away with the nearest larger diameter so long as it's not too far off. More often I make a purchase from Victor Machinery Exchange - they have an extensive metric selection (e.g. 8.25mm which is perfect for M9 x 0.75 threads.)

That said ... it doesn't always work, because some materials are kind of rubbery and flex out of the way of the tap instead of cutting off clean. I find I have to use a slightly larger drill bit when I'm working with hard rubber (ebonite) compared with acrylic acetate. A number of nib units got kinda wedged in the nib sections that I made using the exact numbers, before it occurred to me I should compensate for the nature of the material.

Hope this helps.

 

[d_bondi]

Hello Dave,

Of your list, I use three of these taps, when making my kitless pens. Here is my input.

M13 x 0.8 Triple Start - 31/64" Drill? - YES, this is what I use.
M12 x 0.8 Triple Start - 11.25mm Drill?
M12 x 0.75 Single Start - 11.25mm Drill?
M12 x 1.0 Single Start - 11mm Drill?
M11 x 1.0 Single Start - 10mm Drill?
M10 x 1.0 Single Start - 9mm Drill? - YES, this is what I use.
M10 x 0.75 Single Start - Letter U Drill?
M9 x 0.75 Single Start - Letter P Drill?
M7.9 x 0.6 Single Start - 19/64 Drill? - I believe this is the Bock 250 (#6) tap, correct? I use a Letter M bit for this. For what it's worth, Rick Herrell's step bit for the Bock #6 is 0.295 for the threads, which is the same as the Letter M bit.
M6.5 x 0.5 Single Start - 6mm Drill?
M6.4 x 0.6 Single Start - #1 Drill?

I agree with Duncan's (@duncsuss) statements and have had similar experiences related to different materials, including ebonite as he mentioned.

Happy to help with any other questions you might have.

David

 

[egnald]

Hello Dave,

Of your list, I use three of these taps, when making my kitless pens. Here is my input.

M13 x 0.8 Triple Start - 31/64" Drill? - YES, this is what I use.
M12 x 0.8 Triple Start - 11.25mm Drill?
M12 x 0.75 Single Start - 11.25mm Drill?
M12 x 1.0 Single Start - 11mm Drill?
M11 x 1.0 Single Start - 10mm Drill?
M10 x 1.0 Single Start - 9mm Drill? - YES, this is what I use.
M10 x 0.75 Single Start - Letter U Drill?
M9 x 0.75 Single Start - Letter P Drill?
M7.9 x 0.6 Single Start - 19/64 Drill? - I believe this is the Bock 250 (#6) tap, correct? I use a Letter M bit for this. For what it's worth, Rick Herrell's step bit for the Bock #6 is 0.295 for the threads, which is the same as the Letter M bit.
M6.5 x 0.5 Single Start - 6mm Drill?
M6.4 x 0.6 Single Start - #1 Drill?

I agree with Duncan's (@duncsuss) statements and have had similar experiences related to different materials, including ebonite as he mentioned.

Happy to help with any other questions you might have.

David

This is Perfect information and is precisely what I was hoping for. Thank you so much for your input and suggestion about step drills. - Dave

 

[rixstix]

Hi Dave,

Here's my chart. The differences are mainly due to drill index sizes vs purchasing metric bits. I learned the hard way that the HarborFreight index was causing issues due to out of round and off-center points. Bought an index from Rick Herrell recommendation and all has been fine since.

I use the m9.5x.8 (actually 3/8" UNEF) more than anything.

 

[egnald]

Hi Dave,

Here's my chart. The differences are mainly due to drill index sizes vs purchasing metric bits. I learned the hard way that the HarborFreight index was causing issues due to out of round and off-center points. Bought an index from Rick Herrell recommendation and all has been fine since.

I use the m9.5x.8 (actually 3/8" UNEF) more than anything.

Great. Thanks a bunch. This information was very helpful.
I have a big HF index too, but I just use it occasionally for an odd size where I don't have a dedicated bit for the job.

I try to buy specific bits from McMaster Carr for specific jobs though. For example, for plastic blanks I usually buy bits specifically designed for plastic. They Jobber length and have a 60 degree standard point and near zero rake angles to help reduce heat, chipping and cracking. - Dave

 

[d_bondi]

I need to check out those bits designed for plastic.

As Duncan (@duncsuss) noted above Victor Machinery is a source. I have not used them yet, but they get many mentions on the "As the Pen Turns" podcast.

I purchased a set of stub bits and use them whenever they are long enough for what I am doing. I feel like the shorter length significantly reduces the play. It all adds up, quill, Jacobs Chuck, bit length...

 

[egnald]

I need to check out those bits designed for plastic.

As Duncan (@duncsuss) noted above Victor Machinery is a source. I have not used them yet, but they get many mentions on the "As the Pen Turns" podcast.

I purchased a set of stub bits and use them whenever they are long enough for what I am doing. I feel like the shorter length significantly reduces the play. It all adds up, quill, Jacobs Chuck, bit length...

I absolutely agree with the stub (screw machine) length bits. I have found this to be true especially when drilling for tapping. I even start out with a stub and then go to a jobber if I need the extra length as the stub hole helps act as a guide when I go in for the extra depth. - Dave