Jump to content

Help needed with sizing for making screw threads and nuts


Recommended Posts

I have only done tapping and threading once in my life and this was in Bill Robertson's class this year in Tune. I just looked at the instructions again and my question is where can I find a chart that tells you how big to drill the hole for tapping and that will also tell you how big your outside diameter should be on the part that you want to thread.

Link to comment
Share on other sites

Here is a handy web page that should help:




A google of something like "drill and tap chart" should turn up a bunch of items that would be printable too. Also Starrett tools offers free charts on their web site, from big wall versions to little pocket ones. Their catalog has all that info in it too, and they are free as well. See link below. I'm sure they would ship to S.A.







Link to comment
Share on other sites

Thank you Paul, I did find a chart that shows the sizes...in Bill's photo of his watchmaker tap and die set, the sizes are all in the lid :-)

Link to comment
Share on other sites

When it comes to tiny screws J. I. Morris company is a leader in the field, that is all they do. They have American sizes 0000/160 to 00/90 and UNM sizes 0.3 to 1.20. For things like 00/90s they are really reasonable priced and much better quality than some Asian imports. The tiny stuff can get super expensive.

Here is a link to their spec page.


Link to comment
Share on other sites

Maybe this will help some .  The basic formula is D (basic OD of screw or tap) — 2h (h=depth of thread) X 75% = hole drill size.  

For the very mini threads I use 1 1/2h.    


Maybe some more knowledgable person can chime in here.

Link to comment
Share on other sites

Here is something I have found to come in handy.

For Metric Threads : Tap Drill size is Screw size minus Pitch

So for example an M2 x 0.45 Screw the Tap Drill size would be 1.55

an M1.5 x 0.35 Screw the Tap Drill size would be 1.15

I'm not sure how they determine the Tap Drill sizes for American Threads. I always refer to the charts, but I checked

a few sizes by subtracting the pitch from Screw size and this seems to be pretty close to what the chart says.

Pitch = 1 divided by number of threads per inch. Bob

Link to comment
Share on other sites

  • 8 months later...

I still have not purchased a 0-80 tap & die set to replace my missing part for my needlework stand from GS 2015.  What is the difference between the Morris set that Bill H photographed -- referencing Elga's candlestick class and the tap & dies from MSC?


I am assuming that the tap & die set used at Guild School were MSC products... but the Morris set has that nice knurled holder.... is one product easier then the other product to use?


And what are the other more common sizes that I should purchase, in addition to the 0-80?  I like the MSC sources, as I have no shipping and no need to have a backup if I break anything - trying to build an order... :) it looks like first time email disclosure gets me 25%, and if I build a large order perhaps as much as 35%. 


The JI Morris company would charge me $10 to ship a single 0-80 die - is it even an cubic inch in size?!!!

They must send somebody with it to help me have a good out of the box experience for the $10 shipping.


So someone please talk me into the superior nature of the JI Morris product!  And it looks like 4 sizes on their website, which match the photo of Bill Hudson's set... Suddenly the set on eBay looks like a great deal.


I do not have as much problem paying for the tap & die as the $10 shipping ....


Holy Wingnut Batman!  I think I've gotten myself into some expensive hobby!


Which part is more likely to get broken?  The Tap that creates the nut or the die that creates the thread?

Just curious... I haven't broke a lot of things - yet but when the planets are not in alignment stuff happens.




Link to comment
Share on other sites

  • 1 month later...

Most of the charts I found tells you the hole size for when you want to tap to fit an existing screw, but I had great difficulty in finding a chart that tells you to which diameter to turn your stock when you actually want to make a screw, I found this very nice chart yesterday both in metric and inches.


Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...