# SHALLOW THREADS



## riversidedan (Jul 18, 2021)

been playing around the tap/die projects and just ran a M10 1.5 die down a piece of 6061 , the cut was good and forceful
but when done the threads looked a bit shallow and I dont have a nut to test,  whats the cause  for shallow threads?

what comes to mind is a "funky  die


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## talvare (Jul 18, 2021)

Ya, those threads don't look fully formed. Are you sure your major diameter was correct before you ran the die. I can't tell for sure from your photo, but is that an adjustable die ?

Ted


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## riversidedan (Jul 18, 2021)

I looked a few places and couldnt find out what size a rod had to be for a die so it was a guess but the die was tight on the part so I figured it was close enuff

not an adjustable die>>but am guessing a adjustable die is split to squeez in or out


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## mksj (Jul 18, 2021)

Thread calculator will give you the major and minor dimensions for internal and external threads according to the class/fit you want, so you would want to start with an OD of ~9.9 mm. It appears that you are only partially cutting the minor dimension, but are under on the major. I would check the OD of your threads. You also have some tearing of the threads, I would use some form of threading fluid and also reverse the direction of threading every 2-3 turns to break the chip. Better dies often are adjustable, so you can tweak the final dimensions. Also thread dies are directional, so the wider side fits onto the OD of the rod and gradually increases the depth of the cut as the die moves down the rod.
Internal Threads: https://amesweb.info/Screws/metric-internal-thread-dimensions-chart.aspx

External Thread: https://amesweb.info/Screws/metric-external-thread-dimensions-chart.aspx


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## riversidedan (Jul 18, 2021)

so it sez for example for a  10M x1.25 piece ,  8.647 min 10.320 max drill to get a piece ready to tap or die, sound right?


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## mksj (Jul 19, 2021)

Dimensions are different for an internal thread where you use a tap and an external thread where you use a die. Internal thread you need to look at the upper and lower limits for the minor diameter under internal threads. External threads where you use a die you want to look at the major diameter for an external thread.

So cutting a external thread for a 10MX1.25 with a die, you would still want to start with an OD of around 9.9". The major diameter range varies slightly based on the tolerance class for the particular thread, just realize that there needs to be some degree of clearance between the internal and external thread. If I was cutting an external thread I probably would start out with a 10 mm rod and thread it on the lathe and then take off the peaks with a file, and/or chase it with an adjustable die for final sizing.

Cutting internal threads with a tap is based on the minor thread diameter which changes with the thread pitch. A M10x1.25 the minor diameter range is 8.647-8.912 mm, the tapping chart recommends using a 8.70 mm or 0.3425" drill size. I would use a lettered drill "S" which is 0.3480". The Major diameter that the tap cuts should be slightly over 10 mm The major diameter range is 10.000-10.340". The degree of thread forming may also vary based on the material, the size of the tap and the strength needed. In some materials with smaller tabs you may want to start with a slightly larger hole to prevent the tap from breaking, assume you do not need maximum strength of the thread.

There are slight variations on the dimensions depending on the charts you use and the tap/dies you use.


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