Guys and or Gals,
I need some help. I have a Myford ML7 with a 1.125" x 12 TPI mandrel nose thread. I have in the past made numerous backplates and adapters for the machine using a commercial 55* boring bar or more recently 11 IR AG55 inserts in a SNR0012M11 boring bar. I have also used the same boring bar with 11 IR AG60 inserts for 60* internal threads with no problems.
However, I recently needed to produce an external thread to replicate the mandrel thread. I have a SER1212H16 holder in which, using 16 ER AG60 inserts I have successfully produced 60* external threads. The problem arose when I tried to produce 55* threads using 16 ER AG55 inserts. I set the tool holder up in the same fashion as I would for 60* i.e. the holder's left face parallel to the chuck face or at 90* to the work and the result is a sawtooth looking thread. My thread setup gauge is too large to accurately accommodate the small cutting tip on the insert so it's a bit of a guess going that route.
Why?
Do I need a different holder? I don't seem to be able to get an answer from the insert supplier. The inserts are manufactured by two different companies.
When held on top of one another for comparison the tips of the cutting edges i.e. the root of the thread seem to be in line, with the "skirts" of the thread forms separated by a similar amount on each side yet the thread produced looks like there was no adjustment made for the 5* difference in the included angle and the right edge is almost vertical while the left edge is way more than 27.5* from vertical. See the attached photo where the thread on the left is from an old mandrel while the thread on the right is my fiasco.
If anyone can enlighten me as to what I'm doing wrong I'd appreciate their help. If I need a different holder a part number and source would also help. Thanks in advance,
Twistit
I need some help. I have a Myford ML7 with a 1.125" x 12 TPI mandrel nose thread. I have in the past made numerous backplates and adapters for the machine using a commercial 55* boring bar or more recently 11 IR AG55 inserts in a SNR0012M11 boring bar. I have also used the same boring bar with 11 IR AG60 inserts for 60* internal threads with no problems.
However, I recently needed to produce an external thread to replicate the mandrel thread. I have a SER1212H16 holder in which, using 16 ER AG60 inserts I have successfully produced 60* external threads. The problem arose when I tried to produce 55* threads using 16 ER AG55 inserts. I set the tool holder up in the same fashion as I would for 60* i.e. the holder's left face parallel to the chuck face or at 90* to the work and the result is a sawtooth looking thread. My thread setup gauge is too large to accurately accommodate the small cutting tip on the insert so it's a bit of a guess going that route.
Why?
Do I need a different holder? I don't seem to be able to get an answer from the insert supplier. The inserts are manufactured by two different companies.
When held on top of one another for comparison the tips of the cutting edges i.e. the root of the thread seem to be in line, with the "skirts" of the thread forms separated by a similar amount on each side yet the thread produced looks like there was no adjustment made for the 5* difference in the included angle and the right edge is almost vertical while the left edge is way more than 27.5* from vertical. See the attached photo where the thread on the left is from an old mandrel while the thread on the right is my fiasco.
If anyone can enlighten me as to what I'm doing wrong I'd appreciate their help. If I need a different holder a part number and source would also help. Thanks in advance,
Twistit