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Threading Wire Measurement to Advancement of tooling

gtj

Plastic
Joined
Oct 7, 2018
Hi There,

Noobie here. Been lurking for a while and learning lots from the forum and of course by making mistakes.
Have fabrication as a hobby in retirement.


Anyway, question is:
Is there a formula or way to determine the advancement of the cross slide required from the difference of the 3 wire measurement obtained to the target 3-wire measurement? I assume that the angles and round shape of the wires are going to enter into the determination, such that a simple 3-wire measurement subtraction is not going to equate to the required cross slide advancement

ie. thread cutting getting close and finishing off using the cross slide advancement, 3-wire measurement/M (.045 wires) say is at .522 for a 1/2-13 NC thread and target 3-wire measurement/M is .514

How can I determine the required cross slide advancement?

Much Appreciated
 
The 3-wire measuring method gives you the pitch diameter of the thread. This is a straight diameter, measured in X axis only.

The cross-slide moves straight in in the -X direction.

You want to move the wires straight in by -.008 in X direction(diameter mode)

So no, the angles of the flanks and the size/shape of the wires have nothing to do with it.

Just move straight in by whatever amount you need to.
 
IF the angle DID make any difference, it would be less than .002 per inch for that very slightly more that 3 degree helix angle of a 1/2 - 13
 
I'm puzzled by the two 'answers' above, guess I don't know what they are explaining.
My answer: Multiply the diameter change by 0.574 to get the "depth" to move the cross slide to reduce the pitch diameter. 0.522-0.514=0.008, so move cross slide by 0.0046

On edit . . .

Duh!!!! I was thinking advancement of COMPOUND slide set on 29.5 degrees. Oops!
 
Last edited:
How can I determine the required cross slide advancement?

Threads wires let you calculate pitch diameter. Like any diameter, if you want to reduce a diameter "1", move the the crosslide in "1/2" etc.

Where the formula comes into it is calculating what pitch diameter is of the work. It will depend on thread form - this gives most of it I think

https://www.threadcheck.com/technical-documents/thread-measuring-wire-formulas.pdf

If you are simpling trying to get one cut thread the same size as another, no calcs are needed (see opening sentence). Just move the cross slide in 1/2 of the difference.
 
Last edited:
I'm puzzled by the two 'answers' above, guess I don't know what they are explaining.
My answer: Multiply the diameter change by 0.574 to get the "depth" to move the cross slide to reduce the pitch diameter. 0.522-0.514=0.008, so move cross slide by 0.0046

awander got it right, no need to further multiply with .574

IF you set the tool/top slide to 30 degrees and IF you use the tool slide to advance the cutter then you need the trigonometry.
 
Over the years, using a Peedee thread wire chart, I don't even bother with calculating the theoretical PD. I just take the major nominal diameter of the thread and add the fraction in the ADD column, and that is the max target for the mike measurement. Anybody else do it this way?
 
Here's the short strokes:

dd = the measured difference in the diameter

x = the infeed of the compound at 29.5 degrees

x = dd / ( 2 x cos(29.5))

or using the value for the cosine and putting it all in the numerator

x = dd x 0.574

Or exactly what Mattij said.
 
If you are feeding in at 30 degrees, add 15% to your movement. It doesn't need a calculator, add 1/10, than add 1/2 that amount again.
 
Here's the short strokes:

dd = the measured difference in the diameter

x = the infeed of the compound at 29.5 degrees

x = dd / ( 2 x cos(29.5))

or using the value for the cosine and putting it all in the numerator

x = dd x 0.574

Or exactly what Mattij said.

OP asked how far to move in on the cross slide, NOT on the compound.
 
Thank You for the clarification.
I guess I was over thinking it.
Much Appreciated.
 
Threads wires let you calculate pitch diameter. Like any diameter, if you want to reduce a diameter "1", move the the crosslide in "1/2" etc.

Where the formula comes into it is calculating what pitch diameter is of the work. It will depend on thread form - this gives most of it I think

https://www.threadcheck.com/technical-documents/thread-measuring-wire-formulas.pdf

If you are simpling trying to get one cut thread the same size as another, no calcs are needed (see opening sentence). Just move the cross slide in 1/2 of the difference.

Thanks for the clarification. Much Appreciated
 
Threads wires let you calculate pitch diameter. Like any diameter, if you want to reduce a diameter "1", move the the crosslide in "1/2" etc.

Where the formula comes into it is calculating what pitch diameter is of the work. It will depend on thread form - this gives most of it I think

https://www.threadcheck.com/technical-documents/thread-measuring-wire-formulas.pdf

If you are simpling trying to get one cut thread the same size as another, no calcs are needed (see opening sentence). Just move the cross slide in 1/2 of the difference.

Thanks for the link. Very Informative.
 








 
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