Tapered Pipe Threads and Sub Spindles

[generaldisarray]

I noticed this on another part a few days ago. But I couldnt be sure if it was me or not. So, today while programming a different part i did a test. I programmed the same tapered pipe thread first on the main spindle. Then after transfering the stock I copied that operation to the subspindle ops, changed only the tool,axis combos,z coords, start and end of thread signs. When I then post these two identical thread ops the r/l taper value is wrong on the subspindle.

Main

G0 X.7314 Z.2
G99 G92 X.5172 Z-.45 R-.0203 E.05263

 

sub

G0 X.7314 Z-.2
G99 G92 X.5172 Z.45 R-.0078 E.05263

 

 

Has anyone seen this before

[Guest MTB Technical Services]

Get used to it.

It's been an ongoing issue.

 

The long and short of it is you must modify your post as your post isn't accounting for the run-in distance.

The taper value is being incorrectly calculated from only the start point and the end point.

The run-in distance actually needs to be accounted for to get the proper taper angle.

 

Sit down with a calculator and manually calculate what the radial taper should be.

Make sure both L & R are correct.

[generaldisarray]

Thanks for the reply. Now I know its not just me!

Im no mathmatician. but here is how I have always done it

(sin1.78815)x = r/l

x being total length

I am using mpmaster. btw

[Guest MTB Technical Services]

The taper is 3⁄4 inch per foot or 62.5 millimeters per meter

Your angle is slightly off but not enough to matter

The actual angle is 1° 47′ 24″. or 1.789910608 .

 

It's common practice to simply drop the 24 seconds from the angle for the calculation.

If that's the case then you'll end up with 1.783333333 .

 

Just for the sake of clarity

SIN(1.789910608)*(Axial Length of Thread)

 

Out of curiosity, why are you using a G92 cycle for this?

[generaldisarray]

Instead of G76?

Habit / preference

 

I feel

In G92 everything is black and white for me.

 

G76 P010060 Q0 R0.
G76 X.4459 Z.775 P270 Q105 R0. F.05

 

This^^^ is too cyptic for my tastes