Measuring thread pitch and lead angle

[[Ar...]]

Hello,

How you would measure the pitch and lead angle from this? Thread is 35mm long and 47mm diameter in other end and 42 in the other.

At the moment I just measure 1mm long 2D-line on lead angle surface and compare it to center axis of part.
I'm also trying to optically measure it from straight above, but this is no way accurate way. pitch of thread is too big and distorts the results.

I'm seeing 6 angle minutes of variation in measuring (probing) the lead angle and the tolerance is 9 angle minutes. I'm probing with1mm dia probe. Running on O-inspect 322 with vast xxt.

Any help is appreciated

[[Ke...]]

Interesting, I have not had this style of thread cross my plate.

Using the CMM, I typically try to get styli that match the thread pin diameters, for the over pin measurements. Then I measure self centering points (using midpoint), and just get the distances between them.

Most threads I use a MarSurf (LD260) and use theoretical spheres between the flanks, and do center of sphere to center of sphere there as well, and measure the flank angles on there, as well.

I tried using the CMM using 2d lines (using a pattern), to get flank angles and use the Tangents function to create theoretical spheres there as well... but there were too many calculation errors. If it's a short thread (mine were 3-6" long) you may have better luck.

[[Ma...]]

I am pretty curious how it's made. It looks like normal 60° thread, but that should have tilted 30° side as far as i know how to make threads on cone.

[[Ar...]]

Okay,

I did get good result with measuring pitch, but flank angle was not so good.. Deviation was too much. These measurements are to only verify that we can machine similar parts.

I think the trickiest part in measuring flank angle is fact that helix angle changes when you move up or down in cone. This causes error for the measurement.

These parts are machined with 5 axis cnc. 3D- toolpath and small diameter ball endmill.