Using the Cross Slide for Threading

[expressline99]

When cutting an Acme and only using the cross. I would make the tool bit narrower that it should be. Set the compound to 90°. And use the compound to reposition the tool bit to cut just on one side of the Acme thread for each pass (for most of the time)…Dave

So just by changing the compound angle just by an degree or so... or less? Yes sometimes you have to dumb it down for me If it gets too simple especially. Seems like I could ruin the thread easily if I'm not careful.

Paul

 

[Bob Korves]

So just by changing the compound angle just by an degree or so... or less? Yes sometimes you have to dumb it down for me If it gets too simple especially. Seems like I could ruin the thread easily if I'm not careful.

Paul

Not changing the angle with the compound, changing the position of the cut from side to side with the compound, with the compound oriented 90 degrees to the cross slide.

 

[tertiaryjim]

Had to look it up.
Tangent of helix angle = Lead of thread divided by circumference of screw

So... Lead of thread divided by ( PI x Dia.) = tangent of the helix angle

Don't forget to add 4 to 6 deg. for relief of the cutting face.

I just had to look at the formula and think a bit to get it straight in my head.
Also, I have just figured the infeed with the compound set at 14 deg. and then cut the
acme thread like I cut 60 deg. threads using the compound.

I once thought that the trailing edge of the threading tool could be left with a 90 deg. face
so the tool might be just a bit stronger.
But, in practice it produced a rough face while a 4 deg relief produced a smooth face.
Cast iron might do better with a 90 deg. trailing edge of the threading tool
but that would need to be tried and proven.

Perhaps I hadn't honed the tool properly but I now just plan on relieving every face.
OK, I've prattled and rattled and stated what was already said but now it's clear in my own head.