basic acme thread insert size question

[Bill D]

This is a basic question about acme threading inserts. For normal 60 degree vee shaped threads one insert size and one tool can cover a range of sizes. I know the peaks and valleys are not supposed to be a sharp corner but the bar can hold different corner radius cutters and make useable threads.
How does that work for Acme inserts. I want to make 12TPI acme threads. Do i have to buy inserts and a tool holder only for 12TPI or will the same tool holder cover say 10-14TPI size inserts.
Bill D

 

[Mark Rand]

The same tool holder used for 'V' threads can be used for different pitch ACME inserts within what's available for that size of insert. You obviously neet the insert specific to that pitch.
One gotcha with ACME threads is that the pitch is normally quite coarse. You can need to buy different angled seats for the inserts (if you can find them) or make angled wedges for under the tool holder, as I had to do when turning a 3/8" 10TPI LH ACME thread with a RH insert.

 

[EmGo]

A one-off acme thread is where I go to hss without even passing carbide, do not waste your time, do not pay $200. You'd be all done cutting the thread with hss long before you even figure out what pieces to buy in the insert catalog.

 

[Mark Rand]

It's not too hard to type in something like ER16 10tpi acme into a search engine.

 

[Kingbob]

This is a basic question about acme threading inserts. For normal 60 degree vee shaped threads one insert size and one tool can cover a range of sizes. I know the peaks and valleys are not supposed to be a sharp corner but the bar can hold different corner radius cutters and make useable threads.
How does that work for Acme inserts. I want to make 12TPI acme threads. Do i have to buy inserts and a tool holder only for 12TPI or will the same tool holder cover say 10-14TPI size inserts.
Bill D

Yes but also yes. If you just have one part to make you can use any 29.5° insert or hss bit to cut your thread as long as the tip of your cutting tool is narrower than the root width of your thread. The also yes is that in a shop that cuts a lot of acme threads we do carry inserts for each specific tpi. We used to cut thousands of acme threaded parts per year and had a huge library of inserts for standard and proprietary modified acme profiles. In a pinch you just use the next size down insert (6 tpi insert to cut a 4 tpi thread) and off set the tool in Z axis to widen the root until she gauges. In a manual you just use the compound to advance the tool. I printed out a 1" 12 tpi for you - let me know your diameter and I'll do it again for you.

 

[winger]

Width of the tool tip changes with the pitch. Same for trapezoidal theads.

Gage for grinding the tool is not real expensive.
Dave

 

[Bill D]

It's not too hard to type in something like ER16 10tpi acme into a search engine.

When i read ER16 I was thinking collet system for a vertical mill. Thanks for the insight. That does sound very possible.
Bill D.

 

[Bill D]

Width of the tool tip changes with the pitch. Same for trapezoidal theads.

Gage for grinding the tool is not real expensive.
Dave

I have yet to see a gauge for sale that goes under 10 tpi. Hence my thoughts on using inserts for a one off job.
BillD

 

[EmGo]

I have yet to see a gauge for sale that goes under 10 tpi.

As long as you measure the thread over wires tho, I don't think the root is very critical. Should fit air, as long as it is smaller than the female part id you're okay. Just measure with calipers.

 

[winger]

Had to check, mine stops at 10 also.

Dave