Threading tool pitch correction

Hi

I'm investing in new lathe tool holders.
For the thread turning tools some holders got a insert/plate underneath the insert to correct the pitch if I'm right.
I bought a new internal threading tool but it doesn't have a plate underneath the insert. Should I return it and buy one with changeable plate to correct pitch?
Price for both tools is around the same.

tcncj said:

Hi

I'm investing in new lathe tool holders.
For the thread turning tools some holders got a insert/plate underneath the insert to correct the pitch if I'm right.
I bought a new internal threading tool but it doesn't have a plate underneath the insert. Should I return it and buy one with changeable plate to correct pitch?
Price for both tools is around the same.

Click to expand...

Internal threading tools often come without the anvil/plate as there is limited space available.
Insert pocket is set to angle that works with standard pitches.
Mitsubishi has also internal threading tools with increased angle but you need those only for something like large pitch multi-start thread: http://www.mitsubishicarbide.com/application/files/3314/4774/7034/b053g.pdf

page 22 has further explanation:
Insert inclination angle and thread lead angle have to be within 2.5 degrees of each. Metric fine thread would be within acceptable range even without any insert tilting/shimming.

I have the shims on my Sandvik laydown threading tools. As I understand it the shims do not correct the pitch, but correct the relief angle and the helix changes with different pitches. Definitely a difference at the outer limits of the pitch options, but a few pitchs +/- its tough to notice. I will say the Sandvik inserts outlast just about all others. I am not sure if that has anything to do with the shims or if its the inserts.

I loved Sandvik...and yes I said lov"ed" as I'm a jobbing shop and often do not need to buy packs of 10 inserts for oddball threads, especially as their inserts do not fit other holders and can come in at almost twice the price. Well maybe not twice, but substantially more...then add you need to buy 10 pieces.

For me my turning point was when I needed to do a Buttress thread in plastic for a job I run once every two years...maybe 100 piece per run. What am I going to do with 9 extra buttress inserts at $28ea. Carmex holder, $60. 2 inserts at $15 each.

I still use the Sandvik on touchy materials with long runs...it worth it then.

SIM said:

As I understand it the shims do not correct the pitch, but correct the relief angle and the helix changes with different pitches.

Definitely a difference at the outer limits of the pitch options, but a few pitchs +/- its tough to notice. I will say the Sandvik inserts outlast just about all others. I am not sure if that has anything to do with the shims or if its the inserts.

Click to expand...

Probably what the OP meant after all.

With laydown inserts on internal threading tool the same angle should work for all the single-ended internal threads as the tool diameter or insert size is the limiting factor how coarse internal thread you can make. With IR16 the most coarse possible thread is something like M22x3 and that has 2.49 degree lead angle.

I need to cut M24x3

The holder with shims is only 10,- Euro more
I think best to return it and buy the one with shims.

tcncj said:

I need to cut M24x3

The holder with shims is only 10,- Euro more
I think best to return it and buy the one with shims.

Click to expand...

Just double-check it fits in the starting bore
Korloy and Mitsubishi bars with shim insert won't fit.

I have got caught with the laydown insert boring bar minimum bore size more than once..