Thread Cutting on the Lathe, Part Two - Grinding the Tool

[doubleboost]

(08-04-2013, 02:44 PM)TomG Wrote: The new video is up and as an added bonus it's now available in HD. The mistake is corrected, now if I could just do something about the narrator.

Tom

I could do you a voice over
John

[TomG]

(08-04-2013, 03:03 PM)dallen Wrote: why is it that the inserts that I have, have no flat on the point.

DA

Probably so they can cut finer pitched threads. For instance, the tool for a 28 pitch thread would only have a flat about .005" wide, if any.

Tom

[PixMan]

(08-04-2013, 03:03 PM)dallen Wrote: why is it that the inserts that I have, have no flat on the point.

DA

What is the insert designation that you have? There are many types for threading, the two most common being 16ER/IR (3ER/IR in Vardex parlance) and Top Notch style. The 16ER (as well as 6ER, 11ER, 22ER and 27ER) are the triangular lay down style which can be either full profile pitch specific or "general purpose" partial profile A60 or AG60 for threads ranging from 16-48 and 8-48 respectively. Those will have a .002" radius on each tip. It's a compromise between a true Sharp V thread and a true UN thread. The pitch specific full profile ER/EL/IR/IL series has a radius of the proper dimension for each thread pitch. This makes a rounded root thread rather than flat root, though a flat crest.

When we grind a tool by hand and put the calculated flat on it, that is also a compromise to true UN standards of having a rounded root but is more widely accepted than Sharp V or the .002" radius.

[stevec]

I thought I understood that ANY cutting tool should have some form of radius on the tip. The reason being if you start cutting with a "sharp" tip on the tool it'll try to make it's own flat or radius, not a good thing.

[dallen]

Pixman
the ones that I use for most of my outside threading are some that I got off of evil bay, the box didn't have any numbers on it anyway the label was tore off, all I can tell you is that they were in a kennematal box, and are #3 top loc inserts. I use them in a 1" square holder that I cut a dovetail in the side so it would fit onto my tool post.

I have a couple others that use different inserts, one uses a vertical triangle insert.

DA