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View Full Version : On Edge Threading inserts vs. Flat threading inserts



Darrp
07-17-2019, 11:40 PM
A friend of mine texted me the other day from a garage sale that he stopped at. He told me that this gentleman was selling carbide inserts for .50 cents to a dollar per insert. He was fairly close so I drove over and bought some Dorian Carbide On Edge Threading inserts and a few other things.

I currently use the Flat (for lack of a better term) indexable inserts and I have been quite happy with them, but I would like a second holder for my other lathe. I am thinking that I have 10 inserts so for the cost of a toolholder I would be set for a while.

So my question is for those of you that have used both On Edge Threading inserts and Flat indexable inserts I would appreciate it if you would share your thoughts.

https://www.traverscanada.com/terra-carbide-tnma43nv-apc5t-indexable-carbide-insert-60176-v-thread/p/22-150-097/

The background;

Small lathe is an 11x36 Standard Modern

Larger lathe is 17x44 Chin Hung

tomato coupe
07-18-2019, 12:08 AM
By flat, do you mean laydown? I prefer full-profile laydown style, followed by partial-profile laydown style, and lastly on-edge style. The on-edge style tend to leave a pretty gnarly crest on the threads.

darryl
07-18-2019, 01:13 AM
If I'm understanding this right, I would think that the on-edge style would be stronger- but would require the holder to be adjustable so you could set a proper helix angle for the particular thread and diameter of work piece.

mihit
07-18-2019, 04:28 AM
A $4 piece of HSS goes a long long way...

I use these on a 16mm shank holder on the medium lathe:
https://www.kyocera-unimerco.com/kyocera/metal/turning-tools/thread-turning/inserts-for-thread-turning/
16ERG60 blahblahblah.
Peels pre-hard 41XX just fine.

JoeLee
07-18-2019, 08:03 AM
By flat, do you mean laydown? I prefer full-profile laydown style, followed by partial-profile laydown style, and lastly on-edge style. The on-edge style tend to leave a pretty gnarly crest on the threads.Yep, full profile is the way to go. Once you use them you'll never go back to a general purpose 60 deg. insert.
They cut a perfect thread from root to crest, no "gnarly crest" so you can cut to the perfect fit.

JL............

CCWKen
07-18-2019, 08:18 AM
Besides that, the on-edge style is "old-school" now. :) Everybody was practically giving them away a couple of years ago. And the cost of tooling was not cheap.

loose nut
07-18-2019, 11:15 AM
A $4 piece of HSS goes a long long way...

I use these on a 16mm shank holder on the medium lathe:
https://www.kyocera-unimerco.com/kyocera/metal/turning-tools/thread-turning/inserts-for-thread-turning/
16ERG60 blahblahblah.
Peels pre-hard 41XX just fine.

And will last a lifetime.

BCRider
07-18-2019, 12:39 PM
Shouldn't be too hard to mill a holder for the style indicated by your link.

I'm going to guess that you'll want/need to make it with a bit of a lean angle to allow for the helix angle for a more common sort of threading job. The insert itself does have a touch of clearance but it doesn't look like a lot. A bit of math to figure out the helix angle for a few of the common size pitches and perhaps do a square holder with one angle on one end and a slightly different angle on the other to cover the whole range?

Other than the slight angle it appears that you'd simply mill a seat with an angled back which the holding screw would push the one face up against. It's a 1/2" IC insert so by rights it would only need to be a piece of 1/2" square rod. But for use on the big machine you likely want to use 5/8" or 3/4" if that is a common size for that lathe. On the bigger size stuff I'd likely go for a pocket with is actually a "V" so it supports the insert more fully. And a little notch to clear the tip that is in the apex of the supporting "V". This means some delicate finish milling with a 1/8 or 5/32 end mill though. Or milling with a 3/16 inch end mill into a pre-drilled hole?

The downside is that with the insert being 3/16 thick and a 1/2" IC version you're "only" good for thread pitches of up to maybe 6 TPI. 5 and 4 TPI would see the span of one tooth being wider than the insert. And realistically you likely would not use it for even 6TPI. 7 or 8 would likely be the max to avoid the "V" becoming flat sided near the peaks. But if that's OK or you can live with a different tool for the seriously coarse pitches I'd agree that you're likely looking at a LONG time use for those inserts.

Darrp
07-18-2019, 12:41 PM
Thanks all!

Yes, I guess that the one I have on my S-M is a full-profile laydown style. I really like it, and I guess that I will get another one for the C-H with a slightly bigger shank.

Thanks again for the help!

tomato coupe
07-18-2019, 02:17 PM
I'm going to guess that you'll want/need to make it with a bit of a lean angle to allow for the helix angle for a more common sort of threading job. The insert itself does have a touch of clearance but it doesn't look like a lot. A bit of math to figure out the helix angle for a few of the common size pitches and perhaps do a square holder with one angle on one end and a slightly different angle on the other to cover the whole range?

The commercial holders I've got (Dorian) hold the inserts perpendicular to the work piece.

Darrp
07-18-2019, 07:40 PM
Shouldn't be too hard to mill a holder for the style indicated by your link.

Actually that's not a bad idea, maybe in the winter but its waaaay too busy during the summer. ;)

Video Man
07-18-2019, 08:42 PM
My first insert tool was for the on-edge type; I made my own simple holder which has worked fine for years. I now have the thread-form tools also, but the edge type has a very fine point and I have made 48tpi threads with it. Simple milling job from a leftover piece of ground tool stock. No helix angle, just simple perpendicular, works fine.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=5641&d=1563497103

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=5640&d=1563497103

Darrp
07-19-2019, 12:46 AM
My first insert tool was for the on-edge type; I made my own simple holder which has worked fine for years. I now have the thread-form tools also, but the edge type has a very fine point and I have made 48tpi threads with it. Simple milling job from a leftover piece of ground tool stock. No helix angle, just simple perpendicular, works fine.

Thanks for the pics. Looks great.

I will give it a shot when I get some time.

old mart
07-19-2019, 08:58 AM
I was forced to think of a way to make a laydown threading tool adjustable when confronted by a 1/2" X 8 double start ACME toolpost thread.
I milled the bottom of the threading tool down to take a pair of aluminium shims with a wedge section of the required angle, with a lip to prevent slipping, their thickness adjusted to bring the tip on centre height. I made another shim to restore the original height when normal threading was carried out.

BCRider
07-19-2019, 01:52 PM
The only improvement I'd suggest over VM's method is one of the conical head screws to push the insert firmly against the rear support edge. But yeah, otherwise just like that!

Video Man
07-19-2019, 07:23 PM
The only improvement I'd suggest over VM's method is one of the conical head screws to push the insert firmly against the rear support edge. But yeah, otherwise just like that!

BCRider has a good point, there, and to that end I tapered the heads of a couple of socket-head capscrews to try out, and it seems like a real good idea. Never had a problem, but more secure is better. Thanks, BCRider!

BCRider
07-20-2019, 02:14 AM
There's always room to make things a bit better with a trick or two, eh? If nothing else the conical screws with the push back against the flat back stop ensures that the insert seats the same way each time.