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gftoolshop
06-28-2011, 04:48 AM
I often have to cut shafts that have been mig welded and have made it through so far but with a lot of headache. The TCMT inserts I use do ok after I've chewed of the the high spots and used up 3 or 4 inesrts. I saw a thread on here that showed an insert with a large radius and looked pretty thick. I remember the guy said it cut interupted very well. Can anyone tell me what that insert was or recomend one Thanks.;)

Black_Moons
06-28-2011, 05:16 AM
Try looking into 'softer' more durable carbide, Like C1 or C2 grade (or equvilent) for interrupted cuts in hard material if your inserts are chiping quickly.

They won't last as long once the interrupted cuting is over, But it sounds like it should still be a vast reduction in inserts used, even if you do the entire job with softer inserts.

winchman
06-28-2011, 06:46 AM
Why not use a grinder to remove the bult of the material? Do it away from the lathe, of course.

PixMan
06-28-2011, 07:39 AM
You didn't specify just what size TCMT inserts you use, but just the same what you want is a good, TOUGH (impact resistant) coated grade that's meant for steels.

Among them would be Sandvik 4235 or 4225, Valenite 5635 or 5535, Kennametal 9225, Walter WPP30, Seco TP3000, and so on. With grades like that, the task is easy.

Here's an example of a good buy:

http://cgi.ebay.com/TCMT-21-52-UM-Carbide-Inserts-Grade-4025-SANDVIK-10-Pcs-/220803724530?pt=LH_DefaultDomain_0&hash=item3368ed74f2

A tougher grade, but higher price because this seller likes to sell individual inserts for higher prices:

http://cgi.ebay.com/TCMT-3-2-5-2-UR-4235-SANDVIK-INSERT-/190544806641?pt=LH_DefaultDomain_0&hash=item2c5d5b02f1

Rosco-P
06-28-2011, 09:49 AM
Before ruining inserts on an interrupted cut, did you try a HSS toolbit? I would have tried a brazed carbide bit before a $7 to $10 insert. Carbide isn't always the answer.

PixMan
06-28-2011, 10:29 AM
Before ruining inserts on an interrupted cut, did you try a HSS toolbit? I would have tried a brazed carbide bit before a $7 to $10 insert. Carbide isn't always the answer.

It true that carbide isn't always the answer, but you did recommend it. :D

Just kidding!

I use it almost everywhere these days because:

I have a lot of toolholders and inserts, and keep getting more of it.
I know what the geometries, grades, coating and chipbreakers can do.

The total expense of having a wide variety of toolholders and a range of inserts not something the average home shop machinist can afford (or even store), but that's no reason one can't learn about it. It can pay off handsomely to have a few select tools to accomplish certain tasks that HSS or even brazed carbide has trouble handling.

Rosco-P
06-28-2011, 10:45 AM
The total expense of having a wide variety of toolholders and a range of inserts not something the average home shop machinist can afford (or even store), but that's no reason one can't learn about it. It can pay off handsomely to have a few select tools to accomplish certain tasks that HSS or even brazed carbide has trouble handling.

True, very true. Unless this was a paying job and a rush job, I think I'd start with a high speed bit first.

Fasttrack
06-28-2011, 10:57 AM
I do a lot of machining of welds - cutting welds on shafts like you. A couple weeks ago, I had to cut 4 14" sprockets off of a shaft. I chucked them up in a lathe and ground up a tool that acted like a trepanning tool (except that the workpiece was spinning).


Anyway, I use Rex 95 HSS or Tantung G. They are getting hard to find, but even a high cobalt (8%) HSS bit works great. You can sharpen them quickly, they handle interrupted cuts great and they are cheap. Although I work at a reduced RPM from carbide, I found out very quickly that the money I was saving in inserts and the time I was saving not having to replace the insert every few minutes made the HSS a better choice. After I get through the weld (or at least get it smooth), I swap out holders for an indexable tool holder and bump the rpm back up. Then I'm back at the races.

If it's a personal project, I just stick to HSS. I really like it better, even though it sometimes takes a little longer. On the other hand, with a big lathe, I can take .5" off in a single pass with HSS. I'd hate to try it with carbide. If I've got a job that requires bulk material removal like that, I pull out the HSS again.

Good luck! At least MIG welds don't have much danger of hitting a nasty and abrasive slag inclusion! ;)

Boostinjdm
06-28-2011, 05:15 PM
If you take the "skin" off the MIG welds with a grinder first they will cut a lot easier. It can be as hard on tooling as mill scale or rust.

mike4
06-29-2011, 06:06 AM
If you take the "skin" off the MIG welds with a grinder first they will cut a lot easier. It can be as hard on tooling as mill scale or rust.
Thats the quickest way to save inserts , I machine mig welded shafts and plates at times and have found that a grinder will save a lot of time if you are careful to smoothe out most bumps.
The carbide bits /inserts will take interupted cuts if only light cuts are taken until most of the uneven surface is gone.
Michael

PixMan
06-29-2011, 07:15 AM
Thats the quickest way to save inserts , I machine mig welded shafts and plates at times and have found that a grinder will save a lot of time if you are careful to smoothe out most bumps.
The carbide bits /inserts will take interupted cuts if only light cuts are taken until most of the uneven surface is gone.
Michael

This is exactly why I stress choosing known, quality carbide if you're going to bother. Today's carbide insert technology has the ability to take abuse that it couldn't 5 or 10 years ago....if you choose the appropriate tool. And I mean it is orders of magnitude better than carbide of old or cheap no-name Chinese import carbide.

About two years ago now there was a fellow trying to machine a forged crankshaft of a 4143 or similar alloy. Nothing he tried could get him through so much as a single pass of the heavily-interrupted cut on the counterweights. He had tried HSS, HSS-Co, and various carbide inserts he had. I sent him a particular Valenite CCMT32.52-PM5 grade 5635 insert that I had left over from a job I had bought them to do. Two edges (1 insert) finished the job for him. (I think it was 6 crankshafts.)

That's an example of a very interrupted cut, and applying the right tool to get the job done.

gftoolshop
06-29-2011, 07:36 PM
Thanks everyone!! I found the insert I'd seen earlier, (VALENITE CNGG120408SR9605 CNGP432SR #19145) But I am going to try the HSS. I've been told that a good size radius and little or no relief angle helps to. I did grind a lot of the high spots off, I'll weld it myself next time the guy put the gorilla welds on it and I think that was more of the frustration than cutting it LOL. I don't mind spending money on my tools after all they do pay the bills, and I just love tools to!!!!!! The more I have the more I can get done. I feel like I should be paying for this help you guys teach me more, faster, than any class I've taken. I'll be sure to share what I know and learn with all. Thanks GFTOOLSHOP;)

PixMan
06-30-2011, 07:41 PM
That's the one I used on the VERY hard weld of a heat-treated H13 plastics mold part. Worked fabulously. In fact, I gave one of the inserts to a friend of mine who also had a hard steel job with interrupted cut. At over 50Rc, here's what he got:

http://www.youtube.com/watch?v=GbelVwCwBX0

Here's what the insert looks like, though this one might be the CNGP431SR. Same 9605 grade.

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_0441-r-1.jpg

boslab
06-30-2011, 10:30 PM
i use a round 10mm CBN tool, single point in the lathe, 100 mm x 6 tooth in the mill, no problem yet apart from avoiding ingersoll tooling as the tip is not indexable so when you rotate you just guess by how far, sheel take mig /tig hardface with ease and with a nice finish
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