NMG carbide negative rake inserts for SB9

[Carlos]

Hi guys, I have recently bought my SB9. Love it.

Now, I've read on Practical Machinist that NMG carbide negative rake inserts are not working for SB9. Is that true?

I have all this old tooling that came with, but I would like to use more modern tooling on it as I do not know how to sharpen and maintain old tooling.

What do you say?
Can I sue rake inserts?
I guess its yes, what do I need to consider using them?
Which ones work best - where to buy?

Thanks for the help.

[DavidR8]

I have a South Bend 10K and use HSS tool bits almost exclusively.
I also have some insert tooling with CCMT and DCMT inserts.


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[GlennW]

I'd definitely say away from negative rake inserts on that machine. You need horsepower and speed to make them work properly.

CCMT would be a good choice if you just can;t use HSS tool bits.

[DavidR8]

@carlos you would do well to learn to sharpen HSS tools.
As GlennW said, carbide is really intended for production environments where machines have the hp to take deep depths of cut at high speeds.
On my SB with a 1/2 hp motor using a sharp HSS tool I can take a .020 depth of cut in 12L steel no problem.

[Harold_V]

Hi guys, I have recently bought my SB9. Love it.
as I do not know how to sharpen and maintain old tooling.

What do you say?

What I say is you would be far better off learning to deal with HSS cutters. If you don't, you'll struggle with any choices you make, because you don't understand how or why a cutter works. Without that knowledge, you simply can't make reasonable decisions, nor will you understand why a cutter isn't performing as you hope.

Grinding HSS toolbits for lathes and shapers/planers isn't difficult once you understand cutter theory. Insert carbide tooling is a poor replacement for that knowledge, especially on home type equipment, usually lacking in rigidity and power. Do yourself a favor and start grinding your own cutters. You'll be glad you did.

H

[spro]

I don't want to talk over you, just a conversation. The OP mentioned "old tooling" and that refer to exactly what you said. The South Bend 9 is sturdy enough but has a narrow compound slide. The saddle slide is not meant for using those type bits. Further backwards we can surmise things about the 9A, 9B or 9C. Around 1950 They had Timken bearings. That raised what could be done with them and collets and closers of different type.
The deal is that the point of stress should be in the center of the saddle. Not stray too far from that. It comes back to the hated lantern toolpost with the Armstrongs and well ground tooling.

[Carlos]

Thanks for the answers.

I read a lot about this and understand now that there is a negative rake and a positive rake.

The negative is for big equipment - while the positive rake works for SB9 and also other smaller lathes.

@Harold_V: Yes, agree, you right ... however, my time is limited and if I can substitute knowledge with technology (what everybody does in our days), then I will do it. I just have too much other things going on. But again, yes, I wish I had the time. But I keep on reading and get the idea.

I have now ordered at Banggood 7pcs 12mm Shank Lathe Boring Bar Turning Tool Holder Set With Carbide Inserts. Its cheap and if it works it will save me lots of time. I have seen and read that they work well for small lathes. So I will see.

Thanks for all your feedback.

[BadDog]

As others advise, stay away from negative on small machines. And plain bearing lathes should probably just forget about carbide for most turning purposes, unless carbide is necessary due to abrasive material, or (unlikely on an SB9) turning hard material. Yes, you can find some that will work, and work well, but that's like driving an heavy truck in downtown NY. It may get it done, and sometimes needed for purpose, but in general you'll find other vehicles far more useful.

Read Harold's treatise(s) on grinding HSS tooling, and making a grinder well suited to the purpose to make it oh so easy (and fast). You'll find those "sticky" at the top of the lathe forum (I think). And the best thing about HSS is, once you get the hang of it, you can make any type of cutter you need. That includes special stuff like snap rings, o-rings, arbitrary fillets, trepanning, threading (v, acme, etc), boring (including threading and grooves), and the list goes on as far as your imagination or need will carry it.

Then find some decent HSS. I would suggest NOT the cheap stuff you can get at HF, or from suppliers like Shars. You'll also want to become somewhat knowledgeable on the different alloys/names/etc. Doing so, I've picked up some great NOS Rex, Latrobe and CLE among other premium bits brand new, some in a complete box, for way less than $1 per bit.

This is my HSS bit drawer (with some carbide also starting on the right). I no longer even look for more, I'm set for life.

[Harold_V]

If there's an interest in my posts on grinding HSS, grinding wheels and grinders, they are found in the Resource Library, not the lathe forum. They were all stickied some time ago due to several requests, so they're easy to find, in the few posts immediately after the Announcements.

H

[BadDog]

Sorry, my mistake on location. Well worth the read.