Embarrassed to ask, but haven't found an answer to this with pictures - carbide angles relative to workpiece

[WobblyHand]

Have an LMS mini lathe. I ordered carbide bits with it, since I didn't really know what I was doing. So there are three bits in this kit. These are triangular indexable bits.

Sorry about the focus, I thought it was on the bits. How are they used? Starting from the tool on the right, we can mount this on a QCTP. For non facing, is the bit relative to the workpiece mounted like the picture below?
What should the angle be relative to the length of the piece? 90? I've read conflicting things, or I'm confused. So I'm asking for help. There are a lot of pictures (on this site) on HSS tool angles, but I haven't found anything on carbide tool positioning. As you can see from the 2nd photo, the facing that I did was ragged at best.

 

[mikey]

Turn the tool so that the cutting edge on the left angles toward the chuck by about 5 degrees or so. That will work of both facing and turning. That tool has a huge nose radius and the cutting edges are pressed, not ground, so it will require relatively heavy cuts to work well. I cannot tell how big the tools are but it is possible that AR Warner might sell T-15 HSS inserts that would work better on your small lathe. Maybe check with them?

 

[WobblyHand]

Thanks. It isn't a very good tool for light cuts at all. Even at 5 degrees. I assume you mean a 95 degree included angle between the length of the workpiece and the length of the tool. The tool has been kind of frustrating. I'll check with AR Warner to see what they have.

In the meantime, I've been following the thread on grinding your own. Have the tool steel and keystock. Waiting for the sample example bits (they are in the mail), just trying to figure out the grinder part.

 

[mikey]

Yeah, turn the tool counterclockwise 5 degrees.

HSS will work much better on your little lathe. It will rough better but more importantly, it will take very fine cuts with ease so you can come in on size. I know that model tools thread is a monster but read through it if you can; there is a lot of good information there.

 

[WobblyHand]

These are TCMT 2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC. 3/8 shank. So 1/64" radius. They chatter a lot more than I'd like. Last time I checked, they were on center, how close to center do you need to be? Does the ruler trick work for these carbide tools?

 

[WobblyHand]

I've read that entire thread end to end Thanks for starting it and keeping it going! It's been very educational and helpful.
Still hope to be able to use these carbide bits for something...

 

[BtoVin83]

yes, it should have an angle. What that angle should be let your imagination take hold. Depending on the operations I'll run them angled right or left or strait in. Negative rake tooling is pretty forgiving not like positive rake HSS

 

[mikey]

These are TCMT 2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC. 3/8 shank. So 1/64" radius. They chatter a lot more than I'd like. Last time I checked, they were on center, how close to center do you need to be? Does the ruler trick work for these carbide tools?

Should be dead on the centerline of your spindle. Yes, the ruler trick will work for now.

 

[Cadillac]

These are TCMT 2-1.5-1 carbide inserts: 0.093" thick, 0.015" radius, 7 deg clearance angle, 0.250 IC. 3/8 shank. So 1/64" radius. They chatter a lot more than I'd like. Last time I checked, they were on center, how close to center do you need to be? Does the ruler trick work for these carbide tools?

Look at tcgt 21.51 inserts they will work much better on your lathe. The inserts you have are molded with a large nose radius,these are ground and sharp.

 

[Mitch Alsup]

Rule of thumb:: the smaller the nose radius the light the load on the lathe.

Rule of thumb:: negative rake angles are for very hard material; while positive rake are for soft materials.

So, TCGT are a positive rake version of the TCMT, and look for a nose radius of about 0.008 or smaller

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