QCTP progress and problems

[wawoodman]

I'm starting a new thread, and throwing myself before the bus of the collective wisdom.

I have ground a new cutter, based on the discussion in the other thread. It works, after a fashion, but I know it can be better. I have attached a picture of a test turning. As you can see, the finish is not very good at all (and that may very well be operator error.) When I kept to a .010 DOC, I got nice long, very tight curls of swarf. I laid a ruler on the pile, to give you an idea of the scale.

Settings are: 434 RPM (the middle of the cone pulley) and .0074 feed. When I tried it at the high-speed pulley, I got lots of smoke and blue curls.

I have also attached pictures of the cutter. It's 5/16 HSS. The leading edge is ground at about a 15 degree angle. The tip is ground back at about the same. I can see no place that the bit is rubbing. The top is flat. The QCTP is at 90 degrees, and the bit is going straight in to the work.

If anyone can tell me where I've gone wrong, please do! You won't hurt my feelings.

If you would rather talk than type, I'm at two oh six, five two three, nine six two eight.

Thanks a heap,
Mike

View attachment 95388

 

[jgedde]

What's the material you're turning? If it's steel of some sort (which it looks like), don't be dissapointed if you don't get a mirror finish... When turning steel, the chips have a habit of getting in the cut and galling the surface. Cutting oil will help somewhat here.

Also, I find that a sharp cutter (small radius) and fine feed gives the best finish on steel. I tend to think that radius is a bit big. Also, some back rake (top rake) would be better than the flat top you have.

Try some aluminum to practice your cutter grinds...

All in all, despite the small pictures, the finish doesn't look bad. Can you attach a closeup of the finish?

John

 

[jumps4]

ok i'm a novice also but i only use 7 degrees relief and i grind the top that way also not flat. are you checking your tool height to a center mounted in the tail stock you also may be too high
and if that is hot roll steel that can also be your problem. some of it turns like gum I quit trying to turn hot roll in my 9x20 it just would not cut well for me. I'm sure someone will give you a lot more help
steve

 

[wawoodman]

Material is cold roll steel. The finish is rough to the touch.

 

[wawoodman]

I certainly don't want to start a fight, but the cutter is flat because both Bill Gruby and tomg recommended that I try it that way (unless I misunderstood them, in which case, my bad.) I'll put a little rake on it, and try again in the morning!

 

[swatson144]

Pretty much looks like what one gets with 1018 CR . Before getting all twisted around the axles over the lack of finish maybe scrounge some other materials to try. It is my findings methods that finish well with 1018 CR don't necessarily work well with other material vis a vis. Some materials are hard to get a bad finish with 12L14. 303 SS, 6061 AL, 4140, etc 1018 ain't one of them.

If I am having to use it I have resolved to rough in and finish with a shear type finishing tool and not blue chips to finished size.

Steve

 

[wawoodman]

3/4 inch. Starting with 1".

Steve, that's a great point about choice of materials. Right now, I'm just going to the metal store and going through the cutoff bins ($1 per pound, for CRS.) But, until I know more about what I'm doing, I should probably be willing to pay for the more friendly metals.

On their site, in the Free Machining section, they list the following:
Aluminum 2011-T3, round and hex
Brass C360 flat, hex, round, and square
Carbon 12L14 round
Stainless T-303 round and hex

For work on the mill, I guess I can stay with the cold roll. Is there anything else you can add to that list?

 

[wawoodman]

Thanks, Frank.

Remember that I'm using a QCTP with a HSS bit. That's what led to the discussion about top rake, and some of the guys saying that it wasn't needed.

If you could post a sketch of what you're describing, it would help a lot!

 

[swatson144]

Yeah but 6061 you can get at a big box home center and sometimes the small mom n pops.

Steve

 

[wawoodman]

Yeah but 6061 you can get at a big box home center and sometimes the small mom n pops.

Steve

That's only an issue on weekends. I only live 10 minutes from Online Metal, and they have a 2 hour will-call, or, I can just walk in and dig through the cuttoffs.