What's a decent cut for a 9x20 import?

Larry$ said:
There is a problem with terminology. You can increase torque with gearing but you can not increase power. No matter what you do, you can't get more "power" out than you put in.

Metal removal often has a sweet spot where DOC, Feed and SF/M all combine for the particular tooling you are using. Sharp tools cut freer but dull quicker. My carbide inserts, that are for aluminum, cut steel beautifully but dull relatively fast. The nicest thing about them is being able to take a very fine cut in steel much like my HSS tooling. I can even sharpen the "for aluminum" carbide inserts a couple of times on the tool & cutter grinder.

Just play with the variables until you find what works best for you.
I've tested to see how much material I could take off in a given time. Pretty amazing actually.
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The snip you quoted removed important context. You are correct in the technical sense. Electrical power cannot be increased. The power delivered; i.e., torque, can definitely be multiplied by gearing. The net result is the same; the workpiece has more force turning it.
 
One of my criteria for DOC wouldn't fly in a commercial shop. If the chips are flying very far, as onto me and very many of them going to the floor, I reduce the DOC. I can afford to take a little longer to get to the desired OD since all of my work is donated as a volunteer anyway.
 
David2011 said:
One of my criteria for DOC wouldn't fly in a commercial shop. If the chips are flying very far, as onto me and very many of them going to the floor, I reduce the DOC. I can afford to take a little longer to get to the desired OD since all of my work is donated as a volunteer anyway.
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Funny little story. The place I am at now the people take slow light passes. I had a chunk of CRS that was 8” dia. I had to turn one se toon down to 4”. I was taking .200 /side passes with coolant. They started complaining about all the smoke and chips flying. I was told to dial it back.


Cutting oil is my blood.
 
Huub Buis said:
Some years ago, I made a video to show the cutting capabilities of my mini lathe. It was (and is) impressive.
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He uses a depth of cut of 0.5 mm, which is about 0.020" The feed is heavy, which is apparently what you should try first.

(I'm not buying the first half, in which he claims to take 1 micron passes. Gotta see the micrometer to believe that.)
 
Janderso said:
That will take some patience!
I take .050" or more per pass.
I have a 15" x 50" lathe with 7.5 hp though.
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OK, thanks, that's inspiring. I've been pushing here and there. I had a bunch of good cuts at 0.040 and some at 0.050. At some point I had some trouble with a chipped insert, which resulted in a lot of chatter. Then the replacement insert chipped on the first pass but I didn't notice. Took a while to figure out if it was the depth of cut, insert, or just the diameter I happened to be cutting at the time. Chips are silver when cutting near the center (0.625) but fairly colored as I approach 2.280".

Since then, I've started hand-sharpening the inserts. They're CCMT-060204 which is just a little guy. I've been touching them up on a cheap metal-bond diamond stone. They hold up fairly well, maybe better than factory for heavy cuts. It's not exactly the same as off-hand grinding HSS tools but it's not completely different, either.

I'll push toward 0.050 again tomorrow, with freshly honed inserts.
 
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