My New 8x18

Got my new 5" BTC set true chuck on the lathe and was playing with it a bit after getting it set up.

You can see in one of the following pics where I have a bar of stainless that I just took a 10 thou cut @ 1000 rpm on. The chips were golden/copper colored. I remember my machinist friend telling me that carbide likes to run hot and fast. Was I running a little too fast?

There were also minor marks in the stainless. More visual than anything, but I could feel them with a fingernail. I did have some cutting fluid on there, but it was what I could get on with a brush. Kissed the rod with some 600 grit and the marks disappeared.

The other picture is where I took the bar out and measured across the 3.5" cut to see what difference I had at each end. Curious as I was cutting out by the live center.

I couldn't see any difference with my old eyes and a caliper, so I grabbed a micrometer. One end (I don't remember which) was 0.9811 and the other was 0.9813.

OK, so now I'm really impressed with my little machine, as I have done nothing in the way of setup or alignment to this thing other than to use my iPhone app to level it to within 0.1 degree (the lathe is sitting on a solid wood door the previous owner of my house set up as a bench).

This after taking a 60 thou cut on the end to see if it would slow the motor down. RPM dropped by one when the cut started. Now THAT was a hot cut! :yikes:

NOTE: I don't normally get that aggressive, and probably won't again.

Maybe I'm easily impressed, or not, but this thing ain't bad for a little guy.

IMG_0348.JPG IMG_0351.jpg
 
.002 difference. Fantastic! Great looking machine.
 
Actually, it's .0002 difference. I had to look several times to believe it, and probably measured a half dozen times or more.
 
Stainless is interesting stuff. It takes a little getting used to but it always looks so nice...

On my machine, 15 thou is a good DoC that's productive and doesn't wear out the carbide too fast. If you consistently take cuts at/above 20 thou, it wears the carbide very quickly. When you get those white lines in the cut, it's a sign usually of too high RPMs and/or a worn insert. Oil won't really help get rid of those. Pay close attention to proper/suggested SFMs with stainless. There' not a lot of margin.

Ray
 
Hey Ray!

OK, probably both a dull carbide insert AND too high a RPM. Especially after that 60 thou cut.

So where can I get a chart that lists SFM or speeds and feeds for various metals? This would be a really big help. :D
 
Here you go... http://www.southbaymachine.com/setups/cuttingspeeds.htm

A 60 thou cut will put an instant end to a TNMG 21x; especially uncoated like yours. Also, shop around for some TiN or TiALN coated if you're going to do a lot of stainless. On a 2.5" diameter piece, you'll be able to cut about (roughly) 10 linear feet of stock if you keep your cuts around 15 thou DoC or less. Rapid degradation as you increase DoC beyond that. Good finish cuts happen around 8-10 thou. A round nose like a 322 is helpful with those finish cuts and a 321 is better for faster removal. KoolMist works wonders to keep the workpiece very cool and make the carbide last much longer. Holding tolerance with SS is tricky when it warms-up. It heats very thoroughly, holds the heat and has a fairly high coefficient of expansion.


Ray



wrmiller19 said:
Hey Ray!

OK, probably both a dull carbide insert AND too high a RPM. Especially after that 60 thou cut.

So where can I get a chart that lists SFM or speeds and feeds for various metals? This would be a really big help. :D
Click to expand...
 
Ray C said:
Rule #1. Nobody is forbidden for liking/owning any kind of lathe or equipment here. Old US Iron, Chinese, Taiwan... It's all fair game here. "Hobby-Machinist"... We use what we can get our hands on. If it's old and worn, people here will help you get it back on it's feet again. If it's new and has some imperfections, we help with that too...

The magnifier... Yes, I was serious but, I found it online. No need to trouble yourself. That looks to have a nice size lens on it. I have one with a smaller lens and need another for the shop.

Side Note: I am very, very annoyed because I found one distributor that caters to Medicare patients. They are selling that magnifier for over 450 bucks. Same thing online at different places is running $150-170. When I see abuses like that, I have visions of someone being beaten well past their point of begging for lenience.

Ray


EDIT: If you're serious about getting a 5" Bison, please call Matt using this contact info http://machinetoolonline.com/ and tell him the gang from Hobby-Machinist sent you. Matt is a great guy and he's a top tier Bison distributor. -Don't mention my name or, he'll charge you double (just kidding... he and I are Internet friends).
Click to expand...


Ray,

Can you tell us where you found the magnifier at? I also am interested in it? Its always a pretty broad search on google for this type of thing!

Thanks Bob in Oregon
 
Thank you for the link. Good stuff.

Carbide inserts are something else I have to learn. And quickly if I'm going to do much work in stainless. I don't even know what TNMG stands for, so I guess I had better get busy. Thanks for the suggestions: I assume you can get a 322 Tin TNMG?

Thanks again for everything. :)


Ray C said:
Here you go... http://www.southbaymachine.com/setups/cuttingspeeds.htm

A 60 thou cut will put an instant end to a TNMG 21x; especially uncoated like yours. Also, shop around for some TiN or TiALN coated if you're going to do a lot of stainless. On a 2.5" diameter piece, you'll be able to cut about (roughly) 10 linear feet of stock if you keep your cuts around 15 thou DoC or less. Rapid degradation as you increase DoC beyond that. Good finish cuts happen around 8-10 thou. A round nose like a 322 is helpful with those finish cuts and a 321 is better for faster removal. KoolMist works wonders to keep the workpiece very cool and make the carbide last much longer. Holding tolerance with SS is tricky when it warms-up. It heats very thoroughly, holds the heat and has a fairly high coefficient of expansion.


Ray
Click to expand...
 
Here's the gold standard of information about carbide terminology: http://www.carbidedepot.com/formulas-insert-d.htm

I just happen to notice the insert and tool holder you showed in the picture. If that is a 1/2" tool it's almost certainly a TNMG (see the link above) 322 or 321. The numbers are all explained in the link. If it's a 3/8 holder, it's most likey a 221 or 222. You'll need to look-up info that came with your tool holder to know exactly what size to get. -Most likely will be a 22x or 32x. The first digit is the most important and determines if it will fit in the holder or not.


Ray
 
I'd like to see how deep a cut you can take using cold rolled mild steel and a sharp HSS cutter. I don't use stainless unless I have to on the kinds of things I like to make.

P.S.: brown chips are fine for carbide.
 
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