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kowohtee
02-03-2002, 11:50 PM
I am very new at this,so thanks to all who respond.
How do I make a "clean smoothe" cut on S.S.?
I have a sharp carbide tool but all my cuts are a little "rough", not that smoothe "mirror like" finish. I think I am cutting it too slow. At what speed should I cut at??
Just looking for some simple advice.
Thanks all!!
TEC

KenS
02-04-2002, 05:14 AM
You're right--too slow probably. Carbide works better when driven fast and hard (in the words, more or less, of several posters here).

I learned it here, and have gone to HSS inserts when I need slow cutting in steel of most any kind. Grind your own, or have a look here: http://www.arwarnerco.com/ (also courtesy of one of the people here).

kowohtee
02-04-2002, 03:52 PM
Thanks KenS!!! I will try the HSS inserts.
TEC

snorman
02-04-2002, 09:26 PM
Spray some wd-40 or some such on it before turning. I've noticed this when facing various SS parts; it seems to cut well but ends up rough. Not sure what is happening here but the wd-40 cures it.

bspooh
02-04-2002, 10:23 PM
Now stainless steel is not hard,, it is tough..which means you need to get a good shear cut on it...use only positive cutting edges, stay ahead of the heat, and use HSS instead of carbide if you can, .Any time I cut stainless I try to use HSS because it shears better for me and I can get a better finish and longevity out of my cutting edge...Surface speed should be around 60...I am not saying that carbide sucks, I am just saying I personally have better luck with HSS...Hope this helps...if not sue me..(just kidding)

brent

Thrud
02-04-2002, 11:35 PM
kowohtee:
You are better off with the T-15 HSS Inserts that A.R.Warner sells. Their tooling is cheap too.

Carbide inserts are only better if you have a ridgid setup and you can muster from 100 to 400 SFPS - these speeds give a glass smooth surface finish wet or dry machining. Positive inserts are almost always better for what we do.

Brazed carbide bits are a poor choice for stainless - T-15 HSS works far better.

When you cut stainless it is important especially with 3xx series alloys to take at least a .oo3" cut to get below the work hardened surface skin. If you do not do this, the cut will look like crap. The rough surface finish that you mentioned is also an indication of BUE (built up edge), notched, fractured, or deformed cutting edge. Interrupted cuts should be avoided to help prevent this.

A good coolant mixed properly can make a big difference - I prefer the synthetics, some prefer soluable oil (goes rancid to easily). If you mix up coolant distilled demineralized water is the best choice - and clean your sump every time you change the fluid.

Hope this helps a little. Have fun but follow all safety rules (THE most important thing in this hobby).

Dave

kowohtee
02-04-2002, 11:53 PM
Snorman,Brent,and Dave...
Thanks so much for the reply. Your knowledge is greatly appreciated!
I took your "orders" and ordered the HSS inserts today from Warner. Those people are great to deal with. Very courteous and nice.
Thanks again guys!!!
I hope someday I am able to help as you have.
TEC

smoking joe
02-05-2002, 02:44 AM
I agree with everyone on the HSS.I use it for everything but cast iron.Just turned some SS crank pins for a locomotive using lard for cutting fluid and Dave they sure are shiney.

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kap pullen
02-05-2002, 10:00 AM
Stainless steel is a soft material, not a good wearing surface.
It's aperent hardness is due to a couple factors.

1. It is an insulator (compared to other materials). When you are cutting, or wearing on it the heat stays right at the cutting, wearing area.
This affect causes hardening, galling, the appearance of distortion, and accelerated tool wear.

You need to cut slow to allow the heat to dissapate within the part, or cut with a heavy feed to "out run " the heat in the part. In this way the heat is contained in the chip.

2. stainless is an abrasive material, causing accelerated wear in your tools.
Dull tools cause heat, causing workhardening
causing tool failure.

It,s a vicious circle.

Sharp tools, positive rake, heavier feed, and
some kind of coolant work best for me.

A shaper does a great job because the cutting area is spread out, less localized heat.

kapullen

kowohtee
02-05-2002, 06:59 PM
Boy am I learning now!!
Keep it up guys!!
TEC

Thrud
02-06-2002, 02:45 AM
Joe;

Are you trying to tell me they are shiney? I should hope so! It would suck if it wasn't - sort of a waste of all that Chromium otherwise...

Dave (I must have been a crow in a previous life...)

SGW
02-06-2002, 08:20 AM
Pay attention to the "sharp tool" note in Kap's posting.

I turned some 303 stainless a few weeks ago. To get a decent finish, I first ground the toolbit on a fine wheel, then stoned the edge with a white Arkansas stone to get it wicked sharp. Cutting oil helped, too.

C. Tate
02-06-2002, 09:28 AM
I run this stuff everyday for foodservice equipment mfg's and I have found that not all stainless steels are created equal. If you have 303 stainless you can run it like 1144 steel if you have 304 or 316 which have less carbon and more nickel you have to slow the speeds down. I tend to agree with those who suggest Cobalt HSS tools to cut in the home shop. You need a very sharp edge to do a good job. Stainless is not hard as many think, it is no harder than many alloy steels we cut, the rockwell hardness for 304 ss and 1018 crs are the same. The nickel gets sticky when heated and causes edge buildup on your tools this causes your cutting tool to become a rubbing tool and then failure occurs. A wickedly sharp tool as has been suggested and coolant of some sort is the best way to attack stainless.

The way your tool is ground could be part of the problem use a nose radius some where between .015 and .030 and feed about .006-.007 and you should get a good finish. You should run about 50 sfm on all 300 series stainless steels except 303 which you can run somewhere around 70 sfm. These are starting points you may have to adjust according to your machine and application.

kowohtee
02-06-2002, 10:07 PM
Thanks again gentlemen!!
TEC