machining 7-16 Stainless

[rztmartini]

hey guys. This is a question from my dad, hope someone can help.

 

we are trying to ream holes in some 7-16 alloy stainless steel (not 7/16" thick) and after the first one the carbide bit is ruined...any advice?

[BillZ260]

I use to be a machinist, it's been a while, but I'll attempt to help out here.

 

First let's start with what you did durring your first attemt that didn't work out for you. Can you be specific? What type of machine are you using, Mill or Lathe? What's the nature of the cut are you skimming the faces square or are you cutting a t-slot? What type of carbide tool are you using? An endmill, insert cutter, boring bar, try to be as specific as possible.

 

Now the material, I'll assume 7-16 refers to the chrome and nickel content in the stainless. I didn't find too much on it doing a quick goodle search. If has more nickle than 316, which should make it harder (I think). If it's anything like Incolnel, which I think is just a brand name for 718, it's going to be a pain unless you have the right equipment. READ RIDGED TOOLS.

 

I have lot's of experience w/ Incolnel 718. It's HARD and "gummy", take small bites at a high cutting speed and use LOTS of coolant. Interupted cuts will be very tough, so avoid them if you can. It will wear tooling fast, and once the tip is gone, you'll loose the tool and the piece if you don't get out of the cut ASAP. So, change tools often and keep them COOL. When I left the shop, we had just started experimenting with ceramic inserts, which held up much better and longer, but still need to be checked and replaced frequently. And again, interuped cuts with this material are hard on inserts especailly ceramic, which is even more brittle than the carbide.

 

Give me some more specifics and I'll see if i can't help more. It's been about 7 years or so since I did this type of work, but it was all i did for about 5 years or so. Hopefully I can push some of that knowledge on!

[Roostmonkey]

Ive never heard of that material and a quik search came up with nothing. If there is such an alloy, and it has similar properties to other std stainless's, then I will have to disagree with Bill's comment on high cutting speeds.Stainless should be machined/drilled at low rpm and with a fair amount of pressure. A coolant/lubricant should definaltey be used. The chips coloration will tell you if things are going well. If the chips are a nice silver ( no discoloration ) then your good. If they start to turn a goldish color your still ok. If they are blue/purple , your doomed. This means your turning at too many rpms and its getting too hot. This heat will work harden the spot and make it even harder to get thru.If this has happend, flip the part over and come in from the other side. You mentioned reaming. If by chance you dont have an existing thru hole and your trying to drill a hole larger than .25", you should put a pilot hole thru (1/8") prior to using the larger bit. Good luck.

[johnc]

I hate drilling holes in stainless. Slow with a LOT of coolant is the only way.

[2126]

John is correct......low drilling RPM, high feed rate (lots of tip pressure), and plenty- o-coolant. Heat from the drilling and or milling process will harden the SS, making it even tougher to drill. I deal with this situation quite often at work.

 

Tom

[MatMan]

Could he have meant 7000 series, 316 stainless???

 

See this page:

http://www.suppliersonline.com/Research/Property/result.asp?FamilyID=14&MetalID=1856&Chemical=1&Physical=1&Mechanical=1

 

The site is pretty damn useful as well!

[BillZ260]

rztmartini, how did this turn out?