machining 304 stainless steel

[pauls]

I've got some exhaust manifolds I have to CNC from 304 stainless. I've gone through the machinist handbooks and it seems you need feed rates of .2/min. Any suggestions on tooling or lube to speed up the process? I have a feeling HSS bits will dull quickly so I was thinking of carbide. Thanks
Paul

[Konrad]

Feed Rate all depends, on what tooling you are using, Carbide, HSS, long short, depth of cut, how many flutes, riggedy of your mill etc.
I sometimes go as fast as 16"min.or .2" min.
See, if you can mill {rough out with a roughing millingcutter first, the 304 is not bad cutting, in the 3....series, just make sure, you are not overheating, lots of coolant.
Konrad

[themachinest]

Don't dwell, and use enough feed so you don't work harden the material. Use lots of coolant.

[ghyman]

I've had excellent luck with either cobalt or carbide drills and mills, but with TiALN coating... it's a little pricey, but it eats through 300 series like nothing else!
Try 50 SFpM, and about 1.5-2.0 Ipm.
And, as stated by everyone else... COOLANT!!

[whiteriver]

Cuts like butter if you go fast enough. Cut it to slow and its like cutting a diamond with a butter knife. Will work harden in less than a second.. Keep the feed constant.

Donny

www.whiterivermfg.com

[Halfnutz]

OK, coolant I get the message. I would love to flood everything I do. I just bought a round collum benchtop and since I do a lot of work with steel I am having problems with overheating. I cant figure out how I am going to deal with this in the long run. Any ideas on a benchtop flood system?

[themachinest]

Halfnut,
Have you tried a mister? I have a couple of machines that don’t have flood capabilities and I use misters. I like the type with two nozzles and a reservoir with the controls on the reservoir. I have one called “Spray Master” that I like well enough.
There are enough cutting fluids on the market to confuse anybody. I have found one called “Trim Sol” that I like very much. I use it in my CNC for flood but I also use it for my misters. Mix it about 5 to 7 parts water to 1 part “Trim Sol” and use enough air to evacuate the chips and enough fluid to make things wet, maybe not dripping but wet. This will help you with your steel cutting and heat problem.

[Halfnutz]

Thanks for tip. No I hadnt thought about misting, but it sounds like the way to go. Until now my milling has been limited to a little Homier 12 spd. which is a great little machine, but not capable of creating the heat and piles of swarf that the 33686 does. What about a kiddy pool, some shower curtains and a pond pump? (just kidding)

So about fluid choice,, is oil a thing of the past? Everyone is using water based coolants now? Is oil limited to threading? (I started out with a lathe and oil has allways been sufficiant).

[ghyman]

I have become a "swiss guy" over the past 8 years; there seems to be nothing a M32 can't do (shameless plug for Citizen!). As such, I have had the opportunity to run oil (in ALL my swiss machines), and water-soluable (in everything else).
I have found better tool life in the swiss machines, but I think that is primarily due to the rigidity of the machines. I think the oil is also a factor, but I can't swear to it -- the right water-soluable coolant is pretty good too!

As far as a mister goes, I think it depends on how big of a mess can you stand... My experience is that a water-based coolant in a mister leaves a nice 'scum' on everything around the area after a month or so... water evaporates, and leaves the mung behind. A light oil mist will work just as well, but the area needs mopped, wiped, etc. fairly regularly. (But everything is all nice and shiny!! )

On a small mill, I bought a small pump and reservoir (2 gallons), and had pretty good luck with a "duct tape and bailing wire" plumbed flood system for under $100.

[JRoque]

Hello. I don't know much about metals but I believe 304 stainless steel does not harden with heat. I just finished doing quite a bit of 304 cutting and had no problem using cheap HSS cutting tools. I did take very small cuts however. For 'coolant' I used Tap Magic and water on a spray bottle. A quick squirt once in a while worked.

I have heard good things about this system. I don't have one yet but plan to get it soon. This one also looks good.

Julio

[BigDaddyG]

Halfnutz,
In my never to be humble opinion, Flood is far better than misting, especially for the home machine type guys. I picked up my flood system and coolant from Enco (www.useenco.com). The flood system was around 80.00 or so (been a few years - 5 gal tank, pump, tubing and drain stuff). I saw that Harbor Frieght has one that sells for 30 or 40 bucks. I used the water based coolant (ValCool). It does not funk up the garage with mist either. There are drawbacks to both types. You will have to drill a drain hole in the table top, use as large a drain as you can get in it. You will want to do a "splash guard" around your machine but it does not really take much.

Again, flooding will net you cooler parts. Better in the garage or basement than misting and the cost is a wash. Good luck!
Regards,
Glen

[Halfnutz]

BigDaddy,
Check out this simple settup from about 5-10 dollars worth of misc. parts. It works great and I can set it to flood or mist. Do you leave water based coolant on your machine or do you mop everything dry when done? I know its suposed to be okay, but something about a water base emulsion sitting on my pretty polished table just bugs me. Have you ever had any problems with corrosion or rust?