[1cnchogger]

Having trouble with a 304 stainless 3in by 3in extrusion 60 in length. I have to face it and tap 3/8-16x40 times, they go in .7 in depth . The hole size is up to 9mm just to get that many. I'm running 300rpm with feed of 18.75ipm. I have rigid tapping on my VF3 Haas mill. I have been using a greenfield roll tap with no luck(might get 30 holes). I have iscar 3 in facemill that eats through the 928 inserts, lucky they are four sided. I only have to take 1/16 off face. Question-Has anyone had any luck with tapping s/s in this way, or should I forget about the roll form all together. Also, anyone using anything different to face?

[mark c]

What is your speed and feed for the face mill? What type of oil/coolant for the tap? Spot drill or center drill?

[cdlenterprises]

OSG Hypro High spiral taps. Those have always worked well for me in 304. I haven't had much luck form tapping. Try IC328 for your facemill @ 300 sfm.

[1cnchogger]

speed and feed for facemill is 650 rpm feed of 10.00ipm. I tried speeding up but burned out quicker. I've tried the iscar 328 not much of a change. I think the problem is I'm conventional milling with a 3.00" cutter. I'm trying to get in a 6.00" button cutter to see if climb milling will make a difference.

[1cnchogger]

syntillo 9954 is what I'm running for coolant. Tap seems to be shattering. It's funny the previous holes are fine. No sign of fatigue until it breaks. I am centerdrilling.

[VMC_Jeff]

We machine alot of 304 SS and have found it is one of the least predictable material to machine. One week we get material in that machines great, the next week it machines like granite. I'm sure it has to do with the nickel or chrome content varies from batch to batch. Just my opinion.
We found the Iscar 28 or 328 grades to hold up a little better than the 928. Thread forming usually only works in shallow holes. In the deeper blind holes we use a reverse spiral emugee ticn coated tap. Drill as large as you can and still pass inspection. Even then we found there is usually no warning before they shatter.
Good luck
Jeff

[cdlenterprises]

Sounds a little high on the rpm. I generally try to run 300 surface footage which would calculate to about 400 rpm for a 3" cutter. You have to "push" cutters in 304 or else you'll work harden the material. Try to reduce the rpm to 400 rpm or so and leave the feedrate. As far as the tapping, have you tried a tension and compression holder or a tapmatic tapping head? They tend to be a little more forgiving should you hit a hard spot in the material or bind up the chips. Keep us posted...

[Hogger]

We tap a lot of 304 in the lathe and mill, we use spiral flute USA made taps and run them at 25 FPM but haven't had much luck using coolant, we have to use Castrol Moly-Dee cutting oil to get the taps to live, but can get 1000 or more 3/4-16 by 1.5 in. deep threads done on a single tap, we use forming taps on 3/8 and smaller taps but still have to use Moly-Dee to get any life out of them.

[1cnchogger]

Found solution to facing problem. Iscar rep brought me in an octagonal insert. I have been using it without indexing once. I would have gone through a pack of 928's. Cutter is a ISCAR 3in HOF D3.00-5-1.00-R07 inserts are OFCR 07T3-AEN. Unbelievable difference. I think it may be the clearance allows the chip to be expellend rather than drug along the face. I'm still looking into the tap and drill. Thanks for advice on holders, speeds and fluids.

[jackson]

also dont use coolnt when facing

[protopath]

Try a spade drill, we have pretty good luck with those in 304. 304 is like fossilized bubble gum, hate that stuff. We also do not rigid tap it, we use a tap head and never use a form tap.

[1cnchogger]

What kind of spade drill are you running? Make, size, speed, feed etc. I need to drill 8.75mm for the form tap. Might try compression tapping head now. Much appreciated

[protopath]

TA SHT FLNG is what is on them. Pretty much a generic spade I guess, we use different sizes using inserts from 1.5 in. down to .3125 or so. TiN coated HSS inserts.

Let me take a look today at work, I'll be home tonight after 9:00 central and can give you some better numbers.

[jackson]

TA SHT FLNG

LOL!!!!! that sounds like what happens at my house when i pi$$ the ole lady off!!

[fizzissist]

I just got through doing about 400 8-32 and 200 2-56 holes in 304SS with our shiney new Tapmatic rigid heads and rigid tapping in our Fadal, with plain ole coolant....not a single failure, and the tap is good enough to throw into the drawer with the rest of the 'ok for non-production' taps.

We've had very good luck with the OSG HyPro series taps.

One thing I found with our face mill in 304 is that I really do get much better tool life milling dry. Been using a 2.5" dia 5 insert mill w/Sandvik 2030 grade inserts. Find for us that we generally get good results running about 2/3 their recommended speed.....

Like VMC_Jeff said, 304 has been all over the map for us too, and we do mostly 304 or aluminum.

[jackson]

When it comes to taps i have to agree OSG-HYPRO and EXO are hard to beat
and i dont mill much 304 but i turn alot of it and i always turn it dry till my finish pass and i find that the coolnt just makes the finish a bit better

[protopath]

Got to love that abbreviation huh? Boss loves it when you yell out "I need TA SHT FLNG."

Sorry but I was wrong, smallest spade we've got is 3/8.

AMEC (or ACME - weird logo) T-A is the brand and make. Y series spade is the smallest. Looked it up in the catalog and 3/8 is the smallest insert on the smallest spade. If you could find a spade that small 75 sfm at .003 would probably work. We use the standard 130deg. spades. When we drill with cobalt or m42 in 304 we do grind a flatter bit, probably around 130 or slightly steeper, that is just eyeballing it and freehand grinding.

I think they make Iscar Cham drills small enough and you might try one of those. Those are some tough drills.

[1cnchogger]

Thanks for checking that out. I'll ask my ISCAR rep on the Cham drill.

[jackson]

Got to love that abbreviation huh? Boss loves it when you yell out "I need TA SHT FLNG."

Sorry but I was wrong, smallest spade we've got is 3/8.

AMEC (or ACME - weird logo) T-A is the brand and make. Y series spade is the smallest. Looked it up in the catalog and 3/8 is the smallest insert on the smallest spade. If you could find a spade that small 75 sfm at .003 would probably work. We use the standard 130deg. spades. When we drill with cobalt or m42 in 304 we do grind a flatter bit, probably around 130 or slightly steeper, that is just eyeballing it and freehand grinding.

I think they make Iscar Cham drills small enough and you might try one of those. Those are some tough drills.

Yes the cam drills are great im slowlly geting it where that is all i use .295 and up and so far i havent found anything they didnt like cutting ,

[protopath]

Just got to make sure you feed them hard enough. I've noticed that with the new style that the through coolant holes are much smaller and tend to clog easily, so watch out for that.