Trepanning 316 ?

Need to make some parts with a .900 hole 1-3/4" deep with a 5/16 post sticking out a 1/2" in 316.

They asked me if it was possible and I responded that most things are possible, just depends on how bad yuh want it.

We have done this same thing in alum, but this will undoubtedly pose a challange. (and of course they want them two weeks ago.)

Anything commercially available that would be recommended?

I am assuming we will be dooing some custom grinding...

Iscar makes a pretty extensive line: http://www.iscar.com/Ecat/products.asp/app/54/mapp/TG/GFSTYP/M/lang/EN

RAS

Ox,

I don't know of any off the shelf tool to do this. You need a special made hollow mill. It will look like an end mill with a hole in it. Kind of like one of these "annular cutters" http://www.hougen.com/cutters/cutters_index.html

In 316 you are going to have to peck a bit which can be a problem due to re-cutting chips. Lots of coolant or even high pressure coolant will help.

I did one a while back where the trepan had to be threaded. We sent out a tap and had a hole burned in it. It was pretty thin walled by the flutes when it was done but it worked.

Maybe something like the rig at the bottom of this page.......

http://www.iscar.com/ProductLines/PDF/BasicApplicationswithVariousTools_40.pdf

Course that's probably a 4" hole just to make things look easy

Ox -- is that 5/16" post sticking out 1/2" from the top or the bottom of the 1-3/4" deep hole?

A trepanning tool would definitely be handy for this situation, but desperate times call for desperate measures. You could very well mill this feature with a 9/32 (.281) endmill. You're going 1.75 deep, so that's just over 6XD for the spaghetti string endmill. I can't imagine it being much fun!

The top of the tit is 1-1/4 down the hole. I realized later that it kinda sounded vague after I posted it - but thank GOD it aint THAT bad! LOL!

Picked up some Zig/Zag and we're gunna roll our own it looks like. (wink icon here)

Hope to git to that part yet this weekend. I am hopefull, but we're rolling a few toys in anticipation of it not going quite as easy as the alum that we run like it. LOL!

<grin> Yeah, had me wondering. Still a tough job. The other way I was thinking it'd almost have to be made out of two parts.

Ox,

Let us know how it goes. We've had some swarf trouble with some deeper trepans in hardened 4140. Ended up doing a small plunge and cross feed on an angle in Z- and back again and so on. Was much wider groove than .9, but did the trick. Then again, the 316 chip won't break the same as the hard 4140, but still it's deep. Have fun.

Broke toy #1 as soon as it hit the metal. I knew it was weak lookin' as soon as I picked it up - but had to try it.

New design is in the werks.

Will have many $ invested by the time we have werkable solution... But that's life eh?

If it was easy - everyone'd dooin' it.

Wonder if you could EDM a hole thru an endmill and burn in some slots between the end teeth so the hole looks like a splined hole for the first 3/4" or so down at the business end. That would allow your coolant to feed down thru the center of the cutter and flush the chips back up the flutes. The OD of the flutes could be ground undersize for all but the last 1/2 or so to help the chips get out without dragging and chewing up the ID of the bore. If it worked, the tool could be resharpened with just an end grind of the teeth that wouldn't screw up your OD size on the tool. Something like that would give you the torsional and column stiffness to feed a tool like it needs to be fed in 316, and that's something that ain't likely to happen with any single point tool, regardless of its configuration.

I had a job where I had to take about .090 out of the thru bore on about 5000 forged SS 1" pipe tees. 50/50 mix of 304 and 316 parts. 3" long thru the hole. Used 6 flute HSS EM's reground to size, and figgered I'd be lucky to get 100 pcs between regrinds on the end teeth. Ended up I could really feed the hell out of the tool, and got 800 plus parts between regrinds. Cutters were Niagara, which I've always found to be really first class in their HSS stuff, so I'm sure that helped cutter life. Anyway, with carbide I think you oughta be able to get some real good tool life and production speed as compared to a single point that's gonna be about as stiff as last nite's spaghetti noodles.

Of course this is essentially the same hollow mill Swiss mentioned up above, but it might be cheaper if you can modify a standard instead of making a special from scratch.