304 Cutting questions

[jspangler]

Hi

 

The material is 304 stainless and is .5 thick with 5 through holes that need to be tapped. My laser guy claims he can hold .005, but some of the stuff he's done in the past looks a little sloppy on the outer contours so I want to finish them here. I've heard that 304 is a monster to cut after it's been cut with a laser. Any suggestions? What about reaming the holes and roll tapping them, will that work or should I just re-drill them?

 

I need to get the job in and out fast.

 

Thanks

 

John

[Tim Johnson]

I don't know about the laser, but 304 does work harden when tools get dull and heated up so my guess is that the laser isn't going to help much. 304 does roll tap nicely when the material is annealed (typically how you would buy it). Try redrilling the holes with a reground end mill instead of a reamer. If your holes are less than 1/4" run the drill size for 55% threads. Also chamfer the top side before tapping especially if there is scale on the surface.

[jspangler]

HI

Cool, that's the info I was looking for.

Eventually I'll get around to having them waterjet cut, but for now this is the quickest solution.

 

 

Thanks

 

John

[McRae]

Why laser cut the hole in the first place. As you need to go thru the hole anyway, the laser portion is non-value added. Skip it if possible, drill then form the holes.

 

Is there a reason to burn the holes out??

[Quickmike]

We have 3 lasers here and that is one of my pet peeves. I HATE working on laser cut holes. The heat affected zone i've been told gets to around 70 rockwell c. I think its only a few thou deep but it dulls tools fast. The best luck I've had is cutting 1mm. deep on any laser cut holes. I usually ask if we can drill and tap on the machine then I know everything is predictable.

[jspangler]

HI

Still trying to figure the best way to get this done. Skipping the holes with the laser is not a problem, and by having him blank out the parts, it will actually be cheaper than me buying the material in bars and cutting it so shape.

He suggested (as a few here have also suggested) that by oversizing the outer contour by .03, I will be able to cut "under" the hardened edge, and not wear the tools out.

 

We'll see...

 

John

[jeff]

I would just drill and tap at the machine.

If you have to machine the outer contour after laser,try conventional cutting.

We do that on some burnouts and it seems to make the endmills last longer on that hard crust.

[Keith Graydon]

+1 to Tim Johnson concerning 304. Its all true. especially the part about work hardening.

 

-KLG

[Guest CNC Apps Guy 1]

I'd also consider threadmilling. A little pricey up front but the number of holes you get from a thread mill... can't beat it with a stick.

 

JM2C

 

Hey John, you do anything with that lathe yet???

[jspangler]

HI

No KIDDING. Those threadmills are EXPEN$IVE!!

 

Actually, I finally picked up the chuck for it, and once I get it mounted I'll give you a call for the refresher course.

 

Thanks

 

John

[Harryman]

My $.02, drill and cut tap. Forget laser and ream.