T slot cutter in stainless

Hi all,this is my first post from the sunny Gold Coast in Queensland Australia. I jumped back in the trade about 7 years ago after a 25 year break & im having a ball lol.i was wondering if I could get some advice on milling a 25mm T slot in some stainless.i have a 15mm clearance slot at the top & I originally thought to take that size all the way to the bottom of the tee but now I think I should have the cutter cutting on the full dia. I hope that makes sense,anyway any advice would be welcome
Cheers Pete

I think I'd machine the 15mm all the way to the bottom first. This should enable you to use a heavier feed rate with the T cutter. Run the cutter slow and feed it as aggressively as you can. You need a flood of coolant with good flow to minimize chip recutting. I hope you've got an enclosed machine to contain the mess! Good luck.

To expand on HFD's answer, I'd even run the 15mm a few tenths of a mm into the base unless there's a critical strength issue, that way you remove some rubbing during the cut. I'd also like to use a smaller cutter that would allow me to climb mill the sides individually, but that may be hard to find.

As mentioned, chip evacuation is critical to prevent rubbing and work hardening of the stainless. Carbide teeth are nice if you have a rigid machine, otherwise cobalt HSS to retain edge hardness during the long tooth engagement path would help.

Listen to the cut, if you get squealing remove the cutter and resharpen or replace. If using a CNC mill be sure not to pull the cutter up through the work if you interrupt the program mid-cut!

The first slot(Primary slot)should go as deep as the drg will allow.Normally it will be slightly deeper(about .25m/m deeper) than the cross slot.This is to stop bottom of "T"cutter rubbing and assist the cuttings to escape.As in cutting dovetails build up of cuttings is your enemy-Preferably a stagger tooth cutter/cheap cutters are a false economy-http://www.keocutters.com/product/70120/

Thanks for the replies guys, I wasn't sure about the cutter going from conventional to climb milling with the slot going all the way to the bottom of the T. I'll be using a Dormer high speed cutter on a Bridgeport type mill so I guess I'll have buckets everywhere to catch the coolant. Any suggestions on speeds & feeds would be appreciated.
Cheers Pete

Its one of those jobs that is easier if you "Know" your machines little quirks.Thats speeds/feed wise.I would start off at 140rpm/20m/m ipm-See if machine is cutting well then you could gradually bump both F/Speed up to 190/40.Thats what I mean about knowing your machine next time you will say "T"slots in stainless went well/terrible last time and you know what feed to start at,depending on your past efforts.Its a job that cant be rushed other wise you will end up with a pile of broken cutters

Spacely Sprocket said:

Thanks for the replies guys, I wasn't sure about the cutter going from conventional to climb milling with the slot going all the way to the bottom of the T. I'll be using a Dormer high speed cutter on a Bridgeport type mill so I guess I'll have buckets everywhere to catch the coolant. Any suggestions on speeds & feeds would be appreciated.
Cheers Pete

Click to expand...

The 'climb' versus 'conventional' aspect self balances because opposing teeth on the cutter are equal but opposite in aspect.

Do not run it fast, and feed it like a baby. Run it slow and feed it firmly and aggressively. SS is easy to take heavy chips out of, but it bites when you baby it. If you pause in mid cut, immediately back the table up so the tool is not rubbing (while you clean chips, etc).

Tooling it makes a difference you could pick a cheap one or go for a stagger tooth solid carbide-expensive yes but you get what you pay for-The stagger tooth one will clear the cuttings better and last longer with slightly higher feed but whatever ever you choose its a slow job try and rush it and you will end up taking twice as long to do the job-But its a "T"slot so shouldnt pose too much of a problem.Pencil clear the cuttings occasional blast of air-Pair of steel capped wellington boots and swim suit