drilling/ milling stainless 304

[warfreak]

can any 1 give me some feedback on this.

im trying to drill four .75 side holes on a 3' diameter(od) .

material is ss304.

i have it setup to first drill a pilot hole (.360) F 1.5 rpm 475 <cobalt>

then a .690 drill (g83 @.125/peck) f1.0 rpm 268 <hss>

finally i use a .75 endmill F1.2 rpm 240 <hss>

hole location and perpendicularity is important because a mating pin is inserted.

im also using an automatic index table .

any input would be much appreciated

[Geof]

You do not say how deep.

304 work hardens and if possible you should avoid pecking.

Also your feed is a bit low, my calculation gives around 0.0016" per tooth which is maybe not enough to get under the work hardening. I think you should be able to take this up to 0.005" maybe even more.

And I wonder about piloting at 0.36" then drilling at 0.69", you might find the larger drill chatters badly and the edges chip. I would be tempted to go straight in with a split point drill possibly running slower than your speed but with a good feed and lots of coolant. The risky parts comes when it breaks through, you really need to get plenty of coolant there and directed to the back side of the hole if possible as things can get very hot at this stage.

It seems you are using the 3/4" mill somewhat as a reamer; this is okay and will certainly give you a better hole than a drill can produce. Here I would consider using a corner radius endmill, the sharp corners on a regular mill get much hotter and can be prone to chipping.

[warfreak]

im drilling through the id (2.0 diameter)
also im a bit limited in the drill dept


thank you for this feed back geof its very much appreciated

[Jitendra Tomar]

Yes SS 304 is wokhardening and long chiping material. Use Through Coolant crabide drill with sharper gemetry as the surface is radial please first make a flat on dia rather then using pilot drill. Certainly packing would help you in chips ejecuation.Do not hesitate to increase Cutting Speed as the matrial is some what sticky also.