I bought a carbide burr off Mcmaster-Carr and it cut for a while, but seemed to have burned up and dulled far sooner than I expected. Any tips on grinding on stainless (304) with a die grinder? Should I have been goer slower?

Thanks,

Eric

trick to stainless is go slow, lots of lube/coolant and be prepared to replace tooling often

While i do not use many burs, i do cut stainless. A die grinder will spin at 25,000+ RPMs. When i am setting up a stainless job at work i spin it at about 2,000 RPMs. Steve is spot on, slow it down and expect to wear out the tooling. We change tools at about 1/2 the life if i were cutting a 1035 or 1018 steel. You can also tell the difference in stainless to other steel by the chip it makes. Stainless will pull a spiral when drilled while regular steel makes small chips for instance. 

You can download some of the older Machinery Handbook, a new one will cost somewhere around $200. However even the older ones the info is still usefull today. 304 stainless cuts the same today as it did 20 years ago. The only reason to get a new one is for the newer materials and tooling. This book will tell you how fast you can cut different materials along with a whole bunch of other stuff most people look at like they are reading Greek. Anyway it is one i highly recommend for any one who wants to work metals. Not only does it have speeds and feeds, but drill and tap tables, conversion tables, etc. Loads and loads of info, hence the price of a new one. Well worth the investment in my opinion. 

Another thing the older Machinery Handbooks have, is sections on Blacksmithing that the new versions have eliminated.

You can get a replica 1914 (?) original edition from that place named after the forest in S. America for about $45. 

Machinery handbook is a handy thing to have for sure.

Carbide is very brittle, so you need to stop any chattering as it just breaks the cutting edge off of the teeth. My Dad taught nuclear pipe prepping, and they wound the carbide burrs up as fast as they would go. His die grinder did 50 or 60,000 rpm. Firm steady cuts so you don't chatter. It takes some practice, and a real steady hand. You may try two handing the die grinder for more control. You need enough pressure to pull a chip, and not just rub the surface. With carbide you want the chips coming off blue. With a HSS burr that would be too fast and hot. HSS chips should be silver to a very light straw color.

 

What kind of items, and shaping are you doing?

Forgot about this topic.

I need to correct myself to start with. A bur to me is something all together different than what we are discussing. Hence the reference as to how chips look when drilling. 

So anyway, yes you can run it faster than i stated. However your speed is dependent on a couple issues 1) diameter of the bur, the bigger the bur the slower you go, 2) how much shank is exposed, more shank go slower. Ideally you want a feed rate somewhere between 1,500 and 3,000 FPM ( (RPM) x PI x (diameter) /12 to get feed rate) Using a 1/2" bur at 15,000 rpms. 15,000 x 3.14 x .5 / 12 = 1,962.5 FPM. 

So FPM = RPM x 3.14 x Y / 12. (Y being the diameter of the tool.)

RPM = FPM x 12 / 3.14 x Y   (Y being the diameter of the tool.)

These are the basic formulas for figuring out speed and feed rates. What you have to figure out is what is the ideal feed rate of the tool you are using. You can get that info from a machinest reference book, the tool maker, and even the supplier of the material. 

 

 

 

one more thing is the coarseness of the teeth on the burr.  Too coarse will chatter when turned too slowly. Too fine will go away quickly when turned too fast.

I have some very coarse HSS burrs, for removing lots of material quickly when cutting aluminum, and mild steel. They like to be turned very fast, and fed slowly.

The finer carbide burrs seem to like a slower speed than the coarse ones, and can be fed a bit quicker.  But with coolant, you can spin them at a pretty good clip, really cut some metal.