life of Hss mill bits

[Deny1950]

Hi this is a bit of a stupid question but how long do you guys get out of a mill ,on average. I know it all depends on the feed, rpm, material, and cut depth. Assuming things are done right would they ware out in one day. Do you all resharpen them or through them in the garbage bin? Would 500 rpm on mild steel with a 1/2 mill tacking 50 thou. be to much? I know the chips are not disscoulerd and are not very hot, any help would be great Thanks Denis

 

[DMS]

Most of mine break before they get dull, so I never have to worry about it

The numbers you give below are really conservative, but it's going to depend on your machine. If your using a minimill, that's probably good (though I would kick up the spindle speed a bit). On a full size machine, Gwizard doesn't complain until I try to slot at 0.6". Even then it's suggesting about 900rpm. With a more conservative DOC of 0.25". it's suggesting 920RPM (with a stickout of 1 inch).

There are basically 3 ways cutters wear out, they break, they dull, or they burn up. Breakage happens because of too much feed or from chip packing. Dulling comes in due time, or from not enough feed (rubbing). Burning up comes from too much spindle speed. If your chips are still silver, you can run the spindle higher. If the machine isn't complaining, you can go deeper/faster too. Listen to the cut, it will tell you a lot.

 

[Alphawolf45]

Dont throw out dull or broken endmills.. Real often = today for instance- I hunt through my old endmills drawer till I find the right one to grind down to smaller diameter to use as a reamer or counterbore or whatever is required..Today I ground an old 1/2 inch HSS endmill down to .420 dia. to cut the cartridge clearance into an extractor for a rifle ..And then would have ground down another endmill but I found a 3/4 inch endmill I had already ground down to .515 which I then used to cut the rim clearance into the same extractor..Dunno what projects you get into..Fooling with gunsmithing as I do I am constantly needing to make special tools..and I think most everybody else does the same thing in their own projects....?

I use carbide endmills mostly..And will resharpen them on the end by hand on a diamond wheel which does well enough for a lot of work and then pull out the new endmills only when the work justifies their use.

 

[Deny1950]

Thanks for the info, I was also wondering if any one of you guys have a sharpening machine, am thinking that would be a good project to take on but might be a bit to advanced for me.

 

[jedel]

Thanks ,and the sound answers for the question i will put the advice to work

 

[DMS]

There are plans for a modified Brooks grinder in the current issue of Home Shop Machinist. I started on one a while back (before the magazine issued it's updated design), but got sidetracked on other projects after finishing the spindle. I think the Brooks grinder is an easier build than the Quorn or Blondelle.

I also decided it wasn't worth while to sharpen end-mills given my usage pattern, though I still want a T+C grinder for making custom cutters.