Economics of end mill sharpening

For the hobbyist they may have a value but a commercial shop would probably have no use for them because of them being undersized from the sharpening. Unless you can hold the size to within a tenth or two you must reprogram the cutter comp for each end mill as compared to using new end mills that are right on size.

The small 1/4 in end mills are not worth that much. Larger ones over

3/4 inch start to become economical to sharpen because of the higher replacement cost.

John

Maybe that's why they are dumping 400 lbs of end mills.

i

However, endmill diameter is not so important when used on manual milling machines. More important to users like myself is the material they are made of. I will resharpen cobalt hss alloy (M35/M42) and throw the rest away, including carbide. Steve

We figure the cost of tooling into every job and the saving usually aren't worth the chance of ruining or reworking a part. I can't remember using an end mill larger than 1/2", anything larger is indexable. They used to be expensive and resharpening them was common. No more! But, if I "fell" into a good sharpener, I'd do them for in-house use. I'd say used, sharpened end mills @1/4" are worth maybe $10/dz.

Thanks, nice and solid number, something to work with. I would be unlikely to do anything re: those used endmills. Sweeping floors at Burger King would probably be more profitable. I could buy and scrap them for a quick buck though.

i

If you can't make more money metalworking, versus sharpening metalworking tools, then you're in the wrong line of work altogether. I don't mean grinding a custom tool for a certain job, but doing it in bulk like you contemplate.

The other thing to consider is that an endmill that seems dull to a professional might be serviceable for a hobbyist. You could sort out the really bad ones and sell the remainder on ebay.

Ignoramus6607 fired this volley in news:Y-adnSyrlJ_gcTrRnZ2dnUVZ snipped-for-privacy@giganews.com:

First off, Ig, the 1/4" mills won't be 1/4" once sharpened, unless you're only touching up the ends.

My guess is that used endmills _from_someone_else_, regardless of condition, are almost worthless commercially, but might have some decent value (say 40% of new) to hobbyists. Most shops willing to use re- sharpened mills are having their own done. About the only way to tell if a mill has been properly re-ground is to cut with it, unless you have the optical stuff and the knowlege to inspect them.

LLoyd

While your question is more one of how can you make a buck off 300 lbs. of dull end mills, I for one will choose a reground end mill most of the time. I have several reasons for this.

If I am milling on the edge of a piece of material it makes no difference to me if the end mill is .005 undersize.

If I am milling a pocket or milling a surface being a little smaller makes no difference either.

If I am milling a slot, an end mill tends to walk a bit so the slot becomes a little bit wider, an undersize end mill will often allow me to take a larger cut and keep the slot from widening too much. Also, when I finish the slot to size, I only have one side rubbing, so it is easier to get a better finish and predict the behavior of the cutter.

So unless the price of a new one is more than sharpening go for the regrind. Usually however the tool grinding shop will beat replacement every time.

Iggy, you might find a sharpener in your area that will either take the dull ones off your hands with no effort or give you a deal on bulk sharpening. I worked for a tool and die maker that had a fixture to dress the end but usually he would just collect a dozen before he would drop them off at the sharpener. Of course the economics may have changed since then, but I suspect that a good quality end mill is most always worth sharpening.

Roger Shoaf

Ignoramus6607 wrote:

If you are running a long job and using an M42 or carbide endmill and have a company that resharpens on a cnc grinder and will recoat the tin on them you can save half the cost of new ones but they all have to be the exact same diameter and length when ground or you have made yourself a headache.

John

Hey Iggy,

You've had quite a few good pro and con replies so far, mostly "con". I don't do any end-mill sharpening for myself (not qualified!!). On the other hand, 75 bucks for 400 pounds sounds tempting, even if you only sorted out 100 good ones. And if there is any of it in the batch, carbide scrap is going for about $6.50 per pound ...

One question I would be asking before you consider anything else, is what quantity of the end mills are "plain", versus those with corner radius or ball-noses and other special shapes or those that may be broken, any of which may not be "doable" to sharpen on the Darex.

A friend of mine in tool & die the has a nice Cincinnati Universal T&C grinder with an air-bearing end-mill holder. He will sharpen larger ones for his shop, say over 3/4", or down to 1/2" if they are special like really long... (read expensive)... and then just changes the tool size description in the tool CNC library/changer, and that way it doesn't change "offsets" (which have a slightly different CNC programming purpose). They don't diddle with sharpening standard smaller stuff, and make the special small stuff with a Deckel SO to suit the job, mostly for draft on carbon for EDM.

Take care.

Brian Lawson, Bothwell, Ontario.

$75 is cheap for Christmas presents for all your helpful friends here on R.C.M.

jsw

The issue I see is that if you use an edge finder or a dro, you've got more math to do. It's too easy to screw it up. But, resharpened mill certainly have their place and value, just not so much in a production or precision situation. What's the cost of a part that needs to be fixed or pitched?

Maybe I'm just a little bit weird, but I actually LIKE when an endmill is just a little undersize....

....as an example, if I am using a 3/8" endmill and the print is actually calling for a 3/16" corner radius, if I just use the 3/8", I may end up with chatter in the corner....

...but if I use a resharpened 3/8....it'll likely be around .360" and all I need to do is change the tool diameter in the tool setup and I'm done.

That gives me the strength and chip load of a 3/8 while being undersize just enough to generate the radius rather than forming it.

And yes, I'm talking about in a commercial setting.

The only real drawback to it is that if there was any coating...TiN, TiAlN, whathaveyou...it's largely ineffective.

Luck

Mike

[ ... ]

And -- if it is a three-flute or a five-flute end mill -- how do you measure the diameter?

Yes -- there are special V-anvil micrometers for such measurements, one for the three-flute and one for the five-flute. Do

*you* have them? (I do -- but I collect tools, so I perhaps don't count. :-)

But these special micrometers are expensive too -- especially if you need to purchase them new. :-) (Unless you need the three-flute and the five-flute versions to measure ground cylindrical surfaces for lobes taking them off truly cylindrical. A standard micrometer won't see these particular errors.

Of course --you could skip the edge finder and find your zero with the old cigarette wrapping paper trick instead, which would include the change in diameter in the setting -- for that *one* edge. :-)

Enjoy, DoN.

I cut a lot of keyways and do them in on pass. A resharpened end mill makes a project out of it. If you know how much was taken off the endmill when it was reground you can easily program for the smaller diameter but then if you happen to have a new endmill in the holder... whoops. By the way you can get regrounds recoated from some of the larger resharpen places.

John

When I used to have to use regrinds with odd numbered flutes, I'd clamp the shank in a V-block on the granite table, put an indicator on the OD of the shank, then pick up the reground edge with the indicator which would give me the difference in the radius. Not a problem if you didn't need .001" accuracy. If you did, use a new end mill.

David

Small printed circuit drills and mills...spots and such - are often sharpened and left to be sold for nothing. New is fast and cheap (more or less).

Often only a tip is broken - so the sides are not ground. Just regrind the end of the endmill.

Mart> >>> Someone is offering me a lot of appx. 300 lbs of used HSS endmills,

All of that may be fine...to a point...

....if it's being done on a manual machine, I"ll give you the new mill/cut to size...

...you said that in a commercial setting, that it won't work to use resharps...or words to that effect...

...and I will still say that ALL it takes in a commercial setting is to measure the end mill and put that size in your tool set up and you're done...I do it every day, all day long.

I would NEVER dream of pulling up an old program and putting in tools that I haven't measured and calibrated...anyone that does is not only asking for scrap, but begging for it.

I'll continue to use resharps for where they make sense....and new for where resharps aren't gonna work.

there is a time and a place for both....the key is to know which is which.

Mike