sharpening end mills?

I think most will agree that it is impossible to adequatly sharpen the side cutting edges of an end mill but touching up the end cutting edges manually may be possible for some. However, it would be probable that the four edges would be at slightly different levels and would surface the workpiece using just the lowest one. OK, it may give an improved finish even though the feed rate at the surface will be four times greater.

For a simple jig to do the task accurately look on my website here http://www.homews.co.uk/page121.html

I would suggest that the woodern mount on the last page of the item will work just as well as the method in the design and reduces the work involved in making it appreciably.

I would add that sharpening just the end edges can improve the results achieved by quit a bit and is definitely worth doing.

For those who do not know my site the index for the metalworking pages (around 500) is here http://www.homews.co.uk/page463.html

Harold Hall
 
Two flute end mills ar fairly easy to grind on the ends, four flute more difficult to avoid damaging the (other) two cutting edges. I commonly regrind mills as small as 1/4", and sometimes 3/16", but 3/8 may be a more practical limit for some. I do have a #2 Norton tool & cutter grinder and a Harig air bearing attachment, which I vastly prefer to the (possibly) more well known Weldon attachment, as it does not require the tilting base that Weldon uses, but has a angularly adjustable tooth rest to set clearence on the flutes; for end clearence, the spindle tilts. I do the end gashing and secondary6 end clearence offhand.
 
sO digesting all this info for a beginner, I'm thinking if a 2 flutter needs sharpening, and you never done it, probably best not to grind, but maybe grab a honing stone and if it's not too worn, just dress it up a bit

i noticed once you get something on a bench grinder, you gotta know what you're doin b/c things happen fast
 
benmychree said:
I commonly regrind mills as small as 1/4", and sometimes 3/16",
Click to expand...

benmychree and 4GSR. I've had no problem grinding 1/2" end mills with a cup wheel and my Weldon fixture on a KO Lee T&C grinder. I haven't tried anything smaller yet. When you grind small end mills of 1/4" or smaller, do you still use a flaring cup wheel, or do you use a small diameter regular wheel? I'm asking because I wondered how grinders prevented accidentally grinding the flute above the one that was being intentionally ground on a small diameter end mill.

How much do you grind off the end when you're just sharpening the end?

How do you tell if the flutes need to be sharpened?

In my limited experience, it seems easier and faster to grind the ends in one of the cheapo end grinding fixtures on my surface grinder than to set up the Weldon fixture to end grind on my tool & cutter grinder. Is your experience similar?
 
RWL said:
benmychree and 4GSR. I've had no problem grinding 1/2" end mills with a cup wheel and my Weldon fixture on a KO Lee T&C grinder. I haven't tried anything smaller yet. When you grind small end mills of 1/4" or smaller, do you still use a flaring cup wheel, or do you use a small diameter regular wheel? I'm asking because I wondered how grinders prevented accidentally grinding the flute above the one that was being intentionally ground on a small diameter end mill.

How much do you grind off the end when you're just sharpening the end?

How do you tell if the flutes need to be sharpened?

In my limited experience, it seems easier and faster to grind the ends in one of the cheapo end grinding fixtures on my surface grinder than to set up the Weldon fixture to end grind on my tool & cutter grinder. Is your experience similar?
Click to expand...
I always use a flaring cup wheel, nearly always a CBN, which has practically no wear in use. One needs to grind only as much off as to remove the visable bright spot on the cutting edge that is an indicator of wear; if this bright spot is seen on the flutes, then it too should be sharpened if it extends very far up the flute; if the corner is knocked off, just grind the end back far enough to eliminate it. It may come down to the proposition that "what do I need, full diameter, or (nearly) full length"? I grind the ends on the fixture for the primary clearence, then generally do the secondary clearence and gash the center by hand; I do this at the bench grinder with a hard fine wheel that will hold a good sharp corner. Large size end mills I would likely do this in the fixture.
 
benmychree, thanks. Those few sentences were very helpful. I'm not sure if I can recognize the bright line you're speaking of on the cutting edges, but I'll look for it. Very helpful to know that you're using a hard wheel to do the gashing. I knew those K hardness wheels would come in handy for something some day. Always interested in any more tidbits about sharpening you can think of. Thanks again.
 
Quote:

"I've had no problem grinding 1/2" end mills with a cup wheel and my Weldon fixture on a KO Lee T&C grinder. "

and

"I always use a flaring cup wheel, nearly always a CBN"

This is way above my head; I'm presuming these are some pretty expensive setups
 
SE18 said:
Quote:

"I've had no problem grinding 1/2" end mills with a cup wheel and my Weldon fixture on a KO Lee T&C grinder. "

and

"I always use a flaring cup wheel, nearly always a CBN"

This is way above my head; I'm presuming these are some pretty expensive setups
Click to expand...

They are pricey, but they were a lot less expensive when the economy turned south in 2008-2012. A naked tool and cutter grinder isn't worth much since you need tooling to make it do anything useful, and a lot of what you need isn't easy to make. The tooling took a major leap in price on ebay in the last year. You can grind the ends of end mills relatively inexpensively with one of the generic fixtures that holds end mills in 5C collets, and using either a surface grinder or a tool and cutter grinder. The ability to sharpen the flutes requires a separate fixture. I think the most common were made by Weldon, but KO Lee and Cincinnati also made flute grinding fixtures. I bought my KO Lee T&C grinder with a generaous amount of tooling, among which was a non-air bearing Weldon fixture. The dealer who sold me the outfit thought he could get around $200 for the Weldon fixture at that time circa spring 2007. I just looked on ebay and the selling price looks to be $600 now, with one lucky buyer getting one for $300. Flaring cup wheels are basic grinding wheels and not expensive comparatively. The CBN (cubic boron nitride) wheel is expensive. IIRC they run $300 new from Norton, but wear like iron. I suspect that most home shop owners got the CBN wheel with the grinder.
 
i used to resharpen end mills freehand many years ago. But,it is not ideal,as Tony mentioned. I have an old Weldon NON air spindle on my K.O. Lee "Knockout"(a small t&c grinder. It works fine,but is not as slippery smooth as an air spindle.
 
Those CBN/ Borazon wheels are nice. I use one daily at work, holds up well and lasts a long time for sure. Make sure that the aluminum isn't dragging behind the cutting edge though. When it gets to that point I'll take a used grooving insert and skim the alum back from the abrasive by 1/32 or so. Makes for a free cutting wheel that will stay cool.
 
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