End Mill Sharpening Attempt

Hi. Thanks for the offer and information. These are community consumables, and have to be left in the shop. When I need to get something done, I have my own end mills that I got at a garage sale. They are name brands, in excellent condition, and seem to perform well. Most of the other people using the mills bring their own bits, and have favorites. Most of them use generic carbide end mills that they get online, such as at Enco, since these seem to provide the most bang for the buck. I am afraid that I am still too much in the beginner stage for that right now.

The past weekend, I looked at the milling machine community box and noticed that someone had gashed the end mills that I attempted to sharpen. I think that I have the geometry down now, and further experimentation might prove fruitful. From what I saw, gashing is pretty straightforward if the end mill can afford to lose any center cutting ability. Just make an x in the end with the corner of the wheel. The wheel must be dressed sharp. As mentioned above, it is challenging for carbide, since the green wheel at TechShop is never dressed sharp.

I just got my cutter grinder up and running recently and have sharpened mostly carbide end mills. I have the primary and secondary angles figured out, but when it comes to gashing them, it looks like I need a thin wheel. Looking at new endmills, it appears that the gashing was done with a wheel no more than about .090" thick, and it has a slight bevel on both edges. Does someone make a wheel just for doing this?

I wondered about that myself. Every time I try to sharpen an endmill, I never seem to be able to get that cross cut that I think you are calling a "gash". It seems to make the endmill look nice but is it "important"? My Darex-E90 doesn't mention anything about that in the instructions or in the videos...
Any one know if it is important or not? If it is, what is the reason?
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Bill C. said:

Nice looking grinder, http://www.darex.com/drill-sharpeners-and-grinder/e90-17/e90-end-mill-grinder-and-sharpener.html.

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That is the one I have. Works pretty well. You have to have compressed air to make it work though. The rod that holds the collet is "air lubricated" and glides real nice with that compressed air moving through it. Works well for the plasma cutter, too!

tpic402 said:

One match fire, I also have a Darex e-90, got it for a little trade it is brand new it does take a little getting used to, I have the opportunity to buy a e-90 along with a darex drill bit sharpener(the kind that looks like a bench grinder) 2 Foley saw sharpener one for hand saws and one for circular. The gentleman told me I could have them for $500. What do you think.

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If all of them are in really good condition, I'd think $500 is pretty good. But I am NOT an expert on anything. I'm still trying to learn how to "silver solder" a carbide tip to a steel blade without melting the blade... I am a slow learner...
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derf said:

I just got my cutter grinder up and running recently and have sharpened mostly carbide end mills. I have the primary and secondary angles figured out, but when it comes to gashing them, it looks like I need a thin wheel. Looking at new endmills, it appears that the gashing was done with a wheel no more than about .090" thick, and it has a slight bevel on both edges. Does someone make a wheel just for doing this?

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They do make and sell "thin" diamond wheels for gashing the ends on end mills. I bought one of the Chinese import ones off of Ebay. The only problem is, you may have to make a arbor or bushing, or bore it out to hold it in your cutter grinder. I haven't had a chance to set up and try the one I bought. Also have a couple of diamond cutoff blades that should work on much smaller ones like 1/2" and smaller.

Will one of you please explain "gash" (one photo will probably do it all,)
Is a "gash" actually necessary and if so, why?
Can the end mill perform without a "gash?"
I'm so new I just don't know.
Thanks

The picture is not the best, but you'll get the idea. The gash puts more relief in the 2 opposing flutes for center cutting ability. Without the gash, the mill won't plunge very well.

OK, Now I get that. I have been sharpening the endmills without the gash and they just never looked "right" because I wasn't adding the gash. Now, the question becomes how is that gash made once you have sharpened the endmill to the primary and secondary relief? Is it cut first or after the primary and secondary relief is ground?

Is PLUNGE a critical and ALWAYS required feature? Will the endmill cut surfaces without having to PLUNGE or is that the entire purpose of doing the surface?
Someone mentioned a thin diamond wheel to do it. Is there any other technique to do it? If so what and how should it be performed?

As you can see, I am a rank amateur but can learn. I would like to be able to help the machinists in my area as well as do my own work. This learning is helpful for those activities.
Thanks
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The ability to plunge is critical if you are milling pockets. If you are starting on an outside edge it makes no difference if you only step over 1/2 the dia. of the cutter. I'm guessing the gash is done after the 1st and 2nd relief, just for the fact that now you know how deep to go. A HSS endmill could be done with a cut off wheel, even freehand if you were steady, but carbide will require a diamond wheel, I just haven't found one yet.