roughing down carbide endmill for special, any tips
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  1. #1
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    Default roughing down carbide endmill for special, any tips

    I need to make an 82 degree included tapered end mill from carbide. The cutting face needs to be over 3/8 long. I have made many similar cutters, starting with a used carbide end mill. I use a surface grinder and spin them in a whirley gig to circle grind, then grind a primary relief. I will add a secondary relief or hand clearance as necessary.

    I wondering if there is a better method to rough the tapered shape. On HSS cutters I rough them out with a 36 grit on a belt grinder, that saves a lot of time on the surface grinder.

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    Wet or dry grind?
    Spray bottle at least?
    Face wheel grind probably the fastest.
    Cold grind machine or those used for sharpening scrapers?
    Send it to me? I'll rough and circle grind it for free if it will fit in 5C spin fixture. (Your friends and family discount is honored here)
    A cheap ebay 100-150 grit face wheel with some water and stick and just go at it by hand?

    Weird but I'd much rather do this in carbide than HSS. One is faster in my shop.
    Putting the wheel on the machine and putting the indexer to the right angle is the slow part of the process.

    Some will say green wheels on a bench grinder. Works I guess but the thought makes me cringe.
    Bob
    Last edited by CarbideBob; 08-17-2021 at 09:20 PM.

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    CarbideBob, thats a mighty generous offer. I thank you greatly. But that leaves me back at the same situation I am in now, looking for more knowledge about grinding carbide. I have a pretty good background on small surface grinders on steel thanks to a couple of very knowledgeable cohorts long ago.

    When it came to grinding or sharpening carbide they had little experience either, we just went at it hammer and tongs. Usually with a surface grinder, whirly gig if required, and a cup wheel. Not much knowledge base to draw from other than the experience we had. But we made a lot of tools that made good parts.

    Now I no longer have the need, but have the desire to know at least a little about how to approach the problem.

    What would you suggest for a face wheel? Will the concentration or grit numbers off a ebay wheel even have meaning?

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    Grit numbers and concentrations are the same as long established.
    What is not is filler, bond type, and hardness letter.
    Roughing 120 grit, semi or dual rough and finish 220-320, finish 400, super finish 800.
    Fillers two basic classes green and brown. Silicon carbide and copper.
    Super wet likes the green as it cuts cleaner, dry likes the copper as it sucks out the heat in normal resin wheels.
    Then vit bonds and porosity bonds and letters of my. How long in the press, how much pressure, heat cycles????

    A good wheel stick and it's usage means a lot. If it seems not to be cutting so great stick it. Do not be afraid to do this often.
    On a matched wheel and stick one takes 1/8 to 1/4 inch off the sticks end each time on a 6 inch wheel.
    Problem with sticking is that you break down the corner of the wheel so if you need to hold a .006 corner rad with a 400 it becomes a bit of an art as to how the stick applied.

    Not to worry. After 20 years or so it will be so easy. After only 40 years you will be able to make just about any diamond wheel work.
    For better challenge try CBN and PCD.

    In the world of what you are doing I think our member Michiganbuck perhaps a better source of information than me.
    Bob

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    A bargain brand spin index can become a hack work head and with drilling a hole in the base one can mount it to an angle plate. Surface grinders can grind almost anything but failure to easily see the cutting edge makes cutting tool grinding more difficult. Very often one has to bump an angle to make a straight land to sharp and this is another dill point with cutting tool grinding with a surface grinder.
    A simple TC grinder like a Ko lee can make an easy and full task of tool grinding.
    Diamond wheels love coolant, dry grinding is slow and hard on the wheel, and also produces a poorer surface finish. Wheels finer than 350Gt run dry can cause heat fractures in the cutting edge.

    Sometimes one might put a lathe dog on an end mill shank with it held in a work head(or the like) and using the dog for a handle incrementally/bring the cutter up into the wheel so to grind. The Dog becomes a good handle and coming up, so not climb grinding make little chance of a catch and try to flip the part.

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    Get an M A Ford 82* multi flute carbide countersink. I works quite well for milling.

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