[yoshi900]

It's has always puzzled me how tool manufacturers make the thru holes in endmill and carbide drills. Anyone know?

Yes, I've tried google it and didn't find any info on it.

[sordon23]

Hi,
When the drill is pressed into the form they put a wire into the form. After pressing, the drill is baked in a sintering process and the wire melts away.

[scurr]

Not quite sure what you mean. I have seen it EDM before but am curious about the process you mentioned.

Cheers

[109jb]

Used to work at Guhring. For larger drills they would EDM holes diwn the drill blank. Then the blank got heated and twisted so that the holes would follow the helix of the flutes. From there the drill flutes and other finish operations were ground.

[Geof]

Not quite sure what you mean. I have seen it EDM before but am curious about the process you mentioned. Cheers

Carbide tools are made by sintering. The carbide is in the form of very tiny particles coated with cobalt. These are put in a mold and subjected to very high pressure and heat so the cobalt coating fuses cementing the carbide particles together. Cobalt has a high melting point so it does not actually melt during the sintering process but the temperature is high enough to melt other metals.

[Zirok]

As you mentioned that the wire melts (when baked). But the big question is that how does the wire exactly follow the path of the flute ?

There has to be some technology which ensure that the wire doesnt melts outside the area of flute.

A

[109jb]

With the drills, the twist per length is known an the heated blank twisted that amount. The blank was indexed to grind the flute in thevright spot. even so, the grinding sometimes still exposed the coolant hole. If it did, that one was scrap.

[scurr]

Is there any video footage of the process on the net??

[bebob1]

I think its possible they make it by extrusion press of the green compound through a die with the hollow channels, then they twist the still green part to the correct helix. Then it is sintered, and then the flutes ground.

I think there are many other possible ways of fabricating it. Such as layer by layer sterolithography like selective laser sintering might work, followed by grinding. Or EDM etc. If it was more flowable or wasnt a ceramic material, they probably have more options too. E.g. they commonly make internal cooling channels of titanium turbine blades by investment casting. Similarly they use investment casting for aluminum engine blocks.