Check with
@Wilhelm as he has some of the best drill bits for drilling bars.
Very kind of You, thank You.
My manner is to use dremel with diamond bits from Amazon. Modding oil hole to allow higher flo onto dl's, making 1/4" hole in center of sprocket for Alaskan post. From Amazon I keep looking for the least expensive and grab several for free shipping.
Carbide is painfully slow even if they are sharpened as much as can be. But none of them are speedy
I agree, diamond laced burrs are universal and work on any material.
In regards of Solid-Carbide (aka. Widia, Tungsten-Carbide, Wolfram-Carbide) being slow - yes a masonry Carbide tipped bit is slower than a snail.
But try some Solid-Carbide bits specifically made and sharpened for processing metal.
The supported speeds (rpm), feeds and materials that can be processed are extreme.
There is nothing slow about a Solid-Carbide drill intended for processing metal.
I've never drilled a guide bar, but have you tried cobalt bits? I use them on anything hard and never have much of an issue. Then again, I have no idea how hard guide bars are. I wonder what Rockwell they would be. (quoted wrong post earlier, hence the reason I deleted it)
If You are referring to HSS-Co (High Speed Steel Cobalt aloyed) drill bits, they may be able to go through a soft AM bar but not quality OEM and brand bars.
In the end they are still merely a steel based alloy.
True, the added Cobalt makes them harder, but they are nowhere close to Solid-Carbide.