Proper grit for sharpening drill bits?

100 grit is too fine for repointing, but is OK for sharpening as long as you don't have a lot of metal to remove.

Randy

According to R. O'Brian :

However, most stones don't work well on carbide, whatever the grit. The green stones *sort* of work but diamond is better for solid carbide -- and *worse* for HSS or any other ferrous metal.

Also -- you want a dust mask when sharpening carbide.

Enjoy, DoN.

According to :

I've got one of those -- and while it will split the points on larger drills, try a #30 or something similar, and it never seems to work for me.

BTW Are they now offering more than one grit of diamond wheel for those?

Ideally -- they should have two wheel choices (exclusive of grit) -- diamond, for carbide bits, and Cubic Boron Nitride for HSS bits, as diamond gets fairly rapidly eroded by the hunger for carbon of hot ferrous alloys.

Enjoy, DoN.

Yeah, they offer 100 grit and 180 grit wheels for both the old and new models. They only offer diamond wheels. I haven't had a problem splitting bits on the 750...can't remember if I've tried to split an 1/8" bit though, although I'd expect no problems using the 750 versus the 750X because the point splitting is manual on the 750 for better or for worse. I'll have to try and split a 3/32" bit (the smallest spec'd bit) on both the 750 and the 750X. I'm a bit skeptical of the 750X though since it has a splitting stop and it is non-adjustable.

Don,

Do you find that it's worthwhile splitting the points of such small bits?

Because of the work I do, I find it benificial only to split points above roughly 10mm dia. as I will be using a powerfeed and no pilot. The split point typically increases cutting edge life. However, the vast majority of holes I'm doing do not have tight tolerances as they are only for threaded holes on over-designed stamping dies.

I split the points using a standard pedistal grinder so I can't imagine trying it on anything less than about 4mm or so (and even then...) Do you find there's a significant difference in the drilling process or resulting hole when using small bits (perhaps under 3mm) which have split points?

Indeed, even when using an electric or pneumatic hand drill on materials ranging from soft cast iron to cast D2 tool steel, I find there is no need to split the point (typical starting pilot is 4.2mm dia).

Regards,

Robin

I honestly don't know. I'm a newbie here. I'm making my purchases based on theory rather than experience. I ASSUME that its necessary to split little bits, but I might be wrong. As I'm beginning to learn, the older you are, the more experience you have, the less you spend.

According to Robin S. :

Well ... not always, but I like to have a full set of split point drill bits, simply because it makes certain things easier.

In particular, I think back to when I had to drill 1/16" holes through the far end of guide pulley shafts for the garage door tracks. They kept working their way out of the brackets and wedging, making it difficult to get the door up or down without getting inside to work on it.

Anyway, I decided to drill a hole through the end of each and insert a cotter key in each to keep this from happening again. But -- pulling the thing out entirely to work upon in the drill press was not in the cards without assistance, so I chucked up a 1/16" split point drill bit and drilled each using a hand-held electric drill motor. Unlike with standard chisel point drills, which would require a good center punch mark to hold the point from walking, I found that the split point was easy to start without a center punch mark and to do the whole thing by hand.

The shafts which I was drilling were about 3/8" diameter, IIRC, or perhaps 5/16" (which is close enough to 8mm to get it back into the units which you use most often.

And in general, I find the split points to be a lot easier to start in places where a spotting drill either can't be used, or simply requires too many tool changes.

So -- I find it worthwhile to *have* small split-point drill bits in all sizes, and without the ability to split points, if one gets dull, I have to buy more bits sooner. (I have a nice drill grinder once made by Dumore (and now obsolete), which will nicely sharpen drills from

1/4" down to #70 in size, but it *won't* do split points.

It also significantly reduces the effort cranking the tailstock feed wheel when lathe drilling the end of a workpiece to 1/2" prior to using the boring bar. But for 1/2", I should be able to manage the split point feature of the DD.

O.K.

Ease of starting on a curved surface without a center punch mark or a spotting drill.

I have done little drilling with an air hand drill, though I now have one, and need to try it from time to time. But again -- if I am in a position where I need to start holes on curved surfaces away from the drill press, they are nice to have.

Enjoy, DoN.