Black Diamond Grinder @ $150: Must-Buy or Useless?

[spro]

I think freehand grinding skills are rewarded. I also think that knowing how the Champ works, introduces a person to a way of looking how the feed at three angles works against a precision, side cutting wheel. I think those wheels ran fast, dry and cool.

[ken572]

Steve,

Black Diamond Drill Grinder (Forum)

Great Pictures and Info.

http://www.practicalmachinist.com/vb/ma ... er-267231/
and
http://www.blackdiamondgrinder.com/
and
http://www.sterlingmachinery.com/3528/Black+Diamond+11/

I think it's a GREAT Value.. at $150.00

Ken.

[SteveHGraham]

I don't want to be perceived as arguing about this, since I have never used one of these things, but the manual (which, I'm sure, is unbiased) makes it sound like the Black Diamond is pretty simple to operate. You put a bit in a collet, put a collet in some other thing, use yet some other thing to set it accurately in the second thing, and grind away. I think.

[SteveHGraham]

Nice links, Ken. Thanks.

Looking at the PM (I'm not worthy I'm not worthy) thread, I see that the model they're discussing only goes up to 11/32. At first I thought that was a bummer, but now I'm thinking it would actually be a selling point, since smaller bits are harder to sharpen by hand.

[spro]

I agree with that. The larger types benefit from being in a cradle to establish key equal areas but then...I must go back to what has been filed here, which is better than I can even describe. There is an art to freehand grinding and using the outside of the wheel. Somewhere between that skill and the key registers provided by fixtures, should make that skill easier to attain.

[earlgo]

Not to be forgotten is the General 825 with which I have had some success. For me, better than hand sharpening, but far less accurate than the PolyChoke fixture (if one happens to have the right collet). Easier to set up than the Darex 305, but limited in the small drills. Works great for larger drills up to about 3/4 or so. I should mention that I use it on my Delta Toolmaker so there is better control on the in-feed. Having said that, as with any fixture, one needs to be aware of the limitations.



http://www.generaltools.com/825--ORIGIN ... p_213.html

--earlgo

[SteveHGraham]

One of the reasons drill sharpeners interest me is that I can't make myself believe I can sharpen a drill as well as a machine. We always talk about a thousandth here and a thousandth there...the drill gauge I bought will probably get me with 10 thousandths at best. I keep thinking the drill bits will wander around in deep cuts if they're not perfect.

[ctwo]

One of the reasons drill sharpeners interest me is that I can't make myself believe I can sharpen a drill as well as a machine. We always talk about a thousandth here and a thousandth there...the drill gauge I bought will probably get me with 10 thousandths at best. I keep thinking the drill bits will wander around in deep cuts if they're not perfect.

I sort of expect them to wander anyway.

[BadDog]

Exactly. A drill is a drill. When I didn't have access to the machines (or now when I don't), hand sharpening is still an option.

[Harold_V]

I keep thinking the drill bits will wander around in deep cuts if they're not perfect.

Assuming a drill has reasonable geometry, the reward, or lack of one, for poor grinding tends to be oversized holes, not wandering.

Wandering is characteristic of twist drills, even well sharpened. Gun drills are often used when a straight hole is required. A lot depends on the degree of precision required, and depth of the hole.

Harold

[ctwo]

Harold, are you saying that twist drills will wander anyway, yet yield a proper size hole; but a poorly sharpened twist drill yields larger holes as well as wander?

I guess I take it wandering means the hole kind of bends off axis. I was thinking of wandering as perhaps what we call when an end mill wings? I thought I read something like that here a while back.

[BadDog]

Winging an EM is due to cutting pressures and the fact that it can cut on it's sides.

In the ideal, a twist drill generally cuts on size as the almost unachievable perfect ideal, machine sharpened or no. Various things cause problems for twist drills, and everything that causes deviation causes over size cutting. The easiest to see is when the point is off center. The point will try to stay in the center, and the radius of the hole will be roughly the tangent of the longest cutting edge, depending on exactly how the point is oriented (chisel, split, or faceted), and whether there is a pilot hole. There is a LOT to read about how/why twist drills don't drill on size and/or straight. But the gist is it always happens to some degree, the question is whether or not it exceeds your tolerance.