drill bit sharpening

I have one of those entry level drill doctors. SOmetimes, when I
sharpen large bits, the bit comes out with the point ground down. What
am I doing wrong and are these repairable?
Is there a better way to sharpen these?
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Yeah, by hand--really not hard at all--and that's coming from a semi-spas. Harder for really small drills, but then even these drill docs don't go super-small. And easier iffin you got good eyes. But 1/8 and up should be no problem.
Best to let a shop guy show you how. And it's just as quick by hand as w/ these gizmos. bip bip, yer done. Longer if the bit is actually broken.
I've been told that you really gotta pay some bux for a Darex or sumpn, and *even then* you can get disappointing results. ---------------------------- Mr. P.V.'d formerly Droll Troll
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Proctologically Violated©®
Major NG sore spot! Drill Doctors are CRAP!!! One of my guys has one and brought it in and sharpened a bunch of drills that then wouldn't cut. Upon inspection they had a slight negative rake Hmmmm. If you learn to do them by hand, you will learn empathy with the bit and become a better metalworker.
Reply to
Tom Gardner
I have a drill doctor 500 and it sharpens drill bits just fine. They cut as good as new. I am very happy with it, SO FAR.
Reply to
My personal experience differs from your observations.
Can't imagine how that could happen unless he was using it very wrong. The camming action of the drill holder is pretty un-screw- uppable.
Sure, but saying that Drill Dr. is crap because it's fundamentally flawed isn't an accurate statement.
Reply to
Dave Hinz
I have two of these. A 750 bought about 4 yrs ago, and a 400 bought recently. I never could get the 750 to sharpen correctly. The 400 works great. Discovered that the collet holder that came with the 750 was different than the 400's. 400's holder works in the 750. Found out too late that they redesigned the holder and were replacing the old holders for free......Paul
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That has to be some wicked grinder! Rake angle on twist drills is established by the helix of the flute. Therefore, regardless of how the end of the drill is ground, rake angle is not affected.
If you're telling us that the drill was higher at the heel than at the cutting edge and wouldn't cut because the lip was lower than the heel, then I would suggest to you that it had negative *relief*, not rake. They are not the same, and should not be confused.
Reply to
Harold and Susan Vordos
If one guy gets really good grinds from a DD and another guy gets unusable grinds, it does NOT mean that one of those guys is a bozo. It could equally well (and more likely does) mean that the DDs are not manufactured to close tolerances and one machine is bad and the other isn't. There has to be a reason that Darex dropped the DD. I suspect it has manufacturing problems.
Reply to
Grant Erwin
Yes! The following is courtesy of the late and very much lamented teenut:
" Anyone who wants to learn this skill should start large - and I mean 1/2 inch and above. This is a great way to make long drills short.
I believe I learned on a 3/4" taper shank drill..it is a lot easier to see all the angles and begin to understand how they work and interact.
By the way..we had a handy little dohickey to help get the drill lips level. I have never heard it described before..
For the morse taper shank drills from 1/4" up to about 1" diameter, we had a piece of 2" by 1/8" hot rolled steel strap..about 14" long. One end was bent at right angles, about 2" from the end to form an L shape with one 12" upright and a 2" horizontal. In the geometric center of this short leg was afixed a "dead" center..not a lathe tailstock center!!...more like a 1/2" bolt, 1/2" long, turned or ground to a 60 deg point (Approx...no great precision required) and screwed in from the under side. Thats IT..toolmaking over!
In use the inner face of the upright was coated with whitewash (Never SAW marking blue 'til I got in the toolroom!) The drill was ground, freehand, on the FACE of the wheel (not the flat side)...care being taken to keep the POINT angle as equal as possible on both sides..I'll tell you how to do THAT in a moment..
Lets do that now in fact..
Jim, You are dead right about not being able to grind a drill without mechanical help! Well here's how you create your own "6 Million Dollar Bionic Darex" ;^)
Let's assume we are going to sharpen a 3/8" diameter, 2MT shank drill..it is about 8" long (these figures are arbitrary..I just want every one to have the same mental picture of what I am describing. We approach the wheel, which has been dressed on its face, dead straight across with no grooves..(Ve SHOOT anyone ve catch putting grooves in ze drill wheel!!..No Pity..No Prisoners..Ya! Verdampt!)
The drill shank is held firmly in the RIGHT hand...ALL the movement and control is imparted by the RIGHT hand. For the purposes of drill grinding, the left hand could be...with benefit..a LUMP OF CLAY!!
It is from this "lump of clay" that we fashion the Bionic Darex".
Place your left hand thumb and forefinger tips LIGHTLY together..Relax the other three fingers and let them naturally curl against the palm of your hand. Let the drill flute drop into the vee between thumb and forefinger and let the tip of the finger "Find" the curve of the flute where it fits comfortably. The tip of the thumb rests on the sharp junction ot the land and the flute, about an inch back from the drill tip.
Now...SQUEEZE HARD!!! YOUCH!...I said it would be easier if it were clay! 8^) Lift the drill from your fingers...see the GROOVE?...Drop the drill back in..it locates within a thou or two! Magic?..Bionic at least! Squeeze again to set the groove. You have created a customised drill guide that fits better that that on any machine ever built! You can relax your grip now..feel how smoothly the drill will ride back and forth, guided by the groove you have created for it.
Place the knuckles of your left hand, LIGHTLY on the ginding wheel tool rest, and swing the drill shank, from left to right (using ONLY your right hand) and push the drill lengthways though that groove in your fingers back or forth using the groove to make the drill twist or "rifle" in your fingers. Do NOT move your left hand in any way..it is made of clay remember!
A) The drill axis is "eyeballed" to be at half the required point angle to the wheel face...You can scribe or chalk reference lines on your grinder benchtop to help you line this up..at least untill it become almost second nature.
B) The drill axis is dropped JUUUst below horizontal. This will ensure that your soon to be ground drill lip will start with a "smidgin" of cutting clearance.
(Ideally, and certainly for a beginner, the grinder rest should be set dead radially to the wheel center and about half the drill diameter below the true center of the wheel)
C) The two cutting edges of the drill..the straight, sharp bits, formed by the junction of the flute and the back face (the only bit you grind), should be horizontally disposed..with the edge uppermost on the side closest to your left hand..the other sharp bit of course, pointing downwards (Jeeze this would be a lot easier with a sketch pad)
This I will call the SET or START position!
NOW, move your left hand for the first, last, and ONLY time during this whole exercise. GENTLY ease the cutting edge towards the spinning wheel, carefully maintaining all the angles and orientations of the SET position..until the cutting edge is JUST shy of touching the wheel. If you listen carefully you will hear the tone of the entrained air, whistling through the narrowing gap. You will hear a subtle but distinct change of tone JUST, I mean Just...a couple tenths of a thou BEFORE the edge touches the wheel. STOP!!! FREEZE!! DO NOT MOVE!!
Now, press the knuckles of your lump of clay..sorry, your left hand FIRMLY down onto, into and around the grinding rest..establish a "Groove" on the back of your hand as well as between your fingers.
We are now ready to grind, Your left hand locked to the drill and grinding rest is otherwise quite relaxed..letting the drill slide, twist and tilt wherever your right hand and the groove in your fingers tell it to go.
The actual grinding is a bit of an anticlimax.
You have previously studied a new drill point, you have read about clearance, and cutting angles, and rakes and......
With the RIGHT hand in control, gently, kinda, lean forward... bending or squeezing your arms hands and body..rather than actually moving them..untill you take up that last couple of tenths and the wheel begins to cut. Let it cut..don't force it, and don't rush it..it really won't hurt anything if you take a full minute per pass per face. YOU and your "Bionic Darex" are totally in control of that drill and the wheel..Forget the times when, close to panic, you swung the drill wildly past the wheel, hoping to get "the dirty deed" over with as quickly as possible.
Take your time, enjoy the moment, THINK about the shape you are trying to generate. Just the one face is left to "Interpretation"...every other aspect,angle, facet, what have you...Has ALREADY BEEN TAKEN CARE OF!! and is locked in place under your control!
The right hand should perfome a "Lower Quadrant sweep" for want of a better term. An observer behind you would see your hand move from about 17 minutes past the hour on a clock face, to roughly 25 minutes past. But it isn't a smooth arc of a circle, more a sector of an elipse..You see, as your hand starts to drop slowly, you are also rotating the drill in "the groove"..the first third of the turn needs to maintain that very slight clearance angle on the cutting edge, and not increase it too rapidly.
You need the clearance to cut..But too much at that point will WEAKEN the edge, and cause the drill to snatch and chip...So the first part of the rotation is ALMOST but not quite, just as though you were grinding a straight cone point on the end of your drill. Only as you approach the second third, does your right hand start to noticably drop..kinda "Catching Up" on the rotary motion...increasing the clearance as it does.
In the last third of the rotaion the right hand drops quite rapidly..Thogh not enough to catch the OTHER drill lip on the wheel..that lip is coming around quite rapidly by now.
Above all, take your time, if it helps, move the drill one degree at a time, and think ahead what shape or angle the next degree of cutting face needs...Remember, you have control, and IT ain't going nowhere 'til you decide.
After a pass on one face, flip the drill in your "Bionic Darex" DO NOT MOVE THAT LEFT HAND!!, return to SET position and repeat, the pass on the other face.
Having done a couple of passes on each face..it is now time to check the results on our homemade "Optical Comparator"
(Sorry Jim I couldn't resist!!) ;^)
Rest the center hole in back end of the drill shank, on the center point of the "Comparator" and use, first one and then the other drill lip to scribe a light line on your whitewashed (OK Blue or red dyed) surface.
You will readily see if the lines coincide..if the lips are even..or not, as the case may be.
Lets assume they are..Now look directly DOWN on the end of the drill to check the clearances. HUH? How can you check radial clearance by looking it staight in the face? Surely you need to look at it sideways?
Well no you don't...for once all those interacting and confusing angles and faces and clearances are going to work together in YOUR favor and make what could be a tricky bit of metrology..quite simple. While we are looking at the end of the drill, we will also check that the POINT ANGLE is correct too!!!
(Ok guys, leave quietly..teenut has finally lost it!!)
No really, trust me. IF you look straight down on the point of a well sharpened, standard drill, you will see the two cutting edges, joined by the CHISEL edge which crosses over the web of the drill. The angle fromed by the chisel edge to each cutting edge should be ABOUT 50 deg...anywhere between 40 and sixty is ok for a first attempt. (I can hear the purists and theorists screaming and lighting up their flame throwers.) But believe me, get it in that ball park and your drill will CUT. If the angle is too steep..you don't have enough clearance...negative clearance will give you an angle event greater than 90 deg. Too MUCH clerance and the angle will appear too shallow!
While looking at the end, check the point angle, How? Look down the axis of the drill at the cutting edges. Are they straight? If so, your point is pretty close to the right angle (As designed for that drill, by its manufacturer when he set the helix angle and the cross section of the flute) If the edges appear CONCAVE the point is too flat and if they appear CONVEX, the point is too "Pointy"
If your drill passes all these tests, which take but a second or two to perform, THEN IT WILL CUT..pretty close to size, without chattering, chipping, overheating, wandering or seizing. I guarantee it!
Hey, thats a pretty good start for the first drill you ever ground! All it takes now is a bit of practice for it to become second nature and almost as easy with a little 'un or a big 'un!
Hey guys!
My apologies for "goin'on" but If it helps just one person to pluck up the couragre and go hand sharpen his (or her) first drill, by hand...
Then I hope you will bear with me.
It is late, I am tired and I am not even going to proof or spell check this,
'night all
teenut "
Reply to
Ted Edwards
Well, they could be using it wrong. If you don't get the depth of the bit as compared to the camming surface correct, all bets are off. That'd be my guess as to where the most likely error would be made.
If you were familiar with the mechanism, you'd understand why that statement is nonsensical.
Yes to the former, I doubt it to the latter. An injection mold isn't going to change randomly from unit to unit, so user error is much more likely than manufacturing problems. A distributor chosing not to sell a particular product can happen for any number of non-quality-related reasons.
(shrug?) Mine works great, for what it is. I just don't like seeing one person's bad experience be expanded out to badmouthing an entire product line.
Reply to
Dave Hinz
Everyone should read it twice.
Reply to
Karl Townsend
It is possible that the bad grinds could have come from user error and not manufacturing tolerances. You are being a bit sensitive when you say that what I wrote was nonsensical. More accurately, it is logical, but you assert is is unlikely. OK. It's just another point of view. Have I looked closely at the Drill Doctor? No. I have a better drill grinder.
Dave H> >
Reply to
Grant Erwin
I've managed to come up with good grinds as well as bad grinds using my DD. Not orienting the drill properly will absolutely cause the trailing-edge-higher-than-the-cutting-edge problem mentioned earlier. I've found that when I pay attention to getting the drill positioned properly, that the DD does a very nice job. It can be a little persnickety, but ninety five percent of the time I get a good result on the first try.
Reply to
Peter Grey
I'm truly embarassed!
Reply to
Tom Gardner
Don't forget I'm biased and cheap!
Reply to
Tom Gardner
I believe the inconsistency on the Drill Doctors is due to the method it uses to rotate the drill to the correct angle so that the cam mechanism will put the right relief angle on the drill. If the drill is rotated incorrectly you will not get the right angle on the point.
The mechanism used to set this angle is a pair of sheet metal edges that come out and are supposed to squeeze the drill inbetween the flutes and rotate it to the correct angle.. I'm not convinced that even if it was consistent that this method will work correctly for all drill sizes, but even aside from that I'm having problems getting the drill rotated to the correct angle to get ground properly.
I would prefer if they just showed you which angle the drill is supposed to be oriented in the collet so you could do it by eye, but I guess I'll have to play with the thing to figure that out.
On some drill sizes my Drill Doctor is working ok, but on the size I actually needed it for I'm also getting the wrong relief angle.
Paul T.
Reply to
Paul T.
Except that it does not seem to do a good job with the split-point drill sharpening with the smaller sizes.
One thing to watch for, however, is that it is sensitive to the helix angle. The common jobbers' style bits work fine in it, if it is used as it should be. Those with either lower or higher helix angles wind up mis-positioning the flutes, and can wind up with excessive or negative relief as a result. (What is needed is a couple of more index marks for those differing helix angles, and matching detents.
Enjoy, DoN.
Reply to
DoN. Nichols
It should be said that I'm using my DD on standard run-of-the-mill drill bits, so your observations are undoubtedly correct.
Reply to
Peter Grey
Reply to
Harold and Susan Vordos
When you put the drill in the alignment clam you have to look down on the sheet metal clamp jaws and besure they are still aligned. If the drill is canted or not correctly inserted the jaws will be offset. I get really good results with mine and I learned to sharpen drill bits by hand a long time ago. I just can't see well enough to do the itty bitty ones anymore. Glenn
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