grinding drills

Background:

A long time ago I bought two bench grinders from Grainger. They are 8 inch belt driven grinders. And I like them because they are slimmer than ones with a motor between the two wheels. And i also like the size. 6 inch wheels seem to be a little small. I also have a 10 inch grinder so I am not lacking for grinders. The 10 inch one has two regular wheels. One of the 8 inch ones has a wire brush and a abrasive cut off wheel. And I just made another stand and plan on that 8 inch grinder having a fine wheel and a rubber contact wheel that uses sanding belts.

I have had a General drill sharpener fixture for ages and decided to figure out a way to use it with the fine wheel on the 8 inch grinder. So I was rooting around on the internet looking for instructions for the General fixture and ran across several videos of how to grind drill bits by hand. I can grind drills by hand if they are not too small. I taught myself. Anyway I watched a couple of the videos and saw that the videos show a somewhat different way to sharpen drills.

When I sharpen drills I start grinding on the heal and finish at the cutting edge. Both videos showed the grinding starting at the cutting edge and ending up grinding the heal. So I am curious how most people grind drills by hand.

I mounted the General fixture a bit different from the instructions. It is rotated 90 degrees from the usual position and the cutting is done on the outside of the wheel. So the drill is in about the same position as it would be if sharpening by hand. Somehow grinding on the side of the wheel seems wrong. This does have the advantage that any grind marks are perpendicular to the cutting edge. Not really a big deal as fine stone is 100 grit and the grind marks are pretty much invisible.

The big advantage is that the fixture stays on the adapter I made and the adapter mounts quickly in place of the tool rests using wind nuts. So the fixture is not in the way, yet is easily put in place.

Dan

Reply to
dcaster
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wrote

I can start from a precise position more easily than stopping in one.

jsw

Reply to
Jim Wilkins

I start with the cutting edge and kind of "roll" the bit against the wheel. I shade the bit tip with my hand and hold it up to the window and rotate it to see that the grinding is equal on both sides. Both corners should disappear at the same time on the same level. Then I look down on the tip to see that the tip is centered and both sides are the same.

Reply to
Tom Gardner

Also, it's easier to overheat the edge if you start at the heel.

Personally, I grind the primary, the secondary, then finally I split the point.

Reply to
PrecisionmachinisT

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Dan

I hand grind on the OD face and always start with the cutting edge first. It helps me set the position I want. My drill bit grinding is always a work in progress. Sometimes I mark the bit with a magic marker to help to tell me how the bit is cutting and what edge to re- dress. There's a video of a homeowner-type German-made bit sharpener that I'd like to try (but I don't know if it's available in the US):

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Reply to
Denis G.

In memoriam... Best post ever from Teenut:

Subject: Re: drill sharpening FAQ? From: Robert Bastow Date: Mon, 11 Oct 1999 07:59:04 GMT

Intro snipped.....

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!)

(Sorry)...

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 finger tips LIGHTLY together..Relax the other three fingers aand let them naturally curl against the palm of your hand. Let the drill flute drop into the vee between thumb and fore finger 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!

UNTIL....

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 othe 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 th is 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 dont' 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 thos interacting and confusing angle 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
Karl Townsend

Yes, very good, however, I say switch right to left and vice versa. Then It makes sense to me... ;>)} phil k.

Reply to
Phil Kangas

That drill sharpening jig is one of many machines that KAINDL markets in Europe.. I don't know of any US or Canadian distributors, but there may be a few.

I saw that same jig, new, for sale on eBay.de for about 180 EUR (225 with the grinding disk in the video).. search kaindl-de. No mention of shipping to the US.

In many fixtures/sharpening jigs where the drill doesn't rotate during grinding, it's necessary to adjust/relocate the rotational position of the drill as the point is being ground back toward the shank, since the twist usually isn't being followed. When grinding drill points by hand, it's an automatic adjustment made in the motion of the drill, but clamping a drill in a fixture typically requires resetting adjustments as the drill is shortened.

It seemed odd to me, that in the video, the holder/drill were moved forward, then tipped up slightly - making the drill off-axis with the guide.. maybe the operator doing the demonstration wasn't familiar with drill sharpening, or the purpose of the guide.

Reply to
Wild_Bill

Thanks for the info on the machine. It's a little on the pricy side, but it's also elegant and seems to do the job simply and well.

Reply to
Denis G.

Good one Karl, you beat me to posting it.

My copy has been formatted and most line feeds have been removed.

I really miss Teenut's advice.

Alan

Reply to
alan200

I split a gut when I read Teenut talking about V shoot anyone grooving the wheel and still get a tear in my eye just thinking about that line.

Somebody was going to make a best of Teenut compendium, don't think it ever happened.

Karl

Reply to
Karl Townsend

In general I do not like video's of how to do things. They take too long to view. But a video of teenut grinding a drill would be really nice. If someone did a video showing the actions while teenut's post was read, that would almost be as good.

=20 Dan

Reply to
dcaster

On May 15, 11:09=A0am, "PrecisionmachinisT"

I agree that it may be easier to overheat the edge if you start at the heel, but with a good wheel it is not a problem for me. I rarely am doing much more than touching up the drill using the fine wheel. Any significant amount of grinding is done on the coarse wheel.

Dan

Reply to
dcaster

I find it easier to watch the sparks to see if I am taking off an equal amount across the cutting edge and adjust accordingly. So starting with the heel works for me. But I think the main reason I do it the way I do is that rotating my hand down seems more natural than rotating my hand up.

=20 Dan

Reply to
dcaster

wrote

-In general I do not like video's of how to do things. They take too

-long to view. ... Dan

Reply to
Jim Wilkins

wrote

-In general I do not like video's of how to do things. They take too

-long to view. ...

-Dan

See if you like this one:

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jsw

Reply to
Jim Wilkins

I am certain that Scott Logan did a compilation of Teenut's posts to RCM but I'll be darned if I can find the link.

Reply to
grmiller

Link:

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Reply to
Denis G.

Reply to
grmiller

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