Small Drill Sharpening
I got dozens of drills from #71 to 3/32" that are anywhere from blunt to just a little dull. Is it worthwhile to send them out for sharpening. I can't afford to have them cut oversize, and they're good quality. Whadda you think, and who does it?
Unless they're "special" somehow (coated, parabolic, cobalt, etc.) I would just toss them and order new. Good quality bright in that size is at or below the cost of pro sharpening. Hand-sharpening small ones like these, while possible, is probably not going to get you a good result unless you have a pro-style sharpener.
Yup, toss them---my way. I'll pay shipping. PM for address.
Drill Doctor !!!
There is no easy way to sharpen drills without a special tool or spending hundreds of hours developing a custom grinding setup OR spending hundreds of hours practicing so you are SO incredibly skilled you can hold the drill bit at the exact right angle to the grinding wheel without moving (yes, thats what they did in the old days).
The cheapest option is a Darex that cost about $1500.
I'm no longer sure that the conventional wisdom expressed by jscpm is still correct in these days of low cost USB microscopes.
Simple flat single facet honing jigs for baby drills have been described by many reliable sources and are reported to give adequately acceptable results if the drill is correctly aligned. OK maybe not to quality brand factory fresh standards but certainly back to somewhere in the first quartile of the drill life. Which is a lot better than blunt as more than acceptable for most work.
The devil in the detail is of course "correctly aligned" closely followed by inspection of the results to verify that the drill really is sharp with an accurately centred point after the specified "few strokes on the stone", in need of an unspecified "few more" or, worse, slight modification of the alignment to get a centred point. I tried it just enough to know it can be got to work and to confirm that it was all far too much trouble and faffing about for Mrs Fosters little boy in the 1980's!
Seems to me that exploiting the visibility and working area convenience of a USB microscope makes it practical to rethink things by mounting the drill in an accurate carrier and using two honing guides to give a four facet tip. By its very nature a four facet tip is far easier to inspect for accurate centre than the conventional variety. Given enough magnification that is. Although it is in principle possible to mount up a drill in a carrier viewing through a conventional microscope its a right PIA and not really practical. A simple bore should do to hold the carrier in the honing jig with a wing and pin to get the alignments mutually correct with a few thou twixt wing and body so the drill can drop down as you sharpen. Were I to make one I'd arrange things so as to take a fixed amount off at each sharpening session by, for example, honing until the wing drops onto the main jig body. A couple or three thou should be enough.
The devil now is in making it very fast and very easy to mount up the drill in the carrier. Realistically anything more than "a couple of minutes" to sharpen the drill is too long. Far as I can see there is nothing in the device itself requiring more than careful workmanship. A Vee groove and nearly pointed push bar will retain the drills just fine.
Honing jigs fall into the category of "spending hundreds of hours developing a custom grinding setup".
Originally Posted by Clive603
Hundreds of hours sounds way OTT for what can be a pretty simple device. I was thinking in terms of following a published design, should one exist, or even being able to purchase ready made at a reasonable cost. However were I to have both need and desire I'd expect to have Mk1B, i.e. good enuf for me to use, designed and made in the proverbial week of evenings. Then maybe write up the Mk11 for the Home Shop mags and get a few sheckels in return.
7 to 10 major parts ought to work for a basic unit to cover a reasonable range of sizes:-
Two bodies bored for the drill carrier with a flat top and Vee bottoms appropriately angled for the two facets. Vee so as to do both sides at a single set-up by flipping.
Cylindrical drill carrier with Vee recess to hold the drill, four facet hone means the drill doesn't have to be central so prolly no more than three needed. Less if you aren't going micro tiny.
Vee ended gripping shoe to slide into the drill carrier and hold the drill in place. One for each size.
Alignment wing, one for each drill carrier and a pin for each each main body. Or equivalent arrangements thereof.
Simplest version rubs the bottom body on the stone so its sacrificial hence changing thickness need to be accounted for. Stepping the bottom of the body and providing two rails for it to run on with a thou or so clearance from the stone is a bit more work but avoids body wear.
Nearly as easy to flip things and move the stone or a diamond lap would be just as good.
Hardest part of the design is sorting the retainer for the Vee groove grip system. There were some elegant, simple and accurate interpretations around in the early days of fibre optics which would probably be worth investigating / stealing. I've handled some but didn't pay enough attention to the mechanical details.
If memory serves me correctly a decade or more ago DAG Brown described something of similar concept in Model Engineer. At the time I recall finding the design a little over complex and the use of collets to hold the drills excessively tricky in construction. As described it was only single facet hone and, inevitably at that date, the arrangements drill registration inadequate as well as slow. Should be a good starting point tho' as, apparently a fair number were built and the constructors happy with the outcome.
I have Huot cabinets full of bits, and I think the little ones cost around $.40 each last time I bought them from MSC. I have a couple of SRD 80-S sharpening machines with microscopes that can do no. 80 to 1/8" bits. Those grinders sold for several thousand bucks when SRD was still making them. It takes a minute or less to sharpen a bit and is incredibly easy.
But I just pull out a new bit when I need one. I don't want to take the time to clear bench space so that I can set up the grinder to salvage a 40 cent bit.
I use a Drill Doctor 750 for little drills and for the most part is better than my Darex M5. It's quick and doesn't take much bench space. Bigger drills are another matter. The Darex is much better for them. The DD 750 can be found pretty cheap. I bought one on eBay for $50. Even though I already had one that cost $140 or so - I just couldn't pass it up.
From about #60 on down I sharpen them all the time.... I use a flex shaft with a fine emery cut off disc and a jewelers loupe...... run the thing fairly slow..... maybe a 1000 or 2000 rpm..... just hold up the drill and get it at the right angle and give it a little twist, rotate 180 and do it again without moving the angle of your hand. Keep in mind with a 7 or 10X power loupe I am holding the shaft about 2" from my nose, I kind of brace my hand against the side of my face to keep it steady. Takes a few seconds...... then test to see if it drills nice, you'll know right away... there is either a nice chip coming up or there is not... should be even on both flutes. I will admit it does take practice...... yesterday I touched up a .012" a few times....... Larger than #60 I grab a new one.
I just sharpen them by eye,wearing 4X drugstore glasses. I hold them against a sharpening stone(fine cut) which in held vertically in front of me. The drill is presented,visually checking the angles,and the stone moved up and down.
To drill all those little holes in the steel heart jewelry die,it was on a Sunday,and I broke the #80 drill several times. Just ground it off square,then re set the angles by eye. Got the job done when I couldn't order a drill quickly enough. And,who pays postage for 1 #80 drill?
Actually, you are too late ... sort of. The last two issues of HSM have shown a design for a 4-facet sharpening machine. I think the design could be improved on, but it looks to me like it should work. As I've read it, I've wondered about modifying the basic idea to work on a surface grinder.
Originally Posted by Clive603
That said, if you are looking at a design just for honing, it might be different enough from the HSM series to be worth pursuing for publication.
"And,who pays postage for 1 #80 drill?"..... the question should be who buys just 1 at a time? I thought the reason they sold them by the dozen is because they make them TOO break ;^)....... really I agree with George that anyone who uses small bits in a manual machine should know how to sharpen them.... might be different in a CNC circuit drilling machine that runs at high speeds. I did meet a guy once and flew a thousand miles just to see his shop...... he specialized in drilling small holes, most less than .008" in very tight and accurate (.0002") grids in vespel, he did this on new CNC retrofitted Moore jig bores....... just plain amazing! I learned a lot that day.
BTW I spent about an hour yesterday digging a .018" broken off bit out of a piece of brass....... I knew I should have made an extra of that part. That is much worse than sharpening these things.
Have you ever tried boiling the part in Alum? We use lots of #71s. When we break one off in silver or gold we boil it for as long as it takes for the embedded chips to melt away.
rivett608 - I know how to sharpen larger drills to work in brass, but 0.018"?? What form of abrasive do you use on a drill that small? It must have a clean edge..
I use those 1" diameter emery cut-off discs, I like the thin Dremel ones (sorry I can't remember their stock number, they have a thin and heavy duty) because they are kind or course.... I have many finer from other brands and I use those in the DC micro motor. Anyway I use the side of the wheel....... I use these for a lot of things, the import thing is to dress the wheel! works for me.
I have used the Drill Doctor 750 in a shop setting to sharpen 1/2" drill for a production job ( the engineer was agreeable ) and got them sharpened for production.
Originally Posted by clomb
They went through 3 shifts, drilling thousands of balance holes.
Now I only did this when getting the drill sharpened was not possible any other way. But it did work.
But sharping .40 cent drills on as regular practice would not be cost effective .
My track record of late has been pretty good. Broken one drill in the last 400-500 holes in things non ferrous, #70 and smaller. Not always the most controlled drilling setup either. I do always use some sort of a sensitive feed.
Lately I have been using Hertel drills from MSC for the smaller sizes.
Originally Posted by rivett608