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12-07-2007, 11:25 AM #1
Sharpening 1 - 3 MT drill bits. Jig plans needed
I just obtained a bunch of 1-3 MT shank drill bits for my lathe. I can easily sharpen most of the smaller bits to 3/4" with my trusty Drill Doctor.
Now I'm, looking for plans to build my own jig to sharpen the larger 2-3 MT shanks. I already have nice large bench grinder.
I would use the jig for mainly grinding lathe tool bits and drill bits.
I've seen many great plans online, but nothing dedicated to sharpen bits with Morse Tapers.
Any help to locate free online plans would be appreciated.
12-07-2007, 12:23 PM #2
You might take a look at the mechanism used on the Lisle 91000 drill grinder. They work well but the geometry of the mechanism certainly isn't real simple and would require a lot of work to make. In any case, MT drills are held on the margins for grinding and not on the taper shank. The overhang length would make it near impossible to grind a MT drill without serious chatter. As long as you make provision for an end stop that allows you to turn the drill over to sharpen the 2nd edge while maintaining the same relative length position of the drill, the grinder will never know whether its grinding a straight shank or a MT drill.
12-07-2007, 01:02 PM #3
Rod, I get good results on large MT bits from my Sterling Drill Bit grinder, like this one;http://cgi.ebay.com/Sterling-Twist-D...QQcmdZViewItem By the way, the eBay seller listed his grinder as a model DV, with variable point grinding angles, the one in his photographs is not a DV, it is a DBF with fixed 118° point angle.
Even though the larger shank of an MT will raise the centerline of the bit at the tail a little, unless it's a large MT with a small diameter bit, (which I successfully shim with an appropriate piece of angle iron), the grind comes out quite well. It's fast too, the set-ups are quick and with no collets to buy for a "hundreds" sizes, it's cheap to operate. It will actually grind up to 3" diameter, as stated in some of their info, while another of their notes pegs it at only 2-1/2" I've ground 2-7/8, had a little left over.
Unless you can find a Sterling for considerably less than that gentleman bid, (I did, considerably!), I'll bet that you could come close with your big grinder and a scale-up of the old General drill bit grinding attachment, still only a few bucks at the hardware as a model.
To duplicate the features of the Sterling, you'd need to provide for X and Y movement of the holders pivot point and grind on the side of the wheel. I'm sure you know that there are steel backed cup wheels made for this. Also, Sterling provides fine adjustment for the stop that engages the flute to register the bit. The adjustment changes the relationship of the stop to the center of the holder.
Check out McDonoughs site here. Should you find a Sterling, they are still very much in business and are very prompt at shipping parts, nice folks, ain't Chineses cheap though.
If this intrigues you, I could provide detailed photos of mine with notes.
If your finances are unlimited, buy a new one from the nice folks at McDonough, keep a domestic machine tool business, in business.
Last edited by Robert Campbell Jr.; 12-07-2007 at 01:14 PM. Reason: Added note re; model in ebay photos.
12-07-2007, 02:30 PM #4
Thank you both for thoughful suggestions.
I have looked in both the Lisle 91000 drill grinder and the Sterling Drill Bit grinder.
Both meet my needs, but are priced conciderably outside of my meager budget.
The General drill bit attachment sound and looks like somthing I can mock up in my shop and would use exclusively for sharpening 1-3 MT shanked bits.
I'm still receptive to other jigs or other sharpening methods which are a low cost solution.
BTW, Robert, any relation to cambelldesigns.com?
12-07-2007, 02:31 PM #5
I meant campbelldesigns.com
12-07-2007, 03:00 PM #6
No Rod, that Bob Campbell is way more sophisticated than I. I'm just an old mad inventer with a home proprietary prototype foundry and shop.
By the way all, when attempting to join this board with "BobC" it refused to accept several iterations of my name. I eMailed Don but before he could reply that all of them should be available, it had accepted the name I've since used. I'd recently lost my wonderful and talented 93 year old father and unlike in my ignorant youth, when I definitely didn't want to be a "Junior", I now proudly honor my much loved father with our shared name. Nothing fancy, 'cause I'm not and I won't live long enough to fill his shoes.
12-07-2007, 04:05 PM #7
Rod, I first used one of the General sharpening fixtures when I was in high school about 40yrs ago. I think the one I had was sold by Sears, but it was the same thing. I've always thought they work surprisingly well to cost so little, so long as you pay attention to what you're doing. It would have to be scaled up to work on the larger drills, but its so cheap to buy that getting one just for measuring purposes would be pretty easy to justify. If I were going to do that, I'd set it up and actually use it a bit first, so I could identify the wobbly areas and give them some extra attention on the upsized version.
12-07-2007, 06:05 PM #8
If you have the ID number, eBay listings will usually last quite a while after bid closing. Within several minutes of my correcting the mislabled model of Sterling drill grinder, as the much more expensive variable angle pointing model, (it wasn't) the listing disappeared from eBay.
Doesn't matter as I already had it printed to hang next to the $75 bill-of-sale for my nearly new Sterling. Why parts from the manufacturer for a NOS tool? The bellows boots had disintegrated and I don't want grinding grit on the moving shafts.
Hope it wasn't one of you guys in an honest mistake but I'm thinking he reads the forum, or has eBay started yanking all completed auctions in hours?.
12-07-2007, 06:49 PM #9
I have one of the Lisle 91000 that my dad gave me. Works pretty well. Just really time consuming to set up for each bit. You might be able to buy the holder section as a spare part from Lisle.
The company is really nice to deal with. I needed the little magnet gauge and web guide for mine and it came to $8 with shipping. I also needed new bit size sticker for mine and she sent them to me N/C.
I have seen these machines sell for over $400 on ebay. Then again I regularly see used square hole 5C collets sell for $36 to $42. These things are only $37.25 new right from Hardinge. Geesh...
12-07-2007, 10:03 PM #10
I also went the route of reverse engineering the General drill grinder .
I used my homade contraption for years untill I got a sterling for $249 at auction .
The thing to remember about a General /mock up /clone , is that you will need to adjust the
front locating plate that the flute rests on , so it rotates the drill slightly from small to larger drills . This is required to maintain the clearence angles . I think the Sterling does this by changing the pivot point . They do a good job of describing the variable geometry required to properly sharpen a drill , if you can get Sterling to fax you a manual , it would be educational .
12-08-2007, 12:32 PM #11
I also have a Sterling drill grinder , the fixed 118* model. It would not be to hard to modify to the adjustable model. Mine is old, 1943 according to the maker. It works very well for me.
I got it from a local who worked at the local Cominco plant. When it closed they offered all the maintence tools to the employees.
My sharpener has a double shaft motor on it, one end is for the drill grinder, the other has an adjustable grinding table on it. Kind of a carbide grinder set up.
12-08-2007, 05:16 PM #12art_deco_machine Guest
Is this the grinder?
Sterling Twist Drill Ginder ebay
Note the letter as to why the auction was pulled.
I have that part of a grinder that holds the bit. It came out of the junk. It doesn't look exactly like that one on the Sterling.
12-08-2007, 06:44 PM #13
Seems like all MT3, and most MT2 are good candidates for hand sharpening.
The MT1 go down small enough to be more of an issue.
12-08-2007, 07:25 PM #14
Still very interesting..
Yes Art Deco, that is the same machine, it closed at $1,275. I see he still has it missidentified and as I wrote above, "the eBay seller listed his grinder as a model DV, with variable point grinding angles, the one in his photographs is not a DV, it is a DBF with fixed 118° point angle."
On the Sterling website, http://mcdonough-mfg.com/, going to the "schematic' button then checking the parts drawing, the DV model lists #10 as, "slide bracket" The eBay offering has the fixed neck of the 118° only model.
The DV model "slide bracket" allows the motor/wheel head to pivot about an imaginary point at midpoint on the wheel face, (where the drill bit engages the wheel) in a trunnion effect.
By the way, that micrometer feed for the drill bit is shop installed, not a stock feature. I can't imagine the value of the micrometric feed, as the stock drill feed is fine and a few "tenths" difference in O.A. length of a drill bit has no effect on it's performance.
As to 'both cutting edges projecting equally', the only way to screw that up would be to grind one flute and not the other at the final setting. The micrometric feed won't keep that from happening.