Four/Six Facet Drill Sharpening Fixture for Surface Grinder - Recommendations?

Can anyone point me in the direction of fixture for surface grinder to sharpen drills using four/six facet method, with split point? I'd like something that is quick and easy to work with and rigid. Ideally this would take only slightly more time to set up and sharpen than hand sharpening the same drill, but I'm ok with a bit more. I don't want to be wasting my time with anything finicky.

I'm sure some will chime in with "Get a tool and cutter grinder" - and I know that's an option. But I'll need some convincing that another piece of iron taking up space in the shop is better than a little fixture for an already great/versatile machine.

And just to head off the ones that will say "Just run to the belt and sharpen it by hand". Sure, I'm quite good at this too. However, sometimes I want a near perfect drill bit without fussing to get it just right.

And no, I don't want to keep a cabinet full of brand new drill bits. Even the occasional brand quality drill bit can be found to be ground incorrectly sometimes, or the geometry isn't right for the application.

I'm happy to hear other constructive opinions and options.

(Edit: A wider size range would be ideal, but more reasonable would be maybe 1/8" to 1" - but only up to 1/2" could be a good compromise on the right unit)

The topic of drill sharpening has been covered in great detail here. Do a search using the search term "drill sharpening" and you will get 7 pages of results.

Tom

TDegenhart said:

The topic of drill sharpening has been covered in great detail here. Do a search using the search term "drill sharpening" and you will get 7 pages of results.

Tom

Click to expand...

Thanks, I've done plenty of reading through search results here and did not find an answer to this specific question. I am looking for something far more specific than "Drill Sharpening". Lots of people refer to using Vee blocks or jury-rigged setups on their surface grinder and this is not what I'm after.

If you know of a specific thread I've missed I'm sure you'll be kind enough to post a link for me.

Hi Sparky961:
I looked around for years to find something that would work well and came up with nothing.
I ended up with a home made fixture using an ER collet chuck with indexing flats on it, mounted into a steel block with a reamed hole at the proper angle so I could just put it on the magnet, push it against the rail, and sidewheel my primary reliefs in about 30 seconds.
The rest of the point was usually put on by hand, but I did make a split pointing fixture, that was just another block with a reamed hole in it to accept the collet chuck and present the point at the proper position for split pointing.
I got rid of it years ago and bought a professional grade Darex (not sure about the model number...I think it's SP2500).
Works brilliantly and is even faster.
Cost me about 1300 bucks Canadian on Fleabay.

Beware of the Darex M4 M5 bench grinder models that look like they'd adapt to your surface grinder...I bought one and it's crap.
Ditto for Drill Doctor.
But the SP models work well, or at least mine does.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com

implmex said:

Hi Sparky961:
I looked around for years to find something that would work well and came up with nothing.
I ended up with a home made fixture using an ER collet chuck with indexing flats on it, mounted into a steel block with a reamed hole at the proper angle so I could just put it on the magnet, push it against the rail, and sidewheel my primary reliefs in about 30 seconds.

Click to expand...

Thank you. This is helpful.

I'm considering putting together something similar, but with a bit more complexity and versatility. The purpose of this thread is primarily to make sure I'm not wasting my time reinventing the wheel. If there *is* something out there, or a starting point to be worked with, I'd consider that route before going through the time and expense doing it myself.

Hi again Sparky:
I went for the virtue of simplicity.

ER collets because they're accurate and can clamp over a big range.
A store bought straight shanked collet chuck with a 3/4" shank and a little flange so I could grind two flats at 180 degrees to one another for indexing. (Mine was a Command brand chuck in ER 20 with a 2" long 3/4" diameter straight shank and a very short collet nose to flange back dimension)

A lump of steel (probably 4140 HTSR) squared up, nicely ground and with two bored and reamed 3/4" holes at the proper angles.
Also two shoulders to engage the flats on the collet chuck flange
I put nylon tipped setscrews to clamp the collet chuck in position but ended up never using them and just held the collet chuck in position by hand.

A little sheet metal finger for setting up the lip to be horizontal. (I used the opposite lip to the one I was grinding).
I abandoned this too and ended up just eyeballing the lip to be horizontal...it made zero difference to the performance of the drill unless you were miles off, and the two accurately ground indexing flats on the chuck meant what you did to one flute you did very accurately to the other flute too.

I always sidewheeled the primary relief so I could do drills of any length by just hanging them over the front edge of the magnet, and I split pointed with a plunge grind, hanging the shank of the drill over the RH end of the magnet.
A nice open 46J aluminum oxide wheel with a fast dress and a dished rim for sidewheeling was my wheel of choice.

I originally intended to have more reamed holes in my block to be able to do secondary reliefs too, but I abandoned that as well and just freehanded those...so long as my primary relief was spot on symmetrical, the drill would cut brilliantly.

Facet sharpened drills perform just as well as form relieved ones do, but they're more fragile and will not last as long before they need resharpening.
The greater amount of HSS removed from just behind the cutting edge is the reason...they tend to hold the heat from drilling right at the cutting edge.
Overall though they do perform well so this is a worthwhile investment of effort in my opinion.

So if you keep it simple and drop the idea of spindles and bearings and positioning fingers and gazillions of super dooper adjustments, it'll work very well, and it's quick and cheap to make.
I think I spent maybe half a day, but I already had the collet chuck.

The critical thing is to get the fit between the shank of the collet chuck and the bores very nice, get the distance from each indexing flat to the centerline exactly the same, and get the indexing shoulders on the block accurate enough that the chuck will just push into place with a tiny bit of resistance.
Stone a couple of radii on the flange and the corners of the indexing shoulders and the chuck will pop into position solidly, release easily and spin smoothly when you index from flute to flute.
Relieve everything so there's room for the grinding dirt to accumulate without piling up on the reference surfaces or in the corners and make the reliefs so you can easily wipe the dirt away with a small brush from time to time.

Spending effort to get this just right is where the money is; all else can be rougher than guts and still work, but I hate dealing with rough looking tools so I made mine pretty and nice to hold.
If you want to Cadillac it, you could make the body hardened, but mine was used for years in the HTSR condition and it stood up well.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com

Marcus:

Thanks for your excellent description/discussion of the subject. I need to stick this one on the back burner for a little while to handle some other things. But I fully intend to come back to it, and I'd certainly appreciate bouncing some ideas off of you at that time.

Thanks..

From a hobby magazine.......Model Engineer's Workshop, had a few build articles with a purpose built fixture for a surface grinder.......

look at a royal oak relieving attachment

there are lots of challenges to this. Collets don't grip over a long enough portion of the lands, especially with larger drills. You of course need to be able to index things 180 degrees and also have fine adjustment so you can get the facets parallel to the lips.

Here's what I came up with. Case hardened and ground V block withy micrometer tooth rest. Tooth rest and drill end stop mount to the V block with split cotters, fast and convenient. I use it on a T&CG (Yes you need more iron) but it could be easily adapted to a surface grinder.

V block is used on a universal positioner, also by yours truly. The trick to accurate drills is a good grind that is symmetrical....this does so. Drill bits drill within a couple of thou

what is the micrometer for? you would set the edges parallel to whatever plane you work in and push the tooth against the flute, no?

o.k., if you do more than a touch up, the angle is going to change and you get a "wrong" chisel angle. is the micrometer there to compensate for that? you would have to know by how much to compensate depending on how much you feed in. on the other hand you could just anvance the drill in small steps rotating the flute against the tooth.

Shown below is the result of a few different design iterations, researching similar designs, and lots of subconscious thought processing. Many an hour of sleep has been lost thinking about this project, for better or for worse. It has been a bit consuming, but I like when a project draws me in.

If you just want to see pictures and comment on what you see, skip past my ramblings below. However, I may have addressed some design features or pitfalls already and you could avoid looking silly by reading everything before you comment.

I'm looking for input on problems I may not have considered, and things that could be done simpler/easier/faster/cheaper/better. Maybe there's a $50 widget I can buy that does everything this fixture does and more - but I sure haven't been able to find it!

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The design goal, was to create a fixture to grind a four facet point on drill bits using a surface grinder. I decided on using ER25 collets, which limits the range from about 2mm to 16mm (5/32" to 5/8"). I wanted to make it accurate, fast and easy to use, and rigid as possible.

In my research, and a question or two on this and other forums, I was not able to find any existing fixture design that holds the point of the drill stationary between grinding the primary and secondary facets. This means, for all I can tell, that you need to carefully sneak up on getting the point to match in the centre without going past. If you do, you have to grind the primary facet again, trying to get it in the centre. If there's nothing I'm missing that makes this process fast, accurate, and easy then it's no wonder the go-to answer is just to sharpen your drills by hand on a bench grinder. (Yes, there are times this is the answer, but there are times when more accuracy and repeatability are needed)

The fixture I've designed (actually it isn't quite finished yet) allows the drill bit to orbit around the point. Once you have the vertical axis of the fixture aligned to the face of the grinding wheel, you leave it there throughout the grinding process. The best way to use it would be to have a bunch of drill bits to sharpen, as aligning the fixture centre point to the wheel is probably the most time consuming and most critical part of the process. Not that it's difficult, just that how well it is aligned dictates how well the point is formed. Any material removal adjustments are done by adjusting the fixture, as are the angles to be ground. Indexing is also provided for by the fixture, so after grinding one facet it is easy to rotate exactly 180° to grind a second cutting edge. Provisions for setting multiple hard stops at certain angles will also be added to the design.

Throughout the iterations, I tried to keep my focus on the design goal, but clearly this fixture has other potential fixturing uses on and off the grinder. I am keeping those applications secondary at the moment so as not to distract from the original intent.

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Some of the things I'm not completely comfortable with in the current design iteration:

- Rigidity is questionable. I plan to add stiffening connections between the linkages, but I'm not sure this will be rigid enough. Unless another solution presents itself though, I'm willing to try building it.

- Holding the drill in an ER25 collet is simple and uses off-the-shelf collets, which is a big plus. However, this may not provide enough clamping surface on the margins of the drill. There's a chance it may cause excessive wear or damage, but I think this is remote.

- With small diameter drill bits there is probably not enough clearance past the collet nut for the wheel with 1-2x diameter protruding from the collet. A pin vice or similar device could be used here to stick it out farther without excessive overhang.

- Locking all of the linkages in place in a rigid and repeatable way may be difficult, though I have some ideas to try out here.

- Grinding dust will probably get into everything. Maybe it won't be an issue, but maybe it will. It might just be something I need to try.

... And finally, PICTURES!

For scale reference, a 5/8" jobber length drill is shown in the fixture.














My thanks for your constructive critique.

Hi,

I recommend you looked at proper/commercial grinders that do 4 facet.
Have a close look at the Italian Cuoghi Micra 10, it´s a nice grinder and I actually have one myself. The classic Optima grinder I believe is essentially along the same lines but I have not seen it up close.
Am not 100% sure of your resulting drill point geometry, it´s not going to be same but maybe it works. In your 3D-cad, cut it with a plane simulating the grinder wheel in the diferent positions.
Also you may want to change the sizing so you transverse the drill at centre or near centre height of the grinding wheel hence grinding perpendicular against the edge. That upsscaling may help you get more robust bearings as well.
At the moment I´m actually building a "copy" of the Micra grinder to set up on my T&C grinder. It gives two robust bearings, more easy to achive gives me a geometry I know is proven.

Mcgyer, you made a very nice drillgrinder hat´s off to your workskill!
However it lacks the feature for ensuring that the intersection between 1st and 2nd facet intersect in centre of drill automatically, as can be seen in your pictures. I´m sure it´s a bit of hazzle to get it there?
The big drill looks great but the two smaller needs some more work.

One of all 4 facet grind pics out there...
https://www.tormek.com/media/138933/4facet_drill_bit.jpg

The Micra grinder
Sharpeners MICRA 1 INTEGRAL – Sharpening Machine for HSS and Carbide Drills

so how do they achieve "automatic centering"?