Author Topic: More tool projects.. (Potts drill grinding jig) (Read 10156 times)

Bjorn_B · « **on:** December 01, 2015, 03:47:42 PM »

Got this today...

mcostello · « **Reply #1 on:** December 01, 2015, 03:51:04 PM »

Some assembly required!

Bjorn_B · « **Reply #2 on:** December 01, 2015, 04:16:00 PM »

Yes. And a lot of headscratching

vcutajar · « **Reply #3 on:** December 01, 2015, 08:22:12 PM »

Interesting.

Vince

Bjorn_B · « **Reply #4 on:** December 01, 2015, 08:29:13 PM »

After some studying I must say that the plans are very very good, I even understood most, if not all of the original Van Royen article from 1913 that was included as a photocopy

Might substitute one casting for flat stock...

Bjorn_B · « **Reply #5 on:** December 31, 2015, 03:03:57 PM »

Made some machining on the "drill guide base" today, so far no major problems, only one angle to keep track of so far. Dug out an old friend and made one milling job on the lathe. Otherwise done in the mill in a standard vice or clamped to the table.

Groves are "1/4 with a 5 mm slot for a stud

I really need one of those digital box protractors now, can't seem to find them anywhere over here, import again!

vcutajar · « **Reply #6 on:** December 31, 2015, 04:38:21 PM »

Quote

Might substitute one casting for flat stock...

Any particular reason for making it out of bar stock?

Vince

Bjorn_B · « **Reply #7 on:** December 31, 2015, 04:47:46 PM »

Was the casting I did above that I thought to substitute, but it went ok!

Made a mess out of one of the base castings, but that could easily be replaced by somthing else, pipe fittings spring to mind!

Bjorn_B · « **Reply #8 on:** January 02, 2016, 10:37:27 AM »

Getting a bit more complex now. Hole for pivot is drilled/reamed at a 41 degree angle to the top surface of what will be the bottom half of the drill fixture platform. The centre of the pivot where it intersects the plane at the top surface will be the reference mark for all further machining of this piece. Will need a cunning plan on how to hold this piece for that. Trying a few ideas in my head, but it will probably be a fixture that clamps the pivot shaft at a 41 degree angle from horizontal in the vice. Pivot shaft is loctited to the casting.

Bjorn_B · « **Reply #9 on:** January 02, 2016, 10:43:23 PM »

After considering options, I squared off the pivot boss an was able to hold the casting in a vise. Vise was clocked at the same angle as the top drill platform and a groove was machined for a key. The top platform slides along this to adjust the backing of radius/offset for different diameters of drill to be sharpened.

Bjorn_B · « **Reply #10 on:** January 02, 2016, 10:52:58 PM »

Next is the drill holder vee block. As I find it difficult to cut a v-grove to exact depth and in an exact position I started with the vee and will machine the casting with the vee as a reference point. After squaring up the casting it was set in the mill with the head tilted 45 degrees, head can only be tilted sideways on this mill (+/-45 degrees) there is allso no knee and the head vertical movement has no fine feed, only quill.

Bjorn_B · « **Reply #11 on:** January 03, 2016, 11:30:55 AM »

And this is how far I got this morning. It is getting a bit tricky and difficult to judge how to proceed from here. The bottom and front edge of the v-grove is to be aligned in some way or the other to the rotational axis of the pivot when the drill platform is set for a zero drill diameter. This is not totaly clear on the drawings, I'll have to have another read in the Van Royen papers

Bjorn_B · « **Reply #12 on:** January 04, 2016, 05:51:56 PM »

As the quick-mill project is on hold in search of preload washers for the spindle bearings, here is a bit more on the potts drill grinding jig.

After studying the Van Royen papers some more it is clear that a zero diameter drill would have a zero radius cut with zero offset. So with the jig set up for a zero diameter drill the tip of the drill would aligtnwith the rotational acis of the pivot shaft. This means that the front edge of the bottom of the grove should align with the pivot shaft or ideally be slightly behind it.

Of to work then, first job, mill for clearance of the grinding wheel in the head on position (31 or 59 degrees depending from where one counts)

There must allso be clearance when the jig is swung around (to 45degrees), the vice is set at 45 degrees to the table and the spindle about 22 degree to match the cut made earlier. This is a compound angle that allmost caught me out. It would perhaps be easier to setup on a tilting vice, but I do not have one and headroom is bit of an issue with my mill. I don't use the rotating base for the vice either as the graduations on that are really bad.

After some cleaning up the setting caliper and anvil was bolted to the platform. Might adjust the position of the clamp screw (still a temporary one in the picture), it limits the drill diameter to 9mm right now. A position further forward would increasa capacity to 12 or even 12,5mm

Cheers!

Bjorn_B · « **Reply #13 on:** January 05, 2016, 05:03:59 PM »

Feed screw assembly, a bit over engineered in my view, but then again, why not?

There is a lock thumbscrew to be added on top. And a thumbscrew on the bottom to lock the assembly itself to the drill platform

vcutajar · « **Reply #14 on:** January 05, 2016, 05:08:38 PM »

Does not look like it is a simple kit to do especially when it comes to machine those angles.

Vince

Bjorn_B · « **Reply #15 on:** January 05, 2016, 05:22:51 PM »

Hello Vince, it is not all that bad, but there are no instructions as there usually is in kits from Hemingway. Only some short notes, the plans are good thou. Most headscratching comes from thinking over how to set thinks up. A tilting vice or an adjustable angle plate would help a lot in my view.

Thanks for checking in, premiere grind on the worden soon?

Bjorn_B · « **Reply #16 on:** January 18, 2016, 10:02:05 PM »

Drill platform is allmost done now, just the lip rest to do, but that will not be done until it is finished. Next part is not very exciting, a casting with two holes drilled and reamed at an odd angle, 59 degrees if I remember correct..

Edit, 72 degrees, pivot should be set 18 degrees from vertical

vcutajar · « **Reply #17 on:** January 19, 2016, 11:00:23 AM »

It will be interesting to see how it will be fixed to the grinder. It think the Worden has the facility to use it. What drill sizes does it take?

Vince

Bjorn_B · « **Reply #18 on:** January 19, 2016, 07:13:33 PM »

Quote from: vcutajar on January 19, 2016, 11:00:23 AM

It will be interesting to see how it will be fixed to the grinder. It think the Worden has the facility to use it. What drill sizes does it take?

Vince

Hello Vince! It is nothing very fancy, a couple of cast bits bolts it to the bench next to a ordinary bench-top grinder setup to grind on the side face of the wheel, a cup wheel would be best here I guess.

I'm pretty shure it is possible to grind four facet or split point gemetry twist drills on the worden, it would in most cases be superior to the "cone back off" geometry that this jig will produce. I have done split points on my quorn, but is somewhat of a hassle to set up, thus most of my drills are a bit dull...

Bjorn_B · « **Reply #19 on:** January 23, 2016, 03:48:03 PM »

Done!

There is two settings to be done fore every diameter of drill to be ground:

First picture, setting the platform offset (shank of drill is used for this)

Second setting is jig to wheel clearance (done by eye), this has to be done for every drill diameter because the first setting advances the platform in relation to the pivot. I have a hex bolt for this right now, but I found a ball handle that I must have made when I did the quorn, I will adapt that so there is no other tool needed to use this.

Thinking about raising the grinder on some sort of platform in relation to the grinding jig so that the direction of grind is more favourable, it is now more or less parallel to the cutting edge. I believe it would be better to grind allmost at the 6 o clock position on the wheel.

Drill range seems to be from about 3mm to 13mm

Holt · « **Reply #20 on:** January 23, 2016, 04:13:29 PM »

Quote from: Bjorn_P on January 23, 2016, 03:48:03 PM

Thinking about raising the grinder on some sort of platform in relation to the grinding jig so that the direction of grind is more favourable, it is now more or less parallel to the cutting edge. I believe it would be better to grind allmost at the 6 o clock position on the wheel.

Quietly following along, I have used commercial versions of this type of grinders, and all used the nine'o clock position of the wheel, maybe your idea would make the wear of the wheel more even, as it seems there is quickly forming a groove in the wheel when used in the traditionel way.

Holt

Bjorn_B · « **Reply #21 on:** January 23, 2016, 04:47:45 PM »

Thanks for commenting Holt, my concern for wheel wear is quite the opposite with this jig. The working space on the wheel can be set anywhere when the second setting is done. The pivot does not have to be vertical, only the angle towards the wheel is of importance and thus a new position can be set everytime the horizontal bar is adjusted for platform to wheel clearance. If I use a position nearer to the bottom of the wheel, things will become more static.

I have never seen a jig of this type ether that is not using this position. Even the big KEF drill grinding jig at work uses the same posision. Can't understand the geometry of that jig thou, it's a very odd one, the pivot tilts away from the grinder, a lot...

Bjorn_B · « **Reply #22 on:** February 14, 2016, 03:42:20 PM »

And this is what it has done to my drill inventory...

20160214_135530 by Bjorn Pettersson, on Flickr

I'm happy!

Doc · « **Reply #23 on:** February 14, 2016, 03:57:26 PM »

Looks like it's doing a good job!

Bjorn_B · « **Reply #24 on:** February 14, 2016, 04:40:16 PM »

Quote from: Doc on February 14, 2016, 03:57:26 PM

Looks like it's doing a good job!

It really does! Can sharpen up a drill in a minute or two now, can't compare to a four-facet job, but better a sharp traditional drill than a boxfull of dullies..

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Author Topic: More tool projects.. (Potts drill grinding jig) (Read 10156 times)