Author Topic: More tool projects.. (Potts drill grinding jig)  (Read 10079 times)

Offline Bjorn_B

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More tool projects.. (Potts drill grinding jig)
« on: December 01, 2015, 03:47:42 PM »
Got this today...
« Last Edit: December 31, 2015, 03:09:01 PM by Bjorn_P »

Offline mcostello

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Re: More tool projects..
« Reply #1 on: December 01, 2015, 03:51:04 PM »
Some assembly required! :Lol:

Offline Bjorn_B

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Re: More tool projects..
« Reply #2 on: December 01, 2015, 04:16:00 PM »
Yes. And a lot of headscratching  :thinking: :headscratch:

Offline vcutajar

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Re: More tool projects..
« Reply #3 on: December 01, 2015, 08:22:12 PM »
Interesting.

Vince

Offline Bjorn_B

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Re: More tool projects..
« 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  :happyreader:
Might substitute one casting for flat stock...  :thinking:

Offline Bjorn_B

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Re: More tool projects..
« 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!

« Last Edit: December 31, 2015, 03:12:06 PM by Bjorn_P »

Offline vcutajar

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Re: More tool projects.. (Potts drill grinding jig)
« Reply #6 on: December 31, 2015, 04:38:21 PM »
Quote
Might substitute one casting for flat stock...  :thinking:

Any particular reason for making it out of bar stock?

Vince

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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!

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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.

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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.

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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.
« Last Edit: January 03, 2016, 08:04:23 AM by Bjorn_P »

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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  :happyreader:

Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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!


Offline Bjorn_B

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Re: More tool projects.. (Potts drill grinding jig)
« 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

Offline vcutajar

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Re: More tool projects.. (Potts drill grinding jig)
« 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

 

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