Member postings for Jss

In MEW issue No. 241, on the contents page, there is a reference to J Hugel's drill grinding tables being available on this website. Does anyone know where they are as I can't seem to find them?

John.

Thanks for that Colin, I'll check that out.

John.

Edited By Jss on 18/03/2016 18:49:33

I thought I'd resurrect this thread as I seem to be having the same problem that peak4 has had.

Many years ago I bought one of these made by Picador:

It was left unused until I read Harold Hall's book on tool and cutter sharpening and after one or two modifications I managed to get some reasonable results.

Recently I bought a kit of parts, from a well known auction site, for a Potts drill grinding jig. I bought it because it would be an interesting project to build and also Tubal Cain in his book on drills taps and dies said it produces drill points "very near to perfection".

Some of the parts were already machined and as far as I can tell are in accordance with the drawing supplied (from Woking Precision Models).

The jig is now sufficiently complete to be able to give it a try, however the result is disappointing.

The drill on the left is an untouched 3/8 inch drill as supplied by Presto, the centre one is a 23/64 inch drill (Dormer) that has been sharpened on the modified Picador jig and the one on the right is a badly worn 10mm drill of unknown parentage that I'm trying to sharpen using the Potts. On this the relief angle is now much steeper than the first two and looking directly at the point the chisel angle is wrong also. This seems to indicate to me that the drill point is too close to the axis of the jig pivot, giving too small a radius on the ground surface of the drill. This can be confirmed by putting a straight edge on all three drill points and comparing the curvature.

When using the Picador the minimum distance of the drill point to the pivot axis is about one inch, any less and you end up grinding the tip of the jig off. On the Potts it is much less than this:

This is part of the drawing as supplied by Woking Precision Models. The scale is full size and appears to show the jig set up to grind a 1/4 inch drill. It's not too clear in the side view, but the pivot axis is only just (by about 1/4inch) behind the front of the jig which is where the drill tip should be.

Peak4, did you manage to sort your problems? I have the set up instructions if you're still looking for them. Can someone who has one of these tell me where I'm going wrong?

John

Thanks for the welcome, folks!

Hi Phil/John I'm just outside Goole.

Hi Brian, sorry no, but I do live next door to a real ale pub!

John.

Edited By Jss on 13/03/2016 18:17:27

Hi there, I've been following this forum for quite a while now, but this is my first posting. I retired two years ago from being an electrical engineer with the local electricity board, a job I had since leaving school.

The sum total of training I've had to use a lathe consisted of one day making a plumb bob (which I still have), the rest I have picked up from books such as the excellent Amateur's Lathe by L H Sparey and various Workshop Practice Series books. At one point I thought it would be a good exercise, when working at the lathe, to imagine what Sir John would say if he were looking over my shoulder, but the thought of all that laughing put me off.

Workshop tools consist of a Myford M Type lathe, a Drummond(?) hand powered shaper, Coronet Major woodworking lathe, small horizontal bench mill and the usual hand tools. Virtually everything has been bought second hand or inherited.

Most of the time I make tools but I have made a small oscillating engine from plans in a Model Enginneer 's special publication:

I just need to think of something for it to power, nutcracker, pencil sharpener...?

At the moment I am trying to make a Potts drill grinding jig, about which I have some questions but will post these on another thread.

Regards to you all John Smith..