jig problem

Sorby folks....is there any response to this? Adie is referring to my workshop (I'm the friend) and as a consequence of seeing my pro-edge in action he bought one. I think it would help if we could respond to his question (even if the straight answer is a no it cant be done).

Many thanks

Rob

I asked Jeff pretty much the same question some time back because I had come from a Tormek background where all manner of aids and pre-set protrusion setters can be purchased. His answer on how to control the bevel angle and the wings for any grind you care to repeat is pretty definitive in my view. Somewhat (necessarily) technical but precise and accurate so well worth reading and re-reading until it all makes sense. Here it is. Incidentally, his final recommendation for the protrusion settings of the elliptical jig are what I have now adopted for my spindle gouge long grind. If I want a very pointed nose for fine details (if I'm working with Holly for example) I just grind the sides a little more and keep off the nose. If I want coves or smooth curves I'll grind the nose rounder by focusing more effort on it.

Here's his comprehensive response:

The original design of the ProEdge aimed at reproducing the factory grinds precisely. If you leave the jig as it is delivered and follow the instructions in the book, you'll produce exactly the profiles found on Robert Sorby Fingernail Gouges when they come out of the package.

That said, like Tormek or Oneway Wolverine or pretty much any elliptical grinding system, three things affect the gouge profile. the amount of tool protruding from the front of the jig, the angle between the tool axis and the rotational axis, and the distance between the point of rotation and the abrasive contact point. A change in any one of those settings will affect the length of the wing and the bevel angle of the grind.

Unfortunately, the adjustment of those three things doesn't affect the profile on the ProEdge in exactly the same way it affects the profile on any other system. On all the rest, the adjustments move the contact point along the arc of a curve (the grindstone). On the ProEdge, the contact point moves along a straight line, rather than a curve. Bottom line, you can't look at the settings in Tormek's book and get the same profile with the same settings on the ProEdge.

With all that as a disclaimer, the knuckle adjustment (which controls the angle between the tool and the rotational axis) has the greatest effect on the wing length. The protrusion and the distance from the contact have the greatest effect on the bevel angle, but also affect the wing length.

If you decide to alter the settings of the fingernail jig from the way it is delivered, make sure you can get it back to the factory settings before you do! Before you move the collar, use a scribe to scratch a line on each side of the collar so you can put it back right where it was. The knuckle adjustment should be at setting number 4, but since the scale is a bit crude, I scribe a tiny line across the parts so I can bring it back accurately and quickly.

I have a spindle gouge ground to a rather long bevel with a fingernail profile. It's what most people would call a detail gouge. It's not exactly the same as the factory standard fingernail grind, so I had to experiment to find the right settings for it. I use a 75mm (3 inch) protrusion, the knuckle is at setting #3, and the back collar is 1-5/16" (34mm) from the end of the shaft.

If you have a favorite profile that you're trying to reproduce on the ProEdge, here's the process I used to arrive at those settings.

1) Take the belt off the ProEdge.
2) In general, if you want a long bevel, work with a long protrusion, short bevel, short protrusion. Use standards you can repeat easily.
3) In general, if you want a short wing, use a lower number on the knuckle scale. If you want a longer wing, use a bigger number.
4) Put the jig in the boss and adjust the back collar until the bevel lays flat on the platen when the tool is at dead center.
5) Roll it from side to side, observing the contact between the bevel and the platen.
6) Adjust as necessary to have contact all the way around the bevel, keeping in mind that an adjustment in one setting will most likely require a slight tweak to at least one other.

Hope this helps rather than complicates.

Thanks for finding that, Rob. Saves me going through all of it again, which I was getting ready to do!

This reminds me of something I learned in a sales course sponsored by my employer, the telephone company, back in 1976.   The instructor made the comment, "Good salesmanship is educating the customer as to what the product can do for him." With proper education and a need, a good product will sell itself.

Ken

Bill and I had a punt at Adie's 30 degree bevel detail gouge today using my 1/4" as a template. I must say the pro-edge isn't particularly user friendly if you want to set a known bevel angle like this.

What would be a welcome aid is a little published chart with all the common grinds boiled down so their settings can be dialled into the jig in terms of tool protrusion, collar setting (distance from end of shaft) and which hole in the long boss or just use the short boss.

What we started with was trying to hold a protractor to the chisel whilst in the boss and laid up against the belt but with both the knuckle and the protrusion lock knob loose enough to match the bevel with the angle on the protractor.

That was a mugs game so next up we set the platen to 30 degrees and then eyeballed a parallel match of the straight of the chisels shank with the angle of the platen while the tip of the bevel was touching the belt. We tightened up the necessary knobs and allen bolts and ground the bevel with 60g ceramic to move metal quick.  (Removing the platen first of course).

This method of arriving at the correct bevel angle seemed to work close enough, not perfect but I think good enough. We encountered a problem which is that in order to get a 30 degree bevel the protrusion setting for the chisel beyond the shoulder of the elliptical jig was huge and consequently you can't reach all the way round the left wing (as you're looking at the machine) because the metal bar that holds the boss doesn't have enough travel beyond the belt so the handle was knocking up against the motor housing. The right hand wing grinds over the right side of the belt and that went far enough round to finish the wing.

Now I haven't personally used this 30 degree bevel angle and its not for the faint hearted but Adie is an experienced turner and the desire is to be able to tuck the tool into very fine details. That acute angled bevel leaves very little metal on the nose, allowing the desired access to fine details.

So, Bill in his inimitable "just make it yourself" style has already invented a wooden mod which will dog leg the tool further away from the housing to solve the problem...on paper only thus far.

My question is this:

Is this a known challenge and does Sorby have any suggestions? Also does that little published chart with the settings of various known grinds exist somewhere?

??

I am afraid this forum died a death from lack of user interest, Jeff was the Sorby rep, and he did comment on the thread, but only to thank Rob for putting up the answer.

Jeff has also contributed plenty on many threads, and been helpful on many occasions. So it was a valid attempt to get a community up and running, but the users didn't really get involved enough.