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Post by Rob on May 2, 2014 20:34:35 GMT
Hi Jeff
I've recently become a pro edge owner and I have the "regular" fingernail grind jig but I've not yet tried the Ellsworth one. I've also never actually used an Ellsworth profile on a gouge so am keen to give it a whirl. Does the Ellsworth jig grind a kind of "standard" ellsworth profile out the box or do folks mess about with longer, shorter, different variants of the ellsworth grind? |
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Post by Graham on May 2, 2014 20:48:54 GMT
Thats what I want to know for mine as well. I have the longer jig bar but not sure how to do the els worth with it.
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Post by Jeff Farris on May 2, 2014 22:55:02 GMT
The long grind jig attachment makes for a longer "wing" on your side-grind gouges. Using the out-most hole will provide a side length very close to what most consider an Ellsworth grind.
Just as an aside, while working for a different company, I bought "Ellsworth" gouges from 4 different manufacturers. None of them matched.
Here's my theory on side grind length. There are two reasons to grind a bowl gouge to an elliptical grind. One is to increase the cutting surface so you can remove stock faster. The second is to create an edge that can be used for shear scraping. Any wing length greater than about 5/8 of an inch is eventually going to get you in trouble on mission number 1, and really isn't going to contribute very much to mission number 2.
If you're going to grind an enormously long wing on your gouge, make sure you know why you're doing it.
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Post by Rob on May 3, 2014 10:06:25 GMT
Well, my current personal standard fingernail grind fits well with your description. I've always been curious to try the Ellsworth grind....so in your words....I don't know why I want to try it :-)
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Post by Jeff Farris on May 3, 2014 10:24:42 GMT
Rob,
If you're partial to Robert Sorby bowl gouges, please, try an Ellsworth grind. You'll be cutting away the tool about twice as fast as you will with a more normal wing, sending you back to the shop for a new RS gouge just that much faster. lol
Joking aside, a lot of folks find the long wing easier to shear scrape with, but if you examine the cut you're making while shear scraping, the contact area between the work and the tool is just a whisker. All a longer wing will do is aid in aligning the contact point...sort of like training wheels on a bicycle. I've tried it many, many times, and always come back to a ratio of the side wing length being just about equal to or ever so slightly longer than the diameter of the tool.
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Post by Rob on May 3, 2014 10:43:47 GMT
Yup that makes perfect sense. After all, unless there's a slight convex radius on the wings, they're at a tangent to the bowl side aren't they. The point where the tangent meets is the point at which the sheer scraping is happening. It sounds like (given you've clearly experimented with them) that the whole ellsworth thing is a bit like those razor adverts on TV....every year there seems to be more and more blades. I saw a comedy sketch once where the guy picks up the Wilkinson sword 26 blade razor...proceeds to cut his head off with one swipe :-)
Maybe veritas, with their april fools posts will publish a bowl gouge which is ground all the way to the handle on both sides :-)
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Post by Graham on May 3, 2014 18:47:48 GMT
Training wheels.
Thats it. I knew I was missing something.
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Post by Graham on May 4, 2014 7:35:13 GMT
Getting back to the original post and the els worth grind. Are we any further forward with the desired position of the settings on the fingernail jig ?
Rob has the ordinary one that comes with the machine, I have the longer 3 hole version, but what about the collar settings etc on the 'pole' ?
So far I haven't found any reason to move them but they are presumably there for a purpose ?
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Post by Rob on May 4, 2014 7:53:47 GMT
I've been pondering that too Graham. I left the collar where it was when I bought the tool and my personal preference for protrusion of the gouge from the jig clamp is 65mm. That gives me the same fingernail grind I had setup on my Tormek. Despite the curiosity about the ellsworth grind I must confess that 65mm protrusion really suits me. There's plenty of cutting surface to the sides but its not so big that its difficult to control due to too much stock removal. I think Jeff's advice on that is pretty sound to be honest.
So....if you change the protrusion of the gouge from the clamp, you change the angle of the bevel. What I can't fathom just by 3d modelling it in my head as it were, is what does adjusting the collar change? I've not had any spare time to experiment with this. My original assumption was that it would change the amount of side grind but given you need a different boss for the ellsworth jig than that doesn't make sense. Sure Jeff will explain in due course. This is where I found the documentation falls short and why I think this forum will be such a useful knowledge exchange.
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Post by Jeff Farris on May 4, 2014 14:45:57 GMT
Short answer first. As I said in my first reply, use the outmost hole in the three hole version of the boss and you'll get a long wing like an Ellsworth. No adjustment necessary on the protrusion, the jig angle or the collar.
Now, the longer answer.
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.
The adjustments are present because Robert Sorby, Ltd. buys the fingernail jig from Tormek. We felt they had the most effective design and rather than try to work around their patents, we chose to buy the jig from them. If we produced the jig ourselves, the collar and the knuckle might not be adjustable at all.
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 somewhere around setting number 3 or 4, depending on where the index is scribed on your unit. We use a fixture at the factory that sets the angle at 120 degrees. Since the scale is a bit crude and the pointer seems to move from one batch to the next, I scribe a tiny line across the parts so I can bring it back accurately and quickly if I make an adjustment.
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.
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Post by Rob on May 4, 2014 18:16:36 GMT
Wow...you're a couple steps ahead of me. I went in the workshop today to try and fathom this and the first thing I did was take the belt off to eyeball how the bevel made contact with the platen. I find if you go to each extreme of adjustment, its impact on the bevel becomes more obvious. So I messed around with both collar and protrusion and essentially its the same process as using a sharpie with wheel based grinders, except by eye. Oddly enough I was trying to see what effect it had on a detail spindle gouge. I also don't have the 3 hole boss because my PE was 2nd hand and that jig wasn't supplied. My boss has just one hole and of course the hole for sliding onto the holder. I will purchase the longer boss in time.
But just as you say Jeff, the 3 planes of adjustment were as you explain with much adjustment in one also having a small impact on the others. So marking the jigs is critically important for repeatability (or using stops for protrusion as I do).
That's handy. I now know which way is up in terms of grind adjusting. The great thing about the PE is because of the grit change flexibility, I can freely experiment with different grinds without the dread of a laborious shaping grind to restore the one I lost while experimenting. Really excellent.
Many thanks for that superb explanation also Jeff hit the nail on the head as usual. I thought I recognised the articulated gouge jig too. Now I know why :-)
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Post by Rob on May 5, 2014 14:31:50 GMT
Well Jeff I can now report that I gave your detail gouge settings a whirl and its a great grind. The wings were longer than my original settings and I've allowed a more pointed nose. It really allows access to tight "corners" on finials and other close up work. I'll adopt that from now on if you don't mind :-)
Again, the simplicity coupled with the speed really lets you experiment with different takes on a grind like this without having to be worried about the dreaded reshaping exercise taking all night to reverse it if you don't like the new grind. That alone justifies the PE to me because I'm yet to settle on my "perfect" grinds for different situations. This freedom to explore different grinds very easily, with literally factory quality on the bevel is something I'm really enjoying.
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Post by Rob on May 5, 2014 17:00:42 GMT
Note to Graham......I strongly recommend you do a trial grind using Jeff's suggested settings for the detail spindle gouge. This afternoon I tried it on a 1/4" spindle gouge which already had the wings ground back. But this grind takes them about 2mm further and leaves a more pointed nose if you don't spend too much time on the tip. I messed about with a finial on some oak and its absolutely fabulous for crisp detail, sharp points, deep but small valleys etc. More capable of getting in the crevices compared to my original detail grind which I've been using for over a year now.
edit: To save you looking them up, here they are: Protrusion = 75mm, knuckle setting #3, distance from back edge of collar from end of jig arm = 34mm. I ground mine using 180 grit paper and it took all of a minute if that (though it did have an existing fingernail grind though not as exaggerated as this profile). I took Jeff's advice and lifted the arm to just off vertical which fixed the left hand sweep hitting the switch problem. |
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Post by Graham on May 5, 2014 18:01:56 GMT
Hi Rob.
I will certainly give it a go. Cannot get at the lathe at the moment as I had to do an emergency demolition of a partition wall in my workshop ( separated my chunk from SWMBOs bit as it was about to collapse.
Should be gettable by tomorrow night.
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Post by Rob on May 5, 2014 19:14:44 GMT
LOL...good man :-)
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