Can anyone make sense of this angle question on sharpening using the wolverine?!?

[Joshua Dinerstein]

OK. I am trying to make some platform angle adjustment blocks, wooden wedges, for my wolverine platform. These have been suggested here and in other locations by many people. Herm De Vries was one and Reed/Robo Hippy here at the creek was another.

I have had the last couple of days off of work. Which was sad because it was so freaking hot here that I was just melting and didn't play in the shop. Today finally was different and I took major advantage of it. 4+ hours in the shop this morning and I wanted 4 more but family needs interfered. ;) I got my new table saw all tuned up and it is cutting extremely nicely now! So I cut up some 3/4" MDF into a size to cover the wolverine standard platform and glued them all up.

Now to the freaky part. I decided to set my platform at 90 degrees from the surface of the wheel. No real reason to do that except that at the time it kind of made sense to me. My thought process went kind of "start at 90, cut a block at 45 degrees and you will put a 45 degree bevel on the tool".

Seemed/seems so very simple to me. The crazy part is that somehow I am wrong?!!? I have to be missing something but I can't for the life of me figure out what...

So here is the rest of the setup for this interesting problem. I have a new SRG from PSI. I have the brass angle gauge from from Woodcraft and I checked it. It comes up perfectly 45 degrees. It is nicely hollow ground so I took it over to the grinder and rested the bevel on the wheel until it matched up true. Guess they use an 8" grinder to make them in the first place. I then rotated the wheel down until, with the bevel still mated to the surface of the wheel, the lower section of the tool shaft touches the outer edge of the Wolverine platform. This was to give me the needed info to verify the angle.

OK. So I measured. I get 40mm up from the platform to the lower edge of the tool closest to the wheel. And the platform is 80mm wide. These numbers aren't perfect as I was measuring quick. But it totally thru me. To be a 45 degree angle these need to the same length. Or at least that is what I recall from my HS math class. So I found a simple website and punched in the numbers and I get an angle of basically 26 degrees.

Like I said I don't get it. I have my platform at 90 to the wheel. The tool angle measures at 45 degrees. So how do I have an angle of 26 degrees remaining?

I have been beating my head on this for the last hour and a half or so and I am coming up empty. Anyone know what I am missing? I can just continue to measure and try to cut the wedges somewhat blindly to try and make this match. But I would rather make this work and know why! :)

Thanks!
Joshua

[Joshua Dinerstein]

Ok. I get it now. I am not sure how to compensate for it but I get it now.

I went out to the garage with my brother-in-law and when I was explaining things and standing back from the wheel we realized that the "difference" was that the wheel isn't a plane. I tend to think of it that way as you grind in the center of the wheel. Because of what is going on and the point of grinding being just above the center line there is a greater swing away from the wheel than I had been thinking. And that as far as I can tell is the reason why the angles are off.

So while I have an explanation for the missing angles. I have no clue how to calculate the difference so know how to cut the blocks. Anyone have any ideas on that front?

Thanks,
Joshua

[John Keeton]

Joshua, I think you are going to have to work from the tangent line established by a radius line on the wheel.

[John Keeton]

Forgot to upload the other pics.

[Jim Underwood]

What John said.

You're basically dealing with an "average" because the angle at the tip of the tool isn't the same as the angle at the radius/tangent line, and that isn't the same as at the angle at the bottom of the bevel.


That's why the Raptor jigs are a three point tool...

[Steve Harder]

I found myself dealing with the same issue when I built a larger platform adjustable tool rest for my grinder.

To document an angle setup it seemed easier to set the platform using a tool already ground at the desired angle and then either measure the vertical support to platform angle with a small metal adjustable arm protractor and write result on tool rest -- or cut and then grind to fit a top half of a raptor style guide.

Things change pretty fast as you approach 90 degs.

[Fred Perreault]

Joshua.... your angle calculations would work if you were sharpening a tool as thick as the imaginary lines you used for the calculations for perpendicularity. However, you are dealing with a tangent angle, a radius and curved wheel, and the real thickness of the tool to be sharpened. And some of this would change if the sharpening wheel diameter was smaller or larger, as you are putting a hollow grind on the tool as well.
And this is from a C- math student..... :)

[Thom Sturgill]

Lots of good info. Look at the Raptor guides. They will not only set the cup distance properly regardless of wheel wear, they also set the platform angle. I have seen people who just mark the arm to set it at the same length, but if that worked, OneWay would have pre-marked the arm. Others make square guides to measure a constant distance from the face of the wheel to the cup. That is closer, but still the grinding angle will change slightly with wheel wear since it does not take into account the changes in the tangent line.

[Jim Underwood]

Mike Darlow gives a pretty thorough analysis of this situation in his book Woodturning Techniques if you want to read up on it. I found it pretty informative anyway...

[scott schmidt grasshopper]

oh boy you all work too hard, simple math for this turner, but here is something no one pointed out, why start with a 90 degree platform? better to have say your 60degree scraper angle so without any blocks you already have one set. then you take your example tool set at 45 degrees and put say a 3/4 thickspacer block between it and the platform. does it match the wheel? if too high then shave a little off the bottom till it comes into the right angle setting ( keeping the block flat just making it uniformly thinner)in the end you have the original platform for 60, and two riser blocks to make 45, and 22.5(half of a skew) hope this helps.
ps I still dont think it needs to be perfect, just repeatable I use three differant slopes for my bowl gouges

[David E Keller]

Not sure if I'm indifferent or lazy(or both) when it comes to this issue, but I fail to see the need for such precision in sharpening my tools. I think as long as I'm in the ballpark, I'll be fine. I may be wrong, but I doubt that many of us could tell the difference between two bevel angle that were 5 or 6 degrees apart. Even if I could, a slight adjustment in the presentation of the tool to the wood would likely negate any subtle difference.

Am I missing something?

[John Keeton]

David, that is pretty much where I am. I use the exact same setting on my Wolverine for my bowl gouge, and my spindle detail gouges - somewhere around 42*. I am sure it is wrong, but it seems to work fine for me.

But, I come from the flat world where guys are tuning their table saws and handplanes to the .0001. Never understood that either.:confused:

[Joe Bradshaw]

Joshua, I am more dense than usual today. I don't understand your problem. When I sharpen my SRG, I stick the end of the handle in the V holder and slide it in or out until the bevel is fully on the wheel. I usually blacken the bevel with a magic marker so that I can see where the wheel is touching. I adjust the v arm until I get full contact. It's quick and easy. For my bowl and spindle gouges, I use the vari-grind. I have one set for my spindle gouges and one set for the bowl gouges. I always mark the bevels with the magic marker. Also, I have a block screwed to the side of my sharpening stand so that I can quickly set the amount the gouges protrudes from the vari-grind. The only tool that I sharpen freehand is the skew.

[Joshua Dinerstein]

Not sure if I'm indifferent or lazy(or both) when it comes to this issue, but I fail to see the need for such precision in sharpening my tools. I think as long as I'm in the ballpark, I'll be fine. I may be wrong, but I doubt that many of us could tell the difference between two bevel angle that were 5 or 6 degrees apart. Even if I could, a slight adjustment in the presentation of the tool to the wood would likely negate any subtle difference.

Am I missing something?
Hi David,

My search isn't to get the perfect and exact 45 degree bevel on a tool, as opposed to a 44 or a 46 or even a 48. It is to stop trying to repair bevels after I massacre them. I get the angle what looks close and I start grinding and check again only to discover that I have been hitting only the heel, or only the cutting edge and I now have 2 pronounced bevels. This is more than just a frustration to me as when I get tired enough of the multiple facets or get them bad enough in just the right way that I have re-grind, i.e. truly reshape the tool. I am just needlessly burning thru the tool steel. Plus that much heavy grinding means lots of wheel dressing... and so on.

So I began my quest for a more accurate way to set the angles. I loved the Sorby ProEdge belt sander for this purpose. Their angle setter is awesome. But the unit starts at $500 and that was just too much for me. So based on some comments and pics from others I thought to myself: "Self, why don't you see if you can't enhance what you have first..." So here I am. Reed/Robo-Hippy had been talking about these types of wedges and I realized that I liked the idea of a platform that is fixed in angle and simple drop-on/in wedges that change the angles to what I need/want. Then each time you just put on the right block and hopefully, and this would be totally sweet, you just sharpen by removing a truly tiny amount of the steel rather than actually grinding, because the angle is right each time.

Edit: And by right, I really do just mean consistent rather than, again, being exactly 45 degrees.

Joshua

[David E Keller]

I think I understand your quest a bit better... Are you using the varigrind or something like it? I use mine just like Jimmy Clewes does in his videos. I use the pocket on the wolverine arm as the depth measurement for how much gouge protrudes from the jig(It's pretty close to the depth recommended for the block that they suggest you make). Then I do just like Joe... put the jig in the pocket and adjust the arm until the bevel rests completely on the wheel. Marking the surface to be ground is a great trick to confirming the position of the gouge relative to the wheel.

For scrapers, I set the platform about 15 to 20 degrees from the horizontal tilted in toward the wheel... I sharpen all my scrapers and hollowing tips upside down on the platform using that set angle.

My skews I sharpen free hand but fairly infrequently. I generally hone them over and over before I go back to the grinder.

[Dirk Hoogendoorn]

OK guys, if you set out to baffle me, you've done it. To me David has the idea on this one, just repeatable setting is what you are looking for I think, but then I'm only a high school drop out canuck retired guy with an interest in wood turning. Nothing too involved just a hobby,but you guys sure take this to the uttermost. Have fun with figures, Dirk H

[Joshua Dinerstein]

OK guys, if you set out to baffle me, you've done it. To me David has the idea on this one, just repeatable setting is what you are looking for I think, but then I'm only a high school drop out canuck retired guy with an interest in wood turning. Nothing too involved just a hobby,but you guys sure take this to the uttermost. Have fun with figures, Dirk H

It is a failing of mine. I like to know... Whether or not in the end I will use it "everyday" I want to know how to get it/how to do it. Perhaps it is my training or just my own personal craziness but it is "me". :)

Joshua

[Joshua Dinerstein]

So I have been looking at things. I think that starting on the angle rather than on the 90degree is going to be better. It looks easier to line things up. But it is kind of odd. It just seems like I ought to be able to figure this out. :)

I guess I will have to talk to the local math PhD. He is after all my father and he owes me. ;)

Joshua

[Reed Gray]

I was back in Missery for a vacation visiting family. I did explain a bit to Joshua about getting several angles by making wedges to go onto one of the Veritas Platform tool rests for the grinder. I have it set at whatever angle my scrapers were when I got them, and no, I never measured, but fairly blunt, like maybe 70 to 80 degrees. I then made wedges to go on the tool rest that would change the angle a predetermined amount, without having to adjust anything, and it is repeatable. I am making another tool rest that I will be able to adjust to preset positions from about 90 to 25 degrees. I should be able to make more money with it than I have with the lottery. Hopefully by Christmas time.

robo hippy