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Grinder angle jig.

john lucas

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I'm looking for a measuring device to set accurate angles on a grinder. Not talking about the Tormek that only works with their tools. I'm wanting something that works with platforms like the Oneway or other flat platforms. I've been searching this morning but apparently not putting in the right info.
 
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I have a simple plastic block that came with my Veritas tool rest tool rest. They don't seem to sell it separately (and the angle settings aren't really appropriate for turning tools anyway), but it wouldn't be hard to make one. The catch is that the effective sharpening angle depends on the tool thickness, thus the multiple lines on the gauge at each angled face. On the other hand, consistency is probably more important in most cases than absolute precision.

I don't use it much since I got a RoboRest. With any luck that will come back into production.
 
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If you are looking for a way to set the platform angle, then ditto on Stuart Batty's solution. If you can't find it for sale anymore it's not hard to make something similar (but not quite as good).

20211207_075633.jpg

If you're looking to set the Varigrind angle there was this thread:


I particularly liked post #11, but then I may be biased.
 
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john lucas

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I'm looking for something that's let's me set at least every 5 degrees. The jigs I make let me duplicate a known angle on my tools but if I want to start from scratch and pick 40 or 45 or some other angle. The Tormek jig is similar to what I want but only works with their tool rest.
 
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I have the Raptor gauges sold by Craft Supplies USA. While they are good and convenient, I find them expensive for what they are and I recommend NOT getting them. Like you, John, I would like more degree options available (e.g. 55*) but they are limited, as best I can can recall, 35*, 45*, 50* and 60*. Again, they're very convenient but they are niche for the 8" grinder wheel and the Oneway Wolverine system.

Since you maybe seem to want one thing to do multiple angles, this probably won't help. Nonetheless, this is what I made and use. That post shows the jig and how I make them for various angles.
Dave, brilliant use of geometry! Do you use the V-arm and Vari-grind for any of your gouge sharpening? If so, how do you set a precise angle for your setup like you have for the platform?
 
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Well John, you don't have one of my robo rest. Pull the pin and set the angle, no gauges. It will be back on the market, hopefully in the spring. Can't tell you who will be making them till they are out... There are bunches of ways to make angle setting jigs, some already listed.

robo hippy
 
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I have Robo's tool rest and couldn't be any happier with it. One of the best purchases for my shop. Easy, repeatable and like he said, just pull a pin and set the angle. I think many of my local turning club members that visited got home and ordered one. I'm glad to hear that they may be back on the market in the spring.

Damon
 

Dave Landers

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Dave, brilliant use of geometry! Do you use the V-arm and Vari-grind for any of your gouge sharpening? If so, how do you set a precise angle for your setup like you have for the platform?
I do use a varigrind for gouges. I don't set precise angles, but instead go the other way - I mess around with a gouge till I find the grind I want, then build a jig for setting that v-arm spacing. I make things that looks a lot like the Raptors. See here. They set the distance between the wheel and the v-arm pocket so it doesn't rely on any specific spacing below the wheel etc, and I can take it to someone else's shop and get the same setting. To set the arm on the varigrind, I just drill a hole thru the two parts - if it moves, I can reset it by just re-aligning the holes. There's more jigs and stuff from my shop on my website if you're interested.
 

john lucas

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Reed. I have the Robo rest. I'm playing around with other options. So glad your rest will be back on the market.
 
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The Tormek WM-200 AngleMaster will set platform angles from 10 to 75 degrees and will compensate for grinding wheel diameters between 6 and 10 inches. This gauge will work with non-Tormek equipment. WM-200 instructions The index surface of the gauge to the platform is not very wide so you have to be careful using it to get accurate results.
 
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How about a digital angle finder like this one. As long as you can set your platform 90° to the wheel, this should work (or 0° depending on your perspective)

Set platform to reference angle, zero out the gauge and move it to whatever angle you want. I use mine on the table saw all the time. Most have magnets on all sides.


Not necessarily recommending this one, just the first to come up in a search.

Just looked and the one I have is a Tilt Box II made by Beall.
 
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Ron Brown has one that might work:

The Tormek WM-200 angle setter will work with any 6” to 10” grind wheel and platform. I have used it with my bench grinder. The wheel guard might get in the way above the platform.

I also made my own from ~0.100 thick clear plastic sheet from lowes. Cut them into rectangles about 2-3” x about 6”. If I had a tool that had the correct mesured bevel angle I used it to set the platform. If I didnt I played with the platform angle and a tool until I got what I wanted. I then ground a good sized arc into the plastic using the wheel, keeping the plastic blank edge flat on the platform and the blank perpendicular. Then I used a burr in a drill to relieve all but 2 areas of the arc. Then etched the angle into the plastic. They are +\- a degree or 2 but work. Pic below. You may have to zoom in to see detail. Contrast isnt great.

1638939493968.jpeg
 

john lucas

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I'm quite happy with my Roborest. It is very repeatable and that's all it's really about. I'm just trying to understand how this angle is measured. If you look at the drawing I set my drawn tool rest at 40 degrees. Because the wheel slopes away from this the grind angle is not 40. If you look at the yellow angle gauge tha is set at 40 it only works if the measuring arm is perfectly vertical. Jut for interest I zeroed my Wixi gauge and then set the Roborest at 40. It measures 50. When I set the rest at the 50 degree setting it measures 40. When I grind a tool at the 40 degree setting and measure the grind on the tool it comes out 32 degrees. Which cuts incredibly clean by the way. So you can see my confusion. For years I just grind a tool like I want and then build a plywood jig that sits on the tool rest and touches the wheel at 2 points. This is extremely repeatable. I just want to be able to accurately answer people's questions about tool rests and gouge angles.
 

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@john lucas Well, you had the answer all along. Just measure a tool ground at various robo rest settings. You can find all the math explaining why The platform angle does not agree with the ground bevel angle, but I think you get the concept, which is all that’s needed. The measured angle is a function of wheel dia, platform angle, platform pivot point position vs wheel center, and tool thickness. If you want the robo rest #’s to agree better with the measured angle, the rest platform needs to drop down. If I remember correctly the instruction state to put the platform pivot at the same height as the wheel center, where is your’s? A thicker tool will always measure a degree or so less than a thin tool. The top plane “grows in length” due to wheel curvature.
 
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I'm just trying to understand how this angle is measured.
Now I apologize if I am misunderstanding your question, but here is my answer. Looking at your paper drawing you have a simple tool (e.g. a single bevel scraper) laying on a grinding platform. The tool's cutting surface has a top and bottom, with the top making an acute angle with the tool shaft and the bottom obtuse. We'd like to know the acute angle of the top surface of the tool, but this is difficult to measure. The bottom obtuse angle is easy to measure and it is the complementary angle. In other words if the acute angle is 40* then the bottom angle is 140*; 140* + 40* = 180*. So Batty's setup tool and my plywood tool and your yellow protractor should all read 140* to achieve a tool angle of 40*. Wixey will read 140*, as well provided you zero it on a vertical surface. If you zeroed it on a horizontal surface it will be 90* less. Note that 140 -90 = 50.

I think the other factor you are trying to take into consideration is that the grinding surface is round and the geometries at the top of the tool in your drawing are not exactly the same as at the bottom of the tool. If the platform is pointed directly at the center of the grinding wheel this error will be as small as possible, and hopefully something we can ignore. But if the grinding platform points substantially above or below the the grinding wheel center this effect may be more pronounced, I'm not sure without doing some drawing of my own.
 
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John, l think your concern is unnecessary. If you told a group of turners that you were using a 40* grind based off your Robo Rest setting, it would actually be 32*. Now 40 turners go home and attempt to duplicate your grind on their tool, they would collectively have 40 different grinds. Their tool rest heights, distance from the wheel, wheels diameters, and their setting gauges would all affect their results. Would that make a difference in their cut? If you were to use a bottom feeder that you ground at a 60* or 70* setting, your audience would have similar variability in their grinds, but they would have the same results that you were demonstrating(of course at the skill level of each individual). So if l were you, l would say about 40*.
 
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I think I understand what John wants, and I'd like to do that too. I had a Robo rest. It is repeatable, obviously, but it is far from accurate as John pointed out above. It also has way too much play in the thin aluminum fiitings and bent sliding pin for my use.
 
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I dunno maybe it is just me, but seems to me, too many folks are too nit-pickety about getting precise angles.. the wood don't care what your angle is, and if you get a usable bevel that works for you and sits comfortably, who cares whether it's 40 degrees or 32 degrees? I have not the slightest idea what my actual bevel angles are (my swept back irish/ellsworth grinds run somewhere around 50 or 55 degrees, my 40/40 done on vari-grind actually measures out to 40 degrees every which way I measure it - and I'm kinda liking that grind I just started trying out, my BoB 5/8 gouge I think is around 60 degrees, but I havent measured it yet - I ground that one just like doing an SRG) - but , so far my grinds seem to work for me (or I've just gotten used to and comfortable with my grinds) and as far as I can tell, as long as I keep them consistently sharp, the wood doesn't seem to care one way or another.
 

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the wood don't care what your angle is, and if you get a usable bevel that works for you and sits comfortably, who cares whether it's 40 degrees or 32 degrees?
For many applications precise angles are unimportant

As an example In finial work a 40 degree angle means an easier to control tool and sanding with 220 to start
While a 30 degree angle means having to be better at riding the bevel and sanding with 320 to start.

I want to be in a degree or so of my desired angle most of the time.
The beauty of the Ellsworth grind is the the different bevel angle you have in one tool
60 degree nose bevel holds the edge nicely for roughing
40-45 bevel angle just off the nose for finish push cuts
25-30 bevel angle on the wing for pull cuts.

The beauty of the 40/40 is you have a 40 degree bevel angle all around the cuttin edge.

In my experience 1-2-3 degrees is not important
5 degrees begins to matter
And 10 degrees is a big deal for all sorts of reasons.
 
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I think the other factor you are trying to take into consideration is that the grinding surface is round and the geometries at the top of the tool in your drawing are not exactly the same as at the bottom of the tool. If the platform is pointed directly at the center of the grinding wheel this error will be as small as possible, and hopefully something we can ignore. But if the grinding platform points substantially above or below the the grinding wheel center this effect may be more pronounced, I'm not sure without doing some drawing of my own.
Thinking this through again I realized I got something wrong. See the edit above.
 
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IMO when communicating to other turners, it is important to use the actual measured bevel value. There is substantial difference between 32 and 40 degrees in how the given tool works and feels, unless a scraper. All those turners should be replicating 32 and not 40, and should be measuring the bevel.
 
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After first making my robo rest, when trying the 40 degree setting, it just 'felt' too pointy/acute, so I sharpened at 45 degrees, and that felt perfect. Years later, I compared my 40/40 to another turner and they matched almost perfectly. No clue as to why the angles vary like that, after all, it is a protractor, and the design worked on paper...... I did discover that there is a slight difference in the bevel angle depending on how thick the tool is. A 1/4 inch gouge will have a slightly different bevel angle than a 5/8 or 3/4 gouge. That happens because the platform is set to zero at the center height of the axle on the grinder.

I do like the 40 degree setting for a small detail gouge, so it is actually about 35 degrees....

Can't wait to see what the new and improved version is going to look like. Still no firm dates on when. The original accomplished what I wanted with repeatable set angles.

Oh, John, your platform is very close to the wheel. There should be an 1/8 inch gap between the wheel and the cut out in the platform. Yours is one of the first run rests. The second run was all stainless steel.

robo hippy
 
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I have my Robo rest set up on a 6" grinder so the calibration was bound to be off. I checked the angles produced at each setting with a protractor aligned to the tool edge and made a chart next to the grinder. Seems like that is the simplest way to measure and communicate your grind angles to others.

I put a slight bend in the Robo rest pin to tighten it up a bit. It is stiff enough for me.
 
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Seems the further back a rest’s pivot point is located then the greater difference in tool height to center of the grinding wheel as the angle changes. Would it help any to locate the pivot point close to the front of the rest as possible (nearest the grinding wheel)? Maybe something for a CBN setup without any wheel guards to get in the way of the pivot parts.
 
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Both my grinder rest and the Batty one have a slight cut out in the plate so that the hinges line up with the face of the grinder wheel. This essentially makes the platform a protractor. Never liked the one from Oneway, and think mine went into the scrap pile. It pivots near the middle of the platform. Some have taken it and cut/ground out a space for the wheel. As you lowered the platform, you had to slide it back, as you raised it, you had to move it forward towards the wheel. I had a small one from Lee Valley, and it was adjustable for up and down. I made several wedges to put into the T slot on it, so I could change angles without having to move the main platform. While it worked, there was a hinge joint in the middle of the upright legs, and no matter how tight I made it, it would still change position if I 'bumped' it, which happened pretty much every time I used it.

robo hippy
 
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John, I have the number one angle gauge from SB and WWE, and I really like it. It is super easy to use when setting a platform angle relative to a CBN wheeel. They offer three different gauges, and between them I don't think there's an angle you can't set. I find it's very quick to use, and very easily repeatable.
 
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Stuart Batty had an issue with my grinder when I came out with it. He had a patent pending on his. I informed him, and his group that every thing I based my platform on was older than his dad, and mine for that matter. Every single angle platform on table saws and disc grinders are based on the same principal. With patents, if your lawyer can make it sound good enough, they can get a patent. For the patent to have any real teeth, you have to fight a battle in court, and win.

robo hippy
 
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