WM-200 Angle Master Accuracy

[GIPPER]

How accurate is the angle measurements for this device?  If I place it horizontally on a flat surface, I get 17.5 degrees.  How does this compare with others?

As an example, using an old abused 3/4" flat square wood chisel, the Tormek settings didn't come close to the existing bevel angle.  With the "marker method", and using the WM-200, it told me the existing angle was slightly less than 24.0 degrees.  Maybe by 0.2mm.  I decided to make the angle exactly 24.0 degrees and set this with the micrometer and the WM-200, and ground away I went.  So, the question is, can I rely on the accuracy of the WM-200 and believe that I sharpened this chisel with exactly a 24.0 degree bevel angle?  Gipper

[Jeff Farris]

Not to be flip, but what exactly would be the point of sharpening a chisel to exactly 24 degrees (or any other angle for that matter)?

The accuracy of the WM-200 is based on accurately measuring the diameter of the wheel, accurately setting the diameter compensating side to that measurement, and insuring that the gauge is resting on the grindstone surface at both points while setting the tool angle. If any material length is removed from the tool, the resulting grind will be at a shorter bevel angle than when it was set.

The geometry of the WM-200 is spot on. If you use it as designed, and are measuring a tool that needs minimal steel removal, it will be accurate to within a fraction of a degree.

All that said, any edge tool that is within 2 or 3 degrees of your target angle is going to deliver performance exactly equal to one that is precisely ground...that is to say, after 30 years of woodworking, I could not tell you the difference between cutting with a chisel that was anywhere between 23 and 27 degrees.

[GIPPER]

Thanks Jeff.

Perhaps my goal for accuracy is higher than need be.  I understand that setting the bevel angle to what it is, removes less steel than to create a new angle.  Just recently, however, with another flat, square wood chisel, using the WM200, one side of the chisel measured about 45 degrees while the other side measured about 30 degrees.  I decided I would remove less steel if I made the bevel angle exactly 30 degrees instead of 45 degrees, and set up for that.  That caused me to wonder about the accuracy of the WM200.  I had also been thinking that setting precise bevel angles would make it easier to set up again in the future.

Its still a fascinating learning experience for me, and I thank you and all the folks on this board for sharing your wisdom with me.  Gipper

[Ken S]

When I first bought my Tormek, I had trouble using the WM200.  I almost made a new pointer with a longer bearing surface. (I still may someday.) Before I had a chance to do that, I happened to set up my Tormek outside in very good light.  I found the WM200 much easier to use in very good light.  (The same might be said for most precision tools, especially with older eyes.)

From your description, it sounds like you are having more problems than the WM200.  Is the back of your chisel properly flattened and polished?  From your description "and old abused chisel" I am skeptical.  I have flattened and polished the backs of numerous chisels.  It is a lot of work, especially with oil stones.  Even with faster cutting water stones or sandpaper, it is laborious enough to make one reluctant to abuse the tool.

I would suggest you make certain the back of your chisel is dead flat and polished like a mirror.  The sides should be parallel, as well. The chisel should be in fine condition, except for sharpness. Only after that would I even think about working on the bevel. 

Make sure your wheel is well dressed and square with the universal support bar.  Likewise, make certain you are working in very good light.

At this point, I believe you will find your WM200 is working much better.  (Make sure it is not loose.)

Please post your results, good or bad.  That's the way we all benefit from this forum.

Fortune favors the brave.

Ken

[rsetina]

How accurate is the angle measurements for this device?  If I place it horizontally on a flat surface, I get 17.5 degrees.  How does this compare with others?

I've found it to be very accurate. I sharpened a set of 5 chisels last week and the WM-200 settings were right on. The angle was 30 degrees and each chisel was sharp. Are you sure you had the settings correct on the 200? It should have been spot on.

[GIPPER]

rsetina

Until somebody tells me what reading the 200 gives laying on a flat surface and set for a 250mm stone, I won't know how to tell what bevel angle I actually have if the 200 reads 30 degrees.  As I said before, on a flat surface, my 200 gives me an angle of 17.5 degrees.  Gipper

[GIPPER]

Ken S
I have found one thing out so far, that bothers me.  Using the WM200 to measure a resultant angle while adjusting the Universal Support with the micrometer, I found that by starting high and adjusting down will give me a big error because the support "binds" in its sleeve.  To reduce this error, I found that by starting low and adjusting up with the micrometer, usually gives me the correct angle by the time I lock the support in place.  You can start 'high' and go low but you have to bang on the support with your fist to get it to settle down to the micro surface.

Hope this isn't too confusing.  I'm still trying to confirm or prove, that if the WM200 points to the 30 degree mark, the tool bevel angle will actually be 30 degrees, or any other angle chosen.  So, a good starting point is to check your WM200 flat on a surface and read the resultant angle on the dial.  If its like mine, that angle would be 17.5 degrees.  Gipper

[Jeff Farris]

rsetina

Until somebody tells me what reading the 200 gives laying on a flat surface and set for a 250mm stone, I won't know how to tell what bevel angle I actually have if the 200 reads 30 degrees.  As I said before, on a flat surface, my 200 gives me an angle of 17.5 degrees.  Gipper

The WM-200 will not give an accurate measurement on a flat surface. It is not intended to work on a flat surface. The entire design of the gauge is to measure the angle relative to the circumference of the grindstone.

[ionut]

Hi Gipper,

The angle master is very precise, in my case when I needed to use it I didn't see any difference between the sharpened bevel and the protractor set for the same angle. As Jeff has already said it regardless what setting for the diameter of the wheel you have on the angle master when used on a flat surface you will not get the same angle you can read on the angle master. It has not been designed for flat surfaces. If that would be the case you would have a flat reference surface on the angle master, but there is none. If you want to verify its accuracy I suggest you to take a chisel that you trust of being flat, measure the diameter of the stone with a ruler, the body grid for this purpose may add an error depending on your reading position, set the angle master as the manual explains and grind the chisel. At the end verify it with a protractor, if it is out the angle master you have may be defective or not in within the parameters. I got mine set it for 250 wheel diameter and set it on a flat surface and measured the angle and I got approximately the same reading as you did.

Thanks,
Ionut

[ionut]

At the point where you actually measure the angle (the gage has to be flat on the back of the tool) the grinding angle happens on a totally different tangent line that the one you are trying to set the angle master for when you set in on a flate surface (the line that unified the diameter wheel gage with the angle setting one). That is the reason why using a flat surface will add an offset to your angle measurement.

Thanks,
Ionut

[GIPPER]

Thanks Jeff
I believe that the 17.5 degree angle read on the scale of the WM200 when placed on a flat surface, is correct and accurate.  I have also determined that if the 200 scale could read Zero degrees, you would find that placing the instrument on the grindstone set at Zero (not possible) would contact the wheel perfectly flat.  So what's the big deal?  None.  I just wanted to verify how reliable the WM200 was in measuring bevel angles.

With some math and some graphics, I think I can safely say that this is a remarkable "instrument" in its design.  Probably something that should be treated very delicately when in use or in storage.  But I'm going to use the 17.5 degree mark on a flat surface as a means of checking the calibration of the instrument.  If its different, you can bet that your bevel angles will not be what you think they are.  Gipper

[GIPPER]

Thanks Ionut.
Certainly the angle changes with diminishing stone diameter.  If you use the "flat surface" test, that angle would change from 17.5 degrees to approximately 20.0 degrees with a 250mm diameter stone to a 200mm stone respectively.  That's only a 2.5 degree change but if the proper adjustments weren't made, it would produce a bevel angle far less than what you might want.  The angles I'm talking about are "built-in" angles accounting for the wheel circumference plus a desired bevel angle on a tool.  The constant angle is what I call the "flat surface angle".  Gipper

[Ken S]

Gipper,

If using the WM200 seems iffy to you, here's an alternate method:

Perhaps like you, I am somewhat of a tinkerer.  I use the TTS100 turning tool gage.  Its two point contact (which I believe is patented) compensates for wear of the wheel. 

Set the universal support bar to one of the two settings.  This becomes your fixed distance.

Place your chisel in the SE76 jig and use the WM200 or black marker technique to get the angle you wish.  Note the protrusion distance from the front of the SE76.  Make up a "gage block" for this protrusion distance.  I use a piece of cardboard with a pencil line.  Note the angle on the gage block.

The next time you set up your Tormek, set the universal support bar using the TTS100 and set the protrusion distance of your next chisel using your cardboard gage block.  Your bevel angle should be consistent.

If you wish, you can make up gage blocks for different angles, such as paring chisels instead of struck chisels.

The handbook shows a very similar method using wooden spacer blocks. 

I like methods which are accurate, but do not rely on ongoing measurements.

Ken

[Herman Trivilino]

If I place it horizontally on a flat surface, I get 17.5 degrees.  How does this compare with others?

I do get about 17 or 18 degrees.  But this is true only when the diameter is set to 250 mm.

So, this verifies that your WM-200 and my WM-200 are the same.

Now, if I keep the WM-200 settings the same, and set it on the outside of a 250 mm diameter wheel, it will make a 17.5 degree angle with the surface of the wheel.  That is what it's designed to do.

[Herman Trivilino]

Just recently, however, with another flat, square wood chisel, using the WM200, one side of the chisel measured about 45 degrees while the other side measured about 30 degrees. 

Huhh?  This makes no sense.  If the front of the chisel makes a 45 degree angle with the back of the chisel, then the back of the chisel MUST make a 45 degree angle with the front of the chisel.

To make this happen on a typical wood chisel, you set the WM-200 to 45 degrees.

If instead you want the angle to be 30 degrees, you set the WM-200 to 30 degrees.