Bevel Angles- Raffan (Henry Taylor) Radius Skew Chisels

[Jan]

It's a good thing that I am the moderator instead of the navigator.

Good comment, Ken. At equator one degree corresponds to 60 nautical miles. 

I had not realized the difference is seven degrees. Would either method work as long as we compensated for the difference?

A good rule of thumb would be to measure the edge angle of the skew chisel always perpendicularly to the edge. 

Jan

[RichColvin]

When I measured it using the WM-200, it showed as 50^o ! 

I checked a reference book I have from Leonard Lee titled, The Complete Guide to Sharpening (I bought this before the Tormek).  He says that skews should have an included angle of 12.5^o to 15^o.

From my own experience though, when I had a smaller angle, it was no where near as good an experience on the lathe.  Too hard.  This setup works wonderfully for me.

[RichColvin]

Please note :  I just realized that I have been setting the projection wrongly on the SVS-50.  I was measuring to the housing, not the tool seat.  So, that is why the included angle I reported may be different that you'd thought it should be.

[Jan]

Thank you Rich for your edge angle measurements and your caveat. 

The predefined TTS-100 settings do not allow to set 50^o edge angle for a chisel with skew angle 20^o. When you set JS=20^o, Protrusion=55 mm you will get 45^o edge angle for the hole B. To get 50^o edge angle, you have to make the protrusion by several mm smaller than 55 mm.

Please let me know if it works.

Jan

[RichColvin]

Jan,

I took some time at lunch today to re-grind my skew with the proper use of the SVS-50 Multi Jig :

.

The grind setting I used is

• projection = 55mm
• skew angle = 20^o
• Hole = B

(By the way, the initial shaping using the BGM-100 made this a LOT easier !)

Once finished, I measured the angle on the WM-200 AngleMaster, and found the angle to be 40^o.



As I was grinding, I noticed that the TT-100 also has grind angle measures, so I measured it on the TTS-100 Turning Tool Setter, and found there to be a tight fit when the angle is measured to be 45^o.



Given the differences seen, I measured this using a carpenter's angle finder tool and a protractor.  This showed the angle to be 41^o.

 

So, I would tend to believe the angle measures on the WM-200, but if the angle is critical, I recommend you use a protractor.  Hope that helps.

[Jan]

Rich, thank you very much for sharing your nicely documented results. 

Measuring an edge angle using the notches has limited accuracy, your results show that the relative error is some 10%. It is fully acceptable for such an indicative measurement. As already mentioned it is important to orient the protractor perpendicularly to the edge (not parallel with the side of the blade). It is easy to know that the protractor is properly oriented, because than the measured angle is the largest.

In the skew case I have shown in this topic the real edge angle was 60^o, while measured parallel with the side of the blade it was only some 53^o. The difference was larger because the skew angle was 30^o. 

Jan