Underhand Sharpening

[RobinW]

A couple of problems I have experienced are grinding at large angles. I'm OK for chisels and blades at 25º and 30º. However for unusual items requiring a long protrusion or higher angles I'm not comfortable with as I have had a couple of snatches which don't do the wheel, the tool or my nerves any good. So preferred method for higher angles is to sharpen away from the edge.

However when using the USB in the horizontal position, the square edge jig SE-76 does not allow full width sweeping of a wide the tool across the wheel due to the offset of the SE-76 and also the position of the fixings for the USB. (See the photograph in Spokeshave Challenge post number 51 of 25 October as an example.)

So last night, with a bit of lateral thinking (also known as insomnia), I thought about 'Underhand Sharpening'. I don't recollect seeing this in the manual or any videos.

I have a Veritas scraper plane to sharpen. It's 73mm wide, and the parallel sides are limited ie getting it set up for 50 mm protrusion in the SE-76 is a pain. It also requires its edge to be sharpened at 45º. I have previously tried making a jig for this with some limited success.

So last night's spark was to mount the blade facing out the back of the SE-76, still using the reference edge of the SE-76, and with the USB in the vertical position, have the blade pointing downwards so that you are sharpening away from the edge. Set up with the angle master as usual.

I have just tried it and am very pleased with my Underhand Sharpening.

A couple of things to note. I don't usually use the end stop knob on the USB as I'm familiar with the tool placement on the wheel. As this was a new position I did need the end stop knob.

When moving the blade towards the inside of the Tormek, the blade fouled on the fixing knob which locks the USB. So I swopped the knobs round ie large knob as the end stop, and small knob (now clear of the blade) to lock the USB.

Figs 1 and 2 show this in action.

[Waterstone]

Now this is a good idea Robin! The advantage of the veritcally fixed USB is going together with a safe process. A combination of the best of both worlds. I will have to think about this solution. Maybe it can be adapted for the special jig I'm at it to make.

Klaus

[Ken S]

Bravo, Robin! You deserve one of the coveted Popular Mechanics Home Workshop awards.

Keep up the good work.

Ken

[Jan]

RobinW, congrats, very inventive thinking, appreciated. 

I wondering what happens if you reduce the scraper protrusion to some 30 mm. Will you be able to use also the horizontal sleeves for grinding away from the edge? I hope you will. 

Jan

[RobinW]

Hello Jan

In the underhand sharpening photographs the blade is only protruding 30mm. I normally use 50 for chisels etc (It's as good a number as any.)

I have tried using the SVD 110 and the USB in the horizontal mode, I never felt that I was in control of the blade, it would try and lift off the plate and I didn't get any satisfactory results. With today's method it's all under control and easy to operate.

(I just wish I could get the scraper plane set up as easily as sharpening the blade! It is the most frustrating tool I have, and I wouldn't trust it if I was doing an important job. I get much better results from my No3 plane. I have read the instructions, watched numerous videos, tried different methods of creating the hook etc and if it hadn't cost a load of money it would have been in the bin long before now. I know, a bad workman......)

[Jan]

Robin, thanks for your explanations. 

I think, that when you mount the blade facing out the back of the SE-76 with the protrusion 30 mm, you will be able to use also the horizontal sleeves for standard grinding away from the edge. Or am I wrong? 

The angle setting will remain the same as for your underhand sharpening. 

Jan

[RobinW]

Hi Jan

I've been round this loop a long time ago, and I knew it wasn't satisfactory, so had to do it again to get the information.

Attached pictures for same scraper blade, set for 45 degree.

Figs A and B show SE-76 in 'normal' mode, with full left and right outcome.

Figs C and D show SE-76 inverted with blade coming out the back, with full left and  right outcome.

The very limited movement is not as good as Underhand Sharpening.

[Jan]

Robin, thank you very much for your explanations accompanied with pictures. 

It is good to know that your Underhand Sharpening using vertical sleeves is more comfortable than the use of horizontal sleeves.

Jan