Spokeshave Challenge

[Waterstone]

Hi Robin,

the outside surface of the blade is flat. Oddly the ground bevel is flat from side to side as well.
The inside edge was honed with grit 1000 after the Tormek grinding. I will try to get that done your way.
The minimal protrusion of the jig inside the SE-76 is exactly 50 mm. It can be altered up to 70 or 75 mm.



The bevelling of the plates has to be done indeed. The grinding action can't be seen the way you want it to have. Good idea!

Maybe the jig or my technique (probably the latter ) can be optimized but all in all I'm pretty pleased already. Never had this spokeshave that sharp before. That counts.

Klaus

[RobinW]

Hi Klaus

I'm back from the cold outside!

My jig has a protrusion of 80mm as shown below. Nothing scientific, it was just used for something else.

With the jig mounted out the back of the SE-76, and with the USB in the vertical position, the USB can be raised high enough so that the 'blade' can be swung right through just touching the wheel, so tangential position can be obtained. See below. However, at such extreme heights, the frame of the SE-76 can interfere with the threaded rod of the USB as the SE-76 is moved inboards.

With the jig mounted out the back of the SE-76, and with the USB in the horizontal position, the USB can again be pulled out enough for tangential position. See below.

I haven't tried it, but I would think your reduced protrusion would be preferable as at big USB heights it might be prone to vibration.

You're well on the way to even better results.

Robin

[Waterstone]

Yes Robin, it's lousy cold here as well!

Thanks for the latest pics. I think that I have to give the underhang technique a serious try. If that works, the sharpening process will tend to get fool proof. Have to wait until tomorrow however since I've epoxied the screw heads into the bottom plate. This will need 24 hours to dry.

Klaus

[Waterstone]

I've made a new jig that was built in a way to allow the 'Underhang Sharpening' by using the SE-76. The blade is sitting somewhat tilted inside the jig. So the blade is perpendicular while sharpening, the jig itself isn't. When it was finished I was delighted to state that it works on the horizontal USB very well. That's how it looks:





It's a very safe and controlled sharpening process just the way, that all of us are used to get from the Tormek. The ground bevel:





I'd say the result is close to perfect.

After a quick freehand honing the cutting edge looks like this:



With some anticipation the blade was inserted into the spokeshave. First cut and ...Wow it works very well! Second cut ... what's going on? Only a very narrow shaving. Third cut ... it doesn't work at all! What was happening? The middle part of the edge was folded 



Obviously the edge is way to weak. The inside surface of the cutter needs to get a bevel to strenghten the edge. Will have to think about a fastener that allows the controlled bevelling of the inside surface. Doing this freehanded is a PITA.

Will keep you updated.

Klaus

[RobinW]

Good morning Klaus

I think your edge angle is too shallow. It is difficult to judge from the photographs, but looking at the angle where the blade is now meeting the wheel in your photograph, the ground face looks long, so the edge will be weak.

If you think of a standard plane, with the bevel on the underside, the blade is meeting the wood at 45º. The blade itself may be sharpened at 25º with secondary bevel of 30º, but the upper side of the blade is taking the same angle of 45º from the plane mounting.

I need to think whether you apply an inside bevel (difficult to get accurate on this blade) or rotate the blade in your jig to get a larger edge angle nearer 45º. Have you tried measuring the bevel angle with the Tormek angle master?

MkII jig looking very good and the fact that you under control and feeling comfortable would imply a set up issue, not a jig issue.

Robin

[RobinW]

Klaus - I have just used some of the latest whizzo technology to measure your edge angle.

Took a screen image of your photo, printed, used a pen and protractor and arrived at the very accurate determination of 15º, as shown below!

As lawyers put in documents, E &OE (errors and omissions excepted). Pretty rough and ready method, so accuracy definitely not to be relied on!

Robin

[Waterstone]

Hi Robin,

this whizzo thing is cool!  15° is exactly what the angle finder on the WM-200 is telling as well. Pretty clear that this angle never will work. The problem is, that the face can't be ground smaller. Currently it has 6 mm. Less won't work since the back of the face then would be deeper than the cutting edge once the blade is inserted. Here a pic that shall show it though the quality isn't the best.



So the grinding better won't be done up to the very edge. Leaving 1/10 mm probably will be better. The cutting angle needs to be increased anyway. I guess that this has to be done by bevelling the inside surface.

Many thanks for your ongoing help!

Klaus

[RobinW]

Hi Klaus

Here's four sketches.

a) First shows my understanding of the existing bevel which is too narrow at the edge.

b) Second shows application of a second steeper bevel from the outside to get say 30º at the edge. (This assumes that a lot of the blade is not ground away to get a single say 30º edge.) If the blade is still mounted in the tool the same as that as shown in (a) then I agree that the cutting edge is prevented from operation due to the shoulder where the bevels meet. However if the blade is rotated backwards in the tool to a new axis, then it should work. The amount of metal resting on the wood is small.

c) Third is the case if an inside bevel is applied. Again it causes the axis of the blade to move backwards ie it needs re-positioning. There may be more metal of the blade resting on the wood than (b)

d) To get an inside bevel, assuming you have a waterstone or diamond plate, then use either MkI or MkII jig to hold the blade, tilting the jig down to the angle required that it results in a 30º edge angle. Then push/pull the jig along the length of the waterstone i.e. sharpen along the length of blade not transverse as previously ground. (Not sure of angle required. need to think more)

Plan B
Turn the existing blade round and sharpen the back edge as the cutting edge i.e. start afresh and ignore the edge that you have already worked on.

Plane C Have you got any spare blades?

Robin

[Waterstone]

Robin, you actually are killing me! The speed you throw out new ideas and these brilliant matching sketches is just stunning. Will have to test all of your proposals. Lots of thank yous another time.
I have two of these blades. One is pretty short already, perhaps 5 mm rest life. The other one is rather good. Ok, it has been pretty long before I began the Tormek grinding attempts  But it still has a lot of rest life.

Klaus

[RobinW]

I would use the well worn one first to get technique correct. Then you have the better one with plenty life in it.

The weather is cold so I'm not particularly motivated to do other things. Just had an hour's walk through the estate nearby and it was fresh but enjoyable.

[Jan]

Please can you explain what is the major usage of the cigar shave? I can imagine that it is perfect for refining the inner side of some oval profile. But there are sure other situations where it performs better than other tools. 

Jan

[Waterstone]

Hello Jan,

once the blade is sharp and the set up is right, the tool is able to do much more than to shape concaves. It does convex shapes as well very easily. Jimi Hendricks shows it at WK Fine Tools

http://contrib2.wkfinetools.com/hendricksJ/cigarShave/cigarShave-01.asp

For all kinds of oddly shaped workpieces, the cigar shave is a go-to-tool.
Jimi shows the handsharpening of the cutter. I tried it and it works so la la to me. Never got it razor sharp this way. Now I'm looking forward to getting this tool as sharp as it deserves it.

Klaus

[RobinW]

Klaus

The link to Jimi Hendricks was pretty informative for the following:-

I have taken a screen shot of one of his photographs which is the most telling point. Compared to a plane blade, the flattened outside surface of the curved blade is the 'same' as the flat side of a plane blade. The inside of the curved blade is like the bevelled face of the plane.

Early on he refers to the very small inside bevel, and says that if it hasn't been touched then leave it.  "If not... then you have to make a new inside bevel, but this is not something you should do unless you absolutely have to."

What does one do if it has no bevel or needs cleaned up? He doesn't give any advice about re-doing the inside bevel! That's where we find out for ourselves!

I note the width of the outside flat surface, it looks like 10mm just guessing from the photographs, which is bigger than your 6mm width. I wouldn't change yours.

So I would conclude that you should put a small bevel on the inside surface and get a cutting edge angle of say 30º. (See previous sketch for holding blade). As the tools can be rolled when shaving wood, the a higher angle between blade and wood can result.

On a separate point, I looked at a couple of my metal bodied spokeshaves (bevelled 30º on underside like a plane), and with the blades retracted and the base of the tool resting on a surface, the blades are sitting at a nominal 45º to the surface.

Robin

[Jan]

Hello Jan,

once the blade is sharp and the set up is right, the tool is able to do much more than to shape concaves. It does convex shapes as well very easily. Jimi Hendricks shows it at WK Fine Tools

http://contrib2.wkfinetools.com/hendricksJ/cigarShave/cigarShave-01.asp

For all kinds of oddly shaped workpieces, the cigar shave is a go-to-tool.
Jimi shows the handsharpening of the cutter. I tried it and it works so la la to me. Never got it razor sharp this way. Now I'm looking forward to getting this tool as sharp as it deserves it.

Klaus

Klaus, than you for the explanation and the interesting link. 

Jan

[Ken S]

Robin, you actually are killing me! The speed you throw out new ideas and these brilliant matching sketches is just stunning. Will have to test all of your proposals. Lots of thank yous another time.
I have two of these blades. One is pretty short already, perhaps 5 mm rest life. The other one is rather good. Ok, it has been pretty long before I began the Tormek grinding attempts  But it still has a lot of rest life.

Klaus

Klaus,

Twenty years ago I became very frustrated cutting photographic mats. I had purchased a top of the line professional mat cutter, a C&H, which cost $600 US, far more than a Tormek. My results were mediocre.

After six months of extreme frustration things started to fall in place. To my surprise and joy, solutions came to me rapid fire. I had reached a level of understanding I had never experienced before, and rarely since.

I think Robin and some of the other forum members have reached that same delightful level of learning. I first started noticing it around the time that Herman made his small blade jig. Since then numerous innovative ideas have appeared on the forum. I have faith that this exciting trend will continue.

Ken