Plane Blade Jig

[Kieran Kammerer]

I have the Somax plane blade/chisel blade holder. On the side, it instructs you to have the plane blade extend 50mm to hone a thirty degree bevel and 38mm for a 25 degree bevel. I am sure one of you mathematicians can tell me how may mms the blade needs to extend for a thirty five degree bevel. For that matter, what formula do you use to figure out the blade's extension?

The second question I have regards the cental screw that one turns to pull the sides of the jig together and clamp the blade. As I use it, the screw tends to lossen and the blade susequently shifts from its original mms of protrusion. Does anyone have suggestions as to what (if anything) I might put on the threads to make them grip slightly better.

Thanks in advance for any help or suggestions.

Kieran

[Richard Gillespie]

I am not at all familiar with the jig you have but I wonder if a lock washer might help.

Based on the following replies I have revised this post to remove the egg from my face. As I said with my original post I'm no math expert.

[Todd Burch]

A quick drawing in Sketchup shows the lengths of the hypotenuse that you are looking for. I don't have millimeters, so I used inches. I set the right triangle up so that the hypo. was 50" long and the angle was 25°. Then, I drew two new hypos. to indicate 30° and 35°. Finally, I put a dimension on each line. Just use mm instead of inches.

This proves that a measurement of 38mm for a 35° angle, in your documentation, is an estimate! (but close enough, I'm sure).

Todd

[Todd Burch]

Well, I screwed the previous drawing up. Here is a redo- I reread your dimensions and the length/angle pairs are opposite what I was envisioning in my head. So, here is the corrected drawing. Looks like you need to extend your blade almost 74mm. Todd.

[Todd Burch]

By the way - should I have used my slide rule to answer this question in this forum? LOL!!!

[Kieran Kammerer]

Well, I screwed the previous drawing up. Here is a redo- I reread your dimensions and the length/angle pairs are opposite what I was envisioning in my head. So, here is the corrected drawing. Looks like you need to extend your blade almost 74mm. Todd.


Todd,

Thanks for the mathematical input. It has ben a long time since I have had to work on those ( except helping my kids wth homework). I will try the 74 mm and see what happens.


Kieran

[Michael Campbell]

I have the Somax plane blade/chisel blade holder. On the side, it instructs you to have the plane blade extend 50mm to hone a thirty degree bevel and 38mm for a 25 degree bevel. I am sure one of you mathematicians can tell me how may mms the blade needs to extend for a thirty five degree bevel. For that matter, what formula do you use to figure out the blade's extension?

I don't understand how this jig works or what it's calling a "projection"; my mind is working like Todd's initial drawing (in which Kieran's numbers would have to be reversed for it to work right, and even then the 50mm would have to be closer to 45mm). In my mind (and my jig), longer blade projections give you smaller bevels.

Can someone show me how this jig is set up? Google didn't help much.

[Kieran Kammerer]

I don't understand how this jig works or what it's calling a "projection"; my mind is working like Todd's initial drawing (in which Kieran's numbers would have to be reversed for it to work right, and even then the 50mm would have to be closer to 45mm). In my mind (and my jig), longer blade projections give you smaller bevels.

Can someone show me how this jig is set up? Google didn't help much.

Now that I have completey confused everyone, Michael is right. The 38 mm projection leads to a bevel of 30 degrees and the longer 50mm blade projection results in a shallower, 25 degree bevel. The jig itself is a pretty standard design. It was only hard for you to conceptualize how it worked base on my initial screw-up in the numbers. Thanks for the help and input.

[Michael Campbell]

Now that I have completey confused everyone, Michael is right. The 38 mm projection leads to a bevel of 30 degrees and the longer 50mm blade projection results in a shallower, 25 degree bevel. The jig itself is a pretty standard design. It was only hard for you to conceptualize how it worked base on my initial screw-up in the numbers. Thanks for the help and input.

Ok, now we're cooking with gas. If the 38mm/30* setting is perfectly correct, a 35* projection would be 27mm.

If the 50mm/25* setting is perfectly correct, a 35* projection would be 30mm.

As for it loosening up, I've never experienced that, but after I get mine where I want it, I crank it down with a screwdriver; are you doing that?

[Eric Sanford]

I do as Michael does, get it set and crank it pretty good with a screwdriver...occasionally I will test it and re-tighten if needed.

FWIW, a big help is to create a set of guides for setting your angles. Just a few pieces of scrap ripped to the appropriate mm length, put the blade in the jig, align the jig against the guide and set the cutting edge even with the edge of the guide. Tighten and you're ready to go. This should give you consistent settings.

Eric