Precise angle cutting

Boatman

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The first thing I did was make a convert-a-dog 20 mm for the table and 7/8 for the fence pivot.



Then I drilled a 7/8 inch hole in a piece of plywood to serve as a pivoting fence. Then with a bevel gauge that picks up an angle directly from the work, I can position the fence from 2 different directions as needed.


(Qwas dogs are used to reference an edge when needed)


If I need a precise angle, I can use a 10 inch sine bar that I made several years ago, based on an article in Fine Woodworking.



If you need any for info on anything I can add details
 
The sine bar looks useful. I have a fine woodworking online subscription but I could not locate the article you refered to, do you have any more info on this?

Thanks,

RMW
 
I searched on line and I think it is in issue #199, but I could not pull up the article. I will look at the shop to see if my hard copy is there. I can also post or email how I assembled mine, it is not very difficult.
 
Thanks for looking. I goggled it and it looks like the only parameters are for the 2 round bars to be at a precise (and the recommend even #) measurement and for the edge to be parallel with the centers of the blocks. Does the means whereby you mount them also allow for some final adjustment?

Appreciate the input.

RMW
 
That's a very useful tip for cutting angles on an MFT table.
In theory using a sine bar would provide dead-on accuracy.  Bridge City Tools is coming out with what should be a very handy tool for setting angles within plus or minus 30 arc seconds which is plenty of accuracy for woodworking (actually also precision machining in most cases).

[attachthumb=#]
 
Yes Ron that would work but it is currently unavailable and I spent all my money on Festool.

Rmw  there is no adjustment once everything is glued together. I basically built mine as per the article but I made a spacer bar    to index the two holes. Sorry I have no photo sequence now but I will describe it and do photos tomorrow. This whole thing works on solving a triangle math problem. The given info is one 90 deg angle a fixed hypotenuse an you supply the angle you are looking for. The sine of the angle times the length of the hypotenuse equals the height of the 90 deg leg, or the gage block. A 10 inch sine bar work well for woodworking because it is big enough to actually register a fence. And the math is easy you just move the decimal on the answer for sine. It does not matter what size disc is used but they have to be the same I used 3/4 inch. Strive for a 10 inch spacing. I made a 10 inch spacer so I could drill one hole with a fence and stop then insert the spacer and drill the second hole. When the discs are in the holes measure them and see how you did. I was 5 thou. off but felt that was acceptable ( the math showed the gage blocks when rounded to thousandths would be the same). But if you ended up with 9 and 57/64 who cares that just becomes your multiplier instead of moving the dec. If I were to build another I would first clamp the discs to a piece of wood with small clamps and adjust them so they were a perfect 10 inches apart on center. Then I would drill the holes as described above then cut the shape so you can slide it past the clamps over the discs. Hopefully it will slide right on if not, gently sand the holes till it does. Once it fits mix some epoxy and glue them in place. The piece of wood the discs are clamped to should be protected from being glued with everything else. When the epoxy has cured run the discs against the fence of a router table or table saw to true up the other side parallel with the discs. Except for some final trimming to have the needed clearance at the discs you are god to go. I use the calipers for a quick set up or to measure and cut a permanent gage block, but that can be another post. Let me know if this doesn't make sense.  
 
Thanks Boatman, it makes perfect sense. I have to add to my list of projects aimed at making other projects easier.
 
Still working on these angle cutting ideas, the latest direction is a quadrant as shown in the pictures. With direct reading to a quarter of a degree. The photos are staged Because I'm waiting for some offset knife hinges to use as the pivot.

(click for bigger)




Any comments or suggestions would be appreciated.  [smile]
 
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