Setting precision angles #1: The bevel board

 Blog entry by Boatman53 posted 12-08-2012 10:17 PM 11056 reads 20 times favorited 17 comments
 no previous part Part 1 of Setting precision angles series Part 2: The Sine Bar »

I often read posts from people having trouble setting angles on machines or wherever. So I thought I’d share what I’ve learned over the last thirty years, and I realized I’ve been using, thinking and in some cases obsessing about angles for a long time. My first career was a land surveyor, and obviously that was nothing if not angles and distances, down to degrees, minutes and seconds.
But I moved on from surveying to wooden boat building in 1982 and have been doing that ever since. Boats are an amazing combination of angles and bevels constantly changing from one end to the next. Of course a sliding bevel gauge is a primary tool but if you don’t have a way to set a particular angle all you can do is compare and transfer. So the first thing I made was a bevel board. It’s drawn on about a 32” square of plywood. It’s not difficult to make but just a bit tedious. It doesn’t wear out so if you make one take your time and accuracy is paramount. As a boatbuilder I would use it to make a bevel stick to quickly find bevels on a lofting so frame bevels could be cut on the bench instead of trial and error once the frames are set up as I have often seen in some shops (professional shops in more than one case). Here is how I made mine. It’s very useful even if you don’t build boats.

Start with a square of plywood 32”x32” not much smaller than that. Leave a margin all around and draw a square 30”x30” . Check diagonals and the lengths of the four lines. When you are sure it is square, starting from the lower left hand corner I made a grid of 6” squares I think but they could be any spacing you want accuracy is more important than whether you use 4”, 6” or just one at 15”. Next you will need to draw an arc with a radius of 28 5/8” or 28.625” if you have decimal measuring tools.

Draw that radius from horizontal to vertical. Every 1/2” measured along that radius is equal to 1 degree. What I did next was layout 10 degrees, measure that distance with dividers and then walk the dividers to the vertical line and see how close I came. Once I had the radius divided into 9 equal spaces they were divided in half and then all the 1 degree marks are added. And of course every 1/8” along the arc is 1/4 of a degree. I never felt it was necessary it add that till I needed it.

I often thought that a vertical and horizontal dado for a miter gauge bar would be handy for setting the miter gauge,but I never did it.
Hopefully this information is useful to someone and feel free to ask questions if you have them. This is just the first installment on the different ways I handle angles and bevels.

-- Jim, Mid coast, Maine Ancorayachtservice.com home of the chain leg vise

17 comments so far

 DIYaholic19860 posts in 3182 days #1 posted 12-08-2012 10:43 PM Thanks for taking the time to share this! I can see this being very useful. I was born & raised on Long Island, Bay Shore to be precise. Family still live there, they’re in Brookhaven Hamlet & Mastic Beach now. Again, thanks for sharing!!! -- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing? shipwright8378 posts in 3305 days #2 posted 12-09-2012 01:26 AM Good post Jim. It’s so nice to see you and Eric getting some boat building blogs going.Keep up the fine work. -- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/ TopamaxSurvivor18671 posts in 4183 days #3 posted 12-09-2012 01:30 AM I’m sure this will help a lot of Ljs. Thanks -- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence Dallas3599 posts in 2994 days #4 posted 12-09-2012 01:41 AM Thanks Jim! I used one of these when I was repairing and converting over the road buses into motor homes. Although not as extreme as boats, the angles and curves in a bus are not constant from front to back or even from port to starboard.Floor levels don’t stay the same and roof curve angles change within a foot. Even ceiling heights change from front to rear.As for finding the exact center of the coach, it can be a real guessing game because the sides aren’t straight up and down, they bow out at just below the windows. Think about that the next time you all see a Trailways or Greyhound going down the road….. they aren’t just big boxes on wheels, they have more curves than a the drunk blonde at the office party! -- Improvise.... Adapt...... Overcome! dusty2323 posts in 3936 days #5 posted 12-10-2012 12:27 PM I took a shot at remodeling an Airstream travel trailer. I had some really bold ideas about how much better I could do it than did Airstream. Was I ever wrong. The constantly changing curves on the inside of that Airstream got the best of me. I don’t think there was a straight line anywhere. I finished and used the remodel for years but I was never proud of what I had accomplished. -- Making Sawdust Safely Boatman531062 posts in 2703 days #6 posted 12-10-2012 12:45 PM Thanks for the comments all.DIY… How did your family fair with Sandy?Dusty… I too have thought about putting a nautical interior in an Airstream, maybe some day. -- Jim, Mid coast, Maine Ancorayachtservice.com home of the chain leg vise Dallas3599 posts in 2994 days #7 posted 12-10-2012 01:41 PM Dusty, I have done a couple of antique Airstreams, one a 1958 and the other a 1971. I had such a good time doing them, especially the interior front and rear corners where the roof panels are cut into rays to come down and meet the walls. -- Improvise.... Adapt...... Overcome! Mauricio7163 posts in 3658 days #8 posted 12-10-2012 03:29 PM Looks pretty cool Jim. Thanks for sharing the knowledge. Will you show how to use it? -- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch Boatman531062 posts in 2703 days #9 posted 12-10-2012 04:49 PM The simplest way to use it is just to lay your miter or bevel gauge on the board and adjust to the lines. The other use of finding the bevels form a lofting (the full size drawing of a boat) would require some knowledge of lofting. I’ll try if someone really would like me to however.Mauricio… How did you lay out the angles for your splayed legs on your work bench? Would something like this have helped do you think? Jim -- Jim, Mid coast, Maine Ancorayachtservice.com home of the chain leg vise Mauricio7163 posts in 3658 days #10 posted 12-10-2012 05:23 PM Hi Jim, yeah i had a little protractor thingy that I used to make a line on a piece of scrap and then set my bevel guage to that. So yeah, now that I think about it this thing would have come in handy! -- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch Sylvain881 posts in 3006 days #11 posted 12-10-2012 06:00 PM Excellent idea. For those of us working with the metric system,if we want 1cm per degree,it gives R=90 cm/(Pi/2)or R=180/3.14159…. =57.2958…. , let us say 57.3 cm By the way, if you replace “cm” by any convenient measure, it is still valid -- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn Brit7799 posts in 3349 days #12 posted 12-10-2012 06:22 PM Thanks for a very informative post Jim. One for the favourites. -- Andy - Old Chinese proverb says: "If you think something can't be done, don't interrupt man who is doing it." Boatman531062 posts in 2703 days #13 posted 12-10-2012 06:36 PM Thanks Syllvain for doing the metric math you are correct on all accounts. I’m stll surprised by the world wide audience of the different forums. Thanks again for giving the metric equivalent. Mauricio… Fortunately you used your little protractor just once to mark that scrap and then after refered to the scrap so at least you had some consistency. And whether or not you were even a half a degree off on you project it was of little consequence as long as they were all the same. The third installment is geared more toward hand tool use. So hang in there. -- Jim, Mid coast, Maine Ancorayachtservice.com home of the chain leg vise Mauricio7163 posts in 3658 days #14 posted 12-10-2012 06:44 PM Good, I look forward to the hand tool portion of the program, mostly because I could never get my crappy power tools to achieve that kind of precision. -- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch BigTiny1676 posts in 3395 days #15 posted 12-19-2012 10:19 PM Thanks for sharing. One more for the favorites list. Paul -- The nicer the nice, the higher the price!

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