Struggling with duplicating angles

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Forum topic by toddbeaulieu posted 11-16-2010 05:11 PM 1268 views 0 times favorited 8 replies Add to Favorites Watch
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779 posts in 2428 days

11-16-2010 05:11 PM

Apparently, buying equipment is easier than becoming competent with it.

One recurring struggle for me is working with angles. I’d love to find a local class that deals with basic skills like that (planing, chiseling, etc. ... will have to check back in with Woodcraft). Anyway …

Case in point:

I’m building a cupola and I’m finally at the roofing stage. I’ve got the cedar shingles on, and I want to cut “trim” pieces to run vertically down each of the four corners (from the peak). These will be angled and mitered. Because the slope of the roof is not 45, the miter isn’t 45. After putting my weak resoning skills through a workout, my theory is that if I use the protractor to mirror the corner angle (flat on two planes of the roof, wrapping around the corner) I can then use the angled end cut of the protractor to set the table saw.

I’d love to hear your wisdon on some points and questions that came to mind when trying to solve this problem:

1. Until I get my cabinet saw powered up (it’s only been 10 months, cut me some slack), I’m stuck with a small 8 1/4” table top saw and there’s no way I trust the angle indicator. I really want to transfer the angle, rather than setting it to what some other device tells me it was. I’d be amazed if they coincided.

2. My protractor is a manual sliding model. No readout. Should I get one with a readout? If so, do I really want digital? I get this nagging feeling that analog would give me a better sense for where a measurement would be relative to others, if that makes sense. I attached an image of the protractor that I have.

3. The round end on the protractor makes it impossible to set it down flush on the table saw, so there’s no way to trasfer the angle. In fact, all the protractors that I see online seem to have huge pivot points that I assume would present the same problem.

4. Overall, I really struggle with angles on the table saw. I’m CONSTANTLY cutting miters the wrong way! I just haven’t figured out a system for knowing which way to place the piece, and just as importantly, how to compensate for the angle when setting the fence.

Yeah … I know … I’m a mess!

8 replies so far

View lumberdustjohn's profile


1262 posts in 2591 days

#1 posted 11-16-2010 06:29 PM

Practice with scrap pieces until you get it right, then lock them in.

The more mistakes I make the more I learn.

-- Safety first because someone needs you.

View TopamaxSurvivor's profile


17577 posts in 3100 days

#2 posted 11-16-2010 06:49 PM

Story sticks for lenght and blocks for angles are the key to repeat cuts.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View CampD's profile


1464 posts in 2910 days

#3 posted 11-16-2010 07:01 PM

Unless the cupola is built to NASA specs, the angle will never be the same as you go around,
if you want it perfect, guess the angle and cheat-up on it

-- Doug...

View toddbeaulieu's profile


779 posts in 2428 days

#4 posted 11-16-2010 07:07 PM

Yeah … I know the angles are a bit different on each side. I’m just trying to lean how to duplicate an angle using tools, instead of completely guessing. I fit the base to the ridge by paintakingly sneaking up on it while on the roof. I think that was the best approach for something so intricate, but I ought to be able to set a saw blade angle to match a protractor angle, right??

View NBeener's profile


4808 posts in 2598 days

#5 posted 11-16-2010 07:18 PM

I know you put one in the pictures, but (and I ask because I’m not certain) ... isn’t this what a bevel gauge was born to do ?

After all … you don’t really care if everything is at seven degrees. You care that all the angles that should match … do match, right ?

-- -- Neil

View toddbeaulieu's profile


779 posts in 2428 days

#6 posted 11-16-2010 07:24 PM

Well, I assumed that it was the right tool, but i can’t set it on the saw top. It might be hard to see, but if you look at the photo, the brass end protrudes past the blade. So when I set it down, it rocks on that rounded end a bit. Maybe I should just go into the local woodcraft and beg for tips on using what I bought from them.

View NBeener's profile


4808 posts in 2598 days

#7 posted 11-16-2010 07:38 PM

Wow. I DO see that.

I just took a look at my bevel gauge (Starrett), and … while you COULD MAKE the ‘fixed’ piece stick out like that … you can also make sure that it doesn’t. Either piece can slide past the locking pin. There are slots in BOTH pieces.

If there’s no way to adjust yours so that you don’t have that rounded edge sticking out, then … I’m not sure it’s a good bevel gauge.

-- -- Neil

View RalphBarker's profile


80 posts in 2193 days

#8 posted 11-16-2010 07:42 PM

To snatch the cap shingle from Master Kan’s hand, you must first “become one” with the angle, Grasshopper. ;-)

To arrive at the combined angle of the two components of the cap shingle, slide the metal part of the miter gauge all the way down to form a rounded corner and lay it on the the shingles to either side of the roof’s hip (and, tighten the wing nut, of course). If you were cutting a real miter, you’d take half that angle for each side. But, you don’t really want a miter, but rather an angled lap joint, so water will be directed to either side.

To transfer the angle to the table saw, you’ll need to raise the saw blade all the way up, so the metal blade of the miter gauge will touch the saw blade. In theory, the measured angle will be the angle for both pieces, but with one side flipped end-for-end. In practice, the roof angle may be too shallow to set directly, so you’ll probably have to mark that on a sheet pf paper, and then reset the miter gauge to the complementary angle – the difference between the measured angle and 180°. Then, you’d rip the two components on-edge, with the blade lowered to a safe cutting height. A higher auxiliary fence may be needed to keep the singles vertically stable.

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