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Journey of the n00b #2: In search of an elegant solution: Creating a 45 degree reference angle.

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Blog entry by Michael Wilson posted 01-26-2013 05:47 PM 1103 reads 0 times favorited 6 comments Add to Favorites Watch
« Part 1: The End Table. Part 2 of Journey of the n00b series no next part

THIS has proven to be a challenge. I’m currently unemployed, so buying tools is just about out of the question. (The occasional pine board maybe. But even that is pushing it.)

I’ve got a box in my head and wanted to use mitered joints. This got me Yak Shaving in to creating jigs and the like.

But I got stuck on the fact that I don’t have a reasonable 45 degree reference angle. Nothing I can use to clamp a workpiece down to my table saw sled.

MAYBE my table saw cuts a precise 45 degree angle when I’ve yanked it in to position and tried to hold it there while tightening it back down. And MAYbe my harbor freight chop saw cuts a precision 45 degree angle. But neither of them are capable of creating a long enough cut that errors within the tolerance I’m looking for will be exposed. So they’re really both out. (Though I suppose I could cut 8 or 9 pieces, then stack them and see if the resulting triangle has two equal sides. But the margin for error in that process is really high.)

SO I started thinking… How would I create one that was within sufficient tolerance for cutting long miters?

I can cut something square, so I started there with a piece of 3/4” birch ply. Then I thought: “Well, if I position it ‘corner to corner’ along the kerf line of my table saw sled and clamped it down, then I could be sure I was cutting along the right angle.” I went through rather a lot of plywood trying to keep that positioning stable. No matter how close I got, I was still off by enough that it bothered me. (As determined by the component pieces not matching up.)

I’ve got a couple ideas kicking around in my sick little mad scientist head. But they get weirder and weirder as I get more and more frustrated.

Once you have one, (say, out of a piece of ply) you can make any number for any thickness, etc.

How would you do it? No protractor and no 45 degree square kicking around.



6 comments so far

View Airframer's profile (online now)

Airframer

2753 posts in 704 days


#1 posted 01-26-2013 05:59 PM

You could always print one out from the internet?

I have done that a couple times for rulers in a pinch.

Here are a couple but a simple google search will give you more choices..

http://www.fuzzimo.com/free-vector-ruler-triangle-protractor/

http://thinkzone.wlonk.com/MathFun/Protractor.htm

-- Eric - "I'm getting proficient with these hand jobbers. - BigRedKnothead"

View Michael Wilson's profile

Michael Wilson

587 posts in 1242 days


#2 posted 01-26-2013 06:02 PM

What a strange solution :-)

I was locked in my head to creating the initial reference out of wood.

I would never have considered that. Seems like a silly original post now.

Thanks o/

View Grumpymike's profile

Grumpymike

1188 posts in 1066 days


#3 posted 01-26-2013 06:27 PM

The best referance is a draftmans triangle … they are clear plastic, exactly dead on and cost a couple of bucks.
(much cheaper than all the wood you will throw away)
There are two types that you will want to have in your shop, there’s the 30, 60, 90 degree, and the most used 45, 90 degree. You can find them at Wally World in the stationary sectio, Target, and at most stationary stores.
Or use your framing square, place it on the edge of your work, mark say the 6 on each blade and you will have a 45 with two 6 inch sides.

-- Grumpy old guy, and lookin' good Doin' it. ... Surprise Az.

View Michael Wilson's profile

Michael Wilson

587 posts in 1242 days


#4 posted 01-26-2013 06:41 PM

Yeah, ya know, this is annoying me enough that I’ll head out to get some. Heck, even office max will have those in the drafting section.

The trick with cutting the angle as you suggest, is keeping it aligned with the saw blade within the acceptable tolerance level. That’s the problem I was having.

View Dan Lyke's profile

Dan Lyke

1489 posts in 2876 days


#5 posted 01-29-2013 04:27 PM

So if I needed to start from scratch to make a high quality 45° reference, I’d do the following:

First, I’d build an as-accurate-as-I-could 90° reference angle. Rip like a two foot wide piece of plywood, cut it at what I think 90° is, flip one piece over, hold it against a straight edge, the resulting gap is twice the error. Lather, rinse, repeat.

Now that I have that, cut a 45°, put them together to make a 90° and see how they compare to the reference edge.

Note that given the quantity of (hopefully high-quality) plywood that will be consumed in this process, it might not be any cheaper than just buying a good reference, but done carefully it can give you a reference that’s as good as anything you can buy.

The real question is: How do you set up your tools to be repeatably set to these angles. A sled for the tablesaw makes sense, but I don’t know what you’d set up for your miter saw.

-- Dan Lyke, Petaluma California, http://www.flutterby.net/User:DanLyke

View Michael Wilson's profile

Michael Wilson

587 posts in 1242 days


#6 posted 01-29-2013 07:20 PM

I’ve got a crosscut sled that’s ugly as home grown sin, but accurate to within a couple thou over about 18-20 inches, so I’m happy with that.

That means I can create a repeatable square. This also gives me a valid test (as you mentioned.)

I have precisely zero faith that my miter/combination saw doesn’t cut around corners, so that’s out for anything other than rough length cutting.

I’ve now got a set of plastic squares that I’m going to use for initial cuts on pieces that will become permanent references.

Plus, the pieces I’d been making my attempts with are large enough that I’ll now be able to trim them true and use them, so I’m less worried about actual waste than I was earlier. (And those attempts were very close, just not close enough.)

But I’m still interested in the geometry of the problem.

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