Angle finder tool

[chris99z71]

Hey, all
I just added a new item to the downloads section. It's a very simple spreadsheet with a drawing and link to make a precision angle measuring tool.
http://ncwoodworker.net/forums/downloads.php?do=file&id=108&act=down
I was inspired by this tool -
http://www.amazon.com/exec/obidos/tg/detail/-/B00064RWWY/ref=sr_1_9/102-9791459-4316125?%5Fencoding=UTF8&v=glance
Click on the "see more pictures" link for more detailed pictures.

I just didn't want to shell out $180 for it...
I think the tool could be made with a few pieces of 3/4" x 3/8" steel stock (or stainless...dare to dream...), a few bolts, a 6" dial calliper or similar device, a few quick holes on a drill press, and a tap to match your bolts.
I haven't made this yet, but I was thinking of how to accurately set a mitre fence on a table saw crosscut sled.

So, in the spreadsheet, start by entering your three dimensions, A B & C.
Then set your angle and measure dimension D. Look up dimension D in the spreadsheet, the law of Cosines does it's magic and voila! You've got a super precise angle.

The only possible problem I see is that the holes must be pretty precisely centered on each of the pieces of flat stock.

What do you guys think? Will it work?

 

[Monty]

That's an interesting concept. I don't see any reason at all why it wouldn't work. The only thing I personally would be concerned about would be whether I could get tight enough tolerances in pivot pin hole - any slop at all there and the acuracy would be ruined out at the tips.

What do you want to use this for? I would imagine it might be useful for a woodturner who wants precise angles for segmented turnings...

One question about the tool you linked to: do you have any idea why there are these holes in the ends of the arms (1-9 and A-H)?

 

[chris99z71]

Insomniac,
I was thinking the same thing about the pivot hole. If you clamped a strait edge and an end stop to your drill press table, you could atleast get it in the same place on both pieces. Also, if you leave the pivot bolt sticking out of the top, you can measure distances B and C accurately by subtracting half the diameter of the bolt and half of the pin diameter (A). Since the spreadsheet takes into account specific B and C measurements, I think that you could get plenty close enough. I'd like to make one and put it on a known 45° triangle and see how close it is... I'd like to think it's closer than any other way I can think to measure the angle.

I would like to use this gadget to accurately set fence angles on a table saw crosscut sled. I've never turned anything (except my head when the girls go by...) so I couldn't comment on the other use you suggested.

On the "inspirational" product, I believe the far pins are an alternative measuring option for if you don't have a set of calipers. I'd guess that their look-up table for using the distal pins are set so that if you want X angle, use holes 4 and F and it works out to an even measurement with the ruler. Just my guess. That way you're not trying to measure 512ths of an inch.