« back to Jigs & Fixtures forum
Forum topic by lizardhead  posted 03092012 07:47 PM  2843 views  0 times favorited  12 replies 
03092012 07:47 PM 
I do segmented turning, so I use angles, problem is with a small protractor the margin for error is very minuet, respectfully a very large protractor would have a larger margin for error. I want to take a 24” x 24” piece of MDF and make a large protractor to cut some angled jigs for my miter slider on my bandsaw. My thinking is that if 45 degrees is 1/2 of 90 then the angle would be ticked out on my MDF at from lower left to upper right, OK that’s a no brainer, now if using that 24” square and 45 degree figures I would divide 24” into 45. = 9/16” Take that answer and multiply by the number of degrees I want 15 and I get 8”, so if I rise 8” from the lower right the angle from that point to the lower left should be 15 degrees. Close but not right. What am I wrong about. And if you plan on giving me vectors and X’s & Y’s & C2R & qfb’s don’t bother I do not care to go to school. If that’s the only way to get there then there is no bother to explain other that “THERE IS NO OTHER WAY” They have a website angles for Dummies, but I am not as smart as a Dummy.  Good, Better, BestNever let it restAlways make your Good be Better & your Better Best 
12 replies so far
#1 posted 03092012 08:04 PM 
Would this help?  Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton 
#2 posted 03092012 08:05 PM 
You need one of these – Dial Protractor ±5 Arc Minutes Accuracy. These are cool, a bit pricey. You can get one at Grizzly model G9900 – $53.95 MIKE  See pictures on Flickr  http://www.flickr.com/photos/44216106@N07/ And visit my Facebook page  facebook.com/MTEnterprises 
#3 posted 03092012 08:09 PM 
Gene that’s a pretty good idea too, I like it.  See pictures on Flickr  http://www.flickr.com/photos/44216106@N07/ And visit my Facebook page  facebook.com/MTEnterprises 
#4 posted 03092012 08:24 PM 
Hey, hey, hey! I like that rig there Mike! Lizardhead, I too do segmented turning. Unless money is an issue, just get an Incra miter gauge and never worry again. I have an Incra V120 that I got on sale for $50, and it’s awesome! After calibration, it’s dead on. I’ve made 36 segment rings with no gap, just dead on accurate. It has 120 angle stops, so you can hit almost any angle needed. My next project for it is going to be a miter sled like the Incra Miter Express, or if I deem it easier to by than build, I may just buy one. They’re not cheap, but man do they work good! However, if you have the money, an Incra Miter 1000HD is just an incredible piece of equipment. Not cheap, but it will end all your angle woes for good. But, if money is an issue, which I completely understand (and feel in my pocket!), I will find out from my dad how to do the math you’re looking for tonight.  Kenny 
#5 posted 03092012 08:29 PM 
Did you take trig in school? Those function will give you precise figures to use.  Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them."  D.H. Lawrence 
#6 posted 03092012 08:35 PM 
Ok, I thought about your issue for a minute. Your problem is that you are measuring in a straight line for 8”, not in an arc as would be proper. Think of a protractor, they arc half circles. You will need to measure 8” of travel a the radius appropriate to the protractor you are making. So, find the radius of the arc you want to make, make yourself a trammel that same length, and when you figure the measurement, move the trammel point that far. It should work perfectly. But remember, you need to measure the distance of the arc, not in a straight line.  Kenny 
#7 posted 03092012 08:45 PM 
Or, find the circumference of the circle you want to make, and use that for base number to make your calculations for the angles. IE: The circumference of a circle 24” in diameter is 75.39”. Divide that by 360 and you get .209. Multiply that by 15 and you get 3.14” Go to a 48” diameter circle and you get 150.79” circumference, divide by 360 is .418, now multiply by 15 and you get 6.28 Just remember, you can’t simply go in a straight line, not without converting the measurement in some way. I’m not 100% positive, but I am pretty sure this will work.  Kenny 
#8 posted 03092012 08:54 PM 
If there are an even number of segments, it would be easier to bisect the angles to divide them than to make precise measurements on the circumference.  Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them."  D.H. Lawrence 
#9 posted 03102012 02:59 AM 
The very act of asking the question indicates you do want to go to school. Kenny’s right – the distance between the “ticks” as you call them is not constant if you are measuring them along the vertical edge of the square – they get farther apart as you go up. Now, there is a formula for figuring out how far up the left side to measure for any particular angle, and it only involves looking up one value in a table (readily available on the internet) and one multiplication (the value from the table times the 24” width of the square). If you’re game, I’ll talk you through it. I even found an online calculator for the number, so you aren’t limited to whole degrees for your angle.  "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power."  Abraham Lincoln 
#10 posted 03102012 03:53 AM 
Well it’s a done deal I got me an Incra 1000HD I’ll let you know tomorrow how it works.  Good, Better, BestNever let it restAlways make your Good be Better & your Better Best 
#11 posted 03152012 09:10 PM 
Hi Dave,  Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!! 
#12 posted 03152012 10:05 PM 
I picked up 7 sheets of “Dupont Corian” 24” to 30” square each for $50 bucks from a local installation company. I set that new 1000hd up and cut me 4 Corian Jigs each one at a different angle 151822.5 &30 degree. Then I had a neighbor make me 4 mitre slider bars with two 1/4” tapped holes. Maybe it would be easier to just take a pic and enter them as a project. Not made of wood so I might not hear the end of it—(for posting here instead of a blog) Wait I can do it this way—  Good, Better, BestNever let it restAlways make your Good be Better & your Better Best 
Have your say...
You must be signed in to reply.

Forum  Topics 

Woodworking Skill Share

11563 
Woodturning

1737 
Woodcarving

373 
Scrollsawing

301 
Joinery

1185 
Finishing

4342 
Designing Woodworking Projects

6204 
Power Tools, Hardware and Accessories

26148 
CNC Woodworking

159 
Hand Tools

4965 
Jigs & Fixtures

1294 
Wood & Lumber

5757 
Safety in the Woodworking Shop

1289 
Focus on the Workspace

1971 
Sweating for Bucks Through Woodworking

1140 
Woodworking Trade & Swap

4480 
LumberJocks.com Site Feedback

2129 
Coffee Lounge

8503 