Make a Sine Bar for perfect angles First Time Every Time!

i have a need to lay out some odd angles very precisely and accurately in my case those angles are 6.7 degrees 1.4 degrees and 4.8 degrees and there's no way that i can measure that degree of precision of an ordinary protractor but fortunately there is a traditional easy low-tech way of getting angles to that degree of precision welcome to workshop essentials this is a sign bar now if you're an engineer you'll probably be looking at this and thinking blimey steve that's a big one and indeed it is it's 10 inches from the center of this anvil to the center of this anvil i could have made it smaller but the bigger it is the more accurate it will be and multiplying numbers by 10 is very easy so that's why i'm working in inches and it's 10 inches from there to there by using a very precisely made spacer i can set the angle of this very accurately so this one is 0.84 inches long and if i put it underneath one end like that that gives me 4.8 degrees and i know now that that slope is accurately 4.8 degrees and if i swap it for a slightly bigger one this will give me 6.7 degrees and if i go much bigger this one is 5 inches and this will actually give me 30 degrees like that so how do we make a sign bar well i started with a piece of maple a bit longer than i needed so i've got something to get hold of and i machined it up and then i drilled two holes exactly 10 inches apart how do you do that well i made a spacer exactly 10 inches long now my digital calipers only go up to 6 inches you can get them that go up to 8 inches for not very much more money and you can get them which go up to 12 inches but it tends to get a bit spendy then so i simply did this by eye i got my best ruler and my best glasses and i'm got it to 10 inches as finely as i can possibly measure by eye simply by starting off a little bit too big and shooting the end until it looked right right well looking at this i have got to take off about a 30 second of an inch in length so i'm going to do that with my shooting board nearly let's try one more pass i think that will do very nicely thank you inches then using this 10 inch spacer i put a 20 millimeter drill in my drill press set a stop and put my piece of maple against the stop and drilled a hole and then inserted the 10 inch spacer to drill the second hole so the two holes were now exactly 10 inches apart these brass cylinders or anvils are 20 millimeters in diameter and 20 millimeters long they were made for me by my friend stuart one of the last jobs he did before he died you are sorely missed my friend then there was a little bit of work to do on the bandsaw it needs to have some relief space here so that you've got space to put a piece of wood in there and there needs to be a little bit of relief behind the heel of this back one as well so that was one of the bandsaw the curved bit was done by hand because i've got a quite a wide blade set up on my bandsaw at the moment and it was all cleaned up and the whole thing took me an hour if that so very easy to make i'll just stop this stick into my bench i think be a good idea let's see i'm using an epoxy adhesive to glue the anvils into the holes there we go the final bit is absolutely crucial and that is this edge here has to be trimmed on the table saw so that it's exactly parallel to this cotangent okay it must be absolutely perfectly parallel to that and i was really glad that i've got a good blade guard that covers the entire blade because to hold this against the fence i've got to get my hands closer to the blade than i would normally like but because it covers it exactly i felt fairly well protected very well protected actually now i need to make my spaces and whilst it's not easy to measure angles to one decimal place it is easy to measure distances and to a greater precision than one decimal place as well so when you were at school were you one of the guys at the back of the class writing on the desk or were you paying attention i hope it was the latter because we are going to use signs now if you remember signs signs are the displacements sideways as an angle is rotated the greater the angle the greater the sine at zero the sine is zero and at ninety degrees the angle is one unit length and the every sign every angle has a sign and you can find them in a book like this this is my zeus book table of natural signs now unfortunately this gives me angles in degrees and minutes 10 minutes 20 30 40 50 60 minutes 60 minutes is one degree and my sketchup model gives me angles in decimal angles i want 1.17 so i can either just interpolate or i can ask my favorite friend hey google what's the sign of 6.7 degrees sign 6.7 degrees is 0.117 hey google thank you very much i'm honored to serve hey google so you should be you're only a robot that may be true but i have a heart of gold [Music] so armed with that data i can cut my spacer very slightly oversize on my crosscut saw and then just shoot it until i get the reading that i want so we'll set it to inches and that gives me three decimal places and this needs to be 0.8 0.84 inches long it's 0.835 that's close enough in my book 835-8355 and that will give me an angle of 4.8 degrees when it's underneath there like that and i've got spacers this is this one gives me 6.7 this one gives me five that's five inches that gives me 30 degrees now there is a limitation with this and that my uh digital vernier only goes up to 150 millimeters or six inches so if i want more than that let's say i want to set to use it to reach 45 degrees well that's 0.707 the sine of 45 is 0.707 so that means my spacer needs to be 7.07 inches long and this only goes to 6. so this is what we do we temporarily stick on an extra bit and shoot the end square so the two are dead flush if i close my eyes i can't feel the join there and then i can measure let's just make sure it's zeroed i can measure that so that is 3.65 and this is 3.44 which makes 7.09 and we want 7.07 so i haven't got to take very much off that to get that to the right length absolutely absolutely perfect absolutely perfect and then i could just take off this extra bit it's only stuck on with double-sided tape and i've got a spacer suitable for doing 45 degrees so how do we use this in the workshop in anger well there are two common scenarios in my workshop and one of them is on the table saw and the other is to set a sliding bevel like this let's go over to the saw if i want to set my my defense i can do that with my sign bar i need some folding wedges these just go together and lock in the mitre track like that i can put a roofing square up against them like that so that it's dead square across my table saw then i set my sign bar up against that it is helpful if you've got three hands but if you haven't you just have to be careful and then i can just set my fence against the sign bar like that and that is set at 30 degrees as accurately as you could possibly want it and of course one of the really great things about this is if i'm doing handed parts i can simply turn that over like that and i've got my fence set at 30 degrees in the opposite direction again perfectly three-handedly accurately like that perfect to set a sliding bevel i'm going to use my shooting board and this is a tim russo design you'll find it on the fine woodworking videos it's excellent i thoroughly recommend it and of course it has to be square it's not much of a shooting board if it's not square this space it gives me 6.7 degrees like that and then i can just set my sliding bevel and that is now 6.7 degrees off square and that's now set to 6.7 degrees so if you have a need for some very accurate and precise angles i'd suggest you invest in one of these it's fast it's accurate it's precise and it's satisfying to do because we we're keeping traditional techniques alive and it doesn't break the bank that's all good in my book until the next time cheerio

Channel: Steve Maskery

Views: 21,114

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Id: M5n6lXU2d_8

Length: 13min 3sec (783 seconds)

Published: Tue Jun 21 2022