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| Checking a 45 degree square? |
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| loply:
Hi folks, Some time ago I made myself a whole set of precision references for scraping/inspecting etc, including a very accurate master square. I want to make a 45 degree reference from a slab of cast iron I have but I'm struggling to think of a way of checking it. I can think of a way of doing it if I make two or three, but that's 2x or 3x the work! Anybody know an ingenious way to test for 45 degrees without a known standard to compare to, and without making 2x of them? Cheers, Rich |
| loply:
I have a high precision level too, but no sine bar or sine plate. |
| Fergus OMore:
Two 45's make a right angle, four make- a straight line whilst 8 get you back to where you started. source Euclid. |
| Arbalist:
Yes, bit tricky. Easy to make one but not so easy to check! :scratch: the only thing I can think of is to place it on a flat and scribe the outline, then flip and scribe it three times and see if it meets the starting point! If there's a gap it's under 45° and if it goes over the line it's over 45°... Here's how I make mine. |
| Lew_Merrick_PE:
Rich, One of the tricks I use with great regularity is to drill and ream a set of dowel pin holes in a piece of (say) 1/4 X 6 inch material (usually either aluminum or steel). My Trav-a-Dials (the forerunner of DRO's) allow me to do so ±.0005 inch, so my result will be quite accurate. I then press in dowel pins and mill off the "outside" and end up with an angle plate of whatever (angular) size I need. Thus, for a 45° plate, I would ream my holes at: (.375,.375), (5.250,0), & (5.250,5.250) from the corner of a 6 inch square piece. I then insert (call it ø1/4 inch) dowel pins two at a time and mill my (call it .350 inch) offset edge around the periphery. If I have done this as accurately as my machine is capable, then my resulting angle will be ±.0104° (0°0"2'). Would that be close enough for your purposes? I usually make them in pairs. The angle gets steel stamped on the "face" of the plate. And they end up "living" in boxes where they can be found and reused. |
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