Gallery, Projects and General > How do I?? |
Checking a 45 degree square? |
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DMIOM:
--- Quote from: loply on May 27, 2015, 08:06:33 AM ---DMIOM, I see how that would prove that the two 45s add up to 90, but you wouldn't know if you had a 44 and a 46 though? Or am I missing something?...... --- End quote --- The key is to keep the same face up and just rotate it about one corner ('A' in the sketch below), so you're doubling the angle of one corner - and if its the desired 45 degrees, then you'll match your 90 degree master square, if not the discrepancy will be magnified by a factor of two. Annotated version of sketch attached. Dave |
Fergus OMore:
I would stick with something which equates to 5 or 10" which are normal Imperial sines. They make things easier in the trig! My 5" sine bar- I've just discovered is heavily corroded from when the roof came off my workshop( in Newcastle) Again, I have to find( if they are there) what my Jo blocks are doing. I got the Myford sorted out- without too much damage. Anyhow, settle for multiples of 5 which are easy-er. Regards Norman |
lordedmond:
Norman With ref to sine bars first what language are your Jo blocks if they are inferior then by all means use a 5 inch sine bar the the Jo block stack would be in imp, but if like me you have metric Jo blocks then a 127 mm sine bar is needed As then the answers would be in mm To the OP The level of truth that you are wanting is get is less that 1 arc second if my brain cell is ok today but other will no doubt correct this and this is going to be tricky you will have to put a insulating handle on it to stop thermal changes . How long have you had the material ageing they use to make Jo blocks down the road ,they used to bury the steel for a year befor use Stuart Good luck in your quest |
loply:
Dave - that's boggling my mind a bit! I'm still a bit unsure how I would know which way the error was, I'm sure it's possible I'm just getting confused :hammer: Having said that - I think I've just come up with a way of doing it which only requires one 45 degree part and the master square- If I set up an indicator on the master square such that it's tip is about 10mm off the surface of the square, pointing downwards, and bring the 45 degree and butt it up against the master square such that the indicator reads off it's height (say about 10mm 'in' to the 45), note the indicator reading, then turn the 45 around and do the same on the other side. If it's not 45 the reading will be different, if it is 45 the reading should be the same. It would then just be a case of scraping off whatever the error was from the 'high' side, and re-flatening the thing. |
loply:
This is what I mean: |
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