Replies

1. 
   BruceS | Aug 13, 2006 07:17pm | #1

   Polished Granite Test blocks for testing, Surface grinders for machining.

   Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

2. 
   GHR | Aug 14, 2006 02:09am | #2

   One laps a straight edge rubbing only the high spots with a loose abrasive. Automated machines do the same.

   To measure an optical flat is nice but a laser works.

1. 
   Archibald | Aug 14, 2006 09:06pm | #3

   Where do I get these lenses and laser and do they come with instructions?

1. 
   PeteBradley | Aug 14, 2006 09:35pm | #4

   What exactly are you trying to do? Accurately measuring large objects with precision less than a thousandth is non-trivial. You might be better off asking your question on the Practical Machinist forum.Pete

   Edited 8/14/2006 2:57 pm ET by PeteBradley

2. 
   RickL | Aug 28, 2006 02:49pm | #5

   I do machine repair and tune ups on jointers and a machined straight edge is more than enough. I even do metal work and don't need lasers to check flatness. I think you are going overboard especially since you are posting on a woodworking forum. Construction lasers aren't going to be anywhere close to a straight edge. An optical comparator is used in precise measuring with machine shops but it's for small parts.

   What exactly are you trying to do????? You doing some space shuttle work or something??

3. 
   MrLinux | Oct 15, 2006 05:45am | #6

   Use a dial indicator mounted on a surface gage base on good grade of surface plate (not less than "B" grade ... ignore the Woodcraft $20 model for this purpose) The surface plate is typically either black (lesser grade) or pink (better grades) granite, but properly ground or scraped steel / cast iron are also valid.

   Start at one end. Adjust the indicator to a slight load. Set the indicator dial to zero. Move the indicator along the edge being tested, noting variations in the indicated movement. When you find the low spot, reset the indicator at that spot and resweep the edge. This will give you the TIR (Total Indicator Runout) in easy to understand terms. (Technically speaking, you already had TIR on the first sweep ... but might not have known how to interpret what you observed. The second sweep should make all clear on that score.)

   This procedure can get you down to .0001" territory ... beyond that, prepare to shell out obscene money for a level of precision that is pretty much useless in woodworking.

   That said ... if you can hold .005" in wood, you're a better woodworker than I.