Setting cursors on the TSO parallel guide without guesswork (design weakness ?)

Jason Hagen said:
There is also the issue of making sure both stops are exactly the same. If they aren’t and you use the 3000 rail vs 1400, your board could be be quite a few millimeters (or sixteenths) off.

This doesn't sound right to me.  My TSO guides attach to the rail using the GRS rail squares.  The measurements are therefore at either end of the cut.  Any difference in the calibration of your flip stops would be over the whole length of the cut.
I have experienced problems where the rail has moved after I've set up the flip stops, but that was due to the way I was using the system (not clamping, cutting too fast).
Regards
Bob
 
Svar said:
Packard said:
I am reminded of the very pricy bamboo slide rule (with plastic facings).  The crosshair was purported to be a black widow spider's web stretched and glued to the plastic because it was impossible (back then) to mill a fine enough groove for the cross-hair. 
Spider's web? This is odd. Would black hair be easier to obtain? Regardless, there is no need for milling. Just slice/scratch it with sharp blade, make it as fine as you want.

I looked online for verification and could not find it.  Perhaps the spiderweb story was apocryphal.  But in 1967 I bought it, almost new in the original packaging from an engineering student in financial crisis for (as I recall) the outlandish price of $75.00.  For $75.00 I damn well had better have gotten a genuine black widow's spider web filament for the crosshair. 

(I just checked with CPI inflation calculator and that $75.00 in 1967 is $633.62 in 2021 dollars.)

In 1972 my sister bought the first available Hewlett-Packard scientific calculator and never picked up the slide rule ever again.  If you have ever used log tables, you will understand why. 

By the way that rudimentary calculator cost $400.00 in 1972--about $2,700.00 in today's money.  You can buy the same performance from a $30.00 calculator today.

As a side note, Post (the slide ruler maker) called the indicator a "cursor" back then.  I always thought it was a computer term.

 
Packard said:
Svar said:
Packard said:
I am reminded of the very pricy bamboo slide rule (with plastic facings).  The crosshair was purported to be a black widow spider's web stretched and glued to the plastic because it was impossible (back then) to mill a fine enough groove for the cross-hair. 
Spider's web? This is odd. Would black hair be easier to obtain? Regardless, there is no need for milling. Just slice/scratch it with sharp blade, make it as fine as you want.
I found this reference from Wiki, so the black widow's web might be true after all.

Originally crosshairs were constructed out of hair or spiderweb, these materials being sufficiently thin and strong. Many modern scopes use wire crosshairs, which can be flattened to various degrees to change the width.
I looked online for verification and could not find it.  Perhaps the spiderweb story was apocryphal.  But in 1967 I bought it, almost new in the original packaging from an engineering student in financial crisis for (as I recall) the outlandish price of $75.00.  For $75.00 I darn well had better have gotten a genuine black widow's spider web filament for the crosshair. 

(I just checked with CPI inflation calculator and that $75.00 in 1967 is $633.62 in 2021 dollars.)

In 1972 my sister bought the first available Hewlett-Packard scientific calculator and never picked up the slide rule ever again.  If you have ever used log tables, you will understand why. 

By the way that rudimentary calculator cost $400.00 in 1972--about $2,700.00 in today's money.  You can buy the same performance from a $30.00 calculator today.

As a side note, Post (the slide ruler maker) called the indicator a "cursor" back then.  I always thought it was a computer term.
 
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