Jig Borer - I reveal my Ignorance and Stupidity

I don't know if this will add much but here goes. I ran several jig borers when I worked in the tapered and miss-located hole room. The P&Ws were like big bridgeports without the knees and the Sips were gantry's with a column on both sides of the table. Had to wear sweat shirts even in the summer, 68 deg. The big Pratt & Whitneys used rods and mic heads to measure distance and the Sip's used scales and optics. They were used to locate holes in exact positions and bore them to tenths tolerance, checked with bore gauges. We did a lot of tooling plates, some of these we could ream if the tolerance was loose enough, like slip or press pins. But the real trick was the precision boring heads as they would hold tenths and leave great finishes.
All the tooling around the area were high precision, angle plates, 3,4,6 blocks, dividing heads, rotary tables. One of the jig bores in another shop was a Dixi it was set up like a boring mill with a rotary table built into it.
My favorite was the smaller Sip because of the type and size of the work. The only complaint was you had to sit side-saddle because of the location of the column and head. But neat machines.

emm.. bore gauges were set by the tool room for size and we read them by placing them in the bore like a telescope gauge but you read the size as you rocked it back and forth on the dial gauge. They came to us with a master block set to the nominal size we wanted so we could make sure they were still correctly set.

Jim
 
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