Threads not deep enough

After success on threading the rod, I needed to make a "spud" to fit on the bottom of my new fixed toolpost arrangement. It's a 25mm boss extending about 8mm under the solid tool post base which that locates the tool post assembly top the cross slide..

My spud is essentially a nut. The bolt goes down thru the QCTP and slips thru a section of the tool post base (~45mm) then threads thru the remainder of the base (~15mm), and emerge where the spud can be threaded onto threads continuing past the end of the solid tool post base. The spud will locate the position of the Tool post assembly to the cross slide and will lock the rod against the bottom of the base.

All this is a long way of describing the fact that I now need to cut internal threads. And in fact, I did so with a single point cut. Since I had the piece I threaded in the last few days, I was able to use that thread rod as a reference measuring tool.

But, it seems that this approach makes the internal thread an inferior cousin to the external thread. The external thread can be measured with thread wires and screw thread micrometers. As well as ring gauges or nuts.

What other options, beyond trial fitting, work to measure internal threads?
 
Trial fitting with custom made gauges. Turn some min/max threads to whatever you like (opposite ends of a single piece is convenient), then cut to fit. There *are* genuine thread measuring tools, but they're abominably expensive.

GsT
 
rronald said:
  1. All the pics I see for the three wire method show the two wires under the thread being measured and the single wire on top. Seems silly to me. You can see the harder side of the problem if the double wires are on top of the thread.
  2. found it far easier to install the two wires on top and close the micrometer on them w/o worrying about the third wire. Don't even pick that one up until the two side-by-side wires are (lightly) clamped in place by the micrometer.
Click to expand...
Whatever works for you . Put the wires in a piece of styrofoam makes life easy .
 
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