Fisher Machine Shop
Micro Tapping Guide and Pee Dee Thread Wires

1/2" Shank Micro Tap Guide
Pee Dee Thread Measuring Wires
Ordering Information
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1/2" Shank Micro Tap Guide

#20MTG 1/2" Shank Micro Tap Guide #20MTG 1/2" Shank Micro Tap Guide #20MTG 1/2" Shank Micro Tap Guide
#20MTG 1/2" Shank Micro Tap Guide $12.50
3/16" diameter spring loaded point that can be reversed.
The tip has a point on one end (l) and a concave taper (c) on the other. It is disassembled to switch between the two ends (r).
The point will retract 1/2" into the body.
tap guide on lathe
tap guide on drill press
It Can be chucked up in the lathe tailstock or the drillpress
tap guide with wrench
The point is placed in the small hole at the end of the tap wrench (did you ever wonder what that hole was for?) and the tailstock advanced until the tap is against the hole and the point is fully retracted. You can also use this without a tap wrench if the tap has a center hole. Turn the tap with a regular wrench that fits the flats.
close up
As you turn the tap wrench, the point springs forward, maintaining pressure againt the wrench, keeping it in alignment with the hole you are tapping.
tap guide, using the cone
The concave end is good for smaller taps, which usually have a 60 deg. taper ground at the end.This allows great support and alignment. Use a tiny wrench to turn the tap.

Pee Dee Thread Measuring Wires

No.16 Pee Dee Thread Measuring Wires $27.50

48 Wires - 16 Different Sizes
Accurate to .0001 over the center one inch section

Measures Threads from 3 to 48 Threads per Inch
Metric Threads from .5mm to 6mm Pitch
Acme Threads from 3 to 16 Threads per Inch

Comes with Plastic Sleeve and Charts for Use

Often Copied, Never Equalled

#20MTG 1/2" Shank Micro Tap Guide

Measuring Thread Pitch Diameter

.045 Wires (specified in chart), 13 tpi thread, measures .515" over wires.
Pitch Diameter is .515-.06838 (constant found in chart) = .4466" Class 3A fit.

When cutting a thread to a specified PD, add the constant to the minimum and maximum PD (found in Machinery's Handbook).
For 1/2-13 class 3, high is .4500 and low is .4463, adding the constant (.0684) to both the high and low PD's you have what your mic should read. In this case between (4500+.0648=).5184 and (.4463+.0648=).5147.
More precise than checking against a hex nut, cheaper than a thread gage!

measuring pitch diameter PEE  DEE

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