Once set up the bolts were turned and we were off performing op 1 on the bolts.

The first op turned the minor diameter of the [...]]]> We bought this tool from Shars to allow use to hole the jaws in proper position the cut the proper diameter in the jaws for the bolt.

Once set up the bolts were turned and we were off performing op 1 on the bolts.

The first op turned the minor diameter of the bolt, faced the bolt and drilled it for the firing pin.

The second operation again turned for minor diameter, faced the bolt, and drilled the hole for the firing pin to be inserted. In addition the major diameter was turned.

Test bolts were made to set up each operation in the lathe and for the additional operations in the mill,

All test bolts were marked with double “x’s” on both sides. This prevents confusion later.

With all the bolts completed for the first two operations it is not off for the third operation.

With the third op we go to the manual lathe to cut the firing pin hole to the correct diameter and depth with a square shoulder on the bottom. This allows the firing pin spring to set flat.

With the end mill dialed in it is just a matter using the dro’s to go to the correct depth.

With no engineered drawings to work from the first item of business to take care of was making a drawing of the part with all the dimensions. To do this we used micrometers, feeler gauges and an [...]]]> This post is about making the pivot button for the bolt hold open device for the AR-180B.

With no engineered drawings to work from the first item of business to take care of was making a drawing of the part with all the dimensions. To do this we used micrometers, feeler gauges and an optical comparator.

Using these measurement devices we were able to accurately measure the  the complete button. We also used references from parts suppliers to verify correct dimensions for matching components.

http://www.mcmaster.com/#97431a290/=xirvt8

Side-Mount External Retaining Ring (E-Style)

Black-Finish Steel, for 7/32″ Shaft Diameter

For Shaft Diameter	7/32“
Fits Groove
Diameter	0.188″
Width	0.029″
Ring Size
(A)	0.437″
Thickness	0.025″
Additional Specifications	Black-Finish Steel
RoHS	Compliant

Snap rings into the groove from the side of the shaft. Their three prongs make contact with the shaft and provide a wider shoulder than other external retaining rings for a larger retaining surface. They are magnetic.

Black-finish and zinc and yellow chromate-plated steel rings have a minimum Rockwell hardness of C47.

Next came a solid model of the part.

A program was written with master cam to run on the cnc lathe.

This is the video of machining the part on the lathe.

This is an picture of the part as it comes off the lathe when the first op is completed.

A comparison of the original part to the newly machined one.

What has been done so far with still more to be made.

The second op to come