Rebarreling and Home-Shop Machining

This project is well suited to a collet chuck.

I wanted to put in service a Starrett indicator hole attachment shown in photo 1. The indicator that I had, that was a suitable back plunger type, was a Craftsman indicator. The rod that holds the indicator was too long to use with the Starrett hole attachment. The original Craftsman hole attachment is shown in photo 2. All that I needed to do was to make a new shorter attachment rod for the indicator. This would allow the full 1 5/8 inch insertion of the Starrett attachment. The advantages of this attachment over the original is a longer length and a larger ball size that works better for an interrupted surfaces like the inside of the collet which has three slits.

I decided to use 0.25 inch stainless rod from a K&S assortment that made an appearance at my local Hardware and Hobby Store. This rod is either drawn or cold rolled which means the precision of the surface is about 0.001 inch. This was suitable for this project.

Unfortunately, the first step was to regrind the 0.25 inch collet with the Dremel tool post grinder that I describe on my Website. I had purchased the collet a long time ago and had never used it due to the excessive runout. I inserted the stainless stock and measured runout next to the collet and at 3 inches. I centered the far end in a precision drill chuck while I tightened the collet. When I removed the drill chuck on the far end, the runout was .003 inch next to the collet and .030 inch at 3 inches (Photo 3). That is gawdawful for a collet chuck. The rod was not visibly bent. I reground the collet (Photo 4) and measured the runout on the edge of the hole (photo 1) and it was .0001 inch. I rechucked the rod and the runout with the first end chucked was 0.0007 near the collet and .003 inch at 3 inch. I chucked the other end and it was 0.0005 inch near the collet and 0.002 inch at 3 inch. A lot of this is probably runout and bend in the stock. That’s a 10 fold improvement at 3 inches.

Photo 4-7 show the machining steps that I used to make the extension. The Homemade Die Head in photo 7 is described in this Journal. There was no visible runout on the finished thread. Photo 8-9 show the finished extension.

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