Sunday, November 13, 2011

Aeron Pistol Bulk-Fill Thread Cover

One of my Aeron pistols was missing the cover that fits over the male bulk-fill threads at the bottom of the grip.  The factory supplies a press-fit plastic cap. While it works fine, I need/want a second thread cover.  The bulk-fill thread on the Czech pistols is M18 x 2mm.  It took a couple weeks to track down a bottoming tap that didn't turn this into a $30 project.

Nick recently sent some 1" aluminum hex stock that had been languishing in his carport for years.  Soon as I saw it, I knew it would be perfect for this.  Chopped about a 3" length off to start.

As is the norm, the end was faced off square.  A really sharp bit with some negative top rake and a high turning speed gave a dead flat surface in a single pass.  Some cutting fluid didn't hurt either. 

Rather than drill a hole first, I just plunged the boring bar into the aluminum face to start the hole.  Took a few minutes, but I was able to bring the hole to approx 24mm deep, then bore the diameter to 16mm.  Note:  Not all boring bars work for this type of cut.

With a M18 x 2mm bottoming tap I was able to start the first couple threads by hand turning the headstock and feeding the tap gently until it started cutting.  Once the tap starts cutting thread, it pulls itself into the work as long as the quill on the tail stock is free to move.

Transferred the work to the vise and switched to a larger tap handle. 

About that much.  Oh, I'd like to also recess the e-clip above the thread.

Finding the bottom of the hole.

Cut it beyond the rod and all will be OK. 

The parting tool loves aluminum.

Chucked the cut off piece of work and cleaned up some corners, cut some decorative bevels...

With the boring bar, I cut a relief at the top of the thread to clear the e-clip.

Ran a piece of Scotchbrite over it to get a matte finish.  I could definitely use a second one for the other pistol.  Beats the pants off the plastic cover.

Inside view of the M18 x 2mm threads as well as the cut for the e-clip.

When (if) I make another, it'll probably have to be blackened. 

More soon.