Wednesday, November 2, 2011

Overhauling the IZH 53M -- Part 2

Getting back to the IZH 53M after a short hiatus...

The steel rod came in to replace the plastic factory end cap with something a bit more substantial.  Before turning the piece, I installed some beater jaws into the scrolling chuck and trued them up with a small boring bar.

Sidetrack:  Also made some extra vise jaws for the Wilton, too, since I was working on tools, with tools.  Absolutely nothing to do with this post--but they're nice.

And definitely better than what came with the vise.

OK.  Yes, end caps.  The factory cap is plastic and, well, it's plastic...   I cock the gun, point it at the target and I'm staring at this piece of black plastic that the mainspring is bearing directly against.  Pointed at my eye.    I know it's fine and it's not going to break.  But still...

FrankB has me working in analog with this mic.  The end cap is 0.923" on the slip fit into the tube.  That'll be close enough. 

Chucked a piece of 1.125" OD free machining steel...

...and quickly brought it to size.  Removing the crosslide allowed me to test fit the compression tube to the cap without changing the set up.

Spotted with a center drill.

Gradually drilled a 0.500" counterbore.  That's a lot of steel shavings. 

Switched tool holders and used another boring bar to cut a stepped counterbore for the end of the mainspring.

The other day, I went through the extra mainsprings on hand and found a likely replacement; the original was slightly canted.

This is how it fits.

Need a spring guide to prevent the replacement spring from buckling.  The blue plastic piece came from the scrap box--it's part of an old spring guide from a Rock Shox mountain bike fork.  It's just slightly over 0.500" diameter.  Saved it for exactly this kind of project.

Chopped off the flanged end and set up a dead center to prevent the rod from flexing away from the cut. 

This will be the cap end.

Taking this down until it press fits into the cap. 

Once it fit into the counterbore of the end cap, it was pressed in and the cap was chucked.

A few thousandths went away in a couple light passes.   When the spring slid over the guide without binding, it was good.  Had this been a high velocity spring rifle, a tighter fit would be useful to quell vibration. 

Rounded the end freehand in the lathe with a file.

The gray smudges on the guide is moly grease transferred from the spring. I'll probably add a rotation washer, figure out how to secure the cap to the tube (and the guide to the cap) then shape the rear of the cap and blue it.

Should finish it up in another day or two.  Check back soon.