Thursday, May 31, 2012

IZH-61 Shenanigans Part 2 Final

Finishing up reassembly of the IZH-61.  Gonna gloss over most of this since we've covered it before in detail.

A coat of copper anti-seize on the piston body, spring and acetal guide.

The spring guide on an IZH 60/61 goes into the piston first--then the spring fits over it.  This is the opposite of most guns I've rebuilt.

Of course, this tab of sheet metal isn't on the IZH schematic.  It disengages the ratchet on the cocking lever pivot once the piston is drawn completely rearward and caught by the sear.

It fits here on the end cap with the bent end under the ratchet.  Forget it and it'll be impossible to return the cocking lever to the closed position.  Guess how I know that?

End cap installed and rotated to engage the catch.

Greased the cocking lever

I installed it at a 90 degree angle then rotated it into alignment. 

Like so.

Wiggle and shimmy the pivot end into location then install the pin.

Here's what started this whole mess.  The catch doesn't quite line up.  I have to flex the cocking lever upward to make it work, and that's annoying.

Another pic.

Clamped the solid pivot end of the lever in some aluminum vise jaws.

And gave it a good push.  I was surprised at how sturdy the lever was to lateral force.  I expected it to bend rather easily.  Had to bend/test fit/bend a couple times until it had moved far enough to line up the latch.


For further reassembly and tuning instructions, see some of our older IZH-60/61 posts.

Finished the reassembly and found that the sear wouldn't catch the piston without a hard pull at the end of the cocking stroke.  Knew immediately that the spring was coil bound.  Could've ground down the spring, but I elected to shave down the base of the new guide.

Quit after taking off a few thousandths.  There will be some minor length variances on the mainsprings due to the ends being ground, but the factory really nailed the spring length.  There's only about the thickness of a nickel available before the gun is coil-bound.   If you add rotation washer(s) or a top hat weight to the piston, the spring will have to be shortened by a comparable amount.

Check back soon.

Monday, May 28, 2012

More IZH 61 Shenanigans Part 1--A New Spring Guide

Getting back to the Baikal IZH 61. 

Used a deburring tool to easily clean up the burs on the cocking lever slots in the end cap and the piston body.

It's like running a metal removing razor knife across the sharp corners.

Remembering back to my first IZH 61, the too short spring guide had to go.  I ballparked the length inside of the piston and subtracted a few hundredths.

The original, short steel guide.  On the left is a piece of 0.750" diameter acetal (aka: delrin).

Chucked the acetal in the 3-jaw and took a few quick cuts.  Went a bit too deep on the first cut, so I backed off a few hundredths. 

I'll cut the undersize part off.  It's a mistake to think that you need to accurately measure everything when using a lathe or mill.  It's pretty quick to simply cut until the spring fits over the guide then extend that depth to the length of the guide.

Faced off the undersized portion and adjusted the tool post to cut a bevel.

Rounded the front edge so it'll slide smoothly through the coils.

Found a parting tool and chopped off the guide leaving a flange.

A bit longer than the factory part.  

And several thou larger in diameter.  Didn't want a tight fit to the spring for such a low-powered gun.  The velocity loss would be large.

OK.  Reassemble the gun next time around and see about realigning that cocking lever catch.