Sunday, April 30, 2017

Carbon Fiber Sleeve on the IZH 61 -- Part 2 Final

With the barrel sleeved in carbon fiber, it was necessary to make a new barrel band with a larger bore.

The IZH barrel band allows for mounting an open sight.  Not gonna bother with that.  After sleeving the barrel and pondering a new barrel band, I found this excellent post on the Canadian Airgun forum.  Mr. Samija has apparently already gone down this path while tuning a model 61 for his son. He certainly did a much cleaner and tighter tolerance job than I.

Despite my recent problems machining plastic, I bought a 1" diameter piece of acetal from McMaster-Carr.  Think it was under $5.

Lacking a 15mm drill bit to match the OD of the carbon tube, I considered boring to size on the mill, then remembered to cross check the size against fractional bits.  15mm = 0.5905", 19/32 = 0.5937  I can probably live with a couple thousandths clearance.

With a .500 edge finder, I found the side of the rod, then dialed in 0.750" to be on center (1/2 the edge finder tip diameter + 1/2 the diameter of the work piece).

Drilled a hole in each end.  Figured I'd screw up at least once.



Test fit then cut the ends off to what I think is 1/4" too long.

The original barrel band was not the correct height for the threaded hole in the breech.  Was hoping it was, so I could simply make this to the same center line height.  Nope.  

Started to get all fancy with my measurement, but the thought of measuring the top of the forend on the gun to the center of the threaded hole in the breech started to make my head hurt.

Gonna wing it.  Drilled for the mounting screw.

Flipped and faced the top.


Test fit. 

It looked like the height was off by about 0.020". This is actually closer than the factory band, but not close enough.  Went back to the lathe and stepped the OD to make it a bit slimmer.  Then made the base even shorter.  Scuffed it with a maroon Scotchbrite pad in an attempt to match the IZH finish.

Actually went shorter, because I didn't have a 0.020" washer, but I did have some acetal washers that are about 0.050".   Found that it's often easier to source a thicker washer than one made from what amounts to shim stock.

Used the assembly itself to approximate the correct height. 

Here's the amount the barrel needs to come up.

Washer installed.  The finish looks like an acceptable match. 

Don't see an alignment issue, so it's done.

A few glamor shots.  The wisteria over the deck is in full swing and dropping blooms everywhere.

So, the IZH continues to evolve.  It's now very close to what I envisioned for this little rifle.  Still want to make a shorter muzzle brake and spend more time shooting it.

Thanks for checking in.