Slavia ZVP, Dovetail Math

I really need to make that front sight. The first thing I need to do is to measure the dovetail slot.

A caliper and a set of PeeDee thread wires.

I chose a wire size that was just below the top of the slot.

With wires in either side of the dovetail I measured the width, I got .217"

But when I verified this measurement with a gage block stack it would not fit. Calipers aren't that accurate.

So I tried .216" and it was spot on.

A side view.

Here's a drawing.
The value we want is the width of the bottom of the slot.
We know the diameter of the pins, and the thickness of the gage block stack.
I assumed the dovetail was 60 degrees. It seemed to be.
So, knowing those and looking up the formula for measuring dovetails in Machinery's Handbook:
y=b–D(1 + cot 1⁄2α)

y=.2160
D=.063
α=60
b= base length
Since we need to know b, it becomes:
b=y+D(1 + cot 1⁄2α)

"cot" is a fancy way of saying 1/tan

tan 30 = 0.57735026918962576450914878050196
cot 30 = 1.7320508075688772935274463415059
+1=2.7320508075688772935274463415059
*D=0.17211920087683926949222911951487
+y=0.38811920087683926949222911951487

So that's how I got a value of .3881"
Honestly, I just wanted an excuse to do a little math tonight.

Short Sick Ramble

Just checking in, my creativity has been destroyed by a common cold, posting will be light this week. The good news is it's giving me plenty of time to think about how to make the sights for the ZVP...

Here are some fun links to pass the time:

• A neat article in Gun Digest about blank powered Mexican guns
• Parker and Parker Hale Scopes
• A Spring Calculator
• O-ring specialists
• Grease 101

Slavia ZVP, Miscellany

I did a number of things to my ZVP...first off, here's a neat Czech site that has some pictures, manuals and drawings of the ZVP.

Boring out a cup to make a new piston seal.

Forming the seal. I did exactly what worked before with the Predom Lucznik.

The end cap screwed on easily.

I thought the interface between the trigger and sear was worth noting. It's a gradual curved contact surface.

The pistol back together. The rear sight is off of my Slavia 618, I need to make a copy...

The breech was loose, so I tightened up the pivot bolt. Only problem was that the lock screw divot no longer matched up.

So I stamped some thin shim washers using the method outlined in my post about the Diana 6M, I ended up using one washer .005" thick and one .008" thick.

Which allowed the divot to line up. All that remains is making the front and rear sight...

Slavia ZVP, Cleaning and the Stock Nut

Found some time to work on the ZVP...

After cleaning I felt the transfer port was a bit scarred up.

So I carefully filed and lapped most of damage while trying to not remove too much material.

The front sight...a blob of solder.

I milled it off.

Then filed and hit it with some cold blue. It's bluer than it looks here, but not as blue as blue can be...

Turning down some steel for the stock nut (that is the nut that holds the action to the wood grips). Since it was missing I didn't have anything to go on other than the pictures I've seen on the web, but I figured that 10mm diameter x 10mm long was probably right.

Tapping 5mm x .8mm which matches the threads on the rod. I love my collection of taps.

Slotting the nut.

Parted off and chamfering.

The nut works!

Slavia ZVP, Making a Spring Guide.

Well, in order to make sure the SVP works I needed to make a new spring guide.

The old spring guide, such as it is.

Starting to turn down some 1" steel...

Turned to the correct diameter.

Chamfered at the end, filed smooth, about to part off.

The new guide.

I reassembled the pistol to check function. Using the old piston seal and with no other work it managed to spit a pellet downrange. So I have a pistol that works, now I need to make it work well.

Mounting a Williams Sight on a Crosman 167, Part 2

So I need some longer mounting screws...

Turned and threads cut.

And cut off.

Slotting.

The lower base hole needed to be elongated.

As did the shim.

A tiny vise holds the sight blade (? insert?) and I slot it deeper.

And mill the top down. The goal was to have it roughly in the middle of the adjustment range when the rifle was zeroed at 10 yards.

I slapped some paint on the exposed aluminum. Mounted solidly. I think I could get away without using a shim if I could overlook the gap between the barrel and the base.

a bunch of shots to sight it in and then 5 shots in a row (only at 7 yards...too dark outside) pretty much on center.

Mounting a Williams Sight on a Crosman 167, Part 1

I love my Crosman 167, but I absolutely hate the cheap stamped rear sight. Recently I bought a lot of random Williams rear sights on Ebay, for about $5.00 a piece. So I set about adapting one to the Crosman.

The Williams sight and existing sight. Windage is adjusted by loosening one screw and pushing the sight over.

Elevation adjustment is achieved by pushing in or out the notched ramp.

The Williams sight, while not a micrometer sight, has clearly marked index scales and is much easier to adjust.

Mounted in one screw hole, you can see that the other hole is not in the right place. I could tap the barrel, but I prefer to keep it in stock form (or easily reversible).

The sight base has too large a radius.

A piece of aluminum was turned to the radius of the sight base (I got it close and then checked until it seemed to have full contact.) Then it was offset eccentrically in the chuck.

Drilling begins.

Drilled out to 1/2"

Then to 9/16". The Taig isn't ideal for drilling with larger drills, but in aluminum it works fine.

Parted off.

With a plug inserted, and held in a vee block, the eccentric piece is adjusted.

Sawing off my shim...

The shim fits perfectly.

The underside.

Marking one screw hole.

More to come...