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PostPosted: Sun Aug 19, 2018 11:01 pm 
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Location: Bowmanville, Ontario
I've posted numerous times figuring out my Benjamin. Tuning it, modifying it, trying to making this mediocre rifle a formidable beast. It IS a machine, and it IS possible to make it run like a well tuned one. I understand the mechanics of these rifles now, I know what I need to do to make it do what I want, I still believe it is possible. I have all the ingredients, I just have to put them together.

So, I'll start a new thread of my progress at this point. Anyone interested can either ask or go through my previous many posts about this rifle.

So, recently I discovered that much of the accuracy issues stem from the barrel wiggling in the forks. I had already replaced the plastic washers with brass ones, then some time later made the brass washer fit better and added spring steel shims stock for a better sliding surface.
Well, now I'm starting over. Away with the precious bandaids, I'm rebuilding the connection between the Barr and forks for the best fit my machines and my ability will allow. I have been receiving suggestions if procedures and the best materials to use over at machinistgazette.com which is the machining forum I've been a part of since the beginning. Much of my machining knowledge has come from those fine gents. I digress...

I cleaned up and polished the inside of the forks better. I milled out the small .700" washer pockets for a much larger 1" pocket and cleaned up the Chinese machining hack job. The breech is not true. From one side to the other it's .005" tapered. Not desirable. So I clamped the breech in the mill vise and squared the cutting surface with the barrel. If the barrel is not set square in the breech I want to mill out the washer pocket square with the barrel allowing the breech to sit crooked (if it in fact is crooked, don't know) but the barrel sit in line with the rest of the gun, the breech seal with take up any difference if any. Were talking maybe a thou if anything.

Milled out a 1" pocket and I'm pretty much done for the night. I don't have 1" brass stock at the moment. Will have to grab some tomorrow from the metal supplier. But I requested info from the collective at my other forum regarding the best materials to use in this situation. Either brass, or maybe bronze, or even tool steel and harden it.

That's all for now. More later this week probably. Hopefully.


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File comment: Much larger engagement surface.
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File comment: Old washer and new pocket
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Shawn


Fully rebuilt Benjamin .22 classic
Some other junk rifles
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PostPosted: Mon Aug 20, 2018 2:53 pm 
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Location: Rocky Mtn Hse Alberta
Have you addressed the hinge pin loosening?

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PostPosted: Mon Aug 20, 2018 3:29 pm 
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The hinge screw or the spring pin?
Previously, i loctited the threads and put some anti-seize on the tapered screw head to keep it from galling and getting stuck. It did not move again. The increased wiggle came from the rough surfaces wearing down the brass washers and the face of the forks was not flat but convex.

I am rebuilding the whole hinge. I will likely be making a new shoulder screw too as this one isn't of very good quality.
As far as the spring pin, I am going to leave it for now and not do the whole stronger spring/barrel release I spoke about before. If this rebuilding of the washers works, I shouldn't need a stronger spring as there will hopefully be zero play in the barrel.

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Shawn


Fully rebuilt Benjamin .22 classic
Some other junk rifles


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PostPosted: Mon Aug 20, 2018 10:36 pm 
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A bit more work tonight. Not much. I mulled around ideas on the machinist site of what material to use for the washers and bushing. Bronze? aluminum bronze? brass? Hardened tool steel?
Settled on 360 brass. Maybe not the best material I could use, but certainly one I could afford. The aluminum bronze was $125/foot.... Nope...

I ordered it this morning, I'll pick it up tomorrow. I also ordered a .254" chucking reamer for the hinge screw. I remeasure the stock screw and it turns out my mic was hitting a burr on the shoulder of the screw giving me a false reading.
It is tapered by only 4 tenths (.0004") that is very acceptable...

The progress tonight was to clean up and hone the inside of the forks.
I faced off the inside d the forks with a 1/2" 4 flute carbide endmill, then sanded/honed.
They are now very smooth, down to 1000 grit, and flat to .0015", which is also very acceptable. The remaining convex is due to the sanding/honing. If that .0015" convex causes me issues, it will likely be something like a 1/4" at 50 yards... If this all works...


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Shawn


Fully rebuilt Benjamin .22 classic
Some other junk rifles
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PostPosted: Mon Aug 20, 2018 10:51 pm 
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Location: Caronport, Saskatchewan
Nice work!

Sent from my LG-M154 using Tapatalk

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PostPosted: Mon Aug 20, 2018 11:27 pm 
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Location: Rocky Mtn Hse Alberta
Would you have a pic of the oem hinge pieces?
The Crosman I am familiar with uses a bushing for the pivot
Cheers
Walter

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PostPosted: Mon Aug 20, 2018 11:43 pm 
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The stock setup for the hinge is the shoulder bolt, plastic washers, and a steel sleeve (not a bushing). Pictured below. Cept, I replaced the plastic washers with brass ones.

The sleeve is hardened but is not round and had terrible rolled edges, and too much play between it and the screw.


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PostPosted: Tue Aug 21, 2018 11:43 am 
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Curious now. What makes it ‘not a bushing’?
Clearance with screw has nothing to do with lockup

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PostPosted: Tue Aug 21, 2018 12:17 pm 
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A bushing is generally seen as something with a tight sliding fit that is used in place of a bearing. An oilite bronze bushing on the end of an old electric motor, for example.

The sleeve in the hinge is just more of a sleeve. To make the fitwith the screw a bit better, and spreads the forces of the hinge out over the screw, the sleeve is hardened as well, so to reduce on the possibility of wear in the hinge.

You're right, looseness in the screw/hinge does not effect lockup.
What it IS causing is play in the hinge. The breech is tightly closed. But the play/gap between the sleeve and the screw is allowing the barrel to wiggle back and forth around the screw. And under the intense recoil, I believe that wiggle is throwing my accuracy.
So the poorly machined washers/forks is allowing side to side wiggle (it's also allowing radial twist as well, on a very small scale), and the sleeve/screw is allowing up and down wiggle.

When I put the gun in a vise and put pressure on the barrel, I could move the muzzle an 1/8" in all directions just from the play in the hinge. And that's after really cranking on the hinge screw.

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Fully rebuilt Benjamin .22 classic
Some other junk rifles


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PostPosted: Tue Aug 21, 2018 12:20 pm 
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Hang on. Let me re-word something.

IF the sleeve was machines to acceptable tolerances, I would call it a bushing because technically it is taking up the wear of the pivoting hinge, which is what a bushing does.

I relieved it of its bushing title when I saw poorly machined it was... It is just a tube that was hardened and cut to size. Or vise-versa. If it was ground to fit, then I'd call it a bushing.

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Fully rebuilt Benjamin .22 classic
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PostPosted: Tue Aug 21, 2018 2:29 pm 
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As designed it is indeed a bushing lol

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PostPosted: Tue Aug 21, 2018 4:32 pm 
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"hey, looked good on the computer", "good from far, far from good". A few phrases that come to mind here. It is very likely designed as a bushing, but in practice a drink straw may have done better...

They sheared the tube to length, so there is a HUGE rolled over burr on the inside edges on one side on both ends. It has worn a groove in the screw, which was one of the reasons I was considering making a new screw. But doing so would make me have to build the cylindrical grinding fixture for my surface grinder I planned to build one day much sooner to grind this screw to size..... One project at a time.... :shock:

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Fully rebuilt Benjamin .22 classic
Some other junk rifles


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PostPosted: Tue Aug 21, 2018 5:34 pm 
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If the screw is tight and the bushing properly captured by the screw and washers there is zero movement of bushing against the screw. When properly arranged the barrel will not fall by its own weight due to the fit of the assembly. Until you have that kind of fit you will not have accuracy.

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PostPosted: Tue Aug 21, 2018 5:43 pm 
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Nailed it. And that is what I'm trying to achieve.

If all the mating surfaces are true and the allowable play/slack in all the mating parts is, let's say, .005" and under, I SHOULD be able to fire the gun accurately even without the spring loaded barrel catch. Even without cranking down the hinge screw.

If there is no movement in the arrangement, there's no room for turbulence to be created, the guns harmonics should flow through the hinge as if it was a fixed barrel.

...I'm getting excited...lol

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Fully rebuilt Benjamin .22 classic
Some other junk rifles


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PostPosted: Fri Aug 24, 2018 12:50 am 
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Done.

I wanted to use oilite bronze for the bushing/washer but it would have been way too expensive.
Used the 360 brass.

Came out well. Turned the bushing/washers. Two of them. Cut some oil grooves in the face. Froze the bushings and heated the breech up just a bit. They popped right in. Then indicated it in the mill and reamed the bushings together in the breech.

After a bit of screw cleaning/sanding everything fit together extremely well.

A bit of anti-seize on the tapered screw head to keep it from welding itself in the hole. Did a bit of cranking but not super tight.
The hinge is very smooth. Only .002" play and most of that is likely deflection. It's very solid now.
Put everything back together and just fired off a couple pellets in the back yard to set everything home and eject oil or crud that made it into the barrel. Dieseled pretty good on the first shot. A big pile of sparks in the dark on the first shot.

Remounted the scope. I changed all the black oxide screws out for stainless. The old screws were getting chewed up.

Won't be able to test accuracy for a few days likely.
But I'm optimistic. The gun is quite quiet for its power. No noticeable barrel wiggle at all. Looks promising.


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Shawn


Fully rebuilt Benjamin .22 classic
Some other junk rifles


Last edited by Carpenter84 on Fri Aug 24, 2018 12:54 am, edited 1 time in total.
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