Machining advice

[chongman]

Before I'd do anything with the tube I'd call Don....and keep calling till I got him on the phone.

[1377x]

thats ugly!
even crosman doesnt let anything out the door looking like that!

[Fronzdan]

Too late, Chongman, lol.  I worked on the tube a little.  But after more time really examining things, I know the source of the problem.  Now I just need to figure out how to fix it.

Yes the tube is a bit rough inside.  Definitely not the shotgun bore-look like the Crosman tubes have.  So I will sand it down a bit.  I dont have any dowels, but I think that will work.  I just wrapped my finger and did some sanding with 600 grit (too fine) and then polished with a dremel and it is smoother.  So with a dowel and coarser grit to start, I'm pretty sure I can get it much smoother.  While that will help, that's not the problem.

The winner is...ding ding ding....1377x!  He nailed it.  The problem is related to the hammer pin.  The Mellon hammer pin hole hole is slightly out of tolerance (larger than Crosman).  So the pin wiggles around in the hole more.  And the ledge where the "seat" sits, as 1377x called it, is shallower on the Mellon hammer, not as wide and not quite "flat".  So the skirt DOES ride up above the surface of the hammer when pulled/pushed.  This is indeed the lock washer effect as BDS called it.  Without any spring...just the hammer, tube and pin, I could not slide the hammer back and forth by pushing on the pin, the pin seat keeps binding up on the tube...or rather, the inner edges of the groove in the tube.

The hammers side by side...



The Crosman with the pin inserted...a little hard to see but the pin sits lower and doesn't wiggle much.



The Mellon with the pin inserted.  Pin sits much higher, almost coming out at rest.  When pulling the seat sticks out.



So now what to do?  Clearly the Cothran tube, or actually the hammer pin slot in the Cothran tube is less forgiving of the pin issue.  As I mentioned, the Crosman tube doesn't bind.  So should I try filing down the inner edges of the slot in the tube in hopes of making it "bite" less"?

Or do I drill down the hammer's ledge a bit deeper so the pin sits lower and doesn't rise up too high?  I think this is probably the better approach.  But how the heck do you drill a ledge like that?  I'm think a flat bottomed drill bit?!

[JEBert]

A squared off and resharpened drill bit.  You do know how to resharpen a bit by hand, don't you?  Question is, how hard is this hammer?  Has it been hardened after machining?  If your bit won't cut it, I would try to use a Dremel type grindstone to deepen the hole a little.  Put the right diameter grindstone (that has been flattened) in the drill press with the belts set on the fastest set of pulleys and put the hammer in the drill press vice.  Take it easy and check the depth often, specially if using the drill.  You don't want it too deep either.
Cheers,

[1377x]

three options plus a maybe i would use in the hammer binding situation
1) before you start option one,turn the hammer pin upside down see if it will fit inside the pin hole on the mellon hammer tight i mean it  can barely go in there.if it is a very tight fit ,
you can proceed.turn down the washer on the pin until it is the size of or close to the size if the pin.when you are ready to use the hammer pin keep it upside down and tap it into the hole.thats why it has to be tight.

2) if you have an old dremel bit iirc they are 1/8 diameter this is tricky and takes sizing.because the bit will fall through the hole a spring guide has to be used inside the hammer to keep the bit from falling through.it will bind the hammer spring if it does fall through.
it will be a loose fit.what you need to do is cut the bit long enough to not touch the top of the beech,if its touching the top the gun wont cock and not so short the pin falls out if the gun turns upside down

3) get a drill bit slightly bigger than the pin hole. cut it so it will be a little longer than the height of the bolt.bevel the cut end so it can go into the pin hole tight fit is wanted.you can tap the drill bit in until it is level with the top of the bolt
it will be tight enough to cock the gun and not so loose its going to fall out

4) the maybe
try to source a 2100/ 2200 hammer pin.they have a thin washer and will eliminate the binding and work great with your hammer.
i call it the last resort because you will have to send for it,if its not handy

i dont like the idea of messing with the seat in the hammer without the proper tools.make to wide the pin wobbles and binds,make it to deep the bolt rides over the pin
if you are confident in your skills then by all means alter the hammer
and hope its not hardened

[crossliner]

Fun reading 

[BDS]

1377 said it all 

I think like you, the thought of starting the DC cycle all over again and fighting thru that mouse maze of communication makes you want to remedy this problem yourself

PS good pics of the ID of the tube, that is commercial grade tubing and is not electropolished like the good stuff.

[Fronzdan]

Final outcome...

I tossed out the idea with counterboring that ledge a little deeper.  I didn't have confidence in my tools (or my skills) to not end up enlarging the diameter even more, which would make the problem worse.

I checked using the pin upside down, but the hole was still too big and the pin easily dropped through into the well for the spring.  Same for an old dremel bit.

I looked around for alternatives and briefly considered sacrificing a drill bit to act as a pin and hammering it in, but then, it would be a pain to remove the hammer in the future, and we all know how often we completely dismantle our guns.

Also considered threading the hole in the hammer and screwing in some threaded rod with a bushing to cover the exposed threads.  But at that point I thought...awful lot of trouble for a $12 part (the hammer).

In the end, I polished the underside of the hammer pin slot, liberally lubed, and raked the hammer/pin back and forth a bunch of times to sort of break it in, then put her back together.  It will still get wedged if I just yank the bolt any old way.  But I found if I tilt the gun on it's left side, pull the bolt crisply as opposed to slowly, it cocks 100% of the time.  For now I can live with it.  I will pick  up some JB Weld and try filling the old hammer when I get a chance.

This is interesting.  When I dry fired it, it just sounded different.  More like a single click as it hits the valve.  With cartridge it fires fine, although I need to break out the Chrony to see if the numbers are lower than expected.  But what I think is happening is I'm getting  little/ no hammer bounce.  So maybe the loose pin is acting like an HDD, lol.  I'm definitely getting more shots per cart.

Anyway, here she is.  Silver and black two-tone.  The old 2240 frame was polished too...maybe someday I'll get around to polishing this frame too. But then if I do that, I'll want to polish the RJ breech....then get matching brake....then change the bolt....and on and on....

[1377x]

that looks good!
rj breech,dc tube ,rb grips ( ) p-rod tg/gf
its too bad the hammer didnt work out.i used disco hammer with the dremel bit hammer pin.it was loose like you said thats why i cut it long so when the gun tipped it would not fall out.to stop the pin from falling through a .22 casing was made into a spring guide inserted into the hammer.
no issues with it falling out,bending ,cocking the gun or shooting it
i wonder if you opened the pin hole up enough to fit a sight pin flush waist when screwed in
have you considered getting the p-rod hammer?
i just got one for my build instead of using the striker,a 1/4-28 set screw is being used .i still have to flatten and square off the end of the screw but its a perfect fit and close to the price of the custom hammer.