Machining advice

[Fronzdan]

Here's my issue:

I'm trying to use a p-rod trigger frame on a Cothran SS tube.  This includes a Mellon solid hammer.  The Cothran tube is not as polished inside the tube as a Crosman tube.  The surface is much rougher, I'm kind of surprised.  The solid hammer, in addition to having more surface area than a standard one, may be ever so slightly over tolerance in width.  And the "edges" on the back end are a little sharper than on a standard hammer.  The result....the solid hammer binds in the Cothran tube when trying to cock.  And I mean it wedges in there so you can't retract the bolt/hammer.  This is without the trig frame even installed, so it's nothing to do with the sear or anything.  Even with just the tube by itself with the hammer inserted, it doesn't slide as easily as the OEM one.

So what I'm thinking of doing is polishing the inside of the tube more and/or rounding off the edge of the hammer a little and/or turning down the hammer width a thousandth or so.  Does this make sense so far?  Of the three, I'm not sure if turning down the hammer width helps or hurts.

Problem...I don't have a lathe.  I have a power drill and a dremel.  I think I can get one of my polishing wheels from my dremel into the tube.  But how can I chuck up the hammer on either of those?  Is there some kind of bit that could go inside the hole in the hammer and then expand to hold it?

Btw standard hammer in a Cothran tube works.  Solid hammer in a standard Crosman tube works.  But the two together...not so good.  So another alternative could be to do the JB Weld solid hammer for the Cothran tube...but even then, I'd want to polish the hammer smooth so I still need the mystery attachment for my drill or dremel.

[breakfastchef]

I clearly understand what you want to do with the hammer. First, I have used pencils, dowels or whatever I could find pounded into the hammer hole so I could chuck it in my drill press. Second, the drill probably does not provide enough RPM's to bu useful. Third, a hammer does not have to be pretty; only functional. Maybe a combination of the hammer chucked to the drill and the Dremel would get you there making sure the rotation of each tool is opposite the other for more aggressive action. You could even go so far as to dilling a hole roughly the diameter of the hammer through some stock to reduce the wobble.

[BDS]

Good test on the Mellon hammer with a Cros tube and it works... shows you that your DC tube needs help (reaming/polishing) and the Mellon hammer may yet be oversized.

Yes ream and polish the DC tube regardless, I like a darn near mirror look and total deburr of all edges, slots, holes etc (64 finish minimum, more like a 32)

You can thread the hole in the hammer to accept a bolt/stud and then use that to chuck it into your power drill. Clamp the drill in a vise and  use emery paper on a solid flat device to remove  .001 or .002 of material and polish and radius edges.

[1377x]

are you doing this with the hammer pin attached?
if you have a 1377 try that hammer pin in the solid hammer and dc tube
my solid hammer was a little oversized also take a wood dowl that is a tight fit inside the hammer hole where the spring goes the fins a long tiny screw to go through the hammer pin hole make sure the head cant go through,then again it might not matter.tighten the screw into the wood,this is to keep the hammer from coming off while it is spinning.
i used 330 or 340 grit sandpaper wrapped it around the hammer and spun the hammer.checking the fit periodically.once i was satisfied with the fit i used 600 grit sandpaper followed by 800 grit then 1200 grit.once it was nice and shiny i used some rouge and a felt polishing wheel on a dremel,i guess any polishing bit would work ,a mirror finish is what you are after.then i dropped some moly oil on the hammer and in the tube

[0351_Vet]

What about using a Brake Cylinder hone? Like the  2 or 3 stone units to hone inside the tube? 

[BDS]

What about using a Brake Cylinder hone? Like the  2 or 3 stone units to hone inside the tube? 

Yup except, gotta be careful of the edges of  the drill holes and the slots, those lil stones work great on continuous surfaces, not so much on interrupted surfaces.

[JMJinNC]

I have a brake cylinder hone if you need it. Or you can get one from Harbor Freight for about $8.

You might try making a quick honing tool using a wooden dowel & sandpaper. A search on any springer AG forum regarding"crosshatching" should turn up results. This will solve the problem with the slots in the tube catching the honing stones.

JMJ

[Fronzdan]

Wow...all helpful advice.  Thanks everyone!

Never thought of a dowel...yeah that might work.  And I might try getting extra rigidity by putting a small screw or tack into the dowel through the pin hole.

I also think the tube needs polishing no matter what.  I was kind of surprised how rough it was when I really looked.  Usually they are smoother, like a shotgun barrel.  This one is almost "pebbled"...not tool marks or anything, just a texturing.  I quickly tried last night to polish it with the emery paper wrapped finger, but it didn't help...mainly because I was using 2000 grit, lol.  The textures just got shiny.  I guess I'll have to start out much coarser.  As I said, I have those abrasive puffy wheels for the dremel, which I used for polish jobs.  Might try those too.  Let me look up a brake cylinder hone so I can get an idea how that works.

1377x, you asked about a 1377 hammer pin.  I never compared them with the 22xx version.  Are they smaller diameter on the exposed side or something?  You think that is causing some friction?  I'll have to look at that tonight.


Ok just looked up brake cylinder hones.  The principal looks perfect, but I also worry about all the slots and holes would snag the stones and cause badness.  I did find "flexible hones" which are round abrasive brushes that come in different diameters and grit.  Perfect!  Except they are kind of pricey for what I want to do.

[1377x]

1377x, you asked about a 1377 hammer pin.  I never compared them with the 22xx version.  Are they smaller diameter on the exposed side or something?  You think that is causing some friction?  I'll have to look at that tonight

there is a difference in the size of the seat i am guessing its called.you know the ring around the hammer pin that keeps it from falling through the hole? the 1377 pin ring isnt as thick as the 2240 ring. found this out the other day when i put a 22xx pin in my 1377 hammer.it kept binding up every time i pulled the hammer back it wouldnt budge.when i found the 1377 pin and placed it in the 1377 ,the hammer slid like it is supposed to

[BDS]

Good call 1377, that's a "one-way" lock washer, the little tangs of sheet metal grip the OD of the pin and the thickness could be a real prob for clearance 

[BDS]

Wow...all helpful advice.  Thanks everyone!

Never thought of a dowel...yeah that might work.  And I might try getting extra rigidity by putting a small screw or tack into the dowel through the pin hole.

I also think the tube needs polishing no matter what.  I was kind of surprised how rough it was when I really looked.  Usually they are smoother, like a shotgun barrel.  This one is almost "pebbled"...not tool marks or anything, just a texturing.  I quickly tried last night to polish it with the emery paper wrapped finger, but it didn't help...mainly because I was using 2000 grit, lol.  The textures just got shiny.  I guess I'll have to start out much coarser.  As I said, I have those abrasive puffy wheels for the dremel, which I used for polish jobs.  Might try those too.  Let me look up a brake cylinder hone so I can get an idea how that works.

1377x, you asked about a 1377 hammer pin.  I never compared them with the 22xx version.  Are they smaller diameter on the exposed side or something?  You think that is causing some friction?  I'll have to look at that tonight.

With your latest comments... it sounds like that tube has an as-made or stock I.D. which DC never machined. All you will accomplish is polish the high spots with a dowel and emery paper, you need to cut some metal, about .002" overall.

[Fronzdan]

Hmm...you think that's always the way Cothran tubes come, or maybe did this one slip by?  I could contact him but I think we all know how long that can take.  I'll see if I can take a picture.

[JMJinNC]

You might try making a quick honing tool using a wooden dowel & sandpaper.
JMJ

Here's a good thread on honing the tube.

http://www.network54.com/Forum/79537/thread/1339357827/Home+methods+of+honing+compression+tubes.

Of course you want to smooth out the tube, not rough it up (crosshatching is what retains lube in the walls of the cylinder, technique is also used in engines), but the construction of your sandpaper hone should be similar.

I made on from a dowel, cut a slot in it and slid in a thin plastic "stiffener" (section of plastic bottle) and a piece of sandpaper. Then, 2 small flathead screws (remember to countersink the holes for them) to pinch the slot shut and retain the plastic/sandpaper. The sandpaper overlaps the screw heads so you don't have to worry about scoring the cylinder walls.

Another thread on honing.

http://www.network54.com/Forum/79537/thread/1137046836/B21+saga+redux

JMJ

[BDS]

Hmm...you think that's always the way Cothran tubes come, or maybe did this one slip by?  I could contact him but I think we all know how long that can take.  I'll see if I can take a picture.

Ya ... pic would help and I don't know how he normally does his tubes but, if it was high quality, seamless SS tube, it should be reasonably smooth inside. The good stuff is used in aerospace and medical components in 1000's of applications, it should not need metal removal if it's the right size. Don't know what grade he may be using.

[Fronzdan]

Best I could get...tougher than I thought taking a pic of the inside of a tube.  I think this shows it pretty well.  Outside beautiful.  Inside...not so much.