Line boring jig?

[danski26]

Does anyone have photos and or a measured drawing for a line boring jig for a revolver cylinder? I have been trying to figure this process out, with little luck. I can't see how a reamer would not just follow the existing hole in the cylinder and i can't figure out how to bore the steps necessary for the chamber profile with a boring bar. How is "line boring" a revolver cylinder better than reaming with a piloted reamer? Or do you "line bore" undersized with a boring bar then finish with a piloted reamer?

[leftiye]

I've been playing with this idea for a while now. What I've come up with is a clamp that will lock the cylinder to the frame in place (in the hammer down, trigger back situation - as if fired - tie trigger back). This coupled with a large 90 degree angle plate, and fixtures to hold the clamp, and a drill guide should allow you to hold the revolver sans the barrel in position on a milling machine. The drill guide screws to the revolter in place of the barrel. The trick is that you use a boring bar with one cutting point unstead of a drill or a reamer. This will make a hole that is concentric to the barrel (drill guide). Then you can ream to chamber mouth diameter or use a chambering reamer as you wish.

You'll want to take out the cylinder and finish the hole all the way through though before doing anthing like chambering, or reaming. This can be done in a clamp that holds the cylinder in a milling machine vise, zero in on the center of the chamber mouth and finish the hole with a boring bar as was started in the frame. This works best if there are chambers already in the cylinder, and if you only make a moderate (as light as will cut well) cut with the boring bar, and when you have the holes positioned, then go on to finish cut the chambers. Sorry, no pictures (They're in mi Cabeza, and I'm not psychic).

[danski26]

Good description lefty. Basicly bore it first with the boring bar "single cutting point" then take out of the jig and finish with a piloted reamer after dialing it in. THAT makes sense. I have been playing around with making my jig out of a used barrel reamed and turned to dimension. I'll continue to work with that idea i think.....unless anyone has a better one?

[kywoodwrkr]

Brownells sells a DVD for the Ruger which desribes the align boring process and chambering.
561-000-010
I'm going to make a jig for the Ruger frame.
Using CMM (coordinate Measuring Machine) to get accurate plane and holes association.
Someone from one of the reamer companies sent me a 'steps and reamers needed' document. Can't remember who or where right now.
The DVD uses the frame the cylinder is to be homed in and a barrel bushing for alignment FWIW.

[danski26]

That sounds interesting. I am working on a Ruger Blackhawk. When you get your plans or even wfter you have made your jig I would love to take a look at it!

[McLintock]

That's probably Dave Manson Reamers who had the DVD. He sells a setup with a bushing that screws in the barrel hole, and then a .389" reamer is piloted in the bushing to ream the cylinder as it's held in place by the guns locking bolt. Then a chamber reamer with a 389" pilot is used to chamber the cylinder. NOt quite as good as a line boring job, but takes a lot less equipment, and for so-so shooters like me, it probably doesn't make much difference.
McLintock

[danski26]

How does a "line boring job" work better?

[McLintock]

It probably depends on how tight your cylinder lock up is, as if there's enough slop the reamer can just follow the existing hole. With line boring you negate this possibility. If you want and can take advantage of, thru your shooting abilities, 1" groups at say 50 yards then line boring is the way to go, but if you're doing good to do 2-3" groups at 25 yards, then the Manson setup will do. A $2000 Freedom Arms or Bowen or Clements custom will be line bored, but most shooters don't need it, especially for the price. JMHO
McLintock

[deltaenterprizes]

Steve Acker had a series of articles in "The Machinist's Workshop" Magazine that covered it step by step.

[leftiye]

McL - Thas why I decided to use a cylinder clamp with the trigger tied in place in fired position (cylinder bolt in full up position). Stops the cylinder from jumping around when bored. To be honest (though I respect Dave Manson a lot) I wouldn't even think of doing it without the clamp.

Dave, I guess you've got a CMM available. If not a centering scope and a DRO on a mill will do the same for you (in other words - it can be used to check layout and measure parts as well as find center of spindle shaft rotation).

[McLintock]

I just checked Kunhausen's book for the Ruger Single Actions, and he line bores essentially using the Manson method. But he locates the cylinder with a fitted bolt and then clamps the bolt in place for a positive lock up. They make oversize bolts for New Model Rugers but you'd probably have to make your own for an Old Model. I did a 44 Special conversion on an Old Model .357 and used the Manson Reamer, but made my own bushing and found a Reamer at a local tool shop, but used just a stock bolt. It turned out good, shot good and straight, without having to move the sights off center hardly at all, so it worked good enough for my handgun shooting abilities. Next time though, I'll lock the bolt a little tighter and maybe even make a better fitted one. Weld one up with a Mig welder and then fit it to the slots in the cylinder, just like you do with a 1911 barrel hood.
McLintock

[dominicfortune00]

IIRC there's a guy who specializes in reaming Ruger cylinders to have uniform throats.

He does this part time.

Don't remember his website.

[McLintock]

You're probably thinking of CAS6969, he reams throats, but that's a whole different thing from line boring, and a pretty uncomplicated thing to do, but it definitely helps many guns. All that does is match the cylinder throat diameter to the bullet and barrel bore size, and make them all the same, so there's no swaging of the bullet as it goes through the throat.
McLintock