Without CNC equipment (read: onlt hand operated mills and lathes), how do you machine the radius needed to mate with the barrel.

I am talking both what actually touches the rifle along the length of the rib, as well as what matches the barrel radius in a profile view.

-Spencer

I've never done this so it's just a wild idea but sometimes wildass ideas help so here goes.

Set the barrel behind the lathe so that you can trace it with an indicator and use it to trace the ID bore of a piece of steel about three inches in diameter. The idea is to bore the barrel countour full size in a large piece of steel and then cut the quarter rib from the bored piece. In this way you can have a near perfect fit and with some caution you can cut at least four quarter ribs from the large bored piece.

Maybe someone will have a better way to make just one out of a much smaller piece of steel.

A better way is to make a "pocket", fill with Devcon, insert barrel and action upside down into it and make yourself a "female" mold. Then you need a "finger" attached to the quill of your mill to follow the contour while your ball end mill works on the rib stock in the vise. Confused?

Jim

Not confused.
Timan

Jim, a tracer set up (what you described, or my translation) would work the nuts for getting the taper, but the big problem is getting the radius of the rib to match the radius on the barrel with its ever constantly changing radius along the taper. Can't be done like this with simple manual machines.

Duikerman has the best approach from a manual machine stand point. You don't need a tracing attachment, just the start and stop diameters and the distance between to set the taper(s). If your barrel has a standard shape you will have a straight section of about 1.2" ID and 1.5 to 3" long then a taper down to the barrel's acctual barrel taper, or do like Ruger did on the Frontier and skip this transition and just have the chamber area touching and the barrel taper touching and leave a "lightning cut" in the bewteen area. second pic down Much easier to do.

If you have a copy of Mark Strattons book he describes the process in there. You are basically using the mill as a duplictor. You do make a mold of the top of the action and barrel in epoxy on a jig. Adjacent to the finished jig is a slot where you clamp your material for the 1/4 rib.

You have a stylus that is set up with a collar around your milling machine and it traces the epoxy mould longitudinally while the cutter cuts the bottom of the material. You use a bungy cord to apply down pressure while the cutter travels along the 1/4 rib stock material. You make numerous passes and when done the buttom only needs some minor clean up to match the barrel contour.

I had the set up that Maurice Ottmar used to do this and it is now in the hands of Roger Kehr along with the Bridgeport mill.

Hopefully Mark can pop in here with some photos.

quote:

You make numerous passes

And there is were I dropped the ball. My reading comprehension isn't all there today, I re-read Jims post and for some reason my brain translated that as a simple pass up the center line of the rib. I've been running CNC's too long; they tend to suck the creativity of simple set ups out of my brain.

Hey Chic,

You know that I suck at posting photos. Pull out the CD that came with the book and look under the "Sights and Quarter Rib" icon. There must be 20 photos of the quarter rib fixture sitting in a Bridgeport type machine. If you would, please look through them and pick out a few that will show ShopCartRacing the quarter rib fixture.

To get the rough shape I was thinking of doing what duikerman said, to do it on the lathe and bore out the barrel shape in the middle of a piece of stock.

The makeshift pantograph sounds good, only instead of 3 dimensions, you are tracing on only the X and Z axis.

Also, like on a stock duplicator, you could take an initial pass with a larger tracing stylus and then go back again with one in the shape shape as your cutter.

I'd like to see pics of the setup.

-Spencer

Spencer,
I do not see how you would bore the inside in the case of an octagon barrel. You aint gonna do it on a lathe.

Here are the photos and the bunge cord down feed takes care of the third dimension and the repeated passes will do the rest. The cutter will go down with the taper as the power feed moves the stylus along the mold.

Here is the layout




A view of the mandrel above the bottom of the mold and the cutter above the stock material.




Following is the collar for the milling machine quill.

You have to mold the barrel into the fixture and let it set up. You then dress up the sides of the overflow material. The fixture is reusable as you just mill out the expoxy and have a clean slate.

The power feed will make one pass and then you move the table in a skosh and make another. I did mine at Mark's class in Trinidad and after molding the barrel into the fixture, cutting the bottom of the stock probably took 30 minutes tops. It has been quite a while since I did it and I wasnt trying to put a clock on it.

There are a number of other photos in his book and on the CD that goes with it to show the rest of the steps to shape the top and finish the rib.

Here is a rib in the final stages.

Thanks Chic...

Chic,
EXCELLENT!! thanks for posting!!
jeffe

Fantastic.

The idea of a bungee cord on the drill press handle is the ingenious part of the whole thing.

Now, how to mill the sloping lines of the nose of the rib as it tapers down toward the muzzle.

-Spencer

Chic, nice posting of Marks pics.

This is the system that Ted Blackburn showed us in a 1989 NRA Summer class.

I made one up and have used it ever since, lost track of how many 1/4 ribs I have done with it.
Also made new fixtures so I could machine a intergal front scope base, (or square bridge) wider than the 1/4 rib to bolt on the front ring. This was a trick from the late Fred Wells.

The tricks with this system are as follows.

You can only go down hill with the guide as the slop in the quill will only let you go ONE direction.

Rough out as much as possible, and then reset the depth of the cutter/guide and take .020" wide passes to machine the inside contour.
DO NOT ATTEMPT to totally finsh machine the edge of the rib, leave it slightly proud and final form it to the barrel. Otherwise you WILL have GAPS.

The rib stock I start with 1" square 12L14 and machine two sides the same to make my ribs, .500", .625", .700" wide depending on the barrel contour. This allows the steel to relax from the cold drawn strees on the SKIN.

Once you get used to this you can machine the inside contour of a rib to within about 98%. Mill the reciver end to length, set up drill and tap the two mounting hole and guide pins. Final shape the top of the 1/4 rib. Takes me about 6 hours to do a rib and fit the sights, and final shape and polish.

Or you can do it as Tom Burgess does with his Lathe, boring bar and tracer. Think about that one.

Jim Wisner
Custom Metalsmith

quote:

Originally posted by J Wisner:
Or you can do it as Tom Burgess does with his Lathe, boring bar and tracer. Think about that one.

That's actually how I contour everything from sight bases, scope mounts and ribs. With an adjustable boring bar mounted in the chuck, you can set any diameter you wish. The piece is mounted to the compound via a milling vise and then fed towards the chuck. The compound is perfect for cutting short, odd angles. Though I haven't used this for too long of pieces, it works great for the shorter stuff.

In reguards to milling the nose of the quarter rib, Niagara cutter company makes concave cutter with a 3/8 radius that gives you the proper geometry for this area. Cutter CCS-150 EDP18908. They also make a 1-inch radius cutter that brings the sides of the quarter rib to a ellipse and the concave radius cutter slpoes down to the nose of the rib.

Also as Jim Wisner was telling you always cut down hill, and when I come to a sharp edge in the mold, I help the stylus (Quill part) over the edge. I don't want to break off a sharpe edge. When I first started using this fixture, I used Devcon Liquid Steel in the mold. Very expensive stuff. I changed to JB Weld becauser it was almost as durable and cheaper.

I would like to take credit for this fixture, however I saw something simular in Maurice Ottmars shop in the early 90's. I also took a NRA class in 1993 at Susonville and Roger Green had a verison of this fixture.

quote:

Originally posted by 22WRF:
how does one mill the round portion of a barrel blank after one mills the flat portion for the quarter rib? Or is that an altogether different system.

Same machine, but you would use a rotary table to rotate the piece around a fixed cutter. Pretty simple and straight forward in practice, but time consuming.

22WRF,

Im glad you like the book. It's selling very well.

This set up is mainly for machining the mating surfaces between a quarter rib and barrel. With an integral rib, that suface is already there, you need to remove the outside geometry with the rib in place. I do a nice octagon barrel with a full length vent rib. Rifle Magazine ask to borrow it for a photo to place in the magazine. Maybe you'll see it some day.

As far as a vedio tape of me in action? I did one threading and chambering a few years ago for a friend. It wasn't for sale, but I think I'll pass on that type of project. I couldn't get used to the camera watching every move. I think the best I can do is another book some time down the line. I've stopped teaching at Trinidad, that was fun for me, something different than I usually do and I got to meet a lot of great people. It just got to be a hassle.

What is the title of Mark Stratton's book and where is it available?

Ted Blackburn also had a few things that were neat. He never said if he came up with the system, just that this was his fixture and this is how he had machined 1/4 ribs for quite some time.

His block for the impression was set up with a pivet point in the middle and clamps on both ends. This way he could adjust the vee cutout so he could machine a vee for a new impression. Also you can level the impression so you have less metal to remove from the top surface of the rib.

Since the clamp for the rib material has one solid jaw. He then made his quill clamp so he had three offset holes for his stlyus, to match the offset of the differnet rib material, .500, .625, .700 wide.

Marks clamp has an adjustable offset for the differnet width ribs.

You have to remember that Marks photos are of a cleaned up stopped cutter. This set up makes LOTS OF CHIPS. Also the cutter is about three inches from the impression. A chip guard is NEEDED. You also have to take care so as not to drag a chip under the stylus and scratch the impression.

I use 12L14 for the rib material, this way I can use a 3/8" four flute carbide end mill at 1100 - 1300 rpm, the stylus is .380 in diameter.

Oh yes you can machine a 1/4 rib to fit back onto a octagon barrel with this system. You have to be very careful in matching the cutter to the stylus shape. And then the change up from the flared octagon to round breech is a bear and requires a lot of hand fitting. So far I only had to do one this way, because the barrel blank was not large enough to machine an intergal rib.

Jim Wisner
Custom Metalsmith