Lacking any of the highly artistic skills I see featured in this forum, I decided to go the "easy route" and build a quarter rib mating fixture as described in Mark Stratton's book. I started with some Starrett low-carbon flat ground stock and some cheap cast iron v-blocks. I also picked up some Al plate and round stock that I'll use to make the quill collar and stylus holder.



Machining the base plate was the most time consuming part of this project, especially the v-blocks. It's not much fun machining on cast iron. The rest of the pieces were fairly straightforward.




I used a 3/4" scrap of 6160 plate for the quill collar. I mounted it on the rotary table and just followed the plans. Here's a photo of the quill collar after being parted off, along with some of the larger pieces left over from the milling operation.



Now for the moment of truth... Ahhh, it actually fits!



Drilled and tapped the through-hole on the clamping leg, plus added a radius to the corners. Can't wait to see if this fixture works as well as it looks!



The stylus holder and end cap mates perfectly to the collar. I milled out a 1/2" round pocket on the end of the stylus and glued a .500" ball bearing inside. Both the ball bearing and stylus are made of stainless.




Rather than use up 50 tubes of JB Weld on my first layer, I filled the inside of the containment area with Bondo, leaving about .125" clearance for the JB Weld to form the barrel impression. The v-blocks can be easily removed to make clean-up along the corners much easier.



Can't wait to give this fixture a try.

-- ale

Hey Bud,
You want to do my quarter rib first to make sure of your setup? Just kidding Brian, you're doing well. You are going to have a real nice 10/22!
Butch

Brian

Very nice work and photos.

What steps did you go through to prepare the base plate? Did you machine the bottom to make it easy to use with the mill vise?

What steps did you take to make the V blocks and rib clamp parallel to the base and with each other?

How did you determine how much to machine off the bottom of the V blocks?

Craftsman --

You are correct in recognizing the importance of keeping everything square when building this fixture. Before starting I used a dial indicator to square the vise with the table. Then I squared up the sides of the base plate in the vise. I didn't machine the top or bottom since I assume "flat ground stock" means that it is ground flat. I didn't measure it so I could be wrong. I can always come back with a fly cutter for a clean-up pass.

I machined the v-blocks using a 1" Valenite end mill with carbide inserts. I used a water soluble cutting fluid through a mist system. The constant stream of air plus cutting fluid really helped with machining the cast iron but it was a real mess, too. The only caveat when using this cutting fluid/mist system is that you need to thoroughly clean up all the chips (and fluid) when you're done, otherwise you'll have rust everywhere.

As far as the height of the v-blocks are concerned, I just milled them down as far as I could while leaving enough material to drill and tap for the attachment screws on the bottom. The lower the profile the better but it's not critical. Filling the containment area with Bondo probably saved me $100 in JB Weld. The holes for the v-blocks and vise jaws were all drilled and tapped using one setup so I'm pretty sure everything is parallel with each other.

Butch, I'd be happy to machine a quarter rib for you but you probably have one of those custom Anderson half octagon barrels and I don't have a clue as how to use this fixture for something as complicated as that yet. Better let me practice on the .22 standard contour Shilen barrels first.

-- Brian/ale

Well done Brain! Please keep us up to date on the work in progress. I enjoy seeing these type photos on AR most of all.

I also used bondo for my jig. I also made it removeable so I can just pull it, and put it in the milling machine to remove the old mold material. The only advantage I can see to this is it keeps your cutter away from your v blocks.

Shane Thompson

This type of system to machine ribs has been around for a long time.

In 1989 Ted Blackburn had his well used milling fixture like this, at Lassen CC for one of the NRA one week classes. He has a vee block made from Alum, that has a clamp on each end with a small vee cross wise in the bottom middle with a 1/4" dowel pin in two small vees to act as the pivot, so he can rock his vee block to level the barrel impression.

To make you think a little, Tom Burgess told us in 1990, that he uses his lathe, a 4 jaw chuck and a tracing attachment on his lathe with a boring tool to machine his ribs to match his barrels.

Machining ribs to fit Octagon barrels is some what differnt that a round barrel, but the idea is the same, match your stlyus to the endmill, and do the change from round to octagon by hand.

James Wisner
Custom Metalsmith