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Old May 9, 2017, 12:55 AM   #12
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Join Date: November 13, 2006
Posts: 6,585
John Moses Browning did amazing things in his little Utah shop,with not much.
I don't know about today,but a decade ago,Holland And Holland would go about machining a receiver by simply hogging steel away with a drill press,then carving steel with chisels. Very low tech,high skill processes. No CNC,no EDM. Regardless the mystique,IMO,a CNC machined part accurate to.001 is as good as any part filed to .001. The difference is the filed part may cost $60 to make,while the CNC part is $3 And 30 years from now,Old Joe the File guy is dead. The CNC program can still make parts to print.

Some archaic machinery does amazing things,and parts are designed to take advantage of the machines. Many shapes very difficult for rotating cutters are a piece of cake on a broach. Many folks are familiar with a keyway broach. Using a slotted bushing,they are pressed through a pulley or gear to cut a keyway.
Broaches cut far more complex shapes than keyways. Like splines. Or AR barrel extensions.

I ran a large American Broach machine. Part of it was below the floor,and an 8 in dia hydraulic ram drew the broaches through the parts. Amazing 1950's machine that was a moneymaker!

I had reason to cut some falling block bolt raceways in some Hepburn receiver castings.
I built a fixture on a cheap cast angle plate to hold the receiver and simultaneously guide common keyway broaches to cut the bolt raceways. Beauty!

Many complex to mill gun parts were made on a shaper. These use something like a lathe bit to cut. The cutter is simply driven on a long,straight like cut. It makes one chip.This machine is also called a "planer/shaper".

The shape of the part may be a master pattern,a template,or layout lines on the workpiece.

The operator turns the machine handles to move the workpiece so this cutter is generally "eyeballed" to the layout line or template.

I adapted the idea to making a long bar of rolling block rotary extractors . I used a end mill on a Briddgeport,conventionally. But I used an original extractorattached to the end of the bar for a template.The hole was already bored. The extractor was screwed to a brass plug in the hole.A bar of 8620 steel was held horizontal in the chuck o f a Yuasa Accu-Dex rotary fixture,and aligned with the Y axis.
So,Id rotate theAccu-dex a few degrees,eyeball the corner of the endmill to the edge of the original extractor,and make a cut. I ended up with an 8 in bar of extractor silouettes,cut around the pivot pin hole.

Next,that was stood vertical in a Vee-Block,and a large slotting saw was used to slice off the extractors. The trick! Slice most of the way through at finished thickness,but then offset the cutter in the Z axis so the saw cutter kerf leaves steel for the extractor hook!

Gang drills and box fixtures are old school. Say you have a lever action receiver. You lod it inside a box fixture. Features inside the fixture,a table,a fence,and astop,locate the part.

The top plate of the fixture has hardened drill bushings installed in holes precisely located . The "gang Drill" is just a table with a row of drill press heads. A seies of drills,reamers,and taps are then run through the drill bushings,precisely locating the holes in the workpiece.

Folks figure out how to use what they have

Bill DeShivs: Agreed! Look at a flintlock lockwork from the 1700's!

Last edited by HiBC; May 9, 2017 at 01:06 AM.
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