For the sake of discussion, say someone wanted to scale up a model 700 action to handle the .338 Lapua Magnum with an adequate margin of safety.

Further, lets say he/she has turned a round bar of 17-7PH or 4140 to an appropriate diameter. How would one go about getting an accurate .750" diameter hole from one end to the other? Indicate between centers to an RGnCH*, face drill, bore and ream about 1/2 way through, flip the bar 180 degrees, and then repeat?

Thanks,

LD

PS I only have enough extra money from the loan for either a Kurt vise, or a KDK series 100 tool holder. Having a new mill and lathe is like having two demanding girlfriends simultaneously. No, it is harder. You can't lie to either the mill, or the lathe.

*Gn = gnat's

Use/make a gun drill bit would be the most accurate way I imagine.

I think you'd do OK to use a piece of oversize stock, drill the bulk out and then use a boring bar to finish to size, then turn to the OD on centers.

can you get a gun drill?...if so get one.

I wouldn't try to drill from each end as the reamer will have a very difficult time reaming the thru hole given the mismatch at the junction.

Drill all the way from one end and at the end of drilling relocate the bar concentric to the hole at the exit end and turn the barrel OD concentric to the ID.

Plan to drill about .725 and double ream to .740 and then again to .750

Once you start drilling you must be careful to keep the tools sharp as the precipitation hardening steels will work harden easily and it's a B**** to fix it when that happens.

I got a gun, I can get a drill .

This is too cool, more tools to buy.
You guys just made me smile.

Ooh, that reminds me, I will need to buy a shaper to do the bolt lug ways.

Guess we'll be eating peanut butter for another year or so, no big.

LD

A gun drill is a drill bit that has a single straight flute and is used for drilling long straight holes such as gun barrels . A typical helical drill tends to drill a helical hole !!

Jartman
Check out drill masters. I stopped there when on a trip back to see my wife's family in upstate NY. DMasters has a system where you can use lower pressure air fed coolant to deep hole drill using a standard engine lathe. Normally deep hole drilling requires 500-1000psi oil pressure and a very steady feed rate. If you get a hole through a chunk of material and it's not concentric with the outside, just turn it between centers, face both ends off square & turn it again. Not real fast but would work.
gunmaker

Here's another site
eldorado

Thanks guys,

The spray mist systems look like they will work with a regular lathe. It also looks like an acceptably smooth interior finish can be acheived ithout a world of gyrations.

LD

LD, If I were doing it, I would have the hole and raceways wire EDM. 17-4 would be a challange for your first one. I think that I would use 4140 or 1018 for my first. You could then case harden the 1018. I do have a 9' stick of 2.125 diameter of 17-4. Shipping might be rough.
Butch

I'll look at that also Butch. Is wire EDM something that can be done in a small shop, or is it a "send out" sort of deal?

That is a fairly hefty 17-4 paperweight.

It would make up into a splendid action for a shortened 50 BMG necked down to whatever.

LD

It would be done by a specialty shop. When you get to that stage of your project, contact me. Jerry Stiller of Stiller Precision Firearms is a friend and wire EDMS his raceways. It is much more cost effective to do this than to buy tooling to do it yourself. I think that wire EDM is by and far the most accurate way to achieve this.
Butch

quote:

Originally posted by butchlambert:
LD, If I were doing it, I would have the hole and raceways wire EDM.
Butch

Absolutely and there's just one little problem with that.....you must first drill a thru hole to allow the wire to feed thru to get started.

It's not really hard to put a 5/16 or so hole thru a piece of steel nine or so inches deep but it has to be there. Just drill on a mill and peck a good many times to clear chips.

I'd use a cobalt HSS drill if you can find it but standard HSS drills will do it as well. If you're drilling 17-4 go about 50 surface feet and keep the drill sharp as workhardening can be a problem.

DO NOT USE CARBIDE!!!!



After you get a couple inches deep try to drill one drill diameter per peck and lots of lube and eventually you'll get thru.

I would have to do it on a lathe as my Bridgeport doesn't have that much quill travel. You would have to locate a long drill or since Jerry does his that way, let him drill it also.
Butch

Butch - I was once in a quandry like you, over how to do the lugways in the receiver. I was travelling from San Diego to Denver and stopped in Prescott to see that grand old man, Fred Wells. He graciously showed me through his shop and explained the steps in action making. He didn't tell me how he cut the lug races until I asked. He said, "do you know what hook cutter is?" The light dawned immediately. You can do this in your lathe by locking the chuck and drawing the hook cutter through the bored receiver blank, raising the cutter each stroke until they're at depth, index the chuck 180 degrees and repeat. Cheaper than EDM and fairly easy, if you know how to make the cutter. In James V. Howe's (of Griffin & Howe) "The Modern Gunsmith (circa 1936), Chapter XI, page 157, he explains how to make one of theses cutters. I hope this might help.

I know this is an old thread but I thought I would add my two cents worth.

I used a set up similar to this several years ago. If you remove the idler gears on the lathe, lock the chuck, and attach a drive mechanism to the lead screw, you can actually use the lead screw to pull the reground broach or a hook cutter through the blank and save the labor. I reground a keyway broach to do mine with and attached it to the tool post. I did not index the chuck since my setup only required me to turn the cutter over and reposition the mandrel and tool post. Beats the heck out of doing it the hard way like I did for the first two back in the 80's.

if you wire emd, the pilot hole needs to br through .. it doesn't need to be VERY accurate, as it can and will be recut.

butch, you have that much travel...if your knee gibbs is tight ... drill 4", back out, raise knee, finish

I was told that if your turn the item to be drilled and not the drill itself (the reverse to how you do a short depth hole) it is more accurate as the items "self centres" itself.

not exactly about this topic but has always worked with others . lots of lube and patients .

I might be off base here, but if boring an action say ten inches long, why not just drill a 5/8 inch hole on the lathe (from each end if the bits too short) then set up a boring bar? A sharp cutter and a few passes and you should be good to go. Final ream if there is any taper to the hole from the long bar.

quote:

Originally posted by rick boggs:
not exactly about this topic but has always worked with others . lots of lube and patients .

Advice to aspiring proctologists really is off topic...

Oh, I guess you meant patience!

quote:

Originally posted by montea6b:

quote:

Originally posted by rick boggs:
not exactly about this topic but has always worked with others . lots of lube and patients .

Advice to aspiring proctologists really is off topic...

Oh, I guess you meant patience!

lol i did