My small lathe project

[Pistolero]

Brad's 'Lathey day' post made me think of this project that I just finished.

Working on .38 Spl wadcutter loading for S&W Model 14 and 15 6" target that will produce max
possible accuracy. Starting with Remington swaged HBWCs, since they have a reputation of being
extremely accurate, at least potentially so. Will use my H&G 50 mold to run a comparison
of my own bullets, solid based. Rems are a baseline, and way to learn about HBWCs.
I have some wadcutter brass, and have verified the internal differences with pin gages.
Next I wanted to see if expanding the brass full depth for the bullet would help accuracy, since
the original expander is only about half the length of the bullet and no question that the case
will size down the hollow rear portion to fit the brass, since the alloy is soft and the base is
very deeply hollowed out. Maybe the hollow base blows out to fit the cylinder, even if the
original diam is sized down by the brass - or maybe not. Mr. Target knows the answers.

So - I made a deep expander pin, with the tip at .3580 diam, which pin gages to .357 ID after
expanding WC brass, giving a .001-.002 interference fit on the bullet WITH the thick lube.

Here is a pic of my lathe project, I think it turned out well.

 

[Brad]

What did you use for material? I've been using a bunch of 1144 and it works well.

A good knurl is on my future wish list, the one I got with the lathe is pretty sorry.

Looks pretty good. Now to load some ammo and see how it works!

 

[L1A1Rocker]

Very nice. I had to make one of those for my 300blk a few years ago.

 

[Brad]

I bet Ian can't knurl on his drill press!

 

[Pistolero]

Thanks.

Hell, I can barely knurl on my lathe! My expert has warned me that knurling
tool on one side is real hard on the lathe bearings. He has some sort of an
clamping type of knurling head, for want of a better term, and better memory
when he showed it to me some years ago.

The knurling is the first I have ever done, the knurl was too low, only cut on one
side...... works for gripping, doesn't look as nice, but I'll do better next time. Polished the
tip with 400 grit wet or dry in the lathe, easy to get it to .0001 accy that way.

Dunno on the metal..... steel. I had a chunk of 3/4 round stock in the pile of stuff, and
everything else was too small. I plan on picking up a bundle of 4140 round in various diams
about 24" of each next time I go to my supplier. I have machined it and it is very nice indeed,
seem to get a better surface finish with my lack of skills and home ground hi-speed steel
cutters. The threads don't look as nice as I would like, single pointing is rougher than a die
in my shop, at least. Still learning......

I made a choke tube for a Cutts Compensator a while back from 4140 and was very pleased
with the thread quality and overall machinability and surface finish that I could achieve with
my limited skill set.

Bill

 

[Brad]

I bought a 7/8-14 die just to clean up threads a bit. It cuts far cleaner than single post cutting, at least so far.
I have used a bit of annealed 4140 and it was pretty nice too. I will say that even O1 isn't bad and that stuff really polishes up nice. Made a Star die from it.

I ordered a set of brass barrel laps today for opening up holes in sizers. Hopefully they will be a bit faster than paper and a split rod.

 

[Pistolero]

Here is the general type of knurling tool that he strongly recommended to protect
the lathe head bearings.

http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=950782&PMAKA=505-4518

As usual, you can spend a LOT more. Look at the $650 ones.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=216&PARTPG=INLMK3&PMITEM=505-4515

Probably need a 9/16-18 die for this stuff, do final cleanup.

Brass lap is much more circular and parallel sided in the end, another
tool and die maker friend (make dies for Sierra!) says use a lap for doing
revolver cyl throat opening. I have two friends who make a good living with their
knowledge, and I sure listen when they tell me something about metal
working.

Bill

 

[Brad]

What's another die. Or twenty. They are good for cleaning up threads and they do leave them nice and clean.

Knurling is something I need to play around with.

 

[Pistolero]

Knurling makes nice looking "stuff" and all reloading dies have it on them, so I guess
the scissors type knurling device is not on my list of "tooling to buy"...... stretching off
to the end of my bank account.

 

[smokeywolf]

If you want a really pretty knurl you use a cutter, not a former. Cutters often run $400 to $500 or more. I don't have one. Always had a more immediate need for other tools.
Have 2 or 3 formers, each with several different wheels. Forming good clean knurls can be a bit tricky. Right feed, right pressure, lots and lots of oil or coolant to wash the swarf away.

 

[Ian]

I bet Ian can't knurl on his drill press!

Nice work, Bill, knurling and all. I did that once with my drill press using that very thread pitch....on an alloy steel bolt. It fit the hole in the top of an old Bonanza .44 Magnum seating die just dandy. The hex head is easy to grab, too, though it looks a mite unsophisticated. My only issue was that even with R-P wadcutter brass, it made a bulge in the cases. The solution ended up being to crimp in the first groove and leave the button nose and first band exposed. I've always thought that one of the reasons for the legendary short-range accuracy of the .38 Wadcutter was the small case capacity resulting in the ultimate burn consistency. That and the extra bullet tension.

 

[Pistolero]

Not sure what to credit it to. I have full power loads with .357 cast that have been more accurate than the best
I have ever shot with a .38 WC, so at this time the legendary accuracy of the .38 WC is still a legend for
me personally. Two Model 14s and a target 6" model 15 and still looking for a consistent 1" group, not
there yet, although the eyes are still a bit of a question mark.

With the trifocal and a Hawkeye "pinhole" I am seeing the targets and sights well now at 25 yds, so I
THINK I am back where I am testing the ammo, not the shooter - well, the shooter is always the key
weak point, but for the last year or two, the shooter disability has overridden any variation in ammo
performance, making testing pointless. Starting to look like I am past that point now, so trying
to figure out what makes a swaged HBWC shoot the most accurately in my target S&Ws.

 

[IllinoisCoyoteHunter]

Looks great! I am using the cheap clamp knurler from Shars and it works fine. Comes with 3 sets of wheels too! I think I gave $40 for it.

Threads look good too. I have had good luck finishing the threads by advancing the cross slide instead of the compound. It finishes the threads so the cutter cuts and cleans up both sides of the "v" instead of just the advancing side. I use this method for the last couple thousandths.

 

[Pistolero]

Thanks. Will look at the Shars knurling tool. I have cut threads both ways, with 30 deg
compound and with the crossfeed, straight in. Can't really see much difference, but
I'm sure that the experts know which is better.... maybe. Books say us the compound
at 30 deg.

Bill

 

[smokeywolf]

I have had good luck finishing the threads by advancing the cross slide instead of the compound. It finishes the threads so the cutter cuts and cleans up both sides of the "v" instead of just the advancing side. I use this method for the last couple thousandths.

Set your compound at 29-1/2 degrees and you'll get cleanup on the right side of your V without the risk associated with advancing your single-point tool with your cross-slide.

 

[Pistolero]

Sorry to be so dense, but what is difference in the risk associated with using the cross slide?

Seems like they are both pretty equivalent, the main risk is being an idiot and
forgetting to retract the cross slide before running the cutter back to the right
for another pass. Same risk of that either way, it would seem.

I really do appreciate your taking the time to explain this. So much of machining
is doing the best technique to get better results, and save time, increase safety
and decrease the opportunities for dumb mistakes ruining the work or worse.

I have used a friend's Hardinge lathe for threading and boy that sure makes things
nice. Both the auto feed stop and the tool retract capability are huge reductions
in risk of wrecking the part and just plain old convenient. Besides being so incredibly
rigid, too. Not ready to spend $20,000 on a lathe, though.

Bill

 

[Brad]

Ok, my understanding is this. Run at 29.5 degrees. Using the compound to advance all cutting is on me edge of the tool, the back edge doesn't cut at all.
At 30 degrees the back edge drags on surface.
Using the cross feed you are always cutting on both sides.

I run at 29-29.5 degrees or as close as I can get it. I advance with compound until the last tiny pass or so then I use the cross feed for the final .001 or so.

What I have found is that getting close on the lathe is nice but clean up with a die and get even nicer threads.

 

[smokeywolf]

Bill, you are very lucky to have a friend who will let you use his Hardinge. There is no other lathe that is as uniquely capable of making single-pointing as easy as does the Hardinge HLV. Another example of the compound being intended for single-pointing is the fact that Hardinge put the quick retract lever on the compound.


Brad you are absolutely right on using a die to take the last couple of thousandths. Hint: if you're threading up to a shoulder and because of the lead on the die it won't finish the last 1/4 to 1/2 thread, flip your die around and run it up to the shoulder. Less lead on the back side of the die.


When your compound is set to 29-1/2* (that is 29-1/2 degrees off perpendicular to the workpiece) it causes the right cutting edge of your single-point tool to take a very light cut, equivalent to what's known as a skin-cut, on the right side of thread. Set at 30-1/2 degrees and you're tool won't touch the right side.

Dialing in with the compound is considered the safer way to single-point threads because when dialing in one graduation (.001) with the cross-slide (if your micrometer collar is a 1-for-1 (one graduation on micrometer collar = .001 off total dia. of workpiece)) you're taking nearly a half thousandths off each side of your "V". When dialing in with the compound, due to your compound being set at near the angle of the right side of your "V", you're only taking a half thousandths off the left side of your "V" while taking almost nothing off the right.

In a nutshell, you have more control over your depth of cut, you're taking about half the amount of material with each cut, the trailing edge of your single point tool is weaker than the the leading edge, all these factors combine to reduce your risk of chipping the point off your very carefully ground single-point tool.
Also keep in mind, because of the direction of cutting forces, the trailing edge of the tool has less mass supporting it than the leading edge.

Although some processes and procedures may seem minor or yielding little advantage, in machining you're taught to use every little trick available to minimize having struggle with the part and maximize the accuracy and finish of the part.

 

[Pistolero]

Thank you for the explanation. I'll switch to doing it the right way and set the compound to
29.5 deg. Never thought about chipping the tool, I guess that the relatively few threads that
I have cut means that I haven't yet experienced this. Perfectly willing to avoid making every
single possible error on my own though!

Bill

 

[IllinoisCoyoteHunter]

Thanks for the explanation. I always thought that the leading edge of the cutting tool had less mass for support because of taking into account the helix angle and appropriately grinding that into the tool?