cutting off the back end of a cast bullet with a lathe.

[Whiterabbit]

hi guys,

I've been looking into lightweight gascheck 45 cal designs for 460 S&W. Looks like plenty of options from accurate molds, and that's where I'll be going.

BUT.

Molds are of course pricey, and I don't know what bullet head style would work best for my gun for accuracy. I'd love testers but few people on this forum who have these molds (if any) talk about them.

SO! I was thinking about making my own testers to see if the option is viable. I've got the LEE mold. I was thinking I could cast a few up then chuck them in the lathe point first then face the back. cut it right down to an open grease groove to clip the gas check onto and see if I can't shorten/lighten up some bullets this way.

I see some folks experimented this way hollow pointing some bullets. Anyone ever try shortening the backs? Anyone see why this wouldn't work for testers?

---------------

Plan B was to buy a 5 cavity mold with a different bullet in each cavity to just try them all. The cost is something like $180 for a mold like that from accurate. Not bad, but if I can make a dozen testers from the lee bullets by myself...

[Crawdaddy]

yup. it works fine. I have a Smithy and I do this for my 450 MArlin and 458 WM loads. I get good results with the 450 Marlin. The 458 I have not gotten acceptable results yet but I feel it is a powder/case capacity issue.

I have been reading about fillers and will try it next.

[williamwaco]

hi guys,

I've been looking into lightweight gascheck 45 cal designs for 460 S&W.

I've got the LEE mold. I was thinking I could cast a few up then chuck them in the lathe point first then face the back. cut it right down to an open grease groove to clip the gas check onto and see if I can't shorten/lighten up some bullets this way.

Anyone ever try shortening the backs?




I have done approximately the opposite. I wanted a light weight bullet for my .38-55.

I sent a 265 gr Lyman mold to Erik at

http://www.hollowpointmold.com/

He cut off the gas check, the bottom drive band and the first grease groove. This resulted in the second driving band becoming the base band of a plain base bullet of 214 grains. At 1775 fps, it is the most accurate mold I currently own in that caliber.


The answer is that It is possible to make your own designs and if you are lucky you might even get improved performance.

[W.R.Buchanan]

No reason why you couldn't turn a gas check shank on your bullet instead of facing it down to a grease groove.

Lead turns just fine.

Randy

[Whiterabbit]

I have done approximately the opposite. I wanted a light weight bullet for my .38-55.

I sent a 265 gr Lyman mold to Erik at

http://www.hollowpointmold.com/

He cut off the gas check, the bottom drive band and the first grease groove. This resulted in the second driving band becoming the base band of a plain base bullet of 214 grains. At 1775 fps, it is the most accurate mold I currently own in that caliber.


The answer is that It is possible to make your own designs and if you are lucky you might even get improved performance.


Now THAT is interesting, too. You think I'd have much luck milling a LEE 300 grain mold down in the same way? is the sprue surface a precision, precision, precision surface, or would a GREAT drill press (or chinese mill) level of accuarcy do it?

[JSnover]

As long as it's square and you can cut a good finish... slight tool marks are ok. If they're not too deep they can act as vent lines. If they look to deep and can't be cleaned up with your mill, you can stone them. The sprue plate hole alignment is not critical, but try to get it as near as you can. A drill press would be a bad substitute but a chinese mill will work.

[leftiye]

Or chuck the mold you have in your lathe and face it off. Lead is soft - your lathe chuck jaws will dig into it and mess up your boolits. But if not tight enough the tool will dig in and pull the boolit out of the jaws - cut carefully. Collets seem the better idea for turning lead. Yeah, someone did have that idea before. I turn off the base bands on boolits that I want to put gas checks on. Hollow points, modify the mold (drill a hole, make a nose punch, drill and tap a nose punch retaining screw - don't put a wood handle on it).

[para45lda]

I've got some 340 grn. Plain bases you can try from an Accurate mould.

[mdi]

FWIW I was able to take about .050" off the bottom of a lee mold I have by draw filing. I clamped the mold in a vise, used a sharp single cut file and carefully draw filed it. I turned the mold often to evenly remove stock and occationally trued up the surface by using fine sandpaper and a pane of glass. I was able to keep the mold square and now it casts bullets about as good as any mold I have. I was taking off a bevel base from a TC bullet, but wound up drilling the remainder of the bevel off...

[Crawdaddy]

Now THAT is interesting, too. You think I'd have much luck milling a LEE 300 grain mold down in the same way? is the sprue surface a precision, precision, precision surface, or would a GREAT drill press (or chinese mill) level of accuarcy do it?


If I am understanding this correctly you are going to lose the ability to put a gas check on, which I believe you wanted to keep.

There again, if I am reading this right you could still take it to the bottom grease groove where you could attach your gas check to.

[clintsfolly]

Maybe try the Boolit Exchange in the swap &sell forum. Post what you want and some one may have then. Clint

[Whiterabbit]

Or chuck the mold you have in your lathe and face it off..

I have never performed a lathe operation on square stock. But that is an interesting concept for sure.

How do you chuck square stock in a 3 jaw chuck and ensure the back is square?

Would it be better to chuck an end mill into the lathe and try to clamp the mold into the tool holder? Have you ever done something like that? Actually, I see workpiece height being a problem going with this method. Maybe best to chuck the mold into the 3-jaw chuck. but how to do that?

[leftiye]

Errrr.... Use a 4 jaw? Or put one jaw of a three jaw in the middle of the outside of one mold half and one on each corner of the other mold half maybe? Not centered? Doesn't have to be. As was said, turn slowly. Tap it against the face of the chuck with a dead blow hammer to get the bottom flat on the chuck face (if your through hole isn't too big).

[williamwaco]

Now THAT is interesting, too. You think I'd have much luck milling a LEE 300 grain mold down in the same way?

is the sprue surface a precision, precision, precision surface,

or would a GREAT drill press (or chinese mill) level of accuarcy do it?



Rabbit!

I am not a machinist. I am totally unqualified to answer questions about tools. I do know my mold was modified by a milling machine.

That said, remember, mine was a Lyman mold. Surely your comment about precision was made in jest?

I can tell you that the operation significantly improved the precision of my mold.

[bearcove]

Grease groove may not be right dia for gascheck.

[Twmaster]

As said the mold would not have to be centered. Just perpendicular to the spindle. I prefer cutting flat surfaces like that on my lathe rather than my small milling machine. If I understand what you want to do.

Otherwise I have turned boolets in my lathe while held in an ER collet chuck to trim them down for length or lighten them. (or both)

[Mk42gunner]

I don't see why you couldn't modify a few boolits fairly easily with a lathe. One of the older mould making companies used to supply 1/2" slugs of either lead or linotype so customers could verify their design before cutting cherries, or so I have read.

Robert

[Whiterabbit]

As said the mold would not have to be centered. Just perpendicular to the spindle. I prefer cutting flat surfaces like that on my lathe rather than my small milling machine. If I understand what you want to do.

Otherwise I have turned boolets in my lathe while held in an ER collet chuck to trim them down for length or lighten them. (or both)

oh GOOD. I haven't had the chance to talk to a real machinist yet. I have a question for you.

So I'm setting lathe speed to face stock, and get confused very quickly. If I have a piece of large stock, the actual cut speed is much faster than small stock at the same RPM.

But no matter WHAT I set the RPM speed to, when I hit the center of the material I'm facing, the effective cut speed is zero. What do you do about that? brass seemed to be no problem, but stainless was a bastard to face, at best. $10 says we can put a known flat surface on the face of my new punch and find it in a perfect arc shape.

[Twmaster]

I'm not a machinist. I did stay at a Holiday Inn Express last night though... :D

If you are ending with a nub in the middle your tool is not dead on center. Unless I am not understanding your post.

And yea, stainless is a bugger to turn. Hates it. Hates I do. The only answer I have is very very sharp tooling with a small nose radius and be dead on center.

[Whiterabbit]

You might be understanding, but let me explain more. MY understanding (cause I am seriously not a machinist, just a tinkerer who stumbled on a lathe deal he could NOT refuse) is that my workpiece needs to move at a certain piece past the cutter. NOT RPM speed, but actual speed the piece passes the cutter. So, at a constant RPM, a 2" diameter aluminum rod will be moving MUCH faster than a 1/2" diameter rod. At least, right where the cutter is!

So for so good, for running the cutter across the length of the workpiece.

But when facing it, the actual metal speed changes. At the edge, the piece is moving along nice and fast. Near the center, the workpiece starts to slow down. At dead nuts center (absolutely I shim the tool to center!) I can spin that lathe at 1,000,000 rpm but that workpiece is not moving at ALL with respect to the cutter!

You know. At the instantaneous center.

So, when I was goofing around with a scrap of brass, it seemed like a non-issue. turning nice and slow, the finish was great, facing went without a hitch. But with stainless, I had to up the speed much, much higher. And it was clear the cutter was experiencing much more resistance the closer I got to the middle of the piece. Enough, I believe, to warp my facing from flat to a bow shape.

That got me thinking, if I have to calculate an ideal RPM based on the size of the material to get a proper material cutting speed, how do machinists properly set up facing cuts where the workpiece spins at different effective cutting speeds across the face diameter?

[JIMinPHX]

White Rabbit,
Yes, surface speed decreases as diameter decreases at a constant RPM.
Yes, there is a specific surface speed at which a given tool will cut best in a given material.
Yes, surface speed is zero at dead center, regardless of RPM.

In a CNC machine, you can program CSS & the RPM will increase as a facing cut approaches center. In a manual machine, you don't have that option, so you need to make a few comprises. Most people take off the heavy material with OD cuts & leave just a little bit left for finish, then take a gentle facing cut at a high RPM if they need to cut all the way to center. When taking a lite cut, you can get away with cheating a little bit on your maximum surface speed.

As others have said, having your tool close to exactly on center is important if you want to avoid the nub in the middle of the face. I usually try to set my OD & facing tools about .005" below center. Below center gives you a nub. Above center bludgeons the material instead of cutting it. A .010" diameter nub will generally just break off as the tool pushes up against it.

Stainless is a tough material to cut if you don't do everything exactly right. It is famous for eating up tooling because most people don't cut it correctly. Most grades of stainless like slow surface speed, modest feed rate, rigid tooling set ups with positive geometry on the cutting edge, sharp tools & LOTS of coolant. If you cheat on any of those with stainless, then you will generate a lot of heat & probably ruin your cutting tool. A lot of people cut stainless with Cobalt tooling rather than HSS. Cobalt lasts longer in stainless, not because it's harder, but because it takes heat better. Cobalt is actually a little softer than most types of HSS that are out there.

Geargnasher has managed to reduce the length of some 6.5mm boolits by hand filing the mold blocks shorter. He got good results, but it takes a steady hand & a bit of talent to do it successfully that way. I've always shortened my blocks on a mill or a lathe. Either one will work fine. I normally locate on the top face & breeze cut the bottom to be sure that it is true to the top before flipping the blocks over & taking the cut on the top side. Most 2-cav Lee molds that I have worked with have bottoms that are not true & often not even aligned flat from one block to the other.

[Whiterabbit]

White Rabbit,

Stainless is a tough material to cut if you don't do everything exactly right. It is famous for eating up tooling because most people don't cut it correctly. Most grades of stainless like slow surface speed, rigid tooling set ups with positive geometry on the cutting edge, sharp tools & LOTS of coolant. If you cheat on any of those with stainless, then you will generate a lot of heat & probably ruin your cutting tool.

Ah, most people. That's me! I don't have a cooling rig on my lathe. You'd suggest then I cease and desist any future attempts at cutting stainless?

[Whiterabbit]

And while I've got your attention, I appreciate your suggesting that stainless prefers relatively slow surface speed. Can you tell me the qualitative relative speed ideal for turning brass and aluminum also? (just the cheap hobby over-the-counter stuff, I'm not cutting aircraft aluminum or anything.)

[JIMinPHX]

If you don't have a coolant rig & you need to cut stainless, then at least spray something on it to take away the heat. WD-40 is better than nothing. I've even used a garden hose & sprayed water on stainless when drilling it out in the field. the garden hose actually worked better than I had expected.

If you are just spraying it with a can of oil or something like that & it starts to smoke, slow down or wait a little while before continuing the cut so that the tool & the material have time to cool a little. That's about the most basic, stone-age advice I can give on the subject.

[Twmaster]

The truth is that most 'hobby' aluminum is harder to cut than 'aircraft' grade. Most hobby aluminum is made of soft nasty alloy and more tears than cuts leaving a foul looking finish.

I've just realized that we've hijacked this thread from the OP. It's likely a good idea if White Rabbit were to start a new thread in the appropriate forum...

[JIMinPHX]

Brass & aluminum can both be run a lot faster. Aluminum likes positive geometry on the cutting edge, just like stainless does, but you can move a lot faster & you can use much heavier feed rates. Brass & other copper alloys don't do well with heavy positive clearance angles under the cutting edge. They have a tendency to suck the tool into the work & cause a catastrophe. For brass, keep the clearance angles slight.

"Hobby" aluminum can be anything. Some alloys of aluminum, like the 1000 series stuff used in electrical applications, does not cut well at all. It turns to goo & sticks to your tooling whenever it gets a chance to do so. The aircraft alloys, like 6061, 2024, & 7075 cut like a dream compared to it. 6061 is a great place to start. It's worth buying some. 12L14 (leadloy) steel is another material that cuts easily on a lathe & is a good material for beginners. 360 brass would be great too if it weren't over $5/lb these days.

[JIMinPHX]

Twmaster is right.

I'm sorry for feeding the hijack.

White Rabbit,
If you start a new thread, PM me & I'll follow you over there.

To reiterate the information that I originally intended to post that was relevant to the OP (in hopes of steering back from the unintentional hijack) -
Geargnasher has managed to reduce the length of some 6.5mm boolits by hand filing the mold blocks shorter. He got good results, but it takes a steady hand & a bit of talent to do it successfully that way. I've always shortened my blocks on a mill or a lathe. Either one will work fine. I normally locate on the top face & breeze cut the bottom to be sure that it is true to the top before flipping the blocks over & taking the cut on the top side. Most 2-cav Lee molds that I have worked with have bottoms that are not true & often not even aligned flat from one block to the other.

[Whiterabbit]

I normally locate on the top face & breeze cut the bottom to be sure that it is true to the top before flipping the blocks over & taking the cut on the top side. Most 2-cav Lee molds that I have worked with have bottoms that are not true & often not even aligned flat from one block to the other.

This sounds like very sound advice. Thank you for this.