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I have an aluminum mold that casts a 100gn SWC with a nominal dia of 359. I would like to open this mold up for use in reloading a Makarov. I've thought about casting a hard bullet, inserting a shaft into the bullet, put some valve lapping compound on on the bullet and honing out the cavity.
As anyone tried this? Is .005 too much to lap?
I have done aluminum molds, Dont use valve lapping compound, It it cut fast and leaves heavy rough finish and ruins a mold, Get some very fine grit and go slowly. .005 in my option is alot for aluminum as you can get it out of round and rough finish, If you have a aluminum mold that sticks , lap it a few turns and the bullet will jump out of it. Maybe someone else can help you more on going to .005, Smokemjoe
I've done just about exactly what you describe with a 38-55. It worked just fine and no, .005 isn't too much. You do need, however, to cast a new lapping bullet every now and then as you progress to the larger size to keep from wallowing out the cavity with the original (now) smaller bullet. I used a screw into the base of the bullet and chucked it up in a cordless drill. One of the problems is that it is hard to get the screw in the exact center of the base.
By the way, I shot the final resulting bullets as cast and the results were good.
Phil
I've never done it myself but intend to some day. I was going to suggest doing what 22cf45 already said. It sounds reasonable.
I'm opening up a 120 grain .30 cal mold right now to .315 by the method 22cf45 outlines (for CZ52). I'm using diamond lapping compound (because I have it). Could use a coarser grade, say 600 grit -mine's 1200 grit. Ditto on opening the cavity(ies) up some, then casting a larger boolit and going again. I'm getting no out-of-round by this process, but be careful, lap by hand until boolit rotates easily before spinning in drill. Do one or two boolits, then cast with the alloy you are going to use and see what you've accomplished, and so on.
I also center popped the mold half on one block on all four corners, not as cheesey as you might think. Works good. You have to keep casting, and popping until the feeler gauge says you have the gap you want, no more than probly about .003". the upset metal wears down while casting. Once it is worn in and correct it about lasts forever, and can be popped some more if necessary. Also provides fantastic venting!!
.............While lapping a cavity out will open it up, you're obviously doing it via metal removal. While you're removing metal where you want to, you're also removing metal where you DON"T want. The first and fastest to wear will be the most fragile parts. These will be detail items like corners and edges.
While the driving bands expand, so do the lube grooves and these get shallower and narrower. You can eliminate some of this by embedding the abrasive only on the faces of the drive bands as much as possible.
IMHO, .005" is a lot to lap out.
................Buckshot
You could just buy a MAK mold from Lee. They're not very expensive.
Thanks for your suggestions. The mold in question is someones experimental. I'm not sure what they were going for but what they ended up with was a 100 gn SWC with a nominal dia. of .359. I could buy a Mak mold from Lee, but I want to see if the CZ82 will handle SWC bullets.
If you are taking that much material out, I would try to find someone with a 4 jaw independant chuck on a lathe & have at it with a small boring bar.
JiminPhoenix, No offense, but getting a boring bar in the right place at the right depth amoung the lube grooves is a muy problematical probability. It can be done, but you won't find many that can do it without moving some of the grooves around. Unless you've got a CNC lathe, you have to map out the cuts as per cut first land or gascheck out to (measurement on dial indicator) move to such and such measurement on longitudinal dial indicator, retract to distance that clears groove, move longitudinally to calculated start point of next land, insert bar to cut depth, move longitudinally proper distance for land to be cut & etc.. You Have to have it all calculated out and written down in steps, and premeasured (Make actual cut on trial hole to get correct depth) for the correct boring bar profile. Then you just gotta pray that the mold cavity is straight in the blocks. Wanna guess how probable that is?
As I said in my earlier post with a combination of (.003") Beagling and lapping the rest you can take a mold out .005. with good work habits you can lap .002" without visible rounding of corners on lands.
Geeze leftiye,
I’m kind of new around these here parts, so the last thing that I want to do is get off on the wrong foot by being contrary with any of the proven old hands here on the board. I’ll start off by apologizing now if that’s what I did.
I do have a fair amount of time in working on lathes, both CNC & conventional, although I will admit that I have never turned a bullet mold cavity before.
I had suggested using an independent jaw chuck so that the bore could be centered up. If the bore is not perpendicular to the block edges, then there are tricks using shims or potting compound to get around that problem. I agree that a dial indicator would be needed to be sure that you were in the center of the bore before any cutting began.
I would tend to disagree with you about a CNC being the better tool for the job here. I would take my old Clausing Colchester over the slant bed Puma CNC that I used to run if I had my choice on this job. All that work that you described mapping out the cuts & figuring the moves would indeed be necessary if you were working on an NC machine of any type. I would expect that on a conventional lathe, once you indicated the bore dead nuts, you could eyeball a right angle boring bar to the edge of the existing lube groove, touch off to the OD next to it & gently move out .0025” (.005 on diameter). That would get you a shoulder bumped out to the diameter where you wanted it. You could then pull the same trick on the other edge & just drag the bar back to clear the area between the two grooves that you just made. For a .0025” depth of cut in aluminum, this should be an easy pass, even with a small bar.
Now, I don’t know jack about mold design. I am just assuming that you would blow out the diameter of the driving band & probably one or two bands in front of that. I would also assume that you would be able to see where these bands currently exist when you put the bar up to them. I was figuring that we’re just talking about opening up a few diameters a little bit here, not making a mold from scratch. I know what trouble assuming too much can sometimes cause & I am only hoping that I haven’t crossed that line yet.
Now, I haven’t tried Beagling yet, so I can’t comment on the relative merits of that approach. I’ve only lapped parts to make them mate perfectly after close tolerance machining. I’ve never lapping anything to enlarge a bore to a target size before, so I can’t speak from experience on the merits of that approach either. I can only offer my humble opinions on the turning option because that is what I do have some semi related past history with. I’m sorry if I came out of the gate sounding a little brash & forward. I only wanted to offer an extra option.
Regards,
Jim
Nope, not upset at all, just have no faith in the eyeball method as those small diameter internal holes are hard to see inside. You could touch off in the base band, or use a shim to find the edge and cut from there as you've said, but I'd almost bet you'd be better off with a dial indicator reference of that cut depth from then on. Ditto with touching off on the top edge before making that cut and using that touch off as a reference (zero) on another dial indicator to move in to the center of succeeding driving bands with start point, and width of cut pre measured and dial indicator readings taking tool width into account pre calculated and recorded.
............I'm kinda new to this whole machining thing, only having a capable machine for the past 3 years or so. Before that it was a drill motor clamped in the bench vise :-). However my mind seems to be attuned to this kind of stuff, and always has been it seems. I grew up around a mechanicaly inclined father and grandfather. I really enjoy making stuff and am a bit intuitive it seems.
Not long after getting the lathe (a 1981 Model Logan/Powermatic 11x36) a friend had a shotgun slug mould a bit small for his scattergun, so he wanted some drive bands put in it. Not really knowing any better I said, sure I can do that.
http://www.fototime.com/B14C8C7293C3501/standard.jpg
And here it is. Not knowing any better but figuring it would work, I used a .375" drill blank for the tool and ground a tooth on the end to the width they wanted the drive bands to be and put a mild draught on each side, then the clearance for the bar.
http://www.fototime.com/13A02A26BD7AC9F/standard.jpg
I had already made an extendable indicator holder that is attached to the mounting bolts for the QC box to read on the carriage. Seemed like a good thing to have and easy to make. It came in handy. To do the mould I used that and then put a DI with a magnetic back on the cross slide to read on the compound.
The mould cavity was indicated in (held in a 4 jaw) front to back, and yes some shimming was required. I've since learned that no cavity is dead nuts to any exterior surface of the blocks one might care to check. I fed the tool into the base pin hole then retracted it a bit until I saw it mark the layout blue. That minus .0005" was my compound zero.
Then I ran the tool in, outfed it .050" (just clear of the cavity OD, and backed the carriage up so the tool bumped the ledge formed by the smaller OD of the HB pin. That was my zero for longfeeding. I thought I was pretty brainy, as everyhting seemed to go just ducky until I realized one tiny thing.
In advancing the tool with the carriage I had forgotten to figure in the width of the tool. This was pretty IMPORTANT as the person had only wanted 3 drive bands. CRAP! Since I had 3 bands cut and had enough room for a 4th I went ahead and cut it. Obviously it should have had much wider lube grooves. I figured I was out the cost of an new Lyman 12 ga slug mould.
Turns out the customer was happy with it and said it worked just fine, whew, ha! I don't do this anymore except on my own moulds. It's too tedious grinding a bit, and too nerve wracking cutting where you can't see, also the chance for a major whoopsie is too great, as just illustrated!
..................Buckshot
An 81 Logan is a nice machine to start on. My brother used to have one of those. It worked well for him until he moved up to something larger. It's certainly a far cry better than the ancient F.E Reed or 1920's vintage south bender that I started out with. What's even more important than the machine itself, is the fact that you seem to know what to do with it. Getting good clean finishes on steel like that can be a bit tricky, especially with a small hand-ground bar. My compliments to the chef on cooking up a nice pair of blocks.
Buck shot wow nice work. Id love to have the experience you have with a lathe.
............JIMinPHX and scrat, thank you both but the machine does the work :-) As I mentioned, I love doing this stuff and seem to be a bit intuative. Since it's fascinating to me, reading about it is entertaining, and truth to tell, much is common sense. Kinda like your cutting tool has to be harder then what you're cutting :-). You also do things better that you like doing, so don't ask me about plumbing or painting!
It all kinda boils down to that old saying of removing everything that doesn't look like what you want. However, there are many things that could be considered shortcuts and tricks that only come with experience, or picking the brains of those who are more experienced or more gifted. When told you'll say, "Right! Why didn't I think of that?" I made a diestock to use in the tailstock for threading short or small diameter pieces rather then single pointing.
However, some of my smaller dies are13/16" hexagonal. I don't know how to turn a hexagonal hole and was stumped as to how to utilize them. One of the members here said to just modify a 13/16" socket. ZOUNDS! Why didn't I think of that!!??
So far I haven't made any mistakes, but I HAVE made several spare parts for things that havn't been invented yet.
Check out my post on the Shooters.com forum about Boneheads :-)
.................Buckshot
I grew up a painters son, but nothing puts me in a worse mood than Plumbing! It's true what they say about Painters: The Painters House Always Needs Painting"!
Yea Buckshot, you can talk to 100 different machinists & walk away with 102 different little tricks of the trade. Just be careful of guys that call themselves toolmakers. Where I come from, that’s a code word for a slow machinist. ;-) No offense to the genuine tool makers out there. They are the cream de la cream of machinist industry. It's just that a lot of guys out there that claim to be tool makers aren’t really quite what they say they are.
That 13/16 socket & hex die method is a handy one for making threads quick. Single pointing is a slow & tedious process. The only two tricks with the die in a socket method are starting the die straight & feeding the die into the work at the right rate. I usually take 1 or 2 rough passes with a single point tool before using a die so that I am sure that it will go on straight. For short spans of engagement (1 or 2 diameters deep), you can usually get away with just starting with the die up flat against the back of the socket & that’s good enough. Some guys use a greased up deep socket with a spring inside to keep the die feeding along the material as it want’s to go. I usually just try to follow the infeed rate by hand with the tail stock. I pull the Morse taper slightly out of engagement with the tail stock socket first so that it can slip if I don’t quite keep up. I’ve also just taken a die in a regular die handle & run that over a slowly spinning shaft after I did a rough pass or 2 with a single point tool. On small diameters, you can get away with that. In any event, plenty of oil is a wonderful thing.
I also commonly use a tap in the tailstock chuck to make internal threads. If you are using a spiral point gun tap or a thread forming (roll) tap it works very well. If you use a hand tap from a hardware store, you will probably shatter the tap using this method. Gun taps & roll taps don’t need you to back up & clear chips like hand taps do. I typically do several hundred threaded holes this way before breaking a tap. I consistently get threads that pass class 3A inspection this way. You need to pull the same little trick of bumping the morse taper out of engagement a little bit first so that you don’t tear the threads out in the event that you don’t keep the tail stock moving at the same speed as the feed rate of the thread. You can buy a tension/compression tap holder for this, but I never seemed to need one.
If I am tapping a hole in the end of a shaft that absolutely must be perfect, then I use a different method. I put a live or dead center in the tail stock & jam that into the rear end of a tap that I have in a standard tap holder so that everything stays straight. I then just turn the tap in by hand. The biggest key in any threading operation (with the possible exception of lubrication) is to keep the threading tool lined up with the axis of the bore or shaft that you are working on.
As for making mistakes…
The only guys that don’t ever make any mistakes in machining are guys that don’t make any chips.
Another trick for using hex dies in a round die tool is just to tap a few set screw holes in the OD of the die holder. You don’t need full flats to keep a hex die from spinning. You just need a pilot diameter & a stop.
If you are using a socket, you don’t even need to modify it. You can just get one of those hex bits with a square drive on the end of it like you use with a cordless drill. Those fit right in the tail stock chuck.