Mold Modification, Turning FN into RN with Ball End Mill Cutter?

[turbo1889]

I'm going to contact Eric (the hollow point mold service guy) about this but I thought I'd post a thread on here as well and I am especially interested in the opinion of those members of this forum who are machinist on this.

Long story short I ordered a custom mold made to my specs. for use primarily in my 7.62x54R and 303-brit. guns but also for use in other "fat 30" guns. The mold is a work of art and it shoots very well. Unfortunately, I'm having all kinds of trouble with feeding problems in the bolt actions with the flat meplat catching on every little square edge in the actions and jamming things up. The meplat is the smallest size available from this particular mold maker at 0.18" and I do like the idea of a flat nose but the bolt guns don’t seem to like it at all.

So I pulled up the design in my CAD program and started doodling and this is what I came up with:

http://farm6.static.flickr.com/5166/5249781985_c4f5874a68.jpg (http://www.flickr.com/photos/54455625@N04/5249781985/)

That is a 3/16" ball nose mill cutter distinguished in a maroon/purple color. So how hard would a modification like this be to pull off? I realize that I'm probably going to get a cosmetic issue at the transition point between the two curves but I've already got a ring on the base of the nose where there was a tooling change in the original mold cut anyway so cosmetics aren’t that big of a concern.

[JIMinPHX]

The hardest part is indicating accurately to the center of the nose. After that, all you need is a good rigid ball mill, a little lube & an accurate plunge depth. A vacuum to suck up the chips might be a nice touch too.

I'd stick with a 4-flue ball mill. They tend have much better rigidity than the 2 flute type. You're going to be working far enough out from the tool holder, that going with carbide might be a good idea too.

[deltaenterprizes]

With a set up like in the thread about enlarging driving bands you could do it by hand.

[longbow]

I think I would be inclined to make a bushing that just fit inside the tumble lube grooves at the nose and body right on size then turn a ball nose end mill by hand if the mould is aluminum or very slowly in a drill press or milling machine if the mould is iron.

If the bushing is turned to exact size to fit the mould and shank of the end mill it should guide the end mill well and keep it centered. Also, you can put a stop ring on the shank of the end mill so you can't go too deep.

Longbow

[arjacobson]

You could do it pretty easily on a vertical mill. Just indicate the bore and plunge with a ball end mill. Only thing difficult would be the depth as that would have to be spot on to blend in the old flat point..

[nanuk]

could you just use a dremel and ease the sharp edges on the feed ramp et al?

[JIMinPHX]

I think I would be inclined to make a bushing that just fit inside the tumble lube grooves at the nose and body right on size then turn a ball nose end mill by hand if the mould is aluminum or very slowly in a drill press or milling machine if the mould is iron.

If the bushing is turned to exact size to fit the mould and shank of the end mill it should guide the end mill well and keep it centered. Also, you can put a stop ring on the shank of the end mill so you can't go too deep.

Longbow


I think that I like this idea best.

[Pepe Ray]

Turbo.
I think that ,before I screwed up a perfictly good mold, I'd try several round nose boolets of varying softness to be certain that my efforts would not be wasted.
It would be a pity to find that the jams still occured. Next step? A pointed boolet?
Q,,,
Pepe Ray

[longbow]

Pepe Ray has a good idea too if you can get some different designs of the same length or at least that can be seated to give the same length outside the case you would get an idea of what works before doin gmould work.

I have the NOE 314699 mould ~ if you are interested in a few long round nose boolits I can send you some. I also have the 31141 but it may be too short.

That meplat doesn't look big enough to cause problems. Is it just one gun or several? Maybe nanuk is right with doing a little feed ramp work if it is just one gun.

I also have a couple of home made moulds that make long round nose and pointy boolits if you wanted to try those for feeding too.

Let me know.

Longbow

[turbo1889]

Yes, unfortunately, it is more then one gun that is having trouble. I think this is partially my own darn fault for making the nose a TC shape, a more curved nose that stays fatter further towards the tip and then curves in towards the meplat sharply at the very last like on a ranch dog mold would probably feed just fine. Live and learn, one of the problems with custom molds made to your own specs., they are made to your specs and there is no one to save you from yourself. :killingpc :groner:

Which is also how I ended up with the tool change ring on the base of the mold as well because I failed to take the necessity for a tool change into consideration that I had been warned about on a previous mold and should have used a short concave radius at the base of the TC nose to ensure a smooth blend on the curve intercept.

A picture to illustrate:

http://farm6.static.flickr.com/5208/5222132977_b70baeb686_z.jpg (http://www.flickr.com/photos/54455625@N04/5222132977/)

I think you can see what I'm talking about as far as I should have specified a short length of concave curve at the base of the nose rather then just a straight taper nose since the tooling change from side cutting groove tool to end cutting boring bar shows up as that ring on the nose. My fault not the mold makers, I think you can also see how that sharp edge of the nose could easily catch on stuff.

As to how I know whether a RN mold will work or not. The Lyman 314299 works just fine as far as feeding in all the guns in question its just that it is an inferior mold for my needs since at least the one I've got has a bore rider nose section that is too big of diameter and causes chambering problems in some guns and a body that is too small of diameter and isn't big enough even un-sized, as cast to fill the bore of some guns. My custom mold with the TL grooves on the nose solves the bore rider problem since the bore riding section can be large enough to work with the guns with the biggest bores and still be easily engraved by the tighter bores since the bore ridding section is made up of TL grooves rather then a solid cylinder which does not engrave easily if oversize (like the 314299). And the main body section is the right size coming out of my mold at 0.316" as cast with WW and I can cheat that up another thou. if necessary by using type metal with tin added.

I really like the idea longbow has given, in fact I think I'm going to make a bushing that tightly and exactly fits the entire boolit cavity. Its going to be a cast lead bushing. If I take a 3/16" drill bit upside down with a nice true flat back side that end should self center in the nose taper. Then I use a set screw locking counter sink cutting attachment on the top end and let the taper of the teeth of the counter sink cutter center the bit at the top of the cavity and then I very carefully pore in some type-metal alloy with a ladle in the empty space between the counter sink cutting teeth and I should then have a boolit cast from the mold with a 3/16 hole running through its length dead center. Probably the best bushing possible for keeping a 3/16 diameter cutter centered.

I'll try a ball nose first and if that isn't enough (I would be surprised if it isn't considering the 314299 feeds fine) then I could take a 3/16 drill bit and chuck it into the drill press and hold a carbide grinding file up against it while it spins to make a pointier 3/16" nose cutter bit. One can always cut it out further and make it pointier but you can't go back to less pointy.

Here is the tools I'm looking at getting for the project (Clickable Links):

3/16" Ball End Mill (4F C) (http://www.amazon.com/4Fl-Ball-Carbide-End-Mill/dp/B0033B0SP0)
Stop Collar Set (http://www.amazon.com/7-Piece-Drill-Stop-Bit-Collar/dp/B001711QJU)
Counter Sink Cutting Collar for 3/16" Bit (http://www.amazon.com/Type-Countersinks-FUL-E92-Drill-Bit/dp/B002PK7PFG)

[longbow]

turbo:

Using a hard alloy and casting to fit the mould is a good idea. You may have to pre-heat the mould and "core" to get the molten metal in and get good fillout but if you can do it that should work well. You should use a mould release (graphite spray?) on the "core" to make sure there is a small clearance or the metal may shrink onto the core and stick.

If all goes well you should get perfect fit both to the mould and end mill.

Even if you can't get a good casting you could drill a hard bullet cast from the mould as a bushing. That would at least give a perfect fit to the mould.

Good luck.

This is a bit of a deviation from your usual large bore projects. It is an interesting design you got made, I hope it all works out for you.

Longbow

[38-55]

Turbo Sir,
You may find that by 'playing' with seating depths you may be able to minimize your feed issue problem. Personally I'd try this before any mods to the mold.. As for your mod.. it's not unreasonable at all.. though once again.. I'd go about it a bit differently so if you will indulge me my ramblings, here's how I'd go about things.. I' d indicate the mold in a 4 jaw chuck in a lathe and just use a form tool ground out of HSS.. but that's just how I'd go about things..
Hope this helps
Stay safe
Calvin

[HeavyMetal]

Think I'd call the mold maker and explain to him the mod you want made and see what he charges.

You might get lucky and find he will do it for less than your tooling costs.

I've had Erik do several molds for me because of this very reason.

[MakeMineA10mm]

I think I would be inclined to make a bushing that just fit inside the tumble lube grooves at the nose and body right on size then turn a ball nose end mill by hand if the mould is aluminum or very slowly in a drill press or milling machine if the mould is iron.

If the bushing is turned to exact size to fit the mould and shank of the end mill it should guide the end mill well and keep it centered. Also, you can put a stop ring on the shank of the end mill so you can't go too deep.

Longbow

I think this is the idea right here. You don't mention if your mold is brass, alum., or iron, but be careful what material you choose for your collar so it is clean, smooth and soft-enough so as not to gall the alum., or brass, if that's the material you got the mould made from. Hand turning will be a lot safer.

I'm running into the same dilema with the same maker, because I want to use him for a rifle boolit design, but it's gonna have a point, so maybe have to choose a different maker, unfortunately...

[deltaenterprizes]

You have a problem with the counter sink being 1/2'' O.D., it will not fit inside the mold. Why a carbide end mill, HSS is fine. It is from Victor Machinery Exchange and the last time I ordeded from them there was a $25 minimum order.

[turbo1889]

Already played with the seating depth within the range that the boolit allows, the TC nose shape with the flat meplat with a sharp edge around the parimeter is the source of the issue as far as I can tell, a redesigned boolit with a generous radius edge around the flat meplat and a fatter radius type nose like a ranch dog boolit rather then the TC I went with would fix the issue no doubt but that means another mold and I'd rather try to fix this one first

The mold maker who made this mold only does boolit molds with at least a 0.18" flat meplat on the nose; he is not the only custom mold cutter that makes that condition. I know of two others who also have a minimum 0.18" flat meplat on the nose. It has to have something to do with the tooling used in the type of CNC lathe boring technique these guys use. Which brings me to why I would like to figure out a way to do this myself by hand and get my own tooling instead of just run to Eric or others every time I need a .18" meplat rounded out to a 3/16" ball. I order a lot of custom molds, I rarely buy factoy molds anymore and since 0.18" seems to be the magic number and a 3/16" bit size is just right to modify that flat meplat into other shapes if I can figure out how to successfully do this and have a little kit of the stuff I need then it opens up a lot more possibilities for me if I know I can do this kind of mod myself. In other words I can just order and then after I get the mold finish off the tip to my specs regardless of what the original mold cutter had in mind. If this "molded bushing" trick works I could even do my own hollow pointing jobs by just drilling straight through with a regular 3/16" drill bit and then make my own HP pins from 3/16 piano wire.

This mold is brass, which is normally my material of choice, with the exception of a few types of molds where iron is a better choice despite its suseptability to rust. I only go with aluminum if I have too and have been known to choose not to use custom mold cutters who only cut aluminum molds if I can find someone else who can make the boolit in a non-aluminum block. I do have a couple custom molds that are made from stainless steel, unfortionatly that old gentlmen has gone on to the happy hunting grounds up yonder and everyone else I've run into who I mention custom mold cut in SS blocks looks at me like I'm crazy, apparently the stuff is a real PITA to work with from the machining side of things.

The counter sink is a 1/2" on the outer diameter the angled teeth taper down to the diameter of the drill bit it is designed to fit (3/16" in this case). Here is what I am thinking so far for how I would try to cast myself a bushing with a 3/16 core hole that is dead center:

http://farm6.static.flickr.com/5009/5255896656_b82be3574f.jpg (http://www.flickr.com/photos/54455625@N04/5255896656/)

Basically, simply using the counter sink as a centering cone that still allows me to pore lead into the cavity due to the fact that it is a toothed cone and not a solid one.

As far as the carbide end mill; I like stuff that actually lasts a while and it is only $10 for the carbide so just go for it is what I was thinking especially if I end doing this to more molds in the future if this works out well. Did you buy through them direct or go through amazon.com? Couldn't find anything about a $25 minimum order on their amazon section.

Well, I think that addresses all the posts since I posted last, plus some random rambling of course.

[Centaur 1]

Turbo, My opinion for what it's worth. I think that you're going to have a hard time casting the bushing without the lead hardening too soon. If you have a lathe available you might want to just turn a bushing that's the diameter of the lube grooves, then drill a 3/16" hole through the center. Or you might even be able to find a piece of 5/16" tubing at Ace hardware. Just chuck a piece in a drill press and file notches to fit the lube grooves.

What type of machines do you have available, do you have a mill? Brass may be a soft material, but cutters have a tendency to grab. Even when drilling a hole, I always stone the leading edge so that the drill bit is less sharp. If I were doing this mod, I would use a milling machine. I would indicate the cavity so that it was aligned with the spindle. Place the ball mill in a collet and with the machine off, lower the quill until the mill touches the bottom of the cavity and lock the quill. Zero the dial on the knee and lower the knee a few thousandths. Turn on the spindle and make your cut by raising the knee slowly, .093" should be about right. By raising the knee versus lowering the quill, the cutter won't be able to grab the brass. Trust me on this, for as soft as brass is, it is very hard to drill accurately without using certain techniques.

[crazy mark]

First I would try a RN TP to see if that helps it feed before I went to the expense of having the RN put on it. I have done that with several moulds to see if the fed better and the answer was usually yes. Notice I said usually. Mark

[mooman76]

One thing you might try is to get some lead RBs the size of what you want your nose modification to be. Drill a hole in the nose tip and glue or attach your ball in the hole you bored so you can load a dummy round an make sure it chambers ok before you alter your mould.

[JIMinPHX]

Why a carbide end mill, HSS is fine.

I had thought that a carbide ball mill might be a good idea because ball mills tend to chatter & wander a bit when you plunge them & in this application, the ball mill is many diameters in length out of the tool holder, which would tend to amplify that problem.

The added rigidity of carbide will reduce the the likelihood of having problems with chatter & wander. There will be no advantage to having a carbide cutting edge, but there will be an advantage to having a carbide tool body. Also, the price of carbide ball mills has come way down. They're actually pretty reasonable these days.

[deltaenterprizes]

I had thought that a carbide ball mill might be a good idea because ball mills tend to chatter & wander a bit when you plunge them & in this application, the ball mill is many diameters in length out of the tool holder, which would tend to amplify that problem.

The added rigidity of carbide will reduce the the likelihood of having problems with chatter & wander. There will be no advantage to having a carbide cutting edge, but there will be an advantage to having a carbide tool body. Also, the price of carbide ball mills has come way down. They're actually pretty reasonable these days.

I was concerned with how easily they chip and break if dropped.

[Red River Rick]

With the proper CAD/CAM program and a CNC milling centre, using a 3/16" Ball nose end mill would make a quick job of changing that nose profile to what you want.

RRR

[JIMinPHX]

I was concerned with how easily they chip and break if dropped.

A valid concern.

[TomAM]

Turbo, it would be helpful just for future reference to try a deeper seating. Go deeper than normally allowed by this nose length, just to see what the OAL must be to allow smooth functioning with this meplat. Sometimes it's surprising how aggressive a nose can be with a short enough OAL.

[1Shirt]

:coffee:I agree with Pepe Ray!
1Shirt!

[turbo1889]

Well I finally got around to doing the mod to one of the two cavities:

Step one, casting the center alignment bushings:

Tool set-up used:
http://farm4.static.flickr.com/3451/5708580408_4d2f225f81_z.jpg
http://farm3.static.flickr.com/2189/5708580490_b6695dc0c3_z.jpg
http://farm3.static.flickr.com/2296/5708013465_943ec63380_z.jpg

Results:
http://farm4.static.flickr.com/3058/5708013589_0b9cc9cf3d_z.jpg
http://farm3.static.flickr.com/2432/5708013679_579c76ae3b_z.jpg
http://farm4.static.flickr.com/3334/5708014005_eca82b1c3d_z.jpg
http://farm4.static.flickr.com/3334/5708014005_eca82b1c3d_z.jpg

[turbo1889]

Step two, making the cut:

Tool set-up used:
http://farm3.static.flickr.com/2171/5708581336_09b7550bd7_z.jpg
http://farm4.static.flickr.com/3014/5708581432_58b815757d_z.jpg
http://farm4.static.flickr.com/3260/5708014443_851d383be6_z.jpg
http://farm3.static.flickr.com/2347/5708014539_dbb797af5c_z.jpg
http://farm4.static.flickr.com/3659/5708581732_3624328705_z.jpg

Cutting:
http://farm4.static.flickr.com/3470/5708014745_994dd82e13_z.jpg
http://farm4.static.flickr.com/3023/5708014873_c078dce859_z.jpg

[turbo1889]

Step three, lapping and polishing:

Lapping:
http://farm4.static.flickr.com/3558/5708015489_0460f2ecbe_z.jpg
http://farm4.static.flickr.com/3004/5708015683_71cbf37a50_z.jpg
http://farm3.static.flickr.com/2184/5708016075_7bf2e6ca51_z.jpg
http://farm3.static.flickr.com/2102/5708015569_d4bbd39d2d_z.jpg
http://farm4.static.flickr.com/3020/5708016271_1a15c341d2_z.jpg
http://farm2.static.flickr.com/1407/5708015829_bddbcceb14_z.jpg

Polishing:
http://farm3.static.flickr.com/2347/5708582020_a0339e4a9a_z.jpg
http://farm3.static.flickr.com/2699/5708582140_595e6599d1_z.jpg
http://farm4.static.flickr.com/3240/5708015209_f5cf3db563_z.jpg
http://farm3.static.flickr.com/2402/5708582362_20842f0ec0_z.jpg

[turbo1889]

The final results:

http://farm3.static.flickr.com/2358/5708016837_89ca7616a4_z.jpg
http://farm3.static.flickr.com/2400/5708584064_2f5617f160_z.jpg
http://farm3.static.flickr.com/2122/5708017147_cd09fa0b03_z.jpg

http://farm4.static.flickr.com/3093/5708583786_54bc3c8967_z.jpg
http://farm4.static.flickr.com/3595/5708016395_cf284ed112_z.jpg
http://farm4.static.flickr.com/3492/5708016503_56ac5cdac1_z.jpg


In conclusion, I think I did pretty well over all for a first try at doing this sort of thing. I cut just a little too deep and I’m off center by about 0.002” to one side and you can just barely tell with the naked eye if you look real close. Also some slight chatter marks that didn’t completely polish out.

Think I will still be good for decent accuracy and it should solve the feeding problems I was having. I’m hoping I can now load this boolit in 7.62x39 cartridge and get it to cycle in my SKS now too. Haven’t loaded and shot any yet so all that remains to be seen.

[nanuk]

Can't you lap the RN with cutting compound on the nose to even out the centering?

it would make it less round, but not enough to cause an issue I'd guess....

[turbo1889]

Can't you lap the RN with cutting compound on the nose to even out the centering?

it would make it less round, but not enough to cause an issue I'd guess....

Yes, that is a possibility and I need to do some more polishing on the nose to remove a few of the cutting marks that are leaving fine line rings on the nose anyway. But I plan on doing some accuracy and feeding tests by loading and firing some rounds first before I do any more work on the mold.

As to how I know I'm 0.002" off center, I used a neck turning bench rest set up with the floating dial gauge attachment to figure that out. Just took a piece of brass that had a neck that was dead nuts on center for its neck and seated a boolit inside the neck and then measured on the boolit nose for centering just like one measures on the outside of a case neck to check them for centering.

This is one of those "To Be Continued" things and I will add on to this thread as the project progresses.

[Centaur 1]

Ideally it would be nice if we all could have a milling machine out in the garage, but .002" by hand is pretty darn good. I've worked with plenty of guys who would have trouble doing that in a Bridgeport. Keep us posted with your results, the mold looks great.

[turbo1889]

Success !!!

Well, I test fired some rounds and then I put the mold through a second session of lapping and polishing and then loaded and test fired some more rounds. Long story short the second lapping and polishing session got me on center with less then 0.001” error (my previously explained method of checking for out of round isn’t capable of measuring less then that) but it didn’t seem to make any difference on the target board but did improve the cosmetics of the resulting boolit. Here are some photos of the mold and resulting boolit after the final lapping and polishing session:

http://farm3.static.flickr.com/2753/5720681341_724c65ba8a_z.jpg (http://www.flickr.com/photos/54455625@N04/5720681341/)
http://farm3.static.flickr.com/2257/5721239538_ac495500eb_z.jpg (http://www.flickr.com/photos/54455625@N04/5721239538/)
http://farm4.static.flickr.com/3191/5720681663_fd100091e3_z.jpg (http://www.flickr.com/photos/54455625@N04/5720681663/)

I then did some final loading and casting and did some more test firing. Feeds wonderfully in every gun I tried it in including the semi-auto SKS action. Comparison groups of before/after the second lapping and polishing session were shot with a scoped 303-Brit at 100 yards. Didn’t save those targets or take pictures of them since there was effectively no change in the groups that were printed (This confuses me by the way; anyone have an explanation of why the off center didn’t matter ?).

I did save two targets for photos. First target is the SKS at 50 yards off hand standing with iron sights. Second target is my best shooting Mosin-Nagant that has an genuine vintage WWII era Soviet sniper scope mounted on top of it which was shot at 300 yards with my best high power cast boolit load combination that I have developed for this gun and boolit so far (just with the new RN boolit profile instead of the old FN profile) off the bench with sand bags. The missing tenth boolit on that target hit above the target for my first shot and I aimed below the target for the rest of the group, apparently the round nose does improve the boolit’s ballistics enough to noticeably change point of impact at that range. Accuracy appears to be almost as good as the original FN profile, I’ll have to re-adjust my scope to be sure since aiming below the target where there isn’t as visible of a point to hold on may have opened up the group.

http://farm3.static.flickr.com/2734/5720681463_a26ce80bf3_z.jpg (http://www.flickr.com/photos/54455625@N04/5720681463/)
http://farm4.static.flickr.com/3066/5721239694_39e441cc5e_z.jpg (http://www.flickr.com/photos/54455625@N04/5721239694/)

[geargnasher]

Nice work, Turbo, good creative problem solving.

Gear

[JIMinPHX]

Wow, I just found this thread again. Those are some pretty impressive results for a guy without a machine shop.

I like the idea of using a cast boolit as a drill bushing. I didn't think of that. If you would like to do a more accurate job of drilling a hole in the center of a boolit, you might consider one of my drill jigs - http://castboolits.gunloads.com/showthread.php?t=71615

[edward hogan]

Wondering about whether just going with a Round Nosed top punch would have reformed the bullet nose enough to determine if the modification were justified.

Really nice work, done with a hand drill? Wow! Great thinking, using boolits drilled out to serve as bushings.

I have a .338 RN mold which I am experimenting with using a .358" flat-nose top punch. Wheelweight alloy deforms just a minimum when sizing so might not have needed to modify the mold at all?

[cbrick]

turbo1889,

Fascinating! Both the look of the mold and the groups.

The only disappointing thing to me was I was curious what Erik had to say. Doesn't matter now.

Nice work.

Rick

[turbo1889]

Eric thought the best way to do it would be to drill the mold for a HP pin just like he usually does and then make a pin with the ball end mill cutter that was concave to form the RN rather then us the BEMC directly on the mold.

[cbrick]

See? That's why Erik makes the big money. :drinks:

That's a great idea, you could have any number of different points for that bullet from HP to cup point, round nose. The sky (and your wallet) is the limit.

Rick

[turbo1889]

Yes, but a mold so set-up wouldn't have the casting speed/ease because you have to deal with the pin in the casting process, at least if it were a conventional style pin. And, most importantly in my decision to attempt it myself, his solution could still be done to my mold if I were to screw it up trying to do it myself since the nose would be bored out to fit the pin anyway.

[HamGunner]

Good job and that is some great shooting