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Very Hot Topic (More than 25 Replies) Making/modifying lathe-bored moulds (Read 13470 times)
Cat_Whisperer
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Making/modifying lathe-bored moulds
May 28th, 2007 at 7:24pm
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My real goal (for which I bought the mill and lathes) is to be able to make bullet moulds "my way".  (To be able to change ONE feature for a given application.)  SOMEDAY I'll get there - make my own cherries and all, but not TODAY).

I did bore out my first mould - a Lyman singal cavity 38sp wadcutter to a 330 grain two diameter .375 mould (Win and H&H).

I did not expect perfection, merely to learn what to do better on the second mould.

Got the bore riding portion and the base band a little small.  But I now know with my alloy du jour that I can expect 0.003" shrinkage on the diameter.

A 330gr wadcutter looks crude; but I did get it so it drops freely from the mould on the first try.

330gr is about 1.1" long.  Too long, but I know it stabilizes well and 20gr of 4227 works well with it.  (Leading was 'substantial' but easy to clean and expected at these diameters).  

Patterns were not much different from other cast bullets at 25 yards - that's something that MUST improve.

A good learning experience, more next week.


« Last Edit: May 28th, 2007 at 9:52pm by Cat_Whisperer »  

Cat Whisperer (trk)
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RJM
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Re: Making/modifying lathe-bored moulds
Reply #1 - Jun 3rd, 2007 at 7:00am
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Cat,
Try the alumium Lee molds for reboring - cuts cleanly & easily, comes with handles, cheap. 

For the .310 cadet, I rebored a Lee mold by centering the blocks in the 4-jaw chuck (tedious). The boring tool was turned from a piece of round rod and the cutting edge formed by filing the end to 1/2 the diameter. 

The next thing I'd like to try is making a point pour mold with one of these.
Regards, Ron
  
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Re: Making/modifying lathe-bored moulds
Reply #2 - Jun 3rd, 2007 at 7:22am
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I have never attempted to make a mold and most likely won't but a couple of what i hope help pointers being a tool and die machinist for the past 30 years.
cutting fluid is important, relton makes little cans of "black oil"  for steel, and "a9" for aluminum. they also make tapping fluids for threads.
the biggest thing is grinding the tools out of TOOLSTEEL, blank pieces can be had or you can buy lengths of a2 make your cherry, or cutter, harden in foil at 1750 for about 30 mins air cool then draw @ 400 for about the same lightly sharpen the cutting surfaces and hopefully away you go.
a2 does not change size when heat treated.
hope some of this helps
irish
  
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Re: Making/modifying lathe-bored moulds
Reply #3 - Jun 3rd, 2007 at 8:10am
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Ron, Irish66

I may well have to do the Lee's.  I've got some 6061 and finaly got a lead on getting some 7075; and doing in a few Lee's would be a good warm-up before putting ALL the work into a mould.

I also have a .310 cadet for which I want to open up a 311316 on the front band and make a custom H&I die so I can size (to two diameters) and inside lube.  Might work; I just have to know.

I'm getting better at centering the moulds in the 4 jaw chuck, practice has helped.

And I've now got in stock 3/8, 1/2 and 3/4" three foot lengths of A2.

Next step is milling off about half the round (tilting down by 5-8 degrees and milling a flat on the top on which to index) and the to grind the profile of the cutter.  (I'll take pictures of the boring bar holder I made for these.)

Going to start with two custom cutters - one to do the ogive (after drilling/boring) and the other to do the whole base - two bands and one groove in one step.

A2 is certainly the concensus for these (considering my inexperience).  Hardening and tempering is something I understand but don't have the experience nor have the temperature control to do a consistant job on -- I'll farm that out to someone close who has an excellent reputation.  Down the road I may mess with it.

THANKS for the input!  Progress is slow, but it's one step at a time and so far with little backtracking.




  

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Re: Making/modifying lathe-bored moulds
Reply #4 - Jun 3rd, 2007 at 9:23am
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Cat, I've made a few moulds by turning the bullet shape on a piece of drill rod, then filing the tool to a proper form.  (No mill)  The way I do it is to rough drill the cavity to within .010" depth with a sub-point dia. drill, then step drill out to just under the grease groove dia. for the body.  Set the profile tool up like a boring bar, run it forward to the finish depth, then outward to cut the cavity to the shape and diameter you want.  Not an elegant method, but it works for me.   

As you've found, the larger bullets need about .003" to .004" shrinkage factored in to the cavity diameter.  You can get pretty close in figuring out how much to allow for smaller moulds by taking a mould that casts good bullets in about the diameter you want, and making a Cerrosafe cast of the cavity.  Mike the Cerrosafe about 2 hours after it solidifies, and you'll get the actual dia. of the cavity.  Keep a chart of what you come up with for your alloy for future projects in similar diameters.

David
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David Kaiser
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Re: Making/modifying lathe-bored moulds
Reply #5 - Jun 3rd, 2007 at 9:33am
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The benefit of a full profile is that it will be the same for all cavities; the problems obviously include chatter.

David, with a wider cutter how do you address that - what speeds for which materials, lubes?

  

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Re: Making/modifying lathe-bored moulds
Reply #6 - Jun 3rd, 2007 at 10:48am
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A2 is not difficult to heat treat yourself for a tool that is going to get relatively light use.
With the part in your lathe, and turning at a slow RPM... heat it with a torch. Heat it evenly.  Heat until the whole part is "orange just turning yellow-ish", then shut off the torch and let the part cool.

"The books" would say to hold the part at temperture for X hours per inch of thickness... but for a turning tool, you're only concerned about the A2 getting hard at the cutting surface, not hardening all the way through.
Likewise, if this is a tool that will get used once or twice, you can get away without tempering it after hardening.... but use it carefully with light cuts.
I've made a couple small reamers out of A2 quite sucessfully with a "by eye" heat treat.

You've inspired me to rework a Lee mold to add a driving band to a .38 special mold for a .380 Rook.

Paul F.
  
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Re: Making/modifying lathe-bored moulds
Reply #7 - Jun 3rd, 2007 at 1:45pm
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For a lathe cutter I can see winging it to start with - thanks for the technique - but when I get to doing a cherrie with 3, 5 or 6 teeth - then I'll let someone do it professionally.

I'm always amazed at the level of precision achieved by folks in the 1800's with the tools they had; and I temper that with the fact that new tools are ALL made with old tools.

  

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Re: Making/modifying lathe-bored moulds
Reply #8 - Jun 3rd, 2007 at 2:25pm
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I have modified several moulds by using old twist drills as cherries. The end radius was achieved with a hand held grinder and the grooves with a dremel type tool held in the lathe tool post. The fine dremel cutting wheels were used to cut the lube grooves. Aftet the shape was complete, I removed the drill from the lathe chuck and sharpened up the cutting edges with the dremel. Every time I have done this, I have expected to scrap the first Lee mould that I used as the base. Every time, the technique has worked first time. The twist drill cherry is used in a pillar drill and the mould closed on it using the drill vice after the depth has been set. The 2-cavity mould for my Swiss Federal muzzle loader casts bullets within 1grn of each other consistently.
Fred.
  
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Re: Making/modifying lathe-bored moulds
Reply #9 - Jun 3rd, 2007 at 3:05pm
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Cat Whisperer (and all others) if you need small amounts of any sort of metal, (7075 included) you can buy from Speedy Metals online.  My favorite source for gunsmithing metal these days.   

(You need to Login or Register to view media files and links)

Now, for mould making in aluminum, I reckon I'd use 2024 alloy.  Cuts very clean, like brass.  Chips don't get stringy or gummy like 6061 can. Wonderful stuff.   

7075 is great for aircraft structures, but you don't need the tensile strength for a mould.   

  

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Re: Making/modifying lathe-bored moulds
Reply #10 - Jun 3rd, 2007 at 7:29pm
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6061 is what I could get locally, that's a plus.   

2024 is certainly worth a try - what characteristics do you like?

7075 I got because of hardness, not the strength and some other folks that make moulds for a living recommended it.

Thanks for the info!



  

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Re: Making/modifying lathe-bored moulds
Reply #11 - Jun 3rd, 2007 at 9:21pm
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Cat_Whisperer wrote on Jun 3rd, 2007 at 9:33am:
The benefit of a full profile is that it will be the same for all cavities; the problems obviously include chatter.

David, with a wider cutter how do you address that - what speeds for which materials, lubes?



I'm running my lathe about 120 rpm, re-cutting old Lyman moulds that have been abused in their previous life.  An end view of the cutter is essentially a D shape...to just under half the diameter of the steel "bullet".  For lube on these, I use Brownells Do-Drill, then soak the completed mould in solvent to remove the oil before use.

David
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David Kaiser
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Re: Making/modifying lathe-bored moulds
Reply #12 - Jun 4th, 2007 at 7:54pm
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Thanks, David -   I'm vascilating between 70 and 140, just using the water soluable coolant or a little way oil.  No conclusions yet, need much more play time.  About the same shape - a bit more than half the dimeter, but back side releaved by milling.

  

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Re: Making/modifying lathe-bored moulds
Reply #13 - Jun 4th, 2007 at 8:21pm
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Use kerosene on cast iron Wink
  

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Re: Making/modifying lathe-bored moulds
Reply #14 - Jun 5th, 2007 at 1:28pm
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Jim_Borton wrote on Jun 4th, 2007 at 8:21pm:
Use kerosene on cast iron Wink


That makes perfect sense - it's commonly used when tapping CI !

Why didn't I think of that?

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