My way to make a mold

[sb327]

First, I am trying to learn how to do pics in post, I will have several posts so bear with me b4 commenting, thanks.

Most have an opinion how a proper mold needs to be made. I don't. I have a way that I do it that I have had the best success with over the years. I have tried several ways, this is just the one I prefer.

This way can be done exclusively on a lathe. I have a mini-lathe that I can set at, drink coffee, and relax. I also have a 12x60 Clausing. I used the mini for this project.

So here we go.

Here I am doing the initial turning of O-1 drill rod (air hardening rod works well too, its a preference thing here). I get to about .001" then use 220grit paper to get to final dimension. Also, since I am using a 3jaw chuck, I will not remove the cutter from the lathe until ALL operations are complete.




Here I am turning the nose with a ball turner. The ball turner is about the simplest you can make and works just fine. If you would like to have more detail on it, I can provide info on how I made mine.



And here is just an image showing how I measure distance for features. Just a simple, cheap digital unit from HF mounted to a piece of angle clamped to the ways.

[sb327]

Here is the finished profile. Take a picture of the one you make, cuz it gets ugly after this point, lol!





Here I am cutting the profile in half. Some say perfectly half way, some a thou over, and some a thou under.  I go a thou under because this is not a 'D-reamer', it is simply a profile cutter. I purposefully used a dull endmill to raise a good burr to show up well in the picture. I kinda over did it, lol. In reality, you need to keep the burr created small, but the burr will come in useful later, during sharpening. This step can be done with a file in the lathe or vice, just keep things level nose to tail.





And here I show to leave a small portion of the cutting edge when relieving the back and bottom. How much the profile gets releived depends on the shape of bullet. Rule of thumb, smaller than the smallest bullet o.d. aft of the nose. It needs to fit in a hole that size without touching (until it gets to the nose portion inside mold). More detail on this later.  (Notice the excessive burr left at the cutting edge) Be sure to leave the burr.



 

[sb327]

At this point, I harden my bit. I start heating at the body (shank) of the tool until it is up to temp and then get the cutting end hot. If you are not familiar with reading various temps by available light vs. brightness of the red, just keep a magnet handy. When the steel becomes non-magnetic, it is time to quench. Now, if you read all of what is out there on how to harden and heat treat, you will likely never get to cut a mold. Because to do it 'by the book' requires a controlled furnace temp, controlled oil temp, controlled O2 environment and so on and so forth. I will say, 0-1 is very forgiving. My cutters and reamers have all performed well. I have cut MANY chamber reamers for various PB rifles/pistols and they cut steel just fine. Obviously, for a reamer, distortion is a concern. Chucking a reamer (fluted type) in a drill press and running it slow while heating and having your quench oil below to plunge while turning, has yielded excellent, no distortion results. A D-type is different and at bullet length, not a real concern about distortion.





Immediately quench. I use a light oil that is a mix of diesel and 30-wt. Room temp. This will be very smoky but I always heat/quench inside the shop for purpose of reading temps. Keep the bit in the oil, stirring it around, for a while. Oil cools the part way slower than water. When you are finished quenching, be careful not to drop, it can break easily. Check the back edge with a file to make sure you got a good quench. A file should just skate off it.




After hardening, it will be VERY brittle. I cook in a toaster oven for about an hour at 400-450. (mold cutters such as this 450, its more import that it not be brittle than it is to be hard)

[sb327]

At this point, we need to do an initial honing of the top. Here I am using a medium stone but one of the small, fine grit diamond stone works too.







Then we need to start back relieving as before, only this time use a fine diamond file. We are starting at the bottom of bit (top in the picture) and working our way to the cutting edge. This does not need to be much relief at all. The important thing is to go slow and NEVER take off more at the cutting edge than needed. This is where the burr comes in handy. If you watch it carefully as you go, it will act as an indicator as to how close you are getting. We want to remove all evidence (a noticeable dark line just below the cutting edge) of the burr, but NO MORE. And it needs to be perfectly smooth here so you end up with a smooth bullet. THIS IS THE MOST CRITICAL PART OF THE PROCESS, because you do not have machine contols to go by.

[sb327]

I forgot to get a picture of relieving the nose. It needs a good cutting edge as well because it will be cutting in a plunge fashion for at least a portion of the mold.

I can't modify my first post now. I was gonna take out that first line.

I got the picture posting figured out and will take some more.

Go ahead with comments or questions whatever at this point, I'll add more as we go.

Dave

[sb327]

Here is a sketch of what we are trying to accomplish in the relieving process. All the shaded area gets removed. We don’t want to relieve more than necessary though because the tool still needs strength.

Arrow points to cutting edge.


Dave

[scion19801]

nice little write up Dave. very helpful and much appreciated.  so how are you mounting your blocks and getting things indicated? I'm thinking some sort of mill vice setup would be bestso the molds blocks could be moved around a bit to open the cavity to proper size. but had seen others mount their blocks to the faceplate and put the reamer in the tool post and go that way.

[sb327]

In the lathe with a four jaw is how I originally started but now use a homemade face plate just for molds. Very simple to make. I’ll have it posted further in the write up here.

Dave

[sb327]

Here is my faceplate I made. Just a 3/4” shaft welded to a 1/4” plate. I use a collet in my lathe. The 3/4” shaft is drilled/reamed to 1/4” and I have a 1/4” pointed shaft for setting up blocks perfectly centered. Then pointed shaft is removed and plate mounted in chuck.

I only clamp one mold half so the other gets clamped to it. This way I can cast a bullet, measure and return back to 0 in the lathe easily.

Dave

[JuryRigger]

Wow!! Quite a write up Dave; thank you!  Will be PDF-ing this page once you've completed the series...
Jesse

[subscriber]

Very nice, Dave.

[scion19801]

nice face plate mounting setup. definitely helping me get things dialed in, in my mind. as i see more this looks like i could easily do my own 4 cavity mold. my jig setup would have to be a bit more elaborate to allow more room. i think my 10k south bend should be able to accomplish it with no issue.

[rsterne]

Very helpful article, I learned a LOT....

Bob

[subscriber]

I have a dumb question / suggestion:  Would it be possible to turn a cherry perhaps .04" smaller in diameter than the largest diameter of the mold; then just mill that cherry down flat to its midline?  Doing that would seem to incorporate all of the clearance grinding by virtue of the difference in radius.  See image below.

Surely all you need to do is cut the profile at the cherry "equator" to incorporate the radial differentials and nose radius that you wanted in the full diameter cherry (because this is just a form tool).  Then you zero off that one edge with the tool top face level.  Then use it, just like a full diameter cherry that is clearance ground. 

The only thing that you "loose" is seeing your full-size "bullet", before you deck the full diameter cherry, and cut all the relief into it.  If you can stand to see and verify your smaller OD cherry in CAD, then you have just taken a shortcut with no downside I can see.

See attached image and tell me what you think.

[sb327]

You certainly can. Diameters would be print minus .040” (or whatever). Your ball turner would still need to be set to print dimension.

 You could also four flute instead of D, plunge it with a mill to depth into a mold set up on a rotary table. Then offset x or y and rotate table.

Lots of ways to skin a cat. 

Dave

[scion19801]

wow, tons of good info coming from this. this one is going to deserve a "STICKY"

[rsterne]

This is not unlike a chamber reamer, except that you need the smaller diameter throughout in order to be able to plunge to depth when there are undercuts in the profile.... When making reamers, you don't cut away the diameter at all, but you cut the flat below the centerline to provide the relief angle.... The further below the centerline, the rougher and faster the cut.... Here is a drawing of a 3-flute reamer....



You can also make a single flute reamer by milling out a 90 degree segment as shown by the dotted line.... In either case, notice the flat that forms where the cutting edge intersects the OD is milled past the centerline by 5% of the diameter.... I have found that (5.7 deg.) provides a good balance between speed of cut and finish.... You can also cut the reamer straight across at that point, to form a "D"-drill, but that weakens it a lot....

I see no reason that you couldn't use something like this as a cherry, if there were no reductions in the diameter behind the nose.... ie a tangent ogive nose, followed by a straight midbody, like the way a swaged slug is shaped.... There is certainly no provision to clear chips, other than in the one main flute groove, whether that would cause a problem or not I don't know.... It doesn't when reaming chambers....

Note that the drawing is reversed (you are looking at it from the back/shank), as this reamer is intended to be installed in the tailstock, with the work rotating in the forward direction in a lathe....

Bob

[sb327]

Thanks Bob.

Now for the block. Pretty simple really. I did say when I started this that all the operations could be done on the lathe. Well that groove down the side might be a little bit tricky on a lathe without a milling attachment. You can clamp to a qctp.

If using Lee handles, make the groove 3/16” x 1/4” deep. I just put my stock in the mill and do one groove before cutting into smaller blocks.

Next would be to face the two inside surfaces. Clamp together. Drill the pin holes through one block and partially through the second. Drill under 1/4” and ream to .249”. I use 1/4” drill rod just because it’s usually .250”. Round/polish one end of each. Chamfer ALL inside holes. We don’t want burrs or interference fit pushout interfering with our blocks mating. Press or drive pins to where they just start fitting snug. (If you go a little far and it seems too tight but you can still pull apart with your hands, don’t worry. Aluminum expands at a greater rate than steel and will loosen upon heating.)

 (If your setup only allows drill/reaming one hole then unclamping to drill other, install one pin before reclamping and drilling second hole).

I didn’t get pics of drilling/reaming.

[sb327]

Once the pins are installed, face off the top. This assures that both tops are perfectly flat. No pics of that either. If you want to face the ends/bottom, you can do that now as well. This gets us a blank body to work with.

I am going to highly stress making this little plate I use. It works fantastic compared to a four jaw. I do not have a way of ACCURATELY measuring the driving band (most critical dimension) inside that tiny hole, on a boattail especially. Therefore, I like to cast a bullet or two during the process just to see where I am in the process. Once I get a good reference, I stop just shy, cast another/measure, and make final cut. Each time I stop to cast, I do not have to re-zero with the little plate. I just unclamp one half from the half that is clamped to plate, then clamp it back. This can actually be done without removing from machine by using a 'funnel'.





Once the block is setup in the lathe, you can drill out as much material as your bullet design will allow. If it is going to be a hollow point, drill and ream pin hole all the way through. Here I show cutting to depth with a 1/8" endmill because this is a flatnose profile.

[sb327]

Once you have removed some bulk material, it is time to setup your cutter in the toolpost. Clamp it good and get your height set (I set just a touch high so the cutter is not as likely to 'pull' into the work).

I set it by rotating the toolpost until I have two known points the correct distance from one another. You can also set it by indicating along the shank that is exposed in the toolpost. Your choice. I like knowing exactly where my cutting edge is. Tighten the toolpost down TIGHT.





Now we can plunge to depth. Set your carriage stop.




 Then start cutting the profile. Keep track of your 'zero', I mark mine with a marker on the cross slide wheel. That way when clearing chips/backing out, I don't cut my groove ridges.