Lee Precision and Predictable Results

[Boomer Mikey]

Lee Precision’s Mold Diameter Specifications; -Minimum information required:

Lee Precision wants mold cavity dimensions not bullet dimensions to be specified for their production of molds and you must give them a range of 0.003” to work within.

To specify a range of manufacturing tolerances to obtain the bullet size you want you must consider your alloy and its shrinkage characteristics.

Linotype alloy will produce the largest bullets: at mold cavity diameter.

Wheel weights and 1 part tin to ten parts lead alloy have similar shrink characteristics as follows from the RCBS Cast Bullet Manual:

.22 -0.0004”
.24 -0.0005” 1 in 10 -0.0004”
.25 -0.0005”
.27, .28, .30 -0.0006”
.35 -0.0007”
.37 -0.0008”
.44, .45 -0.0009”

For Lee Precision Custom Group Buy molds I run the diameter stated in the posting will be MAXIMUM bullet diameter with wheel weight alloy. I’ll give Lee Precision a range of -0.002” to +0.001” over desired bullet diameter to work with. For a 0.462” bullet design, production mold cavities would be between 0.460” and 0.463”. As most lathe work will typically be on the large side or middle of a tolerance range, bullet mold cavities will average 0.0015” to 0.0025” over the minimum size specified resulting in bullets between 0.4606" and 0.4616" with wheel weight alloy and bullets between 0.4615” and 0.4625” with linotype alloy.

This is my best guess of how to get predictable results with Lee Precision Custom molds. If you want bigger or smaller bullets with wheel weight alloy, increase or decrease the maximum size desired but specify the same -0.002” to +0.001” tolerance range but apply the shrinkage values within that range...

To get a 0.314" max size bullet from wheel weight alloy with a 0.0006" shrink value would equal a minimum mold cavity of 0.3116" and a maximum mold cavity of 0.3146" (add the shrink value to the maximum bullet size desired and subtact 0.003" from that to get minimum cavity size.)

For a 0.314" minimum size bullet add the shrink value for the minimum size cavity and add 0.003" for the maximum size cavity (0.3146" to 0.3176".)

Lee Precision is a manufacturing company making numbers of products within tolerance specifications with skilled people that care… but there’s a quota to be met.

Anyone have a better idea?

Boomer :Fire:

[MakeMineA10mm]

FWIW, I think this is very good thinking. The only addition I would suggest is that the wording of Lee's note says that their tolerance is +0.000" to +0.003", so we must be careful that we are specifying the minimum diameter we will accept in the drawings we send to Lee.

I know you know that, just wanting to say it for clarity/others.

[Boomer Mikey]

Their tolerance is -0.000" to +0.003".

Lee wants a mimimum cavity size value like 0.357" that they will apply their -0.000 to +0.003 tolerance standard to.

For our purposes with Cast Boolits I would spec a .360" boolit at a minimum cavity size of 0.360" expecting boolits to fall from the molds between 0.3593" and 0.3613" using wheel weight alloy. Most likely they will be between 0.3603" and 0.3613" with a typically larger production mold cavity.

Boomer :Fire:

[45 2.1]

I've heard, from another source from a conversation over the phone, that "Pat" said that they could hold + or - 0.001" on Custom orders. It might be a good thing if we could get that confirmed in an e-mail from him.

[MakeMineA10mm]

And then the question becomes, if Pat said '+/-0.001",' does that mean he really was sneaking 3-thousandths in there? (-0.001" from specified dia., -0.00" from specified diameter, and +0.001" from specified dia.) That still gives the 3-thousandths range of bullet sizes... All still very confusing...

I think it would behoove us as a group to really pin Pat down on how he wants us to specify these things, so we can get the closest to what we want. I'm sure he'll try to wriggle out of that as much as possible, to give himself lee-way to sell moulds that are more out-of-spec than desired, but if it means losing a few thousand moulds a year, maybe he'll consider listening to us....

On the other hand, we can just go with what Mike said above. If the moulds generally turn out on the larger-size of the middle of the range of tolerance, we could compensate for that in our specified size. Now, the problem COULD come if Lee actually hit the mark, and the moulds come right at spec. By playing the game suggested, we would then have a mould that was .001" undersize or so... (I guess that's the one case for "agressive lapping"?) :roll:

The one "nice" aspect of the way Pat/Lee described their tolerence range as -0.000" to +0.003", is that the mould designer can specify an exact size that Lee is implying that they can guarantee it will not be smaller than... (It may be 3-thousandths bigger, but it will certainly not be smaller than @ -0.000" as their bottom tolerance limit.)

[Boomer Mikey]

IMHO the best way to do this is to have the bullet designer draw the bullet to dimensions desired and specify mold cavity minimum dimensions in your attached cover letter. Those minimum mold cavity dimensions should include an allowance for alloy shrink to the nearest thousandth including consideration for intended use. Some will want a 0.XXX" bullet not smaller than 0.XXX" and others will want a 0.XXX" bullet not larger than 0.XXX".

I spoke with Pat again today and I wanted to submit a minimum mold cavity size of 0.3597" and was told they only accept dimensions to the nearest thousandth.

In this case I specified 0.360" as minimum mold cavity size. If they hit the mark and produce 0.360" mold cavities linotype will produce 0.360" bullets and wheel weight alloy will deliver 0.3593" bullets. If they are 0.003" larger we'll get 0.3623" bullets with wheel weight alloy. These should work well with most 357's out there since manufacturers seem to make every chamber oversize nowdays.

For 44's; in particular, the 444 Marlin, I want a "fat" bullet as many of these rifles average a groove diameter in the 0.433" range. I'll specify a minimum cavity size of 0.434" so the smallest bullet to drop from the molds would be 0.4331". If the intended use was for revolvers and nominal groove size 44 rifles I would use 0.432" for the minimum mold cavity diameter to obtain bullets no smaller than 0.4311".

I'm sure Lee can maintain 0.001" with their most skilled craftsmen and best quality machines but I don't think you'll ever get a letter stating they'll do that with any custom order submitted. If you were a good friend of the boss or had a long term relationship with the owner you might get the preferential treatment of having your orders assigned to one of the best machinists in the shop who can make Bator 22 cal molds within 0.001".


Boomer :Fire:

[targetshootr]

The 429421 I sent back was dropping boolits from certain cavities at .445. Wonder why they bother worrying about such teensy specs.

[CSH]

I asked this question (cavity specs vs. bullet specs) last Nov in a thread for the 360-180 group buy. Has Lee changed their requirement for drawings that are submitted?

Originally Posted by CSH Nov 19, 2006


Boomer, have you discussed with 45 2.1 about sending specs for cut cavity dimensions on the sheet that is sent to Lee? I ask because there have been problems in specifying bullet diameter because of Lee's clause to be within +/- .003". It's my understanding that they can be held more accountable if they have to machine cavity specs.

Response from 45 2.1 Nov 19, 2006


Cut cavity dimensions got us molds that were grossly oversize from other buys with other people running them. I don't think you want that here. Things have been running OK on the last few buys the way we have been doing it.

[BABore]

Boomer Mike,

I'm not familiar with the RCBS cast book. Do they state the mold material that they get those shrink values from. As far as I know, RCBS only makes iron molds. Iron and aluminum have different thermal rates of expansion. While the alloy's % shrink should be the same, cavity growth will be different.

Those shrinkage values are similar to what I see in aluminum molds I make, sometimes. I have seen some cases of zero shrinkage and some that go a couple of thousandths. It seems to be influenced by bullet design somewhat. I know that the lead alloy should shrink by the same percentage, no matter what. It just seems that everytime I get it figgered out, I get an anomally.

I've found that it's a cast iron bitch to cherry cut a cavity to drop a bullet dead nuts on. Best I've done is 0.0005" and it took a couple trys by regrinding a cherry. Getting them to +/- 0.001 is childsplay. I just go a little big and size, less hastle.

[45 2.1]

I asked this question (cavity specs vs. bullet specs) last Nov in a thread for the 360-180 group buy. Has Lee changed their requirement for drawings that are submitted?

Originally Posted by CSH Nov 19, 2006


Response from 45 2.1 Nov 19, 2006

Yes, they have somewhat, and they're not being consistent about what they turn out. that makes guessing what they're going to do much more difficult.

[Boomer Mikey]

I'm worried about getting molds like the recent 429421 where 0.437" bullets are dropping with my 50/50 ww/lino mix and I'm afraid I've gotten that little bit of knowledge that's close to making me "dangerous".

A definitive minimum mold cavity dimension stated with the order gives us more control over results and its obvious Lee Precision wants custom mold orders submitted this way. If the minimum cavity dimension isn't included there's an open door to disclaim responsibility for the results.

Telling Lee Precision to make molds that drop bullets at 0.XXX" with wheel weight alloy is what we want to do but a responsibility Lee Precision isn't willing to accept because of variables they consider beyond their control. Lee is willing to make a mold cavity within -0.000" to +0.003".

There are mold makers that deliver exactly what we want. These craftsmen are typically one man operations with the experience to know exactly what works, what doesn't, and why. They share a passion with us for what we want to accomplish with the ability to make things happen.

You can't manufacture that on an assembly line,

Boomer :Fire