theperfessor
07-07-2010, 05:26 PM
I'll try to keep this short, but I need to provide some background information concerning the goal of a long term project I have been working on. Then I'm going to ask for some help from 3 or 4 of you so I can finish and document the current phase of the project. It will only require a few minutes of your time, and the end result will (hopefully) be of benefit to many of the people who frequent this site. If you're interested, read on.
I'm a machinist by training and a mechanical engineer by degree. I teach manufacturing courses at a state university, do some consulting and material testing, and have a small machine shop for doing subcontract work and building prototype machines.
A few years ago my interest was rekindled in bullet casting and reloading. I found this site, and gained an appreciation for the technical aspects of the process of casting bullets. I got a real education after reading many posts concerning the quality problems of various molds, and seeing some really innovative ideas on mold modifications and alterations. I also participated in several group buys until the wait time became unreasonable.
I decided that I could make multi-cavity bullet molds at least as good as any of the commercial vendors, and that making small lots of a custom product of the best quality might be a good way to supplement my income and keep me active when I retire in a few years. I laid out a rough plan for this, dividing it up into stages:
Stage 1: Determine the processes necessary to make a mold, develop the tooling, and cut a sample mold. Test the end result, and keep track of all the problems encountered throughout. I did this, and posted a link to the following article:
http://www.usi.edu/science/engineering/moldfixture/MakingBulletMolds.doc
Since publishing the article above I have made many changes and improvements. While not yet perfect, I can now manufacture the mold blanks accurately and relatively efficiently. I felt like I got things 90% right the first time, and now I've got things about 98% right. But I'm always looking for better ways to do things, so I'm still keeping track of problem areas.
Stage 2: Determine a testing process to enable actual empirical data to be gathered relating the actual size of a mold cavity to the resulting bullet size, and acquire the necessary instrumentation to perform the test. I realized that it would be necessary to be able to monitor and control temperatures accurately, so I built a dual PID temperature controller and posted this thread:
http://www.castboolits.gunloads.com/showthread.php?t=71208
I have made three 5-cavity molds, one each of 2024 aluminum, 7075 aluminum, and Dura-bar nodular iron. The cavity sizes are (roughly) 1/4”, 5/16”, 3/8”, 7/16”, and 1/2”. Each cavity was drilled 1/64” undersize and then reamed to nominal size. However, after examining the first mold, I was dissatisfied with the interior finish and so each cavity was bored out 0.005” to 0.020” oversize using a single point HSS tool. In order to be sure the mold and alloy are at the proper temperature, I put a band around each bullet with a little hook tool so that I can visually check the test slug for good fillout. See the pictures below for details.
The testing process will include three or four different alloys – almost pure lead (roof sheathing), straight WW, a Lyman #2 analog (9 lb WW +1 lb 50/50 solder), and possibly Linotype. These are the typical alloys available to the hobby caster and are materials I have at hand. I don't plan to buy pure materials from a vendor at this point, but I'm keeping that possibility open for later consideration. (Of course if a commercial vendor wanted to LOAN me some certified metals I would be glad to pay the postage both ways and return the extra materials at the conclusion of this test. And I would give credit in the report also.)
The test will be as follows:
1. Measure and record the diameter of each cavity in each mold at ambient temperature. I plan to measure the base band across the parting line with a small hole caliper micrometer.
2. Using a particular alloy, cast slugs at several different temperature ranges above the minimum needed for good fillout. I plan to preheat the mold first and then vary the casting furnace temperature to determine the minimum mold/alloy temperature for good fillout. I will record the furnace temperature, mold stabilization temperature and cycle time, based on how long it takes the sprue to freeze and not smear when cut. I do not plan to use any “assisted cooling” methods such as wet towels, etc. but I will have a fan blowing to provide some gentle air flow, mostly for fume control.
I plan to cast 25 or more slugs of each size at the various temperatures so I will have enough samples for a statistically valid test. Each slug will be measured at ambient temperature and the readings will be recorded and tabulated.
3. Do the math, write up the results, and publish in the public domain.
This is where I need a little help. One of the pieces of data I want to include is a BHN of the various materials. I do not have any hardness testing equipment. I would like to send three samples of each material to someone who can do a hardness test and who is willing to send me the results. I would like to know what machine you used and what the BHN number is for each sample. I can prepare the samples any way necessary and will pay the postage to get them to you. You can add them to your lead stock when you're done. It would be nice to have tests done on several different types of machines, to cover the range of equipment most used by hobby casters.
You will get full credit for your efforts in the report (by name, handle, or anonymously if you wish). I'll either post the report to Castboolits or put it on another site and post a link here. I plan to start the testing soon, but I might not finish it up (there will be a lot of work and time involved on my end) until the end of the year. I just want to line up some help early on.
Once I have this information available, I can move on the the next stage. The last real problem I can see is the need to improve my form cutters so I can make a tool of the exact profile necessary. I've been talking to a local shop and may have a line on a used Cincinnatti tool grinder. No big deal, I spent two years looking for a little shaper to cut vent lines in my molds and finally found one of those, and I can afford to be patient.
http://www.castboolits.gunloads.com/showthread.php?t=83273
Once get over the last hurdle, I should be able to reach my goal:
To make high quality multi-cavity bullet molds in a variety of materials that will drop a bullet of a specific size using a specific material when cast at a specific recommended temperature.
I'm a machinist by training and a mechanical engineer by degree. I teach manufacturing courses at a state university, do some consulting and material testing, and have a small machine shop for doing subcontract work and building prototype machines.
A few years ago my interest was rekindled in bullet casting and reloading. I found this site, and gained an appreciation for the technical aspects of the process of casting bullets. I got a real education after reading many posts concerning the quality problems of various molds, and seeing some really innovative ideas on mold modifications and alterations. I also participated in several group buys until the wait time became unreasonable.
I decided that I could make multi-cavity bullet molds at least as good as any of the commercial vendors, and that making small lots of a custom product of the best quality might be a good way to supplement my income and keep me active when I retire in a few years. I laid out a rough plan for this, dividing it up into stages:
Stage 1: Determine the processes necessary to make a mold, develop the tooling, and cut a sample mold. Test the end result, and keep track of all the problems encountered throughout. I did this, and posted a link to the following article:
http://www.usi.edu/science/engineering/moldfixture/MakingBulletMolds.doc
Since publishing the article above I have made many changes and improvements. While not yet perfect, I can now manufacture the mold blanks accurately and relatively efficiently. I felt like I got things 90% right the first time, and now I've got things about 98% right. But I'm always looking for better ways to do things, so I'm still keeping track of problem areas.
Stage 2: Determine a testing process to enable actual empirical data to be gathered relating the actual size of a mold cavity to the resulting bullet size, and acquire the necessary instrumentation to perform the test. I realized that it would be necessary to be able to monitor and control temperatures accurately, so I built a dual PID temperature controller and posted this thread:
http://www.castboolits.gunloads.com/showthread.php?t=71208
I have made three 5-cavity molds, one each of 2024 aluminum, 7075 aluminum, and Dura-bar nodular iron. The cavity sizes are (roughly) 1/4”, 5/16”, 3/8”, 7/16”, and 1/2”. Each cavity was drilled 1/64” undersize and then reamed to nominal size. However, after examining the first mold, I was dissatisfied with the interior finish and so each cavity was bored out 0.005” to 0.020” oversize using a single point HSS tool. In order to be sure the mold and alloy are at the proper temperature, I put a band around each bullet with a little hook tool so that I can visually check the test slug for good fillout. See the pictures below for details.
The testing process will include three or four different alloys – almost pure lead (roof sheathing), straight WW, a Lyman #2 analog (9 lb WW +1 lb 50/50 solder), and possibly Linotype. These are the typical alloys available to the hobby caster and are materials I have at hand. I don't plan to buy pure materials from a vendor at this point, but I'm keeping that possibility open for later consideration. (Of course if a commercial vendor wanted to LOAN me some certified metals I would be glad to pay the postage both ways and return the extra materials at the conclusion of this test. And I would give credit in the report also.)
The test will be as follows:
1. Measure and record the diameter of each cavity in each mold at ambient temperature. I plan to measure the base band across the parting line with a small hole caliper micrometer.
2. Using a particular alloy, cast slugs at several different temperature ranges above the minimum needed for good fillout. I plan to preheat the mold first and then vary the casting furnace temperature to determine the minimum mold/alloy temperature for good fillout. I will record the furnace temperature, mold stabilization temperature and cycle time, based on how long it takes the sprue to freeze and not smear when cut. I do not plan to use any “assisted cooling” methods such as wet towels, etc. but I will have a fan blowing to provide some gentle air flow, mostly for fume control.
I plan to cast 25 or more slugs of each size at the various temperatures so I will have enough samples for a statistically valid test. Each slug will be measured at ambient temperature and the readings will be recorded and tabulated.
3. Do the math, write up the results, and publish in the public domain.
This is where I need a little help. One of the pieces of data I want to include is a BHN of the various materials. I do not have any hardness testing equipment. I would like to send three samples of each material to someone who can do a hardness test and who is willing to send me the results. I would like to know what machine you used and what the BHN number is for each sample. I can prepare the samples any way necessary and will pay the postage to get them to you. You can add them to your lead stock when you're done. It would be nice to have tests done on several different types of machines, to cover the range of equipment most used by hobby casters.
You will get full credit for your efforts in the report (by name, handle, or anonymously if you wish). I'll either post the report to Castboolits or put it on another site and post a link here. I plan to start the testing soon, but I might not finish it up (there will be a lot of work and time involved on my end) until the end of the year. I just want to line up some help early on.
Once I have this information available, I can move on the the next stage. The last real problem I can see is the need to improve my form cutters so I can make a tool of the exact profile necessary. I've been talking to a local shop and may have a line on a used Cincinnatti tool grinder. No big deal, I spent two years looking for a little shaper to cut vent lines in my molds and finally found one of those, and I can afford to be patient.
http://www.castboolits.gunloads.com/showthread.php?t=83273
Once get over the last hurdle, I should be able to reach my goal:
To make high quality multi-cavity bullet molds in a variety of materials that will drop a bullet of a specific size using a specific material when cast at a specific recommended temperature.