I have successfully lapped out bullet molds or parts of bullet molds in the past but never an aluminum one. I now want to take advantage of other people's experience for lapping out an aluminum mold -- especially someone who has experience with both types of materials.
I would appreciate any advice. How is it different from working on ones of iron or steel, if at all? Different grits? What to watch for? Whatever. Thanks.
John
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I have used the cast slug with a hex nut cast onto the slug method. Turning is then easy with a wrench. I have used simple dental flours of pumice and liquid dish-soap as the lapping medium as aluminum is much easier to cut than steel. Also dish-soap easily rinses out for trial casting to check progress.
Gary
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Thanks Gary that is helpful.
All I have for grits are valve lapping compounds (220 to 1,200) in some kind of oil so if I am unable to get reliable results with swaging to measure (See the Weet method and my question under “Expanding Mold Cavities” topic) having the grit in soap instead of oil would save a lot to time cleaning molds.
Where can I obtain dental flours of pumice and does it come in different grades? If so what grade do you use.
John
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john ... i use an aerosol brake cleaner to clean instantly all kinds of oily/greasy/chippy messes ... from NAPA store; can't remember brand , maybe crc . mine is the clear stuff, not milky. probably a health hazard, so use caution.
with this cleaner you can use your oily grits. 250 grit sounds about right to get to your diameter.
next best is Dawn dish soap solution ...in squirt bottle ( house plant squirter ).
ken
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Better pharmacies and compounding pharmacies will have Flours of Pumice. The name itself is a particle size designation. If the label reads Flours of Pumice it is the correct grit for me for the job I described above.
Some specialty woodworking tool supply businesses will also stock Flours of Pumice as it is also used in fine wood finishing projects.
Professional Dental supply sources will have Flours of Pumice.
There are many internet sources for Flours of Pumice that are found through your favorite search engine online.
Even Amazon has it:
Gary
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Practice on one cavity only until you think you have process down pat. I am sure onondaga's hex nut method will work verygood and should work using harder alloys, but be careful to not let hex nuts damage surface while spinning. Damage can be sanded off on flat surface. A pure lead bullet shrinks more than harder alloys and will allow more clearance between bullet, 220 compound and mold. This extra clearance will allow bullet to spin more easily. A very small drop of oil will help cut better
Open mold halves and apply a very small amount of 220-320 lapping compound using tooth pick to area that you want to enlarge. When closing mold halves together, be sure no compound squeezes out and preventing halves from closing all the way. It can damage mold If mold halves open during lapping, so clamp mold halves together. Do not put any compound in and around gas check area? This will enlarge and cause fins at base. Open mold, clean well and repeat until desired diameter is reached.
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It's different is so much that you are dealing with a much softer metal so you must take care not to over do the job.
What I found enormously helpful when I lapped an alum mould was first taking a cast of each cavity in sulphur and measuring it. Now the sulphur will not be the same girth as your Pb alloy BUT it creates a nice baseline to lap from. As I progressed I could lap, clean the mould and take another cast without having to go through the heating up, cooling down process. I knew how big the sulphur bullets were and that I wanted to open up the mould 1.5 thou so away I went until the sulphur casts matched the net gain.
Cheers from New Zealand
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John, Just remember there is aluminum and aluminum. I have lapped out two Lee moulds with JB bore compound quickly. An NEI took 1000 grit Clover for 10 turns, then JB. FWIW, Ric
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Using a brass hex nut along with some type of fiber spacer between mould and hex nut should work verygood. Preheat everything so that tin/lead alloy will solder to hex nut. Bottom pour pot will help make job lots easier. Brass hex nuts can be purchased at the hardware store.
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Farm boy from Illinois, living in the magical Pacific Northwest
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The coarse Wheeler 220 fire lapping lapping compound will cut faster and not leave heavy scratch marks. Maybe you can imbed compound on lead bullet before lapping mold, much like imbedding bullets before fire lapping. This is done by rolling bullet in compound between two small steel plates.
Spray mold with light oil before closing and lapping. The oil really helps cut better.
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Thanks to all for the many helpful suggestions. I will start lapping this afternoon and put some of them into use. John
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As anybody following this thread knows I received recommendations for lapping compound from 220 to very very fine for my aluminum mold and warnings about overdoing it. So I tried something in the middle -- 400 and went easy. This stuff is from the fire lapping kits of lapping compound that Merrill Martin passed out to interested shooters willing to try fire lapping and report the results back 20-25 years ago.
I tried one lap for about 40 turns, stopping and redoing the knurlng and reloading with lapping grit twice. This involved stopping after a few turns (two or three times) and cleaning the mold faces until the faces closed completely. Washed with CRC (clear) brake cleaner and little tube to get it to the right place under pressure swaged with clean q tip and pressure washed again. Bullets had some wrinkles that most would discard but gave reliable measurement on several bullets. I could see no diameter increase from the bullets I had cast earlier for a control either in line with the parting line or perpendicular to it.
Second try, this time with 220 grit. Same procedure, almost same result almost -- maybe .0001-2” diameter increase.
Bullets for laps have a hardness of 13-14 by LBT test method and relieved by lathe turning everywhere except the parallel nose which I would like to have larger and the nose and rear band for bearings to keep the lap straight. My results so far are radically different that what others have reported for aluminum molds as being easy to remove material. Maybe NOE uses a bullet proof aluminum alloy and heat treat? Could my gritty feeling lapping compound not be cutting. I will keep at it but so far I can't see that this aluminum mold is any easier to lap than the steel and iron ones I have lapped in the past.
Any and all suggestions appreciated.
John
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Interesting. I usually get about 0.001” in 50 revolutions. I would suspect lapping compound bad or weak grip strength (smile). Ric
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I believe the radically different results you got are specifically related to the lathe relieving of the slug that you mention.
The relieved area gives the abrasive compound a place to flow to. Try new slugs with no relief cut and concentrate more on applying the abrasive compound to the areas you wish cut.
Your open mold flush is sufficient but when replacing the slug with abrasive compound on it, Close the mold very gently at the start of rotating the slug. Then gently increase mold handle squeeze while turning the slug. You should definitely feel the abrasive cutting the Aluminum by the amount of resistance the slug turning has for the first 5 or so turns. I can tell if I have the right amount of abrasive paste in there at that moment because squeezing the mold handles will act like a brake if your squeeze is too sudden or too hard. Gently bring pressure as you turn the slug.
The method is very specific to get it to work for me. I believe any relieved areas will allow the abrasive to flow away from the area you desire to cut. A relieved area on the honing slug introduces a void for the abrasive to flow into. This takes away the cutting power in the desired area.
Good luck, Try again.
Gary
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Farm boy from Illinois, living in the magical Pacific Northwest
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Thanks again for the additional replies.
Although the lapping compound feels gritty and I have lapped iron molds with it I may try another.
There is no lapping compound flowing to the relieved portions of the lap. The compound is black and there is no sign of it on the shiny relived parts of the lap after lapping. My procedure is what Gary describes in the third paragraph of hie post #15.
I will try again today maybe with even less oil in the lapping compound and more knurling between tries and report back.
John
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I acknowledge and have observed the Venturi Principle being applied when a mold is closed with a honing slug and an abrasive paste. The abrasive paste will flow to a more open space, like your relief area, where there is less pressure. It is just physics John, not an argument.
Viscosity of the abrasive paste will effect how obviously the principle is observed but viscosity will not negate the Venturi Principle.
Also, I just prefer a dish soap media for the abrasive for the simple reason that dish soap rinses out easily with water and a petroleum media requires a stinkier solvent cleaning. A running faucet is pretty simple to remove soap and an abrasive grit so a mold will close.
Gary
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I used a cordless drill and wood screw to spin bullet (not easy). I also used Clover fine valve lapping compound. This cut iron mold quickly. I also used the Wheeler 220 compound to enlarge a NOE 22 caliber 52gr RCBS clone. Sorry your 220 grit compound did not work. Atleast you have not destroyed the mold cavity....YET. Be very careful. You will get it. Are you trying to enlarge the bore ride section? I have a NOE 3 cavity version of your 80gr design. Maybe I can enlarge one of the cavities and send you samples.
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I tried it again this afternoon. More knurling and more careful lapping got the job done. I guess I was just impatient after hearing the warnings about going too fast with my first aluminum mold lapping attempt. The bore riding nose in one cavity is now .0008” larger in diameter which is about what I wanted to try. I will check fit and also how it shoots before doing more or lapping other cavities.
Gary, I don't want to argue either and I certainly respect physics but since you brought it up I have to disagree about the venturi effect being involved. The conditions for the venturi effect are simply not present here. The venturi effect is the reduction in pressure when a fluid flows through a constricted place in the pipe. There is no flow and no pipe nor anything like continuous flow in a pipe involved in lapping. If the lapping compound had migrated (which it didn't) to the more open space where I relieved the slug the straightforward explanation you mentioned in your #15 post of it just being squeezed out by simple pressure into the empty space would be a better explanation.
I do agree with you that soap and water would be a better carrier for the grit but unfortunately the stuff came in an oil base and I didn't have that choice. Thanks again to all who helped out and your patience while I timidly stumbled around with this. I got a little spooked when the first attempts had so little effect.
John
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Keith, Yes, I am just enlarging the nose. I am actually working on my noe 22570 RN mold. Thought I would get the feel of doing it before modifying the 80 grain mold. I hope to eventually get better accuracy with a nose that fits my rifle better. Thanks for the offer but I guess I got excited too soon. I just expected more action. Is the Wheeler 220 stuff just the grit? If so I am going to get some. It sure would be nice to just be able to wash out the mold with water as Gary suggest. John---------
I used a cordless drill and wood screw to spin bullet (not easy). I also used Clover fine valve lapping compound. This cut iron mold quickly. I also used the Wheeler 220 compound to enlarge a NOE 22 caliber 52gr RCBS clone.
Sorry your 220 grit compound did not work. Atleast you have not destroyed the mold cavity....YET. Be very careful. You will get it.
Are you trying to enlarge the bore ride section? I have a NOE 3 cavity version of your 80gr design. Maybe I can enlarge one of the cavities and send you samples.
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wimilkman
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Tom Acheson
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Aaron
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BRatigan
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MarkinEllensburg
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porthos
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