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I wanted to make a token for daughter to take to college with her when she starts Mississippi State this month. So I carved a mold in 1/2 MDF and bought a pound of pewter from ebay.
The first batch of pewter was almost impossible to melt at 750 deg F it was still not fully molten. After an hour with the propane torch it was ready to pour but it solidified when I tried to pour it. Made a new mold and tried again with the same result. Lesson 1 - Be sure you are using R92 Pewter, it will melt at a very reasonable 550 deg F
So I ordered a pound of R92 from ebay. It melted great, I poured it into the mold and discovered that I needed about a quarter pound more. Lesson 2 - Be sure you have more metal than you need
I ordered another pound of R92, made a fourth mold and everything seemed perfect till I opened the mold and discovered the top and bottom were not perfectly aligned (some how while editing the design before making the 4th mold I had moved the top part a quarter inch on the material. Lesson 3 - Check your design for alignment before carving.
I made another mold, melted 1.25 lbs of R92 and everything worked like it was supposed to. Lesson 4 - Have lots of patience
If I had to do it again, I think I would pour a flat rectangle of Pewter and just machine the design into it.
Start with CAD software that is able to do vcarving and has the ability to produce a mirror image of your final design.
30 Degree vbits and .5mm Tapered endmill are really useful to get the fine detail. You will also need the pewter ingots and a cast iron melting pot you can melt and pour the pewter from. I tried a stainless steel container first and it did not have enough mass to keep the pewter molten while I poured it, so I highly recommend the big heavy cast iron container.
Draw a square that will be the size of your mold (so your design can fit inside)
Draw the front and back of your medallion being sure to keep the shape centered in the mold square for both sides. Remember you will screwing the two sides of your mold together and if the shapes do not perfectly align it is going to be unusable.
Once you have completed the drawings you will need to use the mirror tool of your software to reverse the images so you are carving the mirror image. Be extra careful to be sure you do not misalign the front or back image when you reverse them.
Add a shape on both sides that will be pocketed out to make the fill tube that the molten metal will be poured into. These shapes also need to exactly align on front and back.
So after step 6 you should have a design all laid out ready to start making toolpaths
Now you are ready to design your toolpaths. The first cuts you will want to make are the pockets from the outside shapes of your object. For mine that is the outside circle. I wanted the overall thickness of the medallion to be .25 inches so each side is pocked .125 deep. Looking back, .25 inches thick may be a bit much, if I did it again I would reduce the thickness to .15 or .2 at the most.
You just need to be very careful that your object is thick enough for all the inset design element you have on the front and back. For example if you want text to be .1 inch deep on the front and back then you better make the thickness at least .25
When making the initial pockets you need to decide if you want the text or other design elements to stand out from the surface or to be “carved” into the surface. If you want the text to be set into the surface you must carve the mold so that the text is left standing above the surface. To do this I selected the circle and the text for the pocket toolpath. Doing that forced the toolpath to cut away all the material except the text letters (which were left .125 above the pocket bottom)
If you want the text to stand out from the final metal product you will carve the text into the bottom of the pocket you cut. For mine this means I set the start depth on the front side text to .125 for the vcarve toolpath.
Lesson learned: It is much (and I mean a lot) easier to polish your final product if all the text and design elements are set into the surface (like on the back of mine)
Carve your mold into your MDF, be sure you carve some alignment holes, I carved four .125 holes in each side that I used to align the sides. I then was able to use the holes to screw the sides together.
10 Clean up the mold, be super sure you have removed all the fuzzies and have cleaned out all the text throughly. The molten pewter will make an exact copy (fuzzies and all) of your mold. I used these super useful small files and then a dremel with a scotchbright wheel and it did a great job
Once your mold is really clean (compressed air is your friend) you are ready to apply a very small amount of baby powder to act as a release agent. Do not just pour the power over the mold, I found that putting a small amount of power into an old sock and then “patting” the sock about a foot above each side will distribute a very fine dusting (less is more in this case)
Now align and secure the two sides together. I used the alignment holes with a few of my .125 bits acting as pins to get everything aligned and then ran some screws into each of the four holes. I also used two wood clamps to be sure the two sides were really sealed against each other. I had learned from a prior try that the molten metal will pour out of your mold though even the tiniest of gaps (making a dangerous mess) so it is better to use more clamps than you think you need.
The fun part! put your pewter into the cast iron melting pot (small chunks melt faster than a large block). I simply put my melting pot inside my outside gas grill with two of the burners set to high. The pewter was molten in about 15 minutes.
If you see some dirty looking stuff floating on the top of your nice liquid pewter use a stainless steel spoon to pull it off. It will stick to the spoon really well (you will never get it off the spoon, so don’t tell your wife you used a spoon).
Place the mold someplace safe where a little molten pewter will not hurt anything. Be sure the mold is standing up straight and is very stable. Get the best oven mitt you can find and grab the melting pot and pour the metal into the mold with one continuous pour until the metal is even with the top of the mold.
Tap the mold to be sure the metal is getting everywhere it needs to be then let it sit for half an hour to cool (or do what I did and open the mold in five minutes and burn your fingers).
Clean up the finished product. I used 300 grit sandpaper on a belt sander to to the bulk of the work, then I used 500 grit followed by 1000 wet paper. After the 1000 it looks pretty good, but you will still be able to see very fine scratches. Using the dremel with a polishing tool and the red polishing compound gave me a really nice mirror finish. Then I used some comet powder cleaner and an old toothbrush to clean it up.
I am sure other may have better ways to do this, I was learning while doing and I made lots of mistakes, but in the end it all worked out pretty well.
Oh wow! Very cool. Maybe we could do a meetup sometime. Always good to know someone in your area that is using the same equipment, doing sign making, etc… Luckily my wife is really enjoying it so far as well and she is now really interested in getting a scroll saw!
Ha! Well, that would be for my wife, not me!
I think she feels like she would be more in control and not be intimidated - and she would feel free to use it whenever she wanted. As for the X-Carve, she’s getting good at doing design stuff, and very familiar with Easel design, but she is not too interested in getting into the detail of messing with the router, bit changes, etc…
I’m thrilled she wants to get into creating stuff with a scroll saw!
Maybe, it depends on how the release works, some of the tiny letters broke on my mold when I pulled the metal out. But I was not being particularly careful when I separated them. I have seen others on-line that have been able to use their MDF mold two or three times.
I think that if you wanted to make many copies you would be better making a silicon mold from the MDF first and then use the silicon mold to make your copies
Thanks, BTW I am in Milledgeville so it looks like we may have our own small group of X-Carvers here in GA. I may pick your brain more later on. I still have to put mine together, I just got it a month ago. So looking forward to start my projects and I really liked your medallion idea.
Anybody doing 3D Printing, then make a two-sided mold w/Max-60. then pouring pewter. I am creating on Tinkercad, print 3D design in extra fine, PLA, then making a top sided mold, and pour pewter pendants and jewelry. Learning a lot on Inventables!
