Making Lock Waxes — Waxes are Complete

[Randall Steffy]

Silky,
PM me what thickness you are hoping to get. Perhaps I can help you out. Freeman only sells box lots, and that could be $100+.

[silky]

While waiting on a shipment of silicone in order to make the last molds, today I fabricated a top jaw screw to mold. I believe it’s very important to use authentic 18th Century period methods and materials whenever possible; sticking to that approach, I chucked into the drill press a piece of clear polyacrylic rod I had laying around and went about shaping it, using the original as a guide. The shank portion is just a few thousandths thicker than 1/4” so after shrinkage, it should require minimal tweaking to fit a standard tap-n-die set, and is plenty long to chuck into a lathe with room to work.

I think it turned out well. It was certainly fun to make.

[rich pierce]

It’s all fun so far!    Keep the updates coming.

[Jim Kibler]

A top jaw screw generally requires more work to cast than to just make one out of bar, even without a lathe.

[Clint]

Silky,You have a nice looking bunch of waxes. Are you going to consider selling casting sets to offset your costs?

[silky]

Thanks, Clint. Yes, I plan to make some available for that reason and to get another lock “out there.” But I want to make sure they’re quality, first, so I don’t sell folks a bag of steel garbage. If all goes well, I’ll update this post when they’re available.

[silky]

Looking for a little help, please…

I molded the final lock plate model (.17” thick) and now the final waxes are ~.03-.04” thinner, resulting in plate thickness around .13”. Do you think it’s the wax or the silicone mold shrinking that much? If so, any recommendations on how to proceed? I understand the metal will shrink a further 2-4% during investment casting. The original is ~.15-16”.

How long do you guys wait to open the filled mold? Maybe it needs to more time in the mold to mitigate shrinkage during hardening?

I knew there would be some shrinkage in this process but losing almost 25% in thickness has me thinking I made a mistake somewhere. I thickened the plate in anticipation but this seems too much.

Thanks!

- Tom

[44-henry]

That seems very excessive to me. I just measured one of my injection molds and a wax shot from a small drawer pull I produced in a previous batch using standard pink injection wax.

The mold cavity measures 1.285" across, and the corresponding wax model measures 1.265", which results in approximately 1.6% shrinkage in width.
For thickness, the cavity measures 0.276", and the wax comes in at 0.273"—about 1.1% shrinkage.

So overall, I’m seeing just over 1% shrinkage in both directions, which is right in line with what I’d expect from this process.

That being said, I machined my mold cavity on a Haas mill and intentionally oversized it to account for both wax shrinkage and the expected metal shrinkage during casting. When working from original parts, you lose that level of control and that has always been a limitation of making molds from existing parts, but you should still be able to get a lot closer than what you stated.

One thing you might try is enlarging your sprues. As the wax cools, it naturally shrinks, and if there’s no supply of fresh material to feed into the cavity you will have excessive shrinkage. That sounds like what you’re seeing. When I make molds, I size the sprues carefully and often include additional material reservoirs to help compensate for shrinkage during cooling. This can make a significant difference in achieving consistent, accurate wax patterns. Also, the temperature of your wax is critical. It takes some time and experimentation to get these things sorted out.

[Clint]

I agree with 44 henry about the sprue size. For sand casting in brass, I always add a lug to the farthest part of the pattern from the sprue to act as a reserve pool of molten metal. That pool will help feed the end of the casting as it cools and shrinks. Are you going to make the ceramic molds yourself? I have done it but the molds are their own animal and it tends to make a mess.

[Jim Kibler]

Higher wax temperature leads to more shrinkage.  Keep this as low as you can for the particular type of mold you are using.  Also, higher injection pressure helps.  Again, this is dependent on mold type.  Finally, keeping the wax open as the part is cooling can help as it creates a source for feed wax as long as the wax sprue or gate doesn't freeze off first.  We usually inject with a paste type wax at pretty high pressures using hard molds.  I've used silicone in the past, but it's been so many years I don't recall temperatures and pressures we used.  We definitely ran the wax at more of a liquid consistency and a lower pressure.

[silky]

44-Henry, Clint, Jim,

I went with your suggestions and the waxes are now consistently coming out only ~.01”, so let’s call it a win. I cut some crude reservoirs/vents in key places, and that got me closer in thickness  but not where I wanted it. So, the next round added to that change was dialing down the temp (~10-15 degrees cooler than the manufacturer’s recommendation)… good thickness but rippling/wavy surface texture. Finally, the win was complete by dialing up the pressure quite a bit (15 PSI on the gauge but that gauge is very suspect).

After the crucible that was me learning brass sand casting (pun intended), I should have known to add reservoirs. It’s fascinating how much goes on inside the mold between closing, filling, and opening.

Freeman’s website shows specs for each wax, and it was interesting that temperatures not much higher than melting result in much higher flow rates that decrease significantly as temperature increases. The recommended temp for this wax is 160-165 and success here was just a sludge below 150.

Clint, I plan to let the foundry take care of the investment. I’m happy to be at this point and know better than to push my luck.

Another question: regarding gates for the steel casting, do you recommend one or two on the lock plate? Seems most lock sets I have use one on each side of the pan. Again, no experience here and I’d prefer to add it myself instead of the foundry folks, if it’s necessary. And does the shape matter? The one on the plate is round (rod-like) but I have seen many rectangular.

Thanks a ton for your help with this. The lock plates are the last waxes then it will be time to turn wax into steel!

- Tom

[Clint]

Silky,
  The last blast to study gating would be to buy a TRS or a Chris Hirch lock set and study their gate/sprue size and locations

[silky]

Clint,

That’s a good point. There is some variation but it seems the lock plates similar to mine use two, so I’ll go with that. All other parts I made copied TRS locations, though most of mine are round in profile and theirs tend to be rectangular… so if that matters I can cut and replace but I’d like to avoid that if it doesn’t matter!

- Tom

[silky]

Just a minor update to share a technique that may be helpful to others. I strongly doubt this is a new discovery, though…

The original tumbler and sear are rough, so I purchased new machined ones that are very close but significantly thinner.  Sheet wax was too soft, even using a fresh X-acto blade, to maintain crisp corners and uniform thickness. So I tapped into my old scale model supplies and tried sheet styrene… couldn’t be happier! It’s attached to the part with thin super glue then cut and filed to shape — it files so nicely.  Now the tumbler and sear are ready to be molded.

The styrene and super glue are easily filed/sanded off when done.

Again, probably not original thought but I thought I’d share.

- Tom

[silky]

Life keeps getting in the way of this project, but over the last few weeks I have fabricated a new lock plate, cock, and frizzen using styrene sheet and files. I wasn’t totally happy with a number of the waxes molded from the original parts and modified waxes; that is largely the result of using a rather rough and beat up lock for this project. But it’s all good because this project is about learning skills and methods.

Big picture: super glue some sheet together, trace/draw the original part onto it, then get at it with files. Here are a few pictures of the frizzen from start to finish. With a complex shape like this, I found it most effective to build it in separate sub-assemblies then glue them together. To achieve symmetrical contours, a bonus of using glued-together sheet is that the seams present as light gray lines that act like contour lines on a map — it shows me three dimensions from a two-dimensional perspective. Look closely at the pic of the front of the frizzen and you’ll see those lines.

Superglue creates a perfect bond and essentially fuses styrene pieces together. It files like plastic, too, making it great for durable touch-up filler. The brown seams are actually colored super glue that is easier to see and file to shape.

Once I’m done with the new parts, I’ll airbrush a thin coat of scale modeling primer to reveal the areas requiring touch-up. Then mold and wax.

[rich pierce]

Creative approach. Seems like you’ll get nice clean parts this way.

[FlinterNick]

Good afternoon,

I’m working on waxes to be cast into a complete lock set. Searches here and abroad have answered most of my questions, but a few remain….

1. Any recommendations for good wax material?

2. Do the individual waxes themselves need vents during the investment casting process?

3. A pic or two of lock parts hanging on the tree would be very helpful!

4. I need to carve a new pan as the original is pretty eaten away from hard use and time. If I create a new pan in carving wax, can I just create copies with a mold then attach them to finished lock plate waxes? Or is it better to create a new master lock plate wax (with new pan) and cast it as one assembly? I’m leaning towards the first option because the lock has the name “BARBAR” engraved in it and I don’t want to lose the fidelity and detail of that engraving by molding, modifying, then molding that modified wax… or am I overthinking it?

5. Any best practices for plugging drilled holes in the master? I have messed around with clay and while effective, it’s a bit messy when trying to clean it up. So should I plug these holes in the master, or fill the final wax patterns with wax after making them?

I’m sure more questions will arise during the process. I’m doing this for fun and out of desire to learn the process. Thanks!

- Tom

Great job ! I’ve been pratcting some lost wax castings for a while now, getting some lessons from Jess Melot will be at the Rifle Shoppe in the Fall will be happy to share what I’ve learned.

Lately I’ve moved on from the latex molds to metal filled epoxy by smoothon Inc. The frames I’ve been attempting to mill from aluminum stock too, making the mold more sturdy under high pressures.

[silky]

Great job ! I’ve been pratcting some lost wax castings for a while now, getting some lessons from Jess Melot will be at the Rifle Shoppe in the Fall will be happy to share what I’ve learned.

Lately I’ve moved on from the latex molds to metal filled epoxy by smoothon Inc. The frames I’ve been attempting to mill from aluminum stock too, making the mold more sturdy under high pressures.

Thanks! I don’t think one could ask for better lessons in making lock molds than Jess Melot. Please do share what you learn!

So how do you make the two-part molds using the metal-filled epoxy? I have a little experience doing that with silicone RTV; one builds half the mold and uses sulfur-free clay to create the non-molded half (I think you probably know what I’m talking about?). Is it a similar process? Example pic attached.

[FlinterNick]

Great job ! I’ve been pratcting some lost wax castings for a while now, getting some lessons from Jess Melot will be at the Rifle Shoppe in the Fall will be happy to share what I’ve learned.

Lately I’ve moved on from the latex molds to metal filled epoxy by smoothon Inc. The frames I’ve been attempting to mill from aluminum stock too, making the mold more sturdy under high pressures.

Thanks! I don’t think one could ask for better lessons in making lock molds than Jess Melot. Please do share what you learn!

So how do you make the two-part molds using the metal-filled epoxy? I have a little experience doing that with silicone RTV; one builds half the mold and uses sulfur-free clay to create the non-molded half (I think you probably know what I’m talking about?). Is it a similar process? Example pic attached.

For the metal filed epoxy molds I use both wooden frames and aluminium. I mill out the center of the frame to the depth i need and cut a ferret at the top.

PVC piping does work for very small parts, cut the pipe into two Equal parts and they make a nice round mold or square one if you can find square PVC on Amazon.

Silicone or rubber molds provide very good details but are generally good for only a few waxes, i found they just don’t last very long.

the aluminum filled epoxy provides equal amounts of detail and with high pressures can make a very good part.

Your most complicated parts are thin springs and lock plates.

Top Jaw Screws if i mold I only mold the top.  I tap and weld (not solder) the top on to a 1/4 inch steel bar and cut the threads on a lathe.  I

[silky]

Thanks, Nick! How does it handle pieces with undercuts, or ones that at least require some manipulation to remove from the mold? I'm thinking of a lock plate with an integral pan as an example; it takes some bending and squeezing to extract the formed wax due to the shape of the pan.

- Tom

[44-henry]

Make the lockplate in a few pieces and join them together. If you have some CAD skills you can also 3D print your parts using castable resin. We do this a lot in our lab. While we have printers that cost thousands of dollars we have some Elegoos that cost only 3-400 and they print at resolutions and sizes that are more more than precise enough for this type of work.

[Hudnut]

One way of dealing with undercuts, etc., is to use slides in the mold.  Slides are pulled before the mold is opened to remove the wax. 
The pattern can also be made or built up to create draft to allow wax removal.  Cleanup of the castings will be required.

[silky]

So we finally have all the waxes made and ready to ship to the foundry. Most of the individual parts molded sharp and crisp, though I had some issues with the lock plate, particularly the pan. Slicing in air vents helped, but most of the waxes came out with minor distortions. I added wax worts to them individually so there is enough metal to file back to shape on the finished castings; it’s just not as satisfying as pumping out perfect waxes. A fair bit of flattening and filing should make a good frizzen-pan fit, so I’m not too concerned.

To pass on something I learned in hopes it may help someone on a similar project… one issue that gave me fits was the interior side of the lock plate surface cavitating, meaning it had a concave profile when viewed down the side. In the end, leaving the mold plugged into the injector for a full 60-90 seconds provided hot wax for the lock plate to keep sucking in as it cooled, resulting in perfectly flat surfaces. Without it, the wax would shrink inward, resulting in the concave surface.

I went back and made a new frizzen spring, leaving the finial as a large rectangle that can be filed to specific shapes. Similar locks in books and online show a number of shapes, so this will allow some customization of individual locks.

Speaking of those pictures, the black and white one below is from a British museum, showing a Lewis Barbar-made military musket dated to 1720. While the one shown has a more pronounced banana profile, the similarities to the one I modeled are strong, including the unique frizzen finial. So I think these castings will be good for early-to-mid 1700’s muskets of British origin, including so-called “Colonels’ Muskets.’ What are your thoughts?

Time to pack these well and get them on their way. I’m excited to see how they turn out!

- Tom

[Bob Roller]

I hope for every possible success in these endeavours.I was in the shop this morning and have had a Hawken cap lock that has been started since 2019.tt's a simple one with no half cock like most of the originals but with closer tolerances and better materials and I found out that standing at the bench making these or any thing else is no longer possible because of lower back spasms.I was hoping to make a few locks over a period of time but that won't happen.Leaving my wife alone in the house is another thing.She has a spinal curvature that is serious and if she falls that can be bad.She forgets to carry her cell phone and being hearing impaired is no help either.
Bob Roller

[rich pierce]

Sign me up, but I'll need a template.  I noticed that you haven't spotted the holes or planned to cast "in" some of the possible holes, like the square hole in the cock.