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Gingery Lathe and Accessories
millwright:
Thanks for sharing this with us, Great to see what You have achieved. the pictures are excellent as well. Waiting for the next instalment.
John
Brass_Machine:
This is some pretty cool stuff!
I appreciate the walk through!
Eric
vtsteam:
Wow, didn't expect this much interest! Thank you all!
:mmr:
Here was a good day in molding -- three patterns finished and cast -- probably it was the weekend. Shown are the compound slide in the upper left, the compound swivel base at bottom, and the carriage apron, upper right.
The compound slide had some minor shrink cavities -- these were removed when filing it flat -- there was enough of a machining allowance to do it.
The compound swivel base has a steel cast-in rod which will be sawn off to leave a short dowel as a pivot. The base will get a slab of cold rolled steel attached to form the ways for the compound slide. The slot is where the compound leadscrew goes, the disk provides bearing surface for the swiveling motion and a clamping surface for the toe clips that clamp it in position when the desired angle is set. This is one of the more complicated patterns because of the draft in all parts including the slot, and the cast-in-place rod.
I felt like the lathe was really getting somewhere when I could cast 3 major pieces at a time. Of course all of these pieces needed to be filed and scraped, and needed gibs, gib screws, ways, etc to finish.
The carriage apron was very simple, but it accepts the most intricate casting of all, the leadscrew split nut. Unfortunately I didn't take any pictures of that one. But to give you an idea, you actually cast the threads of the split nut in place. You do this by placing a piece of the leadscrew threaded rod in the mold -- sooted of course to get it to release. In order for that to work, you also have to put the female threads in the wood pattern. This is done by using bondo with threaded rod coated with release agent. This is a very interesting pattern because of the unorthodox methods Dave Gingery used.
The threads came out well on my lathe -- if a little tight. For the half nut I used pot metal (zinc diecast) instead of aluminum, because it is harder and tougher. You can actually build the whole lathe out of that, instead of aluminum. But the filing and scraping will also be a lot tougher to accomplish.
The tightness of the split nut on my lathe was a result of the near zero thread clearance due to casting directly on a threaded rod. However with a little use, the leadscrew and the half nut both essentially lapped each other -- the hardware store threaded rod was a little rough to begin with, and in the process of running against the nut, the high spots were reduced, and likewise the clearance improved. Once that happened, wear and friction reduced leaving almost no backlash, and good fitting parts.
vtsteam:
Here I was beginning to make the tailstock pattern. This is the tailstock barrel being glued up on Vee blocks with a few aluminum "muffins" as weights. When you pour aluminum, usually (if you've calculated right) you have leftover aluminum. Pouring that into a muffin tin gives you some ingots for the next melt -- or gluing weights, as needed!
The barrel has two dowel ends here -- these are core prints -- they actually represent holes in your casting. Holes formed by cores always are the opposite of holes in patterns, they are represented as solids outside of the actual casting. Next picture will show why.
vtsteam:
Here is the actual tailstock mold ready to close up and pour.. The darker brown rod in the center is a baked sand core. The purpose of this core is to leave a hole in the casting. A steel rod wouldn't work here because the hole is too long. Even sooted up it would probably be impossible to drive out.
The baked sand core does leave a rough hole -- later to be bored out. The core is made up of sand, molasses water, and wheat wallpaper paste. It has a wire reinforcement inside, It is baked in a house oven at 350 degrees for about 20 minutes. The molasses makes it smell like cookies baking, so passes the domestic bliss test for do-ability indoors.
You can see the impression of the barrel I made in the step before. The core fits in the space left by the core prints we just talked about. This is why core prints actually represent a hole in a casting, even though they look like a solid in the wood pattern.
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