A Lathe for my grandson (part 1)

Making a 1/12 scale model lathe

    metal
    machining
Thu Jul 13 2023

Of my three kids, only daughter #1 seems to have acquired my passion for woodworking, and none have yet expressed an interest in machining. I’ve decided to start indoctrinating grandson #1 into the mystical arts of machine tools. Somebody needs to inherit all my metalworking equipment!

Though I hardly believe it, my grandson is already three years old. Some might think that a three year old is unlikely to appreciate a model lathe that he probably won’t be allowed to touch, but my plan is to build a machine tool every year until I’ve made him an entire 1/12 scale machine shop. By that point, he’ll probably be almost a teenager and will hopefully enjoy playing with them.

I bought the castings (actually a full kit including raw stock) from PM research. Here’s what it will look like when complete (though I expect to paint mine something other than gray):

PM Research Engine Lathe

It’s a very nice kit, with cast aluminum parts and everything you need to build the lathe (sans a working lathe, vertical mill, and assorted tooling):

PM Research Engine Lathe Kit
PM Research Engine Lathe Kit

This will hopefully be a fairly straightforward build, as I’m pretty much following Joe Pieczynski’s outstanding build series exactly. Any deviations are most likely due to my misunderstanding or differences in available tooling.

In particular, I decided to follow Joe’s excellent suggestion to start with the smallest stuff to build confidence. When I finally get to some of the larger (!) castings and full assemblies it will be like dessert.

Here’s the first part I completed, the old-fashioned rocker style toolpost:

Toolpost
Toolpost

It’s hard to express just how tiny some of these parts really are:

Toolpost with pencil for scale
Toolpost with pencil for scale

Here’s the completed toolpost assembly. Note that this is a working model! I should be able to grind a cutting tool and actually turn parts in this thing when I’m done. I was pretty proud of myself for boring the countersink hole precisely in the tee-slot base such that the toolpost itself is recessed slightly. There is a slight mismatch in the radius of the rocker and the dish, but this was some fiddly work!

Toolpost assembly
Toolpost assembly

Next up were the handles and handwheels for the compound, cross-slide, and tailstock.

I made the square hole in the compound handle with needle files before realizing I needed to make two more square holes exactly 0.100” X 0.100”. That was fiddly enough work that I went ahead and made a dedicated broach:

Broach for making square holes
Broach for making square holes

I made it from O1 tool steel, coated it in boric acid to prevent oxidation, heated it to cherry red, then quenched it in oil to harden it. I then tempered it with a torch to a light straw color. Hardening it was probably unnecessary since the parts are aluminum, but I might use it again someday on something harder.

Once the broach was made, the handles were pretty straightforward (if fiddly):

Compound Handle
Compound Handle
Cross-slide and tailstock handles
Cross-slide and tailstock handles

That’s as far as I’ve gotten so far. I’ll post more updates as I progress.