Small simple turbine engine

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arnoldb:
:D I had a bit of shop time today. I was hoping to get the engine done, but time flies when one's having fun :lol:

First off, I cleaned some excess off with a 6mm ball nose mill. I've had the bare minimum experience with using ball nose mills, but it cuts surprisingly easy, and leaves a nice smooth finish to boot:

:palm: There's a very ugly spot to the left of the groove milled with the ball-nose; that happened last Sunday when the draw-bar on the collet chuck came loose. I was a bit slow hitting the E-stop on the mill... Fortunately it can be fixed; just a bit of effort needed.

Next I very roughly started hogging away some excess aluminium:

Rather than using the tooling plate for the next step, I centered the rotary table to the mill spindle and zeroed the X and Y dials taking care to remember in which direction for each axis I'd taken up backlash. Then I mounted the chuck adapter and 4-jaw on the RT. With a bit of 6mm rod to fit the workpiece bearing, I chucked it up; lightly touching each chuck jaw against the side of the workpiece, and then going round tightening each jaw just a little till things were clamped down properly. Not very accurate, but plenty good enough for the profiling I'm going to do:

Then I started profiling with a 6mm end mill again:

A considerable while later, things looked like this - with a 3mmx3mm step left around the profile:

Not pretty, but OK for now.

Then I used the 6mm ball nose mill to clean up the step - and lightly cut deeper against all the sides with it to clean up the poor finish from the previous step as well:

John kindly gave me some pointers on exhaust holes - Thank You!. I couldn't go exactly to his recommendations, as there is the matter of a screw that's in the way that I had to work around. I drilled the first hole with a center-cutting 4mm 2flute cutter:

The second one was done the same; but nearly in-line with the inlet port - barely missing the screw hole.

On my previous engine builds, I've been very lax about adding oil holes in the bearing blocks, but this one definitely needs it:

Then I spent a couple of hours with files, needle files, riffler files and emery paper to get rid of some of the tool marks:

::) Some latent insanity surfaced and I wondered what it would look like buffed up a bit. I'm not sure if I like it; I'll sleep on that tonight. If I want it buffed, I have to make a plan to get into all the little corners with a buff. That will require some careful work with the Dremel and perhaps lateral thinking. I might just give the whole thing a rub-down with some 600 or 800 emery to get back to the satin-like finish:

So, a lot of faffing around today - but some valuable exercise. I've not done a lot of profiling with the mill, so this is all new to me, but I'm fairly happy with the result. More practice needed though :dremel:

:beer:, Arnold

Bogstandard:
That is looking just fine Arnold.

If the finished engine runs as well as it looks, then you are onto a winner.

John

sbwhart:
Thats a nice bit of sculpting Arnold, :clap: :clap: :clap: :clap:

I prefer the satin finish but thats just me.

You'll have a great looking engine either way.

Stew

andyf:
Really nicely shaped!

Like Stew, I prefer satin finish (maybe with the rotor polished for contrast, as the cover will be transparent) but it isn't my engine.

If you want to try satin, polish it up really bright, wash in solvent, and then (no greasy fingers) dunk it in a solution of caustic soda/lye/sodium hydroxide and let it fizz for a minute. Experiment on a polished offcut first, to see if you like the effect.

Andy

John Hill:
Excellent project! Now I really am lusting for the day when I can buy my mill!

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