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First Steam engine Question

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Active Member
Active Member
Aug 31, 2014
File 2017-04-20, 09 06 23.jpeg
I am trying my hand at my first Wobbler Steam Engine. I made the Cylinder from 25mm Alu and drilled a 13mm hole for the piston about 6mm off center. Now I would like to mill a flat on the side of the Cylinder for the Inlet and Exhaust ports as well as the pivot point. I have to line the Cylinder up in the Milling Vice that the Flat and the 13mm hole are perpendicular. I tried eyeballing it in the vice but I would like to do it more accurately, but for the death of me I cannot find a way to do it. What would be the easiest?


Active User
H-M Supporter-Premium Member
Dec 20, 2012
I'll take a shot at this and the guys can come along and tell you the right way to do it.

I think I would turn a plug from Delrin to be a line to line fit (OD of plug and ID of bore are equal) for the bore. I would attach/screw the Delrin plug to a flat piece of stock so the bottom of said stock is below the bottom of the round work piece when assembled. Then I would put the plug into the bore, drop the whole thing in the vise and let the bottom of the flat sit on the bottom of the vise. With an indicator, I would tap the work one way or the other to get the highest elevation at the top. That should get you on center. Clamp it all down tight and mill the flat.

There is probably an easier way but its late and I can't think of one.


HM Shop Foreman
Staff member
H-M Supporter - Sustaining Member
Oct 21, 2012
Ideally, the flat should have been milled first, but since you drilled the cylinder bore first, other methods will need to be utilized. Mikey's idea should do the trick and should be as good a method as any.


Active Member
Active Member
Jan 11, 2014
That is a tough one maybe.

So yiu have a round part with a bore off center and it needs a cross drilled hole as well as a flat side.

Make a rod a snug fit to the bore and several inches longer so it protrudes a bit.

With a X block or vise you can lay the part in the vise with the rod then rotate until rod is highest or lowest point and measure with dial indicator in drill chuck.

If flat goes on thickest side then rotate until rod is at lowest point.

Now mill off the flat side.

Now rotate until flat side is against jaw and then drill cross hole.

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