Cylinder Machining Order of Operations

I would lap last. Because a properly made and used lap will keep the bore round despite the port cutouts. This means that you can mill the ports and then file if need be to final shape. Care must be taken when deburring the cylinder side of the ports because the boring and lapping will only be removing a small amount of metal. The interrupted cut when boring may seem to be a bit of a pain but when filing the ports to get them to shape and smooth inside it will be easier if you don't need to worry so much about the edges being rounded over where the port intersects the bore. The lapping operation of course needs to leave the ports with sharp edges. Eric

What Eric says would work and does work for most people...But I'm not most people...Try this on for size for machining order...

1) machine bore 2) lap/hone bore to "rough" size...something on the order of .0015-.002 under final size 3) machine side ports/slots to completion 4) the VERY last step before fitting the piston is to finish hone/lap the bore

This order lets you have a little leeway in "damage" caused by cutting and deburring your side ports, allows you to true the bore back to round after cutting your ports, and allows you to leave pretty close to sharp corners where the ports meet the bore with a minimum of fuss.

Just a thought or three.

Mike

Yea, I think lapping last makes the most sense. I think drilling the slots first, then boring the cylinder, then lapping is probably the way to go -- but I've never done it before (or I wouldn't be a wannabe!).

Not to stop you from making a new cylinder, but I am curious, what would happen if one were to get a ball bearing the right diameter and press it through the cylinder? (Kind of like when they re-size brass cartrages prior to reloading.)

With the equipment I have in the shop right now? Probably a stuck ball bearing, possibly covered blood and lonely while I take a trip to the emergency room. I'm not sure that it wouldn't mangle the push end of the cylinder, even with the 'right' equipment.

I hadn't thought of ball-forming the old cylinder. If I were seriously interested in getting the engine working with the least work I'd be searching out a NOS COX cylinder/piston set. Or I'd be asking just how to go about honing, lapping or otherwise cutting the cylinder back to roundness so I could build a slightly oversized piston.

The truth of the matter is, however, that before I go cutting out the dozen or so different parts of a from-scratch working engine, I'd rather just try making the five needed for a cylinder/piston set.

The normal way to machine a cylinder such as you describe would be to rough machine the bore; finish machine the bypass areas and then finish machine the bore.

For finish machining you might look into adapting a Demril tool as a tool post grinder which would make it easy to grind the bore to finished size.

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

If I were to try, I think I would remove the crank shaft and piston fron the block and leave the cylinder attached.to the block. A chunk of pipe in the drill press to apply pressure top the ball and all the stuck ball and bleeding could probably be avoided.

Why not do both?

Some older Dremels fit snugly into a copper pipe cap or reducer that you can solder to a base.

My new Dremel mount is an upright rectangle of aluminum morticed into the compound slot and bored in the lathe to fit the nose of the tool. The tee slot clamp is a lawnmower wheel axle bolt which has a low- profile hex head. A carriage bolt with a washer pounded onto the square and cut flat on the sides works for larger tee slots.

The new Cox cylinder is for practice. Once I get this one working, and possibly the TD 09, then I'm planning on building an Owens Mate (see

look under "projects").

Eventually I want to build a 1/6 scale model A engine, to fly a 1/6 scale Pietenpol Air Camper. This may not happen until I retire, but it's an excuse to keep buying stuff for the machine shop. In the mean time I intend to have fun building engines.

An interesting site. However, I have to comment on something that I keep seeing in print that has been driving me nuts -- in the first article on building EDMs, they say it was a Russian invention.

It was not a Russian invention. That baloney was perpetuated by Charmilles EDM in the early '50s. It actually was invented by the predecessor to the US company Elox, who sold two of their servo-type tap-buster/square-hole-cutting eroders to the Soviet government two years before we entered WWII. The Soviets claim they invented it in the early years of the war.

Back in '77, when I wrote a lengthy article on EDMs for _American Machinist_, I studied the history in great detail, and read the translated papers by the Lazarenkos, who claimed the invention. They added some minor twists but it was basically the proto-Elox machine.

Just setting the record straight. d8-)

-- Ed Huntress

Send him an email. He's a good guy, and enough of an academic that an opposing view (particularly if you can back it with citations) will be meat and drink to him.

Well, that would be very tough. I could give him leads but my guess is they'd come up dry at this late date. I had access then to the McGraw-Hill library, which was full of historical metalworking books and the entire _American Machinist_ archives. I doubt if there is a complete set of those anywhere now, except, possibly, in the Library of Congress.

I'll take a look at my old article and see what it says. We didn't use references on those Special Reports, so I'd have to do it from memory.

-- Ed Huntress