Elmer's Oscillating Cylinder Engine #42

[crueby]

As a fellow Sherline lathe/mill user, I applaud your ingenuity on setups - always interesting to come up with new ways to combine the parts on the machine to do bigger parts.   I notice you have the taller version of the toolpost, you need to add one of the headstock riser blocks to your wish list to let you turn larger diameters on the lathe. Clever how you worked around that on the mill!
 

[tvoght]

Ditto on the cleverness (cleverity?) of your setups on the mill. I am envious of the finishes you achieve. Good work.
--Tim

[EricB]

Thanks for the comments. I like to try and figure out how to do the work with the tools I have. Sometimes it gets strange. I need to make a couple of clock parts from large brass rounds and I've been thinking about them for some time. I decided to try out my ideas on this flywheel. A few things came up in the process.

The extreme parting photo shows the final position of the parting blade. I started in close and played out the length as needed to finish the cut. I figured I would end up using a hand saw but the machine handled it. I caught the spinning cutoff on a chunk of cardboard. I would not try this with other metals than free machining brass.

The facing cuts on the mill in the second picture are at the limit of the machine's rigidity. I was using a broad tipped tool and making fairly aggressive cuts. When it started chattering it almost vibrated off the table. When I try this again I'll reduce the mass on the mill table or shift it toward the center, and make lighter cuts with a smaller tool.

Chris, I have the riser set for the lathe. I used the mill because I've found that when you rotate the headstock the table Y travel stays perpendicular to the spindle axis (assuming you took the time to align the mill column in the first place). When you add the riser to the lathe that isn't true and you must indicate it in. I have my lathe aligned now and I'm not wanting to mess with it if I don't absolutely need to.

Eric

[crueby]

Odd on the alignment, the key in the headstock should keep it parallel, unless the slot is out of line.

[EricB]

Chris,

As Sherline likes to say their tools are precision milled, not precision ground. They have a tolerance limit for headstock alignment and when the spacer is installed those tolerances build up.

Eric

[EricB]

Continued work on the frame today. Carving out the center went well, just took a long time on my small mill. Not much more to say but lots of chips. I still have six more holes to drill and tap. I managed to break a drill on the first hole. Lucky for me it was not deep and I was able to get the end of the bit out by enlarging the hole with an end mill. All my mistakes will be hidden by the cylinder.

Eric

[crueby]

Frame looks great, thats a very different design than the usual one.


 

[MJM460]

Very elegant frame Eric.  A great start to an interesting engine.

MJM460

[EricB]

Thanks for the comments. I have a lot of time and emotion tied up in this frame.

Today I drilled and tapped the final six holes in it. If I never tap another piece of aluminum it will be too soon, but I still have another aluminum part to make with four more tapped holes. I practiced on a scrap piece and still had trouble with the last hole. I also broke my fancy ratchet tap handle on the four bottom holes.

Eric

[crueby]

Thats why I much prefer working with brass, more expensive but a pleasure to work.


Looking forward to seeing it progress.   

[RReid]

Are you using any lube when tapping aluminum? Brass can be tapped dry, but ali can grab without a little slick-um, especially if you don't break the chip often enough. Even a little candle wax rubbed on the tap helps, but usually I just add a drop of my way oil (10W hydraulic jack oil, with a small dollop of STP added). With that I find that even small taps down to 1-72 go just as easily as into brass.

[EricB]

Yes I'm using a lube. What I have is a light machine oil and WD40. The chips aren't sticking to the tool so much as they jam when I back out to break the chips. I've had no trouble with larger taps, but the smaller ones in aluminum are making me nuts. I've read I should be using neatsfoot oil. Would that make a difference?

Eric

[crueby]

Only thing I've found that works well in aluminum (and it does vary with the alloy, some are worse than others) is to back out the tap every turn or so, sometimes it means working the tap back/forth just in that small advance, since the chips jam so much. Especially with small taps like 2-56, they fill the flutes very quickly. Need to back it up every half turn to break the chips small, then back out completely every full turn or so.

[EricB]

I guess I'll just have to keep practicing til I get comfortable with it.

Today I made some little bits and finished some others. First was link pivot for the valve gear. It mounts to the side of the frame below the the exhaust side bearing. I got to use the big strap clamp I made for the frame again.

Next I finished drilling all the steam passages in the valve plate, and then drilled the exhaust ports through the valve plate into the cylinder exhaust passage. Someone once told me that Sherline's sensitive drilling attachment was worthless and I'd never use it, but I think it was quite handy for this task.

Finally I installed studs to attach the steam connection and made some nuts for them.

Next I think I'll work on the valve and the rest of its linkage. Then I can find out if it actually works or is just a paper weight.

The philips head screws are just for fitting the parts. Once I get around to final assembly I have hex bolts for them.

Eric

[RReid]

You also don't want to use a tap wrench with too much leverage. For small taps I mostly hold this one by the knurled portion twixt thumb and forefinger. Much better "feel" that way, and my grip is not strong enough to break a tap from there (unless I bend it sideways). If I need to move up to the tommy bar for more leverage as the hole gets deeper, I get very careful and a little worried. And still use as little of the available leverage as possible. As Chris said, in aluminum especially back up early and often. Don't worry, you'll soon get the feel!