This week I decided to work on the valve heads for the engine. The heads are to be machined from a 1-1/8” diameter Cold Rolled Steel (CRS) rod. The CRS alloy provided in this kit is very easy to machine compared to the average carbon steels found at your local hardware store. This is a good thing considering the amount of cutting required to make these parts :0)
I started out with the lower valve head by coating the CRS rod stock with Dykem layout fluid. Using my calipers I laid out the cut lines for the head on the rod and started cutting down the neck of the head.
I cut down the neck to about .37” in diameter in preparation for the 3/8-24 tap. You will notice that I used the 1/4 round tool bit for a nice transition from the neck to the head (below).
I carefully threaded the head’s neck using a 3/8-24 die. I used the lathe’s chuck to hand tap the part which also helped check for wobble on the die. Note: You have to be super careful not to allow the die to go on crooked or the piece will be ruined.
Once the threads were cut I was able to trim the length of the neck to about .6” to the top of the head (the prints call for .5” long but I added a little length for the 1/4 round base).
The next step was to bore out the neck for the valve rod. I used a 3/16” drill bit for the bore.
The next step was to cut the shoulder on the back of the head. This shoulder will center the head in the bore of the valve chest. I used a HSS parting tool to make the narrow cuts as well as part the head from the 1-1/8” CRS rod stock.
The finished head came out nicely :0)
Using the brass 3/16” rod provided with the kit I was able to fit check the bore of the head for clearance. The bore was a bit too tight for the rod so I honed out the hole with a rigid honing arbor and 320 grit sandpaper as seen below. The honing arbor was made from a 1/8” diameter framing nail in which a slot was cut to hold the sandpaper.
After a little fine tuning the 3/16” brass rod fit beautifully into the bore.
The next step was to machine the upper valve head. Once again I laid out the cut lines before boring out the steam outlet port. I used a 21/64” drill bit to bore out the port.
I used a 1/8 x 27 NPT tap to thread the port. Note that I chose to tap the part before machining the neck of the head. This is to prevent warping that may be caused by the tap if the metal being tapped is too thin.
And now I cut the neck of the steam outlet port as seen below. Once again I used the 1/4 round tool bit for a finished look.
I used the parting tool to cut the shoulder on the back of the head as seen below.
I carefully mounted the head back onto the lathe to countersink the inside of the threads. This will help the steam leave the valve chest with less resistance.
The next step was to drill the mounting holes on the valve heads. I used the same rotary table method I used on the cylinder heads before. The head was mounted to the rotary table and centered with the dial indicator.
I drilled out the four screw holes in the head at 90° angles. A #38 drill (.1015”) was used to pilot the holes which will be drilled out later to accommodate the 5-40 head screws.
The upper head was drilled in the same way.....
And now I was ready for drilling the cylinder/valve chest to match the heads. I used the same drill jig method for the cylinder heads to perfectly align the valve head holes to the cylinder “block”.
I carefully aligned the head square to the cylinder block and then drilled “dimple” holes in the block with the #38 drill as seen below. You will notice that I used the existing 10-24 cylinder head threads to hold the clamp in place.
I used the dimple holes as a guide to finish the #38 holes in the cylinder block as seen below.
A 5-40 tap was then used to thread the holes.
Now that the head’s job as a drill jig was over I could drill out the holes with a 9/64” drill bit.
And now the finished product :0) I used some polishing compound to clean up the appearance of the heads a little...
After looking at the parts I had made so far I had decided to polish the crosshead frame and outer cylinder head to “match” the valve heads. I used the lathe’s faceplate to turn the frame and outer cylinder head so they could be polished (below). You may notice that I bolted the head to the frame so they could be both polished at the same time.
And now the fit check. Everything bolted together correctly and I am pleased with the outcome :0)
Now that I have the heads finished I can start working on the crosshead and connecting rod assemblies. Join me again for the next episode of the 6CI steam engine project. Till then be safe my friends!!!!
