Much to my surprise, it has been since the end of June since I did an update on my Webster engine and all that.
There has been a lot going on for a handful of parts. My main task has been to make three pieces that become what's called the Valve Block Assembly. There are three slices, each 5/8 wide by 1" long and 1/4" thick aluminum. The top and bottom look like each other except the top has drilled and countersunk holes to pass a #2-56 screw, and the bottom has holes tapped for the ends of those screws. The middle piece has clearance holes in those same places (3/32", .094", from both closest sides).
Today I did a test fit assembly and posed the pieces on the drawing.
The tall things sticking off the top and bottom in the picture are valve guides or cages. The valves and cages are the next parts to make, and they're fiddly little things. The cages are 3/8" OD on that rim at the bottom, and smaller everywhere else; the valves are made from 1/4" diameter steel rod.
Along the way to getting those valve block slices done, a problem that had been developing with my tools got to the point where it had to be fixed. I have a nice drill chuck that I use on the milling machine. The chuck is mounted to the milling machine with an adapter from the chuck's JT33 taper to the mill's R8 tooling mounts. Over the last few months, that chuck started falling off in use. Since someone always asks, that was while drilling holes not using it to hold cutters for milling. Originally, it was an occasional thing but over the last several months it got more frequent. Finally, when I was drilling two holes and countersinking them, it got to the point where it was impossible to cut the countersinks without the chuck dropping off.
My fix was to do one of those things I'd always heard of but never done. After thoroughly cleaning the adapter and the inside of the chuck with mineral spirits, I put the chuck in a toaster oven at 200 F and put the JT33 to R8 adapter in our freezer at 0F. I left them there for an hour and then dropped the adapter into the chuck. Once there, I hammered the adapter with a brass chunk between hammer and adapter (softer metal so that the R8 adapter didn't get reshaped). The idea is that the adapter has shrunk in diameter from the cold while the chuck has gotten bigger, making the adapter fit farther into the taper than if they were both at room temperature. When they both return to room temperature, it should make a very tight fit. Since then, I've done a few dozen operations and the chuck has remained in place.
Also along the way to getting the valve block slices done, I lost a critical drill bit. When I got the mill, I bought one of those "900 drill bits for $1.50" sets - probably this one from Grizzly - fully expecting them to be able to drill one or two holes before they went dull, but thinking it would show me what I needed to buy. Over the years, that set has gotten a lot of gaps in it from bits that have broken and it was getting hard to get the right size. A lot of times, even with a numbered bit, you can get by with the one next to it in the set, but there are times when you can't. I've had some bits not able to drill two holes before they broke, and some have lasted for many holes. In this instance, the bit stuck in the work. Probably melted some aluminum chips and then they refroze. I was able to get the bit free but it wasn't likely to make another hole. Bottom line was I needed to buy a good set of the numbered bits - #1 to #60.
Bottom line is that there has been a lot going on but not much in results. I think I start cutting the valves tomorrow.
I don't know how critical your valve seal at the face needs to be but in internal combustion engines they have historically machined about a 1 degree difference between the valve face and the valve seat to get a good seal.ReplyDelete
Scroll down a bit ion this page for an illustration.
Fiddly bits indeed.
Don't even get me started on drill bits.
I literally just got another set in the mail yesterday that I ordered off of Ebay. Hogg Driil bit set, 1/64 to 1/4 in a Huot case for about $20.
I go through those little bits like candy.
Hopefully these will last a while, high Moly content.
I like this little motor project you have going here, looks to be pretty interesting.
The little Internal Combustion Engine is a public domain design, by a guy named Joe Webster. It also has .DXF format drawings so that I measure lots of stuff on them and make some 3D solids. The Webster is recommended as a first project in IC engines. The plans are on the Home Model Engine Machinist forum and probably other places, too. With your experience, you could probably skip it and make something more involved.Delete
I'm making the valves and cages to plans that another guy put up on the forum. He says cut the valve at 92 degrees and the cage at 90, then you grind them onto each other.
I'm not sure how many sets of drill bits I have around the shop. Probably six. Like Ominous Cowherd says, I also have lots of replacement bits that I've bought in lots of five at a time.
This case of Grizzly bits, which is #1-60, lettered bits and fractional from 1/16 to 1/2 by 64ths, just didn't seem worth adding to. I'll add to the new set I got, which is American made, all HSS.
Buy good quality bits to fill the holes you have made in your cheap set. You don't need to buy a whole 'nother set. After all, you're only breaking the ones you use.ReplyDelete