Engines > From Kits/Castings

First build from castings

(1/3) > >>

Allen Smithee:
To date I've kinda stayed away from castings - I guess it's the lack of flat datum surfaces that put me off. But a few years ago I came by one of the Bruce Engineering external hone kits and over the last couple of days I decided that I had to overcome this aversion. So here it is:




Of course the castings are only aluminium, which makes it easier. But they were slightly warped (twisted) which meant having to be careful to choose the positions for the through-holes so that the didn't get too close to edges on the other side. Needless to say I found it far less fraught than I had feared - having chosen a datum face and machined it flat the rest was just a matter of looking at the drawings, thinking about how to hold the job.

In fact of all the daft things - the only bits I had trouble with were the two 1/4" pins. These each have cross-drillings in the middle - one to be tapped 4BA and the other a 4BA clearance. I'm embarrassed to admit that I had four goes at making these before I got usable parts! I ended up clamping a long piece of 1/4" stainless between two V-blocks and then carefully establishing true centre (using an edge finder) to centre-drill and then drill/tap without moving any axis other than the quill. The pins were then cut out of the bar and faced to the required lengths.

Anyway, that particular dragon is now slain!

AS

crueby:
Nicely done! Do you know what it will be used for first? honing valve rods, pistons?


For drilling centered holes crosswise in round rod, a trick I was taught was to take a piece of flat or square stock thicker than the rod, clamp it in the mill vise (with the vise lined up to one of the axis on the mill) and drill a hole in it the size of the rod. Hole does not have to be centered - just so the hole doesnt break through the side. Keeping the mill table locked down, turn the fixture 90 degrees so the hole is sticking out the side. Then insert the rod in the hole, and drill your final hole through the fixture and rod. Since the table was kept locked, the center of both holes are in line with each other. I used this to drill a hole batch of rods for cotter pin holes, worked great.

Don1966:
Nice work Allen love the hone!



 :cheers:
Don

Allen Smithee:
Well they said that for the duration of the crisis I needed to be at hone... ;D

I tried that drilling-through-stock trick, but the drill wandered when it got to the pin. Really odd, because it wasn't especially hard material or anything.

AS

crueby:
Try it with the block and rod the same material. Or maybe with the block harder than the rod? Hmmm...

Navigation

[0] Message Index

[#] Next page