Had some more fun today...
First turned the 3mm pivot shaft from the only piece of 6mm brass rod I have & threaded the end M3. Took a photo of that but it's so out of focus I can't show it here :hDe:
Elmer suggests an aluminium "plug" in the cylinder bore when you solder the pivot pin to the block to prevent solder from flowing into the cylinder. He also suggests putting some packing over the cylinder bore opening when machining the recesses on the block face. I combined these requirements (and a "no burrs left in the cylinder option
) by taking the piece of aluminium off-cut that was left when I made the column - it had about a 6mm length on it that was machined the same size as the column's head; the rest was thicker, but
just long enough to use . I just chucked it on the thinner machined section, and turned down the rest to fit fairly tightly into the bore. In fact, when I tested it, the fit was so close, that I couldn't push the cylinder much more than 5 mm over it; it would just pop right off again from air pressure in the cylinder.
Not wanting to struggle to get it out later because of an air-lock, I drilled a 5mm hole through the plug; if needed I can then use it as a mandrel and/or lap later in the build
Then I set up the cylinder block (with the aluminium plug pressed in) in the 4-jaw and centered on the pivot hole. Elmer mentions that you must use a dial test indicator to check the squareness. I don't have a DTI yet, so used my favorite dial indicator. I know my lathe faces slightly concave, so rather than tramming like Elmer suggests, I just took alternative readings on the ends by rotating the chuck and used the chuck spanner's handle as a lever between the brass plug and chuck face to get things squared. Then a test on a "circle" closer to the pivot hole with the dial indicator showed no discernible run-out; meaning the cylinder face was square on all sides.
By now, you should be tired of reading, so here's a picture of how I did the set-up to turn the recesses and pivot hole:
Easy going; turned the recesses to 0.4mm deep and drilled the pivot shaft's hole. With the aluminium plug inside, I drilled the 3mm pivot hole
just till the first aluminium swarf came out, so the hole is not entirely through the brass - leaving some retaining shoulders and no burrs in the cylinder. Then to make life easier while soldering, I put a generous fillet in the hole using a countersink.
I turned the aluminium plug in the cylinder to get away from the "dent" left by the drill. Got everything right for soldering - all cleaned up etc.
Then the FUN started :fan: - the pivot shaft was WAY to loose in it's hole :wall: - I measured, thought, reflected, and then looked at my drill set;
I drilled the darn pivot hole 3.5mm and not 3mm !!! :rant:.
After a cup of coffee I decided next best was to make a new pivot shaft; just turn it 3.5mm for the section that goes into the cylinder block and 3mm for the rest. Problem was, I didn't have brass stock left for it. OK, some 6mm silver steel turned down should do the job. Turned a new shaft; used emery to get the 3mm section bang on size for the column, and then proceeded to turn the 3.5mm section under-size again! :rant: :rant:
Well, third-time lucky ??? Made a soap advertisement pivot shaft (of the New! Improved! variety) - it worked! - was still slightly loose in the hole - ideal for soldering. Not wanting to struggle with it moving when soldering, I used the rough beaks on my big vice to put some raises & dents on the 3.5mm section - worked a charm; I needed to lightly tap the shaft into place, it didn't wiggle a bit in the hole and was nice and square in all directions, leaving nice room for the solder to wick in
(If this seems like a cheat - yes it is, but it beats the heck out of trying to get punch marks on the shaft to get it to stay put ;D)
So ended off this evening with this:
2 shafts now useless for this build - for the photo wall-of-shame; they will be re-used
, the aluminium "multi-purpose" bit with the dent left by drilling, and the cylinder block with shaft eventually attached.
At least little Fancy's column and cylinder block could come together - some bling still needed though
:
Regards, Arnold
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