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Tim Wescott[_3_] Tim Wescott[_3_] is offline
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Default Remember that o-ring groove in that piston?

Bob La Londe wrote:
"Tim Wescott" wrote in message
...
Bob La Londe wrote:
Well, I tried to assemble the hole thing and the push rod threaded
into my piston crooked... How is that possible I wondered. I did
everything on the lathe. Oh, ****. No I didn't. My mini lathe was
too small so I only center drilled the piston on the lathe. I
drilled it on the drill press. I really need to throw this damn
thing away. The table was tilted side to side. I straightened that
today, but found the table is also slightly tilted front to back.
GACK!!! Its not horrible for punching holes in sheet, but I guess I
need to add a mill drill to my wish list for anything else.


Next time, rough drill it undersized in the press, then bore the hole
to size, with a boring bar in the lathe.

I'm not sure about "too small", though -- unless the tailstock chuck
won't take the drill, you should be able to keep loads light by
feeding slowly.


Actually it has an amazing amount of power for a cheap tiny lathe. HF
calls it a 7 X 10, but I think its really a 7 x 8. Several people
on-line have commented that when they swap out to the 14" bed from The
Little Machine Shop they gain about 6 inches of working length rather
than the 4 you would expect. As soon as they are back in stock I plan
to order the longer bed for it, and turn the old bed into a tail stock
parking rest. I still want a bigger lathe but this little one is handy
sometimes.

Now to save that piston... I am thinking I might bore it out further,
hammer in a plug, and re drill it concentrically. Then either drive in
a couple wedge pins or just slap a couple weld tacks on it.


(a) Press in a plug -- even doing this in a vise is going to be more
accurate than hammering it in.

(b) How much force on the piston, and which way? If the piston isn't
going to be pulling hard on the rod, a press fit or shrink fit may be
plenty strong enough. Or a light press fit with one of the more
insanely strong Loctites, or epoxy. Or just fill the hole with epoxy &
call it a plug (hmm).

(c) Press, weld (not if it's epoxy, though), _then_ bore out the hole --
and check the outside for concentricity and warps, too.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com