Best way to set this assembly up to bore out a threaded hole?

I have a basic Bridgeport universal mill and a small (8 inch swing) Harrison lathe. I need to alter some home fabricated lower suspension arms
from a race car. I cut off the stock compliant rubber bushed "eye" from the arms, and welded in a drilled and tapped buttress to take a rod end. I now find the geometry of the car has proven to need yet more negative camber. The rod ends are now threaded right out, so the ends of the threaded shanks are just flush with the inside walls of the buttresses. I need them about a quarter of an inch further exttended, and ideally for the rod ends to have less shank out of the buttress for added safety and strength. I have decided to bore ou the threaded holes to take a steel tube, internally threaded 5/8 UNF for the existing rod ends. I am unsure of the best way to hold the arms to allow me to drill concentrically with the existing threaded hole to take a sleeve which I envisage as having about a 5mm wall thickness. This will effectively extend the buttress further outboard, and the existing rod end will screw into it and use the same type of locknut against the end of the sleeve. Any clever ideas how to set this up, given I have very limited fixtures and tooling, and not a lot of experience with my machine tools? Thanks.
Photos are at http://www.gatesgarth.com/bore/bore.html
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Why not just weld that nut on to extend the threads? Put a bolt and nut so the nut is just touching the arm and tack it in place. Then turn the bolt so that you know there is no binding - then finish the weld all around the outside.
-jim
Chris Wilson wrote:

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On Sat, 28 May 2011 13:57:39 -0500, jim wrote:

I did consider this Jim, but once the rod end it totally out of the bulkhead region it's solely held by the weld around the nut. It's a big heavy old car (Nissan Skyline) and rather than just rely on a peripheral weld I would be happier if the rod end was in a tube that was supported in the middle, and welded all round at both ends, if you see what I mean. The weld a nut on idea is tempting, time and effort wise, though :) Thanks for the idea and the post Jim.
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wrote:

I take it the problem is that arms are too long to set up on the BP table with the hole axis vertical? If so, clamp the arm to the *front* of the table with the tail end hanging down towards the floor. If they're stiil too long, tilt the part and the head.
Or make a friend who owns a right angle head.
Or clamp the arm to your lathe's crosslide and put the tool in the spindle.
--
Ned Simmons

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I read this as asking how to locate the center of the threaded hole.
I would cut the head off a bolt that fits it, screw it into the threads and chuck the bolt in the drill chuck, then figure out how to support and clamp the part in that position. You don't want to tighten the clamps while the bolt is in the chuck, in case the work springs sideways, but you could loosen the chuck and retract it, then check alignment after clamping by seeing if it will still slide onto the bolt shank.
Commercial bolt threads may not be exactly concentric with and parallel to the shank. If that matters you could indicate the shank while threading in the bolt.
jsw
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