How to assemble a shaft precisely square to a plate

Hi,
I have an aluminum plate which has been ground flat, and I would like to insert a few precision ground shafts into this plate and have them
rigidly/permanently affixed in place, precisely square and perpendicular to the plate. The shafts diameters are .75" and the plate is 1" thick. The shafts will protrude 6" out and I would like it to deviate from squareness by less than .001" over the 6". The straightness of the shafts are rated at .001" per foot.
My initial idea is to bore out the holes a couple thou oversized and then loctite the shafts into place, holding them in place by clamping them to a precision ground v-block w/ .0001" squareness tolerances. Or I could beuild a fixture to adjust the tilt and and measure the squareness with a squareness gage, but I'd have to buy one.
Does this sound like a good idea to anyone? I have a Fadal 4020 VMC and I suppose I could square the plate to the quill and bore for a press fit, but I'm not sure if I could ensure that the shaft would go in straight. If it didnt then I'd be upset, and we wouldn't want that.
Thanks for any advice.
Aaron Keit
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If you're concerned that the hole won't interpolate round, you could always use a boring head, or improvise a boring bar. But it seems to me you are more concerned about the axis of the hole being square to the plate, which I would think is determined by the setup of the plate in relationship to the spindle centerline. You should be able to prove this by sweeping the plate with an indicator attached to a toolholder mounted in the spindle.

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What the OP means is, even though the hole may be square to the plate, the shaft may not press in exactly perpendicular. It will, sort-of, but not to his spec. for square. Pressing exactly straight would be a very difficult operation.You would need both planes of the plate parallel ground, the bed of the press ground flat and square to the ram, the ram travel exactly square to the bed, etc ad infinitum. He might work around this somewhat by pressing on the mill table, holding the shaft in a collet to at least start the press straight. This will still req both planes of the plate be parallel. JR Dweller in the cellar Jon wrote:

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JR North wrote:

HMmmm, that gives me an idea. Bore the hole to the desired class of press-fit, then, without moving the machine, swap in a 3/4" toolholder and use it to press in the shafts. That should get the shafts straight into the just-bored hole.
Jon
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get yourself some smooth walled steel tube. chuck it in the lathe and turn across the end with a facing cut. make the tube about 6 inches long. put face cuts across both ends. make 2 or 3 of them.
stand the tubes on the plate beside your shaft. align the shaft with the tubes and you should have a perfectly square shaft. hth Stealth Pilot
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ADkeit wrote:

Sporty numbers!

Loctite is too fast for that, if you meant thread locking loctite. 741 (?) starts to react in about 10 seconds. I would think about using a two-component epoxy and glue it in with that. That procedure is often used for aligning the guiding columns of punching tools.
Nick
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I understand the squareness condition. How about placement? Do you have a thousanth's "play" available in the actual locations of the shafts?
If so, I'd recommend pressing the shafts into proper-sized holes, then controlled peening around each hole to "move" the shafts into precise vertical position. Of course, this would disturb the flatness of the plate around each shaft -- the peening can be done from either side, if the shafts are pressed all the way to the opposite surface.
LLoyd
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ADkeit writes:

Can you drill and tap holes in the plate, and turn down and tap matching threads on the end of the shafts? Then you just have to have the shoulder on the shaft square.
You don't mention what the loading is on this shaft, but gluing the shaft into an oversize hole with epoxy or CA should work, but you'd need several squareness gages, which at 0.001 precision you might turn yourself on a good lathe, to jig it in place during the cementing.
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Thanks for the replies so far guys. The shafts will have such a slight load it hardly matters...like one pound. They are used to hold some mirrors that slide up and down the shaft but maintain their angle. I do have wiggle room in the exact placement of the shaft, so having an oversize bore is not a problem. I could turn a shoulder on the shafts and bolt them to the plate from underneath, but I doubt that would be square enough for my specs. Any other suggestions? Will loctite try to "self-center" the shaft and perhaps mess with the alignment while curing?
Thanks,
Aaron
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ADkeit wrote:

It self-centers, but not on the angle. You will be off!
If your plate is flat, you can have a thread on one rod's end with a smaller diameter than the rod itself. It will get very straight, even if the thread is not that straight. It gets even better, if you can have a bigger diameter on the rod's base.
Nick
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Hmmm... I can secure the shaft to the alignment rig very rigidly, and secure the alignment rig to the plate. Won't the Loctite takr the path of least resistance as it cures and just fill the space that is available? Plus, if I take the time to align the plate with the spindle before I bore the bore should be pretty well aligned anyway. No? I don't know...
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ADkeit wrote:

Yes it will. But you will have to apply the Loctite to the shaft before you insert it. And then, as soon as you have put the shaft into the bore, you won't have much time to align it.

But you intended to make it oversize. If you press it in, you will wipe off most of the Loctite.
You'll report how you failed. :-))
Nick
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Why do you assume that the shoulder would not be square enough? Or for that matter, a counterbored pocket in the plate and grind the end of the shafting square? With as little load as there is to be on the shafts, I'd go with setting the shafts in a slighly press fit counterbore that is over half way into the plate, the deeper, the better, then use a fairly small cap screw from the other side to hold it in place.
Mike
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ADkeit wrote:

YOu could press the pin into the block and then put the pin in a collet lathe and face the bottom side.
John
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what on earth are you on about? turning a shoulder should allow you to position them exactly vertical.
Stealth Pilot
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Um, Aaron, Turning a shoulder on the shaft perp to the shaft axis, then bolting it to a ground plate is going to be as square as you are going to get. Make sure you have a slight undercut at the corner of the shoulder, or a big enough chamfer on the plate hole that the radius doesn't interfere at the hole/shoulder corner.
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Anthony

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Um, Thanks, but you were wrong. I tried both methods in a test plate, ground flat. The Loctite-ed shaft stayed exactly where it was placed after it cured. The shaft with the shoulder was out of square by a couple thou over 6 inches. Pretty close, but I can't use pretty close. I'm sure I could tune up the shoulder by hand in a long trial and error process, but I don't have the time. Maybe, um, you could do it for me anthony.
Aaron
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ADkeit wrote:

And you had no problems aligning it? I stay corrected! Did you let flow the Loctite into the gap and did it penetrate well?

Did you screw it in or press it it?
Thanks for sharing your experiences! Nick
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ADkeit wrote:

And you had no problems aligning it? I stand corrected! Did you let flow the Loctite into the gap and did it penetrate well?

Did you screw it in or press it it?
Thanks for sharing your experiences! Nick
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> Um, Aaron,

You know, Anthony is a major contributor and valuable resource here. Who are you? He maybe got a little bit cute with you while trying to help you. He may have been wrong, or you may have done it wrong, but regardless, I think it would have been better to thank him for his input without being pissy.
Now you have a plate with pins *glued* in place for your mechanism. That's supper, good luck with that.
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