How to assemble a shaft precisely square to a plate

I have never tried to do anything like you are doing. But I would bore the holes in the plate for a press fit. Then thread one end of the rod and also chuck the rod in a lathe and turn it undersize by a thou or so for a short distance next to the threads. Then insert the rod in the hole and pull the full diameter part of the rod into the hole using a nut. In order to get in all the way in you will need to have a short cylinder so you can get the bit of undersized rod completely thru the hole. Then you get to saw off as much as you can and file or mill the rest so it is flush with the plate ( assuming that you can't have any rod sticking out the bottom of the plate ). I would wipe the rod with an oily rag before pulling it into the plate. And it still might not work as the aluminum may gall and throw the alignment off.

Dan

Ok, can you make the bore plate thicker? 4 diameters would do the trick. Another thought would be to call an engineer at a die shoe manufacturer...ask how they do it.

Here is what I would try.

First make a test plate out of the same thickness aluminum. bore then ream the hole .0005 undersize on a mill where you have indicated the head.

After reaming, lower the table and replace the ream with a 3/4 pin in a collet. Using a propane torch heat the aluminum plate a bit and then press in the pin using the mill.

Now check and see if this method does not get you what you want.

Let's assume that you are off .002 from square. A little tap with a mallet should bring you in line and in a 1" thick plate it should stay where you tap it.

My guess is that the pin will be square without having to tap it in place.

what on earth are you on about? turning a shoulder should allow you to position them exactly vertical.

Stealth Pilot

"ADkeit" wrote in news: snipped-for-privacy@p10g2000cwp.googlegroups.com:

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.

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

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

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

On Feb 14, 4:04 pm, "ADkeit" wrote: > 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.

anthony is actually correct. this says more about your workmanship than anything relating to the suggested method unfortunately.

Stealth Pilot

Considering that, per the OP's original post, the tolerance on the pin straightness eats up most of the perpendicularity tolerance, fixing the pin with a shoulder seems like a poor choice. First off, since the pin is not straight, what point on the pin do you choose to specify the runout of the shoulder? Second, even if the pin were perfectly straight, the runout of a reasonably sized shoulder would have to be held to a much tighter tolerance than the .001 over 6" perpendicularity spec. Unless you're prepared to grind the shoulder and pin OD in one setup, I think the Loctite method is the way to go.

Ned Simmons

Ned Simmons wrote in news: snipped-for-privacy@news.suscom-maine.net:

Ned, If the pin isn't straight, neither method will work. Like you state, at what point is the tolerance effective? If you glue a bent pin in a hole the tolerance is still likely exceeded somewhere along the length, except for the point of measurement during gluing. If the pin is straight, it should be no issue to turn a shoulder square to the axis that will not exceed the perp tolerance. This does have to be measured, not assumed, that the lathe x axis is perp to the spindle axis. But that is a manufacturing set-up issue, not a method of manufacture issue.

"ADkeit" wrote in news: snipped-for-privacy@k78g2000cwa.googlegroups.com:

Aaron, The um wasn't meant in a smart-assed way, it was written in a 'thinking' mode. Unfortunately the written word does not convey very well expression, emotion, voice inflection or other clues to meaning that oral words do. My bad for not making it clearer as to my meaning.

As for the pin, if the pin is straight, and the shoulder is turned actually perp to the pin axis, the pin will fall within tolerance. With your tolerance, any burr, dirt, filings or practically anything else between the shoulder and the plate will cause it to be out of tolerance. This includes the raised portion of the plate around the hole created by the drilling operation. Did you stone the hole face on the plate prior to installing the rod? It also matters what the surface area of the shoulder is, relative to the hole. The shoulder method is used extensively in all manner of industrial equipment for this purpose. I use this method in my designs also, especially in part fixturing designs and have had no issue if the parts were manufactured to specifications.

I've met Ned and he is, as most here have figured out from his posts, a very knowledgeable and very nice guy. In his nice way he's already said - twice - that when the tolerance in the parts you're starting with takes up most of the allowable final tolerance, you may just be doomed from the start. And we never even talked about flatness tolerance for the plate.... Pretty tough to make silk purses when all you have is pigs' ears.

There are a couple of other things I might try, though.

One would be to use an oversize pin. Press it in, with or without shoulder, with or without Loctite, then mount the plate on a lathe and grind the pin to final size with a toolpost grinder. Or turn it to size with a boring head on the mill, then lap to final finish if necessary.

Another would be to insert a to-size shaft, with or without Loctite, and then use a prick punch to upset the plate next to the pin to move it in whatever direction is indicated. Top side or underside, or both. You couldn't move it a whole lot, but I'd think a couple of thousandths would be possible. Stone off the crater rims afterward, fill them with epoxy if you want.

I'm still intrigued by the idea of heating the plate and shrinking it onto the pin.

So, Ned, that snow was pretty much a bust, wasn't it? Still waiting for the big one here in coastal Maine,

John Martin

The original proposal was to fixture the pin as the glue set. With the proper fixture you could at least check, either against the fixture or with a precision square and feeler gage, whether the perpendicularity is in spec while the pin is fixtured. If not, try another (hopefully straighter) pin.

The way I look at it, the best way to get around the potential stack up of errors facing the OP is to do bit of compensation (either Loctite in a loose hole or peening the plate next to the pin), rather than adding more potential sources of error (pressing into a bored hole or adding a shoulder). I agree that in a perfect world an approach that doesn't require fussing with alignment at assembly is preferable, but I don't see that happening based on the original presentation of the problem.

Ned Simmons

Thanks for the kind words, John.

I think you got more snow than we did - only about six inches of heavy snow here. When was it that a snowstorm and temps in the teens in February became big news for days in advance of the storm?

Ned

"John Martin" wrote in news: snipped-for-privacy@p10g2000cwp.googlegroups.com:

John, I'll agree, Ned is a sharp guy. He also has some good, valid points. The stack-up is tough in this application. I'm just of a difference of opinion on how I would do it vs. Ned. I think part of the issue is that the OP was using stock materials on hand, vs actually designing the system from scratch, I was thinking more along the lines of design from scratch, thinking (right or wrong) that the OP could still make design considerations in the system.

Anthony,

Sorry for my snide comments. You didn't deserve that and I wasn't really mad at you. I sat down pissed about something else and got annoyed with what I thought you meant. My apologies.

My first thought was to do it the way you suggested, but I couldn't trust the precision of my parts and equipment to actually produce the results as accurate as needed. The problem is that slight imperfections along the lines of a Tenth in the shoulder or the face of the plate would translate into much larger errors 6" out.

I put a precision V-block on the plate and gently clamped it in the proper position. I put some primer on the shaft, and the loctie in the bore, then slid the pin into place, clamped it, and let it cure. I indicated the position of the tip of the pin and checked it again after the cure(and removl of V-block) to see if it moved. I didn't check with a square gage (because I don't have one yet) but I was really just checking to see if it moved while curing.

IFor the other shaft I screwed it in from underneath against a shoulder turned in the pin. While I don't know exactly how out of square it is I could see light gaps when I plut a precision square against it.

Thanks for all the great suggestions guys... I think I'll be able to do it, and I apologize to all for being testy before.

Aaron

just an opinion here, but you can't do that in an aluminum plate, it's too prone to all kinds of sloppy press-fit problems, the kind of problems that aren't particularly correctible. Also, if one of the rods had any lateral force, it would tend to deform the hole it was pressed into, loctite or not. Meaning, it would overall be a pretty fragile assembly, particularly over time. You would be much better off doweling a tool steel blank. In any case, those press tolerances are fairly demanding, and you may need to hone them to get what you want, which is a critically sized press fit dimension to facilitate