effect of welding on tolerance?

Hi,
I want to draw a steel ring along on two leadscrews, traveling
linearly in the direction of a diameter (not in the direction of the
axis). The ring is 6.625" OD and 6.065" ID. Given limits of space in
the part, I've decided to use two 3/8"-12 acme coupling nuts, which
seem only to come as hex nuts. I will mount the ring on the mill, and
bore two "shelves" for the nuts to rest in, so that they will be
parallel on opposing sides of the diameter of the ring.
So, I will have a steel ring with two little semicircular-bottomed
pockets drilled into opposite sides, oriented just like the tapped hole
drilled in a shaft collar. I need to secure the coupling nuts into
these pockets, and pretty close to parallel or the leadscrews, turned
in sync, will bind.
WILL humble epoxy hold well enough? The forces on this should not be
so very great.
If not, can I weld it? If I lay the hex coupling nut into the
circular pocket and use a mig welder, will it stay pretty neat, or will
the heat harm the acme threads inside the nut or significantly affect
the tolerance of the ring itself? Granted-- the ring CAN become
eccentric, just no more so than ~1/32" at very worst.
Will mig welding likely affect the threads much or the concentricity
of the ring beyond the above tolerance? If so, can brazing be used to
fill gaps (because of the hex nut and circular pocket issue) and would
it, with its much lower temperatures, affect the threads and ring much
less? Or would even epoxy hold, given over 1.5 X 3/8" gripping surface
area?
thanks!
-Bernard Arnest
Reply to
Bernard Arnest
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Welding will move the nuts randomly and frustratingly. You are only thinking about radial displacement - what if you weld a little hotter on one side than the other so the nut is also skewed in an angular sense. I wouldn't weld them.
I can't follow your description, but when I don't want an assembly to move much I braze it, and if I want it to move hardly at all then I silver solder it.
GWE
Reply to
Grant Erwin
"Bernard Arnest" wrote in news:1154494369.039963.231440@ 75g2000cwc.googlegroups.com:
Welding will kill it.
I would suggest 2 E-Clips, one on each side of the nut, and a couple of set screws to keep it from rotating. A wavy spring from smalley between the E- Clip and the nut will allow the nuts to move enough to keep from binding, while if properly installed, will help take up any backlash at the same time.
Reply to
Anthony
Not at all.
Yes. :-)
If it is clamped there while welding, it will.
A bit near the seam. Nothing tragic.
For shure! It will warp. You will have to bend it staight again.
Nick
Reply to
Nick Müller
If the nuts are set in a machined pocket then you only need the weld to stop rotation??? If so, weld only enough to stop rotation which means two quarter inch long tack welds on opposite flats of the nut. If you completely weld around the circumference of the nut then it likely will shrink onto the leadscrew. Brazing would be worse simply because of the excessive amount of red heat causing even more shrinkage. Short MIG welds are very effective at locating components especially if the loads are taken by a separate shoulder or stop. Randy
Hi,
I want to draw a steel ring along on two leadscrews, traveling linearly in the direction of a diameter (not in the direction of the axis). The ring is 6.625" OD and 6.065" ID. Given limits of space in the part, I've decided to use two 3/8"-12 acme coupling nuts, which seem only to come as hex nuts. I will mount the ring on the mill, and bore two "shelves" for the nuts to rest in, so that they will be parallel on opposing sides of the diameter of the ring.
So, I will have a steel ring with two little semicircular-bottomed pockets drilled into opposite sides, oriented just like the tapped hole drilled in a shaft collar. I need to secure the coupling nuts into these pockets, and pretty close to parallel or the leadscrews, turned in sync, will bind.
WILL humble epoxy hold well enough? The forces on this should not be so very great.
If not, can I weld it? If I lay the hex coupling nut into the circular pocket and use a mig welder, will it stay pretty neat, or will the heat harm the acme threads inside the nut or significantly affect the tolerance of the ring itself? Granted-- the ring CAN become eccentric, just no more so than ~1/32" at very worst.
Will mig welding likely affect the threads much or the concentricity of the ring beyond the above tolerance? If so, can brazing be used to fill gaps (because of the hex nut and circular pocket issue) and would it, with its much lower temperatures, affect the threads and ring much less? Or would even epoxy hold, given over 1.5 X 3/8" gripping surface area?
thanks! -Bernard Arnest
Reply to
R. Zimmerman
How about tacking them with the mig and for peace of mind, "JB Weld" filler.
Reply to
Tom Gardner
Hi,
The tube is 9/32 in wall-thickness. Could this be bent out again, and if so, how?
Will silver solder fill gaps, since this unfortunately is NOT a perfect mate, with the hex to the pocket in the ring? If necessary, there IS another nut in the catalogue that IS round, for a perfect mate and no gap-filling needed, although it's shorter, twice as expensive, and wider in OD (when I'd prefer to keep it ot .5")
The pocket covers less than half the circumference of the coupling nut, the coupling nut is more resting on it than at all fully enclosed in a cavity. The welding doesn't just hold it in place, it must hold all of the (mild) forces, too.
thanks for the advice! -Bernard Arnest
Reply to
Bernard Arnest
Given your design constraints and my past experience, I'd turn the OD of the hex nuts round, leaving a small hex shoulder, bore the holes a couple thou over the size of the new round diameter of the nuts, counterbore the top surface of the hole so that the shoulder of the nut mates nicely with the ring, then secure the nuts in place with bearing retainer compound
I believe it will be stronger than epoxy without the warping issue of welding and will allow you to dial in or out whatever 'preload' you might want. Be sure to pick a bearing retainer that gives you enough setup time to position them where you want them.
Reply to
Jim Stewart
I think your best bet would be to design some kind of pivot which allows the nuts to align themselves with the leadscrews.
Best wishes,
Chris
Reply to
Christopher Tidy

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