Wobbly legs: What's the fix?
Moderator: Shoshanah Marohn
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Ross Shafer
- Posts: 1267
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- Location: Petaluma, California
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Jeremy Threlfall
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- Joined: 3 Aug 2006 12:01 am
- Location: now in Western Australia
my Williams developed a loose leg. i reckon it was a flattening of part of the thread on the leg. i put a fibre washer on it - probably 1/32" thick. that was enough to move the contact points of the thread around a bit, so that it grabs adequately. its been like that for a couple of years now, reminds me, i should get it fixed properly. i expect a machine shop could redo that thread for me
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Dave Welch
- Posts: 83
- Joined: 25 Mar 2010 10:39 pm
- Location: Latrobe PA USA
This is just my viewpoint as a retired machinist. You may disagree with my excessive ramblings, and you are certainly entitled to do so! It's just my two cents...
I don't believe the problem is always so much with worn threads as it is perhaps with the condition of the aluminum spotface which is the mating contact surface for the chrome plated shoulder of the leg. It takes a lot to wear threads down to the point where they would cause wobble. Threads mostly provide the axial force required to draw the leg shoulder and spotface together, more so than providing stability.
More than likely you're tightening a loose fitting thread with exactly the same amount of torque as a snug fitting thread, especially since you're only hand tightening that leg.
If you think about it, the 60 degree angle of the thread "V" form naturally causes the leg to draw tightly toward centerline of the tapped hole as your hand torques it until it can't rotate any further. At that point the leg shoulder seats itself. A good flat leg shoulder against a good flat spotface or counterbore face will result in a solid feel as it seats. A slightly damaged or uneven spotface will most likely cause leg wobble.
I had a new steel that I could screw the legs in within 1/8" from seating, and there was a considerable amount of play in the threads. Yet once hand tightened the feel was very solid. The mating surfaces were flat, smooth and parallel, resulting in a good solid fit, and no wobble.
In another example, I had an 80's D10 that had a wobbly rear leg. Drove me nuts. I finally examined the leg and found the shoulder had a small ding near the edge which had scored up the aluminum face a little bit. Enough to cause a problem. I took a small triangular aluminum oxide sharpening file (available through MSC or other tool supply companies) and with the flat edge at one end I carefully scraped both the leg shoulder surface and the aluminum spotface until they were both flat again with no raised areas. I followed up by lapping the spotface using a flat washer and some lapping compound. I know, patience! After cleaning out the hole and all contact surfaces, the leg then screwed in and seated firmly, and the leg movement was gone.
And so, that's been my experience with fixing pedal steel leg wobble, and thus far it's worked for me with the few times I've had to deal with it. If those faces aren't good and flat, rigidity will most likely be compromised.
That's not to say that excessively worn threads might not contribute to the problem, they may be part of the problem as well. But I think they'd have to be worn a LOT to cause an issue. If a spotface is badly worn out and uneven, then I guess I'd try smoothing out the rough spots as best I could, and then use maybe a nylon or hard fiber oil drain plug washer as some have suggested, which might compress and conform somewhat, resulting in a more rigid fit.
And of course there could be other factors. As others pointed out, it could be the threaded stud is loose inside the leg. That's another problem altogether with different possible fixes.
By the way, that Sierra tapered fit design does look ingenious, but right now that's an option I couldn't afford! But I can dream...
Sorry for the lengthy feature presentation...
Again, just my two cents, which may be all that it's worth!
I don't believe the problem is always so much with worn threads as it is perhaps with the condition of the aluminum spotface which is the mating contact surface for the chrome plated shoulder of the leg. It takes a lot to wear threads down to the point where they would cause wobble. Threads mostly provide the axial force required to draw the leg shoulder and spotface together, more so than providing stability.
More than likely you're tightening a loose fitting thread with exactly the same amount of torque as a snug fitting thread, especially since you're only hand tightening that leg.
If you think about it, the 60 degree angle of the thread "V" form naturally causes the leg to draw tightly toward centerline of the tapped hole as your hand torques it until it can't rotate any further. At that point the leg shoulder seats itself. A good flat leg shoulder against a good flat spotface or counterbore face will result in a solid feel as it seats. A slightly damaged or uneven spotface will most likely cause leg wobble.
I had a new steel that I could screw the legs in within 1/8" from seating, and there was a considerable amount of play in the threads. Yet once hand tightened the feel was very solid. The mating surfaces were flat, smooth and parallel, resulting in a good solid fit, and no wobble.
In another example, I had an 80's D10 that had a wobbly rear leg. Drove me nuts. I finally examined the leg and found the shoulder had a small ding near the edge which had scored up the aluminum face a little bit. Enough to cause a problem. I took a small triangular aluminum oxide sharpening file (available through MSC or other tool supply companies) and with the flat edge at one end I carefully scraped both the leg shoulder surface and the aluminum spotface until they were both flat again with no raised areas. I followed up by lapping the spotface using a flat washer and some lapping compound. I know, patience! After cleaning out the hole and all contact surfaces, the leg then screwed in and seated firmly, and the leg movement was gone.
And so, that's been my experience with fixing pedal steel leg wobble, and thus far it's worked for me with the few times I've had to deal with it. If those faces aren't good and flat, rigidity will most likely be compromised.
That's not to say that excessively worn threads might not contribute to the problem, they may be part of the problem as well. But I think they'd have to be worn a LOT to cause an issue. If a spotface is badly worn out and uneven, then I guess I'd try smoothing out the rough spots as best I could, and then use maybe a nylon or hard fiber oil drain plug washer as some have suggested, which might compress and conform somewhat, resulting in a more rigid fit.
And of course there could be other factors. As others pointed out, it could be the threaded stud is loose inside the leg. That's another problem altogether with different possible fixes.
By the way, that Sierra tapered fit design does look ingenious, but right now that's an option I couldn't afford! But I can dream...
Sorry for the lengthy feature presentation...
Again, just my two cents, which may be all that it's worth!
Psalm 33:2 Maybe they did have steels back then...
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Donny Hinson
- Posts: 21192
- Joined: 16 Feb 1999 1:01 am
- Location: Glen Burnie, Md. U.S.A.
Well...IMHO, Fender already had the best idea over half a century ago; the threads were down in a counterbored hole. You just dropped the leg into the hole and tightened it up. That straight counterbore made sure that you couldn't try to screw the leg in at the wrong angle (which you could do with the tapered counterbore design pictured above).Ross Shafer wrote:The new paradigm for pedal steel leg mounting.
I was always amazed that no other manufacturer ever picked up on the idea.
Silly them.
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Bobby D. Jones
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Dave Welch
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Dave Magram
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