leg threads or endplate loose?

Scott Appleton · From: Ashland, Oregon

It seems that the threads on the legs or the endplates of most steel guitars get loose after so many years. What I would like to know is what the best way to
tighten them up is? .. Some say helicoil the endplates and check the threads on the legs to see if their still in tolerance. Are all steel guitar legs and endplates loose to begin with or are they snug.. What kind of variance in tolerance are we looking at here?
Finally what size threads does Emmons use.
Thanks to all who reply.

Larry Moore · From: Hampton, Ga. USA

The Emmons threads are 1/2-13 American Std. Threads per inch.
Larry

Dave Magram · From: San Jose, California, USA

Scott,

I bought some O-rings at the hardware store and popped one on the bottom of the threaded part of each leg of my old Emmons guitar. The O-rings help keep the legs from loosening. Total cost for four O-rings- about a dollar.

I also keep a latex glove in my gig bag to help remove any legs that are held too tightly. The glove works great on mic stands too, and takes up virtually no room at all.

Dave

Chris Lucker · From: Los Angeles, California USA

SEE IF THEY ARE IN TOLERANCE? Those threads are not exactly precision to begin with, and you cannot realistically machine fine precision threads in aluminum endplates anyway. Aluminum is too weak. For example,if you were to tap a hole for a #10 screw in aluminum it is recommended that you use 10-24 rather than the finer 10-32 as the courser 10-24 will retain its integrity better in aluminum. It is easy to visualize that when the depth of a thread is constant for a #10 screw 24 threads per inch will offer greater thread strength than 32 threads per inch.
Perhaps someone should machine Acme threads into tool steel male and female pieces that may be inserted into legs and endplates? Acme threads are strong and don't have the pointy ridges that can get dented and bent out of shape.
While I am on the topic of aluminum, don't fall for the old "Aircraft Aluminum" BS. There are so many different grades of aluminum found in airplane construction that the term "Aircraft Aluminum" is meaningless if it is used to imply strength. I would imaging it is harder to find a grade of aluminum NOT used somewhere in an airplane.
Chris

Roger Shackelton · From: MINNESOTA (deceased)

Hi Chris, I thought 7075 Grade Aluminum was considered to be Aircraft Aluminum.??

Roger

Chris Lucker · From: Los Angeles, California USA

Well to partially answer your question, here is a list of at least nine of the aluminum grades that are specified for use in aircraft landing gear tubing alone:

2011-T3, 2219,2024-T4, 2024-T6, 6061-T6, 7075-T6, 7075-T6, 7075-7351, 7050

Mentioned in there is the common 6061-T6.

But you are correct that the 7000 series is often referred to as "aircraft aluminum."

I am not a machinist, but I play one in the garage.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

The majority of aluminum in a modern commercial jetliner is 5052, 6061, and 7075. Some of the lower grades (1100 and 3000 series) are quite soft, and find very little use in aircraft. These are the grades that aren't heat-treatable, and shouldn't be referred to as "aircraft aluminum". The 7075 grade is the cream of the crop in strength, and well over 90% of that grade that's manufactured goes to two companies, Boeing and Airbus.

Most of the leg problems I've encountered are loose inserts in the legs. With reasonable care and a little lubrication every year of so, the leg threads (in the endplates) will last as long as the rest of the guitar, though a 50 year old Sho~Bud or Marlin might be getting a little "wobbley"! Laughing

Scott Appleton · From: Ashland, Oregon

So I should replace both the end plates or have some hard steel threaded parts installed by a machinist?
This 12 string Emmons i have is way wobbly and I know
I must do something other than use 0 rings .. that works .. i tried it but it just bothers me that there is that much slop in the union. I can move the legs a good 3 or 4 inches ether direction before the leg hits the endplate. My sho bud was not that bad. My MSA was getting that way before I sold it. This Beast is 30 + years old and I want to referb as best I can.
Any other hints out there.

Paul Redmond · From: Illinois, USA

In most cases, the 'seat' where the shoulder of the leg plugs rest on the endplates, become rounded as do the leg plus themselves. I usually take a countersink and run the chamfer at the mouth of the threaded hole to a larger diameter. Usually somewhere between 5/8" and 11/16". This forces the shoulder on the leg plug to seat out further toward the OD of the 7/8" leg. Even with worn threads, this will usually allow them to be much more stable. I always mark legs 1 thru 4 and always install them on the guitar in their respective holes in the endplates. As trivial as this may seem, if a thread gets a ding on it on one of the legs, if you then thread it into a different hole, the ding cuts a little more material out of the thread, and so and so on. If each threaded plug has a slightly different thread, burr, rough area, etc., it just keeps recutting all the tapped endplate holes. Using the same leg in its respective endplate hole at least ensures that the threads are travelling over 'familiar' roads and not carving new ones. You must use a leg pouch to help protect those threaded plugs from getting all dinged up in the first place. Ironically I knew a guy with a Sho-Bud D-10 who never used a leg pouch and his guitar was as wobbly as a drunk. There were hardly any threads left in his endplates!!
PRR

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