Shoulder Eye-Bolts: washer or not?

Frank Koenig

Frank Koenig

Sophomore
Mar 7, 2011
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Palo Alto, CA USA
www.dunmovin.com
What is the best practice? The fly points on many loudspeakers are countersunk holes (typically 10 mm or 3/8 in.) which are filled by flat-head bolts when not in use. The manufacturers recommend shoulder eye-bolts for flying. Shoulder eye-bolts are designed with the intent that the shoulder bottoms against a flat surface. The ideal piece of hardware in this situation, it seems to me, would be a conical washer that has the included angle of the countersink. To my dismay, McMaster doesn't have these, so they are unlikely to exist :) So what to do?

With no washer the jagged edge of the shoulder gouges into the tapered side of the countersunk hole in the plywood, which is ugly and will wear out the hole with repeated insertions. Should one use a (hardened, grade 8) flat washer? I appreciate your guidance.

(And, yes, my eye-bolts are the expensive ones rated for overhead lifting.)

--Frank
 
Re: Shoulder Eye-Bolts: washer or not?

for my situations I'm generally only inserting the eye bolts once, so I'm ok with digging into the wood a bit.

The only reason I can think of NOT to use a washer is that usually the hole in the wood is larger than the bolt so unless the shoulder is wedged in that countersunk hole it could be pulled sideways a bit and the Tnut could move, or if it is into a tapped plate it may put stress on the threads in a direction that wasn't anticipated. This of course doesn't matter if you are dead-hanging straight from the eye bolts, but unless we're talking subs it seems that speakers always need to be on an angle.
But of course it depends...

Jason
 
Re: Shoulder Eye-Bolts: washer or not?

I ended up getting some JBL packaged M10 eyebolts. They included thin, wide washers for use under the shoulder. I had also wondered if there was going to be conical washers, but no. I have no experience with any brands other that the JBLs. If you want me to measure the washer for your reference, let me know. Mark C.
 
Re: Shoulder Eye-Bolts: washer or not?

Frank Koenig said:
What is the best practice? The fly points on many loudspeakers are countersunk holes (typically 10 mm or 3/8 in.) which are filled by flat-head bolts when not in use. The manufacturers recommend shoulder eye-bolts for flying. Shoulder eye-bolts are designed with the intent that the shoulder bottoms against a flat surface. The ideal piece of hardware in this situation, it seems to me, would be a conical washer that has the included angle of the countersink. To my dismay, McMaster doesn't have these, so they are unlikely to exist :) So what to do?

With no washer the jagged edge of the shoulder gouges into the tapered side of the countersunk hole in the plywood, which is ugly and will wear out the hole with repeated insertions. Should one use a (hardened, grade 8) flat washer? I appreciate your guidance.

(And, yes, my eye-bolts are the expensive ones rated for overhead lifting.)

--Frank
Click to expand...

Best practice would be to contact the manufacturer, after checking through all of their online literature, most should at least a small section of proper rigging.
 
Re: Shoulder Eye-Bolts: washer or not?

Spenser Hamilton said:
Best practice would be to contact the manufacturer, after checking through all of their online literature, most should at least a small section of proper rigging.
Click to expand...

I should note that I have JBL speakers. I figured that using JBL eyebolts on JBL speakers provides me with a fairly good argument that I had selected appropriate flying hardware. (For that part of the system, anyway.). Mark C.
 
Re: Shoulder Eye-Bolts: washer or not?

Mark Cadwallader said:
I should note that I have JBL speakers. I figured that using JBL eyebolts on JBL speakers provides me with a fairly good argument that I had selected appropriate flying hardware. (For that part of the system, anyway.). Mark C.
Click to expand...

If it was right from the manufacturer I'd be pretty confident, but it never hurts to crack the manual and double check that you are covering yourself from a liability standpoint.

We got some Mac 350s recently, the bolts that came with the 350s didn't fit the clamp we were using and the bolts that came with the clamps were the wrong grade, one trip to a hardware supplier later and we were in business. Sometimes it is best to double check and know that you are being safe than to just assume that what comes in the package is right.
 
Re: Shoulder Eye-Bolts: washer or not?

Frank Koenig said:
What is the best practice? The fly points on many loudspeakers are countersunk holes (typically 10 mm or 3/8 in.) which are filled by flat-head bolts when not in use. The manufacturers recommend shoulder eye-bolts for flying. Shoulder eye-bolts are designed with the intent that the shoulder bottoms against a flat surface. The ideal piece of hardware in this situation, it seems to me, would be a conical washer that has the included angle of the countersink. To my dismay, McMaster doesn't have these, so they are unlikely to exist :) So what to do?

With no washer the jagged edge of the shoulder gouges into the tapered side of the countersunk hole in the plywood, which is ugly and will wear out the hole with repeated insertions. Should one use a (hardened, grade 8) flat washer? I appreciate your guidance.

(And, yes, my eye-bolts are the expensive ones rated for overhead lifting.)

--Frank
Click to expand...

This always bothered me. You could have these conical washers made at a local machine shop.
 
Re: Shoulder Eye-Bolts: washer or not?

harrybrilljr said:
This always bothered me. You could have these conical washers made at a local machine shop.
Click to expand...

They would be tiny little bastards of a washer. It would be easier to turn them on a lathe with a flat washer surface attached to the cone-shaped spacer. It also occurs to me that in order to work right, the tolerance of the cone would have to be +0/- something in order to work. I don't know that speaker mfgs have close enough tolerances to not have the shoulder of the eye bolt bottoming out on the conical washer instead of the cabinet. There are rated machinery lifting swivel eyes for non-vertical lifts, but IIRC the price is about $70+ each. Not very cost efficient for a single speaker, given the over-engineering (high safety factor) for "regular" forged eyebolts on most single speakers. Mark C.
 
Re: Shoulder Eye-Bolts: washer or not?

Unless you're putting a heavy side load on the eye bolt, I would think the grade 8 would be fine? With the speaker hanging the eye bolt would be pulling away from the washer, so the only pressure on the washer would be the force of the shoulder bolt being tightened into the internal flying studs, which shouldn't deform a grade 8 washer.
 
Re: Shoulder Eye-Bolts: washer or not?

Thanks for all the replies. I see I'm not alone in having thought about this and that if I keep it up I'll qualify for the final round of the Sound Forums Anal Retentive Award.
For now I'll just jam them into the wood, but not too hard, and maybe use a little light-duty thread locker to keep them in a pretty position.
From a structural standpoint, even a single non-shoulder eye bolt with the pull at 90 deg is within its working load limit for this 115 lb speaker.

--Frank
 
Re: Shoulder Eye-Bolts: washer or not?

A late follow-up: FWIW, the washers included with the JBL M10 eyebolt kit measure:

Thickness: 1.5 mm(+\-.03 mm)
O.D.: 38.3 mm (+\- .10 mm)
I.D.: 10.4 mm (+\- .10 mm)

Measurements were taken with a Mitutoyo dial caliper, .02 mm resolution. Three samples measured. Let me know if you are interested in any other measurements. Sorry, I don't have a Brinnell tester at home.

Regards, Mark C.
 
Re: Shoulder Eye-Bolts: washer or not?

In a different industery we use these:
HOIST RINGS, SWIVEL HOIST RINGS, Swivel Hoist Rings :: Carr Lane Manufacturing Co.

The base of which is much, much bigger than eye-bolts. I'm not a rigger/engineer so I have no idea if these can even be used in sustained lifting of pro audio cabinets. I would be nice if someone with those qualifications would chime in, as I'm currious myself.

If you really worry about the section of countersunk wood, I would suggest "shooting" the bottom of the washer with bondo. You'd have to prep eveything for the bondo to release from the cab, and stick to the washer. If there is a serious intrest in this, I'll be happy to make some washers for a small fee. Any material you want, any thickness. I'd just need to know the depth and degree of the countersink.


-Kevin
 
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