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Headless bass - intonation keeps slipping

Poobini

Poobini

Aug 1, 2019
495
1,124
MO/IL
#1
Hey folks!

I've got a headless bass with individual saddles, and the E string tuning head/bridge keeps sliding toward the neck, as if the tension from the string is too much for it to bear.

PXL_20251010_150345411.jpg


There are two allen screws in each head to lock the intonation, but for whatever reason it's not enough to totally lock down the E string.
To make matters stranger, there are four slots to put the screws in underneath the tuning heads, but all of them are at a bad enough spot to not get as in tune as possible. If I put it back all the way, it's way off. If I put it at the next closest spot, it's off in the other direction.

Really I'm just curious if anyone has any tips on getting these screws down tighter - I've tried blue loctite to get a better grip but it hasn't been too successful.
 
#2
First suggestion is to contact the manufacturer for assistance, as always.
Second, if not possible or they have no great ideas, if you can at least get the intonation dialed in, do whatever you can to mark that position (masking tape), that way you can pull things apart and re-gain that sweet spot. Once you've got that established, put an anchor screw at the rear of the adjustment slot, towards the butt of the instrument body. This will prevent the bridge from being yanked back toward the neck, spoiling your intonation.
I would only do this as a last act of desperation, unless you don't mid piloting holes where originally they weren't intended. But it would stop the slippage, if you can anchor a screw at the bottom of that slot vs over-torqueing a screw mid slot, which seems to be the point of failure. Hopefully, this can be done without interfering with the drop in tuner/string anchor mechanism.
Again, hopefully the MFG can give you a straightforward strategy without boring more holes or fouling the operation with a screw head in the way.

Good luck! Looks like a cool instrument!
 
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#5
Are there washers under both of the E-string intonation bolts? Are they just threading into wood or are there threaded metal inserts underneath that they screw into? Have you tried swapping the E-string bolts with each-other or with other ones? If these bolts are just threading into wood then this is a terrible design, and bound to wear out like this- I'd replace the bridge saddles with something like the Ibanez MR5HS bridge (the screws into the wood are fixed and intonation is done with a more traditional saddle mechanism). If they are threaded into metal inserts and all washers are present, then I'd probably just try to replace the bolts with their equivalent as I'd guess one is worn out or out of spec
 
#6
Sound to me like you might need to reinstall that tuner.
It could be the hole has striped, first move is take it off the bass and inspect the hole.
You could dowel and redrill it, or as mentioned above an insert might be your best bet.
Those screws are pretty small considering how much pull is on it.
Another option would be wood dust and glue slurry would fill it as well.
 
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#7
I agree with @sunbeast that this design is terrible. I've worked with a similar problem on a guitar version where a single tiny machine screw held each barrel down to a mounting plate. I hate that you cannot adjust the intonation without removing the string, but let's work on your problem.

Assuming BEADG tuning, I see the wear marks on the A barrel. You may be right in that the screws don't create enough down-force to hold a slotted hole in place.
  • If the screws go into wood, I repeat the advice above about metal inserts and machine screws.
  • If there already are inserts or mounting plates, inspect for thread damage and replace any worn parts.
  • could you add a third insert and screw on that barrel? Do all of them, while you are at it.
  • try sizing up on the screws, both length and diameter. Check first to make sure that larger screw heads don't interfere with the movement of the tuning block that holds the ball end.
 
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#8
sunbeast said:
Are there washers under both of the E-string intonation bolts? Are they just threading into wood or are there threaded metal inserts underneath that they screw into? Have you tried swapping the E-string bolts with each-other or with other ones? If these bolts are just threading into wood then this is a terrible design, and bound to wear out like this- I'd replace the bridge saddles with something like the Ibanez MR5HS bridge (the screws into the wood are fixed and intonation is done with a more traditional saddle mechanism). If they are threaded into metal inserts and all washers are present, then I'd probably just try to replace the bolts with their equivalent as I'd guess one is worn out or out of spec
Click to expand...

Thankfully it's mounted to a plate - I'll definitely try swapping out the screw first. Chances are I stripped something in trying to make some adjustments.
 
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#10
Sorry; I got nothing, beyond what others have said. My headless, aluminum-necked '82 Kramer "The Duke" Special uses a completely different set-up. The ball ends are in a toothed thing at the top; the strings run down to a normal Schaller 3D-4 roller bridge. they go over and through it - Backwards - and then, to 4 Schaller guitar-style tuners. It seems like a pretty "Rube Goldberg" arrangement on paper; but... if there's no problem with silks at the ball end? It works - flawlessly. In the 15+ years I've owned it? Bullet proof... :cool:
 
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#11
Poobini said:
Thankfully it's mounted to a plate - I'll definitely try swapping out the screw first. Chances are I stripped something in trying to make some adjustments.
Click to expand...

Do the cap screws snug-up when tightened? If yes, it's not stripped. The saddle / tuner "sled" sits atop a threaded base plate. From the description, I'm of the impression that the sled is slipping beneath the cap screw's washers...both of them...under 35 lbs of tension. Not sure why it only happened on one. The quick-fix would be to remove the flat washers and replace with a like-sized toothed washer.

What's the bass in question? As suggested, it's a questionable design.

Riis
 
#12
I see the A string set screw has made marks in the sled. Looks like it grips fine but I can’t see a washer under it. The e string definitely has washers. We have a friction problem.

Look at the washers. Washers are punched out of sheet steel and so have a side that is rounded and a side that has a proud edge around the circumference. Perhaps the smooth rounded side is against the sled. Maybe flipping the washer will place the rough side down and grip the sled. Or just remove the washer and see what happens.

I thought perhaps scoring the bottom of the sled and the base plate to create some friction might help too. Or roughing up the washer bottom.

But if possible a larger screw would afford more pressure.
 
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#14
The one that I had worked on before had the same problem. It was common enough of a problem that they stocked replacement plates. I see this as further evidence of bad design. The tiny screws that cost pennies and can be sourced locally should fail, instead of any custom designed plate.
 
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#15
I know I’m late to the party but it appears the us a clear tape strip under the E string screws but not under the rest of them. Did you do that? That tap would cause slippage.
 
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#16
Pep said:
I kniw I’m late to the party but it appears the us a clear tape strip under the E string screws but not under the rest of them. Did you do that? That tap would cause slippage.
Click to expand...
there's no tape, the powder coat is just chewed up from trying to get around in there. If you're talking about between the E and A, that's just a small bit of tape to keep the ground down. That's under the tuner mounts, so a non-issue.
 
#18
Poobini said:
Somehow the mounting plate got stripped. Thankfully I have another bass from the manufacturer that isn't getting played much at this time, so I just did a total tuner swap and setup. Thanks for all the insight folks. :)
Click to expand...
Dang- sounds like the design was almost as bad as screwing directly into wood! I hate that. Actual metal threaded inserts into the wood would have been more robust, but I just think that approach to intonation adjustment is a problem all around. I do have one bridge with a similar intonation mechanism, but the threads are tapped into solid brass so it is the bolts that would get stripped if anything (and I haven’t had a bolt strip out on this bridge in 20 years!). I hate to see throwaway design decisions like that with proprietary parts
 
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#19
sunbeast said:
Dang- sounds like the design was almost as bad as screwing directly into wood! I hate that. Actual metal threaded inserts into the wood would have been more robust, but I just think that approach to intonation adjustment is a problem all around. I do have one bridge with a similar intonation mechanism, but the threads are tapped into solid brass so it is the bolts that would get stripped if anything (and I haven’t had a bolt strip out on this bridge in 20 years!). I hate to see throwaway design decisions like that with proprietary parts
Click to expand...
The OP said the screws go into a metal plate, not the wood, and it’s stripped.
 
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#20
Pep said:
The OP said the screws go into a metal plate, not the wood, and it’s stripped.
Click to expand...
Exactly- I’m saying that a design that relies on screw friction to hold the full force of a string yet uses metal soft enough that a cheap bolt can strip it out is a bad design. The bolt should be the part that wears out if anything since it is a part that will require user adjustment anytime the user changes setup settings or switches to a different set of strings. I take the same issue with companies that use cheap metal for any part that will reasonably see adjustment (like truss rod nuts or pickup height screws, etc), but here the design is just inferior IMO and particularly so if using soft metal for the plate
 

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