Machine Head Problem Fender MIM Jazz Bass

[Montblanc]

Recently black plastic has started appearing around the machine heads of my MIM J Bass. On further investigation there appears to be plastic "shims" which are breaking up under the gear. Has anyone else had this problem? Why, after all these years, are they breaking up now? Is the plastic important, what function do they serve - i.e. can I just remove and discard them? If not; are replacement shims available without having to buy a set of complete machine heads? Has this subject been discussed before on the forum as I can't find any threads but it's difficult to believe this is a unique case? Any advice would be appreciated. Cheers, Neil

 

[bholder]

They might serve as friction reduction washers. I'd try putting it back together without and see what happens. Or you could always find some plastic of appropriate thickness and cut new ones.

 

[LoveThatBass]

They might serve as friction reduction washers. I'd try putting it back together without and see what happens. Or you could always find some plastic of appropriate thickness and cut new ones.

Also, you could get those round hole protectors for paper (if the center is large enough diameter) and use them Or look for very thin round donut washer. You might get buy with one slightly thicker with now problem. Go to Ace Hardware or Hobby Shop

 

[Bruce Johnson]

Ah yes...the Schaller slip sheets. Those tuners are, I believe, made by Schaller for Fender. That friction plate design is used on Schaller's classic BLM series tuners. I deal with them all the time, because I modify Schaller BLM's to use on my Scroll Basses.

Note the thin steel plate that's under the black plastic. It's sticking up at an angle, and the longer side of it fits underneath the worm (the spiral gear on the key shaft). That plate is called the friction plate. It's made from thin spring steel. When you put the gear on the post and tighten it down, the gear pushes down on the friction plate, which then pushes up on the underside of the worm. That's how this design of tuner creates the friction drag on the key shaft; The outside of the worm rubs on the friction plate. The drag is controlled by the springiness of the plate.

The black plastic part is the slip sheet. It's made of thin Mylar or Acetate, cut to the same shape as the friction plate. It sits right on top of the friction plate, with its long end sticking down between the friction plate and the underside of the worm. It acts as a slippery washer under the back face of the gear, but its main purpose is to prevent the worm from wearing itself out from rubbing against the friction plate. That's why it's there. Over time, the slip sheet will crack or split, and the overhanging end will get jammed out from under the worm and tangled up in the teeth.

You can reassemble the tuner without the slip sheet, and it will function okay for a while. But eventually, the tuner will start grinding, and you'll see that the plating on the outside of the worm will be wearing and peeling off. The plating chips will then get into the teeth, and then the tuner will be grinding even worse and get hard to turn. Basically ruined.

I don't know if you can buy replacement slip sheet kits. You'd have to ask Fender or Schaller. You can make up replacements from some thin Mylar or Acetate sheet from a hobby shop. Cut them out with scissors and a knife. Or, stick a piece of clear packaging tape onto the friction plate and then trim around it with a sharp knife. I've done that few times. Good packaging tape, like 3M Scotch, is thin Mylar and is very strong and slippery.

 

[Montblanc]

[/QUOTE]

Ah yes...the Schaller slip sheets. Those tuners are, I believe, made by Schaller for Fender. That friction plate design is used on Schaller's classic BLM series tuners. I deal with them all the time, because I modify Schaller BLM's to use on my Scroll Basses.

Note the thin steel plate that's under the black plastic. It's sticking up at an angle, and the longer side of it fits underneath the worm (the spiral gear on the key shaft). That plate is called the friction plate. It's made from thin spring steel. When you put the gear on the post and tighten it down, the gear pushes down on the friction plate, which then pushes up on the underside of the worm. That's how this design of tuner creates the friction drag on the key shaft; The outside of the worm rubs on the friction plate. The drag is controlled by the springiness of the plate.

The black plastic part is the slip sheet. It's made of thin Mylar or Acetate, cut to the same shape as the friction plate. It sits right on top of the friction plate, with its long end sticking down between the friction plate and the underside of the worm. It acts as a slippery washer under the back face of the gear, but its main purpose is to prevent the worm from wearing itself out from rubbing against the friction plate. That's why it's there. Over time, the slip sheet will crack or split, and the overhanging end will get jammed out from under the worm and tangled up in the teeth.

You can reassemble the tuner without the slip sheet, and it will function okay for a while. But eventually, the tuner will start grinding, and you'll see that the plating on the outside of the worm will be wearing and peeling off. The plating chips will then get into the teeth, and then the tuner will be grinding even worse and get hard to turn. Basically ruined.

I don't know if you can buy replacement slip sheet kits. You'd have to ask Fender or Schaller. You can make up replacements from some thin Mylar or Acetate sheet from a hobby shop. Cut them out with scissors and a knife. Or, stick a piece of clear packaging tape onto the friction plate and then trim around it with a sharp knife. I've done that few times. Good packaging tape, like 3M Scotch, is thin Mylar and is very strong and slippery.

Thanks Bruce - a well crafted answer from someone who obviously knows his trade. This is my back-up bass but it plays nicely and I use it for that "old school" sound with flat wound strings so I'd like keep it original. I'll try your packing tape idea for the time being while I contact Fender and Schaller to see if the slip sheets are available. I fear its probably a case of buying a new set of tuners: anybody know the Fender part number for tuners for this 1982 Mexico Jazz Bass? I'd prefer to use the existing screw holes.

 

[callofcthulhu]

 

[96tbird]

Once, I made new sheets with a Tropicana orange juice jug that worked great. Very thin and very durable plastic.

Never thought of the quality packing tape trick.... Super idea! Do that. It will last years and is easy to redo as necessary.

 

[Montblanc]

I thought I would share with everyone the response I received from Fender Customer Relations:

Greg Armijo (Fender)

Aug 1, 08:16 MST

Hello,

Unfortunately those plastic parts are not available. To replace them you would have to replace the whole instrument. Sorry for the inconvenience.

Regards,

Greg Armijo
Fender Consumer Relations
17600 North Perimeter Drive, Suite 100
Scottsdale AZ, 85255
(480) 845-5140

 

[Montblanc]

By contrast the Managing Director/Owner of Schaller could not have been more helpful:

Dear Neil,

many thanks, yes the answer from Fender is not satisfying…

These are definitely not Schaller tuners and we don`t use and have this plastic plate.


If you like you can order in our Schaller shop (button „shop“ at our website/frontpage) our BM tuners.

If Fender used for your instrument tuners with the international standard measurements our BM tuners will fit.

Please check in the product details of our BM tuners the tabs "technical drawings“ and "guidelines“.


Best regards

Lars


Schaller Electronic GmbH

Dr. Lars Bünning
Geschäftsführender Gesellschafter
Managing Director – Owner


An der Heide 15
92353 Postbauer-Heng
Deutschland/Germany
Nbg. HRB 22913
Steuer-Nr.: 201/138/00055
USt-IdNr.: DE 250 628 367
Tel.: 0049/(0)9180 910 0
e-mail: [email protected]
www.schaller-electronic.com

 

[GIBrat51]

I bought a set of Shaller BM tuners last year for a Warmoth Mini-P bass build, and had to take them apart to reverse them ("left-hand" refers to the side of the head stock - not me being left handed...) There is a plastic slip sheet in there, but IIRC, it's fairly thick, clear plastic, and not as big as the ones in your pics. Bruce's packing tape suggestion, as usual, is a very good one. I'd give it a try...

 

[sissy kathy]

Not only did Bruce have a good idea, but it may work better than the original slip sheets. With adhesive there, I think the sheet may stay put better than the slip sheet does.

 

[fhm555]

Here's your solution. .012" thick UHMW sheet with a sticky back. A square foot runs just over $6.00

Follow the linlk and do a search in the plastics tab, then pick the thickness you want.

McMaster-Carr

 

[Hopkins]

We used to have some very thin viton sheets used for making gaskets on pyrophoric gas compressors at work. That stuff would be perfect for this.

 

[Montblanc]

Further thoughts about this problem:
1. I have been playing around with different strings on this bass and have possible changed strings 6 time in the past year. Prior to that the strings may never have been changed!
2. I would say the failure mode (sorry: 35 years a Professional Engineer - it's the way I think) is the inability of the plastic to resist the worm gear's rotation in compression i.e. the tensile strength is adequate but the material wrinkles under compression - it is not stiff enough.
3. I have measured the thickness of the plastic and it is .012". It is not PVC, PTFE or HDPE and I suspect non of these would be stiff enough. Even with an adhesive backing I can't see packing tape being stiff enough. I can't identify the type of plastic: it may be some sort of acetate, acrylic or some unique branded product.
4. For the time being I have just removed the plastic from the worst affected tuners. I agree with Bruce that this may well increase wear between the spring strip and the worm gear resulting in the failure of the chrome plating.
5. Fender were useless at providing any explanation/solution
6. Schaller were as helpful as they could be but they don't make a tuner with suitable screw centers for direct replacement.

Conclusion: Cheap nasty tuners which no one wants to claim responsibility for designing - I should have bought a better quality Jazz Bass
At Lease my 2015 MIA Precision Bass looks to have better tuners!


Now for a question: Hipshot claim to make a replacement tuner for the MIM jazz Bass - the HB7. Has anyone had experience of these tuners? Better still has anyone change their MIM tuners for HB7s

 

[brendanbassix]

I agree with fender if one machine head breaks you should replace the whole instrument. Haha

seriously though I hope you find a fix that's both cheap and simple.

 

[96tbird]

All of Hipshot products are top notch. Don't hesitate.

 

[Olde Axeman]

I toyed with the idea of replacing the stock tuners on a Mexican Jazz bass I owned with HB7's. I ultimately chose not to replace the stock tuners because they were working fine but did some research and found numerous people who said the HB7's were a perfect drop-in fit. Smoother and lighter as well, or so they claimed. This should be the case as Hipshot designed the HB7 as a drop-in replacement for stock MIM basses.

A set of 4 HB7's in nickel is only $89 from Reverb with free shipping. I recommend that you obsess no more and simply go for the upgrade. Hipshot makes pretty good stuff.
Hipshot HB7 4 string Nickel 20710N upgrade for Fender MIM basses NEW auth dealer

You could also hedge your bets and buy only one HB7 tuner for $26 (+$2 shipping) to see if you like 'em or not and buy the other 3 later if the one tuner works out well.
Hipshot HB7 Machine Head Tuner Nickel Bass Side

 

[Montblanc]

I agree with fender if one machine head breaks you should replace the whole instrument. Haha

seriously though I hope you find a fix that's both cheap and simple.

They probably forgot to mention that their advice would only work if the replacement instrument was a "top of the range" Fender Custom Shop '62 re-issue Jazz Bass. I Wish!

 

[Montblanc]

It has been over a year and a half since I encountered this problem. Fender were of no help what so ever and I even wrote to Fender Mexico but they couldn't be bothered to reply!!! The sorce of the machine heads remains a mystery and I have been unable to find a replacements with the same screw centres.
What I have done is completey removed all the plastic slip shims without any I'll effects. Infact this improved one if the tuners which had become a little stiff due to the deteriorating plastic shim. So far I have not seen any problems with the chrome plating flaking off as was feared by one respondant. Time will tell. In conclusion take the crappy plastic shims and throw them in the trash if they cause you any problems

 

[Turnaround]

Now for a question: Hipshot claim to make a replacement tuner for the MIM jazz Bass - the HB7. Has anyone had experience of these tuners? Better still has anyone change their MIM tuners for HB7s

I have used HB7's on all my MIM Fenders. Very high quality tuner with a drop-in fit.