400 tuning drum spring

ths71

Active Member
My 400 project is missing the little spring on the tuning drum. Any ideas on where to get one?
 
A donor/parts unit. You can get it tight enough without the spring but it's a PITA to do. All it really does is give a little cushion when you "hit the stops" to keep the incidence of cord breakage down.
 
My 400 project is missing the little spring on the tuning drum. Any ideas on where to get one?

I've seen springs sold in True Value Hardware store. You may have to try other hardware stores as well... They sell them in many different sizes. I'll attach a photo of the spring from my 400 and give you the spring dimensions. The only dimension that I can't measure is the force at the extended, mounted length. So it's important that you measure the prospective spring with a 1" micrometer or dial calipers. It doesn't have to be exact, but you want to have enough tension on that string so try to get it somewhat close... Here's the dimensions:

Wire diameter- .021
Body diameter- .240
# of active coils- 21
Body length without end loops- .447
Total spring length with end loops- .725

I used to set up and operate U.S. Baird Springenerators for Cherry, who makes snap action switches for just about anything that needs a switch. I worked at that job for 12 years making springs of all shapes, sizes, and forces. Very interesting job it was :) So when I saw that you needed a spring I just went bonkers!!:D
2013-09-10 02.51.27.jpg
 
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John; You've just been designated as the "spring-ologist" for the forum LOL!

Larry
 
If you have the details on the eye tube spring I will see if I can find a suitable replacement.

You're good, Apple:yes::thmbsp: Those look perfect. Could these possibly be added to Larry's "Sticky", Most Common Parts For Fisher? There's the spring for the magic eye tube as well.. It's great that McMaster has the perfect size, as custom springs can be hard to find.

John
 
you're good, apple:yes::thmbsp: Those look perfect. Could these possibly be added to larry's "sticky", most common parts for fisher? There's the spring for the magic eye tube as well.. It's great that mcmaster has the perfect size, as custom springs can be hard to find.

John

done!
 
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You guys are great. Got the dimensions, a source and unearthed a Spring Professional for any future spring questions.

Didn't realize it but I'm missing the spring for the magic eye tube as well. Looks like it would be easier to find something that would work there.
 
ths71. If you can't find a spring for the Eyetube, use a #4-40 or #6 x1-1/2" (adjust length to suit) bolt with a nut. My TA-600 has that setup (factory). Use a nut with knurled outer edge so you can grip it.

Larry
 
ths71. If you can't find a spring for the Eyetube, use a #4-40 or #6 x1-1/2" (adjust length to suit) bolt with a nut. My TA-600 has that setup (factory). Use a nut with knurled outer edge so you can grip it.

Larry

Thanks. I thought the spring just hooked up to the little slots.
 
It does. The slots can be expanded into holes for bolts. My TA-600 has bolts with nuts. FISHER probably changed to springs to keep hamhanded owners from over tightening the nuts and breaking tubes. All you need is finger tight. If you have springs fine, if you can't find them the bolt/nut is an option. to re-iterate this is for the tuning eye tube, not the tuning string tensioner
 
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Thanks. I thought the spring just hooked up to the little slots.
Hi ths71,
Glad that you found a spring for the tuning string tensioner(if that's what it's called).
I have the tuning eye spring dimensions measured already, but it was late so I'll post it tonight when I get home from work. That spring may be available from McMaster as well. I'll check that also..

John
 
Hi ths71,
Glad that you found a spring for the tuning string tensioner(if that's what it's called).
I have the tuning eye spring dimensions measured already, but it was late so I'll post it tonight when I get home from work. That spring may be available from McMaster as well. I'll check that also..

John
Here's the dimensions for the Fisher 400 magic eye tube retainer spring:

Wire Diameter- .022
Body Diameter- .211
# of active coils- 22 1/2
Free Length- 1.00"
End Loop Gaps- ~.125

The spring just needs to hold the tube in place, so the dimensions don't have to be dead on.

John
 
No prob. I'm happy that I can help.
Keep us posted on your progress with your 400. Check out Dave Gillespie's recent 400 posts if you haven't done so already. Good luck with your project!

John
Yeah, I'm keeping an eye on that. I actually found some springs locally I think might work and I built a dim bulb tester this weekend.

The chassis is about as clean as it's gonna get without drastic measures. I guess I can live with it and will let it wear it's scars as a badge of honor for surviving so many years of neglect. Or maybe that's why The Lord made wood cabinets. Luckily the face plate and dial glass are excellent after cleaning.
 
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