Neck swapping...

I think the problem lies in going from a 20 fret to a 21. Doing that you may run out of room to adjust the bridge saddles forward to achieve intonation, requiring moving the bridge to solve.

In your case you had plenty of room in your bridge adjustment to make it work! Good stuff!

 

Are you talking about Fender necks? 'Cause if you are, generally the 20- and 21-fret necks are the same size, and the 21st fret is simply an extension of the fingerboard that hangs over the pickguard - assuming that's what your previous neck was

 

It has noting to do with the number of frets. It has everything to do with where the 12th fret is positioned in relation to the nut and the bridge.

 

If the neck is a different length you may or may not have enough adjustment available at the bridge, but probably not. As Turnaround says above, the distance from the nut to the 12 fret should be the same as from the 12 fret to the bridge before you make small adjustments for intonation.

 

In cases where there the heel to bridge design spec is not identical, I would strongly advise against neck swapping.
I guess this case shows you can potentially get away with it. OCD me prefers not to see the bridge saddles scrunched so far back, but as long as it’s working, what the heck...
I am guessing that unlike standard Fender P & J, a suitable neck replacement for a Peavey Foundation must be harder to come by.

 

I put a 21-fret neck from an Ibanez Roadstar bass onto a Precision body and I repositioned the bridge in accordance with the scale length. I don’t think it would have worked out so well if I had just left the bridge in the original position.

 

sounds like you got this! nice ax!

 

I wouldn't necessarily adivse against it, but that's just me. If it fits the pocket (or very close), adjustments can be made to make a good fit. I've had to slightly widen neck pockets, shim the sides of pockets, move bridges up/back etc. (as long as as there is room to move it). If you don't mind a little extra work, it usually can be done with great success. And if there are some mods necessary to the pocket and or neck heel that permanently alters them, you have to decide if you those are changes you are willing to accept. Other than that, change away.

 

as long as we're being clear that it's about scale length/bridge placement not actually the number of frets, anything is possible.

i bet it often does not lead to a successful result, and im glad it worked for you!

 

You're only constrained by physics and real estate.
If it fits, it fits........if not, how much modification are you willing to attempt?
Golden rule is 12th fret equidistant between nut and bridge contact points.
Imagine trying to put one of Fender's 24 fret necks on a traditional jazz body. To make that combo go you'd have to move the bridge forward so much it may interfere with, or eliminate, the bridge PU position.
Most would find this objectionable, but to each his own.
If you were swapping from a 24 to a 20, there's not enough body to move the bridge far enough away from the nut.
As in many endeavors, reality and your willingness to hack are the limiting factors.
The results achieved are totally subjective.

 

Yes - getting the 12th fret to be halfway between the nut and bridge (with the bridge saddles moved as close to the nut as they will go is the goal. Another way of ensuring this is measuring the distance from the edge of the neck pocket to the bridge - if those dimensions are the same on two basses, then a swap is an option (assuming the bolt patterns are also the same).

Fender has, at times, produced guitars (Musicmasters for example) which were available in two scales - 24ish and 22.7ish. The longer scale had one more fret on a longer neck, but the bodies were the same.

If you look at Fender's history, almost all of their instruments are produced with a variation (interpolation or extrapolation) on the Telecaster scale. Their short scale guitars are the same as a capo on the first fret, their student guitars are the same as a capo on the second fret. Their baritone guitars are the same scale as a Telecaster with 1 (or 2) more fret(s) added, their basses are the same as a Telecaster with 3 (short scale), 4 (Japanese/medium scale), or 5 (34 inch long scale) frets added. Measure the distance from your 5th fret on your P or J to the bridge - that's a Telecaster. In fact, any fret from the 1st to the 7th is another Fender product's scale.

 

Reminds me of the Reverend Rumblefish basses. The 4 string and the 5 string used the same body. The bridge on the 5 had a corner that hung off the body just a smidge while the 4 string sat comfortably within the boundaries of the body. 34" vs 35".

 

Glad it worked out for you.

 

Yup, this ^ (and a bunch of other posts that basically said this).

As long as the math is right, everything should work fine. Whether or not you can position neck and bridge so it works out will vary from situation to situation. I suppose drastically moving the bridge changes where the pickups are in relation to scale which may or may not have an affect on the end result, again it depends on what neck and body.

 

More precisely, as you butt the heel of the neck all the way into the pocket, the distance from the fret board edge of the nut to the center of the 12th fret needs to be the same as the center of the 12th fret to the witness point on the G string (or C if a 6-string) with the G-string saddle screwed all the way to the front, nearest the pickup, without losing the intonation screw.