Changing a bridge
 

Over the winter months I had the neck reset on my archtop and it came back with a new taller bridge. Now with summer I think the arch of the top has increased. The action has come up and I've lowered the saddle as far as it can go and I'd still like to bring it down a bit more. I have the old bridge. Is it pretty straight forward to swap them? Would the posts likely work in either bridge & are they easy to take out & put into the old bridge? I haven't found anything online yet about installing the posts. Do they just drop in?

FYI classical string players often have "summer" and "winter" bridges for much the same reason; since your old bridge is already fitted to the top, I'd do a straight swap - just loosen the strings, replace, and retune...

So I can expect the saddle posts to just drop in to the old shorter bridge?

You can't "expect" it, but it might happen. There are a few standards for the spacing of the posts (like to match a tune-o-matic bridge) but not all will be the same. You can always measure and see, or take the new bridge off and put the old one back on and see if you get your action as desired. Is it a wooden bridge base with a wooden topper/saddle? You can make a new saddle if you have skills, with slightly fewer skills you can plane or sand the bottom of the saddle to get more adjustment room, with no skills you can get a luthier to do it for you.

Edit: closely inspect the neck joint. I had my old Epiphone's neck reset, it failed after six months with resulting high action, the well-regarded luthier reset it again (for free), it failed again after six months, apparently the warranty expired and I am on my own now. The tell-tale in all cases was a gap developing at the neck heel, and a visible decrease in the gap under the fretboard extension. Having built six guitars between then and now and developed a few skills I didn't have, I am actually just about to reset it again, and look extremely closely for a root cause. The first neck install lasted 70 years, after all...

Brian

re: The posts, I think it's the same saddle on a new bridge so expect the spacing would be the same. I've never done this before so I don't know if the posts just lift out or if they're fastened in somehow. I've found info online about changing bridges but nothing specific to the saddle & posts. Maybe that means there's nothing to that. Guess I'll find out when I get to changing the strings. As for the neck set itself, yeah, it's occurred to me but I don't see any sign of separation at the heel. I couldn't say for sure about the elevation of the fret board, I don't have a measurement or anything. The work was done at the shop where it was built & they seem to have a spotless reputation. I'm inclined to think it's a summertime swelling of the top. I haven't run into this before but I haven't had an archtop guitar before either and I gather that this isn't uncommon with archtops?. (I do have a mandolin, same builder, haven't seen this sort of change) I did send an email to the shop a while back & was advised to try adjusting the truss rod (no mention of switching the bridge back to the old). The neck had seemed perfectly straight to me but I gave it a slight turn (not more than a quarter) Now I have a slight relief, less than .005 (my thinnest feeler) no change in the action though. I thought the advice was a little odd as I'm under the impression that adjusting the neck in that way would have minimal if any effect on action. Never the less, I sent a message back with the result (he'd said "let me know") No response to that though. I suppose maybe it seems kind of minor to experienced players? I had the action at a comfortable to me 5/64 with a bit of saddle height. Now the saddle is lowered all the way action is at 1/8.

No I would not expect that at all, unless the same person used the same hardware to make each bridge. However, if each bridge is a complete (base and saddle) bridge and each base has been fitted to your guitar's top then swapping them out is pretty easy. If you're just swapping saddles and if they are interchangeable on your base that's simple too. The posts stay with the base and the saddle just slips off/on. May as well put on a new set of Martin Retro monel .013's while you're at it.

That is a lot of top movement, in my opinion. 5/64 to 1/8" action change needs almost 1/10" movement at the bridge, plus you imply you changed the adjusters to their lowest, so add that in, your top to neck angle has changed by perhaps as much as 1/8" at the bridge. Mine don't move that much unless something is broken. I have one that has a non-adjustable solid bridge, and it's action doesn't change enough to notice over a year.

But change it has & I don't see signs of stress, cracks, separation, checking. I changed back to the old bridge today & the action is set to 4/64ths on the bass side at the 12th. There must be about 3/16 of post showing now. On a side note, I'd ordered up some of those Martin monel retro's but they're only wound to 36" and I need probably close to 39" on my D & G the way the tail piece is set up so I didn't put those on. It's not like I've tried a ton of different strings on this guitar but all the others I have gotten were wound to 40 inches. What's up with Martin?

Bridge post spaceing
 

Nope some bridges are different post spaceings, measure the distance from post to post . most Bridges will give a dimention for the post to post spaceing and Hole size .mm