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"High" Action on J-45


jchabalk
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I have a D-28 Authentic and i really like how it plays. The action is a bit high  (higher than my other guitars anyway). The intonation is great and i can really dig in. I really like it. It's strung with EJ17 / mediums.

  • Low E @12th fret: .105
  • High E @12th fret: .080

My J-45 (same EJ17 / medium strings) hasn't been worked on in a while, the action was definitely lower and i've been getting a lot of fret buzz, so i took it in for a setup. Before the setup the action was this (and there was a bit of relief, i didn't measure it but it wasn't dead flat and definitely no backbow):

  • Low E @12th fret: .095
  • High E@12th fret: .080

When i got it back the action was measured at .085/.075 (bass/treble) with .007" of relief.

I'm going to take my J-45 back for some additional adjustment and i'd really like to match the playability of my D-28, but i'm uncertain what to ask for. The variables that i'm aware of that complicate this are short scale (J-45) vs. long scale (D-28) - which seems like the big one, and i guess the frets or stability of the fret board is the other.

I've got a saddle blank that i'm going to mess around with to see if i can either do this myself or get close but i'm mostly trying to figure out the best way to get what i want across to the shop.

My plan right now is to first match the action of my D-28 and see if it's close and if the intonation is acceptable, after that i'm not sure.

Any advice on acceptably stable "high" action on a short scale guitar?

I just fit the saddle blank (it's from bob colosi and so is shaped pretty well already). Action's a good bit higher than my D-28 and the intonation is definitely off due the height i'm sure as well as some adjustment being needed, so i'm trying to figure out my approach.

 

 

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You did not mention the string height at the the 1st fret which is controlled mainly by the nut slot depths. This will affect your feel of the guitar. You may want to compare them

You may already know this - The 12th fret is the mid point of the scale. For every .001" you deepen a nut slot or shorten your saddle the action will drop .0005" at the 12th so basically a 2:1 ratio. I normally measure the E strings like you have, mark the string locations on the saddle with a pencil, remove the saddle, measure the saddle height at those two locations then remove twice the amount that I want to lower the action. I use a handy saddle sander from Stewmac. The height of the tool is 1.000" so it's easy to adjust the screws at the two locations to expose exactly the amount that you want to remove plus it's flat and square and fast and comes out perfect every time.

Good luck

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-nuts-and-saddles/nut-and-saddle-sander/

4047-1-in-use-1600.jpg?width=62&height=6

 

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Thanks Dave! yes, i know... just enough to shoot myself in the foot with this sort of thing. My action measurements were done with a capo at the first fret (i should have mentioned that). I will compare nut height - i should have done that already - the shop that did the setup did make a minor adjustment there.

For me to lower the action appropriately it will require taking a different amount off of the treble and bass side of the saddle, something i don't have a great way to do. I've tried to do this before and never really gotten good at it. I have use a marble countertop (or piece of glass), sandpaper and my hands. I'm ok at taking an even amount off of the entire saddle, but the slanted line causes me trouble.

 

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The guitar is setup at the factory for light gauge (12) strings. Mediums will throw off nearly everything - nut slot depth and width in particular. A j45 can “handle” mediums, but I’ve found that lights on my J45 closely mimick the feel of mediums on my D28. 

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interesting, i'd always thought it was the other way around:

lower tension mediums on a short scale guitar would have a similar feel to high tension light strings on a longer scale guitar.

I've had this J-45 set up for mediums before and this particular trip to the shop was to try to get rid of the buzzing and raise the action a bit. Every time i do this it makes me want to keep just one guitar so i don't have these playability differences knocking me out of whack 😉

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I had an unused saddle blank in my stash of parts and figured i'd give it a shot so i don't need to make another trip. I was able to shape it and match the action of my D-28, the intonation is pretty well spot on as well - best work i've done on a saddle yet. I figured that matching the D-28 action would be the upper bound and maybe I'll bring it down a bit in the future.

I finished it up this morning and like it a whole lot better than the lower action the shop had set it up with.

So now i'm sitting at (with capo on the 1st fret):

  • .105 low E at 12th fret
  • .080 high E at 12th fret

It's certainly on the high side

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On 8/6/2021 at 10:15 PM, Dave F said:

You did not mention the string height at the the 1st fret which is controlled mainly by the nut slot depths. This will affect your feel of the guitar. You may want to compare them

You may already know this - The 12th fret is the mid point of the scale. For every .001" you deepen a nut slot or shorten your saddle the action will drop .0005" at the 12th so basically a 2:1 ratio. I normally measure the E strings like you have, mark the string locations on the saddle with a pencil, remove the saddle, measure the saddle height at those two locations then remove twice the amount that I want to lower the action. I use a handy saddle sander from Stewmac. The height of the tool is 1.000" so it's easy to adjust the screws at the two locations to expose exactly the amount that you want to remove plus it's flat and square and fast and comes out perfect every time.

Good luck

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-nuts-and-saddles/nut-and-saddle-sander/

4047-1-in-use-1600.jpg?width=62&height=6

 

Dave, that's a cool gizmo that I didn't know existed. Thanks!

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