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Thread: My first build: left-handed JM-1L

  1. #1
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    My first build: left-handed JM-1L

    Just got a JM-1L kit delivered today. It looks quite good, the wood is pretty nice. I'm thinking either a nice light stain or just satin poly to seal it would look great. The frets are pretty good but still need to be levelled and smoothed. The wood is smooth already and won't need much work.



    Two questions:
    1. The neck fit is a bit too tight. Do I only sand on the sides that I have circled in the picture?
    2. The bridge is weird, it is not mentioned in the instruction pdf. It is kind of like a strat but doesn't have mounting screws. Does it basically just get wedged under the two posts? Also one of the posts is not a super tight fit, I'd be kind of worried about it falling out, is there anything I should do there or is it all good once everything is wedged in?
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  2. #2
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    Hi Jarro,
    Couple of things
    - the kit comes from Perth - the timber will need to settle. Sydney's climate is very different and the timber will expand and contract. Give it time to adjust to the different climate. Better for it to be tight than loose. You can always rub a little was or soap to make the neck slide into the pocket, but wait a few weeks.
    - the bushing for the post should be reasonably tight. When you are applying finish to the body it will probably tighten. Once again the timber needs to acclimatise.
    - the bridge is different. I will see if I can find some photos of how it fits.

    For now, start sanding. Up to a maximum of 240 grit. Too high and you polish the timber and the stain will not soak in.

    Hope that helps.

    Edit:
    Couple of builds to look at for fitting the bridge
    https://www.buildyourownguitar.com.a...ead.php?t=7788
    https://www.buildyourownguitar.com.a...ead.php?t=8865
    Last edited by colin2121; 22-07-2021 at 01:11 PM.

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    I should have clarified, by a bit too tight I mean that it doesn't quite go all the way in, there is about 2-3mm of gap. Although when I measure the scale length with where the bridge will sit it actually looks right. So is it supposed to go all the way in, or does leaving it where it is as long as everything is straight work just fine?

  4. #4
    GAStronomist Simon Barden's Avatar
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    As the neck widens as it goes along, the neck drops in from the top, you can't slide it in.

    If the holes in the neck for the screws have been pre-drilled, and with the screws in position the neck has that gap, then that's wrong. If it's something else, then a photo would be helpful. Unfortunately the way the necks on the kits fit into the neck pockets often leave a bit to be desired in the way they mate up. Sometimes you can sand the end of the neck for a better fit, but if the scratchplate hides any gap, then I wouldn't worry too much about it.

    Those two-point trems are always a balancing act and the trem will fall out if you let it. But it's the the same on any 2-point trem, be it Fender or Floyd Rose or an Ibanez one etc.

    Don't bother fitting it in place until you are ready to string up. You need the trem claw installed (not forgetting its ground wire). It's best to wedge the trem block in place once you've fitted it so that it can't move backwards and forwards. If you can make a wooden wedge for each side, or glue bits of card together. I also use masking tape along the main axis of the guitar to hold the bridge in place against the posts, leaving the two E saddles clear so you can run strings from them to the tuners so the string tension then holds the saddle in place. You can then remove the tape and fit the other strings. At some point you can fit two or three of the trem springs. I'd fit two to start with so you can keep the wedges holding the block central with the springs to either side.

    The trem base plate should be sitting about 1/8" / 3mm from the body and parallel to it. You want it flat, and not angled backwards or forwards for best trem performance, so adjust the post heights and any wedges. If you only want down bends, not up and down, then you can set the bridge plate a bit lower, but you still want it at least 1mm above the body and parallel to it.

    Use the kit strings in the clear plastic wallet for initial set up, then use the Ernie Balls once you are happy (the kit strings are really bad, have uneven string to string response and sound dull, but if you need to take the strings on and off at all during setup, better to do it with the bad set).

    With the wedges in place and the strings fitted, you can then set up the bridge saddles for correct string height. If the saddles are as low and they can go and the action is too high (having first set up the truss rod for very slight concave neck relief), then it's best to fit a small shim in the neck pocket to increase the neck angle so the saddles can be adjusted to suit you. The shim won't need to be thick. A piece of veneer or a bit of old credit card should do. Just use something fairly hard, not too soft like card or paper.

    Once the action is set up, you can then remove the wedges and adjust the trem claw screws to bring the trem plate back to parallel again. You'll probably need to adjust the claw spring and string tuning a few times before it all settles down. However this is no different to a 6-screw trem. The only difference is that a 2-post trem will fall out when not held in by string and spring tension.

    I'd then swap to the good strings, changing them one at a time. Always best to change the strings one at a time on this type of trem to keep it in place, unless you need all the strings off to oil the fretboard or polish the frets.

    The trem posts and the post inserts should be the same size. Have you measured and checked? You normally wouldn't want to try fitting the post inserts into the body until you've applied the finish. You can do, but you'd probably then want to fit some suitable bolts (probably M6 for those posts) into the holes to stop the threads getting filed with finish.

    The holes in the body for the posts should be roughly the same diameter as the post inserts less the depth of the splines. They certainly shouldn't just drop in and pull out, you'll definitely need to tap them in quite hard with a hammer. So if you can drop them in, that's very wrong and they may have used the wrong drill bit. Those 2-post inserts are smaller than most of the post inserts used on other kits. If the holes are too big, I'd send the kit back. If you were more confident, you could fill the holes then re-drill, but you really need a drill press to do it and it's easy to mess things up. Plus if you are staining rather than painting a solid colour, you'll see the edges of the plugs.

    If in doubt, take and post pictures. And measure and check as much as possible. I find a set of cheap digital callipers are invaluable when working on guitars for checking all sorts of things.

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    Quote Originally Posted by jarro_2783 View Post
    I should have clarified, by a bit too tight I mean that it doesn't quite go all the way in, there is about 2-3mm of gap. Although when I measure the scale length with where the bridge will sit it actually looks right. So is it supposed to go all the way in, or does leaving it where it is as long as everything is straight work just fine?
    As I mentioned, give the timber time to acclimatise.
    When you push the neck into place post some photos. That makes it easier to assess.
    Remember, the pickguard should cover any tiny gaps between neck and body.

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    Thanks for the detailed instructions, that should help when I come to the bridge.

    If I put the neck in as snug as I can get it, there is a tiny bit of space at the end:


    Although it seems to have less space on the other side:


    With the pick guard on it fits flush and you can't even tell that there is a gap:


    For the bridge posts, they are snug, but I can get them in and out with my fingers. I don't have calipers to measure. I could probably just work around this by stuffing a couple of toothpicks or something in there and make it tighter.

  7. #7
    GAStronomist Simon Barden's Avatar
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    Whilst you can finesse the end of the neck to fit the pocket, if you can't see it, then it doesn't really matter as it will touch the end of the pocket at one point and that's all you really need.

    But if those post inserts are just finger tight, that is definitely wrong. Whilst I'd happily fix scratchplate screw holes with cocktail sticks, the trem posts exert a lot of force on the wood and you need a solid foundation round them. Now it may be that the holes were drilled for a different bridge that has slightly wider posts (I'd expect the Chinese kits all to use metric sized posts but some other trems have imperial sized posts), or it may just be that they used the wrong sized bit. But it's not right and I'd notify Pit Bull and get it replaced. The neck gap is minor, but over-large post-holes are major items.

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    Ok thanks, yeah I agree the neck fits fine, I'll make it work.

    I've emailed PBG, so I'll see what they say. Although I did a bit of googling and other people seem to have similar problems. They solve it with a combination of plumbers tape, aluminium tape, a bit of extra varnish or some PVA glue. All of that seems plausible to me, but we'll see what PBG say I guess. If it's a matter of sending back the body I guess I just have to wait a bit longer.

  9. #9
    GAStronomist Simon Barden's Avatar
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    As the post hole size seems wrong, have you checked whether they are drilled in the correct place? The factories do get it wrong from time to time.

    As you can insert and remove the post + inserts, I'd put those in, clamp the neck in place (if you don't want to screw it on yet), then run string down from the top and bottom E string locations to the top and bottom E saddles on the bridge. You can run string up the fretboard, down through the top E string tuner hole, back up through the through the bottom E tuner hole and back down the fretboard. You may need some masking tape to hold things in place bit you can set the post height low so the bridge sits mainly flat on the body.

    The position of the semicircular cut-out on the treble side of the bridge plate determines where the bridge sits; the other pivot point is flat so it's bridge post positioning is less crucial. The strings should run parallel to the sides of the neck a couple of mm in. Any slight misalignment can often be sorted by pulling the neck to one side or the other and screwing the neck down hard in that position. but anything major indicates the post holes are in the wrong place.

    This would also be a good time to check that the bridge is correctly positioned with respect to the neck scale length (which should be 25.5"/648mm). Measure from the top E slot to the top E bridge, with the top E saddle set almost fully forwards. The point the string leaves the saddle is slightly back from the front edge by about 1mm, so take that into account when measuring.

    If I wasn't going to plug and redrill, then after determining that the holes are in the right position, I'd probably epoxy the inserts in. You won't get them out again without drilling them out, but you shouldn't need to. The post threads will be a standard size, so if you ever need to replace then, any other 2-post bridge posts should fit. If you feel you might want to remove the inserts in the future, then I'd probably cut small slivers of maple (or another firm hardwood) veneer and stick them to the side of the post holes, a few at a time using PVA or Titebond. I'd use a smaller wooden dowel wrapped in cling-film (top prevent it sticking) to hold the veneer in place whilst drying. I'd do it in stages, maybe three at a time at 120 to each other. I've tried bending soaked veneer into a circular shape to fit larger diameter holes, and it didn't work well - a lot of splitting - so I resorted to using a lot of slim vertical 'matchsticks'. The veneer to wood join should be stronger than the wood, and you then still get the insert to wood compression.

    If the holes aren't in the right place, then the kit definitely needs to go back.

    Plumbers (PTFE) tape isn't a good idea, as you are using one of the slipperiest known substances to try and increase friction between the inserts and the wood. Its purpose in plumbing is to lubricate the threads on a joint so the nut can be turned as tight as possible up to squash an 'olive' into the gap between two bits of pipe to make it watertight. It is not a good gap filler.

    PVA glue can increase grip, but it doesn't adhere to metal (it adheres to cellulose in wood), so you rely on it running into small imperfections in the inserts and setting hard enough to stop movement. PVA is good in a thin layer between two pieces of wood, but the bigger the gap and the thicker the glue layer, the weaker the join. It will help, but is far from ideal.

    I've used copper tape to try and reduce oversized tuner holes to fit push-in bushings, but it wasn't very successful so chose another method. It always ended up being partially pushed down by the bushing, and if you wrapped it around the post insert and then pushed it in, a lot of the tape will be pushed back up the bushing. You may manage to get the top half of the insert held in place, with the tape, but it's very hard to get it all held in place with the tape if you use enough tape to hold the insert firmly.

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    Thanks for your detailed response, it sounds like anything is possible if you know how to fiddle around. Since this is my first kit I think swapping it for another is probably a good idea at this point though. PBG said to let it acclimatise and see how it goes, and they checked other kits and said they are tight, and they're happy to swap if it's still not tight after a week.
    I got about 322mm from 12th fret to bridge saddle with it extended fully, and putting two strings in place lined up. I'm not sure if that 2mm means it is in the wrong spot or if you would just wind it all back.

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