Poppet under the knife....
Easy does it for today.Maybe a few taps this evening as it is veryclose and dry here today.
Wait for the thunderclap and off she'll come...
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Double Bass Double Bass snapped at the heel
- Thread starter EAME
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- double double bass heel
Poppet under the knife....
Easy does it for today.Maybe a few taps this evening as it is veryclose and dry here today.
Wait for the thunderclap and off she'll come...
Yes mate of course I'm looking at construction,that goes unsaid.Be foolish not to.I have other instruments and am always fascinated by their construction.
This is a learning curve.
By the way,thanks for your help.
3.45 Pm,UK
Got it.
Surprising how clean it is,glue wise.
I'll scrape it all down good now.The blackening is where most of the liquid started.It shouldnt take too long to dry.
Excellent. Make sure you wash away all the vinegar as it may hamper future glueing. As you say, when dry scrape both neck & FB. Both should be flat or a wee bit hollow, so that the edges have good contact, but that will come later. Be careful not to damage the edges.
For alignment, suggest to use a suitably thin wire over the centre, running from one of the tuning pegs all the way over the bridge & saddle to the end pin. Make 2 small wooden blocks, temporarily glued onto the neck (with something like a thin hide glue, or Pritt). The top one comes where the top nut was, and gets the same height above the neck as where a string would be, if it were running in the middle, so the thickness of the FB on that end + a bit (say 0.2mm). That top one can have a suitable groove in the middle.
The second one comes at (or near) the end of the neck. It should have a height equal to the thickness of the FB (at that location) + how high you would want your strings to be there, above the FB (say FB thickness + 6mm).
On your bridge mark the mid-point on the crest (pencil), and do same on the saddle (on a bit of masking tape). So the idea is to run a wire right over the centre, and you can read the alignment on the lower block, both in terms of left-right (the wire should be over the mark you made for the centre), as well as in terms of height (the wire should just about touch that lower block).
All this is best done with the bass lying on its back, with back & pegbox propped suitably on cushions or so to get the right position. Position the bridge carefully at the proper place, and maybe use some masking tape to make sure it stays there.
You could possibly do the repair with a single lag bolt, but I would prefer 2 or 3 smaller ones. Suggest to start with a single (central) bolt / screw to do the glue job, nearer the end of the neck. Then, once the glue has set, install 2 further reinforcements running at a slight angle just below the surface of the upper side of the heel. Those should take the string tension, and because they are separated spatially they will also give some lateral strength.
Remember this wood is quite hard, but it will split if the hole is too small for a screw, or has insufficient clearance for glue to escape (you can glue-in the 2 later ones). And also be careful not to snap off screws.
I suggest using a slow epoxy like Araldite Standard, but maybe there are better ones available locally. That should give you a few hours to position the neck, but thereafter it's done. You should have a very small gap (ideally hardly visible), as it should largely go back exactly the way it was before it broke. Test-fit before you glue, re-work as required, and use masking tape to prevent the glue to go where it shouldn't.
Good luck!
For alignment, suggest to use a suitably thin wire over the centre, running from one of the tuning pegs all the way over the bridge & saddle to the end pin. Make 2 small wooden blocks, temporarily glued onto the neck (with something like a thin hide glue, or Pritt). The top one comes where the top nut was, and gets the same height above the neck as where a string would be, if it were running in the middle, so the thickness of the FB on that end + a bit (say 0.2mm). That top one can have a suitable groove in the middle.
The second one comes at (or near) the end of the neck. It should have a height equal to the thickness of the FB (at that location) + how high you would want your strings to be there, above the FB (say FB thickness + 6mm).
On your bridge mark the mid-point on the crest (pencil), and do same on the saddle (on a bit of masking tape). So the idea is to run a wire right over the centre, and you can read the alignment on the lower block, both in terms of left-right (the wire should be over the mark you made for the centre), as well as in terms of height (the wire should just about touch that lower block).
All this is best done with the bass lying on its back, with back & pegbox propped suitably on cushions or so to get the right position. Position the bridge carefully at the proper place, and maybe use some masking tape to make sure it stays there.
You could possibly do the repair with a single lag bolt, but I would prefer 2 or 3 smaller ones. Suggest to start with a single (central) bolt / screw to do the glue job, nearer the end of the neck. Then, once the glue has set, install 2 further reinforcements running at a slight angle just below the surface of the upper side of the heel. Those should take the string tension, and because they are separated spatially they will also give some lateral strength.
Remember this wood is quite hard, but it will split if the hole is too small for a screw, or has insufficient clearance for glue to escape (you can glue-in the 2 later ones). And also be careful not to snap off screws.
I suggest using a slow epoxy like Araldite Standard, but maybe there are better ones available locally. That should give you a few hours to position the neck, but thereafter it's done. You should have a very small gap (ideally hardly visible), as it should largely go back exactly the way it was before it broke. Test-fit before you glue, re-work as required, and use masking tape to prevent the glue to go where it shouldn't.
Good luck!
araldite standard | eBay
So many!
What is best here Ortsom?
So this will be for the neck and the FB yes
I will try visualising your method for a while I think,so bear with me while I figure out what I'm doing,ok
No, don't epoxy the FB. It's not that it won't hold, but you'll never get it off in a normal way. FB's are a wearing item, and after planing / scraping them a few times they become too thin & are replaced. At least, that's what happens with higher quality instruments, the walk of life in this class may be different. Hide glue =HHG is advised for the FB, as it actually is for all standard joints. But before that, make very sure all the old PVA is gone. One of the other problems of PVA is that nothing sticks to it well, not even new PVA.
Many adverts, but all the 'Araldite Standard' ones is the same stuff. The 2x15ml tubes are more economical than the 24ml (=2x12ml) syringe. It is what I used in Putting the head back on. It's the other end of the neck, but have a look through the entire thread; T88 is also used apparently, but I don't know that one.
I have only reconstructed a heel once, a long time ago. That was in the early '80s, and I used impregnating resin (rather than glue), that I had left-over from my surfboard building days. It was reinforced as I outline above, and I used long sections of thread rather than screws, that were epoxied in place. Cannot remember if it was M5 or M6. Has been under tension ever since & is still fine.
In lutherie there is a strong reluctance against procedures & methods that cannot be undone, but as far as I'm concerned: if it pertains to something that should never be undone (like a heel, that should ideally always remain one un-changing unit), it's fine to make it permanent. But things like a FB, top, back, .. should indeed be reversible, and particularly in high value instruments with a long life expectancy.
Yes, please visualise the proposal, check details & get it clear in your head. It's the imaginary dry lap that racers do before the race, and surgeons do before they start the operation.
If the broken wood profiles of the 2 parts still fit well, that helps, because that will then guide you on proper placement, but it's best to make sure you glue it properly, and not under a wrong angle. There's no easy come-back from that.
Also make sure the wood is properly dry before you glue in pieces of steel: wood shrinks when it dries, steel does not.
Many adverts, but all the 'Araldite Standard' ones is the same stuff. The 2x15ml tubes are more economical than the 24ml (=2x12ml) syringe. It is what I used in Putting the head back on. It's the other end of the neck, but have a look through the entire thread; T88 is also used apparently, but I don't know that one.
I have only reconstructed a heel once, a long time ago. That was in the early '80s, and I used impregnating resin (rather than glue), that I had left-over from my surfboard building days. It was reinforced as I outline above, and I used long sections of thread rather than screws, that were epoxied in place. Cannot remember if it was M5 or M6. Has been under tension ever since & is still fine.
In lutherie there is a strong reluctance against procedures & methods that cannot be undone, but as far as I'm concerned: if it pertains to something that should never be undone (like a heel, that should ideally always remain one un-changing unit), it's fine to make it permanent. But things like a FB, top, back, .. should indeed be reversible, and particularly in high value instruments with a long life expectancy.
Yes, please visualise the proposal, check details & get it clear in your head. It's the imaginary dry lap that racers do before the race, and surgeons do before they start the operation.
If the broken wood profiles of the 2 parts still fit well, that helps, because that will then guide you on proper placement, but it's best to make sure you glue it properly, and not under a wrong angle. There's no easy come-back from that.
Also make sure the wood is properly dry before you glue in pieces of steel: wood shrinks when it dries, steel does not.
I will get this for the Fingerboard:Titebond Liquid Hide Glue 118ml 4oz 600224 Suitable for Wood and Cloth Glue
It has the word 'cracking' in it's descritor.
It is a fine word as it really does 'crack' doesn't it?!
I am enthused by your knowledge and yes,some operations are best done with 'reversability' in mind,especially with instruments.
I'm thinking knuts and saddles,and of course Fret/Finger boards.
Here are the two joints cleaned out:
Q: [Probably a silly one}
You see on the right hand side of the heel the side piece is still in place and is fairly solid.Shall I remove this as well tho,and re glue it with Araldite,that would be ideal wouldnt it?
It has the word 'cracking' in it's descritor.
It is a fine word as it really does 'crack' doesn't it?!
I am enthused by your knowledge and yes,some operations are best done with 'reversability' in mind,especially with instruments.
I'm thinking knuts and saddles,and of course Fret/Finger boards.
Here are the two joints cleaned out:
Q: [Probably a silly one}
You see on the right hand side of the heel the side piece is still in place and is fairly solid.Shall I remove this as well tho,and re glue it with Araldite,that would be ideal wouldnt it?
Don't do the titebond! It never cures. Not for instruments. Found this out the hard way trying to repair a friend's bass (he bought this glue when I told him I'd fix his bass if he bought the hide glue). Get the granulated.
Oh right.Have to cancel it then.
How much of it do I need typically?
I'm not good at maths.
This should do? Natural Hide Pearl Glue for luthiers antique repair & veneering - 200 450 900 gm 200g?
EAME, the pearls should do fine for the FB. 200g = enough for some time to come. Search on how to use it, there should be plenty info on the internet (if the seller doesn't include a leaflet). Make what you need & keep the rest dry.
On the pin stripe of white polymer: that looks like the edge of a wedge of wood, and if so, that wedge is best lifted & cleaned of polymer. The most important thing is that the parts fit well to each other, and I fear the layer of polymer between the wedge & the heel is too thick, preventing the rest of the neck to fit properly onto the heel. Then you'll get a weaker joint & your neck will be at an angle.
If you take the wedge out & clean it, you'll have 3 parts (heel, neck & wedge), but with the rugosity of the wood you can probably glue them in one go. Try in your test run & feel how the wedge sits after you tighten the assembly screw (somewhere near the low side of the centre of the heel). But you might need a small clamp.
On the pin stripe of white polymer: that looks like the edge of a wedge of wood, and if so, that wedge is best lifted & cleaned of polymer. The most important thing is that the parts fit well to each other, and I fear the layer of polymer between the wedge & the heel is too thick, preventing the rest of the neck to fit properly onto the heel. Then you'll get a weaker joint & your neck will be at an angle.
If you take the wedge out & clean it, you'll have 3 parts (heel, neck & wedge), but with the rugosity of the wood you can probably glue them in one go. Try in your test run & feel how the wedge sits after you tighten the assembly screw (somewhere near the low side of the centre of the heel). But you might need a small clamp.
Here I am
waiting for the glues to arrive,and running this by you:A: 3 Lag screws,all drilled out to correct shank and srew diameters,either countersunk into the neck or clearance in the bottom of the Fingerboard.
B:See how the wedges sit with the central screw test
C: Possibly glue and clamp the two wedges in first
D:Glue ,screw and get angles sorted with the Bridge in place in the time span before it sets.
How does that sound?
The Heel is 6.5'' long
With a shank clearance of 1 3/4'',I'm thinking the main central screw = 3.5''
and the side ones making them about 2.5'' in length
Q: Would you go any deeper with the central screw [or both] or should the outer ones be the deepest?
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A): best countersunk into the neck. If steel sticks out above the neck it will be more difficult to remove the FB in future. You (or someone else) may break your knife.
I suggest something like this:
The star-shaped one is the screw used for glueing, and the 2 round ones should come later, when the glue is set; those are the reinforcements. To minimise sliding during gluing, the first one should be drilled largely perpendicular to the break, yet a little bit towards the mortise (so downwards in the above pic). The break is a short bit into the mortice, the slight angle should pull the neck into the mortice/top & help aligning the neck.
B): I can see one wedge, not the other, and I can't see how the wedges are shaped. The epoxy acts initially as a lubricant, and if you press the parts together with the central screw, the wedges might be pushed out. Feel for that during a test assembly. If they want to come sideways, you can prevent that with a clamp, but you cannot clamp downwards (in the direction of the end pin). If they want to come that way, you may have to glue them in firsts. But the idea is to put it back together as close as possible to what it was before the break, now with as thin as possible a layer of glue between the parts.
Btw, before setting epoxy dissolves in acetone.
C): Yes, if necessary.
D): Yes. Now that you have hide glue, make a little bit much thinned down (just a drop or 2), use that for placing those blocks, obviously put in place first, or during the test assembly. Don't clamp, just push in place & hold for a second. When done you can knock them off easily. The trick with the blocks & the wire is just to make sure you glue the lot in place aligned properly. That's why you use only a single screw then, that should give some flexibility / room to move the scroll. So it needs to be supported at the right place during the setting of the glue.
Note that there is no rush, you have 80 minutes to get it right. Aligned properly & minimal gap.
Q: The 2 top ones will take all the string tension. When the lot is assembled, the central one won't get any load, at least not if you don't drop the bass.
You want length to cover over more wood, and maximise shear strength, but if screws get longer, they either get thicker (costing you more wood surface, which you don't want because that weakens the heel & neck), or you run the risk of twisting them off (about the last thing you want here). Though the central one needs to be a screw, as it needs to tighten the lot together, you can consider using a piece of thread for the top 2 (say M5 or M6, cut indeed to 3.5"). You would then glue those in place: fill the hole you drill as good & deep as you can w/ epoxy (using a sateh skewer or so), and fill the thread with epoxy along the entire length, and push in place slowly alowing the air to escape.
Indeed 3 1/2" as you don't need to go deeper below the break than you are above the break. So 2x 1.75". I would suggest a 2.5" central screw for assembly, and the upper ones 3.5" pieces of thread.
I suggest something like this:
The star-shaped one is the screw used for glueing, and the 2 round ones should come later, when the glue is set; those are the reinforcements. To minimise sliding during gluing, the first one should be drilled largely perpendicular to the break, yet a little bit towards the mortise (so downwards in the above pic). The break is a short bit into the mortice, the slight angle should pull the neck into the mortice/top & help aligning the neck.
B): I can see one wedge, not the other, and I can't see how the wedges are shaped. The epoxy acts initially as a lubricant, and if you press the parts together with the central screw, the wedges might be pushed out. Feel for that during a test assembly. If they want to come sideways, you can prevent that with a clamp, but you cannot clamp downwards (in the direction of the end pin). If they want to come that way, you may have to glue them in firsts. But the idea is to put it back together as close as possible to what it was before the break, now with as thin as possible a layer of glue between the parts.
Btw, before setting epoxy dissolves in acetone.
C): Yes, if necessary.
D): Yes. Now that you have hide glue, make a little bit much thinned down (just a drop or 2), use that for placing those blocks, obviously put in place first, or during the test assembly. Don't clamp, just push in place & hold for a second. When done you can knock them off easily. The trick with the blocks & the wire is just to make sure you glue the lot in place aligned properly. That's why you use only a single screw then, that should give some flexibility / room to move the scroll. So it needs to be supported at the right place during the setting of the glue.
Note that there is no rush, you have 80 minutes to get it right. Aligned properly & minimal gap.
Q: The 2 top ones will take all the string tension. When the lot is assembled, the central one won't get any load, at least not if you don't drop the bass.
You want length to cover over more wood, and maximise shear strength, but if screws get longer, they either get thicker (costing you more wood surface, which you don't want because that weakens the heel & neck), or you run the risk of twisting them off (about the last thing you want here). Though the central one needs to be a screw, as it needs to tighten the lot together, you can consider using a piece of thread for the top 2 (say M5 or M6, cut indeed to 3.5"). You would then glue those in place: fill the hole you drill as good & deep as you can w/ epoxy (using a sateh skewer or so), and fill the thread with epoxy along the entire length, and push in place slowly alowing the air to escape.
Indeed 3 1/2" as you don't need to go deeper below the break than you are above the break. So 2x 1.75". I would suggest a 2.5" central screw for assembly, and the upper ones 3.5" pieces of thread.
These are the chips and in place :
but rather than glueing them on the Heel [there are slight gaps] they fit better on the neck,and much easier to clamp/apply pressure and there are no gaps this way.
I've never used thread,but saw a couple of rods of it today.
I'm not putting inserts in am I?
Just putting threaded bar end into the predrilled hole, holding the bar in the drill jaws and threading it in?
Thats what you mean?
Also,I'm using the Araldite there,the Hide glue is for the Fingerboard,as was advised earlier?
Yes of course,good point about countersinking into the neck..
Just bought M5 threaded rod 500mm.
Waiting for this and the glues .
Just need to find a suitable Lag screw now.
Is this what I need please?
[M5 not long enough]
but rather than glueing them on the Heel [there are slight gaps] they fit better on the neck,and much easier to clamp/apply pressure and there are no gaps this way.I've never used thread,but saw a couple of rods of it today.
I'm not putting inserts in am I?
Just putting threaded bar end into the predrilled hole, holding the bar in the drill jaws and threading it in?
Thats what you mean?
Also,I'm using the Araldite there,the Hide glue is for the Fingerboard,as was advised earlier?
Yes of course,good point about countersinking into the neck..
Just bought M5 threaded rod 500mm.
Waiting for this and the glues .
Just need to find a suitable Lag screw now.
Is this what I need please?
[M5 not long enough]
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Good day!
Chips: well, on the neck it is then. Wipe off any glue squeezed out before it sets, as that will impede the later fit onto the heel. And don't press so hard that you damage the grain on the top, that should fit into the heel part later.
Inserts: I wouldn't use those. Not clear where they would go, and I'd like to keep as much wood as possible.
On M5 & M6 etc: yes, I was referring to metric screw thread as discussed in Invalid Link Removed. You might use an imperial 3/16" or 1/4" threaded rod, but I believe the UK has also gone largely metric in shops like B&Q, but maybe I'm wrong. I have no clue why that eBay seller calls the lag bolts pictured 'M5 M6 ...', as far as I know they aren't.
You need a wood-thread like that for the assembly screw, to pull the neck onto the heel. But I'm not sure a thread like that is very strong in this kind of wood, I fear that on load it may be splitting the wood & be pulled-out rather easily (if you're not splitting the wood when you screw them in...). That's why I suggested a shorter (2.5") assembly screw.
The threaded rods / studs would not rely on steel-to-wood contact, or pressure on the wood. They are purely glued in, and that's why you need a strong epoxy (which adheres to both wood and steel; hide glue does not stick to steel). The thread just helps to give more grip on the steel part, and you would need some clearance between the hole & the rod for the excess glue to escape. I fear that if you drill a 5mm (or 4.8mm) hole, work epoxy in there, and then come with a M5 rod in a drill & screw that in at full blast, you will split the heel. You need some clearance, and push the rod in slowly but continuously. The hole is slightly deeper than the length of the rod, so nothing sticks out. The rod needs to go in by hand (without glue) quite easily as this epoxy is quite viscous. Test how it goes in, but don't drop it in. If too tight, sand-off the edges of the rod a bit.
Btw: if you push the rod in, the surplus epoxy comes out, and you do not want that to contaminate the surface where you'll glue the FB later, with hide glue. Epoxy will impregnate the wood & make it impermeable, so that hide glue won't stick there. Before you start with the epoxy there, mask-off the neck's surface with masking tape, preventing that to happen.
Btw2: you'll need a longer drill for these holes; standard drill bits are too short. Well, unless you go up in diameter, but then you drill away more wood & make Swiss cheese.
Back to the assembly screw: make sure the hole in the neck is bigger than in the heel: the screw needs to pull the neck onto the heel, and the neck may need some freedom to move in the proper position. You can drill a hole in the neck part first, and then you'll need to position the neck properly onto the heel & drill through that hole with the same drill bit. Then take the neck off & re-drill that hole a bit bigger, & counter-sink.
On the lag bolt / assembly screw: I don't know. Just something 2.5" tall & say 5mm-6mm-3/16"-1/4" OD. Maybe go to a hardware store.
PS.: I am not a luthier, and none of this is lutherie. It is just an, in my mind, pragmatic & cost-effective way to bring your low-cost instrument back to life & use. Luthiers do not do screws & lag bolts, and epoxy is traditionally frowned upon (though I understand it is nowadays used by some, for some applications). Here I recommended epoxy because of prior contamination with the polymer.
Chips: well, on the neck it is then. Wipe off any glue squeezed out before it sets, as that will impede the later fit onto the heel. And don't press so hard that you damage the grain on the top, that should fit into the heel part later.
Inserts: I wouldn't use those. Not clear where they would go, and I'd like to keep as much wood as possible.
On M5 & M6 etc: yes, I was referring to metric screw thread as discussed in Invalid Link Removed. You might use an imperial 3/16" or 1/4" threaded rod, but I believe the UK has also gone largely metric in shops like B&Q, but maybe I'm wrong. I have no clue why that eBay seller calls the lag bolts pictured 'M5 M6 ...', as far as I know they aren't.
You need a wood-thread like that for the assembly screw, to pull the neck onto the heel. But I'm not sure a thread like that is very strong in this kind of wood, I fear that on load it may be splitting the wood & be pulled-out rather easily (if you're not splitting the wood when you screw them in...). That's why I suggested a shorter (2.5") assembly screw.
The threaded rods / studs would not rely on steel-to-wood contact, or pressure on the wood. They are purely glued in, and that's why you need a strong epoxy (which adheres to both wood and steel; hide glue does not stick to steel). The thread just helps to give more grip on the steel part, and you would need some clearance between the hole & the rod for the excess glue to escape. I fear that if you drill a 5mm (or 4.8mm) hole, work epoxy in there, and then come with a M5 rod in a drill & screw that in at full blast, you will split the heel. You need some clearance, and push the rod in slowly but continuously. The hole is slightly deeper than the length of the rod, so nothing sticks out. The rod needs to go in by hand (without glue) quite easily as this epoxy is quite viscous. Test how it goes in, but don't drop it in. If too tight, sand-off the edges of the rod a bit.
Btw: if you push the rod in, the surplus epoxy comes out, and you do not want that to contaminate the surface where you'll glue the FB later, with hide glue. Epoxy will impregnate the wood & make it impermeable, so that hide glue won't stick there. Before you start with the epoxy there, mask-off the neck's surface with masking tape, preventing that to happen.
Btw2: you'll need a longer drill for these holes; standard drill bits are too short. Well, unless you go up in diameter, but then you drill away more wood & make Swiss cheese.
Back to the assembly screw: make sure the hole in the neck is bigger than in the heel: the screw needs to pull the neck onto the heel, and the neck may need some freedom to move in the proper position. You can drill a hole in the neck part first, and then you'll need to position the neck properly onto the heel & drill through that hole with the same drill bit. Then take the neck off & re-drill that hole a bit bigger, & counter-sink.
On the lag bolt / assembly screw: I don't know. Just something 2.5" tall & say 5mm-6mm-3/16"-1/4" OD. Maybe go to a hardware store.
PS.: I am not a luthier, and none of this is lutherie. It is just an, in my mind, pragmatic & cost-effective way to bring your low-cost instrument back to life & use. Luthiers do not do screws & lag bolts, and epoxy is traditionally frowned upon (though I understand it is nowadays used by some, for some applications). Here I recommended epoxy because of prior contamination with the polymer.
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I think the 'M5/6 is the mm 5mm 6mm?
It looks like that is what other dealers on ebay are saying it means.Have I missed something here?
Woww,hold on friend,do you seriously think I'd be doing this thing 'full blast' as you call it?!!
I know we dont really know each other,but give me a bit of credit [I know I ballsed it up first go] but I do kind of understand grain in wood and the need to do some careful drilling to try and avoid splitting the wood prior to inserting steel in there...I'm talking about a vari-speed drill ,hhh!
Please stop using the term 'I fear' !!!.We dont,do we?
We are the courageous fixer's of broken things,the fearless wielder's of blunt instuments!....[And that's just the Bloody Bass!!]
hhh.
Got to laff really,ain't we?!
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On M5, M6, ...:
If you look in the reference linked above, you read "A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter". The capital 'M' is for Metric here, not 'mm'. M5 = 5mm OD x 0.8mm pitch, M6 = 6mm OD x 1.0mm pitch. If you go to a hardware store, manned by someone who knows his stuff, and you ask for M8 he should not try to sell you something with a thread made for wood. You should get 8x1.25, with a thread profile as described in the link.
On the 'full blast': good to hear you have feeling for these things. And I was pleasantly surprised how well you got the FB off. But if you screw M5 into a hole Ø4.8mm, with epoxy in it, even by hand (saw a slit in the top & use a screwdriver) you risk splitting the heel, because of the pressure in the viscous epoxy below. With these metric threads (designed for metal), and with holes this deep, you need clearance for the excess epoxy to escape up & out; with a much coarser wood thread maybe you'd get away with it. And in that sense M6 is better than M5 (M6 might be better anyway, M5 is tiny).
Be careful wielding those blunt instruments, or the bass might indeed get bloody...
I fear you have. Which is me politely saying: yes sir, you have. I do not really fear it, nor am I afraid of it, nor am I losing any sleep over it.
If you look in the reference linked above, you read "A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter". The capital 'M' is for Metric here, not 'mm'. M5 = 5mm OD x 0.8mm pitch, M6 = 6mm OD x 1.0mm pitch. If you go to a hardware store, manned by someone who knows his stuff, and you ask for M8 he should not try to sell you something with a thread made for wood. You should get 8x1.25, with a thread profile as described in the link.
On the 'full blast': good to hear you have feeling for these things. And I was pleasantly surprised how well you got the FB off. But if you screw M5 into a hole Ø4.8mm, with epoxy in it, even by hand (saw a slit in the top & use a screwdriver) you risk splitting the heel, because of the pressure in the viscous epoxy below. With these metric threads (designed for metal), and with holes this deep, you need clearance for the excess epoxy to escape up & out; with a much coarser wood thread maybe you'd get away with it. And in that sense M6 is better than M5 (M6 might be better anyway, M5 is tiny).
Be careful wielding those blunt instruments, or the bass might indeed get bloody...
Gotta give ya props Ortsom for the level of technical specificity you've been offering. Very interesting thread. Can't wait to see the bass back in playable shape, EAME.
