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[Steve_freereeder]

One thing I still don't entirely understand is how there isn't a huge air leak from the hole made for the rod. I know there's a rod going through the hole, but everywhere else in the box there are countless gaskets etc. and here they're suddenly not required.

There will be a slight air leak around the stop shaft, but it is barely noticeable even under high bellows pressure. Air leakage is proportional to the cross-sectional area of any gap. The cross-sectional area of the annulus between the shaft and the wooden block and end frames is really very small indeed. Contrast this with the potentially large cross-sectional area around the bellows frame if the bellows gasket were to be missing or removed.

Here's a rather crude set of calculations but the general point can be made.

1.
Stop shaft dia (say) 2 mm.
Cross-sectional area  ∏r² = 3.142 x 1 x 1 = 3.142 mm²
Diameter of hole for stop shaft (say) 2.2 mm.
Cross-sectional area  ∏r² = 3.142 x 1.1 x 1.1 = 3.802 mm²
Therefore cross-sectional area of annulus is 3.802 - 3.142 = 0.6598 mm² (A)

2.
Now consider the bellows frames with dimensions, say of a Hohner Pokerwork, approx. 150 mm x 280 mm
Total perimeter of bellows frame (both ends) is (150 mm + 280 mm) x 2 x 2 = 1720 mm
Assuming the same gap as previously, if the gasket were to be missing: 0.2 mm (probably a conservative estimate).
Therefore the cross-sectional area of the gap of the bellows frames with no gaskets is 1720 x 0.2 = 344 mm² (B)

3.
Conclusion
The air leakage around the stop shaft is very much less than the potential leakage around the bellows frames with no gaskets:
0.6598 ÷ 344 = 0.001918 (approx 0.2 %)

Which also demonstrates why a faulty or worn bellows gasket can have such a deleterious impact on the air tightness of a melodeon.

[Stiamh]

It is Stiamh!

Just by way of explanation, Theo is contradicting an erroneous statement I made and deleted after about 20 seconds (having thought about the matter a little) - evidently not quickly enough to escape notice! Thanks, Theo.

[Eshed]

Thanks Theo & Steve, this makes a lot of sense!

[Lester]

In addition, when the stop is right down the stop 'button' covers the annulus and when the stop is right up the internal block covers the annuls thus reducing even further the potential loss of air.


Posh boxes with stops usually have a small leather washer on the bottom of the stop 'button'.

[rees]

Easily sorted - make two little leather washers to fit on the stop rod, inside and outside, Castagnari style.

[Gena Crisman]

The stop rod I have has very subtle ridges down its length, and when running it through the hole, it makes a cute little vvzzzzsht noise from how close a fit it is. Test fitting it in advance gave me a lot of confidence that I wasn't going to squeeze the bellows and have it shoot out or anything, but it was hard to believe before I saw it. Gives me an idea, actually, maybe I should try and document that somehow, since it would have helped me.

Anyway, Eshed, McGrooger, Stiamh, and especially Winston! I'm very glad to hear that people have appreciated the tale. I still have another stop to add, so, I'm more than willing to take on board feedback or take a picture of something that I did. I mean, on show mostly are just the ideas I had to solve my particular problems, so, hopefully people will let me know if I'm doing anything egregious. I've wanted a thirds stop for quite some time!

PM your address and I can send you all sorts of hardwood offcuts.

If my plan A doesn't work out, I shall do just that, thank you for the kind offer!

[Theo]

I have a suggestion about drilling that hole.  I would find it easier to use a power drill.  Ideally on a floor standing pillar drill,  or failing that with a hand held power drill with a nice controllable low speed.  Maybe this is what you did, but I understood that you had used a hand powered drill. 
Also on the drilling I think you will find it easier to drill a pilot hole, and then go straight to the finish size drill.  Even better would be to finish with a drill that is .1 smaller that the stop shaft. That way you get a very snug fit.

[Chris Rayner]

There are several versions of this https://www.amazon.co.uk/dp/B0001P19PO/ref=asc_df_B0001P19PO56252480/?tag=googshopuk-21&creative=22110&creativeASIN=B0001P19PO&linkCode=df0&hvadid=223168629794&hvpos=1o3&hvnetw=g&hvrand=14489010104604052102&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9045831&hvtargid=pla-421516047083&th=1&psc=1

Which is a substantial improvement on a hand held drill, and a good deal cheaper than a pillar drill.

[Rog]

There are several versions of this https://www.amazon.co.uk/dp/B0001P19PO/ref=asc_df_B0001P19PO56252480/?tag=googshopuk-21&creative=22110&creativeASIN=B0001P19PO&linkCode=df0&hvadid=223168629794&hvpos=1o3&hvnetw=g&hvrand=14489010104604052102&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9045831&hvtargid=pla-421516047083&th=1&psc=1

Which is a substantial improvement on a hand held drill, and a good deal cheaper than a pillar drill.

I have one of those and they are for drilling holes in a wall or centred on a pipe. Not much use for drilling precision holes where you want them. I also have one of these which is quite a good (cheap) substitute for a pillar drill, if you have a mains drill, esp for light occasional use... I was unimpressed by it initially, but having used it a good few times find it perfectly adequate...though your drill needs a variable speed control and obviously a way to lock the power on.
https://www.powertoolsdirect.com/clarke-cds1-drill-stand?gclid=Cj0KCQjw9ZDeBRD9ARIsAMbAmoaNdIOeTCTxaPOznKJjt17GSRpGjQwcV95aaPPDMunSR92nXQ2BUxgaAvhxEALw_wcB

[Winston Smith]

I'd have a go at this, if I could fit it into my cupboard!

www.ebay.co.uk/itm/pillar-drill-Meddings-Single-phase/192690984744

[Gena Crisman]

I have a suggestion about drilling that hole.

I'm not sure, honestly, I quite like a good hand drill. Well, more like Pin Vise, I guess - you can see if in several of the photos - in case anyone is uncertain, I'm certainly not using one of those hand cranky type things. I feel I have more control with it and can do things at a snail's pace, so can usually fix any problems (such as the hole drifting) before they're 'done' so to speak, and there's only ever as many rotations of the bit in the hole as I want . If this is in reference to the alignment, idk, I think in this case I failed to accurately clamp the wood block and it was in a slightly different place than it should have been. which I can believe because the plastic can be really very flexible, and then splitting and the final process of getting it up to size didn't help.

Going electric and having fewer jumps from pilot to final size to cut down drift - that's definitely something I'll consider when I come to replace the block with a better piece of wood. Should I worry about the grain direction particularly? Also I guess I'll have to figure out how to scour off the existing block without destroying the very thin plastic underneath. If I can manage that, I may cut the block slightly oversize, drill the hole, and slowly adjust the sides down until its perfect, and only then secure it to the slide.

I also think I'm going to release myself from my no power tools on the melodeon rule when it comes to removing the other part of the block mounting wood. That, and buy a proper chisel.

[Steve_freereeder]

... when I come to replace the block with a better piece of wood. Should I worry about the grain direction particularly? Also I guess I'll have to figure out how to scour off the existing block without destroying the very thin plastic underneath.

Since the main forces, up and down, are going to be perpendicular to the stop shaft axis, you want the strongest wood direction, which is along the length of the grain, to also be aligned along the stop shaft axis. Therefore I would recommend drilling and screwing into the end grain of the wood block. If you are using a hard wood such as beech, drill a pilot hole fractionally undersize first and then ease the stop shaft into it a bit at a time and then backing off and clearing the swarf/dust so that the shaft gradually cuts its own thread.

If at any future time, the stop shaft should become loose in the wood block, an effective remedy is to put a couple of drops of superglue into the hole, using a cocktail stick to quickly smear it round the inside of the hole. Then re-screw in the stop shaft before the glue has completely set. The glue will form a firm coating inside the hole into which the stop shaft will re-cut a thread, but will still allow the shaft to be unscrewed as needed.

(This works for loose bellows pins too!)

If you are concerned about removing the remains of the old block from the plastic slider cleanly, do you not have sufficient plastic sheet left so that you could make a new slider?

[Squeaky Pete]

If you are using a hand held power drill and the main worry is drilling at an angle, stick an old CD flat on the surface and the reflection will keep you straight. There's even a hole in the middle to drill through. A bit of blue tack will hold it in position if necessary.

[Theo]

Steve has given the scientists answer.  The practical woodworker would know that wood splits most easily along the grain and that drilling a hole into end grain and inserting a tight fitting screw has a wedging effect which will tend to split the wood along the grain.  The strongest direction for holding a screw is at right angles to the growth rings.

[Steve_freereeder]

Yes - I know that. But it depends on the wood you are using, carefully drilling the pilot hole of the correct diameter, and being gentle with the initial threading of the stop shaft into the hole. Beech should be OK.

But if you are concerned about splitting then perhaps you should drill and screw transversely into the grain. I guess in this particular usage, the screw thread and the fact that the wood block is glued to the slider will help reinforce the block against subsequent splitting due to repeated movement.

[Lester]

Probably the most used and most useful piece of advice I took away from Emmanuel Pariselle's melodeon building courses I attended was to wax the threads of screws in cases like this. Just some ordinary candle wax will help the screw cut its thread without causing other problems.

[Winston Smith]

I was given similar advice 50 odd years ago by an old woodworker, only he recommended soap. Although, in that instance, it was to ensure that the screws came out easily after being in situ for many years.

[rees]

Every screw in my hand built one-rows is waxed. I use Russian tallow, not Vegan friendly as it's made from melted cows, but it does the job.

[Theo]

Screwing into end grain also gives the poorest grip.

[rees]

Screwing into end grain also gives the poorest grip.

Yup!