Member postings for Kiwi Bloke

Thank you Adam and John for your offers of help - much appreciated. I think I need to be self-sufficient, however, in case I need more, sporadically, in the future.

The Westfield site is most interesting (I hadn't found it), particularly the warning that nominal and actual sizes may be quite different. Perhaps that goes some way to answer Jason's points. However I'm not convinced that the Italians in the 1950-60s would have used woodscrews conforming to the gauge number 'standard', and the sizes used in this box seem to bear that out. For all I know, there was a little factory somewhere, churning out 'funnies' for the accordion industry. That industry is interesting: it seems that there were numerous factories (if you can call them that), in two small towns that were, in effect, the accordion manufactory of Italy. Many firms were clearly started by members of the same family. Who made what, or bought in what, and from whom would be virtually impossible to discover. A few videos can be found of the things being made today - mostly hand-work, with little sophistication visible in some firms. The engineering is crude, the material selection questionable, but craftsmen and women triumph over the limitations of their work practice to achieve something beautiful, magical and of considerable complexity.

Hah! Fortunately, no desmodromic valves or Marelli electrics in an accordion! My example is perhaps the Lancia of instruments - it's corroded as hell. Debatable whether a Ducati or an accordion makes the better sound...

Thanks guys for the suggestions, but no joy with the sizes I need. I suppose screw manufacture mostly went East, and that was the end of the 'funny' sizes. Anyway, if anyone can help any more, please do!

Let's wait for one of the Aussie members to send a pic of a workshop python, or a North American send a pic of a bear or wolf. All I've got here in NZ is workshop mice and rats, although considerably fewer, after more aggressive control measures.

Can anyone suggest a supplier (who might send to NZ) of very small woodscrews? I'm particularly looking for 1.7mm nominal dia., in lengths around 8mm, but also some other small sizes. Just to make it even more difficult, most have to have slotted round heads, and preferably be plated. These are to restore an elderly Italian accordion, whose engineering leaves a lot to be desired... I think the original screws were made to metric conventions (don't think 'standards' really applied) because these don't conform to the 'gauge' standard.

I've tried the major accordion spares suppliers' web sites without success. I'm trying to do this 'properly', so sheet metal screws / self-tappers just wouldn't be right. Fall-back option is to make them, but I'm lazy.

+1 for another layer of MDF, or, perhaps hardboard, but, as has been said, it all depends...

Rather than glue a layer of MDF down, you could consider future-proofing it by making the top layer removable. Screw thread inserts into the existing top and use brass or nylon countersunk screws to hold the new top layer. Little risk of damage to cutting tools, should they be driven into the fixings. The surface can be made harder and waterproof with several thinned coats of varnish, rubbing the coats in, until the MDF won't accept any more. Or epoxy, if you're rich...

Thanks everyone for the thoughts and advice - keep 'em coming!

This is one of those jobs that gets worse, the more you think about it. I may now be at the stage of over-thinking, but better safe than sorry. Unfortunately, I'm stuck with a countersunk screw head, which can't be of larger diameter than a M2 csk head. The M2 female threads are gone, so some sort of insert is needed. The thread will be 2mm max in length, so 5 threads engaged max for M2. M3 would be 4 threads, but the csk head is deeper, and it sits in 1mm thick plate, so engagement would be less. Also, the Italian who made the thing fettled the threaded holes with quite deep countersinking, so the original threads were a skin-of-the-teeth variety. A self-tapper into a plastic insert is attractive, but there's the risk of dissimilar metal corrosion at the head end. Thus, I feel the safest option is a plastic M2 csk screw. In NZ, Helicoil or Recoil kits seem amusingly to cost (in real terms) about double the UK price, so, even though irritating to make, plastic inserts have a huge cost advantage.

I'm aware that Zn-plated , Cd-plated, and stainless fasteners are used a lot in alloy threads, often without any precautionary addition of a chromate treatment, such as Duralac (of which I've had a tube for years, for similar awkward applications). Also, Helicoil-type inserts are used a lot, but I believe these should ideally not be the standard, non-coated type. Perehaps, as suggested, a good dose of Duralac would be OK.

Murphy's law will operate. If I were to take no precautions, and use brass screws in alloy threads, as originally manufactured, there will never again be any corrosion. But, if I'm aware of this, and take the chance, all hell will break loose. Sometimes it's best to accept that you just can't win, and try to design yourself out of the problem...

I have a Superior surface grinder, which is very similar, and doesn't contain such 'wires'. I'm sure Tony Ray is correct.

20 years ago, when I was in UK, there were a few bellows suppliers, with a wide range of off-the-shelf sizes and shapes. Some were prepared to make 'specials'. I expect the price would be alarming...

I'm repairing something that contains a sandwich of 2mm thick alloy plates (unknown spec.), which was originally held together by M2 brass countersunk screws, tapped into one plate. Moisture exposure has caused the alloy plates to develop surface corrosion, looking like filiform corrosion, although the alloy was not coated in any way. Not surprisingly, galvanic corrosion caused the threads to seize and then be damaged or destroyed when the brass screws were removed.

I considered Helicoil-type inserts, but assume that these might also cause galvanic corrosion, as would the use of metallic screws (perhaps Zn-plated would be OK), so we'd be back where we started pretty soon.

Plan B (which seems better) is to make some flanged, square-section, tapped plastic inserts, locating in square-section holes (anti-rotation), and use nylon screws, to avoid dissimilar metal contact. The square would be about 4mm AF. There is no access from the back of the assembly, when it's fixed in place, so conventional nuts are a no-go. Please can anyone suggest a suitable plastic, other than perspex, which can be turned and milled, and into which a M2 (coarse) thread could be tapped successfully?

Jouke - thanks, understood. So it looks like the new saddle is strictly a replacement for the later model saddle, as you mentioned in your earlier post. If it's used with the earlier cross-slide and feedscrew, about 1cm 'inwards' travel will be lost, perhaps? Graham Meek will doubtless address this by a modified cross-slide feedscrew bracket.

Gray, fascinating as ever. Some time ago, I asked whether the Compact 5 should be taken seriously. Clearly, it can be - eventually.

Emco Holz un Hobby's new saddle looks interesting. Am I right in thinking that it has been threaded as the feedscrew's main 'nut', but also has an adjustable, anti-backlash nut deeper down the feedscrew's bore? It would be nice to have all the female threads easily replaceable.

[edit - our posts 'crossed'] Now I'm also waiting eagerly for tailstock mod details.

Now you have a vertical unit for your Unimat, I'm waiting eagerly for your upgrade of the spindle bearings...

We ask a lot of you, don't we?.

Edited By Kiwi Bloke on 28/07/2022 11:56:10

Edited By Kiwi Bloke on 28/07/2022 11:56:32

Edited By Kiwi Bloke on 28/07/2022 11:57:01

A silicone wax polish sounds like a good idea. Anyone know whether there are long-term compatability issues with Al?

I'd prefer to stay well away from hexavalent chromium compounds, so Alodyne/chrome isn't a very attractive option. Also, I'd need only a few ml and it's expensive, even in minimum quantities sold.

Graphite sounds attractive, but would it form an electrolytic cell with the Al, as it does with Cu, leading to pin-hole corrosion in plumbing pipes?

I believe that wire wool should be avoided on soft Al alloys, because tiny bits of steel get embedded into the Al - and you're off with an electrolytic cell again.

I guess the answer is to avoid damp atmospheres...

For some reason, which I don't fully understand, I have set myself the task of renovating an elderly Italian piano accordion. It has suffered from damp storage, but was cheap and, being from one of the better makers, is worth restoring. Like some expensive Italian classic cars, it looks pretty, is full of ingenuity, some 'engineering' is rather suspect, its execution leaves a bit to be desired, and it seems to have been designed to corrode. Fortunately, it contains nothing electrical...

The thing contains slides, to select reed banks. These are thin, delicate strips of aluminium alloy, sliding in aluminium alloy channels, held captive by an aluminium alloy plate - an aluminium alloy sandwich. There's quite a bit of corrosion, which has caused the slides to be stuck. I've mechanically cleaned off as much corrosion as possible, but there will be traces of oxide left in corrosion pits in the material.

Small brass screws have been used in aluminium, with corrosion making some (so far) stuck fast.

Q 1. Is there a non-aggressive chemical treatment to 'kill' aluminium corrosion? It must not leave an oily or sticky residue. Anodising isn't practicable.

Q 2. Any suggestions for removal of corroded-in brass screws (which seem to be made from crumbly cheese)? I'm hoping to release them chemically, and preserve the screws, so not wanting to drill them out.

Q 3. Accordion repairers warn against oiling any of the mechanism because of the risk of fluff and dust build-up. In any case, oil or grease would produce too much drag in the slide mechanism, but would a PTFE-based 'dry' lubricant work, or does it eventually peel off surfaces? Ideally, something is required to prevent corrosion.

I thought it was considered bad practice to load countersunk-head screws in single shear. In this application, a dowel or two would be appropriate: it sounds like the OP has done that (I think...).

Well, I've just looked at the page 'Software license' (sic) on Wikipedia. It answers most of my questions above. It also reinforces my belief that we are all sleepwalking into a kind of hell, where we are mere pawns in someone-else's game. The law seems to have dispensed with common sense and reasonableness. Orwell was so prophetic.

For me, the content is more important than the cover. There's currently rather a lot of evidence that more resources should be applied to editing, rather than fiddling with packaging.

I would be interested to know whether this is, in fact, the case. I use Free software these days. When I bought software, I think that there was a Dire Warning on the disc's package seal saying something to the effect that by breaking the seal, one agreed to a whole raft of conditions laid down by the manufacturer. But, at the time one broke the seal, one could not have knowledge of those conditions. Manufacturers like to restrict individual freedom for all sorts of reasons (generally to try to duck responsibility or for their commercial advantage), but such restrictions may not be allowed by the law of the land. Does a hammer have packaging warning the purchaser that it must not be used to commit murder? I suspect that British law allows a purchaser of a physical item to do pretty much what he will with it, provided that it is not against the law of the land. Such commercial licences are not enshrined in British law. If a manufacturer withdraws a purchaser's right of enjoyment of their purchase, without, for instance, warning the purchaser that that right may be enjoyed for only a limited time, is this legal?

I admit that I have no special legal knowledge, but I'm very sceptical of manufacturers' manoeuverings. I expect SOD or Mr Gilligan will be along soon with an authoritative opinion...

ISO metric coarse series fixings are generally OK in Al alloys, as are UNC. However, there's not much point using UNC these days, since metric fastenings and tooling are more readily available, and it's the modern standard.

When there's effectively an arms race ensuring that most 'anti-tamper' fastenings can be undone, the use of such things can only frustrate the technically backward. It's disgustingly arrogant of manufacturers to have such an attitude toward their customers.

Windows 7, what's that? I gave up with ghastly M*crosoft at XP. Now, I could do with an XP machine, to run some ancient software. I have an installation CD (deep in strata of junk, hopefully not yet fossilized). Does anyone know whether Microsoft will condescend to allow one to use it? Can an installation be activated still?

Perhaps not strictly anti-tamper - but what does that mean? It doesn't look like it would make assembly easier, so it must be to frustrate owners when the shoddy thing's built-in failure mechanisms take effect and an unnecessary fault occurs. Just do what 'they' want you to do - buy a new one, it's good for business. Increase waste. There is no hope for the world.