Here is a list of all the postings Jon Gibbs has made in our forums. Click on a thread name to jump to the thread.
|Thread: Tank Cupolas...|
In all of the photos I've seen the hatches appear to be positioned fore and aft which would suggest that the cupola was fixed but there appears to be a bit of a discrepancy between these photos...
which seem to show the view-port facing slightly rightwards (first pic) or directly forwards (2nd & 3rd).
So, it's hard to know for sure.
Edited By Jon Gibbs on 15/12/2017 15:26:27
Edit: Ahhh, Wikipedia says... "The Mk VIA had a return roller removed from the top of the leading bogey and attached to the hull sides instead, and also possessed a faceted cupola. The Mk VIB was mechanically identical to the Mk VIA but with a few minor differences to make production simpler, including a one-piece armoured louvre over the radiator instead of a two-piece louvre, and a plain circular cupola instead of the faceted type. "
So, perhaps the VIA faceted cupola has the two viewports (picture 1) whereas the VIB has the one viewport facing forward.
Edited By Jon Gibbs on 15/12/2017 15:32:59
|Thread: Which spindle fitting on my milling machine?|
Looking at the spindle diagram on lathes.co.uk the recess is clearly there. It seems quite a reasonable idea for completely preventing any possible MT slippage(?).
It might be sacrilege to suggest this but if the MT3 is simply recessed you could turn the square recess off (or at least reduced in depth) the spindle nose with a TCT lathe tool clamped to the milling machine bed?
|Thread: Old White Piano Key wanted!|
...but we're not talking about trading either a musical instrument or a historic artistic artefact here. The OP wants ivory to restore an antique item.
Not sure whether it's come into force yet but all ivory trading may be banned - at least in theory...
Depending how small the pieces are, I'd suggest either tagua nut vegetable ivory **LINK**
or artificial ivory/bone **LINK**
Plentiful supply and cheap enough.
|Thread: Rust removal methods safe for cutting tools / precision parts?|
This is all interesting stuff but I'm afraid FF that just because an equation that has been reproduced several times doesn't mean it's correct.
It's 39 years since my A-level chemistry but this is pretty basic stuff. A solution of anhydrous citric acid in water is just going to be a dissociated mixture of H+ ions (this is the definition of an acid) and citrate ions (C6H5O7-). All acids will dissolve rust (and iron/steel) and this one is no different. It's a fairly weak acid but will naturally react with the rust reducing it to a mixture of Fe2+ and Fe 3+ ions and citrate ions, liberating water or hydrogen in the process. The iron citrate will then potentially precipitate out, depending upon the solubility of the iron (II or III) citrate (**LINK** and **LINK**), which are both only weakly soluble.
Citrate ions are stable, and so is iron citrate in both forms, and so I agree with Martin that it is highly unlikely that the citrate compounds will decompose and release carbon monoxide.
I'm quite surprised to see the equation quoted above for citric acid action on rust. What's it's provenance?
It's a while since I did A-level chemistry but surely, one would expect at least some iron citrate created (C6H5FeO7) with hyrogen and water only liberated.
|Thread: Using Chalk to Centre a 4-Jaw?|
I take the point that chalk is "close-enough" for some jobs but surely the advantage of the DTI is that you can determine, based upon the job in-hand, when you get "close-enough". Just because you can measure to within a thou, doesn't mean you can't stop adjusting when you get within 10 thou.
MrPete222 posted this in the last few days for a really snazzy DTI holder **LINK**
Mine uses the stem to mount the DTI which has the advantage that if I have a lot to do and can be bothered I can switch it round and check the face too with this type of holder.
|Thread: The 'evolution' of language|
...but I'd argue that in all cases a hybrid is nothing more than a recombination of a previously split line.
Just because offspring are viable though isn't the be-all. Sometimes one of the sexes ends up infertile which isn't particularly smart from an evolutionary p.o.v. - see Haldane's rule **LINK**.
...but it's easy to get lost in theory and forget that behind it all there are individuals choosing, and being chosen as, mates.
...and as we all know, the mate selection problem is a complex one - often driven by mutual attraction, opportunity or otherwise, based upon innate characteristics which loosely approximate to "environmental fitness". In some cases it's also "the best available at the time"
It can even be arranged by human intervention as in the case of domesticated animals which formed part of Darwin's seminal work (esp pigeons).
I'd argue that the offspring, if viable, are really all individuals. Some may be better adapted than their parents to their environment or less so ... but any classification, even if it's based around the potential for inter-breading, is still somewhat arbitrary and a convenience for us.
Edited By Jon Gibbs on 24/11/2017 14:31:17
|Thread: Unusual Rule instrument?|
Seems to be borne out from the scale.
Since weight will follow volume, and given that the cube root of 2 ~= 1.26, the ratio looks about right for the lines 1/2 -> 1 & 1 -> 2 & 11/2 -> 3.
Edit: Also from 1 -> 1 1/2 and 2 -> 3 will be ~1.145 which looks pretty close to me too by eye.
Edited By Jon Gibbs on 24/11/2017 13:29:00
|Thread: Cheap Indexable End-Mill|
I have a fair few HSS end mills, including some roughers, and means to sharpen them.
I don't have any carbide end mills though and I just wondered whether it might be a cheap and handy alternative for cast iron roughing to save too much resharpening or bu99ering up my decent roughers.
Thanks for the warning. My machine's an RF25 which might not be rigid enough although it probably has the speed.
Do you think the interrupted cut problem is because the longer cutting edge is not mounted helically for side cutting, like an end-mill would be?
Thanks very much for your advice. At that price it's just below the threshold for VAT and so has to be worth a punt.
Edited By Jon Gibbs on 15/11/2017 19:31:38
I'm looking at one of these (**LINK**) ...
...and wondering whether it would be useful with my round column mill for roughing out. It's not going to work for plunging cuts but for hogging material.
It's obviously wrongly labelled and this one's got a 14mm diameter and so may be better after shortening and turning down to fit 1/2" or 12mm collets.
Any value or a waste of time? - Any or all opinions welcome.
|Thread: A model engineer gone wrong?|
I take the point about vehicles but they are clearly not as efficient when used as weapons and have other, slightly more utilitarian, applications...
Armed incidents -
Las Vegas - 58 people dead and 546 injured
Paris Bataclan - 130 people dead and 413 injured
Vehicle based -
Westminster Bridge - 4 people dead 50 injured
Barcelona - 13 people dead and 130 injured
On the whole, I accept that firearms do have some practical purpose, but I don't think it's unreasonable to say that in their main use these days is recreational.
I don't buy the claim that markmanship will be useful when we have our next war. IME most marksmen I know will be well beyond recruitment age if a war comes.
Edited By Jon Gibbs on 15/11/2017 16:55:06
I'm sympathetic but comparing the carnage that one gunman in the US was able to achieve in Las Vegas with that possible by any of the Islamist terrorists in London, who thankfully weren't able to get hold of a firearm of any kind, I know which democratic government I'd rather continue to live under.
Edited By Jon Gibbs on 15/11/2017 16:19:39
|Thread: Plug and Hole: Should the metals match?|
In theory brass expands more than steel with temperature and so if you use a brass plug it'll get tighter at higher temperatures **LINK**.
The only doubt I have is whether the plug will drop out when the temperature goes down again.
Not sure this helps
|Thread: Plumbers Black|
Stovax black grate graphite polish is still available for woodburners - see **LINK**
A small amount gets everywhere - just like marking blue
|Thread: myford etc.|
As NDIY says one way is to buy yourself a digital metric/imperial set of calipers or micrometer and use the in-built function
...but if you want to keep the grey cells working I have found that it's just as easy to buy yourself a metric micrometer or even just continue to work in metric and as you're approaching the correct dimension in diameter or length multiply the amount you need to remove in mm by 40 to give you the number of 0.001" (thousandths) you need to take off using the dials - Simples.
The actual conversion is slightly less at 39.37008 but since cuts of more than a mm or two (in diameter) on a Myford lathe can be challenging it's close enough and when you get below a mm the approximation is pretty good.
Once you get the hang of it, it becomes second nature to multiple by 4 and shift the decimal point appropriately.
[Edit: I have an imperial mill and an imperial lathe and work in metric often - It's no bother at all. For the Myford ML7, I bought two 21 tooth change wheels from RDG which give access to almost all of the usual metric pitches - within a gnats piccolo of the correct one and probably well within the accuracy of my worn old feed screw.]
Edited By Jon Gibbs on 07/11/2017 09:13:00
|Thread: Bitcoin crashes...|
This graph reminds me of the dot com bubble - Greedy investors jumping onto a band-waggon that rolls for a while before something causes a realization that the valuations are overstated and then there's a readjustment to reflect more sensible valuations. Predicting that point near to the peak is pretty much impossible for your average investor.
I'm reminded of the adage "it's never a bad time to take profits".
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