Here is a list of all the postings Robin Graham has made in our forums. Click on a thread name to jump to the thread.
|Thread: Tapping drill size|
Harold Hall gives a brief, but useful (to me at least!) discussion of tapping drill sizes on his website here
He also provides tables giving thread engagement at various drill sizes for BA, Metric, Metric Fine and Model Engineer threads.
His site isn't easy to navigate (not complaining, it's free, thanks Harold if ever you read this!) but there's tons of good stuff there.
|Thread: Any geologists out there?|
Arf! Might have a use in the workshop then, hadn't thought of that. Some of the holes are indeed remarkably round, which made me think that there was some physical (eg bubbles in mud - but I couldn't see quite how that would work) rather than organic mechanism at work. But armed with the search term 'piddocks' further googling pretty much confirms that's how the holes were formed. Astonishing, I'd never have guessed that!
It turns out that the same question was asked in the New Scientist a couple of years ago. One of the replies runs thus:
Both shipworms and piddocks exude shell material to line their burrows and prevent them collapsing. The civil engineer Isambard Kingdom Brunel learned from this, and used the same strategy to successfully complete the first tunnel under the Thames in London.
The remnants of (presumably) exuded shell material are visible in my specimen. I wonder if it's true about Brunel though? I can believe it I suppose, he probably drew inspiration for his innovations from many sources.
Last week I took a recuperative break in Lyme Regis. Well known for it's unusual geology of course. Wandering on the beach I came across stuff like this:
I forgot to put a ruler next to it, but for scale the biggest hole is about 15mm.The 'stone' is quite soft and may be compressed mud - but how were the holes formed? Googling has so far failed me.
|Thread: If I were coming here I wouldn't have started there... (possibly)|
Thanks for your replies, and apologies for my delay in responding - stuff happened. Back in the saddle now.
I do take the points about being over-obsessed with accuracy. It doesn't matter too much in this case I agree - I could probably do it by eye - but, as a self-teaching amateur, that's the way that I work. I've read posts from people who have who have had formal engineering training saying that they were required to file down a cube to a thou in size and squareness. Obviously not the most efficient route to the end product but good training. In my own experience, when first I got a lathe I would turn to the limit of what I could measure even when it was unnecessary for the project. That's stood me in good stead in that I can now turn to within a couple of thou confidently and quickly - two thou seems bags of room! It's the same with workholding and the many other things I have to learn. For me it's not all about the destination. In doing something I've not done before I try to get knowledge and skill which will help with something I've not even thought of yet. Lord only knows what the final destination is - for the mo I just like making things from metal!
Thanks again for your comments, Robin
Edited By Robin Graham on 06/10/2019 00:17:08
Just trying to be inclusive NDIY - there are antipodeans on this forum remember.
Thanks for your opinion that my method wasn't insane - I'm self-taught mainly and worry about re-inventing wheels.
I'm bad at planning machining sequences. Sometimes if I want to make a thing involving new (to me) techniques I'll do the operations I know about, thinking "I'll cross that new bridge when I come to it". It doesn't always, or even often, work out well.
This is a very simple project - a handle mounted on a taper, such as one often sees - eg:
I turned the taper then thought how am I going to get the handle true? I've ended up like this:
ie sticking the piece in the mill vice with a v-block and clocking the taper square. It'll work I'm sure, but it took ages to set the work and I have a nagging idea that I could have done better with more forethought. How would this normally be done on manual machines? Any more elegant ways of doing this?
Edited By Robin Graham on 23/09/2019 00:11:26
Edited By Robin Graham on 23/09/2019 00:15:11
Edited By Neil Wyatt on 23/09/2019 13:57:48
|Thread: Machining a chuck backplate|
Adam, I think it will be hard for forum members to answer your question until you explain what you mean by 'better'. Since starting this thread I have made two backplates from cast iron (so I'm an expert!) - they are accurate and work well. I would have found it harder to make them from stainless steel because the stuff is (in my experience, on my machines) more difficult to machine to tight tolerances.
I can't think what advantage stainless would have except that it'll probably stay shiny for longer.
|Thread: Ultrasonic toothbrushes|
Dave, I thought (before reading MichaelG's credible hypothesis about foaming) that Ruppel's SEM image must be of a solid structure and hydrated silica seemed the best candidate given that it's odd, amorphous stuff. Maybe I should have said 'most' rather than 'only'. Do you see an alternative if the image is of a solid in the toothpaste?
The doggy utrasonic toothpaste is indeed peppermint, which our dogs detest. We also have enzymatic (non-ultrasonic) dog toothpaste which is flavoured with 'poultry extract' - I try not to think too much about that means! Problem is they like it so much that they want to eat the toothbrush.
Sadly I didn't get the opportunity to test the brush on rust today but I did look up ultrasonic derusting in case it was a crazy idea. It seems that it should work - I'll give it a go when I can.
pgk - I reckon you could be onto a winner with your quinoa and goji berry idea. But:
The pet food manufacturer looking for new flavour ideas wasn't keen on my suggestions of Robin with Mouse flavour.
Over my dead body mate.
Edited By Robin Graham on 02/09/2019 01:32:24
Edited By Robin Graham on 02/09/2019 01:37:20
It appears so Michael - the need for a special ultrasonic toothpaste is clearly one of 'the aforementioned problems' listed in paragraph three. But then on numbered page 7, describing how the invention is to be used, they give the first stage in the process as follows:
- distribute ultrasonic toothpaste lightly on the insides and outsides of the teeth
So ultrasonic toothpaste is still necessary? I'm even more confused now!
pgk, I agree with your last post and your earlier one when you suggested (I think) that the defining quality of 'ultrasonic toothpastes' might be to do with viscosity/surface tension. But Michael's tentative explanation of Ruppel's SEM image could be right. If so, we need to know how the 'implosion' (yes, I noted your inverted commas Michael) of bubbles in fluid might enhance the ultrasonic cleaning process.
Pending a response from Emmident I shall later today try the toothbrush on a piece of rusted steel with normal and ultrasonic toothpastes to see if I can detect a difference. I'll get it in the neck from the Mrs if I knacker the brushes, but sometimes one has to suffer for science.
Edited By Robin Graham on 01/09/2019 01:09:06
Edited By Robin Graham on 01/09/2019 01:16:52
In the absence of any compelling evidence to the contrary I'm thinking that there's nothing special about the ultrasonic toothpaste - at least two members of the hive mind here are getting good results on their own teeth with US brushes and the normal stuff, but no-one has buzzed in with a plausible explanation of why the expensive toothpaste is advantageous. I think it may well be a sales* ploy.
Trawling further through Emmident's sales stuff on their website I see that they give a hand-waving explanation of the ultrasonic cleaning process - that's fair enough, if they went on about Laplace pressure, vapour pressures, surface tension, shock waves etc they would rapidly lose their target audience. But it does seem that they cite Ruppel's images of microbubbles (which surely must be static structures given the timescale of SEM?) as evidence of cavitation - they seem to be conflating ideas of static and dynamic microbubbles. Maybe the static microbubbles in the image serve as nucleation centres and promote cavitation? That seems feasible, but if so why not just say it? I shall email them and report back if I get an explanation.
Anyhow, thanks for the discussion, I've learned some stuff.
*Wrist slapped by a marketing manager for saying 'marketing ploy' on another forum. It's the sales people who do the bad stuff apparently.
pgk - thanks for your interest in this conundrum and for taking the time to consult your professional colleagues - I'll be interested to hear what they say. Thanks also for the aspergillosis tale - that made me laugh, a welcome relief from my wearying worries about dog toothpaste.
MichaelG - I'm sort of almost half convinced by your hypotheses , but I wonder where Ruppel's image fits in with your scheme. I don't know much about SEM, but I think exposure times are far too long to capture a 'snapshot' of cavitation, or even foaming on that scale - small bubbles in fluids are pretty unstable. I might be wrong about these things, but that's why I thought his images must be of solid structures and the only candidate seemed to be the hydrated silica.
I wondered if the the confusion might be because MichaelG's link was to Emmi-dent (the version for humans) but the ingredient list I quoted came from the back of a tube of Emmi-pet. Not so - further research reveals:
Aqua, Hydrated Silica, Sorbitol, Propylene Glycol, Tetrapotassium Pyrophosphate, Xanthan Gum, Sodium C14-16 Olefin Sulfonate, Aroma, Titanium Dioxide, Sodium Fluoride, Sodium Saccharin, Allantoin, Limonene, Mentha Arvensis Leaf Extract, Chamomilla Recutita Flower Extract, Salvia Officinalis Leaf Extract, Sodium Methylparaben.
for Emmi-dent. So essentially the same formula, but with the omission of sodium fluoride in the pet version presumably because of the toxicity problem JasonB highlighted. So still mysterious and possibly mendacious - though I suppose it might depend on how 'abrasive' is defined.
The German version of the patent for the toothbrush yields no more pertinent information than the summary in English. It says that there is an ultrasonic transducer in the head of the device which is connected to a battery and pressing the button causes the thing to work. I'm surprised that the patent was granted (if it was) - prior art surely? Ultrasonic cleaning has been around since the 1950's it seems.
My Teutophone friend translated Manfred Ruppel's letter for me and came up with 'clearly shows the presence of micro bubbles' rather than the 'clearly shows the formation of ...' in the English version of the letter which Michael found. I don't know if that's significant, but I do know that Ruppel's observations are scientifically valueless in the absence of information about what exactly he has imaged, and under what conditions (ie context).
I'm no further forward in understanding how Emmi-pet/dent toothpaste enhances the mechanism of ultrasonic cleaning. I suspect it's a sales ploy.
Edited By Robin Graham on 28/08/2019 01:29:30
Well, yes. But ingredients are Aqua, hydrated silica, sorbitol, glycerin, disodium pyrophosphate, tetrapotassium pyrophosphate, xanthan gum, sodium C14-16 olefin sulphonate, sodium methylparaben, sodium saccharin, aroma, CI 77891. CI 77891 is TiO2.
All very mysterious!
Thanks for further digging Michael - I wasn't disputing Ruppel's credentials, it's just that he doesn't give us much context for the image.
Coincidentally I am expecting a someone who earned her crust by translating German tech documents to drop by tonight. l'll ask her about the patent.
I did indeed Michael - I followed the link but wasn't quite sure what I was looking at. In the English translation the author says of his SEM image:
"it clearly shows the formation of micro bubbles which will implode in the process".
In my first read through I took 'formation' to mean 'bringing into being' rather than 'existing in a particular shape' as, for example, in 'a rock formation'. Then I realised that SEM could hardly capture cavitation on the timescale of a 1.6 THz oscillator. So the micro bubbles must be static features in the toothpaste. The only credible candidate in the ingredient list is hydrated silica. Further research is needed!
Johnnyboy25 - first thing I said to my wife when she suggested it, ultrasound, it'll drive the animal mad. But it seems these things work at much higher frequencies than dogs can hear.
XD 351 - dog was rescued from a bad place - we're just trying to get her back to the state of normal dogness where toothpaste and bogpaper are unnecessary.
Edited By Robin Graham on 25/08/2019 23:16:57
Thanks. The device in question is an Emmi-Pet (about 2/3 the cost of a Femi bandsaw, priorities are all wrong round here), so a proper ultrasonic I think. It does seem to be working - plaque is beginning to flake off and the animal's breath, though not sweet, seems to have less of the whiff of Satan's cesspit.
I think MichaelG's second link answers my original question:
Toothpaste without abrasive particles
While you could theoretically forego using toothpaste when using a conventional toothbrush due to the brushing motion, using the special ultrasonic toothpaste for micro cleaning with emmi®-dent is a must. In contrast to standard products, our special toothpaste is free of abrasive particles that could permanently damage your teeth’s enamel. This is why ultrasonic toothbrushes not only prevent gum inflammation and periodontitis, but are perfect for people with sensitive gums or with pre-existing gum problems.
The first sentence seems to me almost meaningless. What follows suggests that the special quality of their toothpaste is that it's non-abrasive - nothing to do with ultrasound transmission, so I reckon gravy and dog slobber (thanks Adrian) should work.
Edited By Robin Graham on 24/08/2019 23:55:42
My wife has bought (at considerable expense) an ultrasonic toothbrush for use on the hounds. It came with a tube of special ultrasonic canine toothpaste (peppermint, which they really don't like) and a warning that we had to buy their special paste (at £15 for a 44g tube) or it wouldn't work. I doubt that, but maybe there are ultrasonic experts on here who could advise?
|Thread: Profiling tools|
Thanks for further discussion, Dave (SoD), yes, I know about the cubic inch per minute per HP thing but I think your second limit is the rate determining factor - in my case at least. My lathe has a 2HP (on the plate - input or output not specified) motor but I'm pretty sure it wouldn't be up to taking 2 in^3 per min! Obviously there are a lot of other variables as you say. I shall experiment!
Michael - I had the same misgivings about the way the device was mounted. I'd not heard of Gibraltar toolposts (why Gibraltar? Rock solid?) but my plan was essentially the same - a solid post mounted on the cross slide. I rarely need the additional degree of freedom given by the top slide - it mostly just gets in the way, so I'll be going along those lines.
Thanks also for links to cheapo cutters! Ebay came up with 'you might also be interested in... Ten CCMT inserts for 3.99
Rude not to! Especially as I get a 24p discount. For some reason.
Edited By Robin Graham on 22/08/2019 23:18:09
Edited By Robin Graham on 22/08/2019 23:18:25
Badly . I should have said Pi=6 obviously*. You are right of course!
Thanks for discussion, and in particular for Jason's pic - it may be that I'd be better off making custom cutters from silver steel or gauge plate for ornamental work in brass. If that can be done with a 280 I have no excuse for not doing similar with a slightly heavier machine.
I'd actually ordered a couple of RCGT inserts from JB cutting tools anyway - I've been surprised how well GT type inserts work with brass, despite having quite an aggressive positive rake. They seem to work well for finishing cuts in mild steel as well.
*There's no fundamental reason why Pi shouldn't equal 6, it just needs confidence and a determination to make it happen. Apologies if that breaches forum rules.
Edited By Robin Graham on 20/08/2019 21:32:01
Edited By Robin Graham on 20/08/2019 21:37:29
Edited By Robin Graham on 20/08/2019 21:42:33
I was looking at designs of radius turning tools based on boring heads and came across this video. The author (Ade Swash) uses an RCMT 06 carbide profile insert at the business end of the the tool, and it looks like it works well. He also uses the same insert for cutting the relief in the stock for his ball turning demo.
Hmm I thought, I've got one of those 6mm diameter profile tools (bought when I had only a tiny lathe which couldn't cope with it), maybe it'll work with the bigger machine I have now. It did, once I'd conquered nerves and was assertive with the cross slide, like you have to do with parting.
Question is - how big a profiling tool can one run on a 'domestic' lathe? I had a look at JB and they list up to 25mm diameter which would be 75mm (pi=3) cutting engagement if plunged to radius. Surely that would need a very big machine? Even 12mm would speed things up for me though if possible.
I have a 12x36 lathe and I'm working in brass.
|Thread: Pet peeves!|
Dog who howls insanely every time I descend to my cellar workshop because she thinks that's where I keep my pork scratchings. She's right in that, but makes the mistake of thinking that the only reason I ever go down there is to scoff unhealthy snacks. A very peeving pet!
Edited By Robin Graham on 16/08/2019 01:12:20
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