Member postings for Robin Graham

Thanks. I have ordered 12mm holders from RDG and inserts from ARC. So I'm sorted for what I want to do. I had a look a Denitool, but it's easier to just press 'buy' - 12mm is OK.

Good to hear that Jenny is still active - she was very helpful when I was in the market for threading inserts, which in their variety can confuse the amateur,

Robin.

I want to buy a couple of 45 degree holders for square indexable inserts - primarily for chamfering. ARC do them, but they seem to offer only general purpose (SCMT 06) inserts for holders under 16mm - the only inserts for non-ferrous metals they offer are SCGT 09, so I would have to buy 16mm holders. Could do, but it's overkill for my needs. A search on SCGT 06 hasn't turned anything up - maybe such things don't exist for some reason?

I had a look for JB cutting tools but was directed to a Companies House entry saying that the company has been dissolved . That's a pity.

Any advice (other than grind your own out of HSS!) would be welcome.

Robin.

Edited By Robin Graham on 10/07/2022 23:10:00

I buy an unconscionable amount of stuff through Amazon partly because it's convenient but also because of the reviews. It's often possible to distinguish between ridiculous stuff ( eg: Slot Head Brass Woodscrews "they don't fit a Pozidrive driver which is standard nowadays, and the head just breaks off when you tighten them 1 star DON'T BUY" ) and genuine problems which appear again and again. But sometimes with 'niche products' (I'm talking taps and dies for example, not 'exotic' items) there are few reviews in native English and I resort to the opinions of Johnny Foreigner. I have realised that for some reason I value the opinions of French and German reviewers above those those in the UK and the rest of Europe. From North America I tend to trust those from Canada more than those from the USA.

I'm not sure how these prejudices have arisen in me. I'd be interested to know if others have similar irrational tendencies.

For pedants (I'm looking at you MichaelG ) I know it should have been 'whom' in the title, but tempora mutantur, nos et mutamur in illis . And all that rot.

Robin

Edited By Robin Graham on 03/06/2022 01:27:40

Hi Neville. From your opening post I assumed that you had some specific need to use the Proxxon chuck. As the thread has evolved it looks like you are planning to buy one, and I wonder why.

It may be that you are thinking that because Proxxon stuff is generally well made the 4-jaw will be a cut above the (much cheaper) Chinese/Indian offerings. That is not necessarily true. My first lathe was Proxxon PD400 which came with a really lovely Rohm 3-jaw - smooth and accurate. I ordered a 100mm 4-jaw (~£200) assuming it would be of similar quality. I received a Proxxon branded item which proved a real pain to use - very sticky with screws binding in the casting. The 4-jaw which came bundled with my Chinese lathe is far smoother. Looking at your Amazon link I see two reviews, one saying it's 'well manufactured and functions perfectly' and the other:

'The level of "precision" is just atrocious. There are no two jaws that would be of the same height. The machining is just sloppy with a lot of "apprentice marks" like burrs, uneven angles and discoloration from overheating. There is a lot of grinding dust and metal chips in the jaw screw threads. The starts of threads of the jaw screws are misshaped. The screws are binding in the head even without the jaws installed. Hopefully it all can be fixed but the chuck is absolutely not worth the money.'

My experience with the PD400 chuck wasn't as dire as that of second reviewer, but closer than that of the first.

Apologies if this isn't relevant to the decisions you are making Nevillle, just my two ha'porth (as we're going back to imperial).

Regards, Robin.

Edited By Robin Graham on 02/06/2022 23:10:28

Thanks for replies. I'm actually happy that nobody has been able to explain the table in my opening post. Not having an engineering background I've had many 'Oh gawd, here's another mysterious thing I have to understand' episodes and I thought this might be another. Seems not - the table is just wrong, even allowing for sign changes.

Mick - thanks for pointing out the 40HRC /Glass hard thing, I hadn't noticed that because (apart from difficulties with the numbers) I couldn't really understand the layout of the table. I can cope with 2-D ISO tables!

I have ordered a reamer form ARC, which whilst not 'industrial' will doubtless be more trustworthy than the Amazon offerering.

Comments about the importance of technique and ancillary kit (floating holder) made me realise that even if were to spring £40 or so for a Guhring or Dormer I still wouldn't be guaranteed H7 tolerance. Doh! Well I'm here (primarily) to learn and the comments made me think, so thanks.

The job is one of those 'help someone out' things which crop up from time to time. The 'client' has now agreed to send me the broken bushing so I'll be able to make an accurate copy without worrying about standards. It's been an educational thread for me though.

Robin.

I want to make a bushing with a 7mm hole specifically to H7 tolerance. I had a look for a suitable reamer and came across offerings from sourcingmap on Amazon which have the merits of being cheap and being on next day delivery. However I can't understand the table of technical info:

I can't reconcile this with info from other sources which all tell me that 7mm H7 should be between 7.000 and 7.015mm. For example, the entry for 6.5 - 13mm above suggests that for a 7mm mm reamer D will be between 7.000 and 7.005 mm and the H7 column gives a tolerance of +0/-0.027mm. Which seems to suggest the reamer might actually cut under size. Am I misunderstanding the table?

Perhaps I should steer clear and buy elsewhere ( think I probably will actually, ARC's offerings are only a few quid more and they deliver pretty quickly) but I'd like to know what the table above means. If anyone can elucidate I'd be grateful.

Robin

Thanks Duncan, and apologies for delay replying - reply notification got swamped in my inbox. That looks like it should do what I want. A rotary switch would be actually be even better than a toggle for this application.

I'm confident that the existing switch is break-before-make just from visual inspection of the innards.

Robin

Edited By Robin Graham on 13/05/2022 22:09:09

Should have said that if it goes to stage I'll insist that ME gets a credit in the programme!

R.

Thanks Duncan, I had wondered about a rotary switch but I'm obviously out of my depth with this - I had no idea how many different types of switch there are. A rotary switch would be better for this application than a slider from the operator's point of view, so any further input would be welcome.

I got involved with this project because someone else in my town gave up on it and suggested to the 'creatives' that I was the man for the job. The 'creatives' of course see only the effect and are oblivious to the complexities of the mechanisms which underpin their performances . I'm in a grumpy mood!

Robin

Well, I found some 8-pin DP3T slide switches on Amazon (for the princely sum of £6.49 for 20!) and have ordered them. They'll probably be pretty cr@p at that price, but hopefully at least one will be for OK enough for this job.

In the course of my researches I came across a lot of 6-pin slide switches described as DP3T so obviously the designation doesn't specify the switch uniquely.

I also came across a 12-pin DP3T On-On-On toggle switch. A toggle switch would actually be preferable, but I can't see how this one could be made to work in my application. Here is the schematic:

I can't satisfy myself that it's impossible though! If anyone can see a way that it could work or reassure me that it's impossible that would be educational.

Thanks again for help, Robin.

Thanks all, DP3T On-On-On it is. Now I know that I can go ahead with this.

Robin

-Thanks for further advice. Looking more closely at the switch:

it seems likely that if I bend the sides outwards the whole thing will fall apart and reveal pads onto which I can solder.

I'm having trouble finding a replacement though - searching on DPCO as suggested by Mike brings up switches with two rows of three pins rather than the type I need (see earlier sketch). Does anyone know what the configuration I want is called?

Robin.

Thanks for advice. I had hoped that I might be able to get away with leaving the switch in position, but after reading exchanges between Nick, Martin and Noel:

I took a multimeter to the switch and found:

The hatched things are pcb tracks - I can see the L - shaped track connecting 2,6,7 on the component side and infer the existence of one between pins 5 and 8 because they are connected at all switch positions. Presumably on the other side, obscured by the switch body. I have also inferred the switch connection between 6 and 7 in the 'off' position - symmetry seems to demand it!

The problem with leaving the existing switch in the 'off' position and wiring up another one seems to be that pins 2 and 3 will remain connected in 'on and 'demo' modes. Maybe that wouldn't matter but I can't be sure.

I'll have a go with the wick, but if it doesn't look like it'll work I'll resort to Nick's suggestion of destroying the switch - drastic as it seems it might actually be the least risky option.

If anyone's interested the board came from a (now obsolete) Hasbro FurReal toy pony. You can see it here. They cost over 1000 USD when launched I'm told!

Robin

Edited By Robin Graham on 09/05/2022 00:38:01

A while back I took on a community project to repurpose a robotic toy for use by a 'performance artist'. I've got the mechanics sorted out, but I now realise that I need to move the toy's control switch from the 'brainboard' to a remote location. This is the switch from the top:

and from the rear:

My first question is: What are the odds on me removing the switch from the board using solder wick without knackering anything, given that I've zero experience with this technique?

Second Q is whether I even need to remove the switch - perhaps if I left it in the 'off' position I could just take wires from appropriate pins on the back of the board and replicate the 'demo' and 'on' states with a new switch.

Any advice would be welcome!

Robin

Thanks for replies - especially for Joseph's and Nicholas' detailed explanations of what's going on. I think I now understand things better.

Hopper - encouraging to know that you are having good results with gasless. I've looked at some YT stuff about these low-end machines, but after 10 mins of watching a guy opening a cardboard box, ( I think I'm OK with that) followed by shock that that it doesn't have a plug &c &c I begin to lose the will to live.

The main thing I was after was confirmation that the machine is meant to work in short circuit mode. I had incorrectly assumed that MIG machines were designed to maintain a constant arc length.

The welder I bought is of the 'idiot proof' type - just choose gas or gasless and wire size, twiddle the single knob to give the 'power' you want and the machine figures out volts, amps and feed. It works, at least on thin (1.2mm) steel which is all I've tried so far, I just need to get used it.

I'll have a look at the MIG site, thanks for the link Anthony.

Robin.

Edited By Robin Graham on 02/05/2022 22:05:53

A few weeks ago I posted a question about cheap gasless MIG welders as I was having trouble welding 1.2mm steel box section with my MMA machine. I have now bought a cheap (£150) machine and it's night and day - half an hour's practice and I'm making satisfactory welds using flux cored wire.

The hardest adaptation I had to make was trusting the machine to get the wire feed right as I'd (sort of) trained myself to keep a constant arc length with MMA. This resulted in me moving the MIG torch away from the work when it looked like the wire was going to touch the weld pool. The machine responded by squirting out more wire of course, with bad results.

I've now discovered that a 'standard' MIG process is short circuit/arc/short circuit etc, and maybe that's what the machine is trying to do. Would this be normal behaviour for a low-end MIG welder? I'm happy that it works of course, but would like to know what's going on. The manual that came with the machine is pretty much unintelligible but does refer to an 'inductance' setting which isn't explained but might be something to do with with limiting current in the short circuit phase. I'm in that foggy area where you don't even know what the right question to ask  is with this, Any elucidation welcome.

Robin

Edited By Robin Graham on 01/05/2022 02:42:43

I'm not sure how serious you are in this list-making endeavour Michael. If you were inviting pet hates and puns (of which there have been a few), well it's made for an entertaining read. But entertaining the possibility that you are actually trying to enumerate the finite denumerable set of words which have non-unique mappings to a (possibly!) infinite non-denumerable set of 'meanings' I think you may have a task which would have defeated even Heracles. I'm not very sure it can be done. You might be better off trying to populate the set of words which have unique mappings - it would be the null set I suspect, It's a wicked project though, I have to say.

Fowler has views of course - his take is that ambiguities arise not so much from words but from the ways of putting them together. Which seems sensible.

Robin

Edited By Robin Graham on 24/04/2022 01:52:33

Edited By Robin Graham on 24/04/2022 01:53:39

welder - many thanks for your kind offer. I have sent you a PM.

John Doe 2 - I don't think the suggestion of hiring has been made earlier. It looks like I could hire a MIG for about £60 a week, but I'd have to buy or hire gas on top of that. Might as well go the whole hog and buy a welder - bound to come in handy in the future!

Dell - unfortunately I am about 100 miles away from you, but thank you for your generous offer of help. Had you been nearer I'd have been round like a shot. Aluminium would actually better for this, but I couldn't find anyone local with the skill/kit to do it for free - it's a "community project".

It might seem nuts that I'm considering buying a new welder for an unpaid one off, but that's how it works for me. My workshop activities are more about journeys than destinations I suspect.

Robin.

Yes, I think that makes sense Phil - thanks for your input. What I've been doing is making a series of tacks as in A in this sketch:

Sometimes (~70%) it works, sometimes it doesn't. When it doesn't it's because once I've blown through the cut edge the arc just runs away and makes it worse. Would you do something more like B? That is traverse across the 'non cut' bit without any weaving and let the pool melt the cut edge?

I've pretty much given up using stick welding for this project because I need 100% success when I make the frame and I'm not going to get there in in time.

I have now tried silver soldering, which I can do confidently, but I have never tried a joint like this before - I was worried that it would be weak because it's (sort of) a butt joint. I was surprised how strong the joins are though - after application of a FBH the tube bent and the joint just gave me a smug look. More expensive and slower than welding of course, but it'll get the job done.

Robin

Apologies for not referring to your post directly Dave - I think you nailed it when you said it is as much to do with physics as chemistry, Perhaps even 'more' rather than 'as much'? As Michael had asked for an explanation of the chemistry I was attempting to give some background as to why a chemical explanation doesn't work by referring to the chemical basis (ester hydrolysis) for fat breakdown by the individual components of the mixture.

IPA is good for many things, but being a polar solvent isn't great for grease, as Grindstone Cowboy found. Ideally one would use dichloromethane or chloroform for pure solvent action, or a solution of sodium dichromate in

concentrated sulphuric acid for pure chemical action.

I'm not sure how one would make a paste of caustic soda in water? Sounds a bit dangerous...

Robin