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Member postings for mgj

Here is a list of all the postings mgj has made in our forums. Click on a thread name to jump to the thread.

Thread: loctite 638
11/09/2009 08:45:14
Well - you know the silver solder will have a strength approaching that of the parent metal - though you can look up the figures in detail.
 
Then you work out your bond area for Loctite, and look up the shear strength of that bond at that service temperature. You know the area of the bond and you can work out the load.
 
With respect that is not a question that anyone can answer at a a distance, because, to give a decent answer you need to know these things. Unless you want to go by experience "I loctited my injectors/item x/item y and that held Ok so it would be Ok on yours". Well it might be, and it might not, just depending on the conditions.
 
There is one important point though - get it wrong, and in that sort of application, even a decently made bonded joint will fail. A silver soldered one is most unlikely to.
 
For my money, I'd stick with the silver solder - its just so quick, neat easy and sure. Still, others may have done perfectly well with other methods
Thread: General club questions
10/09/2009 23:24:11
Well if you need a hand with the heavy stuff or whatever.
 
I just liked a morning trolling round some of the kit, and talking to people, just to see how things were done.
 
And to maintain a bit of enthusiasm - to see finished items working!!!!!!!!!!
10/09/2009 18:14:32
Chris H - I'm a member of Yeovil and District. they are mainly locomotive orientated but very pleasant (not that they are mutually exclusive). Have a range of interesting talks and a club loco you can learn to drive on.
 
I have to admit, I have been so keen on building I haven't gone to a meet, but they are a nice bunch.
 
The track is on the Crewkerne side of Yeovil on the Westlands airfield.
 
 
Thread: Overloaded website
10/09/2009 18:07:42
Mine takes a few second to load initially, but once I'm in on the page its pretty quick.
Thread: Emgineering Glues
09/09/2009 17:46:25
DSB thanks for that.
 
It does just make the point that while all glues stick, it is a huge subject, and while using x or y may not matter in many cases, in others the choice can make a big difference.
08/09/2009 22:09:06
If you want to see what just Araldite (CIBA Geigy) makes, just click on the link at the top of the page. Educational!
08/09/2009 18:16:36
With respect - I would ring the Tech Services Dept of the makers of your glue.
 
There are all sorts of superglues, some being gap filling (thick non slump)  some being "ordinary" and some being high speed ultra thin types.  -with different peel and bond characteristics. 
 
In the same sense, some glues will out perform others, and others are optimised for all specific applications. The loctite type are one batch of chemicals, (isocyanates?)the cyanoacrylates another which depend on moisture for setting and all sorts. 3M make the 2 pack spray instants. There are shock resistant epoxies, chemical resistant, water resistant (important with epoxies which bond readily to water after setting) and one for every other specialist application.
 
If the application is at all critical, choose a good industruial make, like Devcon or 3M or CIBA Geigy, and talk to the maker before using.Tell him what you want to stick tegether and describe the loads and service conditions, and you'll get a good answer. 
 
Far better than we can give.
 
 
Thread: Harrison M 300 (1978)
06/09/2009 11:14:00
I don't know about Harrison gearboxes, but I know a little about Delrin.
 
It has the advantage of being cheap. And easily machinable too I suppose.
 
The real problem with it is that it is immensely hydroscopic, and when it does absorb water it expands quite significantly.
 
Its notorious for jamming  gearbox and steering linkages where it has been used for plummer blocks and rod guides, and there was one other case where the absorption of water caused vast inaccuray in anti tank ammunition.  We have also had the problem where, in the dairy industry, people have tried to save money over PTFE, and the stuff has jammed shafts, or tried to jam them and then worn very quickly.
 
So that might be a pointer.
 
--------------------------------
Have you given Harrison a ring. The website is harrison.co.uk.
 
Buck and Hickman stock them so they are distributors, and they have a website with a phone number.
Thread: ER32 etc collets
05/09/2009 08:44:18
Chronos do ones by Vertex.
 
I agree about the  ability not to have to use a drawbar.  Being able to pass the rod through the chuck saves a lot of material, and means you can work on longer objects if need be - (and removes the temptation to leave long overhangs forwards, just to get the job into a holder?).
 
Runout - depends on the fitting I suppose. I have one for ER25 collets which screws onto the nose of the Myford. That was a commercial item, and typically the runout is about .001". I have a chuck for ER32 collets which I put, very carefully onto a D1-4 camlock backplate for the bigger lathe, and the runout is more or less zero. (Normal method - drill clearance holes for the bolts. Soft face hammer till runout was not detectable. Tighten and then 3 dowells + loctite)
 
I suppose that they are fine for close work, but, if it has to be 110% right then you are back to the DTI, and  4 jaw or a Griptru?
Thread: 1.1/2" Allchin
31/08/2009 21:02:53
What do they say - for the guidance of the wise and blind obedience of fools!!
31/08/2009 19:51:03
I wonder if you aren't making the same mistake that I did when I kicked off with my first TE - getting mesmerised by the drawings.
 
Obviously everything in a sub assembly has to fit, together, but up to a point, if you use a bit of 1/2" steel for part x, and the drawing says 9/16, it probably is not going to matter too much unless appearance and strength are greatly affected. And most drawings make no mention of tolerances or clearances!
 
So if as I did (and the Little Samson drawings are very good), you misread the hornplate fittings and omit a 3/8" dimension  - well Ok the crankshaft is 3/8 too far forwards on the model - so the cylinder assy will be moved forwards 3/8 inch, and the blastpipe will be 3/8 shorter, as will the LOA.
 
This is a tragedy I shall just have to live with, and while I do so I shall reflect on the fact that these things were assembled by blacksmiths, and the dimensions of the originals varied too. And on the fact that my LS is sitting on all 4 wheels, that everything goes round where it should, without binding (all home cut gears and blanks) , running in (apart from the cast gears in the compensating centre), or other fiddling.
 
So its going to work - soon.
 
With all due deference to the purists. If you have a 1/2" shaft, right or wrong, then you will know you need to make a 1/2" hole in whatever fits. Spacing of gears and things like piston/con rod lengths and crank throw are bit more critical, but if you have one bit, in the main you make the other to fit!
 
Thats not to say that getting it dead right isn't best (Even allowing for those occasions where is says fix dimension from model!). Of course.
 
(Next is a 4" Foster!!)

Edited By meyrick griffith-jones on 31/08/2009 19:56:06

Thread: Home Casting in Mazak
30/08/2009 23:32:38
Not an expert at all in casting - merely an observer on the Defence QA side. Armour castings, engine blocks, and one or two other funny things in funny materials.Some of the larger single crystal stuff and some of the exotics being cast under argon.
 
I should apologise if I used the term "dry" loosely - I am familiar with mould construction. I was really referring to "liquid" or "spare" water. which can also lead to hydrogen embrittlement in those materials prone to it.
 
Could I reword that to say that ones process control in making a mould needs to be up to speed with respect to both design and material content, or the pouring process can be frustrating at best, and very interesting at worst?
 
As an aside, but it does show what a bit of water can do. We had an embrittlement problem in ferrous armour welds. No one could track down the problem source. In the end it truned out that they were using the rod drying oven to heat their pies, which gave off steam which got into the rod coating, and since welding is a casting process....... Water control is quite important in castings, even as vapour in small quantities, which is why the MOD specs controlled the amount of water to be used in moulds very closely indeed. 
 
 

Edited By meyrick griffith-jones on 30/08/2009 23:40:43

Edited By meyrick griffith-jones on 30/08/2009 23:47:40

30/08/2009 19:29:46
Water/damp. Also applies to whatever you are using as a mould.  Must be bone dry.
Thread: Lathe for Beginner
29/08/2009 22:30:34
Chris its plenty curable.
 
There's the expensive solutions like fitting ball screws. Deluxe, quality result, best if you have a DRO, because you may  end up with a funny amount of thous per turn. (or .01s of a mm)
 
Step 1 is to check the handwheel/feedscrew clamp at the  x slide bracket. Make sure that's adjusted properly. If you can, fit roller thrusts. Very cheap very easy, which is why I have never got round to doing it on the Myford (but it is properly adjusted!) All the Chinese kit and the Dore Westbury has them. Worth doing.
 
Step 2. The easy DIY fix is to knock up a tap in silver steel. ie thread cut and then gash the flutes. (or try Tracy tools) Best if it matches the threads very closely, bearing in mind the tap cuts the spaces. But if they don't well its not a disaster. What you are going to make is a feedscrew nut extension, secure the two together with a couple of allen bolts (or even a bit of tube and Loctite retainer though that's not as great on bronze feedscrew nuts as it is on steel) Pop a few shims in between the old nut and the new bit. Backlash gone.
 
If it bothers you. If your slides are properly adjusted, and you always come back beyond  ie you always physically drive the slide into position, then its not really a problem, except possibly on an interrupted cut. (But hten you just lock the slide)
 
You may find a new feedscrew and nut is pretty economical too. Quality has improved a lot.
 
If you need a tool ground up, let me know and the Quorn will oblige.Won't take more than a few minutes. You'll have to set it in a toolholder at the helix angle, or it'll rub while you are screwcutting, (sorry Granny) but apart from that, cutting acme threads is no more difficult than any other.  Any of the screwcutting books will tell you how to work out the helix angle for your thread. That allows a setting flat to be ground, and the correct offset to be applied on the Quorn (in rotation) The operator just puts the flat up against a setsquare.
 
 

Edited By meyrick griffith-jones on 29/08/2009 22:32:02

Edited By meyrick griffith-jones on 29/08/2009 22:35:10

Thread: Malcolm Stride has passed on.
29/08/2009 20:11:59
Surely.
 
I am not really a modern IC man, but I very much enjoyed his articles.
 
Very sad.
 
 
Thread: Lathe for Beginner
29/08/2009 17:42:21
Chris if that's the thing i think it is, someone at the Taunton MES built a lovely 5" gauge Hunslett type loco with it, and was pulling himself and a pile of kids too.
 
Models are getting bigger as capability gets cheaper, and for anyone buying machinery nowadays, I'd go for the biggest I couldn't afford.
 
I've done tiny work on a 6" lathe - just by sticking a collet chuch on it., but you cannot swing a traction engine flywheel on a Myford. -depending on scale I suppose.  Also size does matter because of the increased rigidity and imporvement in finish. (Very crudely stiffness increases in proportion to D^4 . So very small increases in dimension make a huge difference to stiffness)
 
BTW D^4 refers to a solid shaft but the general point remains good.
Thread: Digital editions of Model Engineer and Model Engineers' Workshop.
29/08/2009 10:21:54
I don't think you do have full copyright to the full magazine do you. Authors, or their executors if dead retain copyright. Unless its a condition of publication that authority passes in whole or in part to the publishers.
 
Typically if you publish, the agreement is for once only reproduction.
 
Anyway, I would welcome the ability to search an archive electronically and then pay for a down load.  I have a whole steamer trunk full of MEs going back to I don't know when. I was ill some years ago and laid up for 10 days, and I still couldn't get through them all. So whoever does sort scan and keyword the whole load deseres some sort of recompense IMO.
 
Quite a lot of sites in the engineering and reference world, (refence libraries) have a summary of articles, - steel specifications or whatever. That sort of thing.  So you click on it to download, and there is an invitation to stick a credit card number in there. I don't see that as being unreasonable.
 
(You want Young's Modulus for TP304L stainless and you ain't going to get it for free!)
Thread: Digital readouts
28/08/2009 17:30:00
Make sure the console is a universal one then.
 
I don't have much experience of this, but some i know are milling consoles, some are lathe ones, and some are universal.
 
I set my Warco Supermajor mill up. I just read the instructions, ensured that all was set up well within the tolerances quoted for mounting the scales and fitted them with decent covers. Ensured the head carriers were good and well (miles) over solid and won't flex. Works brilliantly and is accurate to .0002" though the spec say +/-.0008. To mill to 2 tenths is fine by me.
 
I shall fit one to my big lathe, which is an Engineers Toolroom 1236, but I'll use a dedicated readout. The idea is fine I suspect, but in practise the hassle of constantly entering setup and rejigging, wouldn't for me, make swapping a viable exercise. Not as a normal occurrence. Its a pain going in, entering the correction for each scale in parts per million, sense/direction, beep on/off, diameter or radius etc.
 
I accept its not a long exercise, but it is a PITA every time you swap.
 
So I shall use two of the economy boxes.
Thread: Riveting
27/08/2009 22:01:46
I imagine they are probably, but tender sides are not so easy to get really neat, and you can't get a file in there to clean all up behind. Nor is there much room to swing a hammer.
 
Whereas a little squirt with an air gun on the end of a rod.....And prototypically, rivets were usually domed both sides I think? (Not on strakes of course - nice job BTW)
 
The strakes on my Little Samson I just pushed in firmly, and then weld filled the 1/8 holes from the strake side with a touch of MIG. Angle grinder with one of these soft discs and that was it. Nice and tidy job. Mind you the LS, unusually,uses cast wheels.
 
If I were doing it again I'd use the CSK rivets, but I'd just back them up agianst a chunk of something, and then air them in to get a neat dome. Its just so fast, and almost a one handed job.
27/08/2009 18:27:09
Jason I rather agree - you do have to set the rivet, or the plates.
 
Also, as a complete beginner to riveting, I found it a 3 handed job. If you hammer the rivet too hard, it deforms the plate and makes it curve, and it was very difficult to get the whole thing to start straight anyway.
 
I had a compressor - and a boilermaker at work said that professionally they used air, so why didn't I? I bought an air hammer, (Axminster £20) and then put the cup/domed shape into the end of the hammer bit (its fairly tough, but machinable and you can use a ball nosed slot drill with plenty of coolant).
 
Pop the rivet in, you secure the head in the snap located in a vice - that's the anvil. Set the air regulator to about 70psi (not too meaty), press the air hammer firmly agin the protruding rivet shank, and pull the trigger. 
 
1 second later, you have a perfect double domed rivet and no damage to surrounding metal.
 
The shank sticking through needs to be a smidgen longer than dia. So for a 1/8 rivet about 3/16 of shank does the job. Doing a traction engine tender, I now have various "sets". Nice short  2" one, a 6" long one and one nearly 13" long to get into the bottom of the tender tank. teh long ones are made from hardened silver steel, socketed into an air hammer base.
 
Very easy!
 
 I'll have a go at this countersunk version

Edited By meyrick griffith-jones on 27/08/2009 18:28:16

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