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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: Turning Eccentics in Three Jaw Chick
06/11/2009 19:13:01
Yes, and its a nightmare to write up on a computer.
 
page 13.12 of the Model Engineers Handbook - 3rd edition.
 
Or use a 4 jaw.

Thread: Overheating grinder
06/11/2009 19:05:02
Peter - with your wheels.
 
I hope I'm not teaching Granny, but for sharpening up wheels a star dresser is good and cheap. Might appeal to your supposed Yorkshire nature.
 
(On which note the lads from my regiment 13/18 Royal Hussars (QMO) all came from S Yorks - indeed my first tank crew almost all came from the same street in Doncaster. I didn't notice them being particularly close walleted - well not when it came to going down the pub anyway)
 
Better I think is a flat diamond dresser because that will true up a stone as well as revive it. A single diamond is also pretty good and not expensive (we are not talking the Cullinan stone here) , but it really needs to be guided to remove grooves rather than put them in.
 
I'm still on my original wheels.
Thread: Compressed air on lathe
06/11/2009 18:29:57
There are 2 points about all these mist spray cooling systems.
 
1. The liquid in whatever form provides some form of lubrication, which assists finish.
2. The cooling depends not simply on the passage of the mist at a lower temperature, but  mostly in fact on the latent heat of evaporation of  the liquid, even in droplet form.
 
So they are not dependent solely on temperature difference, and the latent heat bit dramatically imporves energy absorbtion.
Thread: Keneddy hacksaw
05/11/2009 22:33:52
You could try the link at the top of the page?
 
www.v-belt.eu
 
They seem to produce lots of belts with no minimum order.
Thread: Overheating grinder
05/11/2009 20:15:39
I bet the rest of the job is just fine Peter.
 
I admire you for your economy and versatility. I think I'd have just machined up a bit of silver steel and done the easy solution. Less ouch hot fingers.
 
One cat and many skins.
Thread: Drive pulley wheels and V belts
05/11/2009 18:29:33
Sometimes it helps if you take your socks off. Stops one running out of counters.
 
Don't forget to use the effective diameter and not the actual diameter. Sorry about grannies if that applies.
Thread: "Precision" or "does NOT do what it says on the tin"
05/11/2009 18:22:54
No, I can see, if you have all your collets to one size, then it should be a once only adjustment. Wrongly, I had this idea that you'd be making adjustments for several collets
 
I like collets to fit t more than 4 points, but that won't matter if the work is not too heavy. 
 
I'm also very keen on boring things in situ/in there own bearings if possible. 
 
Just different ways of looking at the problem.
Thread: Overheating grinder
05/11/2009 18:15:21
I think you are probably right - about the power bit. If the stone isn't all that sharp as well, it may well be doing the decent thing and be trying to cope with demand by drawing more amps over a long period.
 
The alternative is that with vent holes etc, it SHOULD have a fan (is there some sort of location for a press fit ali item?), but somehow it got forgotten.
 
Mine is called a NU TOOL 550 watt grinder running twin 8" wheels. Its a pretty aged Taiwanese machine. (15-20 years?) It has vents and there is a pressed ali fan in there.
 
Annealing - presumably you will have to harden and let down anyway, so that was just a thought. However, there are always many ways to skin a cat. My only concern, were I doing that kind of job, would be that I might locally destroy temper in grinding, so I would do the heat treatment bit - in which case the softening process might just as well be done before grinding?
Thread: ER25 Collets on the ML7
05/11/2009 18:00:48
Hang about gents. I had EXACTLY the issue that John mentioned on  my Myford spindle. A very small burr was raised and I couldn't find the error but faceplates etc all showed a definite but small wobble.
 
Sent hte spindle back to Myfords and the estimable Mr Parker, now I believe retired, diagnosed and fixed. Cost nothing but the postage. (typical Myford IMO)
 
So I would check the thread given the history. Get a facepalte or something relatively unworn and run it under a DTI. I would then face something, clock with a DTI, turn trhough 90 deg and reclock.
 
Then I'd look at the chuck, as described above.
 
A purpely personal opinion - I have on the Chinaman an ER32 collet chuck. Had to be backplate mounted. That is spot on. For the Myford I have an ER25 screw on collet chuck and that does show a tiny bit of run out. However, I have a Grip tru so for absolutely critical work, I use that. I should fix it, I know.
 
If I were doing it again, I'd do a proper backplate mount, and I'd bore and thread the backplate myself.
Thread: "Precision" or "does NOT do what it says on the tin"
04/11/2009 22:38:31
Chris - I don't have it quite in my mind how your system is going to work, but it seems very complex, when the problem seems to be limited to:
 
1. Too much clearance.
2 Potentially varying clearance.
 
The problem is that - as I hope I see it right  - by building in the ability/necessity to adjust - you are losing some of the convenience of collets. True running with no hassle. It becomes self defeating? 
 
If you are to maintain that ease of use, AND be VERY accurate then:
 
Tackling it AAF,  - the varying clearance.  You have to get the collets to a common size.
 
Then, having done that an internal sleeve, bored in situ becomes a good thing.
 
Best thing is to mark up how the assembly was set, so you always install it same way. This is like boring spindles in their own bearings, or always using the preferred key slot for a chuck.
 
I have ER collets. They are in general very accurate, but being compressible, sometimes, at the small size for that collet, trueness does take one or two attempts.
 
My view is that its better to be approximately right than exactly wrong, 
 
So my accuracy tier goes 3 jaw, collets and then 4 jaw/3jaw Griptru when I really really mean business.
 
Given how relatively little you paid for your set of collets, that might be an approach you may wish to consider? (Said he hinting heavily. )
 
(The Griptru is a great luxury - they are wonderfully expensive being made by Pratt and Burnerd. I bought mine along with various other goodies - like a screwcutting gearbox - from a place called Skilmans in Woolwich in 1984 when I bought the Myford. Skilmans had stopped being Myford agents a long time previously and I cleared their remaining stock at clearance prices. I feel no guilt. 
 
If I was going to buy another chuck now I would buy one of those extra precision 3 jaws by Bison, brand damn new. Keep it for high days and holidays. I wouldn't feel a lot of guilt about that either, not even for an 8" one for the Chinaman. I would merely thank my good fortune that I had one, and the bank manger for his kindness.) 
 
Not bad smilies these - even has a crinkly chip smile.

Edited By meyrick griffith-jones on 04/11/2009 22:50:35


Edited By meyrick griffith-jones on 04/11/2009 22:53:24

Thread: Overheating grinder
04/11/2009 19:54:24
No, I don't have a hot grinder. Not even a warm one!Even after prolonged use on tool steel. Not that that's  a lot of help.
 
Warm electrical smell. You are drawing too many amps somewhere and there will be a reason. If it runs for a long period, the probability is that there is nothing electrically wrong, though perhaps part of the winding could be shorting, or the capacitor start centrifugal switch is not disengaging. The capacitor can get a bit warm then!!!! Dirt internally, something in a bearing. Anything you can find that resists movement? Not a real amps/whole volts man I'm afraid.
 
Some of the highly rated drill motors will get warm, but I would imagine that bench grinder motors are unlikely to be so designed? 
 
This might be of use - you have softened the file first by annealing? Might speed up the metal removal rate. Won't fix the grinder though.
Thread: Drive pulley wheels and V belts
04/11/2009 18:35:07
Almost every bearing supplier should have a shedload.
 
Ashley Bearings in Poole do and so do Premier Power Products in Yeovil.
 
Almost every auto factors.
Thread: "Precision" or "does NOT do what it says on the tin"
04/11/2009 18:32:14
Chris - I think you have a couple of choices.
 
1. Send the whole lot back. You will need to check the spec for 5c collets to see whether they are out of spec BTW. Sometimes one can be unpleasantly surprised.
 
OTOH you are after a set of collets, and it would seem that the collets are OK, apart from this undersize caper.
 
I take the point about making all ones own kit - I did the same. Nothing to do with disposable income merely the desire to have stuff that was dead on. Hence the Quorn, Dore Westbury, Radcliffe topslide, GHT dividing head and various bits from Model Engineering Services. Plus tee nuts and various holding thingys for millsand all sorts. All are absolutely spot on and I mean made spot on. The problem is that many want to make models and not tools.
 
Now I buy tooling, because time is limited - my choice. I have never been let down by Chiwanese but I have always kept away from the real economy stuff.
 
As for quality second hand - well that's fine too. Except that one can be certain of 2 things - you don't know how it has been used, and you do know that someone didn't want it enough to get rid of it, for some reason. 
 
There are, it would appear, to be Pooh Traps either way.
 
 
Back to this collet system.
 
I don't think you are going to repair the collets, because there will be a pile to do.
 
2 So its down to repairing the chuck.
 
You can bore and sleeve to size in situ - very accurate.
 
Or you could get it metal sprayed and ground internally.
 
The problem is that every time you buy another 5C holder to increase flexibility, you know you will have the slackness to sort before it is usable.
 
 
For my money it goes back, and you buy Vertex kit (which IMO is a good compromise between cost and quality). Shell out the difference, and write off the lost weekend as bad hair days.
 
BTW there is a PM for you ref MEX

Edited By meyrick griffith-jones on 04/11/2009 18:37:10

Edited By meyrick griffith-jones on 04/11/2009 18:39:35

Thread: Starting out
03/11/2009 22:56:18
The local club is an excellent idea.
 
Its not just the help advice and "how someone else has done it" but you get a dose of the completions. 
 
2 1/2 years into a project like a loco, and getting anything to work can seem a long way away. YDMES does tea well, and has a club loco for the petrol heads to learn on, and you see completed models working to push you along. I find I need that.
 
Mine's going to run on air next weekend - it'll be like pressing the starter on a racing engine for the first time!!!!!! (Only its taken a lot longer to build)
Thread: where can i buy a bell punch?
02/11/2009 17:51:36
I rather agree.  (Keeping them aligned) The other alternative is a centre square from Chronos, though I think Axminster do one too. Not expensive, and a great deal surer for finding centre.
Thread: TIG welding sets
01/11/2009 22:54:52
Ian - MIG is dead easy.
 
1. Get the right gas for mild. You can use CO2 (cheap) but it spatters like mad. Best is Argoshield 5, an for light work, and Argoshield 10 (AP will do equivalents) for something else I can't remember.
 
2. If you can afford it get an arc operated face mask. Set up in the clear, and it darkens automatically. Helpful but not essential.
 
3. Must have- pair wire nippers.
 
 
So, connect earth, to trial bit of metal (clean and about 1/8" thick for a start.) Press trigger to check for wire feed - listen for gas (purge line). Nip wire off 1/4 - 3/8" from nozzle. with nippers to give nice sharp end for arc to strike on.
 
Set feed and amps  according to makers instructions - try welding. Basically if the wire stabs forwards and/or burns back in an intermittent action you should up the wire feed (or turn down the amps). ie its striking and burning back so the feed rate is not enough to maintain a continuous weld.
 
If the wire sticks into the weld hard then turn down the feed rate. Its coming in too fast.
 
You should get a steady frying bacon noise, and when you stop, you should get a small blob on the wire (rule of thumb). As with all things amps wire feed and your speed along the work are all interlinked, but its pretty accommodating. Most welders have a series of steps for amps, and so assuming you are in the right step or range, its easier to adjust feed.
 
 Experiment - its not that difficult.
 
 
Going for a decent weld, assuming you don't have a welder with a special start setting and a dwell for finish, which most of us don't.
 
 
Start a little way into the weld, come BACK, and then go forwards over your start. This ensures you have adequate penetration at the beginning of the weld. At the end, don't just stop. Dwell for a second or so, then shut off. Stops that dimple, which is not great technique.
 
 
Vertical down is a matter of getting settings right and it'll run perfect. Vertical up is little triangles.
 
Once you have had a go and can get the thing to run you can start moving the torch left and right to get leg lengths right as specified on  the drawing. 
 
Seemples. 
 
TIG will produce beautiful welds, and manganese bronze too. On ali and magnesium its the dogs. But you need to do a bit of practise or train under instruction. Its very easy to get it imperially wrong!!!! Especially in thin ali, or anything else thats hot short. And its going to cost a grand or better to get a good fully versatile set..
 

 

Edited By meyrick griffith-jones on 01/11/2009 22:59:17

Edited By meyrick griffith-jones on 01/11/2009 23:04:05

Thread: Case Hardening
01/11/2009 12:21:23
Forgive me, but I thought certain steels were not heat treatable so the ability or requirement to refine the core would depend on what the item was made of in the first place.
 
The 40 carbons, to use the old terminology, sure, but if its a low carbon mild, and especially a freecutting mild, one can certainly case harden, but refining the core might prove a tad more difficult? 
 
My metallurgy in that field was always a bit limited, but I think that is right?

Edited By meyrick griffith-jones on 01/11/2009 12:24:42

Thread: Starting out
01/11/2009 10:26:58
If I may suggest it, I doubt that gauge or size has much effect on machining - in principle at least, though some particular models can have features which make parts awkward to hold. 
 
Very often bigger is easier, simply because (so long as your equipment is of a size) everything is easier to hold, less likely to flex, holes are bigger, you can see what you are doing better, you are less likely to break taps etc.
 
Next point is that its not usually the machining that's difficult, its the bending, rolling, putting in joggles and the like that are more awkward in the larger sizes. 
 
So it might be wiser, if you have no machining experience, and may not be familiar with drawings etc, to kick of with something which makes for a shorter and less broad in scope project. Not much fun, if through inexperience, you buy expensive castings and find you have machined them  exquisitely - but wrong. A loco is quite an extensive project, and if its going to involve 100% OTJ training as well, it will be a while before things start to fit together, never mind coming close to completion in operating form.
 
Unless of course there is a club locally, or you have somone to ask for advice.
 
If on the other hand you are talking of buying a ready  machined kit which is basically a spanner job to assemble, then I think Polly models do them and quite possibly some others. (Maxitrack?) Castings you can buy in stages, but whether these loco kits come in sections I don't know.
Thread: Work positioning in the 4 jaw chuck
31/10/2009 23:58:28
Dave - you'll do that in a Boxford - easy.( unless your 4 jaw is unusually small)
 
Set it up true exactly as Jason has said in the external jaws (tap home firmly with soft face mallet - using a bit of brass shim to prevent marking?), and then if you're a bit worried about overall stability, centre drill first, and use a running centre.
 
It will be off centre/out of balance so don't go mad with the revs when you centre drill, but being ali it'll centre drill OK.
 
Hell a Myford will do a little job like that without blinking.
 
Given that ali likes to spin a bit quicker, you might think about setting it on the face plate (bolt it from behind, and then add some weight to balance. You could then run at a sensible speed with impunity. (They always say you shouldn't use change wheels for balance weights - but most people do) 
 
You will get it anodised before use?
Thread: Moore & Wright micrometers.
31/10/2009 11:25:22
I don't know whether anyone covets a digital micrometer, but, now would seem to be a good time to look at the M&W 201 series.  They are on promotion and going for about £76 rather than £150, plus the vodka and tonic of course.
 
Splash proof to IP something or other, metric/imperial switchable, reading to .00005" or  a micron if you use metric and absolute and inc reading.  Normal stuff. 
 
I think the promotion goes on till next April - check on the Moore and Wright website
 
No connection with any tool supplier, but I just got a very good deal on a 1-2" one which I'd wanted for ages.


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