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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: Drilling problem - the sequel.
30/10/2009 14:06:57
One 4 facet sharpened drill with a little diamond lap about to "blunt" the cutting edge -AKA  zero rake. don't go mad- a couple of strokes is plenty, one is usually fine.
Actually it needs resharpening, but since it still cuts better than a new drill it can wait!!!


Edited By meyrick griffith-jones on 30/10/2009 14:07:34

Edited By meyrick griffith-jones on 30/10/2009 14:08:48

Thread: TIG welding sets
30/10/2009 13:41:47
I don't know what your welding experience is.....
Well as always, what are you going to weld.
Some materials require the electrode positive, some negative. 
You will have to change your gas of course, and you have to know your settings, same as for anything else..
Honestly, I'm very surprised to hear you say that MIG is difficult. MIG with the right wire matched to your card, and using Argoshield  (Argon Oxygen mix) is about a simple as point and squirt for mild steel. But you do have to set amps and feed rate and the two are interlinked.
I don't know whether you have done gas, but TIG is only electric gas - you are dipping and touching and adjusting heat settings just the same.  TIG is not suitable for thicker sections, and while in the hands of a good man it produces very neat welds, in the hands of the inexperienced or a barbarian it produces rubbish.  Position welds - vertical up down and inverted are MUCH easier with MIG.
MIG is normally faster with higher metal recovery rates too, and very often less heat input, (depending on how its used). 
Are you sure you have given MIG an adequate trial? For most who want to weld mild in average conditions, MIG with Argoshield is difficult to beat for speed and ease of use. I would have thought that someone who had difficulty setting up MIG would not take to TIG very quickly. TIG is a bit of an art to get right. 
As Ian says, a sensible TIG set which you will need if you want ot go to 6mm plate of any size,  (or even an HF unit to go on a MMA box) is quite expensive.
 An HF unit might be worth looking at, because then you get an stick welder which is more suited to thicker plate, and the TIG for thinner stuff which it is better at. Some HF units are not suitable for the alis and light alloys of this world. Its not that there is anyhting wrong with them for steel - they just don't provide the right condions at the electrode for the light alloys.

Edited By meyrick griffith-jones on 30/10/2009 13:43:12

Thread: Riveting
28/10/2009 22:39:08
Well that's when the fun starts- trying to hold the plates, and the second snap, and the hammer, and trying to keep all square so the second snap doesn't skid off and the head starts central because if it doesn't......
In my somewhat limited experience double headed riveting was somewhat easier in theory than in practise, but I'm quite willing to accept that I may have missed a trick somewhere along the line.. .
Shortening - set the rivet with a plate of the right thickness, with an allowance for the excess left by a pair of small bolt croppers. Hold all steady and zap with an air hammer which has the dome cut in the tool. 1 second: perfect double round head rivet.
Air hammer - £20 from Axminster - No I don't - wish I did
Thread: oil
28/10/2009 18:10:31
OM 13 - so did we. Nice light, additive free hydraulic oil.
If you were a Myford owner at the time you should have taken some home!.
Some of those oils were really quite special - like the winter specials for ACE mobile force north of the arctic circle or the Challenger gearboxbox oil.  Some of the specs were just written around a commonly available and suitable oil like bog standard 20/50 multigrade for  engines in temperate zones, or "ordinary"  hydraulics, and what you actually got depended on who  had that contract. Shell, Esso Castrol etc.
I always thought they were military specials, but I learned otherwise when policing some of those contracts in DQA. 
27/10/2009 18:37:31
Allen  -
Frankly if you aren't going to use the lathe then you are most unwise to just leave it. You wipe it down, get rid of all the soluble oil tarnish, which is a feature of some of the soluble oils like Rocol (which the detergents in motor oil are quite superb at doing) and then coat it specifically with a preservative  oil.
If I may actually quote from my Myford manual "Where oil of viscosity SAE30 is specified any good motor oil of this number will be satisfactory".
Detergent oil was certainly around when that was written in the 80s, because the bulk drums of  oil for military vehicles were all maked Burmah Castrol, Shell etc, then all the multigrade spec - to spec OMD110. And OMD stands for Oil Mineral Detergent. And I didn't notice stuff wiped with that rusting too much  - not even in the tropic!. Nor when acidic oils  have been left in car sumps, or externally on steel parts, does there appear to be much degradation after long periods at the scrapppys -(for those who were into F750 racing.)
 I mean, its not like one is applying Fairy Liquid!! FFS - the detergent is designed to stop clumping and to carry away carbon and maintain an even high cling film Not for washing up in. Isn't it a bit alkaline, which is a bit of a bonus? When rusting is generally an electolytic reaction between dissimilar metals ( at the microscopic leve) in an acid environment?
I can only express extreme astonishment that My Super 7 B, given the abuse caused by the almost sole use of SAE 30 oil,   despite having been laid up in a damp shed for a while when we moved house, has after 24 years or so, still not managed to rust.  (nor wear either)
Perhaps it will get round to it.
if you felt charitable, you could always post me that can of SAE 30. I'm sure I could find a use for it.
26/10/2009 23:54:08
Indeed it does- I knew there was a reason to use SAE 30 oil.  If you look at the lubrication chart, it recommends SAE 30 motor oil for a whole chunk of bits. (VG68 as an alternative - whatever that is!)
I feel really good about that. No wonder my lathe has lasted so well!
26/10/2009 18:24:05
 I'm with David on this. 20/50 is very thick and it isn't going to get hot enough to thin. Also I don't fancy paying for all the additives and carbon  carriers and fuel dispersants and multigrading when they aren't necessary.. We need something quite bit thinner, and SAE 30 is about as thick as youd want ot go.
The army uses Esso Nuto in gun buffers and for oiling main armaments on tanks. Its not much thicker than 3 in 1. It is in fact, but you know what I mean.
I did use 20/50 and I had oil starvation on the headstock bearing - though mine is pretty closely adjusted. That may have a "bearing".  (awful pun)
So SAE 30 does for everything, as being a good medium grade oil, without additives desined for IC engines, because it is such a good clingy oil and does the bedways so well. A plain 5W or 10W would probalby be better. Still the machine has lasted from 1984 without self destructing, so 30 it is!!
For preservation I think I'd use horticultural chainsaw chain oil. That really sticks! (and no additives)
Thread: Help
25/10/2009 00:40:47

Rob, I think that most people would say you need a 6" lathe for a 4" engine. That means a 6" gap bed.
I know Jason says that LS is not massive- and he is right, it isn't. Even so when you go to the Dorset Steam Fair and other places, I'd describe the LS as a compact 3"  engine rather than a big 2" one. Its a whisker under 4 feet long. So you have some fairly chunky bits to machine. You certainly need, for the 3", a bigger lathe than a Myford - subject to Jasons very valid points - but don't forget you need to mill. And the Myford/3 1/2"  will not do that for you.
This is mine - I have got rather further with all the valve gear and cylinder complete, but it gives an idea of size against the table and door.

Give you an example - the cylinder block. On a 3 1/2" lathe you are going to have to pack it up, and then bore between centres, and then fiddle around to face the end of the block. Then you have to face the other end, and then cut on a 3" radius, the curve on the block to fit the boiler, and I don't think you can get that on the Myford saddle. Its just too big for the centre height.
On a 6" lathe----- just pop it in the 4 jaw, bore the cylinder face this end for the cover, and square the mount face. . You now have a datum to turn it round and face the other end. And then you can do the steam chest. - ain't going to get that on a vertical slide!!!!..

This is the same block being rotary milled for insulation - the table is from Ivan Law (MES) - home built, as is the DW mill of course..

This is the second motion gear being cut on a GHT head - that is centre height for a 3 1/2" lathe. Even on a mill. I had to hang it off the back of the table, use the head for indexing and a clamp to put the thrust into the table.
This is going back to the start - boring the smokebox, which is 6 1/2" od.
Turning the front wheels in the Myford, before I got the Chinaman. They just fit for diameter - but the overhang is such that you cannot turn it round to face the other side for the hub caps - though you could do it in a mill. Hadn't got an indexable TCT tipped tool with enough length either. (Stil don't)

This is just indexing something or other. Same home made GHT head
Now - with bigger machinery, life is a lot easier.

Edited By meyrick griffith-jones on 25/10/2009 01:06:38

Edited By meyrick griffith-jones on 25/10/2009 01:07:49

Thread: Drilling problem - the sequel.
23/10/2009 16:48:17
Yes- is that a pickup?
23/10/2009 14:22:04
Its not blunt - it has zero rake.  I don't mean a mankey chipped old thing. Personally mine are razor sharp 4 facet sharpened drills - a lot sharper than they are when brand new.But they are properly configured for brass - and when finished, they are cleaned up on the lips to put them back into steel mode. I suppose I should have 2 sets, but its too expensive.
I agree about feed rate - the tendency is to feed as one would with steel. In fact to stop grabbing, as you suggest you increase the feed. Basically you push it faster than it can cut, so all the backlash is taken up, and kept taken up so it cannot pull forwards. So I lean on the thing pretty firmly and drive it pretty hard.
Yes you do have to resharpen because you are converting from one tip geometry to another.
However, everyone is trying to dance round the problem which is terribly terribly simple: a drill or lathe tool ground for the brasses and bronzes is not suitable for steel, and vice versa. The characteristics of the metals are different . Lathe tools with low rake angles will work. Drills, which have higher rake angles make the point for you - sometimes quite forcibly.
Tools for the job, and those who don't know about rake angles and grabbing etc - learn or otherwise find out, (Ian Bradleys book for a start) because brass and gunmetal are our stocks in trade, and not knowing will cost castings, time and grief.
 Myfords not being up to it? 
Depends on diameter and I'm not up to industrial rates of course, but doing 1" ID bearings for a traction engine in bronze -  lots of coolant to contol binding from expansion,  centre drill, 1/8 pilot, 4.5mm gun drill (needs initial stabilisation because of the length) all at top speed. , 3/4" 2mt (biggest 2MT drill I have) at 1000rpm. Bore to -.005" and ream to size. Nothing grabs, nothing jams. Why should it? I have my tips sorted.
With respect - the Myford takes it just fine. A 1/8 bit can grab in the 6" lathe, which weighs God knows what and is as solid as the rock of Gibraltar. Is that not up to drilling a 1/8" hole in bronze?


Edited By meyrick griffith-jones on 23/10/2009 14:22:36

23/10/2009 12:17:54
Yes, or in model engineering sizes you can use a 3MT- the leverage of the larger diameter.... but all that is curing the symptom not the disease IMO.
Best have it not grab and cut straight an not oversize etc because  you are still getting the tip flexing and the like which are causing the forces which cause the grab.  Its going to show somewhere - like the drill spin in the chuck and score the shank. There being no such thing as a free lunch.
Another "fix" is to cure the backlash in the tailstock quill- because thats whats allowing the thing to jump forwards. I think we have heard of this just recently........ Its still symptom not disease, but it does help. As will INCREASING the feed rate of course.
23/10/2009 04:19:07
I think you'll find that if you go to zero rake, you'll be able to drill at a good speed, without having to lock quills and other bodgery.

if Robin, you don't quite follow, just blunt the cutting edges with fine stone. So the cutting face is a little wall. Don't go mad, just take the edge off the drill with a couple of wipes of a stone.
Thread: oil
23/10/2009 04:14:05
Oil - my Myford manual says  Esso Nuto H32 which replaces H44. Possibly there is something newer and better since.
I use SAE 30 horticultural engine oil, which is a non multigrade, no additive, not too thick oil, with good cling capabilities which copes with headstock bearings being  pretty closely adjusted. The lathe seems to have lasted 23 or so years from new without appreciable wear, 
If there are better suggestions, I'm very willing to take advice.
You need to buy Ian Bradleys book on the Myford. It isn't just a manual, its a how to do almost everything on a lathe. It would be an investment.

Edited By meyrick griffith-jones on 23/10/2009 04:14:25

Thread: Grinding hss
22/10/2009 14:31:21
Michael - don't worry about what it's "suitable for", because your toolholder may not be the same as his.
Measure from centre height to the lowest edge of the tool holder (in its lowest position if you use a Quick Change type), and that will tell you the one for you.
I use 12mm tooling on my 6" lathe and thats perfect for me, but my toolholder may be differnt from yours..
Just to damp Chris firework slightly, I can take a 250 thou cut on radius on a Myford at 600RPM, on a standard tool  ...... its just the hot fingers and rough grinding it takes to get there thats the PITA. 

Edited By meyrick griffith-jones on 22/10/2009 14:34:10

22/10/2009 10:37:49
I agree about setting up a grinding wheel - one does HAVE to use the correct spacer and discs. And the grinder wants to be in reasonable nick too - and be bolted down.
I must admit I am quite keen on face protection.
 I once picked up a single spark from an angle grinder. I was wearing goggles, so this spark had to have come off the wheel, hit my cheek, bounced under the goggles, hit the back face of the goggles and then bounced back again into my eye. Uncomfortable session later in the Addenbrookes and all was OK , but these things have a surprising aount of energy, in certain circumstances.
Also the big face jobs don't mist up!
Too simple - of course. Very obviously its an excellent device. Wish I'd heard about them earlier, because then I wouldn't have struggled to build the Quorn accurately.  - chickens and eggs.

Edited By meyrick griffith-jones on 22/10/2009 10:39:30

21/10/2009 22:48:58
Yes - I rather prefer those full face masks for anything like that. One can see rather better!
I have a couple, one hangs up by the Quorn and one by the grinder, and I even use it when I am polishing.
Thread: Lathe Backgear
21/10/2009 18:52:57
It may be we are pushing this screw cutting thing a bit far?
The advantage of screwcutting a thread is really that one can guarantee it is straight. Mostly the pitches we cut taps and dies are in fact available. So a compromise solution may be to singlepoint screwcut (by hand) to a few cuts to make a start, and then use a die to finish- because the die or tap will naturally follow .
Yes, one is losing some flexibility, but its like all of these things -  90% of the result for 50% of the cost?
I'm alright on this one, because both machines have proper screwcutting gearboxes and a good range of feeds - but then I don't have the space problem that many have.
The only thing thats really important in this discussion is that people go into the showroom with their eyes open, and they understand the tradeoffs?
Jason - I shall make a tap. Good idea. Years ago I built a Quorn. I have never used it to a fraction of its capabilities, so it needs a surprise. I shall screwcut some silver steel and then make a tap. That'l be a good evenings exercise, and 2x the satisfaction deforming a bit of bronze.

Edited By meyrick griffith-jones on 21/10/2009 18:54:37

Thread: Grinding hss
21/10/2009 18:34:40
The one of grinding HSS which always puzzles me is the advice never to dip it in water to cool it. This apparently introduces cracksNwhich can lead to all sorts of dire things.
not in my workshop is all I can say. Nowadays I do keep it cool by dobbing it with a wet paintbrush when clear of the wheel, right from the start. In the past I've dunked it when it was blue with heat. 
I'm sure that is all wrong, but I speak as I find. (I have only ever ground Eclipse, Sandvik or Cleveland bits. Once some chaep imported stuff and that is in the trash can)
I think Chris advice is very sound. He and I have a habit of agreeing far too often.

The tangential thingy looks excelelnt - no experience unfortunately. The only problem is that its too simple to sharpen and one might just live with sharpening that and leaving other bits - and one does need to be able to tackle them - screwutting tools, speciaist grooving tools drill bits and all sorts.

So to back Chris, get Harold Halls book and get building a rest for an ordinary grinder. Even if you are a tipped man, and I am now, it will still be enormously useful - not least because if you have a green grit wheel you can sharpen all the blunt tips!. 

Perhaps I'm braver than Chris about grinding.  If one fits the wheel with a proper arbor and spacer and uses the soft packing washers and cup washers on a wheel of KNOWN PROVENANCE one should be OK. First thing is to dress it properly and second thing is to remember that .001" is a very big cut grinding. However caution and goggles are good things. 

As for using carbide - I must say that I've read all the stuff about speeds and feeds, and it is, no doubt, very sound. I just use it exactly as I would HSS - never changed coolant either, just 20:1 dilute soluble oil for everything from cast iron to titanium. I have never had anything other than good results on a 6" Chinaman and a Super7B. However, I have never used cheap tips, and I have never used cheap tools. It is just that last time someone had an agony about finish with tips, it turned out that the tools were not giving him clearance
Thread: Lathe Backgear
20/10/2009 21:44:10
Yes - can and have with a tailstock die holder. Prefer to do it mandraulically, partly to break the chip, and partly because all my dies and taps are CS. Harder and last longer but I'm wary of localised heat build up at the tips.
Probably under power it would be better, but I'm just used to doing it the other way.
Love threadcutting though. The LS brake mech calls for a square thread, so I'm looking forwards to doing the actuating arm and nut for that. (And not cheating!).

Edited By meyrick griffith-jones on 20/10/2009 21:44:51

Thread: Help
20/10/2009 17:58:29
Thanks. I bought a 6" Chinaman, and actually was quite glad of it, even with a 3" LS. Wheels of course, but even so mandrels for putting cylinder bores on and the like - its nice not to have a parting off game before you start. 

Talking to the gents down at the club, in terms of "relative expectation" I think TEs tend to need bigger lathes than locos. Mills OTOH seem more stretchable.

Edited By meyrick griffith-jones on 20/10/2009 17:59:27

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