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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: Spindle not running true
30/03/2018 18:22:22

I'd agree with Jason - if it was OK before and you didn't brutalise anything when it was apart (includes misplacing shims and so forth), then I'd look at what has changed.

I would check the assembly very carefully, and I think I'd have a scout about to see if there is a blob of paint interfering with anything, or preventing some housing from closing up as it should.

I think it would be most unwise to start hacking at metal until you identify what is wrong.

 

Edited By mgj on 30/03/2018 18:22:43

Thread: Teflon Spray ?
08/09/2012 12:11:37

One of the reasons many of these products don't perfom as well as one might expect, and others seem to get them to work well, is because occasionally people don't think about what the material is doing and how it works. It is important to use them intelligently,

If you have a thin type penetrating oil which disperses water out of a crack. (WD, 3 in 1 and many others) thats grand, but the water hasn't gone away (as a matter of principle) Its simply moved elsewhere. Eventually the oil will float (depending on evaporation rates of the wateretc etc.)

So the trick, in watery conditions like the bore of a steam engine, or tools in a poly bag full of damp air, is to dry the water off and respray. (With say a loco, its easy - pump the stuff in, spin the wheels a few times, and then respray, and no risk of a cylinder full of heavy oil creating a hydraulic lock next time. )

------

Again, I think it most unwise to say what will or won't stick to what, not unless one actually knows the subject. The chemists these days really have their act together, and just because a material is ostensibly slippery, it doesn't mean to say that it won't stick to something, using electrical bonds and the like. For instance preservative greases can look the same as any other grease, but have very poor charactristics under load. Some oils can be very good at rejecting water, cling to surfaces but reject small particles, and not be made of "oil" at all, but for example glycol.

So generalisations can be - misguided or possibly just out of date.

08/09/2012 09:20:27

Obviously your rust is different from mine. Keeps bores perfecty clean and stops rings sticking. But like all of the lighter low viscosity materials, its best if left alone and not rubbed off. Still if people don't like WD40, they would be better off using something else. At the end of the day, all that most of these oils do is provide a simple barier between oxygen and air.

If I wanted to keep tools and the like clear for extended periods then I'd use a proper ph controlled preservative grease like the military PX7. Or something really heavy like chainsaw oil because that really sticks and you will need white spirit degrese properly, but it isn't ph controlled.

 

Incidentally Geoff, I didn't think that an IC engines rings depended much on oil. A lot of IC engines have oil scraper rings precisely to remove (almost ) all of the oil from the bore. The advantage of WD40 in those circumstances is that it removes the old oil possibly - darned good thing - it will be acidic, and contain a fair proportion of fuel, (up to 10-15% by volume for a relatively unworn engine, more for an old design) and replace it with a fresh light preservative, which will stop them sticking. But of course one doesn't then want to turn the engine over.

 

What happens when you use the choke/ECU on start up, if the rich mix doesn't wash the bore clear, or nearly so?

Edited By mgj on 08/09/2012 09:21:04

07/09/2012 18:45:29

Well WD40 bonds at a molecular level with the substrate and displaces water. I use it squirting a blast into cylinders to prevent water rusting the bore. You know it will bond with hte base iron very aggressively.

But its not a lubricant as such, as Coal burner said. Teflon is,

 

Will WD40 prevent rust - very effectively, and for years. Obviously Because if a molecule has had its bonds taken up with a non oxidising agent, they are not available to be taken up by oxygen atoms.In principle at least. Thats pretty basic chemistry - and most oils don't work that way - they just coat (or that used to be true, less so now).

However before one says Teflon is this and something else is that, one wants to know what the properties of the carrier are. - since in general teflon will reprent a very small proportion of the total volume. So before saying the one stuff is better than another, one really wants to look at the tech spec, and see what it was made to do, and use it for that purpose.

Edited By mgj on 07/09/2012 18:46:56

Thread: Dormer drill bits
06/09/2012 17:02:16

Possible best to ring Dormer and get a definitive answer?

Thread: Elephant Hawkmoth
19/08/2012 09:05:55

Well as a failed humming bird hawk moth photo taker, I like it.

We always used to get the HBHMs on the valerian outside my window. Every year. Wonderful to watch them. But not this. They are susceptible to cold winters and we are on the limits of their range.

Hopefully next year.

Thread: Whistles
18/08/2012 22:15:12

I rather agree.

I have a couple of traction engine whistles in service. They are adjustable, in that the bell screws down for tuning.

You can set them on air, but they always require a bit of additional tweaking to get them working really well on steam. So if you are going to set a whistle on air, you need to be sure you have set it right in the middle of the range, because it can end up sounding pretty feeble on steam.

There was a good article on sizes and dimensions. The original was published as an SMEE article, but it then appeared in ME quite recently under the heading of "Wheezeless Whistles". It will contain all that one needs to build a good whistle.

Edited By mgj on 18/08/2012 22:15:47

Thread: Parting problems
16/08/2012 20:32:25

I'm sorry but it is simply not true that a rear mounted parting tool moves away from the load. That old chestnut has been around for years, and I am afraid that a lok at the vectors involved prove that is oversimplified and wrong If it was right the tool wouldn't jam up at the back - and it can.

Draw it up - its easy to see.

img.jpg

 

The force acts at right angles to the face of the tool - on the top rake.So it has 2 components - some downwards(at the front) and critcally, some inwards Put that point above centre at the rear and you create a situation where you have an inwards force pulling into thinner material if things go wrong so its tending to unload. Put the tool below centre then you have an inwards force digging into thicker metal.

Do the same drawing from the front, and you can see the forces are the other way around but otherwise identical. And you would expect that since the tool and the job have no idea where they are.

What  is needed is an argument that explains how it jams both front and back, and why its less likely to jam at the back. And thats pretty simple, once you look at the mechanism.

Waht you have to do is take off the inwards force - take off the rake, you remove the inwards vector and it doesn't jam. Look at the commercial indexed tools and they are all almost zero or negative rake.

How does it work - You dig a tool into the material, you generate that inwards force, but the feed is greater than that inwards force so the tool is kept under control in the backlash gap - its jammed against the feed nut, and it cant move forwards. Reduce the feed, the cut is insantaneously identical, but that pressure is removed - it is now free to pull in, which it will in the backlash in the feed nut. Which is why most of the time these jam up occur when the operator is being careful

If you get rid of the rake and maintain a steady feed, you find that jam ups are a thing of the past. I have apile of tools and kept putting on rake, because it looked sharper. Bought about 10 different models to try to solve the jamming problem. The identical tools, reground don't jam any longer - no top rake. And I don't part off from t he back any longer. If anyone wants a genuine Myford rear parting toolpost they can have it. It is perfectly useless and offers no advantage. PM me!

 

Why doesn't it jam up at the back so much - less feednut backlash, because normally that face on the screw is only ever used to retract a tool under no load. But put enough rake on and it will jam at the back, and very easily - that I promise. Got that tee shirt.

 

BTW tools have to be straight etc as well - thats understood. As is the fact that tools must give vertical glearance. I do agree though that the Sandvik 2.5mm tool as fitted to the Kit Q Cut cuts better than the GTN2 fitted to the Glanze and others.  But not by much, and hte GTN is a lot cheaper and made by many people.

Edited By mgj on 16/08/2012 20:35:06img.jpg

Edited By mgj on 16/08/2012 20:38:08

Edited By mgj on 16/08/2012 20:43:54

Thread: Frame Problem
16/08/2012 16:45:47

I'd have thought he's entitled to an answer if one is available - after all thats why he posted the question. Still one continues to see the kind of warm and friendly attitude, allied to useful and accurate advice that persuades me to visit but rarely.

I wouldn't worry about the oil creeping - the paint isn't going to get into places, and longer term the oil in there might do good. I'd just give it a spray of oil personally and put it aside. I've used penetrating oil on the joints for good reasons. Then come the day, give it a good scrub with a brush in hot detergent and get it warm to dry. (If you are brave enough and use gloves, then very hot caustic is pretty good, but be careful - eye protection and all that stuff) Prime and top coat ASP

Priming at this stage - depends on how long you want to keep it, but most primers are porous. So there is a limitation there.

Edited By mgj on 16/08/2012 16:47:46

Thread: Turned items are not looking good ...
15/08/2012 22:10:53

I think I would look at the chuck as well. I don't think that has been mentioned, and if it has a bus pass, or not been looked after, the jaws may not be holding correctly.

Give the lathe a tune up (it probably deserves it), sharpen all and ensure you support the work properly too, with minimum overhang. But before despairing, mount a job in another chuck/collet/faceplate/4 jaw, and see. Culprit could easily be a dodgy 3 jaw.

Thread: Machinability of Drill-Rod
14/08/2012 19:18:01

Drill rod is what they call silver steel. So it will machine like any high carbon relativley high strength steel. Silver steel or gauge plate in the soft condition of course.

If you need to know precise details, then you'll need the ANSI spec for that grade which will only be a google search. If you don't know precisely which grade you have, then ask the supplier, and you can cross refence from there.

What were you going to use it for is the next question. Making tools - then probalby one ought to finish grind. If its for pegs and dowells any grade will do. If for driving pins, then case hardened mild will be an easier to machine and give a harder result.

Thread: Welding Gas
14/08/2012 17:12:10

Thanks for that - I have an Argoshield light bottle from BOC. I have had it for about 9 years, and its still well full. 9years at £120 a year....

I reckon I can get one of these little bottles, weld for 5 years and still show a retun on 1 years rental. That Argoshield in the BOC cylinder must be worth its weight in gold!!

Thread: Hardening gauge plate
11/08/2012 22:25:18

Agreed Graham.

 

But,- if you have to quench, one drops it in vertically to prevent bowing and keep it moving to prevent assymetric cooling..

Personally I'd use mild and case harden, for a couple of reasons.

1. Free cutting mild is a lot easier to cut than gauge plate

and while its not ideal for volume hardening,

2. The surface will still be much harder than tempered gauge plate and

3. Less prone to wearing the die by having a better surface finish

3. Stronger by being less prone to crack propagation

4. Its a lot easier to make a new die block after a few years, than a new expansion link.

For me I'm afraid its a bit like making driving pins out of silver steel. Sound like a good idea but metallurgically a little less than sound.

Edited By mgj on 11/08/2012 22:26:02

Thread: bending 4mm copper tubing
09/08/2012 21:43:29

Clive - 4mm rad in 4mm pipe is seriously tight. That will be an entertainment. I think you'll need the extra leverage of a bender to do that nicely.

There is a sort of ideal (typical) minimum dia/bend rad ratio. I have forgotten what it is, and someone may be able to help with that - but its not 1:1!!!!

Any way you can get away with it a bit wider than 1:1?

08/08/2012 23:08:15

I have a tube bender - Hemingway. Very good, but over complex for the task- but quite excellent in the slightly larger sizes of tube.

If i'm not telling my granny, the operational guts of the thing is a groove, just over 1/2 th dia of thee tube to be bent. That stops it going oval and collapsing. So a lot of my smaller tubes I bend by using a ball nose cutter on a rod of the required bend radius, of about 75% dia depth, and bend the annealed tube around that.

3/16 tube I like the sliding shoe of the bender, but less than that a thumb and a groove does as well!

Thread: Rocol Ultraglide, Does it work for you?
26/07/2012 19:45:14

I agree Kwil. You put me onto the X5 which is just the stuff in a tin. There is no doubt about it it - the cariage slides more easily when lubricated with Ultraglide, rather than SAE30. Its quite noticeable.

Thread: Safety Valve Advice
22/07/2012 08:31:36

If the valve has a wing type plunger, ie an area which sees steam in the boiler and a pop type ring which see steam escaped and provides a larger area, then probalby the area of the ring is too big. ie it lifts at a pressure, and then the increased area keeps it open to a much lower pressure.

The adjustment procedure is to get the valve to lift at the correct pressure- adjust spring compression/preload or rate until that is right. (using a gauge and the air compressor one will scrounge access to) At this stage don't worry about closing.

Once it lifts at the right pressure, then adjust the ring or the area between ring and wall, untill it closes at the right pressure.

I'm just doing exactly this for Metre Maid which has standard ball type safeties, and they buzz and fizz, so its getting new safeties of the pop type.

Google Ross type safeties.

Thread: Drilling a long way through steel.
18/07/2012 22:09:16

Gets a lot easier with a sharp , preferably 4 facet sharpened drill especialy for the pilot.

If you haven't got access to that, try buying a split point drill for the pilot - once you have a straight hole, the full size will follow it.

2" deep x 8mm. Wouldn't bother with a pilot on a mill - centre drill, lots of coolant and go with a 4 facet/split point. Just don't let the swarf build up (and jam the flutes) - that should keep even an ordinary drill pretty straight.

Why the split point/4 facet geometry - because it has a point on the tip rather than a chisel edge which tends to stop the drill from wandering.

Edited By mgj on 18/07/2012 22:09:40

Thread: How accurate is your lathe?
16/07/2012 12:14:00

Are we sure we are not getting confused between repeatability/concenetricity of the chuck, and paralellism/leveling/lack of taper in the bed.

Surely, if you turn a bar in a lathe, even if it is held eccentrically, the result will be a dead true piece, radially, even if it is axially tapered. If then there is a detectable error that is not due to surface imperfections, there is likely to be a problem with bearings, looseness in slides, chuck gripping etc.

If the piece is truly round, but but tapered, then the dumb bell test (leveling, twist - call it what you will) hasn't been done properly, or there is some sort of fault in that direction.

But the two are not the same, and in general terms don't cross reference.

The whole drift of this thread has not in fact been about lathe accuracy, but chuck accuracy, which again, are not the same thing at all. For one to think that a 3 jaw is OK at .001 runout....... They are only built to about .003. You can get an ordinary 3 jaw which meets then normal DIN standard for a very reasonable price. A top grade 3 chuck guaranteed to hold to .001 or less is about £4-500 plus vat in our sizes, and going up, and it will stil only hold to that on one nominated master pinion. Unless one is lucky and you happen on a good one.

.001" when new is darned good for a slef centring 3 jaw. No one ever bought an SC three jaw for accuracy did they? Only for convnienece?

16/07/2012 09:35:34

I think I might remember the jaw/pinion number that produced that. A standard SC chuck in good nick by Pratt & Burnerd will only hold concentric to about 3 thou.

A Super Precision SC 3 jaw from Pratt will be under a thou one one jaw only, but with both sets of jaws. It will however vary pinion to pinion with diameter (according to the bit of paper it comes with), so to get the best out of it one needs those test results handy.

So one thou with an ordinary 3 jaw is pretty good. Might also be wise not to abuse it, thopugh up to a point the accuracy of the chuck is not relevant. If something has to be genuinely concentric than one will set up in a 4 jaw, or if using a 3 jaw, you'd turn to size Personally I'd never put something in either a 3 jaw, or even collets and assume it was true without clocking it. A Griptru is handy though. Its a bit quicker to adjust than a 4 jaw.. So on reflection, my super precion 6" for the big lathe was, in hindsight a waste of the extra dosh - it does have hardened slides, sure, but for amateurs like us thats hadly a consideration.

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