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: Parting off help!|
It is the lack of rake that makes life easy. I only use 4 deg (in the main) because I have toolholders that hold the blade at the optimal 4deg, so the top is ground flat and the toolholder does the rest. Grooving and everything else is done with zero rake.
Edited By mgj on 28/06/2021 11:00:54
Might be worth being careful how much rake you add - the more rake the more inwards force exerted by the cut there is, and the more prone to jamming.
Edited By mgj on 27/06/2021 23:51:08
|Thread: Master key - precision chuck.|
John - yes thank you. That is a very good old wheeze. I seem to remember reading it in The Amateurs Lathe by Sparey in around 1980 when I bought the lathe. Tubal Cain also mentioned it in some publication - perhaps the First Edition of the model Engineers handbook.
Thank you all. I have been away for a few days.
Old Mart thank you - that is exactly the faff I was on about. It isn't just about holding a single diameter bar. And indeed, on this chuck, the internal and external "best" sockets are different.
Jason - no. Mine doesn't have that zero on it.
Jason - yes. The jaws are marked, like that, but which socket, for the chuck key, refers to which jaw? So is no 3 socket left or right of no 3 jaw?
I have a Burnerd super precision chuck (not a Grip - Tru). It is just a precision 3 jaw.
|Thread: A Welding Problem - Steel Type?|
I did once have a problem with a SIP that was difficult to control.
Edited By mgj on 03/06/2021 12:49:58
Edited By mgj on 03/06/2021 12:51:50
|Thread: Spindle not running true|
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 ?|
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.
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
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|
Possible best to ring Dormer and get a definitive answer?
|Thread: Elephant Hawkmoth|
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.
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|
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.
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 20:38:08
Edited By mgj on 16/08/2012 20:43:54
|Thread: Frame Problem|
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 ...|
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|
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.
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