Here is a list of all the postings ANDY CAWLEY has made in our forums. Click on a thread name to jump to the thread.
|Thread: quickest way to bore a large hol using a lathe|
Oh yes, I find that by editing you can't change a post to have the email notification bit on, hence this post.
This is an experimental posting which I intended deleting.
I'm blessed if I can find out how to do what seems like a simple task.
I went to the Website FAQ and got lost in a thread about deleting threads which drifted into a long discussion about SHOUTING.
No surprise there then!
Despite a bit more trawling I could not find out how to delete one of my own postings. I did try deleting all of the text but when saved just left a blank postings.
Please can somebody advise?
Edited By ANDY CAWLEY on 17/05/2014 09:44:20
I thought that was a bloke looking through a pair of specs!
Thanks for that.
Hmmm! I just tried to add a photo and that didn't work either.
Edited By ANDY CAWLEY on 17/05/2014 06:06:00
Edited By ANDY CAWLEY on 17/05/2014 06:06:36
Tt the end of the first page of this thread is my take on trepanning. Although I have done it a few times now it still causes a fierce clenching of the buttocks when approaching the end of the operation.
How do I post a link properly?
Copy the url as you did then when typing your message, highlight a suitable word such as "this" then click on the icon of a world globe with chain Link, a window will open where you can paste the url
Edited By ANDY CAWLEY on 16/05/2014 09:51:55
Link and explaination added by Jason B
Edited By JasonB on 16/05/2014 10:27:01
|Thread: posting pictures|
Wow, that really goes against the grain but at least it will save time and frustration.
I'm using IOS 5.1.1
Does this mean I should not bother trying any more?
I created my album successfully on my PC.
How do I add photographs to it from my iPad?
When I go to the add photographs bit the "choose file" button is "greyed out"
What am I doing wrong?
Edited By ANDY CAWLEY on 26/03/2014 07:16:35
|Thread: dim tolerances|
Sorry about that . Clumsy writing on my part.
I thought I had explained, where I wrote about halfway down in brackets for the benefit of newcomers that clearance means "fit".
I was, in my way, trying to explain the difference between tolerance and fit. I should have added that negativeclearance is correctly described as an interference fit and no clearance at all, that is size on size, is a transition fit.
Edited By ANDY CAWLEY on 02/03/2014 09:37:18
There always seems to be a confusion amongst folk who are good with spanners etc. but who are not trained engineers about what is meant by tolerances. Most talk of tolerance when they mean clearance.
Tolerance is the range of dimension permissible on a completed part as specified on a drawing.
Clearance is the gap between two mating parts. It can be positive meaning the two parts can move against each other. Negative means that the two parts interfere with each other and are therefore locked against each other.
The larger the clearance the free-er the two parts are to move against each other. The greater the interference the tighter the two parts are locked together.
Given that tolerances are not generally shown on model engineering drawings then an understanding of the clearance between the two mating parts is the knowledge that the newcomer to metal work needs to learn. (For the benefit of new comers this clearance is known as the "fit" of two components.
In my opinion the most useful guide to this is in "The Model Engineers Hand Book by Tubal Cain" . (Page 5.18 is the grubbiest page in my working copy of the third edition plus I have copies of the page around my work areas.)
He lists 12 classes of fit and puts numbers to them making the allowance necessary for the relationship of clearance to diameter. He goes from shrink fit through to large clearance fit via drive, slide, close run and easy run to name a few.
When all is said and done for one off production such as in our projects our main object is for things to work and the way they work is down to the correct clearance.
|Thread: How do I stop old drawings curling up?|
Lots of lovely advice chaps, thank you.
However I suspect I have not really explained my immediate problem adequately.
It is well understood that old fashioned drawings are the best archive. That is what they are and will remain, well looked after. Old drawings are however fragile hence the plan to put them onto a disc
Somebody thought similarly in the past hence the copies on polyester. Electronic copies are however much easier to deal with, hence the new plan to put 'em on disc
Again the potential impermanence of stuff on disc is understood.
I am, however, as well as archiving them, working with them in the 21st century and as we all know a CAD drawing can be whizzed through cyberspace at the greatest convenience..
My immediate task is, a physical one, sorting the drawings into some sensible order and finding out which ones, if any, are missing.
What I neglected to mention is the fact that I have over 1000 drawings! I have a flat plan filing chest. I have a filing index that sorts into groups. The drawings are currently not filed entirely in index order or by group
So far reverse rolling looks like the best bet. Would raised temperature speed things up .
One of the problems of flat plan chests is leafing through the drawings to find the one you are looking for. My current idea (having flattened the beggars) is to interleave thm with brown Kraft paper with a filing tab on the edge to lead direct to the drawing of choice. As far as I can make out Kraft paper has a neutral pH.
Any views on this? Is there some thing commercially available to do this job for me?
Edited By ANDY CAWLEY on 25/07/2012 17:41:40
|Thread: Shell CY2 oil for Centec Vertical head|
Mine actually leaks from the sliding part of the quill. It's difficult to imagine how a seal could be put on this area due to the rack machined on one side.
|Thread: How do I stop old drawings curling up?|
I have the responsibility for procuring spares for a particular make of (pre-war) motor car. I am the current custodian for the old factory drawings dating between 1925 and 1939. They are drawn on a different types of paper and there are no standard sizes but they range between A4 and A0 but none of them are exact.
|Thread: Tempering Salts|
Oh dearie me David, now we are getting really confused. I was referring to your post of 19/07/2012 11:05:47'
.Never mind, this is not confusing:-
Done in the oven, no dangerous molten stuff, wife out at art appreciation, no damage, Austin 7 door now stays closed.
Thank's Terry for injecting common sense into my technorambling!
Whilst not as adventurous as dangerous molton salts you suggestion is far more sensible.
I'll give it a go!
Thanks for keeping my feet on the ground!
How I love the ability that we all have to mislead ourselves.
David is quite right in one respect, the OP was asking about where I would get a home workshop sized supply of salts that I could melt and hold at a temperature that would temper a piece of steel that had been through hardened by quenching either in an aqueous bath or an oil bath.
Pinched from Wiki :-
“ For metals, tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to a much lower temperature than was used for hardening. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product.” (I underlined the bit about temperature.)
I’m not sure David is right about Springbok’s confusion. To the best of my knowledge Cyanide baths for heat treatment are not aqueous but are molten salts usually at 800/900C and are used for case hardening where the salt increases the carbon content of the steel on the surface.
By way of clarification for some of the community I offer the following explaination:-
Steel is an alloy of Iron and Carbon in its simplest form.
Steel with a carbon content of above 0.40% (En8 in old speak or 1040 American speak) is capable of being hardened by heating to a temperature of around 850C and then quenching to reduce the temperature very rapidly. This makes the steel very hard but brittle. The brittleness can be reduced by tempering (see above).
In simple terms the higher the carbon content ( upto 1.0%) the harder the steel will be. This process is generally known as hardening and tempering..
Steel with a carbon content of less than 0.40% is known as mild steel and as such cannot be through hardened.
Case hardening of mild steel is a process by which mild steel can be given a very hard surface. This is done by increasing the carbon content at the surface of the steel and usually at very high temperatures then quenching. The high carbon bit of the steel at the surface then becomes very hard and the low carbon bit in the middle remains soft thus the component its self is tough in the middle.
The carbon enrichment of the surface is achieved by several methods whereby the steel is intimately surrounded by a compound which, when heated, to the magic temperature releases some of its carbon into the steel.
Summing up we can “through harden” for steel with sufficient carbon content and “case harden” steels with low carbon content.
This is a huge simplification (alloy steels have been ignored for instance) but I hope that it clarifies things a bit for those who are new to engineering and the influence of metallurgy on what we do.
For those on this forum, of which I expect are the majority, who are more knowledgeable than I, I beg your indulgence.
Pat thanks for that.
Somehow a container of molten salt at 200C seems less hazardous than a vat of boiling oil and less smelly as well When cold I guess there is less spill risk with the salt.
Gosh, Dick, sounds like a really cool(as my grand children would say) school. Cyanide eh? Now thats the way to teach.
It seems these days kids have to don safety glasses even if they use a compass to draw a circle, that is, of course, if they are allowed to handle something with a point on.
Harrumph rant over!!!
David, thanks for your caveats. I remember enough of my A Level Chemistry to be aware of some of the dangers. Since the range of temperature that tempering is done is 200C to 320C I’m not looking for a fearsome combination. Mixture 5, half and half sodium nitrate and sodium nitrite, looks like the one. With a melting point of 144C and a working range of 150/500C. Weed killer and food preservative sound like a really technical concotion!
What I am curious about is, will the letting down of a powerful oxidant like sodium nitrate with a stable sodium nitrite reduce some of it’s dangers?
I was rather tickled by Ian S C’s assertion that salt bath work is for the professional workshop. Most of what we do could be so classified.
I do however appreciate every ones concern. I actually picked up on the idea from Workshop Practice Series Number 1 in which Tubal Cain ( the real one) makes it all look perfectly feasible. Ive got a Belling Hot plate and a cast iron glue pot.
What could possibly go wrong?
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