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Member postings for David Colwill

Here is a list of all the postings David Colwill has made in our forums. Click on a thread name to jump to the thread.

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Thread: Safety Shoes
22/04/2011 02:03:03
Apparently steel toecap boots are not issued to Royal Navy submariners as the most common foot related accident is dropping torpedo's on feet which causes the toecap to slice off the toes. Navy surgeons decided that squashed toes are better than no toes and so stiff non toecap boots are issued. The moral of this is to first work out what you are going to drop on your toe and dress accordingly.
I was told about this second hand so cannot vouch for its accuracy but it certainly sounds convincing!
David.
 
Thread: Precision Tailstock Alignment
16/04/2011 06:25:47
   I do have a turner friend that aligns his tailstock by boring a hole the size of the barrel in a piece of scrap steel and setting so that it fits nicely when fed in this does take all of the above into account. There should be no problems with vertical alignment as this is usually very accurately machined. I'm not sure of the arrangement on an SC3 but I would be inclined to proceed slowly and methodically until you are sure where all the errors are.
   If you do have vertical errors one way of dealing with them would be to use one of the compounds like turcite which is used by machine builders to reduce friction on sliding surfaces and for what you are suggesting. There was an article about it in MEW but I can't remember when.
   Well good luck with it!
   Dave.

Edited By David Colwill on 16/04/2011 06:26:34

Thread: Things we should not do
26/03/2011 13:09:30
The trouble with trying to distil this kind of knowledge into a usable format is that it tends to read as a set of rules which then become hard to interpret as experienced engineers rightly question them. What could be perfectly safe for Fred with 30 years experience of it may be quite unsafe for Bill who has none.
I (in common with many of you) often have to do things which I have never done before with machines which aren't quite right for the job and tooling which is often made or adapted. I first start by trying to imagine all the things that could possibly go wrong. I have always done this and it wasn't until recently that I realised I'd been subconsciously doing 'risk assessments' . Having thought things through this far I can then take steps to minimise any danger to me and am aware of how things could go wrong. The main problem here is one of experience. A man who has worked on a lathe for 30 years is going to have a much better grasp of using a milling machine for the first time than someone who has never been in a workshop.
I think that 'things we shouldn't do' should be called 'things I shouldn't do' and that rather than a set of rules, a guide to thinking things through, where generic things like loose clothing, safety equipment, guarding etc can be applied or disregarded as it is felt necessary.
One of the great things about a forum like this is that one can ask about even the most obscure things and find someone who has done it / knows about it. Therefore if your level of experience is low in a certain area you should ask about the subject in question.
Finally I should mention that I have a little voice in my head (I know what you are thinking) it is the voice of my subconscious or instinct, call it what you will. I have learnt that ignoring it has been a precursor to most of the really stupid things that I have done. I now treat it with a great deal of respect. Many times I have looked at something and thought it was wrong or unsafe without quite realising why only later to think yes that was it. So if you feel really uncomfortable about doing something then try and work out why.
Sorry for the ramblings
Dave
Thread: Amateurs
23/03/2011 22:38:44
"many times there is only 1 way do do the job"

Well at least we know who to blame the death of engineering in this country on!

It's a shame that other countries found cheaper ways while we were p*****g about trying to do things properly!
 

Thread: VFD Drives
17/03/2011 22:18:02
If you choose to Earth the screen it is usual to earth only 1 end, normally the end nearest the incoming mains.
Thread: boxford 125 tlc
13/03/2011 09:50:50
I have never done a 125 but I have done an easiturn and a compact 5. Usually you can keep the spindle drive controller and motor. Keep the axis drive stepper motors but get rid of the stepper drivers (modern micro stepping drives are much better and smoother in my opinion ). Limit switches can be kept and if you have a tool changer it should be possible to make that work.
 
A rough list would be:-
1) Two micro stepping drives
2) A break out board (Has a socket that a printer lead or similar connects and terminals that allow you to connect the electronics to the PC.
3) A 0-10v spindle speed interface if not on the breakout board (this allows mach to change the spindle speed)
4) Wire, connectors and other bits and pieces of electrical hardware.
 
It isn't to difficult if you take each stage at a time and the end result is a much improved machine.

Apologies if I've forgotten anything (others will be sure to say) and good luck with the project. If you get stuck you can PM me.
 
Regards.
Dave
Thread: Craftsmanship
11/03/2011 11:07:48
Fantastic! Well worth watching.
Thread: Strange angle ?
09/03/2011 09:08:47
I have a type 13 DSG and the topslide / compound slide (delete as appropriate) did cause me several hours of head scratching until I finally worked it all out.
Thread: Made me chuckle
24/02/2011 12:53:46
Dare I mention Michael Caine's immortal line from the film Zulu 'Fire at Will'. He was the Zulu with 600 bullet holes in him!
22/02/2011 13:54:51
Keep them coming I may end up with enough for a book!
21/02/2011 13:05:54
While walking home in the rain today I walked past a bus stop which was being cleaned by a man from a contract cleaning company. What made me laugh was the sign he put out.......
'Caution wet floor'
Thread: drilling HSS
20/02/2011 23:32:29
When I did this I hung a weight off the drill handle and pottered around while it happened.

Edited By David Colwill on 20/02/2011 23:32:52

Thread: Denford CNC milling
19/02/2011 14:19:06
I have got two Denford machines a Triac and an Easiturn both of which have been converted to Mach 3. They are both great machines. I find that a combination of mach 3, a cad package and desk cnc (very cheap for it's functionality) enables me to machine most of the projects that I need to take on. Those that wish to write G code programs line by line can still do so with mach once a few dialect differences have been taken into account with the added advantage of being able to cut and paste code in a windows word processing package. When using the lathe I have found the wizards in mach are easy to use and do pretty much all that I need.
These conversions are so easy to do that almost anyone can do them. I have done 3 now the latest a bridgeport clone and have had no trouble with any of them. Complex things like the tool changer for the lathe and mill seem a little daunting but are in fact a question of sitting down and reading through the documentation and examples and working them out.
A company that I work for bought an 8 x 4 cnc router last year for in excess of £30k and I have yet to see it do anything that I couldn't do (in most cases easier) with mach.
If all this seems like a sales demo for them well so what! I think it's great. So my advice would be buy a machine convert it then if it goes wrong ( mine haven't in 5 years) then you will not be relying on a compay who may or may not still be in business to repair it, you will be able to do it yourself.
 
 
 

Thread: How do I replace the gaslift cartidge in my chair..
17/02/2011 20:45:57
I accidentally drilled into one once. What a mess!
Thread: Notes on CNC Milling of 316 Stainless Steel
15/02/2011 09:48:16
I have some of Cutwels alpha mills and never had satisfactory results with them. I had a job to do on my cnc and decided to work out the speeds and feeds properly. I used the kennametal calculators:-
http://www.kennametal.com/calculator/end_milling.jhtml
All of a sudden my previously useless cutters performed brilliantly.
The moral of this particular thread must be:-
If in doubt sacrifice a goat before you start!
Thread: pcb guillotine
10/02/2011 01:00:18
I have one of the warco 3 in 1 metalworkers with guillotine, bender and slip rolls. I mainly use it for cutting pcbs and it comes in handy for all sorts of other things as well! Mine is the 24 inch version. Well worth a look.
Hope this helps.
Dave
Thread: Backlash - Steppers, Toothed Belts & Ballscrews
28/01/2011 16:01:48
I have converted my bridgeport clone using ballscrews, steppers and toothed belts. I paid extra for double ballnuts which allowed me to reduce backlash to about .03mm (total including endfloat in the screws etc). The software is set to compensate for this.
My mill is fitted with a newall dro which allowed me to make comparisons between where the software (mach 3) thought the machine was and where the machine actually was. After running the machine for an hour the x axis was .02 out and the y .04 out. This is more than adequate for my purposes .
Thread: DIY Vacuum heat treatment oven
31/12/2010 15:59:09
I fed argo shield into my muffle oven for a job I did once and it worked ok. If you feed the gas in at a fairly high pressure to get rid of the air initially you can then turn the flow right down and maintain the shield. It didn't use that much gas overall.
Thread: Metal storage
29/12/2010 17:44:32
A difficult one this! If you find the answer let me know.
Thread: Merry Christmas from Model Engineer Magazine
25/12/2010 11:08:04
Merry Christmas all.
<< First < Prev 33 34 35 36 37 38 39 Next > Last >>
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