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Member postings for pgk pgk

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

Thread: What did you do today (2015)
15/01/2015 22:51:24

My mill got delivered today and I got lucky between showers getting it into the shed. It wasn't easy - a tad tight with the threshold step and these things are top heavy so some creative roping needed...

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Thread: Forgotten engineering techniques
15/01/2015 07:38:51
Posted by Michael Gilligan on 15/01/2015 07:31:26:
Posted by pgk pgk on 15/01/2015 07:10:48:

That's an extract from a BBC documentary

.

... so it must be true devil

Do I detect a hint of sarcasm? I'd actually come across the technique of the drafting floor in past general reading and grabbed that bbc quote to save typing. Remember paper was an expensive commodity. Heck it;s not that long ago kids used slates at school - also could be referred to as working from scratch.

Thread: What is the best way to mask off circles prior to painting with an airbrush ?
15/01/2015 07:26:46

Never used it for this application but you can buy masking fluids from any art shop when doing water colour washes or any hard edge technique with acryllics. Paint on.

I hate decorating so i buy a cheap low tack blue paper masking tape from a (scottish) auto detailing co on-line and can spend a few hours masking up architraves, skirtings etc and then dosh out emulsion with a wide brush and roller - avoid all the stress (and care) of cutting in. Walls and ceilings only ever get done in white (cheap, clean and in huge tubs). Woodwork is stained or varnished (never painted). A whole room gets done in a day and the tape comes off without marking the underneath or lifting it.For hard edge spray lines on heli canopies I've used the plastic 3M masking tape

Thread: Boiler Insulation
15/01/2015 07:14:48
Posted by Brian John on 15/01/2015 05:12:08:

I was looking in the wrong places : the pottery and ceramic supply shops have ceramic fibre sheets which is 2mm thick X 610mm wide and $20 per metre. It is rated at 1260 degrees Celsius.

What do they use it for ?

I use them as a gasket for the access port of my woodburner flue for sweeping and gaskets around the woodburner door glass.

Thread: Forgotten engineering techniques
15/01/2015 07:10:48

Sometimes folk look too deep for an answer.

'Building from scratch'

<<the skill of the medieval mason. ... for the building were worked out at full scale on tracing floors covered in soft plaster. ... and at Worcester a carving shows a mason giving a drawing to a monk.>>

That's an extract from a BBC documentary on medieival stonemasons. Literally scratching the designs out for a building on the drafting floor. And you can bet they made concept sketches and scale drawings beforehand. I's also a darn good bet that they made concept models. At one time i took an interest in Windmills. No way do you go building something with baulks of timber that huge without a model or two to show it's going to work.

As for fettle. Often a guess,.. but make something fit you can fiddle, file, fatten , wattle and caulk and have the mettle to keep twiddling and tweaking....

Thread: digital calipers
13/01/2015 22:18:28

It's only a fair test and criticism if you repeat the experiment with your mitutoyo's. Of course if they creep....

Thread: Popcorn Popper to roast coffee beans
12/01/2015 16:33:29

When I was a kid there was a coffee shop that roasted. A simple set of half a dozen brass coloured horizontal cylinders with a bearing rod at one end and a gear at the other all rotated by a chain drive above a set of gas jets. The only adjustent being the flame height. Nice , simple basic stuff and super aroma.

Thread: Festive Port Pourer
12/01/2015 12:55:29

You can buy cheap flexible graspers.. spiral wound stainless with 3-4 sprung tines down the centre activated with a spring plunger. Before the advent of modern endoscapes and their tiny flexible camera versions we used to fish foreign objects out of patients by feel and luck.

Camera based endoscopy obviously makes that a much more reliable and fun game albeit at a heck of a cost with a whole slew of alternative grasper types and baskets and bags as well as ultrasonic probes and laser fibres - particulalry fun when frying and cracking bladder stones the long route...

Thread: Forgotten engineering techniques
12/01/2015 10:25:59

According to legend the London to Croydon vacuum railway use leather and tallow to seal the horizontal strip of the vacuum pipe that pulled the train. When the Croydon Pumping station was fired up in the morning then all the rats that had been chewing on the seal were sucked in .. and it rained rats over Croydon for the next half hour...

11/01/2015 23:49:24

Talcum powder is still talcum powder/

Fom wikepaedia

The studies reference, by subject: pulmonary issues,[11] lung cancer,[12][13] and ovarian cancer.[14] One of these, published in 1993, was a US National Toxicology Program report, which found that cosmetic grade talc containing no asbestos-like fibres was correlated with tumour formation in rats (animal testing) forced to inhale talc for 6 hours a day, five days a week over at least 113 weeks.[12] A 1971 paper found particles of talc embedded in 75% of the ovarian tumors studied.[15] Recent research questions if a link does actually exist between the two. [16] [17]

From searches on talc BP

(pharmacuetical grade) shows several compnaies producing purified takc for that sector

pgk

Thread: tolerances
07/01/2015 21:41:10

Points well made, chaps. There's a lot for a newbie to learn and remember. Perhaps next time I'll dig out my honing paste and leather wheel as well

07/01/2015 20:48:44

Ah! That makes sense.. thanks.

07/01/2015 18:55:33

But the thing ended up too thin. Surely spring passes are there to effectively 'get it thinner to size'.

This was also a 12mm tool bit ground for facing that hadn't done more than a few inches of surface distance since ground and honed and here was being used on the ack edge of it's radius 'cos I'd angled it to get into the shoulder. While I'm new at tool grinding the cutting edge used was effectively new. The swarf was bum-fluff anyway on such thin passes.

Unless it dug iself in a tad on the 0.005mm?

Thread: What did you do today (2015)
07/01/2015 15:31:30

I'm feeling a bit chuffed. Just had a go at my first thread-cutting having finally modded stuff so i could get the right changewheels in. I chose an M16 cos it's the largest commercial nut I have lying around and my practice steel bar is 1.24 inches and I've been turning a section down for practice anyway. The nut fits as well as it does on the commercial bolt!!

Thread: tolerances
07/01/2015 14:41:17

Correction. I hadn't misread the DI...(dumbo beginners!).. It was 0.02mm runout before machining.

07/01/2015 13:41:15

The bushing in my duplex cgnage gear was too tight..needed some severe persuasion to remove from the paired bearings in there. (Discussed with Chester before i attempted that in case of damaging the bearing since thisbush has a shoulder andthe inner race couldn't be protected. )

The bushing requires reversing when that duplex gear is reversed.

On to the question. The shouldered part is about 13mm long x 24mm diameterand was held in the 3-jaw. I indicated and best runout I managed was .2mm on the axle part of the bushing. (if I hadn't misread the DI I igh have tried longer to go to 1/100ths. The axle part is 1.5mm diameter and about 22mm long

Using the DRO I scratched and then fed in 0.02mm and took a slow shave. A test fit at that time was still too tight to push in by hand. I fed in another 0.005mm on the DRO shave again and hit it with some scotchbright.

It now slides in very easily.. acceptable but I'd have preferred it a tad tightter

Never having machined stuff to tolerance fits that seems odd. My first cut was a slow handwheel job because this feed gear was out...and anyway for a newbie this was close to the chuck. Is this a case of the cut raising a fine bur that should have been scotchbrighted before the second cut?

Thread: Vertical Shear Lathe Tooling
06/01/2015 17:06:03
Posted by chris stephens on 06/01/2015 15:33:42:

...

Re that American video chap, can't help but feel he thinks he is still talking to school children, instead of second childhood children! He is far too dogmatic for my taste but to be fair you can learn a few basics learn from him.

chriStephens

He spent his career teaching high school machine shop...

Thread: elf and safety gone mad
06/01/2015 17:02:27

I'm always amused by the need for compliance by every A&E unit havng to have it's green first aid box and accident book.

In the early days of all this I had a visit at my surgery from H&S and my answer to their question of 'where is your first aid kit' - "your standing in it" wasn't greeted very well.

They also complained that I had a 'toilet duck' in the loo that clients might use. "what if a kiddie drinks it?" They demanded. And once more my answer of "If it's that young or stupid one asumed it's parent will accompany it. And you don't see to mind the fact they've just walked past a cupboard full of pharmacy to get there"

Grrr

Thread: Safety Glasses Side Shields
05/01/2015 19:38:59

A good optician will do cool stuff. I had them make me up a pair of my prescription glasses with an extra flip-down lens pair for close-up work rather then use the fancy loupe I'd bought 'cos it was horribly heavy to wear for any length.

You might make your own side bits.. a bit of polycarbonate and a coupe of simple spring clips...

05/01/2015 15:21:17

I wear specs too and wore a pair of cheapo safety glasses over the top of them while grinding yesterday...and completely forgot i was wearing both pairs until the wife pointed it out some hours later...

No idea what brand they were but I'm a mean beggar so doubt I paid as much as £4.90 for them...


If it's just side bits you really want then I was going to suggest a ski shop.. the side bits to protect against snow blindness... but a quick look at the silly prices for fashion sunglasses makes that a real no-no

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