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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: internal grooves for o rings
01/06/2020 18:37:28

I've not tried that job but the problem with most form tools is that the load goes up as the tool shapes the space. first thought is the rigidity of the boring bar and how far in the bore you need to get to to minimise stick-out of your tool and keeping the tool tip as short as possible. You can also try cutting the groove with a narrower tool as two bites and then traverse the bottom.


Thread: Coronavirus
01/06/2020 16:15:26

There are so many variables to consider that analyses are difficult.. Simply consider a country with more than adequate testing capacity testing any and every in-contact and individual that feels slightly unwell and they will have a higher number of +ve cases compared to a country that only tests likely candidates that need hospitalisation. Perhaps more important is also the type of test used since these will vary in % of false positive or negative results (sensitivity v specificity; also depends on the lab and tech doing the test). One should also consider how a death cert re coronavirus is decided upon - actually by a proven test or a convenient reason to put on a certificate - and if it was by proven test was that the real cause of death or a contributing factor only.

It was mentioned earlier in this thread that the original idea of COVID19 was as a respiratory disease but it manifests as a vascular disease in many patients such that ventilators aren't the wonder answer - it's also access to other support measures including dialysis for a subset of those who fall ill and probably access to clinical acumen and clinicians who aren't overwhelmed - more so than technology?.

Just look at some of our own confusing figures: link
Deaths from C-19 38K+
Deaths where C-19 is mentioned 45K+
Deaths higher than usual for the time of year 59K+

Gov published figures for regions vary wildly too Link... but that will be as much down to when it got in there and how the local population has taken to control measures Indeed areas with low pecentage cases are those waiting to catch up...


01/06/2020 09:26:49

<<On 17 March, Sir Patrick Vallance, the government's chief scientific adviser, said keeping the number of UK deaths below 20,000 would be a "good result" from the COVID-19 pandemic. >>


He may not be an elected MP but still a gov mouthpiece but not a point I intend to argue further.

If I recall correctly they also stated that unchecked COVID would kill 500K citizens which is also 0.8% population and unless there is some startling new therapy/vaccine then we're on track. It'll just take a whole lot longer and as a series of small numbers be more 'acceptable' to the public albeit more devastating to the economy and non-COVID public health.

I remain cynical.


01/06/2020 06:17:40
Posted by Martin Kyte on 31/05/2020 17:12:43:

I though they said we would be doing really well if we kept it below 20,000 actually.


Political speak for 'we expect less than 20K and then we'll tell everyone how wonderful we were'

38.7K and rising.

Differing testing percentages and how deaths are counted - as in not everyone that might have it gets tested and at the moment population testing is in small samples that aren't too statistically valid. We're told that 7% UK population tests +ve for antibodies (rextrapolated from small samples) but less than 0.4% population has been tested and found postive for the virus (i.e. potentially sick people) with 13% mortality.

If 7% population actually has had it then mortality rate is 0.8%.These are such wildly different figures that it's impossible to know what to believe.


31/05/2020 17:02:52
Posted by SillyOldDuffer on 31/05/2020 15:42:15:

UK policy is based on a prediction that unconstrained Covid-19 would kill about 300,000 Brits. There's no doubt lock-down is effective. As of yesterday we're only up to 38,768 deaths.


We were also told that lockdown could keep the death rate below 20,000.
the trouble is that all these estimates (guesstimates) were pulled out of a statisticians backside based on numbers from other countries with differing counting methods + assumptions like actually having equipment.

it'll only be after it's over (if it ever is) that a count-back will tell us whether the overall death rate was improved by lockdowns (slower death rates, lower levels of immunity lasting unknown time) compared to letting it go wild (high initial death rate and high initial percentage immune population) with the differeing time frames to economic recovery/performance.

I wonder how many folk will now follow the regime of masks throughout (ordinary) flu season?


Thread: Surface Plate & Height Gauge recommendations
31/05/2020 14:46:55

I must admit I've resisted buying a surface plate and (when required) use the mill tbale. I can see me buying a secondhand surface plate and vanishing down the rabbit-hole of wondering how flat it really is and either hunting up semone to re-surace/certify it ot buying more stuff to try and check it with. You only need to look st some of Tom Lipton's Youtube vids to see how small a deviation can be measured and how much you really need a surface grinder and....


Thread: Coronavirus
31/05/2020 09:17:06

Let's not forget that the original idea behind lockdown was to 'flatten the curve' and avoid overwhelming the NHS. Gov admitted early on that they were suprised by public compliance. Fear worked, probably helped by the appalling figures for mortality amongst those admitted to hospital; figures which suggest either that the UK strain was somehow worse than some other countries or by some poorer approach to treatment here. It will be some time in the future (or hidden from public) as to how our therapy performance compared to elsewhere.

From the viewpoint of Gov there are all the other consideration - economic woes, loss of access to other medical needs - delayed surgeries, dentistry, mental health, home abuse and lockdown mental stress and as always the inevitable shuffling or blame and criticisms associated with political capital and political point scoring.

Lets also not forget that clearing out the old and infirm and weak is to Gov's advantage financially so long as they can keep the public believing it's not their fault.

With no effective therapy or vaccine on an immediate horizon then the only solution is to slowly let the virus work it's way through the population and sort itelf out because we don't have the ability or resources to quarantine the whole country due to our dependance on imports and a Gov that wants to be on a world stage. Without so doing any reduction in cases will just end with subsequent flare-ups - this whole thing started UK with only a few cases and they are going to keep coming in.

It really comes down to each individual looking out for themselves and sad realty is that some folk are more capable or financially able to do that than others. I can just imagine the mental and physical health tolls on single parents in tower blocks with strings of difficult kids and low education standards. For them the overall whole life risk is probably less out and about and at school and getting fed than being cooped up.

You'll start to see the pattern where areas of the country that shut visitors out early on and stayed with low numbers of sick will be the areas with the highest case load next..just because they have the fewest numbers that caught it and became immune and complacency has occurred.

we've finally had two cases outlying my area but you donlt see even 1% wearing a mask or keeping a real distance when out and about unless controlled by shop staff. At least folk have stopped looking at me oddly when i rock up with my industrial P3 mask on and disposable gloves.


Thread: Method of joining for chuck key?
30/05/2020 17:40:25

How about making the handle hole a subtle oval? It could fool the eye and add security to any adhesive.


Thread: Repair advice, please!
27/05/2020 22:24:37

Looking at vids of the metalstitching it's certainly an impressive process. But.. if used on a curved surface I'd assume you'ld need stitches of that radus? And close to the bolt lugs would be an issue too?


27/05/2020 09:50:32
Posted by Howard Lewis on 27/05/2020 09:24:07:

The casting cracked because of an excessive tensile load at that point.

Will an adhesive have a greater tensile strength?

If you have a lathe with a large enough capacity, you could possibly make a replacement from a block of steel.

A flycutter will mill the faces that need to be flat. A boring bar will produce the bore. A slitting saw on an arbor, between centres, with the job held on the Cross Slide or Toolpost, will produce the split. A similar set up of the job will allow the drillings to be made.

Not necessarily an easy or quick job, but not impossible.

And being steel, less likely to crack in the future.



If the item is a stand alone collar + necessary clearance/capacity the no reason it can't be made from two pieces of rectangular bar and bolted top and need for slitting saws or milled faces.. Function over aesthetics...just bored and drilled.



Edited By pgk pgk on 27/05/2020 09:51:10

Thread: Stand for Dremel type power tool
27/05/2020 06:42:33

Another simple holder. Can't remember the thread i cut but it was a dremel copy anyway..



Thread: Stressing over numbers
26/05/2020 09:56:33

I get days like that too...

Are you sure the DRO movement was diameter? If you went in 0.9mm with the toolbit then you got the expected result.

As to telescopic gauges..known problem beasts even in the best hands and in my shed things oten get worse in summer when it slowly heats up in there or winter when the woodburner finally starts kicking out too muh heat and not everythng has come to the same temp. If it;s a critical measure then I pick my time, recheck mics against standards etc or make up a plug gauge.

I'd guess I'm not the only one with a bin full of bad fit scrap.


Thread: Repair advice, please!
25/05/2020 12:26:06

I don't see that lockdown stops you getting a competent welder in...England allows for journeys for work and with only one of you in the hobby shed you're keeping your distance. Any concerns about the welder contaminating your shed could be resolved by staying out of it for a few days after his visit. Of course it would be better to move the D-W outside but a major chore solo.

I know that if I was faced with the same issue here I'd have a word with my local agri engineers and they'd almost certainly sort it (but then I've spent lot of money with them over the years). Agri engineers seem pretty flexible chaps due to the nature of the stuff they have to sort and where they have to sort it..

I have a lot of respect for epoxy and I'd expect it'd probably work with the huge surface area involved under your cover

Another option would be to create a bunch of split-collars-with-bolts out of, say, 15-20mm steel and layer them between the original lugs in addition to the epoxy while it all sets up. You might even get away with large hose-clips if the tube is emptied and the gap wedged to close up the cracks during epoxy-set.

Final though is to create a similar solution as you have but with it's own lugs and bolts that are a sliding fit through the originals. It'd probably take an acetylene torch to do the bends


Thread: Internal threading question
23/05/2020 13:12:14
Posted by pcb1962 on 23/05/2020 12:00:34:

Thanks Jason, you've been extremely helpful, but I think this time I will go with a tap, what's "plenty of room" to you is I feel still going to be very tight for me, thanks again.

I might well do the same thing in practice but another of Joe Pie's vids demonstrates cutting a partial depth internal thread outboards i.e lathe in reverse (if you dont have a screwed on chuck) whch has the benefit here of proving the clearance on each tool entry. Also he makes the point that the first pass can be a larger depth of cut than subsequently since the actual cutting surface at that time is smallest. It also allows you to use the smallest stick-out of the tool since you don't have to worry about when to disengage the feed.

For total cowardice there's nowt wrong with a handground HSS tool and manual cranking of the lathe. It's tedious turning the chuck with two keys but do-able..


22/05/2020 07:00:31
Root and crest widths different for each size thread = ideal tool or each thread.
Tom;s Techniques I referred to earlier has a good vid on hand ground thread tools and explains helix angles too



Edited By pgk pgk on 22/05/2020 07:01:47

Edited By pgk pgk on 22/05/2020 07:04:24

21/05/2020 09:05:54

I'll first admit that the only internal thread I've cut was a 1" thread as practice following Toms Techniques Youtube vids when I started playing and using a hand ground cutter. A smaller internal hole with a tight tool and I think i'd cut it away from the chuck with inverted tool to make it easier to check clearances and place the tool before each run.


Thread: Macro rust spots.
21/05/2020 08:35:34

I also had a similar pattern on a stainless sink that I flushed some tiny Potassium Permanganate crystals down. I assume it acted like a strong oxidiser with the pattern where the tiny crystals had lingered. EDM I assume will have similar electron movements very dependant on steel composition and spark pattern??


Thread: Stirling Engine Fan
20/05/2020 19:30:17

I find getting smaller paraffin heaters to work very challenging and can spend ages trimming wicks and messing about and finally giving up. As a Student we had one of those Aladdin heaters that worked a treat but my most recent excusion with greenhouse paraffin heaters was a disaster. I got the things buring nicely before i left them for the night and a.m. found the whole inside of the glasshouse covered in oily soot that took hours to clean off with soft brooms and detergent.
Hopefully you'll do better. Or do what i did and go electric heat..

Thread: Unknown tool
17/05/2020 18:41:06

Looks like the supplied tool with my bench grinder for refreshening the wheel surface.


Thread: Using a cats cradle corectly
15/05/2020 10:35:34

I'm not entirely sure i understand that post. I guess the raw square stock won't fit inside your headstock so any set-up is bound to be tedious. I'd probably cut a short length that can be held in the 4-jaw without 'drooping' and then use the simple trick of 4 bits of flat scrap and an elastic band so one can indicate on the inside surfaces (quicker) to get the 4-jaw pretty well centred. Then do the same thing with your cats cradle in the fixed steady wth that trial piece of spare stock before setting things up at their relative distances and finalising indication at the ends and middle with the workpiece and facing it's ends.


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