On 19 July 2024 at 13:28 Andrew Tinsley Said:

I am somewhat nonplussed. The recommended drill is 12 mm ..

Not in my book.  13mm is more like it.  Depends on the pitch, p=2, 12.7mm; p=1.5, 13.00mm; p=1.25, 13.2mm.

Unless there’s good reason not to, I follow Tubal Cain’s guidelines and drill tap holes a shade bigger than industry.

Be interesting to put a microscope on the Presto Tap to see how much damage has been done by attempting to force it into a too small hole.  Hopefully not much, though the later refusals to start are worrying. At least the Presto survived an accident that might have snapped a cheaper tap.

Could the taps be counterfeit?

Dave

A handy tabulation [just one of many]

https://www.carbidedepot.com/formulas-tap-metric.htm

MichaelG.

I have always started with metric thread diameter minus pitch to give the tapping drill size.  While this mostly works, smaller diameters in harder materials will benefit from slightly bigger diameter.  On larger threads always run through the typical three tap set, smaller threads will benifit also but sometimes the lead on the tap is too much for the drill depth.  Essentially you must make sure you have started the thread square to the hole otherwise it may become tight or strip the thread.

On 19 July 2024 at 14:02 Andrew Tinsley Said:

… I think Dave must be suffering from the heat, as just about any list of tapping drills for Metric coarse gives a 12mm tapping drill for M14. …

Can’t blame the heat as I’m in the West Country where it’s cooler!

Maybe gremlins temporarily changed the page in my book: just checked again, and of course it says 12mm.   More likely, being uncomfortably unwell at the moment is doing my head in.

Sorry for the confusion.

Dave

Sounds more like too much west country cider😜

OK, I,ve just copped it !, another cock-up ! That should be Angels, not Angles. Must be the Silly Season.

Still, I,m in good company !

On 19 July 2024 at 15:34 Andrew Tinsley Said:

No problem Dave. I am suffering from severe sinus problems so I know how you feel. If I had been normal, I might well have spotted the left hand tap problem, but I didn’t!

 

Andrew.

Poor you, I’m a fellow sufferer.  Sinus problems are truly horrible: made my middle-age miserable and then just stopped. Fingers-crossed it doesn’t come back.  Can’t recommend a cure because the trouble gradually faded away for no apparent reason!  None of the medical treatments worked.  After surgery I remember them removing a bandage stuffed into my sinus cavity, producing more and more of it like a magic trick.    The bandage was enormous!   Apparently the front of our heads in the sinus region are mostly empty, maybe to improve balance, and if anything goes wrong inside, the patient suffers a painful and difficult to fix attack.   On a scale of 1 to 10, where 1 is mere discomfort,  and 10 is wish for death,  how painful varies from 2 or 3 (alleviated by over the counter pharmaceuticals), to 8 or 9.  Can last for a few days or decades.  Sinusitis often does an excellent imitation of severe toothache.

New theory about Gremlins.  They’ve discovered the web and are using it to spread global havoc.   They arranged delivery of Andrew’s Left Handed taps, then sabotaged my book after noticing I was reading his question and finally tweaked CrowdStrike’s security update to crash the internet!

Dave

On 19 July 2024 at 15:44 JasonB Said:

Sounds more like too much west country cider😜

Potent stuff.   In the 70s my local pub sold traditional Scrumpy, and featured a bench full of elderly farm labourers, all apparently brain-damaged!

My boss at the time was a tough young Scot, who, visited in Somerset by his equally hard-drinking mates, took them to a Scrumpy pub, where they drank heavily.  He said they expected 8 pints of ‘Apple Juice’ to be much the same as 8 pints of beer, which they were all up for.  Sadly, they were in the presence of evil, because the locals encouraged them in this belief, buying them rounds of rough Scrumpy.

Traditional Scrumpy is in a different league to most beers!   Trouble started in the car-park, where the group went from happy drunk to 999 emergency  over the next half-hour.  My boss described hallucinations, projectile vomiting, repeatedly fouling himself, going in and out of consciousness, and terrible headache.   No recollection of what happened in A&E, only being discharged a day later with his worst-ever hangover.

Back then, with many honourable exceptions, Scrumpy was made on farms, using methods and materials that met no standards whatever.   Scrumpy ferment requires meat, and the usual source was dead rats dropped whole into the vat, fur, guts and all.  Apples could be covered in mould.   No control, so entirely possible the alcohol content could be increased by adding meths, or sweetened with anti-freeze.   The people who drank Scrumpy were looking for a cheap powerful hit, ideally going to bed suitably anaesthetised after a few pints.

Not sure if anyone still makes rough Scrumpy.   More care with Apples, cleanliness, and they use fresh supermarket mince rather than old rat. Still unexpectedly potent, but far more refined than it was.   Recommended, especially the dearer versions – in moderation!

Dave