The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

Supporting all legal firearm owners, collectors, enthusiasts, shooters and competitors by promoting and encouraging legitimate gun ownership and use in the UK through unity, advocacy and discussion. To REGISTER contact admin(at)full-bore.co.uk
It is currently Mon Jun 01, 2020 4:05 pm

All times are UTC




Post new topic Reply to topic  [ 36 posts ]  Go to page Previous  1, 2, 3, 4
Author Message
PostPosted: Tue Jan 21, 2020 6:29 pm 
Offline
Site Supporter Since 2015

Joined: Wed Aug 31, 2011 7:05 pm
Posts: 1395
Ovenpaa wrote:
I calibrated a metric digital micrometer for our own use today, the calibration temperature was 17,5C and it was zeroed at 25,000mm (25 to 50mm range) I have just popped the calibration gauge in my pocket to warm it up, this will be interesting. Right now it is now coming up as 25,021mm so it has 'grown' by just under 8/10th of a thou in old money, which does make a bit of a mockery of measurements. This is why I always ask for the tolerances when I am sent a drawing and in the absence of a tolerance I add a premium and record the temperature value at the time of cut.


I'm really surprised that good quality calibration gauges are not made of something like Super Invar that has a very low thermal expansion rate, as used for the pendulum rods in really serious astronomical observatory type clocks, up until fairly recently.

_________________
TARGETMASTER
an altogether better trickler
www.targetmasteruk.com


Top
 Profile Send private message  
 
PostPosted: Tue Jan 21, 2020 6:44 pm 
Offline

Joined: Thu Oct 13, 2011 9:36 am
Posts: 894
Location: Highlands
Home club or Range: Strathpeffer Rifle & Pistol Club (& Cawdor Rifle Club)
I worked on a 'metric' facility with a load of yanks (maybe not yanks but good ole southern boys) and most of them were totally confused. I pulled up one guy for trying to kick open a 6" ball valve with about 120 bar gas pressure on it. Yo! take it easy, there's 120 bar there!! He goes blank and says, " Bar? PSI? what the difference!! Mind you half of them couldn't write there names, let alone read a pressure gauge.

However, I have worked with gauges in Bar, Atm., Kg/m2, PSI, MPA, kPA even Inches WG & mmHg. It is easier if the whole plant is using the same standard, not always the case though. Quite common for Oil & Gas production facilities to use metric & the Drilling rigs onboard to use Imperial.

_________________
Rifle & Pistol Shooting in the Highlands with Strathpeffer Rifle & Pistol Club.


Top
 Profile Send private message  
 
PostPosted: Tue Jan 21, 2020 6:46 pm 
Offline

Joined: Thu Oct 13, 2011 9:36 am
Posts: 894
Location: Highlands
Home club or Range: Strathpeffer Rifle & Pistol Club (& Cawdor Rifle Club)
1066 wrote:
Ovenpaa wrote:
I calibrated a metric digital micrometer for our own use today, the calibration temperature was 17,5C and it was zeroed at 25,000mm (25 to 50mm range) I have just popped the calibration gauge in my pocket to warm it up, this will be interesting. Right now it is now coming up as 25,021mm so it has 'grown' by just under 8/10th of a thou in old money, which does make a bit of a mockery of measurements. This is why I always ask for the tolerances when I am sent a drawing and in the absence of a tolerance I add a premium and record the temperature value at the time of cut.


I'm really surprised that good quality calibration gauges are not made of something like Super Invar that has a very low thermal expansion rate, as used for the pendulum rods in really serious astronomical observatory type clocks, up until fairly recently.



That's why the calibration certificate for the gauge uses a 'standard' temperature rating.

_________________
Rifle & Pistol Shooting in the Highlands with Strathpeffer Rifle & Pistol Club.


Top
 Profile Send private message  
 
PostPosted: Tue Jan 21, 2020 11:48 pm 
Offline

Joined: Sat Jul 23, 2016 9:50 pm
Posts: 118
Home club or Range: Invicta Bristol, Frome and District PC
I was talking to the chaps installing our new CNC mill, they were quite impressed that we were installing it in a room with climate control ( only within 2 deg C ).

Apparently most of them (£250K machines FFS!) get installed in sheds with no climate control.

I used to drive one in a shed where my water bottle would freeze in the winter, and it would be 35+ C in the summer.

No wonder half the parts I send out for machining by external companies come back out of tolerance.


Top
 Profile Send private message  
 
PostPosted: Tue Jan 21, 2020 11:58 pm 
Offline

Joined: Sat Jul 23, 2016 9:50 pm
Posts: 118
Home club or Range: Invicta Bristol, Frome and District PC
Generally I agree with TRG-22, especially;
TRG-22 wrote:
And recent changes have made me embarrassed and ashamed of it.


I like metric, I'm bilingual, but metric is significantly easier to use, and I generally use it when I'm designing things, unless those things need to mate with existing imperial parts.


The metric thread system is to be preferred, I like to keep things in one standard, rather than, BA, UNC, UNF, Whitworth etc. My stock of screws is entirely metric at work, with the exception of a few UNC/UNF for equipment made in the US.


I had a frustrating discussion today regarding NPT and BSP threads. I know BSP is actually the ISO standard, but part of me does wish they'd created a more sensible standard, and that the septics hadn't made a competing standard that is impossible to tell apart for practical purposes, expect that they don't actually mate.


By the same token, I don't know my own weight in Kg, or my height in cm, and I'm as likely to cook in oz as g (though I always use C not F). I like pints in the pub, and don't really mind if its mph or kph, as long as its consistent for daily use.


Worth noting that the current 'imperial measurements' are defined both here and in the US, as conversions of SI units. (A UK pint is 568ml, an inch is 25.4mm).


Top
 Profile Send private message  
 
PostPosted: Wed Jan 22, 2020 10:29 am 
Offline
Site Supporter Since 2019

Joined: Fri Dec 10, 2010 8:33 pm
Posts: 780
Location: Wolverhampton
Home club or Range: stourport
Back in the 1970s, we went metric on chassis fixings. Our new protype vehicles started to fall apart on testing. There is a non-preferred metric fine standard which is actually a good thread, but the commercial people were against using it on cost grounds. We adopted "sticky bolts" which were standard metric coarse threads with a dab of loctite on them. We could not stop people checking for tightness after the initial running in period and they turned the whole fastener and lost preload. In the end, we adopted washer faced nuts and bolts, which were still cheaper than the fine thread alternative and these proved successful. We bought a "New Generation" Mercedes truck at this time and were not surprised to find that all structural connections used fine threads.
I got curious about which of the many thread standards were the best and commisioned a test programme backed up by finite element analysis.
It turned out that there was an optimum thread design: BSF.
Fred


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 36 posts ]  Go to page Previous  1, 2, 3, 4

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group