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Member postings for colin hawes

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

Thread: New Micrometers
05/12/2021 16:06:23

If you rely on using the clutch to take readings it is easy to inadvertently include a speck of swarf as it is not felt ; it is my opinion that finger touch on the thimble is more likely to show up such an event . Although I confess I've never experienced it on a micrometer, I have seen a clock digital display with a number giving a wrong figure due ,presumably, to the connecting matrix becoming faulty and losing a part of the digit. Colin

05/12/2021 11:43:53
Posted by SillyOldDuffer on 03/12/2021 14:44:17:
Posted by colin hawes on 02/12/2021 19:17:50:

A decent mechanical micrometer will only develop very small errors due to wear or operational "feel" whereas a digital electronic one could introduce unknown errors so for maximum accuracy I prefer the mechanical micrometer. Colin

Is that true? What 'unknown errors' are introduced by digital micrometers?

A common type has a digital display mounted on an ordinary analogue instrument with a differential screw.

mitdigmicrometer.jpg

I wouldn't expect a difference in accuracy. The advantage of the digital display is eliminating misreading errors, and being able to do Imperial/Metric and offsets etc. The disadvantage is needing a battery! The analogue and digital display can be checked against each other. Owners please, do they differ, and if so, which reading is less wrong?

Another type is digital only. There's no analogue scale. Although the example below looks cheap and plasticky to my jaded eye, it's made by iGaging and like the Mitutoyo pictured above reads to half-tenths.

igdigitalmic.jpg

Seems to save space, and I suspect this type doesn't contain a precision differential screw, relying on some other arrangement, perhaps a miniature DRO track and rotation counter. They're not expensive. Does anyone know how they work?

The problem with differential screw micrometers is they depend on the production accuracy of an expensive screw, which is vulnerable to wear, tear and dirt. They're particularly prone to wear on one section of thread if the instrument is repeatedly used to measure similar sized objects. Like the curates egg, worn micrometers are only good in part. A digital instrument could avoid wear problems by not relying on a precision thread, instead directly measuring movement along an optically or magnetically precise track.

Anyone have experience of them?

Dave

Edited By SillyOldDuffer on 03/12/2021 14:45:32

Reading inaccuracy caused by a reading circuit problem giving a believable false reading. A mechanical instrument can't present such a reading. Colin

Thread: Horizontal mill arbor
05/12/2021 11:14:16

I have used horizontal mills for many toolmaking years and have never needed keyways even on quite heavy powerful machines but on hard working heavy production work they are used to maintain accuracy with gangs of cutters and to make it possible to unscrew the arbor nut after heavy use I have seen a case hardened arbor nut "explode" under heavy industrial use due to lack of a key tightening a cutter gang. That takes a LOT more power than us model makers are ever likely to see. If the at least one spacer needs to have a keyway to make it possible to use a key with thin cutters Colin

Thread: New Micrometers
02/12/2021 19:17:50

A decent mechanical micrometer will only develop very small errors due to wear or operational "feel" whereas a digital electronic one could introduce unknown errors so for maximum accuracy I prefer the mechanical micrometer. Colin

Thread: Is Model Engineering "green"?
30/11/2021 17:19:18

Seems to me that natural pollution from volcanos and forest fires has a bit to do with excessive CO2 and the loss of trees has a lot to do with failing to reduce carbon absorption .Why didn't we hear so much of global warming in the decades of smoky domestic chimneys? Colin

Thread: Cutting up bits of metal
14/11/2021 18:45:42

I use a Warco 6x4.5" bandsaw for mild steel and soft metals, an angle grinder to cut tool and high tensile steels (to save the bandsaw blade) and a horizontal mill to cut steel plate that won't fit in the bandsaw. Colin

Thread: Music on TV Programmes.
13/11/2021 13:17:23

Quite often I get a good laugh at subtitles; are the "howlers" created by poor elocution?; also there seems to be vastly more bad language than there used to be; Why?

13/11/2021 13:17:22

Quite often I get a good laugh at subtitles; are the "howlers" created by poor elocution?; also there seems to be vastly more bad language than there used to be; Why?

Thread: UK fires up old coal power plant as gas prices soar
07/11/2021 10:46:10

I think that the only reliable natural energy source in UK is tidal rise and fall as it varies all around the coastline so overlapping generation could provide a continuous supply.. More development needed. Colin

Thread: Motorcycle wheel spindles
30/08/2021 11:22:50

I don't consider EN8 to be strong enough for this application. I would NOT risk my neck on this material. Colin

Thread: Useful MEW Table
07/04/2021 18:00:43

I fixed about 20 data sheets on A4 pages in book form to cardboard backing sheets and hinged it on a cupboard door in my workshop so I can easily flip to the page I want; the page is held in place with a spring clip. This way I only use the area of two A4 pages. Colin

Thread: Shaping Skew Gears on a Lathe
07/04/2021 17:46:39

Very interesting setup. colin

Thread: Cleaning up BSW threads
31/03/2021 19:29:36

It is easy to think a 1/2 " thread is Whitworth 12 tpi when it could be UNC which is 13 tpi whereas most of the UNC threads are the same pitch as Whitworth. Could the machine have UNC threads? Colin

Thread: Taps with plus sizes?
31/03/2021 19:12:09
Posted by Tony Pratt 1 on 31/03/2021 17:59:10:
Posted by colin hawes on 31/03/2021 17:28:44:

They are used on steel that has to be case hardened to allow for hole shrinkage/distortion. Colin

Good engineering practice is to plug tapped holes so the threads remain soft during the case hardening process or you can carburise the part then drill & tap the required holes then finally harden.

Tony

I have cyanide case hardened threads to about .005 deep on tooling that requires a wear resistant tapped hole. It gives long life and greater strength. The taps used were known as "B" taps. Colin

31/03/2021 17:28:44

They are used on steel that has to be case hardened to allow for hole shrinkage/distortion. Colin

Thread: How to make a spring
30/03/2021 10:47:03

I would definitely bend that spring at red heat to avoid it cracking .Colin

Thread: Welding and Pacemakers
11/03/2021 12:58:56

Michael G, many thanks for your references there seem to be an awful lot of precautions to remember when fitted with a pacemaker. I have been recommended for one and it seems likely to make a huge impact on my restoration and workshop activities. Thank you for inviting me to P.M. you, I may well do that at some time.

Thanks also to everyone contributing to this discussion. Colin

Thread: What’s this tap? Thread form?
10/03/2021 17:24:29

Stubby taps always make me think.... Pipe thread. Colin

Thread: Welding and Pacemakers
10/03/2021 17:18:16

Having recently been threatened with the prospect of having a pacemaker I am interested in the implications for arc welding; Has anyone had experience of this as I use mine very frequently without a second thought? Will I have to give it up or wear special protection? Colin

Thread: A Certain Age
10/03/2021 16:58:54

I was taught the following: "there is a number of items" is correct , "There are a number of items" is not correct because there is only one number.

But I see the second incorrect statement all the time. Was my teacher wrong or has the language changed? Colin

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