[time-nuts] repairing Maser threads

[Robert Atkinson]

Hi Ernie,
You can get M5.5 screws fairly easily (in the UK at least) It's actually a "cheat" size, almost identical to the old 2BA screw. 2BA was used in electrical fittings and there were so many in use that a replacement was required that fitted older fixed installations like junction boxes cemented into walls. M5.5 screws are also found on many diecast boxes, usually the "taptite" tri-lobular thread forming type.
 
Robert G8RPI.

--- On Tue, 13/4/10, ernieperes at aol.com <ernieperes at aol.com> wrote:


From: ernieperes at aol.com <ernieperes at aol.com>
Subject: Re: [time-nuts] repairing Maser threads
To: time-nuts at febo.com
Date: Tuesday, 13 April, 2010, 23:47



Hi,

you can not go step like 5.5 mm or so.... the best thing is to cut a new M6  thread because it is the next most available screw size
in metric.....
I had a lot of problem with the American size thread but the best solution was always the next higher most common metric size......!!!!

Rgds Ernie.









-----Original Message-----
From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Wed, Apr 14, 2010 12:19 am
Subject: Re: [time-nuts] repairing Maser threads


Dave wrote: 

>Another solution - especially with metric - is to tap the holes ( >only bad - or all - so that they all match) to the next larger >Metric size - of the same thread pitch as original - so as not to >cut across the original threads, but just cut the same thread pitch >to the next size, such as from 5mm to 5.5mm or 6mm. Then you only >have to buy a standard - not too expesive - metric tap - and some >new slightly larger hardware. 

Unfortunately, 5 mm is the only standard metric thread with a 0.8 mm pitch, so you'd need a custom tap and would need to make custom bolts. Hence, my suggestion to just make some custom bolts in "M5.2x0.8" or "M5.5x0.8," whatever is necessary to get a tight fit. Same approach, but less work (although if someone ever loses the bolts, they'll go crazy trying to figure out what to use for replacements). 

What I didn't mention previously, but would be good practice if you went that way, is to cut one straight flute on the bolts (look at a self-tapping machine screw to get the idea) to make it easier for them to deepen the major diameter of the original 5 mm thread. 

Best regards, 

Charles 



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