Oversize B9A Valveholder

['LIVEWIRE?']

May I point out that there are B9A Valveholders, of which the Edicron SK9CC22-H55 (Rapid 38-2012) is one, where the overall diameter of the ceramic base is too large to pass through a hole cut for a standard B9A base.
I discovered this when attempting to fit a new Edicron Holder in a Ferguson 2022 chassis, in which the hole is (as near as I can measure it) 18.5mm diameter, whilst the lower part of the Edicron base is 20mm diameter. The valveholder is in other ways standard, accepting any B9A based 'bottle', and comes with a retaining clip, useful in many applications, including in the 2022, where the valve is mounted horizontally.

[Restoration73]

The same applies to the Octal type. It should be noted that all of these valve holders
tend to have gold plated contacts.

[G8HQP Dave]

I seem to recall a standard B9A base needs a 3/4" hole (i.e. 19.05mm). These new bases, usually made in China, are in that sense non-standard. They can also have sockets which are too tight for normal European valve pins, so maybe Chinese pins are slightly thinner?

B7G was 5/8", octal was 1 1/8" (or was it 1 1/4"?).

A few years ago I managed to pick up quite a few NOS valve bases on ebay, so hopefully they will last me out and I won't need to buy any more modern ones.

['LIVEWIRE?']

You are right, Dave. 0.75" is the stadard diameter for a B9A valveholder. I've just tried the ECL86 in the new holder, and it's a good, tight, fit, which should mean that the retaining clip won't be needed.

[Herald1360]

Originally Posted by G8HQP Dave

octal was 1 1/8" (or was it 1 1/4"?).

1 1/8"

Still got the Q-max somewhere!

On a related note, some of the Chinese B8A sockets have no polarizing means to line up the valve.

['LIVEWIRE?']

I still have Q-Max B9A B7G Cutters somewhere, but can't find them, not that they would help in this instance. How to enlarge a hole in a steel plate by 1 or 2mm without access to suitable tools is the problem!

[vidjoman]

Originally Posted by Herald1360

On a related note, some of the Chinese B8A sockets have no polarizing means to line up the valve.

They do have a line moulded in. Easy to put a red dot on the chassis.

[John M0GLN]

Originally Posted by Herald1360

1 1/8"

Still got the Q-max somewhere!

Yes 1 1/8" is the normal size but I have one that fits in a 1" hole.

John

[John M0GLN]

Originally Posted by 'LIVEWIRE?'

How to enlarge a hole in a steel plate by 1 or 2mm without access to suitable tools is the problem!

One of these would probably be the best, but I don't know what suitable tools you are short of.

https://www.tlc-direct.co.uk/Main_In...l#Cone_Cutters

John

['LIVEWIRE?']

Thanks, John - you've teminded me that I have a conecutter somewhere, so, provibed it's the right diameter, I can enlarge the hole with that, though I only possess a hand-held electric drill. I can also get a new conecutter of the correct dimensions if neccesary. I haven't used one in a long while so forgot about them!

[Diabolical Artificer]

I advise slowing your drill down if using a cone cutter. When drilling out large diameter holes they have a nasty wobble. I put mine through a big variac.

The other problem with these cutters is that there is a "transistion" of a few mm or so between steps/diameters, it's easy to over drill.

Happy to pop a NOS B9A in the post for the postage to save you the hassle.

Andy.

[John M0GLN]

I advise slowing your drill down if using a cone cutter. When drilling out large diameter holes they have a nasty wobble. I put mine through a big variac.
The other problem with these cutters is that there is a "transistion" of a few mm or so between steps/diameters, it's easy to over drill.

There are two ( or maybe more ) types of these cutters, the one I suggested is the smooth tapered cutter rather than the stepped one, the photo is taken from the TLC catalogue.

John

['LIVEWIRE?']

John, theone I have is a spirally cut one, but I could get one of the smooth tapered type.
Andy, thanks for the offer. You have a PM. Somewhere in my parts stock (a.k.a. 'clutter!') I'm sure I have a new B9A holder, but can I find it, No!)

[Diabolical Artificer]

Here's the types I have, as you see thy fit differently. the one on the left measures 18.5mm dia. I suspect the one on the right is no good as it has little bits sticking up on the metal bracket.

Andy.

['LIVEWIRE?']

The one on the left should be OK, Andy I'll willingly pay the postage costs, by the way.

[vidjoman]

Originally Posted by Diabolical Artificer

Here's the types I have, as you see thy fit differently.

One fits above the chassis and the other below. Many of the Chinese ceramic types have a loose metal fitting that can be used under or over chassis.

['LIVEWIRE?']

The valveholder I obtained from Raid has a loose metal fitting, which would allow it to be fitted below the chassis, although I would have to remove the valve retaining clip to do so.

[Biggles]

The smooth cone cuts by their design make a slightly tapered hole. I normally clean up the hole edge by gently going through from the other side if space allows. You can also use the old trick of slipping a washer over the cone cut to control the depth/diameter of the cut, although this can scuff the area around the hole.
Alan.

['LIVEWIRE?']

Today I received the B9A valveholder from Andy (Diabolical Artificer) Thanks, Andy. PM, etc., to follow shortly.
NB I must be getting old -or is it the heat? Spot the typo in post # 17 'The valveholder I obtained from Raid, should, of course read 'obtained from Rapid, etc.!'