[Healeys] 100 front brakes

[Michael Salter]

It's a bit more complicated than that.
There is actually no such thread as an AF thread. AF refers to Across the
Flats and is measurement across the hexagonal nut and denotes the spanner
(wrench) size.
i.e. a 5/16" UNF bolt is 1/2" AF.
There was a change made in the name of the thread form early in BN1
production from SAE (Society of Automotive Engineers) some say (Standard
American Engineers but are wrong) to UNF (Unified National Fine). SAE
actually refers to the "Family" of threads which includes UNC and UNF.
These threads have a thread angle of 60 degrees.  The "F" and "C" refer to
the pitch or threads per inch.
For the most part the threads used on the brake lines of Healeys are 3/8" x
24. 3/8" diameter and 24 threads per inch.
Whitworth refers to a different and older "family " of threads which have a
55 degree thread angle.
I should mention that there were also some differences in the shapes used
at the bases and peaks of these different thread forms which Google can
help you with if you haven't already fallen asleep.
Hope that doesn't serve to further muddy the waters.

M

On Sun., Feb. 26, 2023, 3:26 p.m. Hank Leach via Healeys, <
healeys at autox.team.net> wrote:

> Gary- The note about the type of thread used was what I was referring
> to-mentioned earlier. The early BN1 used AF type threads.(equivalent to a
> 1949 Chevrolet). All the later cars (and I do not know where the changeover
> was-maybe Michael does) had unified Girling threads. The lines should
> thread easily or else you have a different thread count and pitch. I don't
> think you will find the early type hoses from any supplier. They will have
> to be special made or found in NOS. Hank
>
> -----------------------------------------
> From: warthodson at aol.com
> To: "gradea1 at charter.net"
> Cc: "healeys at autox.team.net"
> Sent: Saturday February 25 2023 1:24:04PM
> Subject: Re: [Healeys] 100 front brakes
>
> This car is a BN1.
> Yes, I was referring to the brake wheel cylinders or slave cylinders as
> opposed to the master cylinder.
> What are you referring to when you say  "Be sure that you were supplied
> the correct threaded hose...most suppliers do not have the early style."
> How do I identify an early style hose from a latter style hose?
> Gary Hodson
>
> -----Original Message-----
> From: Hank Leach <gradea1 at charter.net>
> To: 'warthodson at aol.com' <warthodson at aol.com>
> Cc: 'healeys at autox.team.net' <healeys at autox.team.net>
> Sent: Sat, Feb 25, 2023 12:59 pm
> Subject: RE: [Healeys] 100 front brakes
>
> Do you mean "wheel" cylinders and not "slave"...100s have a mechanical
> clutch. I understand that on all model Healeys the brake hoses have one
> threaded end and one flared end. That flare goes into the metal line nut.
>
> On the early 100 wheel cylinders they used an American AF thread but
> switched over to the Girling unified thread on later releases. The bleeder
> connection can be either in or out in shape (photo) but if the bleed screw
> is flat it uses the check ball (supplied in rebuild kits) and fits the
> recessed shape. The pointed bleeder uses no check ball.  Be sure that you
> were supplied the correct threaded hose...most suppliers do not have the
> early style. Use Girling red grease on the threads. Hank
>
> -----------------------------------------
> From: "warthodson--- via Healeys"
> To: "healeys at autox.team.net"
> Cc:
> Sent: Friday February 24 2023 5:15:16PM
> Subject: [Healeys] 100 front brakes
>
> I will be assisting a friend to replace the flexible hoses on his 100
> front brakes. He has ordered and received a set of hoses, but the ends that
> thread into the slave Cyl do not match the shape of the mating surface in
> the slave. The ends of the hoses are flat & it is my understanding that the
> cyl. is cone shaped inside. The vender says this is not a problem. I think
> it is a problem.
> What do you say?
> Also, if it is an issue, where can we get a set of flex hoses that have
> the correct ends for this application & are also the correct length (I.E.
> Not too short)?
> Gary Hodson
>
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