• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

G: Gearbox 1 1/4 20 tpi thread dimensions


hrdaustria

Well Known and Active Website User
VOC Member
Hello, I´m in need of details for the 1 1/4 x 20 tpi 55° thread used on the gearbox output shaft. I have to make a special g 23 nut for my Egli.
Thanks,
michi
 
Last edited by a moderator:

Robert Watson

Well Known and Active Website User
VOC Member
Or as my friend says, You really think a nut is going to know the difference that 2 1/2 degrees ((60deg- 55deg) /2) is going to make over the depth of the thread????
 

Magnetoman

Well Known and Active Website User
VOC Member
You really think a nut is going to know the difference ...
I'm sure that sometime in the last 100 years someone calculated or measured the effect of this difference on the ultimate strength. A 20 tpi 60-deg. nut will dig into the root of a 20 tpi 55-deg. bolt by 0.008". Also, if the nut makes contact at the h/6 root of a 20 tpi 55-deg. bolt it will be 0.0024" away from touching at the h/6 crest when finger tight.

The fact the threads of a mismatched pair require an additional ~5% distortion of the metal (0.0024"/0.050") in order to make contact must have an effect on the strength. We already know it's possible to strip any of the threads of matched pairs by applying too much torque so a mismatched pair must be measurably weaker, and measurably easier to strip. Anyway, in answer to this question, yes, I think the nut will know the difference.

p.s. I have 55-deg. indexible carbide cutters for threading on my lathe so it's no more difficult for me to make a correct Witworth thread as is an incorrect 60-deg. one.
 
Last edited:

vibrac

Well Known and Active Website User
VOC Member
I agree we are not talking about putting a unc 1/4 screw in a whit 1/4 bolt hole in alloy we are talking about a substantial diameter in steel in an important position
In the egli clutches with Vincent gearboxes especially belt drive I have worked with the standard nut works with some lathe work
 

Pist n broke

New Website User
Non-VOC Member
hrdaustria, this is a first time post for me, the info below may be of some help.

I assuming what your chasing is how deep to cut the thread, as you have everything else you need listed.

To work this out use the following equation.

Thread depth = Threads per inch / 1 x 0.64

20tpi over 1 = 0.050” x 0.64 = 0.032”

Just be aware this is theory depth, so when you get to this depth you will need to take side cuts using your top slid and you will most likely need to go slightly deeper than this depth depending on how well you have ground your tool to match the required root radius of the thread. Clean up of the thread crown can be carried out using an internal thread file holding a slight bit of on it. Don't put too much pressure on as it will chatter and dig in damaging your thread. You should check the fit of your female thread to the male thread on the shaft once you reach theory depth and then work your side cuts 0.0005" at a time checking each time you take a cut same applies if you are going deeper, check the fit each cut. Also when cutting female threads it helps to open the minor diameter of the thread out by about 0.005" before starting to cut the thread as the thread will grow inwards by around this amount through pressure from the cutting action of the tool bit

For reference 0.64 is the constant used for 55deg.
0.61 is the constant used for 60deg.


In answer to the comment on if a nut knows the difference between 60 degrees and 55, the answer is yes is dose. Mixing thread angles results in point load on the flanks, which promotes galling for the threads and ultimately binding.

Hope this is of some help.
 

Vincent Brake

Well Known and Active Website User
VOC Member
M. Ich wurde zuerst mal geau anschauen ob es die 60 oder55 gr geschintten worden ist am welle.

Dann: nur die innere durchmesser ist zu beobachten, und dann einfach am ende, schlichten je 0.02 mm machen mit versetz von die tiefe um 0.005mm. ( vielleicht etwas kleiner weil es ein 55gr ist)
Damit schneidet er nur an einen seite des flankes.
Und dann einfach gegenteil dabei zum passen.

Weil es ein gehartes teil ist, ist m nicht genau so wie die theoretisches abmass wie im tabelle.

Auch mal bestens Toolox 33 stahl
. Ist ja so um 40hrC
Oder 36nicrmo6.
Vergütet.

Gruss
V
 

peter holmes

Well Known and Active Website User
VOC Member
M. Ich wurde zuerst mal geau anschauen ob es die 60 oder55 gr geschintten worden ist am welle.

Dann: nur die innere durchmesser ist zu beobachten, und dann einfach am ende, schlichten je 0.02 mm machen mit versetz von die tiefe um 0.005mm. ( vielleicht etwas kleiner weil es ein 55gr ist)
Damit schneidet er nur an einen seite des flankes.
Und dann einfach gegenteil dabei zum passen.

Weil es ein gehartes teil ist, ist m nicht genau so wie die theoretisches abmass wie im tabelle.

Auch mal bestens Toolox 33 stahl
. Ist ja so um 40hrC
Oder 36nicrmo6.
Vergütet.

Gruss
V
Vincent, Not sure what has gone wrong with your keypad, but this is just a load of indecipherable gobbledygook!
 

peter holmes

Well Known and Active Website User
VOC Member
Tim, I would like to think that Vincent and I share a similar sense of humour, ever since I first met him and he asked me if I knew what is brown and twists, when I said I had no idea he pinched (there is no easy way to say this) my nipple quite hard and twisted it, I was not overly offended and I doubt that Vincent is by my comment.
 

vibrac

Well Known and Active Website User
VOC Member
Thanks Pete
My Bilingualism extends to knowing Araf on the road in Wales is welsh for slow (I dont know what Arabs make of that as Araf in Arabic is some sort of purgatory between Heaven & Hell, not quite what you want to see on the mountain road to Aberystwyth)
 

erik

Well Known and Active Website User
VOC Member
Vincent dein Deutsch ist ganz gut ,aber doch noch nicht ganz perfekt.Deshalb hat google translate da Schwierigeiten. Gruss Erik
 

powella

Active Website User
VOC Member
Hi

What you need is one of these .

Nice new Cylinder Head Nuts have a 55 deg angle BUT will not fit onto used or old Cylinder Head Studs since these will have stretched over years of use to 60 Deg on the thread - been there - done that _ burned the T Shirt .IMG_1146.JPG
 

Bill Thomas

Well Known and Active Website User
VOC Member
I got caught out with new S/S head nuts on old studs, I think our Trev told us to just open the hole in the nut a touch, It worked for me.
 

Magnetoman

Well Known and Active Website User
VOC Member
used or old Cylinder Head Studs since these will have stretched over years of use to 60 Deg on the thread -
That can't be the explanation for whatever problem you experienced. For 55-deg. to morph into 60-deg. would require the upper part of the threads to be stretched while the bases stayed the same, despite uniform pressure being applied over the entire thread by the nut. Are you sure you're not mistaking wear for stretch?
 

Top