Cassette lockring thread size

[CC12345678910]

Anyone know the thread specs for the lockring on a standardised shimano HG spline freehub/driver body, in this case a hope pro2 old? It seems to be a cards-close-to-chest secret if google is owt to go by.

Diameter? Pitch? Thread standard - american, english (24 or 26tpi cycle thread maybe), metric, other?

Dia. can be in fractional or decimal. I'll convert and work it all out in the end.

I've an alu 9spd freehub body coming from ebay but it's got a stripped cassette lockring thread so whilst I do intend to raid it for parts i'm curious to see if I could shorten everything to an 8 or 7spd and cut a new lockring thread. Seeing as by that point it's a pen holder anyway I see nothing to lose and something to gain.

Thanks in advance.

[forteh]

1.37“ 24tpi British cycle thread rings a bell? Or is that bottom bracket?

Shouldn't be too hard to measure the pitch and if you can grind a suitable tip on a boring bar then bob's your aunties live in lover

Failing that, phone up hope, I'm sure they'll be able to tell you.

[monkeyseemonkeydo]

1 hour ago, forteh said:

1.37“ 24tpi British cycle thread rings a bell? Or is that bottom bracket?

Yeah that's BB. Think the cassette is smaller diameter.

[CurtisRider]

8 speed is the same width as 9 speed, so you will only be able to shorten for 7 speed

[CC12345678910]

@forteh as said, 1.37 x 24tpi is BSA BB's and screw on cassette/freewheel thread.

@monkeyseemonkeydo is correct in saying that a cassette lockring dia. is a larl bit smaller.

@CurtisRider I had forgotten that. Still, the point of the exercise is to attempt to repair something that is otherwise shelf art, so a 7spd (or even smaller maybe) would be just fine.

FWIW I checked a cassette lockring with a thread guage which said 1mm pitch. So I double checked by nestling a m6x1 bolt into the freehub body i already have (the one that is going to get the salvaged parts from the fecked pro2 driver that's on the way) and that [the bolt] fits like a glove.

Just need to get the diameter sussed now.

[Luke Rainbird]

13 minutes ago, CC12345678910 said:

Just need to get the diameter sussed now.

|_____________|

'bout that.

[monkeyseemonkeydo]

1.2" x 24 tpi says this guy: http://www.bicycles.net.au/forums/viewtopic.php?t=73677

[CC12345678910]

7 hours ago, monkeyseemonkeydo said:

1.2" x 24 tpi says this guy: http://www.bicycles.net.au/forums/viewtopic.php?t=73677

Aye I found that already bud, but when using this (fairly comprehesive) tap chart http://www.custompartnet.com/tap-size-chart I couldn't make head nor tail. There doesn't seem to be (at least to me) a size that correlates to what those peeps quoted - If the dia. sounds right then the approximate TPI seems off or vice versa.  I've had the freehubs apart tonight to make up the 1 good from 2 bad so I've had the calipers out, taken (mildly!) informed guess' as to what size I'm after and ordered up a small selection of bolts and nuts in those sizes to see if a lockring threads into them.

I can only be wrong and it's cost about £4.90something to find out.

[pocoapoco]

I've machined my own lockring and the size is definitely 30.5mm x 1.1mm NOT 24 TPI. There's a 3.9% difference between those two pitches and threading a 24tpi into a 1.1mm will start getting tight after 2 1/2 turns or so.

[@simon_everitt]

Hey guys,

I'm in the process of reducing the width of a 135mm hub to 110mm single speed. I'm doing this by machining the freehub body down by 25mm. However, to finish the job I need to know the thread spec.

The info on this thread is really useful. However, has anybody established which tap to use / where to buy? Or is it a case of cutting a bespoke thread on my lathe?

Cheers.

[fastbike]

On 3/7/2019 at 11:39 AM, pocoapoco said:

I've machined my own lockring and the size is definitely 30.5mm x 1.1mm NOT 24 TPI. There's a 3.9% difference between those two pitches and threading a 24tpi into a 1.1mm will start getting tight after 2 1/2 turns or so.

I've never seen a thread pitch of 1.1mm specified.  That equates to an imperial size of 23.1 tpi. Both pitches are nonsensical on any common lathe.

However the measured, and machined size, of the many lock rings  that I have made to fit into Shimano compatible cassette hubs are 30.5mm (or 1.2") x 24tpi.  This makes sense as 24tpi is a common pitch on bikes (old school headsets, BSC [British standard cycle] bottom brackets, old school freehubs, screw on drum brakes, etc).  The reason for the non standard diameter is a side effect from the days of freehubs where the locking cog was threaded 1.375" x 24tpi.  As that was an external thread, but the cassette required an internal thread, 1.2" diameter was the size that gave enough wall thickness on the hubshell for splines etc, and enough clearance for the axle and bearings on the inside.

Regarding homemade lock rings that start to bind after a couple of turns, I suggest that either the lockring has not been made to spec, or the body has damaged threads.