peter_d

Is anyone familiar with the kind of seatpost binder bolts used on 1970's Bob Jacksons with the fastback Messina lugs? The right side of the lug is deeply recessed and the left side is threaded....it must be some kind of alan bolt arrangement but i can't find any photos of the actual bolt online.
Thanks for any info.

Chombi

If you can post up pics of the seat cluster/seatpost clamp area, we can help you better....

unworthy1

Yes it probably is an Allen pinch bolt, this style was called the "Dutch" style (perhaps they invented it, but they got the credit). Not 100% sure about Bob Jackson's practice, but many British builders who adopted this style use non-metric threaded bolts, so don't assume without checking. You might even find some that used Whitworth threaded bolts, in which case you may need to find a vintage British Motorcycle source for a bolt.

dyander

Sorry about the lousy pictures, but if this looks right, I can take it out and get some decent pictures and measurements of the bolt in the morning.

callig

I have a 70's Condor with fastback stays and what came with it was a large headed Allen bolt which I hardly think was original I would like to get one that will recess into the binding lug the head of the current one binds on the outside

Chombi

That looks like just a big allen head bolt to pinch together the split back of the lug. not really unusual.
I think you should be able to find a metric socket bolt from a good hardware store to fit and work
Before you posted your pics, I was thinking that it could also be one of those three piece wedge type pinch bolts that some bikes also have, which will be harder to find parts for.

Michael Angelo 

I would think 6mm x 1.0

peter_d

Yes this looks about right. If I can't find a replacement I think a regular alan bolt style would work if I grind down the thinner side so it'll slide into the threaded (left) side of the lug.
Thanks Dyander

rando_couche

IME, that's pretty UNlikely for a 70's vintage brit (or US) bike. Back then metric hardware was rare outside Europe (which does NOT include the UK - just ask any brit) or the far east. And on a bike from the UK, it could even be Whitworth (shudder...). So look in the SAE hardware section of your local Ace or big-box hardware store. And remember you'll need an inch-size allen wrench to go with.

SP
OC, OR
...been wrenching on 70's bike since the 70's.

repechage

I too think there is a good chance it is not Metric, and of course not SAE. Whitworth threading may not be that difficult as a bolt, (Think British car restoration) but an allen head cap screw in Whitworth may be more of a trick.

As Bob Jackson still exists, (even though the employees of the day are probably long retired) I would inquire with them. They have an active refinishing department still, so I bet they know from that work. If they have the correct fastener, buy it and pay the postage.

peter_d

I had checked out their website, the only seatpost binder bolt shown costs $45.00. . Next trip to the City i'll check out the hardware stores. As a last resort i could drill out the threading on the left seatpost lug, then a regular alan bolt style will work.
Thanks for the input guys.

Chombi

Oh please don't resort to irreversable mods to the poor frame like drilling out the threads on the lug.
The lug and frame designers went to such effort to provide a very clean design for the seat cluster. A bolt and nut affair will surely uglify that area if you go that direction. Give the hardware store a shot to see if you can find an equivalent to the original bolt. If you find it there, it will mostt likely just cost a couple of bucks at most. Try to find one that is either stainless steel or cadmium plated. Do not get a blued/parkerized one as it will rust almost as soon as you install it.

peter_d

Hi Chombi, I wouldn't resort to a regular hex nut and bolt but was considering a chromed recessed alan bolt fitting. I really don't want to alter the frame so may try to modify the bolt slightly rather than the frame.

repechage

Forget the website, send them a real letter with a few pictures of your frame and the internal dimension an the best guess on your part of the length you need. I think it would be they type of deal that if you sent them come cash up front in local currency, they would just pop one in the post to you. This is not like you have a brand X bike and are looking for a part.

Or, call them and follow up with an email directly to the person you talk to.

jiangshi

Take the bolt out and head to your local Ace Hardware, you may be surprised. I would guess metric, even on a Brit bike. At least by taking a trip to the hardware store, you will be able to tell for sure what the threading is.

Citoyen du Monde

My Jackson tandem has the same bolts both front and rear. It is NOT metric. Whether it is SAE or whitworth I am not sure. I checked my triplet too and it too uses teh same bolts for all three seatposts. I remember back in the 70's I had to find an SAE allen key specifically for the tandem.

Chombi

If it is indeed SAE threaded, the OP will be in good shape as it's easier to find SAE Allen headed bolts in hardware stores here in the US....

oddjob2

Spend the extra $2 for stainless steel!

peter_d

I've tried a few SAE seatpost bolts and all are too tight. It may be Whitworth but I thought Whitworth threads were quite coarse. According to one online source Bob Jackson built their 531 SL frames out of metric sized tubing so maybe they used metric fasteners also. This frame is very light so it may be SL. I'll pick up a few metric sized bolts this week and see if any fit.
Thanks again.

Should mention the frame has been back to the factory at some point for extra braze ons and a repaint so no frame stickers.

unworthy1

it could be an example of a BSC (British Standard CYCLE) bolt which is considered a sub-set of Whitworth standards but reserved for bicycle and motorcycles. It differs from the Whitworth threaded fasteners used in auto and shipbuilding specifically by the 60° thread angle used (compared to 55° standard Whitworth) and a finer thread pitch (usually 24 or 26 TPI).
If I was betting this is what I'd put my money on.
Since British motorcycles also used this threading, and employed many more Allen-head bolts in use than bicycles, I'd search your LMS (Local Motorcycle Shop) for a bolt. Or look on-line.

oddjob2

Metrics have fine thread and course, so the pitch can be different.

peter_d

Aha! This sounds very plausible. Thank you.

peter_d

https://www.retrobike.co.uk/forum/dow...e.php?id=74479

Not what i was expecting on such a slick looking lug, basically a knurled nut and bolt.

JohnDThompson 

I like that "Cinnetti Italia crown" as well...

ColonelJLloyd 

Gripfast?