Dura ace 7400 brake caliper adjuster thread diameter

Hi, does anyone know what the thread is for the barrel adjuster on a 7400 dura ace dual pivot caliper please? M6?

Re:

Ok, so just had a look at a front brake, 7403, date code PF (June 1991). The attached photo should make self-explanatory.

The barrel adjuster bolt has a flat side and slides into the nylon cup that is shown. My digital calipers came up with 5.5. No (obvious) thread where the nylon cup sits. Took the barrel adjuster itself off and fits M6 perfectly (tried it on several Shimano brake blocks and M6 bolts to be sure).

Re:

As an aside, did DA 7400 come in single and dual pivot versions?

Thanks for that. So it looks like I've actually got the right adjuster after all and I'm missing the nylon insert. I'm guessing they're like hen's teeth!

If you can measure the dimensions from the brake accurately with your calipers, I could potentially 3d print one.

Re:

'Adjusting nut bushing', part number 84A 0700

https://si.shimano.com/pdfs/ev/EV-BR-7403-1078.pdf

Given this simply allows the barrel adjuster to move up and down the bolt without the bolt rotating to shorten / lengthen the cable suspect would not be too hard to produce a plastic part with the same effect, piece of plastic tubing, for example, and it would be virtually completely hidden from view.

Velobase shows that the earlier version of 7400 was single pivot.

If you want more detailed photos / measurements, let me know, easy to access.

Re:

I would love a couple of the inserts as have the 7400 single pivots with the inserts missing.

Re:

I’ve got both single and dual pivot versions I’d you wasn’t pictures. PM me

Re:

In case anyone has access to 3D software and a printer, here's some more detailed photos of the caliper and the bushing and some dimensions. The bush has a lip to sit in the caliper with a distinct D shape on the inside to secure the flat edge of the bolt in the caliper. In fact, something like a cut-down rawplug with a lip fits reasonably well in the socket in the caliper with the lip holding it in place and might work as a short term fix.

The dimensions of the bush are as follows, using a digital caliper:

Top to bottom 5.55 mm
The top lip is 2.53 mm from top to bottom
Widest section across the top 10.13 mm
The lower part is 7.99 mm across
The internal diameter is 5.74 where it is circular and 4.9 into the flat side
There is a slight curve in the top of the bushing into which the bearing can seat.

Really interested to know how modern technology will get on with this, wish I had access to the technology but at the moment not possible.

Good luck.

Re:

Are they the same for the single pivot, from memory (before mine broke up) they looked similar.