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Seat post bolts - M4 x 30 capscrew jumbo head

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Seat post bolts - M4 x 30 capscrew jumbo head

Old 10-14-21, 07:08 PM
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Gnolo
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Seat post bolts - M4 x 30 capscrew jumbo head

Struggling massively to find a replacement seat post bolt for one I had to drill out on a 1992 Basso Laguna. It's an M4 x 30 socket head cap screw with oversized head, and coarse threads. Any idea where to buy real niche stuff like that online? Local fastener shops here don't have anything remotely similar... May have to settle for Philips head. Cheers!
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Old 10-14-21, 08:04 PM
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You positive it’s a 4mm? That’s pretty small for a seat post binder bolt on an italian of that period.
More typical would be 5mm.
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Old 10-14-21, 08:43 PM
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You mean the bolt for the saddle clamp? I would call around for a real hardware store, prob family owned. If you're lucky and can talk to a live wire, they should know at least what you are talking about. Or some auto shop that does Volvo, Mercs, Hondas, etc.

Or here: https://www.homedepot.com/p/M4-0-7-x...4638/204283605
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Old 10-15-21, 06:43 AM
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It is not unusual for bicycle components to have special heads on their bolts/screws, occasionally
special enough that they are unique. You might peruse the metric bolts at Mcmaster.com and
see if one of those might work. They do not have oversize heads but maybe a button head
could be adapted. eg https://www.mcmaster.com/screws/roun...d-torx-screws/
Recheck the diameter/pitch of the screw first. Mcmaster ships really fast but shipping costs can be as much
as the order for small orders (assuming you are in US).

FWIW 4M screw pitch is 0.7 for coarse, 0.5 for fine.

Last edited by sch; 10-15-21 at 06:48 AM.
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Old 10-15-21, 07:29 AM
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Will this work ?

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Old 10-15-21, 07:56 AM
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Try here. Metric Hardware, Metric Fasteners, Metric Bolts, Metric Nuts & Time-Sert Thread Repair (belmetric.com) Also this place has some specialty bolts for bikes and motorcycles but are on hiatus for now due to covid so the website isn't showing their products at the moment. Titanium Bolts, Titanium Bolt, Titanium Fasteners, Ti Bolts (torontocycles.com)
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Old 10-15-21, 10:15 PM
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Originally Posted by rccardr View Post
You positive itís a 4mm? Thatís pretty small for a seat post binder bolt on an italian of that period.
More typical would be 5mm.
Thanks for the suggestions all, will check those links out.

A 5/32Ē bolt fits it, though rattles around in there a little.

It measures 4.2mm on the calipers, so I am doubting it is even metric - some funky imperial bolt by the looks.

Thatís 3 LBSís and a hardware shop who have drawn a blank so far. Will have a poke around in the above links and some more fastener suppliers!

Hereís the assembly and the drilled out bolt in question. The bright bolt next to it is M4 (fine).


Edit: So, 4.2mm is 5/32"! Who would have thought, deep in northern Italy in 1992 😅

Last edited by Gnolo; 10-16-21 at 12:26 AM.
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