Tomm Willians

Good evening all

I purchased some low profile M5 bolts for my bottle cages only to discover that Colnago apparently used an M4 at least at this time?. I’m fairly handy with tools but have never used a tap and die set, I assume I can re-tap these holes to M5 by simply running the appropriate cutter through the boss? I’d hate to screw these up by finding out too late that it’s not quite that straight forward

BCDrums

Would seem easier to get some M4 bolts,

Tomm Willians

I’ve looked for low profile blue anodized bolts in M4 but cannot find exactly what I’m looking for.

sweeks

You'd have to drill out the bosses then tap the threads. If the frame is aluminum and the bosses are welded on, this might be possible, If the bosses are swaged in, or the frame is carbon, you might apply enough torque to cause the boss to spin. BCDrums' idea ^^ is much better.

HillRider

+1. You can't just run an M5x0.8 tap through a threaded M4x0.7 hole without taking a great chance of breaking the tap, particularly if the bottle bosses are steel. If they are rivnuts, you stand a good chance of spinning the rivnut loose and then nothing will work.

You would have to drill out the existing holes with an M5 tap drill (4.2 mm or #19 drill bit) then tap new threads with an M5x0.8 mm tap.

Buying a few suitable M4 screws will be much easier and cheaper.

krakhaus 

Ebay has some blue M4 bolt listings, but they're all in China. So, you could order those, or you could get some from the hardware store and hit them with this.

I've used it on a few things, and it looks just like anodizing if done right. Less durable, but if they ever chip, you can just do it again.

due ruote 

There’s nothing worse than having something go sideways when you knew it was a bad idea to begin with.
I would just get some stainless M4 bolts. If it makes it easier you can just think of them as placeholders.

Geepig

The tapping drill size for M5 is 4.2 mm, which is not much difference to the 4 mm thread root size of your M4, especially if you are going to have to hold the drill. You might get a nice pair of threaded holes, or you might not.

TiHabanero

If you simply store the bike with water bottles in place, then no one, including yourself, will see the bolts, and thus a potential problem has been averted. On one of my display bikes I have a "special to me" water bottle in place on the bike, and I will confirm the bottle bolts cannot be seen.

fishboat

There's probably more than a couple "silver" bolts on the bike. "Blue" must be pretty important to risk screwing up the holes in general. If they get messed up in the effort to make them M5...how's the next (post M5 re-work screw-up) bottle cage attachment going to look?

Some things matter..some don't. Put some silver M4 bolts in there, or paint the heads if you need to, and a week from now some other "thing" will capture your attention and the blue-bolt thing will be a distant, less important memory.

BCDrums

It's a lesson I have learned. This would make a good signature!

BCDrums

https://www.probolt-usa.com/titanium...4x0-50mmx12mm/

This could be a candidate.

hokiefyd 

I second that, and liked the first mention of it. You already have this feeling that you're going down the wrong road. You already know it's the wrong approach and, for some reason, you can't turn back.

When you finally do screw it up...you get this empty feeling in your stomach, that feeling where you wish you had listened to that voice that told you not to proceed..

Phil_gretz

^ interesting observation. I think that a part of maturity is having the self control to resist the impulse to simply plunge forward with a plan that you know is unsound. I'm always so proud when those moments occur, and I step back from the abyss to reconsider my way. This has come with both age and mountains of mistakes along the way, though.

macstuff 

You can't just run a larger tap into a smaller thread to enlarge it, you would have to drill the old threads out first. (machinist drill register bit). Especially since the threaded bung you're talking about is probably no more that a few mm deep. It would just tear out the old threads and mess the hole up real good. the tap would have to be held firmly in a fixture as it turns to ensure it is going in straight. A long hole to be tapped is kind of self straightening for a hand tapping job but a shallow one will Hogg out.

Re-tapping the hole is a ruined frame waiting to happen.
If they make 5mm blue bolts, the same company makes 4mm blue bolts. Maybe not the packager you got the 5mm from, but the company that actually made them. Patience and looking around for the right bolts is the answer
Worst case scenarios:
Your bolt heads aren't blue
You ruin an expensive frame

Tomm Willians

Thank you !

dsbrantjr

If by "anodized" you mean aluminum, I avoid aluminum nuts and bolts (and spoke nipples) like the plague. They are weak and liable to both stripping and seizing, especially when mated to aluminum threads.

sweeks

Thanks for that source for titanium hardware! For several years I have purchased the odd titanium bits from Toronto Cycles and have been quite happy with their products. Sadly, the site seems to be closed since the pandemic started. I've replaced a lot of bolts, brake hardware, chainring bolts and crank hardware (below) with titanium on my "winter" bike... titanium doesn't corrode!


Original stainless steel hardware on the left; titanium replacements on the right,

BCDrums

I had bookmarked Toronto Cycles a few years back, never ordered from them, but they had a great website for colored, anodized connectors. When I saw Tomm's post I looked them up and was sorry to see that they had closed during the pandemic, and maybe permanently, who knows? It must be hard to make a business from customers who order two or four water bottle bolts.