karldub

The bolt head hex grip on my seatpost clamp bolt is broken, so there is no grip for my hex key to screw it out (see pic below).


I've already ordered a replacement clamp bolt, but do you have any ideas on how to get the screw out before I try something that might makes things worse? Some ideas:

1) Drill a metal drill through the bolt head to destroy the bolt altogether - difficult because the bolt is thick
2) Try to saw the bolt off - difficult since it's so thick
3) Any other way to "get grip" in the bolt for unscrewing?

Cheers!

seypat

Try an Easy Out screw extractor first.

3Roch

If it were me I would use a dremel cutoff wheel to cut the bolt(carefully) via the slit in the seat post. You could also use a hacksaw blade but would need to keep the bolt from turning
ps be sure to stuff something into the seat tube before cutting to keep chips out of bb and clean tube out afterwards so you don't seize the seatpost

79pmooney

Can you grab enough of the center portion of the bolt with needle nose vice grips and simply unscrew the nut? If the nut won't unscrew, then hold it with an Allen key and hacksaw as suggested above.

thumpism 

Is the bolt actually broken or is the hex portion merely rounded out? If the latter, you might be able to drive in the next larger size hex (either metric or standard) or a Torx bit.

thook

then you ruin a good tool....unless you have plenty of spares. it certainly works, though!!

a number of viable options here, but i'll throw in another. grab the female bolt within the slit using needle nose pliers or vice grips and use a reverse drill bit on the head of the male side

Mr. 66

VIse grips on the one that has issue, there's enough grab on.

oneclick 

Here are some options, in order of risk-of-damage:

a) grind a hex key of the proper size flat, so you get sharp corners at the end. Drive it deep into the socket, there may be enough of the hex left down there to grip. If the hex does not work, try with a torx bit if you can find an appropriate size (as mentioned above).

b) use a dremel cutoff wheel or hacksaw to cut the bolt in the plane of the seatube slot. This will take time, but you are not likely to wander far enough to damage the ears.

c) use a vice-grip or similar pattern to grab the outer edge of the screw head (as mentioned above).

d) use a dremel cutoff wheel to cut a slot in the face of the screw head, then use a flat-blade screwdriver on it. You must be careful not to cut into the ears.

A while ago a friend turned up with a bike she was to ride the next day in an event, seat at the wrong height, and the socket-had screw had rounded as yours - plus the screw was in a counter-bored hole so the head was flush. a) worked, and after that I that I made a little spacer so the head of the (longer) replacement screw would always be proud of the hole. A socket-head capscrew in a counterbored hole is about as intelligent a design element as seatpost flutes.

thook

what's wrong with seat post flutes? (not a loaded question )

himespau 

I have so many cheap hex keys that came with various pieces of cheap furniture that I can't bear to throw out that I'd probably sacrifice one by trying to JB Weld it into the slot and use it to hold that end.

karldub

Great input. Just ordered a pair of vice grips and a set of bolt extractors and left hand drill bits so in a few days I should have some options to try out.

oneclick 

Weaker and wetter.

Same as internal cable routing, nothing but trouble.

Hobbiano 

I doesn't seem like it could be very tight since there's no seat post to tighten it up against.
Anyway, I think a small pair of vise grips should work, and if not just cut it.

merziac

Not on your life.

Steve B.

This

I stripped a L crank bolt once, used a Dremel to carve a slot, used a large flat bladed screwdriver to loosen the bolt. I got lucky, it worked.

repechage

too shallow I think.

I would try a slightly snug or oversized Torx bit,
buck it up, tap in I and purchase on the 1/4” end of the torc bit.
with a Kroil application first

3Roch

+1

dedhed

[QUOTE=onyerleft;22199085]Here's another option: take it to a business that specializes in bicycle repairs (aka a bike shop). /QUOTE]

Kinda new to this C&V crowd aren't you?

The major shop here says this

Special Notes

Some bicycle styles or repairs require additional work and are therefore subject to additional charges:

• Recumbents, tandems and specialty bikes
• Older bikes, department store bikes or bikes in poor condition
• Hydraulic brake maintenance
• Insurance or accident estimates

verktyg 

Couple of things to consider...

Those seatpost bolts are usually made of through hardened alloy steel with a Rockwell C (Rc) hardness of 45 Rc or more. The OPs' is stamped Cro Mo meaning Chrome Molybdenum alloy steel like 4130.

Most "hardware store" i.e. cheap drills are made of carbon steel hardened up to ~60 Rc.

But... when carbon steel reaches ~400° F it looses it's hardness and becomes useless. Commercial industrial quality drills are made of "high speed" alloy steels with hardnesses from 60 Rc to 62+ Rc. The benefit of high speed steel is that it will maintain usable hardness up to 1000° F.

A problem trying to use a drill in that stripped out hex hole is that it's likely going to grab and chip or break.

An "easy-out" or screw extractor isn't going to be of much use either because there's only going to be about 3mm-4mm length of "purchase" for the tool to dig in and grip the screw head. They work best with longer engagements.

Another point, many seatpost bolts have a small tab that fits into a small slot in the lug to keep the non drive side part from spinning during tightening.



Vise Grips make thin long nose pliers that will fit in the space between the "ears' on the lug but they wont do much good unless you can grip the right side threaded part of the bolt and try to turn it. The left side wont turn because of the tab. Also there is not enough exposed surface on the bolt head side to grip. See OP's photos below.



What to do? What to do? What to do?

If a drill will cut into the bolt head, by using increasing larger dills enough metal can be removed so the the head will pop off. Easy way, Home Free!

Next thing would be to take a Dremel tool with about a 1/4" carbide burr or a mounted abrasive point and grind through the bolt in the center of the lug ears. As some one mentioned above, unless the BB is going to be removed, use something in the seat tube so that the metal chips and grit doesn't get into the bearings.

Cause of the problem???

Usually happens with cheap of worn out hex keys (Allen wrenches).

One of those never ceases to amaze me things, folks who spend hundreds of dollars on the best components and not use good tools - bike shops too!

Quality hex keys are made hardened steel that resists wear and most importantly, they're accurately sized to fit the sockets.



Quality hex keys have chamfered ends that smoothly fit into the sockets. Cheap hex keys have rough corners which can keep the key from seating properly.

Hint, as the ends wear, grind up to 1mm off to keep the end size accurate.


Quality hex keys are some of the cheapest tools you can buy. Why settle for garbage?

End of lecture...

verktyg

Just one more thing that I just thought of:

Solid carbide drills for drilling hard steels. Known as Die Drills or HiRoc drills, they're strong and work well but can sometimes be expensive (read way overpriced).




Carbide tipped masonry/concrete/rock drill bits are cheap and can be used in a pinch to drill hard steel.

verktyg 

Judging from the bike shop sticker, the OP, karldub maybe in Uppsala, Sweden???

If so, those suggestions may be irrelevant...

verktyg

Prowler 

So true. This reminds me of a Park triple hex wrench, ball end, we had at the shop. The head mechanic agreed with me that we should not have it in the building. So I took it home to see if I could use it. First thing I did was cut off the ball ends. I used a cut off wheel in a Dremel tool. Wow, that steel was hard! I've cut cheap hex keys with a hack saw. Not the Park keys. I was impressed. Good tool.

I subsequently decided I did not really want a triple wrench at home. Took it back and it's still in service with little sign of wear.

I also learned, over the years, that if I buy tools that are better than I am, I always grow into them. Worth the money.

oneclick 

From the pic supplied it looked to me not as though there wasn't enough to grip, but that that was a rounded edge, and a mole- or vice-grip would tend to slip off. You could use a clamp to hold it on, and incrementally increase the pressure without moving the arrangement, causing the teeth to bite deep enough into the rounded edge that it'll have a chance at turning it before it slips off; alternatively you could use a safe-back file (or riskier: dremel) and carefully cut some flats on the screw head.

verktyg 

Been there, tried to frustratingly do that or similar efforts many times!

Latest re-invention:

\

Remember, a hammer should be the first or last tool to pick up!

verktyg

karldub

Great post, a lot of good things to pick up on there!

Sweden/Uppsala (Stockholm) it is, and from your username I'm guessing there's a connection there? Yes, good bike shops around here are hard to come by and even the bad ones charge around 50$ to change an inner tube

I couldn't wait for the tools to arrive so I adjusted the dremel advice and took a small hacksaw and carved a slot through the bolt head. Worked like a charm in this case since the bolt itself wasn't really stuck.