how difficult to drill out seat tube bolt?

[mr Mag00]

cannot find the thread on here it has been discussed
how much time should i set aside and how do i do it properly?

cheers

 

[mickle]

Set up the work piece so that it's comfortable and safe to work on and secure it to allow you to exert pressure without it shifting.

Choose three or four new bits in 0.5mm increments, the largest being the same as the inside diameter of the back nut.

Start with the smallest drill bit, flood the area with oil and run the drill at very slow speed, between 120 and 240 rpm. Push hard and straight on the bit. Too fast and/or too light and you'll burn the drill.

Once you are through work your way up through the bit sizes.

Don't use cheap Allan keys on your bolts in future!

 

[mickle]

Half an hour-ish.

 

[mr Mag00]

thanks
not cheap allen keys, it just will not budge

 

[RedBike]

Punch/mark the centre before drilling. It's very important that the first hole is EXACTLY in the middle of the bolt and straight.

It might be easier to just spray it the bolt with WD40 (or whatever) and then get a socket on it. Or if the bolts rounded cut a slot in the bolts head and then use a screwdriver socket.

 

[gbb]

Set up the work piece so that it's comfortable and safe to work on and secure it to allow you to exert pressure without it shifting.

Choose three or four new bits in 0.5mm increments, the largest being the same as the inside diameter of the back nut.

Start with the smallest drill bit, flood the area with oil and run the drill at very slow speed, between 120 and 240 rpm. Push hard and straight on the bit. Too fast and/or too light and you'll burn the drill.

Once you are through work your way up through the bit sizes.

Don't use cheap Allan keys on your bolts in future!

The only thing i'd add is that such small increases in drill size means the next one is only cutting with a tiny fraction of its cutting surface...and that can ( but may not) cause probems. To be fair, on cheaper bolts, you'll probably get away with it. But good quality bolts, you may struggle with such tiny increments.
As Mickle says, remember plenty of oil...
As Redbike says, ideally dot punch the middle of the bolt head.
And use the best drill bits you can buy. Cheap ones are a waste of money.

 

[MacB]

It might be easier to just spray it the bolt with WD40 (or whatever) and then get a socket on it. Or if the bolts rounded cut a slot in the bolts head and then use a screwdriver socket.

+1 lot of things can be done before drilling out

 

[mickle]

Punch/mark the centre before drilling. It's very important that the first hole is EXACTLY in the middle of the bolt and straight.

Is it though?

 

[mr Mag00]

surely siting the drill bit in the allen key recess is enough?

 

[RedBike]

Is it though?

Yes, because each larger drill bit will try and follow the path/ hole drilled by the previous. Once you get to the larger drill bits if your holes not straight and central you'll end up taking a chunk out of the frame.

 

[asterix]

Good luck!

 

[gbb]

Yes, because each larger drill bit will try and follow the path/ hole drilled by the previous. Once you get to the larger drill bits if your holes not straight and central you'll end up taking a chunk out of the frame.

Agreed, thats a very real danger.

 

[mickle]

I've (probably incorrectly) made the assumption that the bolt has a nut on it rather than screws into the frame.

Another option is to saw or Dremel the bolt in half. Once the tension is removed the threaded end will usually be free enough to unscrew by hand.

 

[MartinC]

Yes, because each larger drill bit will try and follow the path/ hole drilled by the previous. Once you get to the larger drill bits if your holes not straight and central you'll end up taking a chunk out of the frame.

+1 for Mickle. Fortunately dead centre isn't required. If you drill carefully and in small increments you can stop when the edge of the hole coincides with the side of the bolt. At this point, even though there may be plenty of bolt left, you'll have relieved the pressure on the thread and it'll unscrew

 

[mr Mag00]

it has a allen head on one end and a bolt on t'other. it doesnt screw in to the frame.

i have though about trying to but bolt in half where the frame splits but not much room B)