Boring out a pushbike saddle tube.

[Kram]

So the hole needs to be 26.2 but is currently 25mm ID down to 7" deep, and the 25mm bore is guiding the bit?

 

[eLuSiVeMiTe]

Go the other way. Make a drift and bang it all the way down

Edit. Missed that the inner tube still has some meat left at the top

 

[Gareth J]

The drill is following the bore of the centre tube, so actually easier than you might expect.

I'm sure you're being careful but I've had drills wander boring pipes out on a lathe. Probably due to my dodgy sharpening more than anything though.

Think I'd be going for a DIY long drill bit. With a stub of solid something as a leader in front of it to keep it on track that fits the bore of your wrong seatpost. Probably cobbled together using some bar or pipe and that tct bit seeing as you said it was really effective.

 

[Welderpaul]

without spending £££ on a 26.2mm reamer?

Adjustable reamer?

 

[bigegg]

Adjustable reamer?

£34!!!
If i have to, I suppose I'll have to.

 

[bigegg]

Go the other way. Make a drift and bang it all the way down

Edit. Missed that the inner tube still has some meat left at the top

It wont move anyway: If it wont budge with a 3kg slide hammer, i doubt it'll drift in

 

[bigegg]

So the hole needs to be 26.2 but is currently 25mm ID down to 7" deep, and the 25mm bore is guiding the bit?

Yes.
Basically.
The "unbored" part is around 5", and has a 22mm(ish) ID

 

[Welderpaul]

£34!!!
If i have to, I suppose I'll have to.

Then sell it when you’ve done

 

[nickk]

£34!!!
If i have to, I suppose I'll have to.

Then sell it on here ,perhaps get half your money back!

 

[stuvy]

90mm is the recommended seat post depth


Could you not turn a piece of ally down the sit inside and use a collar to bolt it in place?

Ebay us is the only place I can think of for a fisher unless the retro bike forum has something for sale

 

[Brad93]

Really what you want is something with a weld on shank. The. You could make a long spindle.

you could make a set of bearings to align the whole lot in the tube

 

[stuvy]

As brad said could you not tig a few dabs inside and then pull the remaining out with the bottom bracket in a vice via a dead crank arm?

 

[bigegg]

Really what you want is something with a weld on shank. The. You could make a long spindle.

you could make a set of bearings to align the whole lot in the tube

I have the germ of a plan.
10mm connector nut, drilled out to fit the shank of the tct drill + a blob of weld. That should keep everything aligned.
M10 all thread. And if I'm really lucky, some 10mm ID, 25mm OD bearings in my parts bin.

Might have to go m12 if neccessary - i i think i've got some m16 connector nuts I can grind down to make a bushing.

Thanks everyone.
Got me over the 'hump".

 

[bigegg]

I can make up a drill extension tomorrow if that helps. Is it 13mm drill chuck on the other end?

Just noticed the offer!
Thanks.
I might take you up on it if the other plan doesn't work.

 

[bigegg]

As brad said could you not tig a few dabs inside and then pull the remaining out with the bottom bracket in a vice via a dead crank arm?

I dont have a ac/dc tig.

Im going to weld the drill bit to a length of 10mm bar.

 

[mike 109444]

If you have an old steel stem that would fit then you could cut a set of teeth at the end then a hole through the other end and insert a tommy bar and hand ream it out as it's ally.

 

[bigegg]

If you have an old steel stem that would fit then you could cut a set of teeth at the end then a hole through the other end and insert a tommy bar and hand ream it out as it's ally.

Ooh.
I like that.
I still have 6 crates of bike scrap from when i was buying bike chain + sprockets from the local bike charity so i've probably got a suitable seat post in there.
And if not, a piece of 25mm CHS

 

[graffian]

I bought a frame off someone who had am interesting method of removing seat posts. He had made a pilot for an annular cutter and he bored the post out with it. I bought
a steel frame off him, with a seat post stuck in it, I didn't take him up on his offer to remove the post as I am quite a dab hand with the caustic.

To rem an ali post out of a mount vision frame, I chopped
the post off level with the top of the frame and made something like 8 slits
the full length of the post with a cengar saw. The slits were almost through
the post at the top, the post collapsed in on itself quite easily and there was not
a mark on the tube .
If I hadn't had my Cengarette I Would have used a jigsaw.
Took me about 15 minutes to make the slits in the seatpost, the Tompson Elite seatpost.

 

[bigegg]

I bought a frame off someone who had am interesting method of removing seat posts. He had made a pilot for an annular cutter and he bored the post out with it. I bought
a steel frame off him, with a seat post stuck in it, I didn't take him up on his offer to remove the post as I am quite a dab hand with the caustic.

To rem an ali post out of a mount vision frame, I chopped
the post off level with the top of the frame and made something like 8 slits
the full length of the post with a cengar saw. The slits were almost through
the post at the top, the post collapsed in on itself quite easily and there was not
a mark on the tube .
If I hadn't had my Cengarette I Would have used a jigsaw.
Took me about 15 minutes to make the slits in the seatpost, the Tompson Elite seatpost.

Recip saw blades aren't long enough: i tried.

The piloted annular cutter is basically what i'm using. It just isnt long enough.

 

[graffian]

I don't use reciprocating saw blades I use hacksaw blades in my jigsaw and cengarette.

I am guessing he put the annular cutter on an extension.

I made a cutter to bore out the aluminium shelf holding bottom brackets in, I
used parting blade inserts as cutting edges.

The cengar takes hacksaw blades without alteration. I think i altered my bosch jigsaw to take hacksaw blades,
in the 70's I chopped stainless steel engine plates out with a jigsaw far to often, at the time eclipse blades lasted far longer than anything made for the jigsaw.