Advice on Cutting Seat tube

kand

Likes Dirt
My dropper post is too long. I need to cut the seat tube by about 12mm so I will have the correct leg length from pedal to saddle.
Needing advice on how to make sure a get a straight cut on the same angle as the seat post is.....aka: what could I use as a guide? I'm hoping to do it with a pipe cutter....OR I'd rather go to a local machine shop at Thornleigh, Sydney as I'm pretty hopelss with tools plus a good quality pipe cutter will set me back $75
thanks

357539
 

moorey

call me Mia
I just cut by eye. Could use a pipe cutter. Then I drilled a hole a about 10mm down and cut a slit with the hacksaw. You need the hole to stop a crack forming.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
I used the bottom of the seat clamp to scribe a cut line into the tube, then remove the clamp and use a grinder with a narrow (alloy cutting compatible) disc installed to do the cut. I get neat enough results with a grinder and a quick deburring, but hacksaw and file will get you equally good results just take a little longer.
 

ozzybmx

taking a shit with my boobs out
I cut one on one of the kids bikes, it was about 40mm long and I needed to take 15mm off it.

I locked my verniers in at 15mm, then scribed a line around on the paint, lopped it off with a 0.75mm cutting disc on a 100mm grinder. Then cut a 20mm slot at the back 'carefully' to avoid the grinder digging in and kicking forward onto the front side. File and tidy the edges and a little bit of galv-it on the bare surfaces.
 

rowdyflat

chez le médecin
Lay bike down . I would just draw a line with a marker and follow it like beeb said with a narrow blade on a grinder or can use hacksaw better working vertically.
I presume it is aluminium alloy and that there are no obstructions in the seat tube further down.
Are you sure it would nt be easier to get the right dropper ?
 

kand

Likes Dirt
I used the bottom of the seat clamp to scribe a cut line into the tube, then remove the clamp and use a grinder with a narrow (alloy cutting compatible) disc installed to do the cut. I get neat enough results with a grinder and a quick deburring, but hacksaw and file will get you equally good results just take a little longer.
that sounds like a goer....thanks
 

kand

Likes Dirt
if you do cut it yourself, remember to video yourself.

No way.....

Personally I'd be looking for a new dropper before chopping the frame.

nope...staying with what I got

Are you comfortable that once you chop the seat tube you can fully insert the dropper ?

Then I'll be posting on the fxkwits forum..LOL
 

kand

Likes Dirt
I cut one on one of the kids bikes, it was about 40mm long and I needed to take 15mm off it.

I locked my verniers in at 15mm, then scribed a line around on the paint, lopped it off with a 0.75mm cutting disc on a 100mm grinder. Then cut a 20mm slot at the back 'carefully' to avoid the grinder digging in and kicking forward onto the front side. File and tidy the edges and a little bit of galv-it on the bare surfaces.

That's it...I have verniers! Always fancied a dremel and xmas is upon us....thanks
 

kand

Likes Dirt
Lay bike down . I would just draw a line with a marker and follow it like beeb said with a narrow blade on a grinder or can use hacksaw better working vertically.
I presume it is aluminium alloy and that there are no obstructions in the seat tube further down.
Are you sure it would nt be easier to get the right dropper ?
yep, aluminuim, no obstructions.....staying with current dropper.....it's cordless. I think it uses blue tooth to communicate. And my bike has no provision for internal cable routing, plus I still use a front der.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Then I drilled a hole a about 10mm down and cut a slit with the hacksaw. You need the hole to stop a crack forming.
^^^ Above all, this is the most important thing ^^^

Ain't nobody got time for a cracked seat tube!
 

T-Rex

Template denier
My dropper post is too long. I need to cut the seat tube by about 12mm so I will have the correct leg length from pedal to saddle.
Needing advice on how to make sure a get a straight cut on the same angle as the seat post is.....aka: what could I use as a guide? I'm hoping to do it with a pipe cutter....OR I'd rather go to a local machine shop at Thornleigh, Sydney as I'm pretty hopelss with tools plus a good quality pipe cutter will set me back $75
thanks

View attachment 357539
Put an automotive hose clamp around the seat tube with the top edge of the clamp exactly where you want the cut to finish. The clamp will square up perfectly to the seat tube. The top edge of the clamp becomes your cutting guide, cut, grind and file your way down to it and you should be able to achieve a perfect finish. You will need to rotate the clamp to finish the area adjacent to the worm drive.
 

kand

Likes Dirt
Put an automotive hose clamp around the seat tube with the top edge of the clamp exactly where you want the cut to finish. The clamp will square up perfectly to the seat tube. The top edge of the clamp becomes your cutting guide, cut, grind and file your way down to it and you should be able to achieve a perfect finish. You will need to rotate the clamp to finish the area adjacent to the worm drive.
Good advice...thanks....I can even use a hacksaw now!
 

Plankosaurus

Spongeplank Dalepantski
The pipe cutter idea works ace on bars, steerers and seat posts, not sure you'd have the same success with a frame though. Might be ok if you're cutting below the clamp slit, but that'll cause you all sorts of issues if it needs to cut over it.

If you use a hacksaw, make sure you have a fine tooth count, it'll take longer but you'll cut smoother. And also be careful not to cut into your hose clamp guide, if anything cut slightly above it and file it down.

Sent from my G8441 using Tapatalk
 
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