Posted 27 October 2023

Best tool to cut my bike seat post

I need to cut 10cm off my bike seat post, which is made of alloy. The thickness of the pipe is 2mm.

I have the following tools available to me, so would like your opinion as to which tool will do the best job in terms of getting a decent result for less work.

The seat post is made of forged aluminium.

Tools available - angle grinder, dremel, hacksaw, junior hacksaw.

I am inclined to go for the angle grinder, what do you think?

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27th Oct 2023
If you go for using a dremel or grinder make sure you wear safety goggles! Especially if using a dremel as they can be particularly dangerous as your face will be close by to the cutting wheel.
27th Oct 2023
A hacksaw will breeze through that, the initial and end cut where the blade is going through the most metal will feel slow but the rest a hack was will just flow through
Author
27th Oct 2023
Very true. Hadn't thought of that. Yes, the middle bit is going to be quite simple
27th Oct 2023
I can see a where can a get a new seat post ask coming
27th Oct 2023
If I were you I'd use the junior hacksaw. Put some tape round the post to stop it slipping.
If I were me I'd use a pipe cutter.
Author
27th Oct 2023
i don't have a pipe cutter. would a pipe cutter work on these pipes? they are designed to cut copper pipes, which may be softer than these sort of posts? i coud get a pipe cutter.

why do you say the hacksaw is best? because it gives a clean result compared to the angle grinder? (edited)
27th Oct 2023
It's easy to slip off a tube so I'd stick to the handsaw unless you have a good way of clamping a pipe.
Author
27th Oct 2023
I have a black and decker work bench, which have clamps. I was going to use that. Someone advised to wrap the tube with cloth to give a better grip, which is a good idea.
27th Oct 2023
Used a hacksaw on mine only takes a couple of minutes once you've got it started, or you could use a dremel type tool (edited)
Author
27th Oct 2023
That is good to hear. I was thinking it will take at least half an hour to hacksaw the post but I guess it won't be made of hard steel.
27th Oct 2023
I used an angle grinder. Did the job swiftly and easily, but made for a far uglier cut than I would've liked. If I can offer any tips from my experience, it's to fully commit when you attempt the cut, and, 1000%, wear robust PPE. It'll be loud AF, and red hot metal shards will fly everywhere, so wear decent ear protection, eye protection, thick clothing, and thick gloves. If you still have face masks from the COVID days, it's worth putting one of them on too. And, obviously, clamp it all as tightly as possible, so there's no chance of it flying off. Mind that the angle grinder will hit the surface with about as much force as Gerard Butler's Sparta kick, so that's what you need to clamp in preparation of.
Author
27th Oct 2023
I saw a YouTube video where the grinder cut the tube like a pair of scissors going through a toilet roll! It may be only certain types of posts will spark, the one he did didn't spark at all.

This video

youtu.be/9R3…lKM (edited)
27th Oct 2023
If you're confident with an angle grinder that would be easiest. Just a standard cutting disc but make sure you're wearing eye protection.
Otherwise junior hacksaw, will just take a bit longer.
Author
27th Oct 2023
i think the hacksaw will take a while to do but i could start off with that and see how easy it is to cut. if it takes too long, then i could switch to the angle grinder? i have all the protective tools for using the angle grinder and i have used it before to cut tiles in situ, so i am pretty nifty with it

just wondered what the advantage would be with the hacksaw versus the angle grinder?
28th Oct 2023
Just curious, why do you need to cut the post. Can't you just drop it down inside the frame to lower the seat height, or do you need it lower than that?
Author
28th Oct 2023
i bought a new bike recently and there is a design flaw on the bike there are 2 holes on the frame on the seat tube part, which have been drilled into the frame to allow accessory attachments. unfortunately these holes have not been drilled cleanly and look like they have been punched into the frame instead of drilled, so there is a small catch on the inside of the tube, which stops the tube dropping any further down beyond these two holes!

If i could get access to the inside of the frame to sand down the top hole, then i wouldn't actually need to shorten the seat post at all
Author
28th Oct 2023
update - thanks for the input everyone! I am glad I asked for opinions as it changed my mind from going gun ho and taking out the big gun to do a small job

i decided to use the hacksaw and i was really surprised how soft the metal is as the hacksaw went through it like it was a 2mm piece of plywood rather than metal! it took me longer to remove the seat from the post than it did sawing the post! i took about 10 minutes to cut the post but that was because i have never used a hacksaw before and i wanted to keep eaxmining the cut while i was cutting.

for an experienced user, this would be gone in 2 minutes. i wasn't able to get a perfect straight cut and so the bottom of the cut was about 0.5cm out from the intended line but it will do
29th Oct 2023
What a load of hassle. Sounds like Poor quality control. You shouldn't of had to do that. Could technically be classed as faulty and returned me thinks. Well glad you got it sorted easily.
Author
29th Oct 2023
i got it on clearance so i can't complain but yeah, may explain why it was on clearance!
29th Oct 2023
Has anyone ever spray painted a seat post, mine is silber but want it black. Youtube has instrcutions on how to do it
Author
29th Oct 2023
should be no different to spray paint anything else. i have never spray paint before, but i think you would need to get your technique right to get a good even finish.

not much of the seat post would be showing, so you could just take the easy option and wrap it in black handlebar tape?

temu.com/uk/…k=1