May 23 2009
My great-grandfather was a machinist. As a small girl I would watch in awe as he cut through large hunks of iron or steel, cover my ears when he mauled aluminum bar stock over an anvil that was bigger than I, and be amazed as he built beautiful objects from brass. But I never warmed to metalworking. I saw metal as cold, inanimate, slightly intimidating. Until I became a mountaineer, that is. Then I had to learn about metal in order to keep my ice tools and pitons in top shape. I went on to become a geologist, and came to appreciate metal even more as I learned about it in its elemental state. But I’ve never been a metalworker like Pop. Still, I love bikes. And bikes—my bikes, at any rate—are metal. Two are steel and the other is aluminum alloy. So when something needs doing on my bikes, I like to be able to do it, whatever it is.
Today the time had come to do something about the seatpost on my Long Haul Trucker. I’ve sunk it into the seat tube as far as it has to go to give me the right seating position. Most of the time. There are times when I’d like it to sink a smidge lower, like, for instance, when my hip bothers me. No problem you say? Just drop the seatpost a bit, right? Shouldn’t be any problem, but for one thing—the top waterbottle braze-on on my seat post. Its hidden interior self imposes a stricture in the seat tube, and so I cannot drop the saddlepost beyond it. Here’s the seatpost aligned with the seat tube to show what I mean:
What to do? Cut an inch off the saddlepost, that’s what. Cutting an aluminum or even a steel saddlepost doesn’t need to be a terrible hardship, and it’s certainly not an intellectual challenge. But you need tools. Just ask my great-grandfather. While a determined and capable person can fashion metal using little more than a file and a hacksaw, the job is made easier and the result more satisfactory with the right tools. Here’s a list of the tools I assembled for the job:
• Black & Decker Workmate®
• Portable Vise
• Cutting Oil
• Cutting Guide
• Deburring Tool
• Safety Glasses
I took the job outside so metal dust would disburse into the gravel:
I covered the saddle with a plastic grocery bag to keep metal dust away, and rolled a heavy paper bag round the seatpost for padding and to avoid scarring the finish. I tightened the ‘post in the padded vise, but tightened the jaws only enough to hold the ‘post tightly, and not so much that the ‘post would be crushed. To make the cut square, I clamped a “Nashbar Steerer Tube Cutting Guide” onto the seatpost with the guide slot aligned over the place where I’d cut.
The guide slot is wide enough to permit the hacksaw blade plenty of room for maneuver without binding:
With the seatpost clamped and the cutting guide in place, the hacksaw had to be prepared. I placed droplets of cutting oil along both sides of the blade, then started the cut.
With the blade at an angle, I started the cut until the blade began to sink into the alloy ‘post, then leveled the blade and cut with long, deliberate strokes, holding the front of the saw frame with my left hand. Progress can be gauged by taking a gander from the end of the seatpost:
You can see the cutting guide clamp holding the seatpost from the top (it’s black, and in the middle top inside the cutting guide’s mouth). Note the metal dust and flakes—you don’t want any of them in your eyes, so safety glasses (or prescription glasses) will help keep your vital orbs safe. This isn’t a job for a windy day, either. In the fullness of time, the cut end falls to the ground and the hard part of the job is over.
It’s a clean cut:
Yep, I said a clean cut, though the cut edges require dressing before the job is over. That’s where a deburring tool comes into its own:
Drag the deburring blade around the inside and outside of the seatpost, peeling off the burrs and creating a smooth beveled edge inside and out. A swipe with a clean rag finishes the cleanup.
We’re not done yet, though. Now comes the rest of the cleanup. I deburred and cleaned off the stub of seatpost just in case it might be useful for something someday. Then the saw blade had to be cleaned:
With that done, the tools had to be returned to their proper places and the work bench folded up for storage. The final step is easy—replacing the seatpost and saddle, tightening the seatpost clamp, and going for a ride!