How to cut a steer tube?
#1
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How to cut a steer tube?
This is mainly what's the best tool to cut a steel steer tube. The steel is an un-named CrMo, unknown if it's heat-treated.
I figure a hacksaw with a fresh blade is the best choice (and it's what I have!), but is how many teeth per inch is best? I have a good 32 tooth blade, or should I use 24 teeth? Plus are there blade features that I should look for to make a cleaner cut, i.e. less final filing or deburring? Use a cutting fluid? or just jig it up and start sawing?
I'll make up a fixture from some scrap wood and C-clamps, mark the cut point with a small triangular file, and chamfer/clean the cut zone with a mill bastard file. I don't have a guide for a square cut, but I seem to do those pretty well by eye. In any case I can square it up by hand.
I figure a hacksaw with a fresh blade is the best choice (and it's what I have!), but is how many teeth per inch is best? I have a good 32 tooth blade, or should I use 24 teeth? Plus are there blade features that I should look for to make a cleaner cut, i.e. less final filing or deburring? Use a cutting fluid? or just jig it up and start sawing?
I'll make up a fixture from some scrap wood and C-clamps, mark the cut point with a small triangular file, and chamfer/clean the cut zone with a mill bastard file. I don't have a guide for a square cut, but I seem to do those pretty well by eye. In any case I can square it up by hand.
Last edited by Road Fan; 07-23-19 at 07:09 AM.
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If it's a threadless tube a pipe cutter will work very well.
#3
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I'll have to head down to the LHS and check those out!
I should have said, it's threadless!
I should have said, it's threadless!
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A pipe cutter works great with softer metals like Al or copper - somewhat more laborious with steel, although it'll work eventually. What's wrong with simply sawing it, with a tool designed to cut steel? The biggest challenge will be keeping the cut straight and perpendicular (this is where the pipe cutter will excel - do a light score all the way around, ensure that it meets up with itself, and succeeding deeper cuts will track the score perfectly). Last time I cut a steerer, I used an old/cheap treadless stem - clamped it to the steerer and use the top as the guide. The saw blade scratched the stem top up a bit, but resulted in a perfect cut.
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hacksaw with a good/new blade. works fine, you want to cut it pretty square but it doesn't have to be perfect. don't over think it!
If in doubt use your lbs. $20 seems like a lot for a 3 minute job but is worth it to some.
If in doubt use your lbs. $20 seems like a lot for a 3 minute job but is worth it to some.
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If its chromoly, the tube is heat treated and tempered, but there is no post weld heat treatment. There may be some post-weld stress relief (heating to below the temp for heat treatment) but mass producers (and good custom builders) have the jigs set up so precisely, and the mitering done so well that the PWSR required is minimal.
In any case, heat treatment and tempering for "bikely" chromoly doesn't leave them too hard. HRC 20-30 IIRC. A good hacksaw will work. Given how thin wall the tube is, use a fine (32 tooth/inch) blade or the tube might stick in the blade gullets. Your idea to use a straightening jig is likely a good one (depending on how well you implement it!) If this is a threaded fork you'll have to clean up the end (square it and deburr it). I'm assuming that you are cutting in the midst of the threads, and not in the unthreaded area. If the latter, you'll need to cut threads on it. You may want to have the LBS do that as the die and die holder/centering fixture is expensive for one-time use. But if you are cutting a threaded fork in the midst of the threads, you'll be well served to thread on a locknut before cutting. Run the locknut down closer to the crown than the cut. Make the cut. Clean up with a grinding wheel (to get the end square and flat) and a Dremel tool (to deburr). When that's done, unscrew the locknut to chase out the thread ends a bit. This will allow you to thread stuff back onto the cut fork more easily.
Can't recall, but I seem to remember that if you do need to cut more threads on the fork you do this before cutting. This automagically centers your die nicely.
In any case, heat treatment and tempering for "bikely" chromoly doesn't leave them too hard. HRC 20-30 IIRC. A good hacksaw will work. Given how thin wall the tube is, use a fine (32 tooth/inch) blade or the tube might stick in the blade gullets. Your idea to use a straightening jig is likely a good one (depending on how well you implement it!) If this is a threaded fork you'll have to clean up the end (square it and deburr it). I'm assuming that you are cutting in the midst of the threads, and not in the unthreaded area. If the latter, you'll need to cut threads on it. You may want to have the LBS do that as the die and die holder/centering fixture is expensive for one-time use. But if you are cutting a threaded fork in the midst of the threads, you'll be well served to thread on a locknut before cutting. Run the locknut down closer to the crown than the cut. Make the cut. Clean up with a grinding wheel (to get the end square and flat) and a Dremel tool (to deburr). When that's done, unscrew the locknut to chase out the thread ends a bit. This will allow you to thread stuff back onto the cut fork more easily.
Can't recall, but I seem to remember that if you do need to cut more threads on the fork you do this before cutting. This automagically centers your die nicely.
Last edited by WizardOfBoz; 07-23-19 at 07:58 AM.
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Depending on how much extra tube you have (and the type of bike), you might consider just stacking up some spacers, and running it as-is.
In my slower, antiquated state, I now prefer a bit more of an upright position, anyway, so it often works out OK.
On a recent project, I scored a pack of six 10mm alu spacers pretty cheap from a Amazon vendor, which fixed me right up.
Otherwise, as I understand, a hacksaw jig is the way to go, for a DYI job.
In my slower, antiquated state, I now prefer a bit more of an upright position, anyway, so it often works out OK.
On a recent project, I scored a pack of six 10mm alu spacers pretty cheap from a Amazon vendor, which fixed me right up.
Otherwise, as I understand, a hacksaw jig is the way to go, for a DYI job.
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You can use a worm-drive hose clamp (or two) as a guide to ensure a square cut with your hacksaw.
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Hacksaw and file to clean up, no pipe cutters please.
A hose clamp on either side of the cut will help guide the blade straight. Although I usually wrap some masking tape on one side of the cut then saw a groove all the way around before the final plunge cut.
Don't cut with the fork in the frame if you like your skin and the paint job.
Consider cutting about 5-10mm too long and running a spacer or two (can be above the stem for fit) until fit is confirmed. Later if the extra bothers you cut down the last bit. Andy
A hose clamp on either side of the cut will help guide the blade straight. Although I usually wrap some masking tape on one side of the cut then saw a groove all the way around before the final plunge cut.
Don't cut with the fork in the frame if you like your skin and the paint job.
Consider cutting about 5-10mm too long and running a spacer or two (can be above the stem for fit) until fit is confirmed. Later if the extra bothers you cut down the last bit. Andy
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Use the appropriate blade for the material. 18 to 24 teeth is probably right for CroMo. A finer blade should be used for crabon.
https://diyhousehelp.com/hacksaw-blade-guide
I use the guide pictured below. Hose clamps will do if you are careful. Painters tape helps to see the line on dark colored tubes.
Be sure to deburr the cut end with a little sandpaper.
https://diyhousehelp.com/hacksaw-blade-guide
I use the guide pictured below. Hose clamps will do if you are careful. Painters tape helps to see the line on dark colored tubes.
Be sure to deburr the cut end with a little sandpaper.
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Use the appropriate blade for the material. 18 to 24 teeth is probably right for CroMo. A finer blade should be used for crabon.
https://diyhousehelp.com/hacksaw-blade-guide
https://diyhousehelp.com/hacksaw-blade-guide
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#16
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Good hacksaw info from the Wiz.
Since I dont always have a saw guide the correct size, I have used masking tape wrapped around the tube for a good guide. Its up to you to make the saw go the right way.
If you replace forks often, get a guide. Its definitely worth it for less headaches to make a good saw line. The other ides that nobody is going to see it is most likely true too, if you dont saw it straight.
While pipe cutters can do the job there is a lot of crushing to make the cut, but it can score a nice line around the tube to use as a guide.
-SP
Since I dont always have a saw guide the correct size, I have used masking tape wrapped around the tube for a good guide. Its up to you to make the saw go the right way.
If you replace forks often, get a guide. Its definitely worth it for less headaches to make a good saw line. The other ides that nobody is going to see it is most likely true too, if you dont saw it straight.
While pipe cutters can do the job there is a lot of crushing to make the cut, but it can score a nice line around the tube to use as a guide.
-SP
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Glad this was of interest. A small addition: one rule of thumb states that ideally there should be 3 teeth resting on the sawed section (that is, the maximum tooth pitch should be material thickness divided by 3).
If you've ever hacksawed thin material sheeting and had the gullet catch the saw, you'll have no trouble remembering that rule!
If you've ever hacksawed thin material sheeting and had the gullet catch the saw, you'll have no trouble remembering that rule!
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When I read "tungsten steel" I was thinking of the alloy of mostly ferrite (iron), with carbon, tungsten and other elements. Tungsten is added to steels used for cutting to give better "red hardness". That is, to allow a bandsaw blade or drill bit or a lathe cutting tool to remain sharp even when they're heated to red hot by the cutting process. This class (tungsten and other alloys) of alloys are called high-speed steels. You don't need tungsten steel's red hardness in a hand saw and its expensive. So most hacksaw blades are not tungsten steel.
Park hacksaws come with a 32tpi bimetal (not tungsten steel) blade. But Park's carbon-cutting blade is not tungsten steel. In fact, very few hand hacksaw blades (I could find none) are tungsten steel alloys. Park's "tungsten steel" is a steel blade bonded to tungsten carbide grit. Tungsten carbide (a chemical compound of tungsten and carbon) is a much different animal (way harder and more wear-resistant, for example) than tungsten steel alloy. You make cutting tools like drill bits and such with tungsten carbide by embedding very fine-grain carbide in a cobalt matrix. These bits can cut hardened steel (and even high speed steels) due to their hardness, strength, and ability to withstand heat.
The problem with the Park blade and aluminum I'm guessing is that aluminum gets scooped out by the carbide grit and doesn't clear - it sticks to the blade in the small recesses between carbide grit particles. So the blade gets gummed up ("blinded") by the aluminum and ceases to work. But with carbon fiber or steel, the small cut chunks don't stick to the blade and so you can exploit the tungsten carbide's hardness and wear-resistance.
I'd use the Park blade with CF. I'd probably use a normal bimetallic 32tpi hacksaw blade with steel, and definitely with aluminum. At least for all things bike related.
Last edited by WizardOfBoz; 07-23-19 at 12:50 PM.
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#19
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Thanks, all! I'm only doing one fork at the moment, maybe a second one someday. The steerer is steel, so I'll stay with 32 tpi to maintain smooth saw action. I'll use a hose clamp or two to guide the saw. That all should help a lot! I think I'll measure three times, add 5 mm, then cut once, and fix it if wrong. For a steel steerer it looks like my hacksaw blade does not need to be any special alloy.
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I cut my steerer tube 3 times, and it's still too short.
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This is what I've done with carbonfiber steer tubes. I've never used any sort of guide. I just put masking tape around the tube, make a nice squared line around it and follow the line carefully when I cut. If I were doing this several times per year, I'd make or buy a cutting guide. But for the three times I've done it in my life in the past 10-15 years, the way I do it has worked fine. I might have to square it up a little with a flat file, but that's easy enough. It's not a complicated or difficult DIY Just be careful.
Last edited by Camilo; 07-24-19 at 12:26 AM.
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This is mainly what's the best tool to cut a steel steer tube. The steel is an un-named CrMo, unknown if it's heat-treated.
I figure a hacksaw with a fresh blade is the best choice (and it's what I have!), but is how many teeth per inch is best? I have a good 32 tooth blade, or should I use 24 teeth? Plus are there blade features that I should look for to make a cleaner cut, i.e. less final filing or deburring? Use a cutting fluid? or just jig it up and start sawing?
I'll make up a fixture from some scrap wood and C-clamps, mark the cut point with a small triangular file, and chamfer/clean the cut zone with a mill bastard file. I don't have a guide for a square cut, but I seem to do those pretty well by eye. In any case I can square it up by hand.
I figure a hacksaw with a fresh blade is the best choice (and it's what I have!), but is how many teeth per inch is best? I have a good 32 tooth blade, or should I use 24 teeth? Plus are there blade features that I should look for to make a cleaner cut, i.e. less final filing or deburring? Use a cutting fluid? or just jig it up and start sawing?
I'll make up a fixture from some scrap wood and C-clamps, mark the cut point with a small triangular file, and chamfer/clean the cut zone with a mill bastard file. I don't have a guide for a square cut, but I seem to do those pretty well by eye. In any case I can square it up by hand.
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The price usually includes: taking the bike in, doing the paperwork if the owner won't wait on site for the job to be finished (or if it can't be done right away).
Removing the fork from the frame - which requires removing the bars and the front brake.
Cutting it, filing the cut to be clear of any burrs.
Returning the fork, bars and the brake.
Setting up optimal headset bearing preload.
Checking whether it all works (disc brakes with QR wheels often require some fine tuning to avoid any "scratching").
So, not really a 3 minute job.
I'm all for buying the needed tools and doing it yourself, properly.
Like all other DIY stuff: it makes one more skilled, which helps with being more self-reliant, in case of any roadside (emergency) repairs, not having to leave the bike at the shop (when there's peak season rush).
But if doing that for someone else, doing it properly and taking the responsibility in case anything is done wrong, I think 20 $ is a fair price.
For the effort, knowledge, responsibility and the time needed.
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When i was looking into getting mine cut I walked into the shop forks in hand marked. All they had to do is put in jig and cut away. For $10 I would have said go ahead but for 20$ was just too much. Its all in what you’re content with
1 $ for a hit with a hammer, 99 $ for knowing where and how to hit it...
The price usually includes: taking the bike in, doing the paperwork if the owner won't wait on site for the job to be finished (or if it can't be done right away).
Removing the fork from the frame - which requires removing the bars and the front brake.
Cutting it, filing the cut to be clear of any burrs.
Returning the fork, bars and the brake.
Setting up optimal headset bearing preload.
Checking whether it all works (disc brakes with QR wheels often require some fine tuning to avoid any "scratching").
So, not really a 3 minute job.
I'm all for buying the needed tools and doing it yourself, properly.
Like all other DIY stuff: it makes one more skilled, which helps with being more self-reliant, in case of any roadside (emergency) repairs, not having to leave the bike at the shop (when there's peak season rush).
But if doing that for someone else, doing it properly and taking the responsibility in case anything is done wrong, I think 20 $ is a fair price.
For the effort, knowledge, responsibility and the time needed.
The price usually includes: taking the bike in, doing the paperwork if the owner won't wait on site for the job to be finished (or if it can't be done right away).
Removing the fork from the frame - which requires removing the bars and the front brake.
Cutting it, filing the cut to be clear of any burrs.
Returning the fork, bars and the brake.
Setting up optimal headset bearing preload.
Checking whether it all works (disc brakes with QR wheels often require some fine tuning to avoid any "scratching").
So, not really a 3 minute job.
I'm all for buying the needed tools and doing it yourself, properly.
Like all other DIY stuff: it makes one more skilled, which helps with being more self-reliant, in case of any roadside (emergency) repairs, not having to leave the bike at the shop (when there's peak season rush).
But if doing that for someone else, doing it properly and taking the responsibility in case anything is done wrong, I think 20 $ is a fair price.
For the effort, knowledge, responsibility and the time needed.
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