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Old 03-28-11, 11:39 AM   #1
AndyK 
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Cutting an aluminum steerer tube?

I should be getting my new aluminum Cinelli Experience frame this week (carbon fork / aluminum steerer). Can I use one of those tube cutters that rotate around and around the tube until it's cut?

http://www.google.com/products/catal...d=0CFQQ8wIwAw#
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Old 03-28-11, 11:43 AM   #2
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sure can
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Old 03-28-11, 11:58 AM   #3
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Tube cutter Will raise a Burr around the inside of the tube,

as said measure many times , before you cut..

You can always run with spacers above the stem, so as to get the low position..
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Old 03-28-11, 12:02 PM   #4
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I'll install the headset and stem first, measure to get the best saddle to bar drop, then cut. I'd rather use a tube cutter to get a perfectly straight cut, then de-burr if I must.
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Old 03-28-11, 12:17 PM   #5
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Correct tool for the job http://www.parktool.com/product/thre...saw-guide-SG-6

When you know how high you want it, measure twice cut once.

If it's a new build, and have no reference to how long you want it, would leave it very long, play around with spavers for a few rides, and re-cut when happy with length.
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Old 03-28-11, 01:34 PM   #6
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If you already have the tubing cutter then fine. If you don't you can get great results from using a wrap of masking tape around the tube set so it meets itself exactly. That provides a true guide line to cut the tube with a hacksaw. Cut it about a millimeter away from the tape and then file off the end down to the tape line and deburr the inside and outside edges to leave you a nice square, clean and perfect job.

I don't like tubing cutters because then often tend to swage in the last 1/8 inch of the tubing so you end up with a taper over that much length. But much of this depends on the sort of alloy that the maker used in the steerer tube.
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Old 03-28-11, 01:59 PM   #7
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The only correct answer is: NO - YOU CAN`T!!

Already had this discussion with a shop owner that thought using a hacksaw and guide was passee and a waste of time. I actually decided to let him `educate me` with a demo on a new fork, LOL

A tube cutter doesn`t cut metal - it DISPLACES it. Which means that the outside diameter within 2 to 3 mmof the `cut` areas will be too large for the stem to go onto, and the inside dia will be too deformed and small to insert a star-nut.

Of course if you insist you can always check and see for yourself!
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Old 03-28-11, 02:04 PM   #8
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Since I don't own a vice, I guess I should just bring it to a shop to have them cut it after figuring out the right height.
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Old 03-28-11, 02:05 PM   #9
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Starnut, Id say, is only a good piece to use on steel fork steerers . scratch becomes aluminum stress riser
becomes crack, becomes a break, too easily.
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Old 03-28-11, 02:20 PM   #10
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No starnut??? I thought they are fine in anything except carbon steerers?
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Old 03-28-11, 02:28 PM   #11
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Using a expanding fitting to secure the nut under the adjustment cap will do the task just fine.
and not score the aluminum steerer tube.

It's your Neck , do as you wish.
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Old 03-28-11, 02:33 PM   #12
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I never thought of the sharp steel edges of a starnut cutting into the alloy steerer tube. I guess I'll see what the headset included with the frame comes with. Maybe it will have both a starnut, and expander. If not, I'll get an expander.

Thanks for the heads up!
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Old 03-28-11, 04:36 PM   #13
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Andy in theory Fietsbob is absolutely correct. In reality - there are lots of alloy steering tubes out there with star fangled nuts in them. The wall thickness can vary considerably depending on the quality of the fork, and of course the forces on it will depend on how you drive it. From a practical point of view the nut will be above or within the area clamped by the steering stem so any real danger is minimal.

I use compression plugs myself but mostly out of principal. The notion of paying a large sum of money for a precision suspension item and then using a hammer on it just goes against my grain. I put out the extra $10.
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Old 03-28-11, 06:09 PM   #14
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While I've read of several posters who have reported successfully using a tubing cutter on aluminum or Cr-Mo steerers, in general I agree with Burton. A tubing cutter tends to leave a raised ridge on the outside of the cut and a sharp edge inside. If you are willing to file off the burrs, ok, but a fine tooth (32tpi) hacksaw with a cutting guide works much better.

As BCRider recommended a wrap of masking tape can be a suitable guide but I prefer a stainless steel radiator clamp. It provides a well defined and solid edge to guide the cut.

Finally if you leave the steerer a bit too long and add a thin spacer above the stem, having an absolutely square cut isn't as important since the spacer will provide the needed square edge for the top cap to butt up against.
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Old 03-28-11, 06:24 PM   #15
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Quote:
Originally Posted by Burton View Post
Already had this discussion with a shop owner that thought using a hacksaw and guide was passee and a waste of time. I actually decided to let him `educate me` with a demo on a new fork, LOL

A tube cutter doesn`t cut metal - it DISPLACES it. Which means that the outside diameter within 2 to 3 mmof the `cut` areas will be too large for the stem to go onto, and the inside dia will be too deformed and small to insert a star-nut.

Of course if you insist you can always check and see for yourself!
Well damn. Glad you're here to tell me this.

Will someone please tell my bike it didn't work?
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Old 03-28-11, 06:27 PM   #16
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Will someone please tell my bike it didn't work?
Glad to. What's its e-mail address?
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Old 03-28-11, 06:27 PM   #17
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While I've read of several posters who have reported successfully using a tubing cutter on aluminum or Cr-Mo steerers, in general I agree with Burton. A tubing cutter tends to leave a raised ridge on the outside of the cut and a sharp edge inside. If you are willing to file off the burrs, ok, but a fine tooth (32tpi) hacksaw with a cutting guide works much better.

As BCRider recommended a wrap of masking tape can be a suitable guide but I prefer a stainless steel radiator clamp. It provides a well defined and solid edge to guide the cut.
Even with a fine-tooth hacksaw, you're going to have to take a file to the steerer tube anyway.

Quote:
Finally if you leave the steerer a bit too long and add a thin spacer above the stem, having an absolutely square cut isn't as important since the spacer will provide the needed square edge for the top cap to butt up against.
I didn't think the top cap should be touching the steerer tube - no matter what.
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Old 03-28-11, 06:31 PM   #18
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Even with a fine-tooth hacksaw, you're going to have to take a file to the steerer tube anyway.
True, but just to smooth up the cut face but not to remove a ridge of raised metal. The problem with a tube cutter is most users adjust it too tight, particularly if the cutting wheel is a bit dull and that is what causes the displaced metal.

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I didn't think the top cap should be touching the steerer tube - no matter what.
Good point. So, a very highly accurate 90° cut isn't critical in any configuration.
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Old 03-28-11, 09:41 PM   #19
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Quote:
Originally Posted by Burton View Post
Already had this discussion with a shop owner that thought using a hacksaw and guide was passee and a waste of time. I actually decided to let him `educate me` with a demo on a new fork, LOL

A tube cutter doesn`t cut metal - it DISPLACES it. Which means that the outside diameter within 2 to 3 mmof the `cut` areas will be too large for the stem to go onto, and the inside dia will be too deformed and small to insert a star-nut.

Of course if you insist you can always check and see for yourself!
I had always used the tube cutter method on the forks I've had over the years with both aluminum and steel steerers. Never had a problem until I did the last one, a Surly 1x1 with a cromoly steel steerer. Measured, cut, filed and installed the star nut then went to assemble on the bike. The stem didn't want to slide onto the steerer, it was tight. I had to use a rubber mallet to get the stem on the steer tube. The stem can spin on the steer tube once installed but it's taught. Another steer tube and stem combo may produce different results. My experience based on Surly 1x1 rigid steel fork and older Synchos stem.

Now I see what you say about the tube "cutter" not really being a cutting tool. The diameter growth at the end of the steerer may be slight, I didn't notice it just by eyeballing, but it's significant enough to prevent my stem from smoothly sliding on.
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Old 03-29-11, 08:09 AM   #20
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Quote:
Originally Posted by fietsbob View Post
Tube cutter Will raise a Burr around the inside of the tube,

as said measure many times , before you cut..

You can always run with spacers above the stem, so as to get the low position..
The burr on the inside isn't too much of a problem. Even if you use a hacksaw, you'll need to dress the inside of the tubing. Get a deburring tool like this.

Quote:
Originally Posted by Burton View Post
Already had this discussion with a shop owner that thought using a hacksaw and guide was passee and a waste of time. I actually decided to let him `educate me` with a demo on a new fork, LOL

A tube cutter doesn`t cut metal - it DISPLACES it. Which means that the outside diameter within 2 to 3 mmof the `cut` areas will be too large for the stem to go onto, and the inside dia will be too deformed and small to insert a star-nut.

Of course if you insist you can always check and see for yourself!
A tubing cutter works but, as you say, it displaces the metal rather than cuts it. However, it's easy to file the raised ridge off. Even a saw cut will need some cleaning. If you really want to make the tube nice and smooth you should use a pipe reamer like this one. This one is a very good one but you can find them cheaper



Quote:
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Starnut, Id say, is only a good piece to use on steel fork steerers . scratch becomes aluminum stress riser
becomes crack, becomes a break, too easily.
I've never used anything but a starnut on steer tubes. I've got lots of aluminum steer tube equipped forks that have starnuts in them. Most of those are mountain bike forks too which take a lot more abuse than road bikes. Haven't had one crack yet. The top of the steer tube doesn't see all that much stress anyway. I don't think it's an issue.
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Old 03-29-11, 12:18 PM   #21
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And generally aluminium steerer tubes are a lot thicker walled than steel ones. Only perhaps on some light weight road bikes would the alloy used be so thin that I'd worry about a scratch from a star nut causing a stress riser and eventual cracking.
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Old 03-29-11, 02:34 PM   #22
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I'll definitely check out the steerer tubes' thickness, and see what Cinelli included with the bike as far as the headset and parts go when the frameset arrives.

Thanks for all the opinions and advice.
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Old 03-29-11, 07:37 PM   #23
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I'll definitely check out the steerer tubes' thickness, and see what Cinelli included with the bike as far as the headset and parts go when the frameset arrives.

Thanks for all the opinions and advice.
I believe star nuts come in various types and there is a specific size for aluminum steerers to compensate for their greater wall thickness.
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Old 03-29-11, 08:11 PM   #24
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I believe star nuts come in various types and there is a specific size for aluminum steerers to compensate for their greater wall thickness.
just use a 1 inch star nut for al 1 1/8 steer tube, it is not necessary only if the walls are really thick
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Old 03-29-11, 10:19 PM   #25
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OK I`ll bite

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Well damn. Glad you're here to tell me this.

Will someone please tell my bike it didn't work?
I`m never one to pass up on a chance to learn something new so lets trade experiences. Personally (and every shop I`ve worked in) use a guide, a fine tooth saw and a chrome file and/or 320 grit wet sandpaper to cut and finish tubing. If there`s a way to accomplish the same level of quality faster - I`m very open to suggestions.

Every pipe cutter I`m aware of thats readily available to the general public is intended to `cut` soft, thin walled copper, brass and PVC tubing. Thats why they`re in the plumbing section. I`m also well aware that tubing cut commercially for precision applications is done using very expensive motorized equipment with saw blades.

But I`m seriously interested in knowing exactly what you did youself so here`s a chance to show off that job of yours. I have three different pipe cutters here - all virtually new with cutting wheels in excellent shape, so I`m going to cut a tube using one of those pipe cutters, and cut the other end using a guide and saw, and post pictures with details of both the overall time and the level of precision.

Really don`t know what you installed your fork on or what stem you stuck on it. I do know that Thompson, Ritchey and any BMX stem I`m aware of has tolerances so tight that you`d have to remove any deformation caused by a pipe cutter. And personally I hate to have to do any more work than necessary to achieve the results I`m after.

So I`ll have photos and details up within the next day or so and people can make up their own minds. And like I said - if you actually did get superior or equivalent results faster - I`d like to SEE it. Otherwise, in theory - you could also use a hammer and chisel too if you were prepared to do all the rework necessary to recover the situation afterwards.
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