I need to cut a 0.5 mm brass tube. Should I use a knife, a razor saw, a nipper, or something else?
Hello!
I used a little triangular file to cut a slight groove around the tube and than break it off and file the edges even. Works even better to grip the tube to be cut in my motor tool instead of a drill bit, turn the motor on, not too much revs, and then just put the file to the rotating tube - something like a lathe - to make sure the groove is nice, straight and even. Hope it helps - good luck and have a nice day
Paweł
I used a little K&S tube cutter - link below to it on Amazon - your local hardware store may have something similar. The K&S cutter is perfect for the sizes of styrene and brass I use in modeling. 
I second the tube cutter. I found a small one at the local hw store and have used it for metal, styrene and PVC.
.5 mm. That is easily cut with an exacto by rolling it on your cutting mat while lightly pressing down. Don’t try and cut through it. Just score a line. Then take a small plyers and snap it off right on the line. You will get a clean cut each time. Allbion alloys has excellent YouTube vids on this.
I use an abrasive disk in my Dremel moto tool. It cuts tubing like butter.
I have a K & S cutter, but I only use it for the larger diameters, quarter inch and up. For the small stuff I use the “score with Xacto” method. One caveat with that though. You need to hold the knife blade exactly perpendicular to axis of tube. Otherwise you will scribe a helix and it will not break when you try.
Although I have a bunch of files and a Dremel, I’m very interested in the K & S cutter. Does it also cut brass rods? If so, it’s a no brainer to order one.
K & S tube cutter- “Aye, that’s the ticket, Laddie!”
I have another brand, same idea. Never use a saw and miter box again.
A tip- if you plan to telescope tubes inside of each other, do it first, then cut the larger one over the smaller one. Any time a tube cutter is used it reduces the inside diameter, which makes later tight fits a pain.
Hobby Lobby has the K&S tube cutter. About $4.50 with coupon.
Its not very robust but it gets the job done. Except for the blade its all plastic. If you cut lots of brass you might want something more heavy duty.
This cuts up to 5/8" in diameter. Also cuts aluminum and copper.
One hint on using this don’t try to cut through the whole tube in one turn. Make several turns, each time twist the knob to advance the blade a little bit deeper.
For telescoping tubes, if you combine the tubes first, the scoring method will not work. I do them separately, but the IDs all match common drill bits. I merely ream cut end with the proper drill.
Ditto ! Best little tool I ever bought ! Works great on brass , aluminium and steel as well as copper , cast acrylic( Very Gentle here ) and regular styrene plastic ( like Evergreen tubing ) P.S. You can get a handy all metal one at Harbor Freight too .Doesn’t cut quite as small though .
Hello !
Hey Mits .You just pointed out something that anyone whose used any tubing cutter knows . Do Not try to cut through on the first pass . Watch a plumber cutting tubing .They do it just like you said !
Respectfully, not true. The trick ids to take a little longer, go slower, and move the cut as close to the end of the inner tube before snapping it.
How do the inner tubes get scored, if you only score the outer tube?