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thin brass 7mm tube - how best to cut to length?

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  • #16
    Originally posted by Fasturn View Post

    Exacto makes a small saw, but I would re- vist the lathe. Grind your parting tool extra thin at the end. Maybe .025 wide. My guess is your tool has too much presure to make a clean cut.

    And yet, the blades i mentioned are only . 012 thick
    25 miles north of Buffalo NY, USA

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    • #17
      Have you collets so co can hold it ok? Just grind a very narrow parting tool of hss, zero rake and stone to a razor edge and they'll part right off. nickel, those saws might work, but they tend to grab in brass, not much fun imo. Maybe some hero will offer their anecdotal exception, but with brass, zero rake and super sharp make for easy machining. emphasis on the super sharp.
      Last edited by Mcgyver; 07-28-2021, 01:31 PM.
      in Toronto Ontario - where are you?

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      • #18
        This is what pen makers use to cut the brass pen tubes
        https://www.pennstateind.com/store/MLCUTOFF.html
        they also sell the blades separately
        https://www.pennstateind.com/store/TUBESAWB2.html
        Sole proprietor of Acme Buggy Whips Ltd.
        Specialty products for beating dead horses.

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        • #19
          A Dremel with cutoff disk held in the lathe tool post will cut the parts off cleanly. Use a pick or something for the part to fall onto so it doesn't get lost.

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          • #20
            Originally posted by gzig5 View Post
            A Dremel with cutoff disk held in the lathe tool post will cut the parts off cleanly. Use a pick or something for the part to fall onto so it doesn't get lost.
            You must have missed this part:
            Originally posted by metalmagpie View Post
            ...
            I tried chucking it in the lathe and cutting it with a Dremel with abrasive wheel. I was quite surprised at how poorly that worked. ...


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            • #21
              I'd use (and have used) one of the Warner parting tools and a thin HSS insert, probably the 1/64th inch size. Nikole makes the same inserts in carbide and those are available from most machine tool suppliers.
              Mike Henry near Chicago

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              • #22
                If you chuck your dremel with cutoff wheel the three jaw in your lathe and make a simple fixture to mount on the compound with a hole to feed the tubing into and a stop for length you can use the crossfeed to advance the tube into the cutoff wheel to make the cut. Obviously lock chuck and carriage once set.

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                • #23
                  I would go for a collet gently tightened and try a 1.6mm, 1/16" cutoff for aluminium close to the end of the collet. Tube won't be free cutting, so that could pose problems however you cut it.

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                  • #24
                    Originally posted by Rich Carlstedt View Post
                    You want to cut the tube from inside to outside , for maximum support
                    Put it in a 7 mm collet and extend the tube 1/4" beyond the collet and then using a internal cutoff tool , go in and part it off .
                    The collet acts with maximum support for the cutting forces. If the tool has a slight lead angle it will part off cleanly and leave a burr on the tube in the collet
                    That can be cleaned with a 400 grit paper block , and ready to move the tube out 1/4" again.
                    The Boring tool can be made from drill rod.
                    Your shank should be .200 diameter and the disk ( Before trimming ) about .25.
                    Here is a photo showing a similar tool . do the inside (.200 diameter )shank first !.. then face to get the thickness ! ( .010 ? )
                    Then grind back and finish with a Dremal to get the cutting edges shown .
                    The Dremel parting tool puts a nice relief behind the cut edge that allows easy stoning. The tool would then be .225 and fit in the bore
                    Click image for larger version

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                    Since its Brass you are cutting, you do not need heat treatment
                    Another advantage is the part will fall onto the shank of the tool for easy retrieval.
                    and it will be free of burrs
                    Rich
                    If I were to cut thin tubes again I would use Rich's method. It makes a lot of sense and fast and easy to make the tool. Well done Rich.

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                    • #25
                      Simple.... look for a Micro 110 "Standard - Grooving Tools - Retaining Ring - Square - Right Hand - Miniature".

                      Hold the tube in a 9/32 collet in the lathe. Use the carbide Micro 100 tool to cut from inside out. Grind a slight angle on tip of tool so burr is not left on cut-off piece, Been there, done that on small diameter brass tube. Tumble de-burr.

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                      • #26
                        I cut 6mm brass tube once with a plumbers cut off tool for copper pipe. You know, the kind you twist the handle as you rotate it around the pipe. I put a wooden dowel inside the tube to keep it from deforming. My pieces were not as short as you need. They were 15mm long.
                        Location: The Black Forest in Germany

                        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                        • #27
                          I reviewed how to make one in a earlier post , but if you want to buy, try this
                          https://www.mcmaster.com/32335A81/
                          Personally I think .018" ( .5mm ) is too wide for the work, but it's close
                          Rich
                          Green Bay, WI

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                          • #28
                            The 2 to 3 teeth in engagement "rule" for a saw is ASSUMING a hand held saw. With a hand held saw, you are moving it at a relatively slow speed and are constantly pushing it into the cut and that means down into the material being cut. If you have fewer than 2 teeth in engagement then the saw falls down when it is between teeth and the next tooth tries to take a really big bite. Then it grabs and either stops or the object being cut is distorted instead of being cut.

                            You can ignore that "rule" if both the saw and the part being cut are firmly held and if you control the feed so that the next tooth does not try to take a large bite. This also means that you must not have much backlash in the mechanism that controls that feed. Most saw teeth have a positive rake angle and will pull themselves into a cut if allowed to do so. But if each tooth is only taking the small bite (depth of cut) that it should take, then it will cut the part and not jam or distort the part.

                            I can see several ways of accomplishing this. First, the part (your tubing) should be held in a vise or clamp that is firmly attached to the machine. Second you can use either a ball screw (CNC mill) or some kind of device that limits the feed. I used a radial arm saw with that kind of device and it worked well. And third if the saw teeth are moving at a high speed, it can limit the amount of travel that they or the work piece in the vise can move between one tooth and the next.

                            This suggests a relatively large diameter saw in a Dremel style tool that is attached to the tool. That tool can be a milling machine, a lathe, or even one of those radial arm saws. One way of limiting the effect of backlash may be to tighten the gibs on the dovetail of a lathe or mill. With a significant amount of drag, the vise or the saw blade will not be able to jump forward very much between teeth.

                            And your saw should be DEAD SHARP. And DO use a cutting fluid with lubricative properties, not just one for cooling. You want the tooth to pass through the object being cut with as little force as possible.
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

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