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Thread: First try with 8"X 1/2" slitting saw,I have questions.

  1. #1
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    Default First try with 8"X 1/2" slitting saw,I have questions.

    I tryed out a 8" x 1/2" x 28T HSS that I got at a garage sale.I was Machiniing a 1-5/8 sqaure stock I think it hot roll,it came from a hitch Manufacter that was used for stingers that would go into vehicle receiver.I tryed 90 rpm but cutter was very jumpy so went to 160 and ended up at 260 rpm is where it ran smooth.I was taking about 180 thou cuts at 3" a minute feed.How many mistakes did I make?

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    First off, it's a side milling cutter, staggered tooth.
    Using CS x 4 over diameter , gives you a lower cutting speed but looks like nothing burned up.
    They will cut very rough till a few teeth are in the work, then smooth out.

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    Mild steel is what, 100sfm in a rigid setup for HSS? At 8” diameter cutter that should be ~50rpm.

    50rpm*.001”/tooth*24teeth=1.2ipm.

    You’re pretty far out of by-the-book. And a slitting saw is more like 0.020” thick, not 0.500”.
    Last edited by adatesman; 11-02-2018 at 10:30 PM.

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    Have you ever confirmed your speeds with a tachometer ? Seems awful fast for HSS to survive..
    Some call those wheel cutters, fast way to cut a keyway, some keyways.
    Last edited by 754; 11-02-2018 at 10:27 PM.

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    Quote Originally Posted by 754 View Post
    Have you ever confirmed your speeds with a tachometer ? Seems awful fast for HSS to survive..
    Some call those wheel cutters, fast way to cut a keyway, some keyways.
    It looks like aluminum to me.
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    only in texas is that a slitting saw, for the rest of us its a staggered tooth cutter for a horizontal mill. Agree with the others, too fast....rpm = 4x CS / dia. It obviously cut but running that fast is hurting the tool life I'd think substantially. You really want that with an overarm and support then you can put it to work, that's likely why its bouncing around. You could almost go as deep as wanted with on a horizontal, an inch or so, the constraint becomes what can the key handle. Anyway, what I'd do us not run it over the max of speed of say 50, and reduce feed/doc until the setup can handle it.
    .

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    Quote Originally Posted by adatesman View Post
    Mild steel is what, 100sfm in a rigid setup for HSS? At 8” diameter cutter that should be ~50rpm.

    50rpm*.001”/tooth*24teeth=1.2ipm.

    You’re pretty far out of by-the-book. And a slitting saw is more like 0.020” thick, not 0.500”.
    I thought slower would be better,side cutter it is.
    Quote Originally Posted by 754 View Post
    Have you ever confirmed your speeds with a tachometer ? Seems awful fast for HSS to survive..
    Some call those wheel cutters, fast way to cut a keyway, some keyways.
    Yes speeds are correct,it is a gearhead mill.
    Quote Originally Posted by bborr01 View Post
    It looks like aluminum to me.
    I just took out of bead blaster to remove mill scale.
    Quote Originally Posted by Mcgyver View Post
    only in texas is that a slitting saw, for the rest of us its a staggered tooth cutter for a horizontal mill. Agree with the others, too fast....rpm = 4x CS / dia. It obviously cut but running that fast is hurting the tool life I'd think substantially. You really want that with an overarm and support then you can put it to work, that's likely why its bouncing around. You could almost go as deep as wanted with on a horizontal, an inch or so, the constraint becomes what can the key handle. Anyway, what I'd do us not run it over the max of speed of say 50, and reduce feed/doc until the setup can handle it.
    What seems odd the Head or Table did not seem to quiver,I have had that happen when I really pushed a face mill taking 300 thou cuts.My mill lowest speed is 90.Maybe should not use it in vertical application.

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    From the other direction 3ipm / 260rpm * 24 teeth is a chip load of 0.00048” per tooth. That’s not cutting, that’s rubbing.

    Cutter that big without support on the other side on such a small arbor is asking for trouble.
    Last edited by adatesman; 11-02-2018 at 11:23 PM.

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    Also, it looks like you were climb milling? That’s generally a no-no, as backlash will cause it to jump around. Some mills have backlash eliminators (my Abene does on X), but typical Bridgeport’s do not.

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    Agree.

    You basically got away with murder there. I've never gotten away with anything close.

    Those cutters will slam like anything until you get to where at least one tooth is cutting at all times, which essentially means 3 teeth in the work. With a coarse tooth like that, there is a minimum depth of slot that will work well, below that the thing will slam clear through the cut.

    You were running about 500 SFM, with a chipload of about a half thou per tooth, which may be how it worked for you in mild steel that does not work harden. The 180 thou might have just barely let you get three teeth in, maybe not quite. (cutter seems to have about 30 teeth total).

    I'd want to run about 50 rpm max, and keep the 3" per minute, which would give 2 thou per tooth chipload. You could go up to a faster feed, the gullets of the cutter will take more chip, so with sufficient power, you could maybe double the feed at that depth. Deeper you could need to back the feed down closer to 3" just to keep the gullets from getting filled.

    Those cutters like to cut metal. Better to slightly overload them rather than underload them so that they rub, because rubbing will take the edge off quickly. You had to be right on the edge of that situation..... but you seem to have dodged the bullet.

    Yes, to do a deep cut with those, you typically at least need the overarm, and in some materials or feeds, you will want the overarm brace as well. With that setup, it will munch through the job quietly, making an rrrrRRRRrrrrrrrrRRRRrrrrr sound as the inevitable slight off-center changes the depth slightly at each rotation of the cutter..

    I like the overarm brace because my horizontal is a small one, many larger units are so stout they only need the brace with a gang cutter setup.

    The one thing about those cutters is that the edge of the tooth is slightly angled, which cuts down on the slamming, somewhat lowers the cutting force, and helps with keeping at least one edge in the work at all times. But some slamming is inevitable as the cut starts, because only one tooth at a time is anywhere near the work as the cut starts, and it cuts through, exiting the work before the next edge hits.
    Last edited by J Tiers; 11-02-2018 at 11:30 PM.
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