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Thread: school me

  1. #1
    Join Date
    Aug 2018
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    Panama
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    Default school me

    Hi, need some advise from the pro's . First real work on a LMS 3990 mill . Need to cut a slot in some 1 3/4 inch by 3/16 wall SS pipe . The slot will be 530 wide and about 8 inches long . I read the entire archive posts when I first signed up , information overload , do remember reading about climb milling etc but doing and reading are 2 different things and I remember by doing better . So that aside what is the best way to do this . My thinking is a 1/2 end mill then moving the table 30 thou and taking another cut . Is that the right way and if so when sitting in front of the mill does the pipe start out on the left or right side of the end mill and then when taking the 30 thou would you crank the table into towards the post out out towards yourself and then take the cut traveling back to where you first started taking the org 1/2 cut . Or would you use a smaller mill for the first cut . Thanks in advance on any ideas

  2. #2
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    Some clarification will be needed:
    1- is this slot to be from end to end, or will one or both ends be closed?
    2 - do the sides of the slots need to be on a radius, i.e. think of a pie slice wedge removed?
    3 - How is the pipe to be held?

    If the slot is closed on both ends, and the orientation of the slot sides isn't critical you can just plunge in (assuming a center cutting end mill), mill the full length, then move .030 to make the rest of the width in the non-climb (conventional) direction, or make a .015 widening cut in each direction.

    If slot is end to end, you want to make sure your holding method doesn't squeeze it shut.

  3. #3
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    Plan your operations so the last two cuts each side to size are climb cuts will give clean edges with minimal burrs.

    You have a challenge with stainless pipe. It may be sensitive to work hardening. Sharp tools, rigid machine and setup, always pull a chip (don't let the cutter rub without cutting), and cutting oil.

  4. #4
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    Hi , the cut will be from one end but not going completly to the other end
    the sides inside can just e touched up after with a grinder
    because the pipe already has a cap welded on one end I was just going to do it in a vise . I could leave the open end closed for about 1/2 inch and then just zip disc it open if need be , this is nothing fancyjust a outboard motor lock
    Can you give me a quick lesson on non climbing again. ? For example if the material starts on the left side of the cutter and I plunge in and cut , would non climbing be cutting the side closest to thr column or the outside

  5. #5
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    Can you give me a quick lesson on non climbing again. ?
    Imagine looking down on the spinning end mill (EM), and you're facing the axis of table movement or the relative movement between the EM and work. Visualize then the sharp edges will be pushing against the work if moved in one direction - that's conventional milling; if moved in the other direction the sharp edges will grab the work and tend to pull it - that's climb cutting.

    For example if the material starts on the left side of the cutter and I plunge in and cut , would non climbing be cutting the side closest to thr column or the outside
    That question can't be answered with certainty without knowing exactly what you have, because end mills differ. Some are made RH, some are made LH, with respect to both cutting AND the helix or spiral direction, not to mention upcut and downcut.

    Just concentrate on whether the sharp edge is pushing against the work as it moves, or if it is pulling itself toward the uncut portion of the work.
    Last edited by lynnl; 08-10-2019 at 01:15 AM.

  6. #6
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  7. #7
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    Imagine the cutter being a tire, if it the contact point and direction of cut is the same between the wheel and the road (workpiece), then you are climb milling.

  8. #8
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    Thank you all for the info .thanks joel for the link , bookmarked for future use also . Now for example with what I need to do , would climb milling the 30 thou on this thick of pipe be too much of a cut in 1 shot or would I need to take 2 cuts

  9. #9
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    Quote Originally Posted by panamaguy View Post
    Thank you all for the info .thanks joel for the link , bookmarked for future use also . Now for example with what I need to do , would climb milling the 30 thou on this thick of pipe be too much of a cut in 1 shot or would I need to take 2 cuts
    The reason we don't climb cut all the time is when there's backlash, it can grab the work and pull it into the cutter, sometimes messing up the work, sometimes breaking the cutter. The climb cut as to be light enough that the tables inertia prevents this. Typically I go full depth and may take off 5 thou for a finish pass. Stainless can be a pita - you have to make chips, it will work harden so not making a chip or dwelling can lead to miserable problems. Each successive path of the tooth has to advance enough go past the working surface the previous tooth left. slow everything way down so you make a chip and keep it wet. I'd probably go full depth with 1/2 end mill, then clean up the sides.

    Biggest challenge I would think is its going to be flimsy set up. Vise is no good, will just crush the work into the cutter. Clamp directly to the T slot in the mill. Still the materials could ring and bounce about like crazy which would I think make stainless work hardening more likely (but cutting slot this in ss piple is not something I can remember doing, have done steel and it can be a problem). Filling it with cerrobond would great, but who has that much of it lying around?
    Last edited by Mcgyver; 08-10-2019 at 11:41 AM.
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  10. #10
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    One thing you will find, lighter mills tend not to cut a dead straight slot. So start with 1/2 inch, then climb one side at say 10 thou, then 10 thou on the other side ...... then measure and finish to size.

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