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  1. #41
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    I second Bobs comments, 3/8”EM may play better yet. I can’t see a trim line on that part but it sure looks like a forging. OEM SAE type forgings are usually jacked up (Q&T) for higher strength. That ALWAYS changes the machinability ratings.

    So, how hard is it? HSS endmills are pretty much limited to 40-45ish machinability rating with Q&T steels. So if your file nicks a (carbide insert) lathe shank it’ll be about the limit of what HSS will cut. And that will be done by factoring the speed will be reduced 60% from AISI 1212 ratings, or about 66 surface feet per minute MAX.

    So for a 1/2”EM about 500RPM & 3/8”EM about 670RPM - MAX. Center cutting hard steel sucks with a BP, but then milling through the forging skin also sucks (radius on the flutes helps a lot here).

    And WHY are you cutting through a suspension link???

    Good luck,
    Matt

  2. #42
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    Quote Originally Posted by gbyoung View Post
    No, the quill was not locked.

    I did my first plunge manually bringing the quill down, raised the quill, shifted the table to the back, did the second plunge, then shifted the table back and forth while manually holding the quill down to take out the section that wasn’t cut during either of the two plunges.
    Yup, you're chipping the corners of the endmill. Lock the quill in the up position and feed with the knee! Dump the 2 flute end mills. Where did you learn to use those? Go to a smaller endmill, like 1/2"

    This is all stuff I learned in trade school 100 years ago. AFAIK, the basics haven't changed since then. Just bring them over, I'll bet I can cut 20 of them with one end mill.
    JR

  3. #43
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    Quote Originally Posted by JRIowa View Post
    Yup, you're chipping the corners of the endmill. Lock the quill in the up position and feed with the knee! Dump the 2 flute end mills. Where did you learn to use those? Go to a smaller endmill, like 1/2"

    This is all stuff I learned in trade school 100 years ago. AFAIK, the basics haven't changed since then. Just bring them over, I'll bet I can cut 20 of them with one end mill.
    JR
    “Learn?”

    Sir, therein lies the problem; I ain’t never had no learning on any of these machine tools. Couldn’t spell B-r-i-d-g-e-p-o-r-t before I picked this one up a few years ago so I could try and learn how to use them. And that’s where we are today.

  4. #44
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    Quote Originally Posted by Matt_Maguire View Post
    I second Bobs comments, 3/8”EM may play better yet. I can’t see a trim line on that part but it sure looks like a forging. OEM SAE type forgings are usually jacked up (Q&T) for higher strength. That ALWAYS changes the machinability ratings.

    So, how hard is it? HSS endmills are pretty much limited to 40-45ish machinability rating with Q&T steels. So if your file nicks a (carbide insert) lathe shank it’ll be about the limit of what HSS will cut. And that will be done by factoring the speed will be reduced 60% from AISI 1212 ratings, or about 66 surface feet per minute MAX.

    So for a 1/2”EM about 500RPM & 3/8”EM about 670RPM - MAX. Center cutting hard steel sucks with a BP, but then milling through the forging skin also sucks (radius on the flutes helps a lot here).

    And WHY are you cutting through a suspension link???

    Good luck,
    Matt
    Sounds strange, but to lower the rear end of a motorcycle with the suspensions some of them use today, you increase the length of the rear suspension links; shorten to raise the rear end. These particular links are not from his bike, but from another model that shares a similar arrangement but they are too long. The 9/16” taken out will put the rear of the bike exactly where he wants it so he can “flat foot” it on level ground.

  5. #45
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    Quote Originally Posted by gbyoung View Post
    I ain’t never had no learning on any of these machine tools.
    OK, here are some basics:
    Having everything as rigid as possible will make your life easier. Use the quill to drill or bore.
    2 flute endmills are good for aluminum and thats about it.
    Any endmill larger than 1/2" costs a lot more money. If you need, you need, but not very often.

    It's taken me a lot of years to "learn" what I have. I'm more than willing to share if anybody listens.
    JR

  6. #46
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    Quote Originally Posted by gbyoung View Post
    No, the quill was not locked.

    I did my first plunge manually bringing the quill down, raised the quill, shifted the table to the back, did the second plunge, then shifted the table back and forth while manually holding the quill down to take out the section that wasn’t cut during either of the two plunges.

    The HSS 2-flute was all I had at the time, and 9/16” was used because that was closest to the exact amount he wanted removed from each (suspension) link. Each needed to be cut exactly the same to prevent stresses once welded up and fitted back on a bike.
    Just to repeat and emphasize what others have said in case you missed it. Your process is a big part of your problem.

    To successfully cut metal your part and tool holding must be rigid. Flex in either the part or tool leads to deflection which leads to chatter and dulling of tools. By using the quill you introduced flex into the tool which dulled it during the cut and possibly work hardened the part.

    1. Lock the quill
    2. If your mill is old and worn, lock any table axis you are not currently feeding with.
    3. Don't plunge with the end mill unless there is no other option. They cut much better to the side.

    In your case, I would get a new 4 flute end mill as others have suggested. Use the table feed if possible and create the notch from the side in multiple passes. The rigidity of your part holding will determine your depth of cut. The more rigid your setup, the deeper you can cut on each pass. To play it safe, think of using a 1/2 end mill with a quarter to a third of an inch depth of cut on each pass.

    Teryk

    Sent from my XT1710-02 using Tapatalk

  7. #47
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    Quote Originally Posted by mTeryk View Post
    Just to repeat and emphasize what others have said in case you missed it. Your process is a big part of your problem.

    To successfully cut metal your part and tool holding must be rigid. Flex in either the part or tool leads to deflection which leads to chatter and dulling of tools. By using the quill you introduced flex into the tool which dulled it during the cut and possibly work hardened the part.

    1. Lock the quill
    2. If your mill is old and worn, lock any table axis you are not currently feeding with.
    3. Don't plunge with the end mill unless there is no other option. They cut much better to the side.

    In your case, I would get a new 4 flute end mill as others have suggested. Use the table feed if possible and create the notch from the side in multiple passes. The rigidity of your part holding will determine your depth of cut. The more rigid your setup, the deeper you can cut on each pass. To play it safe, think of using a 1/2 end mill with a quarter to a third of an inch depth of cut on each pass.

    Teryk

    Sent from my XT1710-02 using Tapatalk
    Definitely failed on items 1 and 3: I did not lock the quill, and I plunged with it. Oddly enough, I did lock the table in the planes I wasn't maneuvering.

    I've got a new 4-flute and we'll muster up the courage to whack this sucker tomorrow so I can send it back to Texas.

  8. #48
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    Okay, we’re done. Finally clamped up another link the fella sent and we cut a 9/16” wide swath through it.

    9/16” 4-flute un-coated cobalt EM
    ~510 RPM
    Quill locked; table raised to deepen the cut in several thousands of an inch intervals
    X-axis table movement locked throughout the process
    Table height locked for each pass, loosened to raise
    EM looks like it has survived and has lived to cut another day

    No major issues or drama. Actually went pretty smooth.

    Much thanks again for putting up with all my inane questions, and your excellent suggestions. Gotta learn somehow.





    First link cut is in the back. Latest link cut today in front.


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