Breaking TiN coated carbide step drills - Page 2
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  1. #21
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    Quote Originally Posted by cbarish View Post
    Trying to use a TiN coated carbide step drill for a 1018 steel part. Step drill diameters are .245" at the tip leading to a .427" diameter. The drills are breaking on the lead angle (118°) between 1-6 thousand cycles. We have tried changing the RPM's up and down with no positive results and would prefer not to slow the cut down as it is a very high volume machine.

    Currently we are running at 850 RPM's with a .300" feed and a 12 sec cycle time. Originally was set to 1160 RPM's and have also tried 1500 RPM's. We are looking at changing the coating to AlTiN. Does anyone have any other suggestions to prevent the tool breakage?
    You need to know chip-load. All drills Ive found have a 3% of their diameter chip-load. Your drill is quite a stretch. The .427" diameter should be able to a chip-load of .03 times diameter.
    Use the RPM to calc the feed rate. Of course the RPM has to be with your carbide tools ability to run at that rpm.

    Please try it. I'd be interested in how it performed.

    Regards,

    Stanley Dornfeld

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  3. #22
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    The nature of the plant I work in doesn't lend itself to playing around with speeds and feeds. Machines run 24/7 365. A stoppage for 5 minutes needs to be justified.
    The first thing you really need to change is your management.
    If your management is so stupid that they are unwilling to allow you time to optimise the operation cycle, then they deserve to have a large bill for replacement parts.
    And step drills have weaknesses, and may not be the best solution here.

    Cheers
    Roger

  4. #23
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    I drill tens of thousands of holes in 1018, all you need to do is contact your local OSG rep , show him your drawing , let him supply you a couple of test drills ( normally free) , follow his speed and feed recommendations , problem solved. You will be surprised on how fast the hole can be drilled , I'm thinking under 2 sec.

  5. #24
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    Quote Originally Posted by cbarish View Post
    You misread the original statement. The .3" feed isn't per minute it is how far the tool goes in the 12 second cycle time. This equates to .0018" per rev.
    I'm sorry, but I read it the same as Limy, and probably everyone else did.

    YOU needed to clarify it in the original post, much like you have now done in post #10.

    Don't get mad at us 'cause we aint mindreaders.

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