Drilling Holes In Carbon Steel
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    Default Drilling Holes In Carbon Steel

    Hi,

    I am looking for the most efficient way to drill approx 65 - 7/8" dia holes in flat, 1 1/2" thk carbon steel plate on a CNC mill. We currently use a high speed drill for this operation which seems time consuming with the pilot holes, pecking, and slow feed drill rate.

    We have heard the Sumitomo 3xd replaceable thru coolant w/ 7/8" dia drill tip inserts would work best for this operation.

    Is this the way to go? Other suggestions?

    Thanks,

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    Just don't use a High-speed drill at S2500 and F4 (IPM) with no coolant, like I accidentally did yesterday.....

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    Annular cutter? Always my go to for holes <1/2”. Put it in a 3/4” collet or tool holder.

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    What milling machine - cos some tools need less speed but more power, torque and push than some CNCs can deliver.

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    Might be a wee bit nicer if you put some prices on your suggestions....just sayin'

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    Haas Mill VF 8 / 30 Hp / 7500 RPM

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    Would you consider these similar to the Sumitomo 3xd replaceable thru coolant drill tip inserts?

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    What happens when the slug stays in the cutter? That would be my concern.

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    I've never used any Sumitomo drills, but I could also suggest either a Sandvik CoroDrill 870 or an Iscar Sumocham. If you want to increase your throughput they also make one with a 3 flute design that I haven't gotten to use yet, but have been looking for an excuse to get.

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    Quote Originally Posted by fstdril View Post
    Would you consider these similar to the Sumitomo 3xd replaceable thru coolant drill tip inserts?
    with out knowing which sumo line you are referring too, both of the links i provided are products with through coolant drill bodies

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    Quote Originally Posted by CAMasochism View Post
    I've never used any Sumitomo drills, but I could also suggest either a Sandvik CoroDrill 870 or an Iscar Sumocham. If you want to increase your throughput they also make one with a 3 flute design that I haven't gotten to use yet, but have been looking for an excuse to get.

    Sounds good, Thank you. Ever had any issues with the tips breaking midway through a hole?

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    Is your mill thru coolant capable?

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    Yes, our mill is thru coolant capable

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    Quote Originally Posted by fstdril View Post
    Sounds good, Thank you. Ever had any issues with the tips breaking midway through a hole?
    So far only when an operator isn't paying attention to their inserts or when through spindle coolant isn't available. Once you get your speed and feed dialed in with either of those drills they have great life. The Iscar 2 flute Sumocham drills come in a fairly wide variety of geometry designs, so if one of them isn't quite working you can try another.

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    Quote Originally Posted by fstdril View Post
    We have heard the Sumitomo 3xd replaceable thru coolant w/ 7/8" dia drill tip inserts would work best for this operation.
    Never had any luck with the Iscar Chamdrills I'd stay away from those, they just haven't worked like they claim, at least for me.
    However the Sandvik 870 drills are really, really good! And don't forget to look at Kennametal etc.. each big name brand has their own replaceable tip drill and they are all pretty much similar in performance.

    Do you know the exact type of steel you're drilling? Carbon steel plate can mean a million different kinds of steels.

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    Straight shank, 3/4 or 1/2" shank S&D 135 deg HSCO 7/8" drill - 442 RPM 7.2 ipm. 7/8" does not need a pre-drill. G73 high speed peck to eliminate any long errant chips. Try 3-5 pecks total to start.

    Drill time - 0.1 clearance plain - 0.18 tip length plus over-drill - 1 1/2" stock - 1.9" cut length X 65 = 123.5" LOC / 7.2 ipm = 17 minutes.

    4 pecks costing you maybe 0.4" X 65 = 26" / 7 = 3 3/4 minutes.

    Let's call it 21 minutes.

    Chamfer both sides with long neck 1/2 carbide DA cutter from Harvey or the likes. (3.1415 X 0.375 tool path D) +(0.2 lead in lead/out) X 65 X 2 = 179 LOC / 30 ipm = 6 minutes.

    In the cut time for job around 28-30 minutes.

    In short, if you had just loaded a drill on hand and started drilling instead of posting here you would already be done and on to the next job.

    With a rigid setup and proper coolant concentration the drill should make it through the whole job without a problem.

    If this is a repeat job and you have no drill yet on hand then by all means, go the high route. But remember the basics is just about a half an hour w/ 2 sided chamfering.
    Last edited by 13engines; 02-21-2020 at 08:33 AM. Reason: large brain fart on chamfer equation. material stated improved times

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    Material is SA-516 70 Normalized plate

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    Quote Originally Posted by fstdril View Post
    Material is SA-516 70 Normalized plate
    Qty (18) post's in, an then you announce this little fact ?

    Why not in post #1 ?

  20. Likes Mtndew, Steven-Canada liked this post
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    isn't all steel carbon steel?


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