Need to make make a 5/8 hole a total of 8” deep on a mill.
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  1. #1
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    Default Need to make make a 5/8 hole a total of 8” deep on a mill.

    This is the piece I’m working on. See below. I need bore a 5/8 hole in this and needs to have an 8” reach and cut length. The total length of actual cut is about 4” but it’s deep inside but where the cutter won’t engage it’s still going to be very close so it does need to be an 8” loc.

    I would prefer an indexable bc I will have a bunch of these to do in the future but I can’t find a 5/8 of that length. Anyone know where I might be able to find one?

    I’ve been on msc, grainger and the carbide store and unless I looked over one I don’t think they offer one. 93b9b366-4594-4540-94ca-212ba911a97a.jpg2c247641-8993-458e-8905-238a995e8617.jpg

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    I don't understand your LOC need as only the end of the drill bit is doing much. It's not ideal, but you can do lots of pecking to clear the chips out....and that works better anyway as even flutes don't always work that well. But for making lamps out of those pieces, why not drill it from both ends?

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    You state bore, but do you need it bored or drilled? What are the size and finish requirements? What is the material?

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    It looks like cast bronze or brass to me. Could you not just use a long drill? As gbent said, you did not state your tolerances, but if all you need is a hole through the thing then just use a long drill. If you don't have a drill that long then extend one. It's really quite easy to do.

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    You might try a 5/8 hex shank drill bit and use an extension.
    Makita B-69060 5/8" x 6" Multi-Purpose Bit, 1/4" Hex Shank - - Amazon.com

    slow easy feed going into a tapered bore or the drill may catch to spin the part or break the drill bit.

    Agree a 1/4 shank won't take a lot of torque.

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    Sounds like the thing 4 flute core drills were made for, since it appears to me there is already a hole cast thru it.

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    Looks like you are making a steam boiler injector...don't you need a tapered hole?

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    Centre drill, drill 2” in reaming size hole, ream, the first bit acts as a guide for the next instalment, go in as much as your comfortable with, ream
    Finish
    The drill usually comes out where it’s supposed to, a badly sharpened drill comes out wherever it wants, this is what I’ve found, plenty coolant not squirt can, flood ( I know it’s messy) steady feed, and I admit I’ve got drills to go where they weren’t meant to, a good US made drill bit, no Chuck taper shank
    Mark

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    Use a threaded aircraft drill on a straight extension. Most common is 1/4 shank but they do make 3/8 shank as well.
    Bill D
    Please tell me that is a poster on the wall and not the OP.

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    .5625. The piece is an eductor or foam proportioner for fire fighting. These types are mostly used on offshore units literally like on oil rigs so as much as I would like to I can’t just drill from both ends. I think I figured it out. I bought a technics slimline 1/2 shrink fit and a long flute 1/2 end mill and I’ll just use a boring cycle in cam. The holder is going to allow me to get down inside a pocket and reduce the length of stick out. Should be okay. I appreciate all the responses.

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    Tolerances are .015625

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    Yes the piece is suppose to be 844 brass but does not machine like it. I think the foundry is using the same crucibles for everything contaminating the alloy and possibly making it harder. It just takes a little bit of that and a splash of this and they have changed the properties a lot.

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    Quote Originally Posted by Shawn_Laughlin View Post
    Tolerances are .015625
    Is that +-, or TIR?

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    Yes sir plus or minus. It’s pretty big tolerances. But I was wrong on the diameter. The drawing I was given only had about 20 percent of that of all the info I needed and when I said a 5/8 hole I was guessing.

    Well I found a part that was machined and the hole was .5625 so 9/16 so I tried and I learned that a ball end mill 8” long 1/2 diameter doesn’t do to good when used like a drill bit lol.

    Ain’t happening or at least didn’t for me. Sounded like it was going to shatter before even starting to cut.

    So I had a choice of a 6” or 12” long hss drill bit so I got the 12 and cut it down to 9 and chucked it in an er32 and cut like butta. I felt like an idiot for over thinking the whole thing. But my paps loved it bc he told me from the beginning we should just get a drill bit of correct size and go with it,especially with allowed tolerances.

    Would’ve been much cheaper also. End mill plus over night 250. Drill bit from local hardware store 46 and made a nice clean hole and way faster and much less noise.

    I haven’t done much drilling on the machine and not at all familiar with the speeds and feeds of one but a little searching on line and we were making holes like a pro.


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