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Thread: how to machine a long bore?

  1. #1
    rainman is offline Aluminum
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    Default how to machine a long bore?

    I have somewhat of a challenge here for CNC lathe. 1.063 dia. blind bore, +.002/-.000, 8.45 deep, flat bottomed. 6061-T6 aluminum part. Ream? Tools I find aren't long enough. Getting chips out is going to be a challenge as well. Any suggestions?

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    Mydrrin is offline Hot Rolled
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    How many parts? you could use a 0.875 devibe and a TCMT go from back to front. Run once pull chips, run a second time to size - you might be able to get it to size in one pass - try different things if something isn't working. There are reaming tools that you can use with extensions. Can't seem to download the link but here might be something.

    AlliedMachine.com

  3. #3
    Limy Sami is online now Diamond
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    Dualkit is offline Diamond
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    How is your turret\reamer holder alignment to the spindle? If it isn't dead nuts you are going to have to bore it to hold +/-.001 over 8" deep.

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    PixMan is offline Diamond
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    Just what is allowed at the bottom of the bore regarding corner radius, flatness and finish? That could be your bigger problem than bore diameter, tolerance and length.

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    A long Allied Drill to depth, with a flat bottom of the same size comming in behind it, both with HP coolant will do a decent job on this.

    When the tool shanks get this long, they will pull onto center way better than a short stubby one, so more likely to drill to size.

    Best bet is to drill slightly under and ream in.
    But you would want a reamer with a through tool coolant port, and I don't know much available for that.
    I have had to have some of them made that way.



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    rainman is offline Aluminum
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    Thanks guys, for the ideas. I'm trying to get the engineer to cut me some slack at the bottom of the hole, so it doesn't have to be finished to the very bottom. I was thinking as were you that I'm gonna have to get some serious coolant through the tool to get the chips out that deep.

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    Dualkit is offline Diamond
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    Quote Originally Posted by rainman View Post
    Thanks guys, for the ideas. I'm trying to get the engineer to cut me some slack at the bottom of the hole, so it doesn't have to be finished to the very bottom. I was thinking as were you that I'm gonna have to get some serious coolant through the tool to get the chips out that deep.
    First thing I do when I see a flat bottom is too ask if I can have a drill point and how big.

  9. #9
    Limy Sami is online now Diamond
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    Quote Originally Posted by Dualkit View Post
    First thing I do when I see a flat bottom is too ask if I can have a drill point and how big.
    Same here, and when they ask why? I play the cost card - surprising how many minds that changes

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    Dualkit is offline Diamond
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    I found a lot of flat bottoms that are called out are for springs so the flat part doesn't have to be very wide in most cases.

  11. #11
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    david n is offline Titanium
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    Many times I call the customer before I even quote the part and let them know what features are going to hit their wallets the most. As Sami said, it changes minds right quick.

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    rainman is offline Aluminum
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    Thanks again. Only problem here is that this is an in-house thing. Although cost should be important to engineers, it isn't always. This is for a pneumatic deal, this being a piston bore. I'm hoping when the engineer looks at it closer, he'll find that the piston doesn't go all the way to the bottom, and can allow a certain distance from bottom that's not to size

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    Dualkit is offline Diamond
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    Quote Originally Posted by rainman View Post
    Thanks again. Only problem here is that this is an in-house thing. Although cost should be important to engineers, it isn't always. This is for a pneumatic deal, this being a piston bore. I'm hoping when the engineer looks at it closer, he'll find that the piston doesn't go all the way to the bottom, and can allow a certain distance from bottom that's not to size
    I have been self employed for over 15 years but I really enjoyed those engineer vs machinist battles when I worked at a large company in the 80's. If you can prove your design will save money and be just as functional you will win the battle 100% of the time. Of course you may have to take your battle pretty high up the ladder.

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