What tool holder to cut up to a live center?
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    Default What tool holder to cut up to a live center?

    Manual machine, This comes up too often.. I'm making a replacement idler shaft for an edge sander. I need to get up close to the center to turn this section from 1 1/4 to 7/8" My go to tool for steel alloys (4140PH in this case) is a Trigon. Obviuously not going to cut it. Too many styles to choose from so looking for recommendations. Doesn't seem there is profile that can get in close and cut up to a square shoulder towards the head stock. Maybe a straight 55 degree diamond then finish the shoulder with the Trigon?lathe.jpg

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    I'll preface by saying that I am more of an amateur hack that uses machine tools, than a machinist. Wouldn't this be a typical use for a half dead center rather than a live center? The half dead center would open up more space for the tooling/insert of your choice.

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    35° diamonds or 55° diamond will usually get you up close. 60° triangle will work also. The key is not to center drill no deeper than necessary. The 35° is kinda flimsy so I'd only use it to finish. If I was only going to buy one I'd get a 55° diamond and be done with it.

    A half dead center will work but you won't get much RPM's before your spin welding the two. Those are Ok but reallly old school.

    Brent

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    I use this- ISCAR HELIGRIP

    Sent from my SM-G973U using Tapatalk

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    If you can swing it financially, an interchangeable tip live center will save you a lot of headaches. You will have a lot smaller center point to contend with being in the way.

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    Quote Originally Posted by aribert View Post
    I'll preface by saying that I am more of an amateur hack that uses machine tools, than a machinist. Wouldn't this be a typical use for a half dead center rather than a live center? The half dead center would open up more space for the tooling/insert of your choice.
    If you use non-rotating dead center in a lathe, you're gonna have a bad time.

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    I like the Iscar tool. I think a 55 diamond for deep cutting first and finish up with the iscar would be a good choice. Also I'm keeping my eyes open for a 3mt CNC center. So, guess I'm ordering toys, ah I mean tools today. Thanks guys.

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    Here's a live center I just bought and tried out this morning. Was very shocked how well it performed. Your mileage may vary.

    MT2 Live Center Morse Taper Precision 0.000197'' Long Spindle Lathe Tool CNC HOT | eBay

    Ken

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    I agree get a extended nose center.
    Bill D

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    4GSR-

    Could you expand on 'shocked at how well it performed'. I was looking at that very same extended reach center last week and almost pulled the trigger. But backed away on the theory that at $16 it must be pretty rough.

    -DD

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    Kids, more than 80 years ago (a little before I was born) tungsten carbide was invented and applied by brazing to lathe tool bits. It could be made in any shape required for about any turning or boring job. That includes reaching into the gap between a 60 degree center and the end of a bar. I have ground bits for just that sort of job. I even have five identical factory-made bits that work for that job that prove some company needed them enough to buy them ready-made.

    Yes, the so-called CNC centers are handy and have been since well before CNC was NC. I have some by Rohm and Riten and they are sometimes needed.

    But the right shape of brazed carbide bit can reach in next to a normal live center.

    There was even a time when machinists would grind high speed steel tool bits for individual jobs. And before that, the smith would forge them to order from carbon steel. That stuff did work, you know.

    The OP did say he was making a replacement part, so maybe just one off. I thought it was odd that he was looking to buy an expensive holder and inserts for such a simple task.

    Larry

    dsc02031.jpg dsc02032.jpg dsc02033.jpg

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    I use these: Royal Spring-Type Live Centers
    They're expensive, but top quality and don't get in the way.

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    Larry, even though this is a one off it seems like I'm always dealing with arbors for woodworking machines and I'm up against the center. Usually I fanagle something in there but it's time I get the right tools. Plus I love buying this shit.

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    Quote Originally Posted by Dumpster_diving View Post
    4GSR-

    Could you expand on 'shocked at how well it performed'. I was looking at that very same extended reach center last week and almost pulled the trigger. But backed away on the theory that at $16 it must be pretty rough.

    -DD
    I was expecting it to be a piece of junk like a Indian made center I bought to put with a lathe I sold off a couple of years back. You could wiggle the center point on it. This one ran just as good as a older Rohm center I bought new 40 years ago. I wasn't expecting that good performance out of a "cheap" live center. I would say, it's strictly for light duty use.

    Ken

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    Quote Originally Posted by kenscabs View Post
    I like the Iscar tool. I think a 55 diamond for deep cutting first and finish up with the iscar would be a good choice. Also I'm keeping my eyes open for a 3mt CNC center. So, guess I'm ordering toys, ah I mean tools today. Thanks guys.
    I'd save the dough for the 35 & 55° carbide unless you really need the profile turning possible with them, they aren't good metal movers on manual machines. The cool center will last MUCH longer.

    About the dead half centers, C’MON Mtndew! It is a manual machine process & it’s likely dead centers are still the gold standard for grinder hands wanting nuts-anal roundness.

    Turning with them is slightly more touchy feely because of the heat/friction deal. Nevertheless, it’s done. Running at 100sfpm with a 7/8” dia quallies for “walking and chewing gum at the same time”. Running at 300sfpm you need pretty good bug juice in the center. Figuring out how to run at 800sfpm would qually for “running with scissors and chewing gum” (I’ve never tried that).

    Below are some centers that show that (1) the 2 step extended relief for a tool is not new, and (2) why grinder guys like half dead centers (especially with wide wheels). We used to use something called white lead mixed with oil on the point to beat the friction/heat thing (it’s now a no-no), but the stuff from CMD works pretty good.

    Good luck,
    Matt
    Attached Thumbnails Attached Thumbnails dead_centers1.jpg   dead_centers2.jpg  

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    Stepping or clearing the end of a live center is common.
    Obviously you need to get in there and be able to cut inside out and most holders do not like this.

    Cole2534 points to a nice groover but be careful in application.
    Poke in, move over poke, go deeper and repeat.
    A well raked 35 diamond with zero lead will also do this needed step but fragile.
    Be careful not to stall or spin the center when cutting it which is the biggest problem. Lots or lateral force needed as you are cutting on a friction drive with a small area of drive contact.
    Small steps and very light cuts. Don't get crazy or you will spin it and puck up the tip.
    It will be hard, get the SFM down.

    Your problem sort of looks like just simply getting in there so why cut the center?
    A D,V or even a T insert and holder does not have that overhang to the right so it clears with no mods.
    Why a trigon and single sided beyond that? It is a terrible insert/holder combo and only used as a last resort.
    Bob

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