Saturday, October 11, 2014

We Have Chips

Made the almost-ceremonial first cut with my mill today; deliberately chosen to be something I never would have tried on my CNC Sherline:  0.2 deep slot across a 1" steel bar.  12L14 or Ledloy for you cognoscenti ;-)
The mill did just fine.  I, on the other hand, did less than 100%.  I hadn't tightened down the vise holding that bar all the way and had some rude shaking.  Nothing that slowing down didn't fix. 

In this past week, I've gotten some familiarity with the machine, evaluated it somewhat and made some measurements of run-out on an end mill in a collet and on a couple of drill chucks.  The 3/8 end mill had less than .001"; that is, a dial indicator contacting the part doesn't change by more than .001 as the cutting tool's shaft rotates once.  The drill chuck, advertised as .004, showed .009.  The R8 adapter arbor it was on had less than .001.  I emailed the seller, Little Machine Shop, on Wednesday and had the replacement via Priority Mail today.  This one comes in at .004.  (Yeah, that's an endorsement.  They treated me well and I'll keep going back to them.  FTC - they don't give me anything.  I buy it).  By the way, the Grizzly chuck that comes with the mill had almost .015 run-out.  Maybe that's acceptable for a drill chuck.  Precision machinists don't use drill bits except for very rough operations.  But I prefer the .004" run-out. 


7 comments:

  1. A lot of overhang on that part...
    must just be for the photo.

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  2. Yeah, it had too much. Did it for that cut because midway through setting up, I found that safety shield visible at the top hit the milling vise. I cranked it sideways until the vise cleared and just stuck the rod through a bit farther.

    That shield has an interlock that keeps the motor from starting if it's open by more than about 30 degrees. Definitely going to be a pain while I figure out how to live with it.

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  3. maybe you could bypass the switch and use magnetic base lexan chip shields.

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  4. One of the first things you'll want to do is get rid of that infernal chip guard. The G0704 chip guard is truly a worthless accessory. A Bridgeport mill doesn't have a chip guard even though it is many times more powerful.

    My first project was to mill the tee slot nuts down to the proper size, and the chip guard was continually in the way. And so it went away.

    Here is how to do the deed.

    Russtuff http://www.youtube.com/watch?v=vn6UvTeBQsI

    hossmachine http://www.youtube.com/watch?v=vxHoSifZqss

    "Friends don't let friends buy X2's"

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  5. More good progress, nice. I concur about LMS. They've always been good to me. They also have an infrequent email they send out that mentions some machining shows they'll be at. In the last year that has been Portland, PA, and MI. I don't recall anything near your area. They also have a yearly Open House in Pasadena coming up.

    http://www.littlemachineshop.com/openhouse

    73, Jim

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  6. Wow, it's really amazing what some companies consider "precision".... Our company throws away carbide mills that are over .0007" TIR - and that is for our standard tools. The premium stuff has a max of 3-5 "tenths". I know most people don't concern themselves with TIR, but think about it : as that tool wobbles, one tooth is doing the majority of the cutting. Tool life, finish, and performance all are affected by quality tools and tooling. You'll never regret buying quality equipment.

    While I am no expert, I have done a fair amount of Bridgeport and lathe work. In full disclosure, as well, I am the Maintenance man at Dura Mill Inc. So yeah, I know what a good 'mill looks like.

    look forward to seeing more chips fly.

    Leigh
    Whitehall, NY

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  7. Leigh - the .004 run out is on a drill chuck. Still sucko, but not on an end mill. The end mill was under .001". I don't think machinists will ever hold an end mill in a drill chuck and drill bits are not going to make nice, straight, circular holes no matter what you hold them in.

    If you're going to toss tools that are .0008" TIR, where can I go to paw through the trash? ;-)

    Anon 1144, I found those two videos yesterday and that's the enxt thing I do.

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