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  1. #1
    Join Date
    Aug 2009
    Posts
    106

    Cool New 770 owner!

    Hello,

    Just purchased a new 770, should arrive Friday. :wave: Can't wait to get a pile of chips on the floor!

    I purchased the machine for my hobby business; non-ferrous jewelry, wood, plastic, and engraving. I'm in Durham, North Carolina and would be happy to meet other local makers.

    I joined cnczone about 4 years ago and have been reading continuously ever since - but this is my first post! Look forward to discussing techniques with the many experienced members I've come to know.

    --Bryan

  2. #2
    Join Date
    Jan 2012
    Posts
    789
    Welcome to the club, Bryan! I'm sure you'll love it.

  3. #3
    Join Date
    Apr 2011
    Posts
    71
    I've been enjoying my 770 for 2 years now, I'm sure you'll love yours!

  4. #4
    Join Date
    Jan 2007
    Posts
    869
    I've had mine since December. I absolutely love this machine. It's already paid for a large portion of itself. I couldn't be any happier with it.

    I kind of wish I had the room for the 1100, but I really like having the 10K spindle.

    Wade

  5. #5
    Join Date
    Jan 2013
    Posts
    32
    Bryan, you will love it. I purchased my machine a few months ago. It is hard not to spend all your money and time outfitting your new toy with all of the latest end mills and attachments! Please post a few pics of your new baby when you get a chance.

    Have a great time,
    Leigh

  6. #6
    Join Date
    May 2013
    Posts
    63
    Bryan

    I'll be getting a used one, hopefully next week. Mine is the bigger (slower) 1100. I'm not too far from you, down in Ramseur, Randolph county.

  7. #7
    Join Date
    Aug 2009
    Posts
    106
    Thanks for the warm welcome!

    I'm contemplating tooling & endmills right now. I was thinking about using ER collets for everything, and the off-brand TTS ER chucks are a good deal, 10 or 20 of them should be plenty for my needs.

    But ER20, or ER16? The ER16s max out at 3/8" which is the max recommended for the 770 anyway, and I've read several threads suggesting the use of ER16 to "get in a bit closer" to the work.

    But they're basically the same price as the ER20s and no one is offering ATC compatable off-brand ER16s (I don't have an ATC, but may eventually add one).

    Any wisdom on ER20 vs. ER16?

  8. #8
    Join Date
    Jan 2007
    Posts
    869
    I've used up to 1/2" EM on my 770 without a problem. If you do, you have to drop your RPM's down to about 5500 tho otherwise you aren't getting the most torque out of the motor.

    Get the ER20's if you want to settle on one size. Also, don't discount the setscrew holders. Those things are great.

    Wade

  9. #9
    Join Date
    Oct 2011
    Posts
    477
    I have an 1100 but I use ER20's and ER32's. the 32's allow the use of large shank tools like reamers and larger end mills.

    I could also see the need to own a few ER16's.

    All work in the ATC provided they are grooved.

    nitewatchman

  10. #10
    Join Date
    Jan 2013
    Posts
    263
    If you're doing any 4th axis stuff then definitely ER16

  11. #11
    Join Date
    Jan 2012
    Posts
    789
    I prefer the set screw holders over the ER's. If you are using high pressure coolant like I do, the coolant splashed up into the collet, even getting into the TTS R8 collet. I have to stuff a rag scrap into the back of the ER holder to stop this from happening. And if you leave tools in the collets for a long time, a lot of junk gets in there and can leave your collet and holder less than perfect. I use air to spray out the collet every time.

    The set screw holders just work.

  12. #12
    Join Date
    Aug 2009
    Posts
    106
    Quote Originally Posted by GJeff View Post
    If you're doing any 4th axis stuff then definitely ER16
    ER20s on the 4th Axis:

    What's the problem with the ER20s for this? Is it simply the width of the collet nut down near the bit? Or is there something else going on? I'm definitely looking at getting the 4th axis for my jewelry work, so if ER16 is necessary for that, I'd like to understand the reasoning. Also, how do the ER16s compare to, say, the 1/8" set-screw holders for 4th axis work?

    Set Screw Holders:

    I've read that the ER system has better runout than the set screw holders. Most of my work has been jewelry using 1/4" or smaller bits (actually everything of value so far has been 3/32"). At this size, the runout becomes a significant part of the equation.

    Engraving Bit:

    I also purchased the diamond engraving bit, is this bit used with the spindle on or off? No instructions were included, I think the spindle is supposed to be off, but I don't want to break a brand new bit by not spinning it!

    --Bryan

  13. #13
    Join Date
    Jan 2013
    Posts
    263
    It's just the width/diameter of the collet nut. Every little bit counts when doing 4th axis stuff. If the nut is smaller then you can have your piece held that much closer to the chuck without colliding with the chuck's jaws. Granted you can probably get away with ER20 - I do but I'm not doing anything nearly as small as jewelry and I'm using a 1100 with a giant 8" rotary table.

    I hate set screw holders too much run-out. Collets are the way to go for small end mills when run-out really matters.

    I don't know anything about diamond engraving bits, for engraving I use a Milescraft 2214 1/4-Inch V Groove Router Bit which works great for both shallow and deep engravings and is nice and cheap - but probably a bit heavy duty for jewelry. I'd like to hear and see what others are doing with the spring-loaded diamond bits though. I'd assume you can do some very fine stuff and I believe you leave the spindle off.

  14. #14
    Join Date
    May 2013
    Posts
    63
    What shape and configuration is the tip of the engraving bit? I've seen single-fluted and 3-sided pyramid shapes. Every one I've ever used was with the spindle on at HIGH speed.

  15. #15
    Join Date
    Jan 2012
    Posts
    789
    True- I use the ER20's for small diameter bits. You can get some excellently small runout on them. But I've not had any trouble with runout on the Tormach set screw holders I use for 1/4" and up.

  16. #16
    Join Date
    Jan 2013
    Posts
    263
    Here's a video of a diamond drag bit, the spindle doesn't rotate.

  17. #17
    Join Date
    May 2013
    Posts
    63
    I stand corrected. A "diamond drag bit" is a new one on me, but more knowledge is good! Thanks for the info.

    http://www.diamondtool.com/dragengraver-dr.html

  18. #18
    Join Date
    Oct 2011
    Posts
    477
    I use these Engraving Mills to cut Part Numbers and Trademark Names into a ductile iron casting we are machining. There are two lines of text about 2" long and .4" tall. The depth of cut is 0.015", spindle speed 5140, feedrate 5IPM. The engraving cut takes 2.4 minutes and about 2-1/2 minutes with a tool change. Total cycle time on the part is 20 minutes. we have cut ~450pcs at $52.00 each.

    I originally bought 50 of these cutters on eBay from China for this job expecting to go through a lot of tools. So far, we have used 4. Looking back at that order, the deliverd cost was $1.76 per cutter.

    This works VERY well for us. We have run them in ER20's, and in a 1/4" Jacobs Chuck. Used the Jacobs Chuck so they could be easily changed on the fly if they broke in a cut, they haven't. Doesn't make a lot of difference.

    Your mileage may vary.

    nitewatchman

  19. #19
    Join Date
    Sep 2012
    Posts
    1543
    I'm partial to 2linc.com for all engraving tools, so far they are proving to last a lifetime. (unless you have bad code). I have a Diamond Drag engraver, but have never used it, and yes, spindle is stopped while using it.

  20. #20
    Join Date
    Aug 2009
    Posts
    106
    Finally! Got 'er all set up; PCNC 770, power draw bar, fog buster, 2 vises, 10 ER-20 collet holders, and a variety of end mills.

    I was going to post a pic of cutting my first piece - then the end mill broke!

    1/8" mill drill, 4-flute into 1/8" 6061. I entered it into GWizard as a 2-flute, set on "Turtle speed", got a plunge of 5 in/min @ 10k RPM. It got about half way through the material before it snapped, with aluminum welded to the flutes.

    I know.. I know.. use 2 flute cutters on aluminum. I got 4 more on the way.

    Was that all I did wrong here? If I do the same operation with a 2-flute carbide/TiN mill drill, will it plunge ok? I've also read that HSS is better - but at this size the recommendation seems to be carbide. I'm using a mill drill bit because later it does some chamfering and engraving with the angled tip to reduce tool changes.

    Thanks!

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