Build Thread Chris' G0704 build - Page 21


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Thread: Chris' G0704 build

  1. #401

    Default Re: Chris' G0704 build

    CL_MotoTech you got me thinking last night so I took a look at the mill this morning. The screws all seem to be tight but I could feel some slop in the table if I grabbed the ends and pushed them in opposite directions.

    The Y axis seemed to be the culprit. I was able to tighten it down quite a bit. It was enough that I decided to pull the gibb and take a look at it. There's a wear mark where the very top of the dovetail on the base is touching the gibb. It doesn't look like they are machined on the same angles. After playing with it for a while I got it about as tight as I can without stalling the axis. I think the only cure for this would be to buy a new gibb and grind or scrape it to fit the casting.

    The X axis seems OK. I pulled the gibb and there are a few spots over the entire face that are contacting. It's not a lot and it's not very even, but it's better than the Y. I tightened it down until the screw bottomed out in the casting. That axis seems to be OK though.

    I checked Grizzly's web site and the gibbs are available for $8.50 each. I think I'll order a pair and see if I can get a better fit on the machine.

    Anyway I'm going to try pushing the MRR a bit harder over the weekend and see how the machine reacts.



  2. #402

    Default Re: Chris' G0704 build

    I ran a test cut using a Best Carbide 3/8" 3F Carbide at 6750rpm, 81IPM (.004" IPT).75" DOC and .030" WOC (1.5" MRR) and worked my way up to .060" WOC (3.65" MRR) in .005" increments. The machine seemed quite happy at 3.65" MRR. I stand corrected. Apparently my weak spindle motor and sloppy gibbs were giving me the impression that the machine was tearing itself apart.



  3. #403

    Default Re: Chris' G0704 build

    Awesome!

    Here's the end mill I've been using a lot: https://www.ebay.com/itm/3-8-3-FLUTE...53.m2749.l2649

    They are brittle, but they really cut nice and they last a long time, just don't drop them...



  4. #404

    Default Re: Chris' G0704 build

    This conversation makes we want to try a four flute .5" and see what MRR I can get. I may run up against TTS but it's worth a shot!



  5. #405

    Default Re: Chris' G0704 build

    Here’s a short video of the machine cutting 6061 aluminum at 3.65” MRR.






  6. #406
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    Default Re: Chris' G0704 build

    Hi Chris - The specific MMR is usually expressed as DOC/feed rate. In metric this is (mm depth of cut) / (mm/sec or mm/min) What are the units of your MMR ( inches?) So its the volume removed in time not just a distance? Peter



  7. #407

    Default Re: Chris' G0704 build

    Hi Peter,

    I mentioned the specifics up a few posts. This was 3.65 cubic inches per minute. 0.75” DOC, 0.060” WOC, 6750 rpm, 0.004” IPT.


    Chris



  8. #408

    Default Re: Chris' G0704 build

    Quote Originally Posted by ChrisAttebery View Post
    Here’s a short video of the machine cutting 6061 aluminum at 3.65” MRR.
    Nice and quiet too!





  9. #409

    Default Re: Chris' G0704 build

    I’m making a solid tool post riser for my lathe. I couldn’t find a new piece of steel large enough at any of the local metal suppliers. I wound up buying a burn out that was approximately 35 lbs. On Saturday I spent a couple hours making chips and turned 14 lbs of steel into this:



    That was about half of the chips in the machine. Since then I’ve whittled another couple pounds off with the mill. I have to drill a few more holes and bore pockets for the hold down screws and this side is done.




    Sent from my iPhone using Tapatalk



  10. #410

    Default Re: Chris' G0704 build

    A quick update: Since installing the 2hp motor I've been able to double the MRR on every one of my programs that I've run in aluminum to roughly 3" pre minute. I've done this mostly by increasing the WOC. I feel really comfortable with the machine running 81IPM (.004 IPT) with a 3 flute carbide end mill. The other day I was tweaking a program and had the feed override set to 150%. The mill powered right along at 120IPM and 4.5" MRR but the finish suffered a bit.



  11. #411

    Default Re: Chris' G0704 build

    I got the flat parts of the new motor mount machined out of 1/2" 6061 last night. The inner pieces mount to the head and the outer pieces mount to the motor.

    Chris' G0704 build-img-7865-jpg


    I went to make the round threaded spacers I need and realized that my 3/8-16 tap can't cut deep enough.



  12. #412

    Default Re: Chris' G0704 build

    I finished the mount up at lunch today.

    Chris' G0704 build-img-7866-jpg

    Chris' G0704 build-img-7867-jpg



  13. #413

    Default Re: Chris' G0704 build

    Good news, good news, bad news...

    The first good news is that I machined a bunch of parts yesterday morning and the mill is much more satisfying to run now that I've cranked up the metal removal rates.

    The other good news is that the new spindle and gibbs showed up a couple weeks ago. I finally got around to installing the new spindle yesterday. It seems to have a bit better runout. I measured it at .0015" TIR roughly 1.25" from the end of the spindle with a 1/4" carbide shank in an R-8 end mill holder.

    The bad news is that the ABEC 5 bearings that I installed in May are shot. The lower has a click and the upper feels like it's full of sand. :^( I ordered two sets of the cheap AC bearings from VXB that I had originally used. They should be here by the middle of the week.



  14. #414

    Default Re: Chris' G0704 build

    Are you using strictly AC bearings or were those ABEC 5 units tapered?

    I have found much better life with tapered bearings though I've been through loads of both, but I suppose there are number factors involved. Adding an oil drip to mine seems to have been a huge help in keeping the spindle nice and quiet. I'm using way oil from the automatic oiler and I just let it drip in the top of the spindle. It's not adding much oil, but I do find some oil running out the bottom "seal" after the spindle sits for a while. So there must be some purging action going on. Before I installed the oil drip I smoked the tapered bearings but had an important customer project at the time. So I pulled out some noisy bearings that I saved for just this scenario. After adding the oil drip and reinstalling the noisy bearings I started the spindle. It sounded like crap but I decided to stick it out, and I ordered two new sets of SKF tapered bearings. Well after about an hour of running those noisy bearings went quiet and I've been running them ever since. I have five months on them this year and an unknown amount of time on them before they got noisy and I removed them the first time. They are no-name Chinese bearings from eBay, $8 a piece. I have $80 of SKF bearings just sitting in my toolbox. So after this long story, I think lubrication is certainly the issue on these spindles. Though I do prefer the tapered bearings as they seem to require less adjustment.



  15. #415

    Default Re: Chris' G0704 build

    These were ABEC 5 AC bearings from VXB. I pre-lubed them with Kluber Isoflex NBU 15. This is the same procedure I've used with the previous sets and those all lasted at least a couple years. I'm leaning towards too much pre-load or too much load from the heavier cuts I've been taking. I haven't used tapered bearings since I converted to belt drive 7-8 years ago.



  16. #416

    Default Re: Chris' G0704 build

    The dynamic load rating of the compatible tapered bearing is more than twice that of the AC bearing (generally speaking as I'm not going to research all bearings). Too much load is too much load. Your finishes are beautiful and given your experience I am willing to bet you had the spindle setup just right, the bearings just don't seem up to the task (IMO).



  17. #417

    Default Re: Chris' G0704 build

    Quote Originally Posted by CL_MotoTech View Post
    The dynamic load rating of the compatible tapered bearing is more than twice that of the AC bearing (generally speaking as I'm not going to research all bearings). Too much load is too much load. Your finishes are beautiful and given your experience I am willing to bet you had the spindle setup just right, the bearings just don't seem up to the task (IMO).
    I guess I'll try the AC bearings again and if it becomes an issue I can swap back to tapered rollers. It looks like the bottom bearing is rated to 6200rpm on grease though. I'd have to lower my upper RPM limit.



  18. #418

    Default Re: Chris' G0704 build

    You have a one-shot oiler, switch to oil. There's a reason why bearings have higher RPM ratings with oil than grease (it doesn't matter if it's Kluber or cheap grease).

    To add oil I made a plate that sits inside the mill head where the gear used to be, it has a compression fitting for the oil line, the oil literally drips from the fitting onto the top bearing and uses gravity to lube the bottom bearing. I'm using Vectra way oil. When the ways get oiled so does the spindle. The plate is glued in place with silicone sealer. Certainly a bit jenky, but trying to drill and tap holes down in there would be challenging and there's no reason the plate will ever need to come out. The plate has a hole that's slightly larger than the splined section of the spindle, which also helps to keep dirt and other things out of the spindle from the top side. The entire project took like 12 minutes. It's very simple but will get you to higher RPM and longer bearing life.



  19. #419
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    Default Re: Chris' G0704 build

    Quote Originally Posted by CL_MotoTech View Post
    You have a one-shot oiler, switch to oil. There's a reason why bearings have higher RPM ratings with oil than grease (it doesn't matter if it's Kluber or cheap grease).

    To add oil I made a plate that sits inside the mill head where the gear used to be, it has a compression fitting for the oil line, the oil literally drips from the fitting onto the top bearing and uses gravity to lube the bottom bearing. I'm using Vectra way oil. When the ways get oiled so does the spindle. The plate is glued in place with silicone sealer. Certainly a bit jenky, but trying to drill and tap holes down in there would be challenging and there's no reason the plate will ever need to come out. The plate has a hole that's slightly larger than the splined section of the spindle, which also helps to keep dirt and other things out of the spindle from the top side. The entire project took like 12 minutes. It's very simple but will get you to higher RPM and longer bearing life.
    Good tip. I'd be worried about over oiling though.
    Do you think that is an issue or does it just pee out the bottom once there's enough in there?



  20. #420

    Default Re: Chris' G0704 build

    I can't switch to an oiled system. I cut a lot of plywood on my machine.

    It dawned on me that I did recently cut a ton of steel at rates I wouldn't have attempted before. I wonder if that caused the bearings to go.



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