Speeds, Feeds, and Strategies for Bench Top Mills - Page 7


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Thread: Speeds, Feeds, and Strategies for Bench Top Mills

  1. #121

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    Bad bearing! BADDDD bearing!!!! Impressive. I haven't had any go bad in that manner. Usually mine have just started getting noisy.



  2. #122

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    I have flat spotted rollers, just out right overheated them, filled them with swarf, but this is the first cage failure I have seen. We saw this all the time in our racing motors, so I am not new to this type of failure, but it was a surprise in my G0704. Being on the topside bearing, that's especially rare. I have a bearing above this too, so it's not like it's carrying the full load of the belt drive, in fact the belt drive is in double shear across the two bearings. The lower bearing looks great. At some point it was over heated, there is some blueing of the race, but despite that it shows little sign of wear. The rollers look great and the cage is fine. I changed out all bearings this time. I am not super happy with the tune of the spindle right now. I will continue to run it and tweak the lubrication and setup. Once i actually start to cut the true performance will be obvious... I have been very lucky with spindle performance lately, I hope to return to that.



  3. #123

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    New bearings are in and running, albeit a spot hot. 10 hours of run time down, they haven't fried yet... At full hog the machine is insanely quiet. It blows my mind.

    I was struggling a bit with surface finish before, tool chatter too. The new bearings have fixed all of those issues. That top bearing was letting go for quite a while it seems. I feel like an idiot.



  4. #124

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    Cruising. The machine has been on since 3pm and will run through the night. In the morning I will setup two more billets for a final side Side A run. Once they are done, I will get the table setup for the side B cuts. Side B takes less than 10 minutes per gear.

    I'm not crazy about my current spindle tune, but I think it will be fine if I do a slight adjustment on it. I just need a spot less preload. These things are so sensitive it's crazy.





  5. #125

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    I started the final round of Side A's. The spindle is a little hot at around 140F. I am not going to play with it until after this run.

    I am still running at 54 ipm with a 3 flute at 6k rpm for roughing. The machine is quiet as can be. This is probably the best surface finish I have ever achieved with this machine. I'll grab some more pics as I finish off these parts.



  6. #126

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    What brand of bearings did you go with?

    Here's a post from Forrest Addy on spindle bearing temps. They're talking about lathes in this thread but it all applies. I've learned more about machining by reading his posts than any other source.
    https://www.cnczone.com/v...earings-81612/

    I measure the temperature with a Raytech IR temp gun right where the lower bearing sits in the quill. I put a piece of masking tape there because the IR guns don't read well off of shiny surfaces.



  7. #127

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    I think they are just the VXB house bearings. They were in plastic bags, no box.

    I checked out that thread. I use an IR gun generally on the side of the head, but only do so after long runs, it takes a while to heat soak all that material. I was seeing right around 135F, too hot IMO. That aligns with the information in your thread. This is with a coolant ring, which definitely pulls the spindle temps down, so I am certain preload is too high. At one point I even smelled a bit of oil smoke, so clearly the internal temps are pretty high.

    These are a spot tighter on the spindle than previous bearings and that makes adjustment just that more precarious. I use the old fashion calibrated elbow method for setup and frankly it's a crap method. I wish I could set them and move on, but I don't have any good ideas on how to do that yet.

    This in mind, the new bearings seem to be okay for now.



  8. #128

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    I like measuring the temp as close as physically possible to the bearing.

    If you're having trouble setting the bearings try setting it like you normally do then tapping both ends of the spindle with a nylon faced hammer. Give it a couple good whacks and then check the drag again.

    The Timkens I tried were tighter on the spindle than the NSK are. I had to heat up the lower Timken to get it in place. The NSKs just need hand pressure.



  9. #129

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    The issue is that the last little bit of preload is so touchy. Tiny fractions of a turn makes all the difference. 1/30th of a turn can change the spindle temp 50 degrees. So no matter how hard I try, it almost always ends up being three of four tries before I get it right. Removing the drawbar, coolant ring, spindle pulley, it's not a hard process, but it takes time to pull it apart and then get it back together right. The drawbar can be especially touchy. If it doesn't get setup right then things get ugly real fast.



  10. #130

    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    Yeah that sounds like a lot of work. I can pull mine in about a minute now.



  11. #131
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    Default Re: Speeds, Feeds, and Strategies for Bench Top Mills

    Honestly glad (in a way) to hear that I'm not the only one who thought the preload nut was super touchy. I've spent soo much time reassembling the spindle trying to get the perfect balance.



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