[jakemestre]

Nice build and modeling.

In post #7 you mention replacing the bolts with stainless to gain strength and or rigidity. Stainless though great for corrosive environments is not very strong, how about grade 8 bolts?

Also with the new design you have presented and the new spindle, a little more Z would be nice. Seems like a lot of effort to be limited by a 10" piece.

You are doing great.

Thank you very much for the suggestion. I'll try the highest grade bolts I can get a hold of and report back. I have some 4130 to machine this week so that will put it to the test.

Jake, I think you'll find a little experimentation will help with the preload as well. By all means, start with the calculated values and try to figure the spacing needed for that. I believe I have the spacing info in the article you referenced.

Then you'll want to assemble the spindle and test it while keeping a careful eye on bearing temperatures. You'll want to be sure that's possible and that the bearings aren't buried too well in the headstock to access them. Make sure you're using good quality grease, like the Kluber I reference. Follow the run in procedures you find in the various bearing manuals, again monitoring temps. Once you've run in a bit and temps are stable, you can see whether you've got the bearings too tight or too loose based on the temperatures you're getting. See my spindle article for details.

Best,

BW

Thank you Bob,
I'll be sure to add a hole in the spindle cartridge to measure temp. I'll probably just use an arduino lying around, they're so easy to program to display multiple temps.
I think I've landed on the final design for the cartridge: two angular contact bearings in the front with two deep groove ball bearings in the back. I'll have to precision grind the spindle to 55mm for the ID of a 7211 bearing. It'll all be an assembly that bolts together and can be serviced outside of the machine if necessary. The headstock will be based around a granite epoxy mix. Thanks for all your help so far, your blog has been invaluable.

for this spindle build i would use tapered roller bearings. i have them in my 13x40 geared head lathe using the same spindle. there is a massive thread here on cnczone on spindle construction, bearing preload is the least of your worries. the housing itself will need to be ground and the seats need to be straight and perpendicular to the bearing and concentric and paralle with each other. also you don't have to grind the bearings themselves you can use hardened spacers between the bearings that are ground to create the clearance you need. it will be easier to grind these than to try and keep the bearings clean. abec 3 bearings will be just fine for your build and you won't notice any decrease in performance.
i think your going to find that constructing the housing for the spindle will be a fairly difficult task and i do wish you all the luck and will offer any advice during your construction.

Thank you for the suggestions Runner. Could you by chance post a link to that thread? I'm having trouble finding it. I think tapered roller bearings will be difficult to control preload as the temperature of the spindle changes. I'm really shooting for a repeatability of this machine to be between 1-3 tenths so I'll have to be very careful about how I design the spindle. I like the idea of having two preloaded angular contact bearings in the front with support bearings in the back.

So I got most of the linear motion in the other day. Precision ground ball screw for x by Issoku, and linear guides by THK. I still need to order the Z screw, I have a rolled ball screw for the moment but ground is a must to meet the precision. Now I just need to verify all the designs for the motion system before I can start drilling some holes in my plate. I also got a duplex AC bearing set but they're ABEC 1. I want to figure out how to make the spindle cartridge before I spend $300 on a set of nice bearings. Thanks everyone for the help, keep it coming. If you see something I'm doing incorrectly please feel free to post and/or email me directly at [email protected]. Until next time.