ACME Rod bearings

[pbunnstf]

I am just beginning design of my Z axis for my router and plan to use 1/2"-10 ACME rod with a Dumpster nut for the Z axis.

I plan to support the rod with pillar blocks on each end and assume that I will have to machine the rod at each end to fit the appropriate size bearing.

I have a 9 x 20 lathe and a mini lathe but am not much of a machinist - I plan to chuck the rod up and turn until I the threads cut off and turn the rod until I get it to the bearing size? Anyone know the likely bearing size for 1/2" -10 and any suggestions as I promise I hardly know what I am doing.

Thanks in advance for any help.

[diecutter]

I used 1/2-10 ACME rod and dumpster nuts on all three axis of the router I built.
I turned the ends down to .375 " dia. which is just where the threads disappear and a standard ID bearing can be used. On my next machine there will be some changes. First, I'll use thicker ACME rod with less threads per inch. My 40" long Y axis has some harmonics on 80 IPM rapids and the 10 TPI limits top speed. A 3/4"-6 rod may give better performance.

Also, I would have liked to try running the 1/2-10 ACME rod through a bearing with a half inch ID (no lathe work, better support, truer alignment), and used an ACME nut on each side to secure it (this would make preload a snap). I did cut the 1/2-10 rod down on a 9 by 20 Jet lathe and it was easy. The rod is loaded through the spindle bore sticking out of the chuck just far enough for turning. Be sure you center the rod carefully with a dial indicator; I ran an ACME nut which was round outside onto the rod and secured it with a jamnut, indicating on the round outer surface. Good luck on your build.

[pbunnstf]

The idea of using a 1/2" bearing and not machining the ACME rod is interesting. Has anyone tried this? The 1/2 " pillow block seems common and I can't find a 3/8" pillow block.

[joecnc2006]

Yes that is what I use on my Model 2006 machine, Made bearing blocks with HDPE and inserted 1/2" bearing and preload with two 1/2"-10 acme nuts (ie. a jam nut on each end), helps eliminate alot of the lead screw whipping.

Joe

[putela]

Have you guys been using deep groove ball bearings or angular contact bearings?

Would deep groove bearings work without noticeable backlash & withstand sufficient force? I'm thinking about a small(ish) moving gantry router, around 20 x 12 inch table size, for plastic and some light aluminium work.

Thanks in advance,
Pekka

[Madclicker]

Originally Posted by pbunnstf The idea of using a 1/2" bearing and not machining the ACME rod is interesting. Has anyone tried this? The 1/2 " pillow block seems common and I can't find a 3/8" pillow block.

I used 3/4" and 5/8" acme rod mounted in the same size flange bearing with no machining. Held in place with the set screws only. Works fine....120"+ rapids.

[yukonho]

Depending on your machine, and how deep/fast cuts you are doing, you likely far more prone to getting backlash from leadnuts and machine flex than with bearings, at least on smallish hobby machines. I used single skate bearings on my current machine, and after two years, there is no noticeable play in the bearings. Generally I cut basswood and ABS, 1/8" thick. Not too much load in my case. When I build a more robust machine I will look at different bearings.
Colin

[dertsap]

i would suggest using 3/4 "-6 acme rod with 3/4 pillow or flange bearings , thats what i used on my small table and it worked well ,you will need to add some .003 shim stock to snug up the screw in the bearing or you will end up with the screw running a lil wacky , 6tpi rather than 10 will gain you nearly double the speed