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pminmo
06-12-2003, 08:21 PM
I'm in the process of designing my own router, similar to the hobby CNC one. It will have low utilization, so wear isn't to much of a concern. Mostly will cut balsa and light ply, but maybe some softwoods also. I've got a Rotozip Solaris I plan on using for the router.
I just bought two pieces of 3/4" drill rod from KBC (I'm lucky their 5 minutes away) that I plan on using for the x axysis. Rough dimensions for table top 36" x 18". I have a piece of glued up hard maple strips that is very stable and strong that I plan on using for the basic bed. The rest will be baltic birch plywood of appropriate thickness for the part. My son has played roller hockey for years so I have some of those bearings. My question is on the x axysis, I'd like to use two bearings on top of the 3/4" rod and use brass bolt ends (either 1/4-20 or 10-32) for lateral bearings and bottom bearings. By using T-nuts or brass inserts I can get snug adjustments. I figure that the weight of the Y,Z axysis mechanics and the 2 lbs of the router will place the most force down. I wouldn't think a lot of lateral force force would be placed in while cutting. The other thought would be to use some exotic (LV) hardwood for lateral and bottom bearings. Just can't commit myself to the cost of commercial linear bearings. But I am a firm believer in the KISS principle. Am I going to be in for a surprise?
Thanks,
Phil

mwestern
06-13-2003, 02:08 AM
I have been very successful with building my own linear bearings. My latest design is made from 1/2" stainless steal, skate bearings, and 1.25" drill rod. They work well, but are very time consuming to build. My maching is made to cut aluminum and mild steel. Materials have cost my about $800.

Mark

balsaman
06-13-2003, 02:23 AM
You will be fine. JCK uses skate bearings on the side and top, with nothing on the bottom and it works great.

Eric

dhprc2
06-13-2003, 01:19 PM
Originally posted by mwestern
I have been very successful with building my own linear bearings. My latest design is made from 1/2" stainless steal, skate bearings, and 1.25" drill rod. They work well, but are very time consuming to build. My maching is made to cut aluminum and mild steel. Materials have cost my about $800.

Mark

Mark, what kind of tolerances are you getting with your machine? Do you have any pictures you could post?

Thanks!

p.s. I tried to post this once already and it didn't seem to work. Sorry if it comes through twice.

pminmo
06-13-2003, 06:01 PM
Hear are two bearing pictures I'm thinking over:
http://webpages.charter.net/pminmo/bearing1.gif
http://webpages.charter.net/pminmo/bearing2.gif

Planform I started with, subject to bearing decision:
http://webpages.charter.net/pminmo/table.gif

Opinions sought from those who have been through this.

mwestern
06-13-2003, 11:53 PM
Here is the bearing I am assembling, I have not completed my machine. I have not had a chance to check the precision or accuracy. The bearings fit pefectly on the drill rod and glide like silk.

mwestern
06-14-2003, 12:00 AM
Here is one side of the gantry with the bearing attached

mwestern
06-14-2003, 01:10 AM
What is nice about this bearing plate is that is made from stainless steel and will not deflect under a considerable load. The first bearing I made of aluminum and when pushed against the gantry with your body wieght you could feel a little deflection.
I have this bearing skeched out in Auto Cad if you would like to take alook.

Mark

balsaman
06-14-2003, 01:32 AM
Hear are two bearing pictures I'm thinking over:

Go with the second one. There will be heavy side loads when the router is off to the side of the axis.

Eric