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Alaskan
01-28-2005, 06:22 AM
Hi,

I have looked around and found that making my own linear railings seems to be the best route for me.

I've looked at EBay and there are a large number of different bearings. The most popular seem to be the ABEC 3-7. Does anyone know why I would need the ABEC 7 as opposed to the ABEC 3?

Or are bearings just bearings in this applications, as RPM isn't really an issue and they will be adjustable, so I don't need chrome hardening (or do I)

The design I'm thinking off is slightly different to this one.
http://solsylva.com/cnc/trucks5.jpg

Rance
01-28-2005, 07:56 AM
Alaskan,

The one you have pictured looks complicated to build. Would something using angle iron like the attached be sufficient? Just a thought from the KISS methodology. The only thing this does not have would be the adjustment screw. Maybe we could come up with a way to do that and still use the angle iron?

Rance

ToyMaker
01-28-2005, 08:29 AM
For a wood working machine any of the ABEC ratings will have sufficiently close tolerance. The lower rating (3) might not come in a sealed bearing however.

robotic regards,

Tom
= = = = =
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Alaskan
01-28-2005, 08:42 AM
Rance:

Thanks for trying to help, but I wasn't asking about the design. The design I have in mind, I happen to have pieces that will work with it lieing around as scrap. It was the offcuts from some other design.

ToyMaker:

Thanks for the help. Seems that I pay a little for the lifetime of the bearings, and alot for the number 7. I guess I'll just get the cheapest that I can get in sufficient numbers aslong as they are sealed and of the correct dimensions.

Thanks for the help

jcc3inc
01-28-2005, 11:55 AM
Sir:

Have a look at Lee Controls, linear bearings. Thes bearing blocks are similar to what you want, use rollers instead of ball bearings, and go on round shaft.

Regards, Jack C.

CNCAddict
01-28-2005, 10:54 PM
ABEC ratings as seen in most "ebay" items and rollerblade/skateboard bearings are mostly false. ABEC 1 bearings made by a reputable company such as NSK will be far and above better than almost all of the cheap "ABEC 7" bearings. On the other hand, I think even the junk bearings will be fine for DIY CNC. Bearing tolerances would have to be truly terrible to affect the machines most people here build. Remember, even ABEC 1 bearings are around .0003" radial runout which is VERY good by my standards. Oh, and remember to purchase bearings with seals, not shields.

David Bloomfield

Hobbiest
01-29-2005, 02:15 PM
Sir:

Have a look at Lee Controls, linear bearings. Thes bearing blocks are similar to what you want, use rollers instead of ball bearings, and go on round shaft.

Regards, Jack C.
Do you have a link showing a photo of this product?

fyffe555
01-29-2005, 02:38 PM
http://www.linearmotion.com/pb.html

Torsten
01-29-2005, 04:47 PM
"ABEC 7" bearings have better runout precision a quality that
for the most part would get lost by this application.
Your design only uses the bearing in a one directional force
where the cheaper bearing would be sufficient.
The weak part in this is the I.D. of the bearing wich determines
the size bolt that can be used to hold it.
If the savings allow go for bigger here.
Good Luck.

shootingarts
08-14-2005, 01:04 AM
Sir:

Have a look at Lee Controls, linear bearings. Thes bearing blocks are similar to what you want, use rollers instead of ball bearings, and go on round shaft.

Regards, Jack C.

Jack,

Exactly what I was fixing to have to machine! I knew I had seen these rails several years back but could not locate them now. I'll be giving Lee a call Monday.

Not sure if I will go with their three roller system or some wonder plastic slides yet though. Of course when sticker shock hits I may reconsider everything.

Thanks for the link!

Hu

DennisCNC
08-14-2005, 12:59 PM
Like the idea with the angle iron by Rance, Here is one that will have a adjusting bolt, I think I should work very well and be easy to build.

ESjaavik
08-14-2005, 01:36 PM
Use the cheapest bearings you can get. Your precision will not be limited by the bearings, but the part you're running them on. Whether that is a rod, tube or angle iron. It will wear dimples in it in no time unless it is hardened.

And yes, I know this from experience. And then with a non-CNC woodworking machine. I dare not think about how fast it would be junk if it were CNC. With a couple of years of very little use, it is now no better than if I were just pushing the boards along the table. I would guess that if I just pushed it back & forth continously for one 8 hour day, it would be wobbling like it is now. And tightening it down will not work, because then it will bind when used outside where it is worn (in the center of movement).

But if you must try it yourself, as I say: use the cheapest bearings. They will outlast many shafts/angle irons.

Einar

Bear
08-14-2005, 02:09 PM
hello all,
use chromed rod for rails,like used in hyd.shafting
Bear