New build - need linear ball pillow block advice / sourcing help

[DachSavage]

Hi all, new to the forum and looking forward to building my first CNC machine. I am grateful there is a DIY forum like this and will probably have a lot of questions. My goal is to build a 54" x 54" high quality high speed CNC router table type machine yet keep the costs as reasonable as possible. I realize this is not going to be easy but I already have a half dozen really high quality supported round rails that came out of HP Designjet wide format printers that I am looking to incorporate into the project. They are over 60" each and I am trying to source open linear ball brg pillow blocks for them at a reasonable cost. I started looking on Fleabay and I found lots of linear bearings but all the reasonably priced ones are metric. Problem is that the rails are .623" (I am assuming these are considered 5/8" nominal). I need 12 pcs for my preliminary design but so far all the bearings in 5/8" that I have found are like 10-12 times as expensive as say the SBR16UU which is the 16mm metric near equivalent. The chinese vendors don's seem to be offering " standard brgs and I am wondering if anyone here knows of a source of reasonably priced 5/8" open linear brg pillow blocks? Barring that, I know that there is an adjustment on these pillow blocks and 16 mm is approx .630. I have emailed 3-4 vendors to ask if this is in the adjustment range of the 16MM bearings and so far none of them have been able to give me an answer. Has anyone here tried to adjust a linear bearing down .007"? I was also wondering if it is feasible to put a strip of .003 piece of shim stock in the 16mm bearing block bore to close the cartridge down to suit the .623 rods? BTW, I have already looked at the print head carriage that originally rode these rails but while they have a type of lineal bearing they have a lot of "slop", are predominately plastic and not really shaped to lend themselves to re-purposing. I would appreciate any advice, sourcing tips or solution ideas that anyone cares to offer. Meanwhile I will go back to perusing the archives for insight into what I have gotten myself into, maybe it will help me ask better questions down the road. Thanks Dach.

Similar Threads:

• pillow bearing block
• Thompson 1" linear shafting with pillow block bearings
• pillow block bearings
• Linear Pillow Block Slide Bearing Specs. How accurate will my cuts be?
• small bore ball bearings w/ pillow block or flaged

[ger21]

EDIT: Disregard this post, it is NOT correct.

.623" = 16mm

What you have is 16mm rail, not 5/8".
16mm bearings should be a perfect fit.

[DachSavage]

.623" = 16mm

What you have is 16mm rail, not 5/8".
16mm bearings should be a perfect fit.

Hi Ger21, thanks for your reply. I must be missing something but I just double checked 3 different conversion charts; 16mm shows as .6299213 on all. Rounding to 3 digits wouldn't that put 16mm at .630 which is .007 larger than my rails and .005 larger than 5/8" or .625? Is there something about the way linear bearings or rails are measured that I am not understanding? I measured my rails with a micrometer across the largest diameter ( in 3 places on the shaft ) and came up with the .623 dimension. How much clearance is desired between the bearing bore and the shaft? .0035 seems pretty "loose". Please advise. Dach.

[ger21]

Disregard my previous post. I was somehow rounding .629 to .623.

How accurate are your measurements? 5/8" shaft should be about .624 -.6245.
So you probably do have 5/8" shafts. Unfortunately, I think all the chinese stuff is metric, so the 5/8" bearings are coming from Japan.
I don't think adjusting a 16mm bearing will work well. These bearings are not the most rigid to start with. You're cheapest option might be Igus plastic bearings, if you can make you're own housings.
igus

[louieatienza]

5/8 Inch Open Twin Linear Pillow Block (with out bearing) | eBay

Cheap for empty block... just need to find cheap bearings!

[DachSavage]

5/8 Inch Open Twin Linear Pillow Block (with out bearing) | eBay

Cheap for empty block... just need to find cheap bearings!

I agree, looks like a better solution than two individual blocks. Considering this is for a 54" travel machine do you think that a single 5/8" supported rail per side (for the Y axis) would be stiff enough to prevent racking of the X cross beam? I had planned on using two supported 5/8" rails per side with 4 bearings ea for the Y. I guess I could still use 2 of these per side, that should be awesome stiff but might be overkill? I am trying to build a sturdy machine that I can quickly and accurately score glass with but also be able to change to a router to extend its usefulness. Dach.

[louieatienza]

I agree, looks like a better solution than two individual blocks. Considering this is for a 54" travel machine do you think that a single 5/8" supported rail per side (for the Y axis) would be stiff enough to prevent racking of the X cross beam? I had planned on using two supported 5/8" rails per side with 4 bearings ea for the Y. I guess I could still use 2 of these per side, that should be awesome stiff but might be overkill? I am trying to build a sturdy machine that I can quickly and accurately score glass with but also be able to change to a router to extend its usefulness. Dach.

If you're driving the gantry from both sides you may be OK, though my preference is to have the gantry bearings spread as far as possible, regardless of how it's driven.