Skate bearings on CRS rod

[bobh]

Here is yet another idea for those who need to go the inexpensive route and use skate bearings. I had already built the 7th Sojourn crankorgan machine,
so I was able to use it to route layers out of 1/2" MDF that were then stacked together to create a linear bearing asembly. The stacked MDF housing holds 5/16" threaded rod & 5/16" carriage bolds upon which the skate bearings are mounted. The bearings are positioned to have a bearing run along the top of the rod and two bearings at 120 degrees to either side of the top bearing. The bottom of the assembly is open to allow the rod to be supported. The bearing assemblies consist of two basic shapes that are used to hold the threaded rod/carriage bolts. These are shown in the first picture.
If you sandwich together two of the shapes on the right, you have a holder for the top bearing. The shape on the left is used to hold 5/16" carriage bolts for the lower bearings. The slots to hold the bolts are tapered so there are wider at the bottom which allows the bolt/skate bearing to move in & out for adjustments. The small screw in the side is used to press the bolt towards the rail to make the adjustment. The open side of this shape is placed against the upper bearing layer and the stack is bolted together. The whole
assembly is held together by eight #10 machine screws (this is probably overkill, but I did not want the MDF to split where the adjusting screw is placed). I added a thin piece of phenolic to the ends of the stack to act as wipers to clear debris off the rails. Phenolic was all I had at the time and the piece would probably work better as a wiper if it was more of a soft/rigid type of material.
The example that is shown in the next picture shows two sets of lower bearings placed on either side of an upper bearing layer, but another combination would be to have a lower bearing layer placed between two sets of upper bearing layers.
The rails are 1" CRS round rod that is pretty inexpensive. I made the bearings so that the rails could be the supported type of rail since they are 50" long on my machine. The supports I made (the third & fourth pictures) are quickie ones I made out of 3/8" phenolic and screwed down to the table top. I drilled and tapped the CRS and attached the supports to the rail from the bottom.

When all the layers are stacked together, the tops of all the pieces are flush which then gives you a nice flat surface for mounting. This distance from this surface to the bottom of the upper bearing will be the same for all sets
of bearings that you assemble. The adjustment screws on the bottom only affect how tightly the whole assembly fits on the rail.

I made this set out of MDF since that was what I had on hand at the time, but it could be made from something a little more substansial if needed. I know you need to have (or have access too) a CNC router to make these, but in my case building the crankorgan machine first was very educational and it gave me the ability to make parts for my second machine that I otherwise could not fabricate. I can post the dxf files if anyone is interested.

Bob

P.S. I have had them running for about a month now and they still seem to be fine.

[Geof]

Nice, very nice.

[WilliamD]

Very nice! I'm basically going to use the same method of cutting slices and bolting them together. I really like you design, simple and effective. How is the MDF holding up? Is it fairly rigid? Where did you get that CRS? What does CRS stand for? I would love to have a copy of the DXF files! Thanks for the inspiration!

[2muchstuff]

CRS stands for Cold Rolled Steel.

[joecnc2006]

I have a similar idea i was thinking of using on a larger 4'x8' router i'm working on.

[rippersoft]

I would like to see the DXF files to play with. Very good idea.

Thanks,
RipperSoftware

[bobh]

WilliamD,
The MDF when stacked and bolted together like shown is very rigid. For application where the bearing rides on top of the rail the MDF should be sufficient. If the bearing was hung upside down on the rail, then you may need to go to a stronger material (maybe phenolic or acrylic). The cold rolled steel I got from MSC a year or so ago for another application and never got used. I just looked it up and it was ~$22 at MSC and ~$21 at Enco and both were for 6 foot pieces. Bearings were from VXB. I can upload the drawing files when I get home from work. Thanks, Bob

[pminmo]

great idea!!!

[ger21]

Very nice.

[bobh]

Here are the files that I used to cut the MDF. I use sheetcam and pocketed the grooves for the threaded rod and then did an outside contour to cut the pieces out.

Bob