LR3#strut-plates, Strut Plate Material

HI All,
I’m unable to source 1/4" MDF for the strut plates. Would 1/8" Hardboard or 1/4" plywood plywood be an acceptable choice? Planning on picking it up today.


Would be nice to see a definitive list of most-to-least preferred Strut Material options from LR3 Beta/Experienced folks.

Recommendation depends on your build dimensions and what you’re planning to cut. But guessing folks here doing relatively Stock build are using 1/8" tempered hardboard or 1/4" ply. Seal and paint before assembly.

Feels like 1/8" Hardboard is most common? But I think (someone please confirm/correct me) …

Common Strut materials (from Most rigid):

  • 1/4" Hardboard (1 solid piece or 2 x 1/8" glued)
  • 1/4" MDF
  • 1/4" Ply
  • 1/8" Hardboard (3/18" Tempered Hardboard Panel at HomeDepot)
  • 1/8" MDF
  • 1/8" Ply

Exotic Strut Material options :


Personally used 1/4" ply leftovers (gantry has 56.5" tube/strut-length). Custom front strut looks cool, but I don’t have any performance/strength data to share indicating whether this or something else is the weakest link for my build. Still learning…

I used 1/8" Hardboard that I bought from Lowe’s and it should be fine in most instances. My issues with it seemed to be related to me going “off script” in my LR3 build, resulting in not the best cut (my openings for the screws were less than ideal), and so my performance of the 1/8" Hardboard was a bit off from the goal. At the time I did not fully grasp why, and so I used the hardboard struts just long enough to cut some more struts out of 1/4" plywood. However, I kept the 1/8" Hardboard struts, and did indeed use them on my 2nd LR3, which is made to carry a plasma torch, and thus the minor deficiency in how they were cut is less of an issue, since the plasma cnc does not need the same rigidity as a router CNC needs. What I later realized was that due to the cut inaccuracies, a few (not many) of the screw heads slipped through instead of clamping down. I hope this helps. If you don’t go off script, you should not have the issues I had.

Also, the dialog on difference between solid struts and ‘skeletonized’ sheets is an interesting one. I agree the strength difference is likely minimal, and I would point out that having the openings in the ‘skeletonized’ sheets has been crucial for me to get the nuts held in place while tightening screws. I would strongly advise using the shown design of ‘skeletonized’ sheets, or some variation of it. I my case, I modified it by using “X” brace design instead of “Z” brace design, and while it may or may not have added any rigidity, it did not take away my openings like a solid strut would have. I have seen designs where only one strut (the “front” one) was solid, for the sake of design aesthetics and implementing distance markers, and that is probably doable as you still have openings in the bottom and back for reaching in with tools to clamp nuts!

Thanks Doug. The Lowes hardboard is what I was looking into. I think I’ll give that a go. If it doesn’t work out I can always change it.

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PS: the design with the solid strut on front looks really sharp. Very tempting. I think it may have been by aaron GitHub aaronse

Agree, rear and bottom struts must have holes large enough for you to fasten the nuts, and maybe route some wiring, or hold power adapter(s) even. Brace design revision with captive nuts would be nice.

Just to confuse you some more :slight_smile:

@marvinlange has a slick looking solid front Alu grill…

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Nut capture slots are a mixed bag on whether they are good or bad. I have usually seen them hold for one use, but become problematic on instances where you need to loosen and remove screws to redo something, and re-insert again a 2nd or 3rd time. One thing: if you get them working right, don’t over tighten them or you risk “spinning” the nut in the slot and then it never works right again. At that point having no capture slot is better than a ruined one!


PS: I think I remixed the brace to have capture slots on all the screw holes instead of just one side. I was mixed on whether it’s better or worse, but lean slightly toward that it was better. :slight_smile:

PPS: The above note is based on the fact that I have built two LR3’s and the remixed braces were on the second one. :slight_smile:

LowRider 3 CNC - braces for gantry remixed to have nut capture slots on all holes! (v1.0)

Here’s a link to the Printables listing of the remixed braces with nut capture slots on all three directions:


Well I have a lot of weight on my gantry been playing around running it full speed have not noticed any twisting it feels very Rigged but make sure you glue your spindle mount nuts in its a pain in the but if you don’t with the solid front strut

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