View Full Version : Sand and Resin Filling Box Section

16-12-2015, 12:50 PM
Hello Everyone

I am heading along with my 50x50 Box Section CNC and I have bought my Kiln Dried Homebase jointing sand. I was just going to use that to fill the box up but then thought that every time it comes apart the sand will leak out of the threaded holes.

I have seen that it is mixed with resin but I don't know if that is because it adds strength and dampening too. Or could I use PVA and mix it with the sand to hold it in and stop it running out, but also because I am using 3mm steel would it tap well with the resin and help with the holding too ?.

If it is resin I'm not really sure how much to order or where from ?

I guess its not possible to mix it with mortar and just make cement is it.

Thank you for any help in the right direction



Clive S
16-12-2015, 03:00 PM
If you have not built it and tested it out I would not fill it yet. Also 3mm is tight for threading what rails are you using? Some people have glued another strip of metal inside the box so as to be able to get a better thread grip. I think Eddycurrent has done this.

16-12-2015, 03:28 PM
Hey Clive thanks For the Reply. The only problem I have is that I have to fill it before I weld up the second end with my screw plates at the end. I guess I could make a filling screw at each end but I didn't know how the sand and resin flows as the hole wouldn't be large.

The rails are 20 mm Round supported type that I bought before I started to learn it wasn't the way to go but I have made the design with an eye to swapping to Hiwin in the future.

16-12-2015, 03:41 PM
Sand is as you know extremely abrasive. I filled the base of my Chester Lux mill with the the B&Q variety sand and some gravel mixed in with casting epoxy a while ago too. (I am sure you can find cheaper alternatives to that though like roofing resin?). Then went to drill it to put linear rails and found that my drills would burn as soon as they broke though.

My advice is to drill and tap before filling. Then plug the holes using a hotmelt glue gun.

The epoxy/sand mix does not flow well unless it is more on the epoxy side of weight ratio. I think I did 10% by weight that produced good results but it had the consistency of mortar.

16-12-2015, 04:11 PM
Hello Komatias

Thanks very much for that I didn't even thing of the drilling I just thought It may hold the bolts better. I does certainly sound like I will be best to drill and tap first then and then I think I will come up with a small slider door or something on the box section.

Do I have to use resin or can i just pour the sand in and then empty it in the future If needed ?

Back to the drawing board.


16-12-2015, 05:05 PM
Make the frame so the sand can added after it's built and removed if needed when moving etc. It's just dampening the vibrations you don't need epoxy unless you intend to leave it in and like has been mentioned this can cause other issues along the way.

16-12-2015, 07:45 PM
Hey Dean

Great thanks very much for that that will be my ideal and I will just tape the holes if I ever need too. Brilliant back to the molten metal then :smug: