The bed that comes with the Tevo Little Monster is very uneven so I decided I would add a borosilicate glass plate to level it out until I upgrade the heated bed and base plate. There were a couple of bed clips around already but they either could not be tensioned or affixed to the frame rather than the bed. I also did not want to use the existing bolts holding the bed on as I use these from manual bed level and I needed to make sure the clamp did not interfere with the fan ducts or IR sensor that sticks out past the sides of the hotend
So I created a small clamp with a cam to it that not only held the glass in place but also clamped it down to the bed evenly. I tried some different design that did not require modification to the bed itself but in the end the best design was the one that required a few additional M3 holes to be drilled. I also made a jig to made it easy to drill the holes exactly where I wanted to make life easy.
Make sure you print out of ABS or Polycarb, I have run the clamps for several days in Black ABS printing Polycarb (130C bed temp) and have had no issues as the edge of the glass in nowhere near the indicated bed temp on the edges (only around 65C)..
Hobbyking Black ABS
The clamp is sized already to make up for shrinkage in ABS, the hole jig is meant to be printed in PLA but the small shrink if you wanted to print in ABS would not be an issue.
You will need to use the hole jig to line up each of the wholes while the bed is still in the printer, you can mark them or just hit them quickly with a drill bit to mark them.
If you have a M3 Tap, then drill out the 3x holes with a 2.5mm drill bit then follow up with the M3 Tap. If you don't have a Tap set you can use, then drill out the 3 holes with 3mm drill bit and use longer bolts and a M3 lock nut on the back. The parts are deliberately a little less height than a 3mm glass plate so they flex and clamp down the glass bed, so make sure you tighten the bolts down well. I suggest you use button head bolts so they do not protrude much above the surface of the clamp, you may also be able to use a countersunk screw. Make sure either way you use some lock tight on the threads to stop the bolts slowly coming out.
Take care to clean the bed plate and glass plate well then add the glass to the bed and carefully align it in the center and tighten the clamps to hold it in place. Once you have it tight and aligned correctly only loosen one clamp each time you need to remove the glass, this will ensure the glass bed remains aligned in the center without having to fiddle with the three clamps each time. The original Tevo sticker (undamaged) works as a pretty good temp transfer from the heated bed, if you remove this sticker you will need something to make up for the height difference between existing glass bed (one that came with printer) and the aluminium holder for it (about 0.5mm difference in height).
I designed this model in Fusion 360