(NOOB): Size of glass for 10" i3v?

I went to Home Depot and bought a 6 pack of 12'x12' mirrors for $12.00 and a glass cutting wheel. Then, like dacb; I scored and snapped them down to 10"x10" and trimmed the corners by scoring and snapping with pliers. Then sanded down the snapped edges with 220 sandpaper.

I noticed with the mirrors that my actual bed temperature (measured with Fluke laser thermometer) is 10 degrees C less than what I ask for. Set for 110C but measure 100C. Not sure if this is the same for glass but thought I should note it.

My Ace Hardware glass ranges from 7C to 10C cooler than what my Prusa is set for.

I'm not totally sure, but I think it might make sense that all heatbeds with glass on top will measure in similar way.

I think the thermistor being sandwiched between kapton tape, the bed, and some sort of insulating material creates a very small air gap that holds its heat in much better than the surface of the bed which is open to the environment. I wouldn't be surprised if the thermistor is measuring the correct temp for its location underneath even though this isn't a very exact measurement for the surface of the glass.

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Originally Posted by dacb

Welcome to forums! Congratulations on your printer!

I used a piece of regular glass from the local hardware store and they cut it to 10"x10" for free. Then I used a glass cutter like the one below to score the glass on a diagonal at each corner to form an isosceles triangle with the two edges of the same length being about half an inch (IIRC). Then, I had my kid hold down the glass using a straightedge at the scoring line which was also aligned with the sharp edge of a table below. Then, I took a pair of vise-grips and snapped off the corner. Remember to wear safety glasses.

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I accomplished the same result with my 10" also....but instead of cutting the corners myself, I made a cardboard template of the heat bed with the corners cut diagonally to make room for the screws. Took the template to the hardware store and they made me two pieces of glass per the template for $4.00. I would say wait until you get the kit, measure the heat bed yourself, then decide your approach before having glass cut....you will spend 2 days or so putting the kit together so the glass will not be needed immediately.