I converted CharGriller Duo to Natural Gas (NG). Ordered circuit board drill bits: Xuchuan circuit board bits. Used this website to convert from millimeters to the correct Wire Bit size - www.riogrande.com. Cross references to this chart to estimate BTUs - www.joppaglass.com. Did not measure water column (WC). Used old NG grill orifice size by seeing which drill bit fit. Through trial and error, I increased the bit size until I had a good flame and the burners fully lit.
I used an old NG orifice from a Weber grill (blackened from use) as a starting point - orifice was was 1.6mm. I started at 1.4mm to be safe and worked up to 1.8mm for the burners. I drilled out the side burner to 1.60mm.
Final orifice size for CharGriller Duo is 1.80mm - this is at sea level (Charlotte, NC). Start out with a smaller bit and work up (altitude and WC might be different where you are at).
Held orifice with vise grips to drill out hole.
These are the Circuit Board bits I used - ordered off Amazon and they came from Xuchuan - 10pc circuit board bits - cost $6.00! Yes, you read that right, $6 for 10 micro drill bits ranging from 1.1mm to 2.0mm.
LP orifice was 1.0mm so I drilled starting with 1.2 until I got to 1.7mm as my final orifice size for NG. I worked my way up to avoid breaking bits.
The bits fit into a Dremel tool. Run it at fairly high speed to avoid the bit seizing. Brass is easy to drill so no need to press down - I just let the weight of the Dremel tool drill through.
I cut the LP regulator off and reused the hose pieces. Use a 3/8 brass T (threaded) & 2 female brass barbed connectors (one for the burners and one for the side burner). Used 1/2 in hose clamps. Connected and tested for leaks using soapy water.
On high, it hit 700 degrees in about 2 minutes. You need to be careful as there are no knob stops so you can crank it full on (this is a fire hazard so do not leave your grill unattended and DO NOT LEAVE IT ON HIGH!) You have been warned.
Things got really hot really fast - DO NOT LEAVE UNATTENDED and DO NOT TURN IT TO FULL HIGH! Flames will shoot out from protectors and splash guards at high. There are no knob stops (which typically come with a conversion kit to avoid this hazard).