Bead Roller Modifications Harbor Freight

[Ralph]

Eastwood and Woodward sites say their 3/8" main body is "plate steel".
Harbor Freight says theirs is "cast iron".
I bought the HF unit yesterday with a 25% off of $149.95 (coupon on HF main site, good till 12/18/2016)

Questions: is the HF unit cast iron? If so what rod is everyone using...or does it matter, when adding re enforcing braces?

If it is cast iron what I do is pre-heat the metal and use a 6011 or 6013 rod. After I weld a bead I ping it with a ball-peen hammer.