Thanks for the feedback folks, much appreciated.
Mikey you mentioned you prefer the DBL202A. Are the 3/8" bars easy to come by as the 1/2"? Would you prefer HSS or carbide tipped bars?
Criterion
HSS bars are scarce in new condition, regardless of shank size. A full set of six bars used to cost $125-140.00 or more on sale; much higher retail.
If you go for another brand, like Borite, then either shank size is readily available. I prefer Borite cobalt boring bars; they will cut almost anything in my shop, are easily sharpened and they last forever. These bars leave a fine finish at the lower speeds boring heads require. Between 3/8" and 1/2", the lighter 3/8" bars will let you go slightly faster due to their lower mass. The DBL-202 A heads take 3/8" bars; the 202 B head takes a 1/2" shank.
I don't use carbide tools in my boring heads; you can and many do. My reasons are that cobalt bars cut well at lower speeds and finish finer than carbide. There is less deflection with a cobalt bar, especially compared to an inserted carbide bar, so I feel they are more accurate. Carbide needs a bigger depth of cut to work well and while they will rough just fine, I find that dialing in a thou or two is not what comes off due to deflection. Many times, I am boring to really tight tolerances and I need that bar to cut what I dial in; cobalt does that for me and carbide often will not. Whether others have similar experiences, I don't know; this is just what I've found in my shop.
To be fair, I use bench top mills. If I had a big knee mill that could better handle the centripetal forces then I might be able to go faster and carbide would work better ... but I don't. One of the items near the top of my To-Do list is to make up a set of counterbalance weights for my DBL head so I can up my speed without my mill walking down the street. Criterion had a set of these weights that came out just before they were sold to Allied. You can buy them but it comes in a set with the head, bars and weights and sells for north of $500.00. I would rather make them than buy them at that price.
I can just see you guys stroking your chins, saying, "Hmm, I can make that!"