Terry McGee wrote:
Phenolic resins. Vacuum impregnations. Acrylics. Young people these days, I don't know....
Nah, good on youse. The 19th century was great, but we must be getting close to time to move on...
I'm surprised you impregnate the lot, but you probably have your reasons. I'd imagine I'd do the rough boring (but not the reaming) and the rough outside turning (but not the profiling) just to get rid of the worst of the waste, and give the resin access to both inside and out. Then you're impregnating and curing less material with better access. But maybe you find the material machines better once impregnated?
Well, the first surprise I got when doing resin infusion is that wood doesn't really absorb it much through the surface, but rather the end grain. I have actually put some bored out and shaped pieces in and didn't find that it absorbed noticeably better than un-bored, square pieces. But to really evaluate this I'd need a more formal test where I weight the pieces before and after. I might find that there is more absorption than I think. My gut says no, because I've done a lot of this now and would probably notice a significant difference. So while you will save some waste by using rounded stock, that is the only advantage. And sometimes I do actually rough turn before infusion, but that presents some other difficulties I'll describe in a moment.
The wood
does machine better after being infused. A big difference, actually. I've reamed raw maple versus infused maple and the difference is quite significant. The resin-infused piece cuts much smoother--more like an oily wood. Not quite as glassy as something like blackwood or cocobolo, but pretty close. Whereas the raw maple reams quite rough by comparison.
The difficulty with pre-boring the stock is that it can still move during the cure process unless steps are taken. In many cases this won't be a problem, but you might suddenly end up with a section whose bore now has a slight curve to it, which might complicate your re-boring or reaming process. I've overcome this problem in some cases, but that is another long and technical conversation

If you are only doing short pieces, this is not an issue. If you are getting up in the 20" range it's another matter.
With square stock, I can wrap the wood in foil after infusing, then clamp several pieces together in a row. The pressure from the clamp makes it difficult for the individual pieces of wood to move during the heat cure, so that there is less chance of warping. With some woods that are highly prone to warping, I actually sandwich the stock between lengths of square stock steel and clamp them from all four directions, so they can't move at all during the cure. Even so, if there is enough grain tension the wood might still move a little once the clamps are released.
Scrimber! I knew I heard that word before

I think it was from one of your posts, most likely!