By far the easiest method would be to through bore it & insert a bush-like spacer (with nicely squared ends) in the middle of the bore. A light push fit with a few loctite grooves should do the trick.Tel Terry old sod, I was going to suggest that very thing but held off in hopes you would come up with it. That way you will get the blame if things turn out for the worst!! Actually it looks to be a very good idea to use the bush though I believe I could machine a shoulder with that centre mounted boring bar by just not cutting all the way through. Jesse in Tennessee MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.