Originally Posted by BigDaddyKane
Sidecar... allow me to elaborate... I'm having a lapping bar made for me by a friend who is a machinist. I paid 35$ for the metal... he's turning it for free... in the end I'll have a lapping bar that is precise.. built exactly how I want it... for a quarter of the cost of buying the 35mm lapping kit kit. In addition... he's cutting off two lengths from the overall rod to make the plumb bobs that fit in the individual rings to check alignment... I'm not uninformed. Rather going about it a cheaper and better way. I simply didn't feel it necessary to explain that in the first place.
You need to 'explain' all the parameters involved in your issue and a forum, any forum that deals with your issue needs to be aware off all facets......
I apologize profusely, however, being a machinist and journeyman tool and die maker, and shop owner myself, I can say without any qualms that no 'turned bar' by any machine tool that turns steel or any material for that matter, will be as accurate as a centerless ground bar. Good luck on that. There is a good reason why drill stock is centerless ground. Concentricity and parallelism and neither is achieveable at the same tolerance level (or surface finish) as centerless grinding.
Keep in mind that when lapping anyrhing, both lapped surfaces degrade. While the softer of the 2 degrades (abrades faster), both abrade with the cutting action of the lapping compound. In other words, any lapping bar or tool has a finite life.
Nuff said on that.
I digress. Have at it. When it don't work out get the drill rod.