[Brenck]

Hi folks,

I am currently finishing the 3rd machine and I would like to tram it, I have a gantry type router. I know the principles of how to tram a spindle to the table that's not the problem, but what I am concerned is that the ''tabletop'' of my machine is an 5/8'' thick aluminium plate that is bolted to the table structure, it doesnt have any facing done on it or any machining, its just the way it came from the place that they sell alum. plates.

The thing is how will I tram this since there is no garantee that this plate is perfectly flat. Lets say I put a dial indicator attached to ''L'' shaped rod and have this inserted on the spindle collet. If the tabletop was a perfect flat, ground or faced piece it would be ok to tram it with this apparatus, actually quite simple, but if my aluminium is slightly arched, convex or concave, I will get erroneous readings...

Is there any trick to do in this situation?

Thanks to all

[jsheerin]

Bolt / clamp / whatever some sacrificial material to the bed at the locations you'll indicate off of to tram your head. Face the tops of those pieces using the router. Tram your spindle. Maybe resurface the locations you trammed at now that your spindle is straighter and recheck the tram. I typically have a MDF spoilboard on my router. I'll surface it with a bit that's not too large, maybe 0.5" diameter, then tram off of a 123 block that spans any ridges left by the out of tram spindle.

[Brenck]

Thats seems like a good idea, also I need to use a small step over while facing right? I'm thinking in something like 20% the bit diameter, I think I will use a 1/4'' endmill

Thank you