Welcome to the forum . I'm sure the experts will chime in soon . But seeing as you've introduced yourself now I'd repost in the router table thread as you will get more responses .
I'm new at this myself but I'm going to guess the sub fence is for jointing among other things .
The offset lets you straighten out wood so they fit together with no gap .
I'm guessn , so I'll leave it to the experts.
Simmy I was going to mention that it helps the others help you if you fill in your public profile a bit .
A first name is always nice too
Welcome to the forum Simmy. This is from Jessem's site.
The Mast-R-Fence II has been developed with high density fiberboard sub-fence faces that have been edge banded for long life. The sub-fence faces can be adjusted tool free with convenient locking knobs on the backside of the fence. Our dust port fitting is designed with an inside diameter that accepts a 2-1/4" diameter vacuum hose fitting and outside diameter that accepts a 2-1/2" vacuum hose fitting. Also, included with the fence is our unique fence face shimming bars. These bars are made of anodized aluminum with one side designed to offset the fence face 1/32" and the other 1/16". When not in use they conveniently store on the backside of the fence.
I think what they are saying is that the sub fences can be adjusted to open or close the gap around the bit and the face shimming bars are used to make progressive cuts to get to a finished profile and they can also be used on the outfeed fence for a jointing cut.Shimming the faces is handy where you are going to do more than one piece and the cuts are so heavy that they need to be made in stages. You would set the fence for the final cut and then use the 1/16" bar first, then the 1/32" bar, and then no bars for the final cut.
A forum community dedicated to router and woodworking professionals and enthusiasts. Come join the discussion about different types of routing and routers, shop safety, finishing, woodworking related topics, styles, tools, scales, reviews, accessories, classifieds, and more!