skamp
Well-known member
I think it would be a little more complicated as the SDS bit end is wider than the shank. For instance the bit head (say first .50" of the bit) is a bit wider than 7/8" (my bosch is .906) and the shank is smaller than 7/8" (.826). If you use a tube with a single ID I think you would still get some wobble as the shank can move within the tube as soon as the bit head exits the bottom of the tube hole. It may be best to use a slightly bigger ID tube and after inserting the drill bit in the tube insert a sleeve that decreases the ID of the tube to match the diameter of the shank part of the bit, almost like a bearing. I hope that makes sense.I think if you look at the directions for the anchors, they say do not use a pilot bit.If you egg out the hole you could end up with a very dangerous situation.Why don't you make up a steel template with 6" pcs. of 7/8"ID steel tubing welded to a pc of 1/8" plate.Pin it down with a couple of 1/4" pins and the tubes will hold your bit nice and straight.Sort of along the lines of this JR Smith setting gauge we used to use in wall hung toilet rough-ins.If I get 1 of these lifts I will make up a template for drilling.If you don't have to think or worry about placing the holes you can be much more accurate in your work!![]()
I think having something like this would be a huge advantage for installation. I just ordered my MaxJax yesterday. I did a test hole over the weekend and I was not perfectly perpendicular and it was hard to keep the bit straight with all that movement of the hammer drill. I have a post tensioned slab and really do not want to cut out sections, although my column placement is within a 4' x 4' area for each column so could cut out the concrete as a last resort.
A jig like this would help me get it right the 1st time. I have thought about making a jig like you mentioned out of 3/4" plywood on the bottom to allow for the larger bit head. On top of that would be 2x12 (maybe even 2 2x12’s) bored to the exact diameter of the bit shank. I would use steel dowels or something to align the plywood and 2x12. I position the plywood in place on the concrete and duct tape or use industrial 2 sided tape to hold it down so it stays in the same place through all 5 holes. For each hole I would place the drill bit in the plywood, slide the 2x12 down and mate it to the plywood via the dowels. I would of course make the plywood and 2x12 template from the column base. Thoughts?
Steve
Last edited:

