Why not mortise the treads in then use two threaded rods going across
between stringers just below each tread?? I'd be inclined to drill and put
two half inch dowels in each end of the treads through into the stringer.
( belts and suspenders so to speak).
I am thinking that that lags would twist and loosen or cause splitting.
If the treaded rods appearance bothered you they could be hidden by a square
piece of 1.5 by 1.5 rabbeted out to capture the rod and enclose it under the
tread.
Randy
"habbi" wrote in message
...
I tried in rec.woodworking but nobody could help. I want to build a pine
timber straight staircase. My stringers are 4 X 12 and the treads are 3 X
11. The wood is freshly sawn so I don't think moritising the treads into
the
stringers will be a good idea because of shrinkage. I was thinking of
simply
lag bolting the treads in place and then everything could be tightened as
it
dried. Threaded rod through the treads would be nice but drilling a 4'
long
hole through the 3" thick treads would be tricky. Any other ideas out
there,
I don't want to re-invent the wheel.
Thanks