Modified toolpost and bolts
The stock Taig toolpost is mounted using an Allan-head cap screw through the
toolpost into a square nut that fits the T-slot in the cross slide.
This poses two problems.
- Each time you need to adjust the screw, you need to fumble for an
- Attaching the toolpost to the lathe involves sliding a square nut into
the T-slot. If you do this while the nut is not attached to the toolpost, it
is easy enough, but then you can't see the nut when you are trying to screw in
the hold-down screw. Alternatively, if you leave the nut on the end of the
hold-down screw, you need to manipulate the nut, out of sight below the
toolpost, in order to get it to fit the T-slot.
I hunted for a better way, and found these two blog posts:
I found Irv Bakeland's solution first; that inspired what I did. Only later
did I discover that Lew Bishop had done almost the same thing.
As with Lew Bishop, I modified the hex head bolts used to clamp things to the
cross slide. He did some of his work on a mill, where I used hand tools, but
the results are essentially the same:
Chuck each bolt in the lathe collet to face the end of
the head, making the head thin enough to fit the T-slot.
Hand file opposing flats on the bolt head until the head is narrow enough
to fit in the T-slot.
Hand file flats on the side of the bolt shank so it fits in the T-slot.
Unlike Lew Bishop, who made lever-operated nuts to fit the top of his toolpost,
I opted to use a simple wingnut working against a brass washer. This works
well enough that I don't see any reason to make anything more complex.
I've made a number of mounting bolts, in different lengths, and I've drilled
several pieces of 1/2" aluminum bar stock to fit the bolts. These bolts and
bars have served me very well as furniture for mounting various workpieces and
tools on the lathe carriage. My first use for this furniture was in drilling
the toolpost to clear the new bolts.
Setup for on-axis drilling
The hole in the toolpost doesn't need to be perfectly centered, so my approach
to drilling it out may be overkill, but here's what I did:
- Suspend the toolpost between centers over the cross-slide, and clamp
the tailstock ram in place. This holds the existing hole in the toolpost
exactly on axis, and it holds the toolpost floating about 1/2 inch above the
surface of the cross slide.
- Insert auxiliary posts in the cross-slide T-slots, one on each side of the
toolpost you're drilling. I used 1/2" aluminum bars that were drilled on axis
and held down by some of my modified 1/4-20 T-slot bolts, but you could just as
easily use a pair of stock Taig toolposts for this, if you've got spares.
- Use a C-clamp to loosely pinch the toolpost you're drilling between the
two support posts. At this point, the supporting furniture is all loose,
the only thing that is tight is the tailstock center holding the hole to be
enlarged exactly on center. Also, lock the cross-slide. On the Taig, you do
this by tightening the middle cross-slide gib screw with an allen wrench about
- Gradually tighten the mounting bolts for the suport posts and the
C-clamp. Give each screw or nut a turn until you feel a little resistance,
then give each screw a bit more torque until you feel a bit more resistance,
and so on. The idea is to tighten things gradually so that the centering of
the workpiece is never disturbed. By the end of the process, the workpiece
will be held on center by the clamping furniture.
- Unclamp the tailstock ram, and unclamp the tailstock so you can
back it away. Slide the carriage away from the headstock, remove the headstock
center, and put in a collet and drill; 1/4" in this case.
- Drill the hole. I prefer to do this by disengaging the carriage from the
rack and pushing the workpiece into the drill with the tailstock ram. You
don't want to let the drill meet the tailstock dead center, so you need
something hollow mounted on the tailstock to serve as a pusher.
I used the Jacobs chuck that came with my lathe as a pusher. With
the jaws opened all the way, they're retracted behind the front face of the
chuck and open far enough that they'll clear a 1/4" drill. This is safe,
but I'm tempted to turn, drill and tap a bit of aluminum rod to use as a
drilling pusher before I use this setup again. A Taig die holder
would also work as a pusher.