A
quick change tool post may be a luxury for a hobbyist, but one that will
be appreciated over and over. On smaller lathes, adding one may require
some modifications.
The South Bend 8k SB1001 8"x18" lathe comes with a four-way turret tool
post. These facilitate changing between multiple tools, but require
shimming tools up to center. Quick change tool posts use adjustable
height tool holders, eliminating shimming.
The Aloris tool post is the
original standard, made in the USA, but there are imports available that
are less expensive. The Aloris AXA comes with a 9/16-18 shaft and a
threaded metal plate that could be machined to fit a compound t-slot.
Unfortunately, the SB1001 does not have a t-slot in the compound so the
compound slide must be modified.
A couple screws, either side of the compound handle, hold the compound
slide in place. Remove them and push the compound slide off. Be aware
the jib that may also slide off.
Tap out the original tool post shaft. It's held in place with knurling
on the post and a pin between it at the compound. Remove the jib set
screws.
Mill off the raised portion, and then continue to make a recess, perhaps
.05". Too shallow and the tool holders may bottom out, too deep and the
compound slide starts looking thin. The cut will need to continue back
towards the handle a bit to accommodate the tool holder rotating. The
metal is cast iron and cuts easily. After finishing the milling, drill
out the shaft hole to 1/2" and tap 9/6"-18tpi.
After milling, the tapped portion is thin and may only have three full
threads. To add turns and spread the load, we add a nut in the recess on
the backside of the compound slide. A 1/2" nut has an outer diameter
that fits well. Simply drill it out, and tap it. Mill one side so it's
flush with the bottom of the recess. Tighten it with a socket and mill
the nut-shaft flush with the back of the compound slide.
The shaft-nut must be flush to the bottom of the slide to clear the
brass compound lead screw nut. A little filing of the brass nut may
improve the compound slide action. This SB1001 came from the factory
with some interference.
The compound is ready to be reassembled.
The completed and mounted quick change tool holder is a nice addition to
this lathe. 3/8" tools work well, with some adjustment travel left in
the tool holders. I've not tried 1/2" tools yet, but they will be close
to bottoming out the holders. Consider this when milling your compound
slide, you may want to go a little deeper.