Anyone make their own line boring bar/equipment? It doesn't look that hard
to make and could be handy on jobs that are too big for machine tools. Just
wondering if there are any good plans or project info on these. The stuff
looks pretty expensive to buy new for what it is.
"RogerN" fired this volley in
I made a simple jig that mounts the work on the cross-slide, and holds
the boring tool between centers. It allows me much longer bores than a
single-ended boring bar mounted in the tool holder would.
It's really nothing more than a plate to which I clamp or screw the work.
The boring bar is a piece of 5/8" stock with a hole for the tool bit and
a hole for a setscrew, plus center pockets on both ends. Drive it with a
About the only drawback is that the bore size is limited to the amount of
tool overhang you can afford; with my little 1/4" bit, that's about
1.25"(or a bore of 2.5" max) before chatter kills the job. And, of
course, you have to adjust the tool on every cut, rather than moving the
But it works.
This is essentially how the original boring machines worked. Lots of early
automobile engine blocks were actually bored on lathes.
Some of the old English MAP books show miniature versions of those old
boring setups on lathes. Brit lathes, which traditionally have T-slotted
cross slides (or saddles; I forget which) are ideal for that work.
Haven't got there yet, but I'm with you. I need one and they seem to be
priced too high for what they are. At some point when I asked about it
getting an old bridgeport head (from folks rebuilding and upgrading the
head) was suggested as a power-unit & feed option. I've also seen
mention of getting one from army surplus, but have never seen such
A lot of that type of thing is specific to the job at hand, locomotive
steam cylinders, VW engine cases, compressor shells, car engines,
etc. One of Guy Lautard's Bedside Readers had a description of such a
rig and some of Colvin and Stanley's works described what they built
up in locomotive shops to redo cylinders in situ. The Model Engineer
magazine had a lot of such setups on the old Brit lathes, they had T-
slots on the carriages so were easy to rig up. The cutter bar spun
between centers and the work was fastened on the carriage and
traversed with same. What you need to build is pretty much determined
by what you need to machine. A lot of what they used to do with such
rigs on a lathe is now done with boring heads on a mill. Basically
all you need is a tool holder, a way to guide it through the rough
bore, a method of spinning it and another one to periodically move it
down the line. You'll also need some way of fastening the works so it
doesn't move relative to the workpiece. The last could be easy or
could be hard, depending on what you want to work on. A star wheel
advance for the cutter is pretty easy to rig.
They have a motor on a linear slide with a hand crank screw to feed. A bar
with holes drilled and broached for tool bits, and holes drilled and tapped
for the set screw. There's also pieces to mount a bearing and center the
bar. The pictures of line boring bar in the dropbox looked like it would be
much more difficult to construct and handier to use. I guess to me it just
looks like one of those items that would be cheaper to make than buy, the
eBay version that is, maybe not the dropbox version.
I would guess someone could run with the idea and make portable machine
tools that you could bolt or weld on large equipment to do machine work.
Seems like it would be interesting for HSM'ers with big ideas, limited
space, and small budgets.