On 2009-02-14, Michael Koblic wrote:
Jim Wilkins wrote:
[ ... ]
Looking in Advanced Machine Work that seemed to be the only toolpost then.
In fact they do not discuss toolposts much at all.
Because there was only one common choice back then. It was when
production lathes like turret lathes came along where the ability to
quickly change the tools and have them repeatably positioned became
important. First, indexed turret toolposts, later quick change
toolposts of various sorts.
Ed described their versatility very well. I made this one from a bolt
to be able to use the lathe:
http://picasaweb.google.com/KB1DAL/T...59874580966978
The initial bootstrap "tool holder" was a strap clamped by bolts and
fender washers trimmed to fit into the tee slot on the compound. The
chain-drilled slot was very rough at first but that didn't matter,
only the spherical washer and the bar that rests on it need to be well
finished. I fitted the bar by smearing blueing on the washer and
repeatedly filing off the contact marks, mostly with a coarse rasp
that left the crosswise lines. The clamp bolt should be hardened or it
will mushroom on the end, as you can see. I will need to grind that
one down with a Dremel to get it out.
OK. In the picture the rocker bar is "upside down". Now I see why they
called it a rocker toolpost. In a lot of the literature and web references
this feature is by no means obvious.
:-)
Looking at it I wonder if the slot was milled in the threaded part of the
bolt could one not use a nut or two to adjust the height of the tool?
I've got some small ones designed for Unimat lathes which have a
two-part ring without the rocker feature. You adjust it for the needed
height by turning the top part which is threaded into the bottom part.
The bottom ring has a raised part which engages the T-slot so it will
not turn while you turn the top part.
Aslo, how is the toolpost held on the crosslide? I take it there is a
capscrew that goes through the hole in the bottom and screws into a tee-nut
which then goes into a tee-slot? Or does the whole thing screw down directly
into a taped hole in the crosslide (or compound)? Given the nature of the
rocker bar and its position the capscrew length must be fairly critical so
that it is long enough and not too long to interfere with the bar.
Looking at the image in the URL left quoted above, look at the
bottom of the toolpost. It is turned to a diameter and thickness so it
fits into the T-slot cleanly. The ring and rocker press on the top of
the compound when the tool holder is clamped in place by the screw at
the top. The traditional ones had a square head screw with a flange so
standard wrenches which also fit other clamp screws and such could rest
on the top of the screw for easy access when you need to change
something. Once you clamp down with the screw, everything is firmly
held in place.
I've seen some with a two-part base -- the round one shown
there, and a rectangular one with a counterbore to accept the round base
of the normal toolpost. This is done mostly (I think) to adapt a
smaller toolpost to a larger lathe compound.
Instead of the spherical washer and rocker bar you could use a stack
of large washers or a section of water pipe. A threaded joint cut from
pipe and a fitting would be adjustable for height.
Similar to (but cruder than) the one for the Unimat which I
have.
As Ed said they
have no real advantage in use, but they are easy to make from common
hardware with simple equipment. That one was turned between centers
and drilled a little crookedly on a drill press.
And the "between centers" explains the apparent hole in the
center of the bottom -- it was for making the post, not for a screw to
secure the post in place.
[ ... ]
This is the tool post I like best, the Multifix, which is quick and
solid like an Aloris but rotates almost like a rocker post. Chinese
clone tool holders from Tools4cheap fit the Swiss center column
perfectly.
http://picasaweb.google.com/KB1DAL/H...33382447691698
I found it for $50 while on a treasure hunt for a used Aloris or new
Phase II.
That is a steal! How many tool holders came with it for that
price?
In all honesty I think I am jumping ahead of myself. I think the first
toolpost will be something very simple
http://www.metalwebnews.org/mr-tools...ng%20lathe.pdf (page 6)
just to establish that the concept actually works. However, I now know more
than I did before and when (if) it comes to making a permanent toolpost the
choice will be easier
O.K. The whole design of the lathe shown there is rather crude,
but should work for light cutting at least.
Good Luck,
DoN.
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