When I straightened mine, I used the drill press as an arbor press
with a dial indicator to show quill travel. It took deflecting the
gib strip about 0.015" to remove the 0.005" curve it initially had.
Since I was measuring quill travel I used relatively large risers to
support the piece. Using calibrated supports would eliminate the
need to measure actual quill travel.
I lapped with the strips in place, instead of lapping them
separately. Since I was trying to improve the overall contact area
it seemed logical to lap with them in their assembled location. By
the same token, I only lapped until I had reasonable surface
contact. By minimizing the amount of lapping I avoided much risk of
making the gibs convex; the actual lapping was consistent with
loathing of the process. (Used to have to do it on relatively large
steam fittings in a previous incarnation.)
Roy
--- In 7x12minilathe@..., "Paul Moir" <paul.moir@...>
wrote:
There isn't much to add to the instructions at mini-lathe.com.
Begin
by determining if the the gibs are straight enough to be lapped and
first unbend them as necessary. It is pretty easy to get an idea if
your gibs or surface plates are flat. Just place a decent all-steel
ruler's edge up against the surface and hold it up to the light.
0.0005" error will be very obvious.
I cannot find the original source, but someone here suggested using
a
drill press as an arbor press to straighten the gibs. Support the
ends with pieces of sheet metal and press down on the centre. By
using progressively thicker pieces of sheet metal, you don't risk
over-bending or breaking the gib. I found this works well.
It's hard to lap the surface of the gibs so that they don't become
convex along their width since they're thin and hard to hold (not to
mention sharp!). I found it was very much worthwhile to make a
holder
for them. I just ran a short scrap block of oak through a table
saw,
with the blade set to cut about 3/32" or so depth, with an angle to
match the gib's sides, and then widened it until the gib could be
tapped into the slot. Naturally the same could easily be done with
a
sharp chisel, etc. Could even superglue it to a block and release
it
later with acetone.
I hope this helps. If your gibs are not straight, this will
definitely make a big difference on the machine.
--- In 7x12minilathe@..., Dennis Thompson <dbt@> wrote:
I need to lap the gibs on couple of my machines I recently
purchased, (with little time to use/clean, etc., 'till now).
I've
never lapped gibs - any particular tips?
Dennis (really new at some of this)
Cummins Mini Mill, freshly unpacked
HF 7x10
Cummins 7x12
