"James Waldby" wrote in message
news

If you cut a groove or slot, or mill a horizontal surface,
then yes, the Z-axis should be locked -- ie, the fine-feed
meshed, the vertical gib tightened by handle on side of
head, and the limit block tight against the bottom of the
head. If you set the limit block first, that should keep
the depth from increasing beyond what you want.

I repeated the measurements and the change is more like 3-4 thou. Between
myself and the sucky caliper I got it wrong first time.

In previous post, I wrote:

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

I forgot to mention the alternative of setting the zero so that
the indicator reads zero when you are at the desired depth. If
you do so, then varying thickness of metal you are drilling
into won't matter, as long as the surface not being drilled
through is clamped against the same reference surface each
time.

I should look at that. However, I tried the shimming and I suspect it is the
way to go. I just used an improvised 0.13" shim which gave me one and a half
turns of the screw. I can make something up to be 0.145" thick and use it
every time. It will give me 2 turns of the screw and for the application it
does not need any more. Then the thickness of the plate will not matter: If
it too thin for the drill to go through with this shim it would be too thin
to use anyway.

--
Michael Koblic,
Campbell River, BC