On 9/13/2019 11:00 AM, David Billington wrote:
On 13/09/2019 15:49, Bob La Londe wrote:
On 9/12/2019 3:15 PM, David Billington wrote:
On 12/09/2019 22:51, Bob La Londe wrote:
On 9/12/2019 4:33 AM, David Billington wrote:
On 11/09/2019 23:11, Bob La Londe wrote:
On one of my machines I pulled of the pair of lock down vises I
normally have on the table so I could mount some custom fixtures to
machine a mold that was almost the full work envelope of the machine.

After I finished I had to put my pair of vise back on, align
them and align them to each other. Not that long ago (a few years
atleast) that would have been a daunting task. I have gotten to the
point that I expect them to be within the range of my test indicator on
the first try... and they almost were, but getting the vises within 50
thousandths is not the goal of course. LOL

I quickly got the first squared up on the table, and proceeded
to the second. Of course I tighten the hold down clamps they shift a
few thousandths. Lightly tapping with a hammer and going back and forth
as I bring the bolts down as far as I dare tighten them without to much
fear of damaging the table gets me within about a thousandth across 2
six inch vise with a 3 inch gap between them.

One vise. No problem. five minutes any day of the week, and
much faster on a good day. 2 vises... not a "problem," but tedious.
Maybe 20-30 minutes. Maybe longer. I didn't really pay attention to
how long it took. Probably also not all that necessary as I use soft
jaws with a premachined step on the bottom so I can fully face them
square to the travel of the machine. Then I add a step in the top of
the jaws, or in this case take a skim cut on the step that is already
there. I can use the step for a high hold or for thinner parts, and use
the entire jaw when necessary.

Anyway, none of that really matters. Just background until I
get to the point. The point is even clamped down as hard as I dare the
vises still can move with only a modestly firm tap with a hammer. Its
only a few tenths to a couple thou depending on the blow, but it does
move. I know a hammer blow delivers a deceptively large amount of
force, but still. It made me wonder how easily those vises really move,
and if there was something I could do or even needed to do to more
firmly affix them in place. I tend to mount a vise or in this case two
vises and only remove them if I have to. Often even temporary fixture
plates are just mounted in the vises. The two I just remounted on the
table were last off the machine over a year ago. I've cut a lot of parts
in those vises. Maybe hundreds.

So what kind of "normal" cutting fores might cause those vises
to move. I put the word normal in quotes, not because I wanted only
include safe cuts that work every time, but also things that can happen,
but maybe shouldn't. I know a crash with a fly cutter could do as much
damage as a hammer. How abut a 1/2 inch mill entering a piece of hard
steel or a face mill banging on the edge of a work piece.

I know about the sheet of paper trick (it does work really
well), but I cut 95% aluminum with flood on that machine and having
something between the vise and the table that can not just hold but wick
moisture is a bit disconcerting. The only other thing I could think of
was to add some stop blocks bolted to the table up against the vise.


I'm wondering if your clamps may have the threads bottoming out
so not providing the full clamp load to the vice, I've seen it before. I
once did a job with the vice clamp bolts done up finger tight as I had
forgotten to use the spanner to fully tighten them, it did eventually
shift but I did a surprising amount of work before it did.



They certainly didn't bottom out in the table, but I suppose they
could be close in the nut(s). I'll see if I can get a hook tool in
there to see how deep the ends of the bolts are.

Maybe I could have been clearer, all the BP 5/8" T nuts I have are
tapped so the studs won't go all the way through the T nut, the thread
will bottom out in the T nut and not hit the bottom of the slot. I have
experienced situations where the nut will hit the end of the thread at
the top end of the stud and only minimally clamp the vice or fixture.
Worth checking that this isn't happening with your clamping arrangement
what ever it is. If not the case must be some other issue but worth
checking.

Regarding slot damage I have only seen that on a badly abused
BeaverMill table and then the current owner knew that the previous owner
had been using the wrong sized (too small) T slot nuts which resulted in
the damage to the underside of the T slot.



I understood. I have 7 mills. 6 currently in operation. I have
t-nuts in the slots on all of them. I have also made t-nuts, but when I
make them I tap all the way through. Its a lot easier to make sure you
won't bottom out in the table before hand than it is to make sure you
won't bottom out in a t-nut.

Ok one of them doesn't really count. Its a mill drill that doesn't
even have a fine feed, but it does have a vise bolted to the table. 5
real mills in operation. LOL.

I have a fairly decent stock of heavy washers, and have made a fair
number of spacers so I could use the bolt i have handy instead of
spending all day looking for one or going to the store. Even when I
don't need one for length I try to use atleast one because it acts like
a thrust bearing and the vise moves less when I torque it down. It also
spreads the load from the bolt a little, so a bolt head is less likely
to damage a cast fixture, angle plate, vise, etc.

One set of six parts cut so far, and the vises have not moved. Maybe
I was just being paranoid.

Now I feel inadequate as I only have 3 lathes and 2 mills but they
pay their way and always useful, the small CNC mill is a work in
progress. A mate down in Cornwall mentioned recently he met a guy down
at the local mine with 30 lathes, then largest being 12' diameter
capacity and a 30' bed, I guess he has the need, space, and connection
to the national grid.



I often struggle to keep them all going. I just can't do CAD/CAM work
fast enough. But there are days when I have them all going and realize
I need to do something else, and just have to wait. Except for the
mill/drill all my mills are CNC. That being said I've made parts in a
pinch in a hurry on the mill/drill too. LOL.

I'd love to have a CNC lathe, but the cost for something decent always
makes me think twice. Also the electrical budget in my shop is very
tight. Not money, but amps. I just have a single phase 100 amp sub
panel feeding the whole shop. I often find myself adding up what's
running in my head and guesstimating how close I might be to tripping
the main if I start just one more machine. Its one reason I am the only
one with a remote for the overhead doors. LOL. I do have three lathes,
but only 2 in operation. Well not counting my wood lathe. It works,
but I only use it once or twice a month. So I guess I have 4 lathes.
Now shall I start counting badsaws and drill presses. LOL. I found
duplicate equipment saves me a lot of time for jobs that are done
repetitively and repeatedly. One lathe is set to do just one job.
Radius the end of dowel pins. 2 drill presses are dedicated to
automatic tapping heads, etc etc...

As a one man shop an idle machine still saves me time when I need it if
its dedicated and always setup for a particular job I do routinely. I've
debated a gang drill press table so I can pass certain jobs down the
line, but they are expensive. Even used they cost a bit. I might make
one out of cheaper drill presses sometime... if I ever have the time.