On 7/23/2024 6:15 AM, Jim Wilkins wrote:
I didn't suggest following with a second smaller reamer because I
couldn't think of a way to ensure it aligned with the first radially and axially, the necessary extended shank could let it wander and there's no
easy way to know when to stop.
Milling machine does a fair job with alignment as long as you don't move anything. The reamer will follow the existing hole.
There is a saying, "Drill fast, bore straight, ream to size." Somebody
else must have said it first, but I've never heard anybody else say it
exactly that way. For now I am the guy who said that saying until
somebody tells me different.
It's a mold so depth is easy to find. Just open the mold and look. The
pin slot was already 3D machined fairly accurately. 0+ to -.001 or
better anywhere along the slot. The reamer(s) just needs to kiss the
hole to make it a smidgen smoother. Its a lead casting mold so as long
as the pin sets at "about" the right position castings will come out
fine. You don't get flashing with upto .004-005 gaps unless the mold
and lead are overheated. I vent .0015 to .003 every day without issues
on gravity casting lead molds. (Resins and injection have their own set
of issues and tolerances.)
I have already tested fit without reamer cleanup and it "would work" as
is. I'd just like it to set set a little deeper for ease of dropping in
the pin. I think just kissing off the machine marks from the original
3D op will be just right.
I'd ream to position the large head of
the pin relative to the surface, cut off the small end and bin it for
later. For a small pin in a deep hole I'd use a dowel or roll pin instead.
A straight pin would work, but the customer wants a taper pin because it
will theoretically knock out easier. It will. With a straight pin you
have to DRAG the pin out of the casting for the entire length. With a
taper pin a light tap with a soft face hammer and it just falls out.
***
I'm cutting a mold for somebody that casts a body with a through hole.
There are nominal dimensions, but a tapered pin that knocks out easily
would be acceptable.
***
I may not have done an adequate job of describing the application. The
taper pin is not for "joining" or "aligning." Its to be used as a
removable core.
FYI: I make similar casting molds all the time with straight pin cores,
and they work just fine. They do require more effort to remove, but
they work just fine. In this case its a custom mold, the customer has
no experience with lead casting, and they are a bit OCD. Its easier to
charge them for the work than to argue with them and it needlessly burns
less of my time.
Similar mold I make with straight pins larger and longer than the custom
mold above.
https://www.cncmolds.com/webstore/lead-casting-molds/weights-lead-line-for-nets/ten-count/weight-net-sinker-1/4-pin-4-cavity
Hammerlock chain links have another way to retain a pin. It's turned
smaller in the center and passes through a nested pair of large split
roll pins with their slots opposed. They expand to let the end pass,
then shrink onto the smaller center. Unlike shackles one end is no
larger than the bow and fits into chain links. The pin is fairly easy to hammer or squeeze in and punch out. https://www.riggingwarehouse.com/rw-lifting-rigging-hardware/rw-connection-repair-links/rw-hammerlocks.html
This is the preferred fitting to splice one chain to another,
hammerlocks are wider to accept multiple chains for slings. https://www.etrailer.com/Accessories-and-Parts/Titan~Chain/TCML13.html?feed=npn&gad_source=1
I had to go beyond hardware store G30 chain to a logging equipment
supplier to upgrade my hoisting gear for the heavy logs.
The drill press vise would be for the mill, to hold large but light
material, mainly sheet metal for electronic control panels etc, plus
give more badly needed working space under the spindle for upright jobs
like 5C collet blocks.
Did you look a the slide lock vise? I have actually thought about
making a second one to go on the South Bend mill. In a t-slot table the clamping screw for the split block could also lock it to the table with
a t-nut making all adjustment and movement fast and easy from the top of
the table. When I don't need it I can just loosen the knob and slide it
out of the way.
I don't know how flimsy of material you plan to drill, but anything
heavy enough to not buckle when clamped in a vise works in the step jaw
just fine. I drill aluminum sheet as thin as .080 as needed. depending
on the alloy could go thinner. Much thinner and I use double stick tape
or painters tape and super glue to a backer. The sacrificial backer
would then clamp up in the vise just fine. They are small. but there is
a vertical groove and a horizontal groove milled in the moving jaw of
the vise for round stock, and there is no reason I couldn't use a 5C
collet block in it either.
For reference. I once made a fixture for milling paper. Plane old
ordinary .003 thick printer paper. Talked about it on this group. I
used it to create neatly printed custom button labels for a hybrid phone
system back when I was still contracting.
My Clausing 8525 mill is the early version
without the column riser block.
Its my understanding that riser blocks for mills were options. Not
included. You unbolt the head, lift it up, slap in the riser block, and
bolt it back together. I wouldn't mind an additional six inches on my
South Bend, but usually I can bolt on a right angle plate, and hang the
part off the table if I need to drill something longer than my Z
clearance. I have to swing the head to one side so the long part can
clear the knee, but its made to do that.
I had to remove the hard jaws to clamp 6
squares of 5" wide 14 ga steel for a hole saw, and wider steel would
have been better for hoist baseplates. At Unitrode I replaced a
worn-out drill press with an RF-31 mill
I had an RF-31 for a while. I didn't get much use out of it, but I seem
to use my South Bend knee mill a lot. A true 5HP (Running on 7.5hp VFD) spindle makes short work of some roughing and truing jobs even if I do
have to turn the handles.
drill and bought an 18 lb 6"
drill press vise for it instead of a 70+ lb milling vise that could
crush a foot. Machine work for electronics is mainly on aluminum sheet
and light extrusions, and no one wears steel toe boots.
The big advantage of the slide lock is it can't spin, its light weight,
and its easily removed or installed. Of course you can make it any size
you need.
--
Bob La Londe
CNC Molds N Stuff
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