Re: [CAD_CAM_EDM_DRO] Clamping Fixture

Hello Victor

Some time back I posted a couple of projects on the Sherline website. Go
to http://www.sherline.com/CNCproj.htm and look at the church project.
The building and the steeple each have three reamed 0.1247 inch diameter
dowel pin holes. The building and the steeple are then pressed together
with three dowel pins between the building and the steeple. I used a
vise to press the parts together but C clamps work well too.

If you download and unzip the project you will find drawings and Gcode
files for the church parts and for the fixture plates. The fixture
plates replace the steel jaws on a Sherline vise and hold the church
parts aligned with slip fit dowel pins.

I'll try to make time to photograph some large horizontal fixture and
work plates used for making an array of small parts.

Tom Hubin
thubin@...

*********************

Victor A. Estes wrote:

>
> Tom,
>
> What you describe is along the lines of what I have been thinking
> about building over the last several years, I've just have not done it
> yet. I always seem to do it the had way with mutiple setups and have
> not really taken the time to fiqure out a good repeatable fixture/jig
> clamping design for my application. That's what is driving my
> motivations right now. So thank you very much for the description, it
> seems straight forward to me. SOme pics would be great as well if you
> have time.
>
> Thanks Again
>
> Victor A.
> ----- Original Message -----
> From: Tom Hubin
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Sent: Thursday, March 08, 2007 12:31 AM
> Subject: Re: [CAD_CAM_EDM_DRO] Clamping Fixture
>
> Hello Victor,
>
> I often make fixtures for arrays of parts on my Sherline 5410 CNC
> mill.
> FYI, my Sherline 5410 has a center to center area just a bit over 8.0
> x
> 4.0 inches.
>
> I design 1/8 inch or 1/16 inch diameter dowel pin holes into my work.
> Sometimes just for alignment on the fixture but often for accurate
> location in a complex assembly. Dowel pin holes can be drilled
> slightly
> undersize then reamed to perfection. Slightly less than the dowel pin
> for a press fit or slightly larger than the dowel pin for a slip fit.
>
> If you don't need quite this much accuracy then you can work with
> countersunk screws.
>
> In either case, their are usually 2 or 3 plates involved. The bottom
> plate has holes for 10-32 screws to secure to the Sherline table with
> T-nuts. Also, four 0.2505 inch diameter reamed holes near the corners
> of
> my work area. That is, as far back and forward and right and left as
> possible. These four reamed holes are used with quarter inch steel
> dowel
> pins to locate the plate on the table.
>
> The top plate is for the array of parts that I am making. There will
> be
> several 1/8 inch dowel pin holes that match dowel pin holes in the
> bottom plate. Convenient screw size clearance holes in the top plate
> and
> matching tapped holes in the bottom plate. As much as possible I use
> dowel pin and screw holes that will be in the finished parts. However,
> I
> create dowel pin and screw holes anyplace that I find necessary.
>
> Usually I do all the drilling in the top plate, including any
> alignment
> holes. The plate is secured to the table in any number of ways.
> Alignment need not be perfect since all work later will be referenced
> to
> the dowel pin holes.
>
> Then I secure the top plate to the bottom plate with dowel pins and
> screws. Then do any milling and additional work. Then I flip the plate
> over to machine the backside. Then cut out the parts with the mill. If
> they are all screwed down then they won't fly off as you cut away the
> last of the outline.
>
> But suppose your part has tapped holes and not through holes. Then I
> use
> a middle plate with dowel pins and screw clearance holes counterbored
> from the bottom up. So the top plate (or array of parts) is secured to
> the middle plate from the underside of the middle plate. Then the
> middle
> plate is secured to the bottom plate from the top.
>
> For reference, I make a square piece that can be secured to the bottom
> plate using dowel pins and screws. I use an edgefinder to find the
> edges
> of the reference part and define the X and Y coordinates. Then remove
> the reference part and you are ready to go.
>
> So, the bottom and middle plates and the reference part are made once
> and used forever. The top plate is machined into an array of parts.
>
> Tom Hubin
> thubin@...
>
> *********************
>
> Victor A. Estes wrote:
> > Rexarino,
> > Yes this is worth building a fixture/jig for because I will be doing
> > this setup quite a bit.
> >
> > I have been doing this in the past by clamping, milling, moving the
> > clamps, and the milling again, a pain. So it's time to make this job
> a
> > little easier and a little more accurate results on my part.
> > Victor A.
>
> [Non-text portions of this message have been removed]
>
>