Hi,

I am about to try milling for the first time (will practice on scrap
material first till I get used to the "feel" of the machine). The main
issue is that I am not sure how to hold down the jobs so they are secure
and I don't mark them (particularly the light gray plastic).


There are 3 different enclosures I need to cut slot in. Below I have
given a brief description along with a link to a details of the
enclosure with the hope it is clear enough for someone who would be kind
enough to take the time to take a look and make some suggestions.

Thanks in advance. (I have a Machining vise and a clamping set with
T-Bolts etc).

A link to each style of box is included below.


1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

http://www.hammondmfg.com/1553.htm


2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

http://www.hammondmfg.com/dwg2b.htm


3/The end plate needs slots cut in it. This plate is 2mm thick. The
actual plate has 4 mounting screws in the corners rather than the 2 shown.

http://www.hammondmfg.com/1455.htm
--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869


Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986

Hi, David.
Do you have access to a bunch of random size aluminum and steel block
cut-off pieces? The sizes need to be somewhat larger than the plastic
boxes you are going to mill. The problem with milling any kind of
plastic is its flexibility. The end-mill bit will flex the plastic as
well as cut it. The result is an "L" shaped slot.

You need to design and mill a box to totally enclose the plastic box,
except for the end you are going to mill the slot in.

The tooling I have done all have a pocket milled to hold the box with
about .10 inch or less of the box exposed above the tooling. Then a
steel plate is machined to size to fit the box. When the tooling and
the plate are clamped in the vice, the plastic box is tightly held by
the cover plate. Now, the plastic box is ready to mill.

I use a stop rod on the vice so the tooling is always returned to the
vice at exactly the same location.

In one case I made the tooling out of a steel block to completely
enclose the plastic box. The pocket is offset in the block so a rather
thin portion is next to the place where the slot it to be made. The
first box to be slotted also slotted the tooling.

The above steel tooling also has 4 holes in the side so it acts as a
template and I can drill circuit board mounting holes in the box.

I think I can find the tooling and send you some pictures if that will
help.

Paul Drahn, President
Jodeco, Inc.
Redmond, Oregon

Paul,

Thank you for your feedback.

I have not used a mill yet (complete novice). The idea of getting the
mill was to be able to make small prototype runs with better results
than cutting the slots by hand with a nibbler.

My experience is predominantly Electronic circuit design. It would be a
little early to attempt milling out a holding jig.

For the metal end plate I was thinking maybe an aluminum block with 4
holes and screw the plate to the block.

The small plastic enclosure I thought could be placed end-on in the vice
but not sure if I would get away with using tin plate between the box
and vice jaws to protect it ? Maybe I could cut a wooden block to fit
into the box to give support ? Really not sure what would work best here.

As for the handheld, that is more problematic as the sides are curved. I
thought maybe put it lengthways into the vice so I could clamp on the
square ends but I don't think this looks stable.

Any other suggestions how I might secure and protect the work without
needing the experience of milling out a jig ? It is a bit of catch 22
until I get more experience. I don't mind messing up a few boxes as part
of the learning process.

Thanks again

wrote:
Hi, David.
Do you have access to a bunch of random size aluminum and steel block
cut-off pieces? The sizes need to be somewhat larger than the plastic
boxes you are going to mill. The problem with milling any kind of
plastic is its flexibility. The end-mill bit will flex the plastic as
well as cut it. The result is an "L" shaped slot.

You need to design and mill a box to totally enclose the plastic box,
except for the end you are going to mill the slot in.

The tooling I have done all have a pocket milled to hold the box with
about .10 inch or less of the box exposed above the tooling. Then a
steel plate is machined to size to fit the box. When the tooling and
the plate are clamped in the vice, the plastic box is tightly held by
the cover plate. Now, the plastic box is ready to mill.

I use a stop rod on the vice so the tooling is always returned to the
vice at exactly the same location.

In one case I made the tooling out of a steel block to completely
enclose the plastic box. The pocket is offset in the block so a rather
thin portion is next to the place where the slot it to be made. The
first box to be slotted also slotted the tooling.

The above steel tooling also has 4 holes in the side so it acts as a
template and I can drill circuit board mounting holes in the box.

I think I can find the tooling and send you some pictures if that will
help.

Paul Drahn, President
Jodeco, Inc.
Redmond, Oregon


--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869


Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986

David wrote:

1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

The end plate is easyest (and will come later).
Unscrew, lay flat onto the table and clamp down. First put masking tape
to where you will clamp. Second, put some plate between workpiece and
clamp. It might be necessary to build some kind of stop that the part
doesn't slip away. Expect this to happen!

2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

Ob boy! You know, that the cases don't have parallel walls? They are
conical. You can't simply clamp it down on one side and mill on the
other. It will be tiltet and bend like mad!
If you have a horizontal mill, you can proceed like with the first part.
Putting the open end down on the table.
If not, you need to weld some table to support the housing.
I would pull out my power drill, bore hole near hole and file.

3/The end plate needs slots cut in it. This plate is 2mm thick. The
actual plate has 4 mounting screws in the corners rather than the 2 shown.

This is easy. Clamp the plate down onto some plastic (Styrol, ABS) that
you can cut a bit into (mill into the plasic, NOT into your table).
Also, use masking tape to protect the part and put some steel/aluminium
flat between the clamp and the part.

You could think about casting some jigs out of plaster (reinforced).


Nick

--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

"David" wrote in message
...
Hi,

I am about to try milling for the first time (will practice on scrap
material first till I get used to the "feel" of the machine). The main
issue is that I am not sure how to hold down the jobs so they are secure
and I don't mark them (particularly the light gray plastic).


There are 3 different enclosures I need to cut slot in. Below I have
given a brief description along with a link to a details of the
enclosure with the hope it is clear enough for someone who would be kind
enough to take the time to take a look and make some suggestions.

Thanks in advance. (I have a Machining vise and a clamping set with
T-Bolts etc).

A link to each style of box is included below.


1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

http://www.hammondmfg.com/1553.htm


2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

http://www.hammondmfg.com/dwg2b.htm


3/The end plate needs slots cut in it. This plate is 2mm thick. The
actual plate has 4 mounting screws in the corners rather than the 2 shown.

http://www.hammondmfg.com/1455.htm
--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869


Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986

It depends a little on how many you need to make...

The problem, of course, is holding an irregularly shaped of probably
flexible plastic so you can cut it accurately without toooo much hassle.

You can put a lot of time and work into making fixturing. But the forces in
cutting plastic aren't all that great, so maybe a different approach would
be adequate.

You can also cast "blocks" that will fixture it nicely, and, although their
useful life probably wouldn't be long enough for true production, they'd
probably hold up for a few dozen/few hundred pieces. Go to a dental supply
and get some material of the sort a dentist uses for making a mold for false
teeth, etc. Then, make a fixture much in the same way as you would make a
mold for casting with your "sample" piece as a pattern. Apply a little
imagination and it isn't hard to visualize how to hold your little plastic
box to make the cuts you need (if there are several, you may need more than
one fixture...).

Jerry

David wrote:

Hi,

I am about to try milling for the first time (will practice on scrap
material first till I get used to the "feel" of the machine). The main
issue is that I am not sure how to hold down the jobs so they are secure
and I don't mark them (particularly the light gray plastic).

There are 3 different enclosures I need to cut slot in. Below I have
given a brief description along with a link to a details of the
enclosure with the hope it is clear enough for someone who would be kind
enough to take the time to take a look and make some suggestions.

Thanks in advance. (I have a Machining vise and a clamping set with
T-Bolts etc).

A link to each style of box is included below.

1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

http://www.hammondmfg.com/1553.htm

2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

http://www.hammondmfg.com/dwg2b.htm

3/The end plate needs slots cut in it. This plate is 2mm thick. The
actual plate has 4 mounting screws in the corners rather than the 2 shown.

http://www.hammondmfg.com/1455.htm
--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869

Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986

Other folks have suggested fairly involved fixturing which I think is a
bit more suitable for modest production runs. What I normally do for the
one or two off projects milling plastic enclosures is to just cut a wood
backer block to provide support underneath where I will be milling.
Clamp the part down over the top of the wood block with the clamp
strap/stud/step block setup and just put some masking tape on the
surfaces the clamp bars will contact to prevent scratches.

Pete C.

Jerry,

Thanks for the suggestion. Maybe even body filler for cars would be good
enough. I only have 1 of each to do for now. The largest run of
prototypes would normally be 10 with maximum of 30. Beyond these numbers
it starts getting viable in terms of waiting time and cost to contract
the job out for someone with CNC facility.

Even a cast of the inside of the square box would help put some "meat"
behind the end panel that I want to mill.

I suppose for the handheld unit I could make a cast in a rectangular box
larger than the enclosure being cut, and then press the enclosure 1/2
into the mold to get a contour. Then use a clamp at each end and mill
from inside the box.

The small plastic end of the handheld enclosure may be troublesome as
there are no mounting holes. I could probably also use a mold to form a
recess to prevent the plate from sliding and then come up with some way
to stop it lifting up.




Jerry Foster wrote:
"David" wrote in message
...

Hi,

I am about to try milling for the first time (will practice on scrap
material first till I get used to the "feel" of the machine). The main
issue is that I am not sure how to hold down the jobs so they are secure
and I don't mark them (particularly the light gray plastic).


There are 3 different enclosures I need to cut slot in. Below I have
given a brief description along with a link to a details of the
enclosure with the hope it is clear enough for someone who would be kind
enough to take the time to take a look and make some suggestions.

Thanks in advance. (I have a Machining vise and a clamping set with
T-Bolts etc).

A link to each style of box is included below.


1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

http://www.hammondmfg.com/1553.htm


2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

http://www.hammondmfg.com/dwg2b.htm


3/The end plate needs slots cut in it. This plate is 2mm thick. The
actual plate has 4 mounting screws in the corners rather than the 2 shown.

http://www.hammondmfg.com/1455.htm
--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869


Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986


It depends a little on how many you need to make...

The problem, of course, is holding an irregularly shaped of probably
flexible plastic so you can cut it accurately without toooo much hassle.

You can put a lot of time and work into making fixturing. But the forces in
cutting plastic aren't all that great, so maybe a different approach would
be adequate.

You can also cast "blocks" that will fixture it nicely, and, although their
useful life probably wouldn't be long enough for true production, they'd
probably hold up for a few dozen/few hundred pieces. Go to a dental supply
and get some material of the sort a dentist uses for making a mold for false
teeth, etc. Then, make a fixture much in the same way as you would make a
mold for casting with your "sample" piece as a pattern. Apply a little
imagination and it isn't hard to visualize how to hold your little plastic
box to make the cuts you need (if there are several, you may need more than
one fixture...).

Jerry



--

Kind Regards

David Huisman
General Manager
-----------------------------------------------------------------------
ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work
(Telemetry, Control, Monitoring, Security, HVAC ...)
A.C.N. 107 441 869


Website : http://www.orbitcoms.com
PO Box 4474 Lakehaven
NSW 2263, AUSTRALIA
Phone: 61-2-4393-3627
Fax : 61-2-4393-3685
Mobile: 61-413-715-986

David wrote:
Jerry,

Thanks for the suggestion. Maybe even body filler for cars would be good
enough. I only have 1 of each to do for now. The largest run of
prototypes would normally be 10 with maximum of 30. Beyond these numbers
it starts getting viable in terms of waiting time and cost to contract
the job out for someone with CNC facility.

Even a cast of the inside of the square box would help put some "meat"
behind the end panel that I want to mill.

I suppose for the handheld unit I could make a cast in a rectangular box
larger than the enclosure being cut, and then press the enclosure 1/2
into the mold to get a contour. Then use a clamp at each end and mill
from inside the box.

The small plastic end of the handheld enclosure may be troublesome as
there are no mounting holes. I could probably also use a mold to form a
recess to prevent the plate from sliding and then come up with some way
to stop it lifting up.

Use aerosol foam from the hardware store. Wrap your workpiece in plastic
wrap.

"David" wrote in message
...

Thanks in advance. (I have a Machining vise and a clamping set with
T-Bolts etc).

If your only milling plastic then I don't see why you couldn't use wood to
make the fixture/clamps.


AJS

In article ,
(Nick Müller) wrote:

David wrote:

1/ This handheld unit needs a slot in the top to enable viewing of a
small LCD display. (refer left most picture). Also required is a small
slot in the end plate.

The end plate is easyest (and will come later).
Unscrew, lay flat onto the table and clamp down. First put masking tape
to where you will clamp. Second, put some plate between workpiece and
clamp. It might be necessary to build some kind of stop that the part
doesn't slip away. Expect this to happen!

2/I am using the light gray version of this box. A slot needs to be cut
at each end for connectors.

Ob boy! You know, that the cases don't have parallel walls? They are
conical. You can't simply clamp it down on one side and mill on the
other. It will be tilted and bend like mad!

Yes. The sides are sloped at 2 degrees, so the part will come out of
the mold. Another problem I have is that steel tools cut the
zinc-aluminum die metal so easily that it's hard to keep the drill from
wandering unless everything is well clamped and perpendicular. Holes
will wander even if one has done the whole centerpunch and pilot drill
dance, because ordinary twist drills can easily cut sideways (like a
mill) in such soft metal.

The box manufacturers (Bud, Hammond, et al) have mechanical drawings on
their websites.

Using a 2-degree wedge from MSC, one can machine a set of clamp blocks
that will fit the box precisely. Or, machine a filler block that will
fit inside perfectly. For this, a hardwood like maple should be
adequate for a short run.

Joe Gwinn