June 2006 33
by Derek Moran
The Slot Machine Fixture consists of a base unit and the Slot
Machine itself, fitted with three adjustable nylon machine-screw feet.
All the parts and hardware for the fixture, ready for assembly.
There is a complete bill of materials on the plans.
The feet allow you to set the height and angle of the hinge pocket.
The radial marks on the hex-head screws help keep their rotation
synchronized.
The completed base assembly. The mark on the platform is the
centerline of the hinge-pocket cut. This is a fast and easy project!
Slot Machine Fixture
THE GREAT PLANES Slot Machine was one of the first tools I
bought when I returned to modeling several years ago. This little
marvel will cut a beautiful hinge pocket in seconds.
I invented the fixture presented here to enable me to
consistently place hinges in proper alignment. Whether you build
from kits or from scratch, this device will improve the speed and
quality of your hinging task.
The fixture consists of a base unit and adjustable-height legs
installed on the Slot Machine. Construction details, including a
bill of materials, are outlined on the plans. This device is quick
and inexpensive to build; most of you will probably find the
materials in your scrap box and odd-parts collection.
You can use any convenient material for the three base parts;
MDF (Medium Density Fibreboard), plywood, and even real wood
will work fine. If your material varies from the nominal 5/8 inch,
adjust the spacer’s thickness so that the platform’s working
surface is 11/4 inches above the base. I used an old particleboard
shelf for the unit in the photographs.
The melamine coating looks nice, but it’s unnecessary.
Whatever the material, the working surface of the base must be
smooth to allow the feet to slide easily.
There are three geometric relationships to maintain as you
build the base.
1) The base must be flat. The working surface of the platform
must also be flat and parallel to the base.
2) The base fence must be perpendicular to the base.
3) The platform fence must be perpendicular to the base fence.
The slot on the base allows you to use a C-clamp to hold the
stock on the platform. The slot will fit most long-reach clamps
A great tool made even better!
Accurately cut hinge slots in any material with the Great
Planes Slot Machine and this simple-to-build device
with a 2-inch opening and 31/2-inch depth. Be sure to use a
backing block so you don’t mar or crush your workpiece. The 5/8-
inch-diameter hole is convenient for wall storage.
Each standoff has a boss that is turned to an interference fit
with the counterbores of the Slot Machine. The fit must be tight
enough to resist the torque of rotating the feet. A drop of thin
cyanoacrylate glue can lock a standoff that is not quite tight
enough.
I chose nylon machine screws for the adjustable feet so they
would not ruin the base. If you substitute steel or brass, jam nuts
will be necessary to lock adjustments. Jam nuts are rarely needed
with nylon screws because their Class 3A thread form is a tight fit
with the Class 2B standoff thread. I selected 6-32 threads because
the pitch conveniently matches the fractional thickness of balsa
stock. Thus to raise or lower the machine 1/32 inch, you rotate each
screw one full turn.
Precisely aligning the tool is accomplished in four simple, logical
stages. Be aware that there is some interaction between the pitch
and roll axes and the elevation. If you tilt the cutting blades
downward, the entire machine must be raised slightly to maintain
the same center height. By following this procedure you will avoid
most interactions.
You will need balsa for test cuts; a piece of medium-hard (8-12
pounds per cubic foot) measuring 1/4 x 1 x 36 is ideal. Check this
material at several locations along its length with a micrometer or
calipers to make sure the thickness is consistent. It doesn’t matter
what the thickness is as long as it is the same (within a few
thousandths).
Initial alignment is done by eye. Since the test stock is 1/4 inch
thick, we want the centerline of the cutting blades to be 1/8 inch
above the platform. At the same time the cutting blades should be
parallel to the platform when viewed from the front and the side of
the base. Adjust the feet until the blade position looks okay.
It’s time to cut a few pockets. Hold the test stock securely
against the platform fence with your left hand. Hold the Slot
Machine against the base fence with your right hand. Advance the
machine, maintaining contact with the base fence, so that the
cutting blades just touch the balsa. Push the trigger switch with
your thumb and then gently advance as the blades cut the pocket.
Proceed with fine adjustments, starting with alignment in roll.
By roll I mean the side-to-side tilt of the pocket as viewed from
the stock edge.
Cut two pockets approximately 3 inches apart. Partially insert a
hinge in each slot and place a straightedge against the hinge tabs.
Both hinges and the straightedge should be collinear. Raise or
lower the front left foot to make corrections.
Align the pocket in pitch: the dive or climb of the pocket after
34 MODEL AVIATION
The author cut these hinge pockets in 1/16 sheet balsa. He used
Great Planes GPMR4015 blades (.008 thick) and modified them to
cut a 5/8-inch-wide pocket. This setup works well for small nylon
hinges such as Klett RK2 and Du-Bro 119.
If you don’t have access to a lathe, a drill press can turn the bosses
on the standoffs. Mount a left-cutting lathe bit tightly in a vise and
securely clamp the vise to the drill-press table. Tap the table
horizontally to adjust the infeed; advance the stock with the quill
downfeed. Concentricity and finish are noncritical. Make light cuts
and be sure to take safety precautions.
Cutting hinge pockets is easy. Hold the stock against the platform
fence with your left hand; activate the trigger switch and advance
the Slot Machine with your right.
Cutting forces are not high, so you can usually hold the stock with
your hand. The base has provisions for a clamp, for unique situations.
Photos by the author
it enters the stock edge. Cut a new pocket
and then insert a long strip of credit-card
plastic that is the same width as a hinge.
Sight this from the side; any error in pitch
will be magnified by the length of the strip
and can be easily seen. Raise or lower the
rear foot to make corrections.
Center the pocket’s elevation on the
stock edge. Cut a pocket and then flip the
stock top to bottom. Advance the
machine’s cutting blades to the slot and
inspect it closely.
If the pocket is above the blades, raise
the machine half the distance. If the pocket
is below the blades, lower the machine
half the distance. Raise and lower by
turning all three feet an equal amount. The
pocket is centered when the cutting blades
will enter it without rubbing on the top or
bottom surfaces.
Once the machine is aligned, add index
marks to the feet to help keep their
rotation synchronized. Make marks with a
fine-point Sharpie pen, drawing a radial
line that is parallel to the direction of the
cut.
At this point you can adapt to different
standard stock thicknesses by counting
turns of the feet. If the machine is adjusted
for 1/4-inch stock and you want to cut
pockets in 3/8-inch stock, unscrew (raise)
all three feet exactly two turns.
However, don’t blindly rely on this
feature because balsa stock often varies
from its nominal thickness. Always verify
your adjustment by flipping the stock top
to bottom as described in the preceding.
Mark the platform to indicate the
centerline of the cut. Use this mark to
locate the stock when cutting pockets for
your model.
Clamp a piece of stock to the platform,
against the fence, and cut a pocket. With
the stock still clamped to the platform,
place a mark on the fence directly below
the pocket centerline. Remove the stock
and extend the mark along the platform
and spacer using a square. Use the Sharpie
as before.
This fixture will cut hinge pockets in
most common construction situations. Plan
hinge locations early in the building
process and cut pockets while your stock
is easy to work.
Whenever possible, cut hinge pockets
before tapering or shaping the stock.
Tapered stock requires a spacer to level it
on the platform. I like to plot hinge
locations on the fixed surface (wing,
horizontal stabilizer, and vertical
stabilizer) and transfer those locations
directly to the moving surface (aileron,
elevator, and rudder).
Slot Machine accessory blades are
available in various thicknesses and
widths. I use two sizes of hinges in my
building and have a dedicated machine for
each. Changing blades is a straightforward
procedure, but why bother when Slot
Machines are so inexpensive?
Don’t be afraid to modify the cutting
blades for a better hinge-to-pocket fit.
Grind the blades with a hollow behind
teeth to allow for chip clearance. Take
care to keep the blades flat and carefully
deburr the edges.
I couldn’t resist the opportunity to
show off a unique capability of this
fixture. A photograph shows a perfectly
formed hinge pocket cut in 1/16 sheet balsa.
With scrap material and a few hours of
work you can make a tool that will
consistently cut hinge pockets easier,
quicker, and better than any product on the
market. MA
Derek Moran
[email protected]
Sources:
McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs CA 90670
(562) 692-5911
www.mcmaster.com
Great Planes Model Distributors
Box 9021
Champaign IL 61826
(217) 398-8970
www.greatplanes.com
Edition: Model Aviation - 2006/06
Page Numbers: 33,34,35,36
Edition: Model Aviation - 2006/06
Page Numbers: 33,34,35,36
June 2006 33
by Derek Moran
The Slot Machine Fixture consists of a base unit and the Slot
Machine itself, fitted with three adjustable nylon machine-screw feet.
All the parts and hardware for the fixture, ready for assembly.
There is a complete bill of materials on the plans.
The feet allow you to set the height and angle of the hinge pocket.
The radial marks on the hex-head screws help keep their rotation
synchronized.
The completed base assembly. The mark on the platform is the
centerline of the hinge-pocket cut. This is a fast and easy project!
Slot Machine Fixture
THE GREAT PLANES Slot Machine was one of the first tools I
bought when I returned to modeling several years ago. This little
marvel will cut a beautiful hinge pocket in seconds.
I invented the fixture presented here to enable me to
consistently place hinges in proper alignment. Whether you build
from kits or from scratch, this device will improve the speed and
quality of your hinging task.
The fixture consists of a base unit and adjustable-height legs
installed on the Slot Machine. Construction details, including a
bill of materials, are outlined on the plans. This device is quick
and inexpensive to build; most of you will probably find the
materials in your scrap box and odd-parts collection.
You can use any convenient material for the three base parts;
MDF (Medium Density Fibreboard), plywood, and even real wood
will work fine. If your material varies from the nominal 5/8 inch,
adjust the spacer’s thickness so that the platform’s working
surface is 11/4 inches above the base. I used an old particleboard
shelf for the unit in the photographs.
The melamine coating looks nice, but it’s unnecessary.
Whatever the material, the working surface of the base must be
smooth to allow the feet to slide easily.
There are three geometric relationships to maintain as you
build the base.
1) The base must be flat. The working surface of the platform
must also be flat and parallel to the base.
2) The base fence must be perpendicular to the base.
3) The platform fence must be perpendicular to the base fence.
The slot on the base allows you to use a C-clamp to hold the
stock on the platform. The slot will fit most long-reach clamps
A great tool made even better!
Accurately cut hinge slots in any material with the Great
Planes Slot Machine and this simple-to-build device
with a 2-inch opening and 31/2-inch depth. Be sure to use a
backing block so you don’t mar or crush your workpiece. The 5/8-
inch-diameter hole is convenient for wall storage.
Each standoff has a boss that is turned to an interference fit
with the counterbores of the Slot Machine. The fit must be tight
enough to resist the torque of rotating the feet. A drop of thin
cyanoacrylate glue can lock a standoff that is not quite tight
enough.
I chose nylon machine screws for the adjustable feet so they
would not ruin the base. If you substitute steel or brass, jam nuts
will be necessary to lock adjustments. Jam nuts are rarely needed
with nylon screws because their Class 3A thread form is a tight fit
with the Class 2B standoff thread. I selected 6-32 threads because
the pitch conveniently matches the fractional thickness of balsa
stock. Thus to raise or lower the machine 1/32 inch, you rotate each
screw one full turn.
Precisely aligning the tool is accomplished in four simple, logical
stages. Be aware that there is some interaction between the pitch
and roll axes and the elevation. If you tilt the cutting blades
downward, the entire machine must be raised slightly to maintain
the same center height. By following this procedure you will avoid
most interactions.
You will need balsa for test cuts; a piece of medium-hard (8-12
pounds per cubic foot) measuring 1/4 x 1 x 36 is ideal. Check this
material at several locations along its length with a micrometer or
calipers to make sure the thickness is consistent. It doesn’t matter
what the thickness is as long as it is the same (within a few
thousandths).
Initial alignment is done by eye. Since the test stock is 1/4 inch
thick, we want the centerline of the cutting blades to be 1/8 inch
above the platform. At the same time the cutting blades should be
parallel to the platform when viewed from the front and the side of
the base. Adjust the feet until the blade position looks okay.
It’s time to cut a few pockets. Hold the test stock securely
against the platform fence with your left hand. Hold the Slot
Machine against the base fence with your right hand. Advance the
machine, maintaining contact with the base fence, so that the
cutting blades just touch the balsa. Push the trigger switch with
your thumb and then gently advance as the blades cut the pocket.
Proceed with fine adjustments, starting with alignment in roll.
By roll I mean the side-to-side tilt of the pocket as viewed from
the stock edge.
Cut two pockets approximately 3 inches apart. Partially insert a
hinge in each slot and place a straightedge against the hinge tabs.
Both hinges and the straightedge should be collinear. Raise or
lower the front left foot to make corrections.
Align the pocket in pitch: the dive or climb of the pocket after
34 MODEL AVIATION
The author cut these hinge pockets in 1/16 sheet balsa. He used
Great Planes GPMR4015 blades (.008 thick) and modified them to
cut a 5/8-inch-wide pocket. This setup works well for small nylon
hinges such as Klett RK2 and Du-Bro 119.
If you don’t have access to a lathe, a drill press can turn the bosses
on the standoffs. Mount a left-cutting lathe bit tightly in a vise and
securely clamp the vise to the drill-press table. Tap the table
horizontally to adjust the infeed; advance the stock with the quill
downfeed. Concentricity and finish are noncritical. Make light cuts
and be sure to take safety precautions.
Cutting hinge pockets is easy. Hold the stock against the platform
fence with your left hand; activate the trigger switch and advance
the Slot Machine with your right.
Cutting forces are not high, so you can usually hold the stock with
your hand. The base has provisions for a clamp, for unique situations.
Photos by the author
it enters the stock edge. Cut a new pocket
and then insert a long strip of credit-card
plastic that is the same width as a hinge.
Sight this from the side; any error in pitch
will be magnified by the length of the strip
and can be easily seen. Raise or lower the
rear foot to make corrections.
Center the pocket’s elevation on the
stock edge. Cut a pocket and then flip the
stock top to bottom. Advance the
machine’s cutting blades to the slot and
inspect it closely.
If the pocket is above the blades, raise
the machine half the distance. If the pocket
is below the blades, lower the machine
half the distance. Raise and lower by
turning all three feet an equal amount. The
pocket is centered when the cutting blades
will enter it without rubbing on the top or
bottom surfaces.
Once the machine is aligned, add index
marks to the feet to help keep their
rotation synchronized. Make marks with a
fine-point Sharpie pen, drawing a radial
line that is parallel to the direction of the
cut.
At this point you can adapt to different
standard stock thicknesses by counting
turns of the feet. If the machine is adjusted
for 1/4-inch stock and you want to cut
pockets in 3/8-inch stock, unscrew (raise)
all three feet exactly two turns.
However, don’t blindly rely on this
feature because balsa stock often varies
from its nominal thickness. Always verify
your adjustment by flipping the stock top
to bottom as described in the preceding.
Mark the platform to indicate the
centerline of the cut. Use this mark to
locate the stock when cutting pockets for
your model.
Clamp a piece of stock to the platform,
against the fence, and cut a pocket. With
the stock still clamped to the platform,
place a mark on the fence directly below
the pocket centerline. Remove the stock
and extend the mark along the platform
and spacer using a square. Use the Sharpie
as before.
This fixture will cut hinge pockets in
most common construction situations. Plan
hinge locations early in the building
process and cut pockets while your stock
is easy to work.
Whenever possible, cut hinge pockets
before tapering or shaping the stock.
Tapered stock requires a spacer to level it
on the platform. I like to plot hinge
locations on the fixed surface (wing,
horizontal stabilizer, and vertical
stabilizer) and transfer those locations
directly to the moving surface (aileron,
elevator, and rudder).
Slot Machine accessory blades are
available in various thicknesses and
widths. I use two sizes of hinges in my
building and have a dedicated machine for
each. Changing blades is a straightforward
procedure, but why bother when Slot
Machines are so inexpensive?
Don’t be afraid to modify the cutting
blades for a better hinge-to-pocket fit.
Grind the blades with a hollow behind
teeth to allow for chip clearance. Take
care to keep the blades flat and carefully
deburr the edges.
I couldn’t resist the opportunity to
show off a unique capability of this
fixture. A photograph shows a perfectly
formed hinge pocket cut in 1/16 sheet balsa.
With scrap material and a few hours of
work you can make a tool that will
consistently cut hinge pockets easier,
quicker, and better than any product on the
market. MA
Derek Moran
[email protected]
Sources:
McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs CA 90670
(562) 692-5911
www.mcmaster.com
Great Planes Model Distributors
Box 9021
Champaign IL 61826
(217) 398-8970
www.greatplanes.com
Edition: Model Aviation - 2006/06
Page Numbers: 33,34,35,36
June 2006 33
by Derek Moran
The Slot Machine Fixture consists of a base unit and the Slot
Machine itself, fitted with three adjustable nylon machine-screw feet.
All the parts and hardware for the fixture, ready for assembly.
There is a complete bill of materials on the plans.
The feet allow you to set the height and angle of the hinge pocket.
The radial marks on the hex-head screws help keep their rotation
synchronized.
The completed base assembly. The mark on the platform is the
centerline of the hinge-pocket cut. This is a fast and easy project!
Slot Machine Fixture
THE GREAT PLANES Slot Machine was one of the first tools I
bought when I returned to modeling several years ago. This little
marvel will cut a beautiful hinge pocket in seconds.
I invented the fixture presented here to enable me to
consistently place hinges in proper alignment. Whether you build
from kits or from scratch, this device will improve the speed and
quality of your hinging task.
The fixture consists of a base unit and adjustable-height legs
installed on the Slot Machine. Construction details, including a
bill of materials, are outlined on the plans. This device is quick
and inexpensive to build; most of you will probably find the
materials in your scrap box and odd-parts collection.
You can use any convenient material for the three base parts;
MDF (Medium Density Fibreboard), plywood, and even real wood
will work fine. If your material varies from the nominal 5/8 inch,
adjust the spacer’s thickness so that the platform’s working
surface is 11/4 inches above the base. I used an old particleboard
shelf for the unit in the photographs.
The melamine coating looks nice, but it’s unnecessary.
Whatever the material, the working surface of the base must be
smooth to allow the feet to slide easily.
There are three geometric relationships to maintain as you
build the base.
1) The base must be flat. The working surface of the platform
must also be flat and parallel to the base.
2) The base fence must be perpendicular to the base.
3) The platform fence must be perpendicular to the base fence.
The slot on the base allows you to use a C-clamp to hold the
stock on the platform. The slot will fit most long-reach clamps
A great tool made even better!
Accurately cut hinge slots in any material with the Great
Planes Slot Machine and this simple-to-build device
with a 2-inch opening and 31/2-inch depth. Be sure to use a
backing block so you don’t mar or crush your workpiece. The 5/8-
inch-diameter hole is convenient for wall storage.
Each standoff has a boss that is turned to an interference fit
with the counterbores of the Slot Machine. The fit must be tight
enough to resist the torque of rotating the feet. A drop of thin
cyanoacrylate glue can lock a standoff that is not quite tight
enough.
I chose nylon machine screws for the adjustable feet so they
would not ruin the base. If you substitute steel or brass, jam nuts
will be necessary to lock adjustments. Jam nuts are rarely needed
with nylon screws because their Class 3A thread form is a tight fit
with the Class 2B standoff thread. I selected 6-32 threads because
the pitch conveniently matches the fractional thickness of balsa
stock. Thus to raise or lower the machine 1/32 inch, you rotate each
screw one full turn.
Precisely aligning the tool is accomplished in four simple, logical
stages. Be aware that there is some interaction between the pitch
and roll axes and the elevation. If you tilt the cutting blades
downward, the entire machine must be raised slightly to maintain
the same center height. By following this procedure you will avoid
most interactions.
You will need balsa for test cuts; a piece of medium-hard (8-12
pounds per cubic foot) measuring 1/4 x 1 x 36 is ideal. Check this
material at several locations along its length with a micrometer or
calipers to make sure the thickness is consistent. It doesn’t matter
what the thickness is as long as it is the same (within a few
thousandths).
Initial alignment is done by eye. Since the test stock is 1/4 inch
thick, we want the centerline of the cutting blades to be 1/8 inch
above the platform. At the same time the cutting blades should be
parallel to the platform when viewed from the front and the side of
the base. Adjust the feet until the blade position looks okay.
It’s time to cut a few pockets. Hold the test stock securely
against the platform fence with your left hand. Hold the Slot
Machine against the base fence with your right hand. Advance the
machine, maintaining contact with the base fence, so that the
cutting blades just touch the balsa. Push the trigger switch with
your thumb and then gently advance as the blades cut the pocket.
Proceed with fine adjustments, starting with alignment in roll.
By roll I mean the side-to-side tilt of the pocket as viewed from
the stock edge.
Cut two pockets approximately 3 inches apart. Partially insert a
hinge in each slot and place a straightedge against the hinge tabs.
Both hinges and the straightedge should be collinear. Raise or
lower the front left foot to make corrections.
Align the pocket in pitch: the dive or climb of the pocket after
34 MODEL AVIATION
The author cut these hinge pockets in 1/16 sheet balsa. He used
Great Planes GPMR4015 blades (.008 thick) and modified them to
cut a 5/8-inch-wide pocket. This setup works well for small nylon
hinges such as Klett RK2 and Du-Bro 119.
If you don’t have access to a lathe, a drill press can turn the bosses
on the standoffs. Mount a left-cutting lathe bit tightly in a vise and
securely clamp the vise to the drill-press table. Tap the table
horizontally to adjust the infeed; advance the stock with the quill
downfeed. Concentricity and finish are noncritical. Make light cuts
and be sure to take safety precautions.
Cutting hinge pockets is easy. Hold the stock against the platform
fence with your left hand; activate the trigger switch and advance
the Slot Machine with your right.
Cutting forces are not high, so you can usually hold the stock with
your hand. The base has provisions for a clamp, for unique situations.
Photos by the author
it enters the stock edge. Cut a new pocket
and then insert a long strip of credit-card
plastic that is the same width as a hinge.
Sight this from the side; any error in pitch
will be magnified by the length of the strip
and can be easily seen. Raise or lower the
rear foot to make corrections.
Center the pocket’s elevation on the
stock edge. Cut a pocket and then flip the
stock top to bottom. Advance the
machine’s cutting blades to the slot and
inspect it closely.
If the pocket is above the blades, raise
the machine half the distance. If the pocket
is below the blades, lower the machine
half the distance. Raise and lower by
turning all three feet an equal amount. The
pocket is centered when the cutting blades
will enter it without rubbing on the top or
bottom surfaces.
Once the machine is aligned, add index
marks to the feet to help keep their
rotation synchronized. Make marks with a
fine-point Sharpie pen, drawing a radial
line that is parallel to the direction of the
cut.
At this point you can adapt to different
standard stock thicknesses by counting
turns of the feet. If the machine is adjusted
for 1/4-inch stock and you want to cut
pockets in 3/8-inch stock, unscrew (raise)
all three feet exactly two turns.
However, don’t blindly rely on this
feature because balsa stock often varies
from its nominal thickness. Always verify
your adjustment by flipping the stock top
to bottom as described in the preceding.
Mark the platform to indicate the
centerline of the cut. Use this mark to
locate the stock when cutting pockets for
your model.
Clamp a piece of stock to the platform,
against the fence, and cut a pocket. With
the stock still clamped to the platform,
place a mark on the fence directly below
the pocket centerline. Remove the stock
and extend the mark along the platform
and spacer using a square. Use the Sharpie
as before.
This fixture will cut hinge pockets in
most common construction situations. Plan
hinge locations early in the building
process and cut pockets while your stock
is easy to work.
Whenever possible, cut hinge pockets
before tapering or shaping the stock.
Tapered stock requires a spacer to level it
on the platform. I like to plot hinge
locations on the fixed surface (wing,
horizontal stabilizer, and vertical
stabilizer) and transfer those locations
directly to the moving surface (aileron,
elevator, and rudder).
Slot Machine accessory blades are
available in various thicknesses and
widths. I use two sizes of hinges in my
building and have a dedicated machine for
each. Changing blades is a straightforward
procedure, but why bother when Slot
Machines are so inexpensive?
Don’t be afraid to modify the cutting
blades for a better hinge-to-pocket fit.
Grind the blades with a hollow behind
teeth to allow for chip clearance. Take
care to keep the blades flat and carefully
deburr the edges.
I couldn’t resist the opportunity to
show off a unique capability of this
fixture. A photograph shows a perfectly
formed hinge pocket cut in 1/16 sheet balsa.
With scrap material and a few hours of
work you can make a tool that will
consistently cut hinge pockets easier,
quicker, and better than any product on the
market. MA
Derek Moran
[email protected]
Sources:
McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs CA 90670
(562) 692-5911
www.mcmaster.com
Great Planes Model Distributors
Box 9021
Champaign IL 61826
(217) 398-8970
www.greatplanes.com
Edition: Model Aviation - 2006/06
Page Numbers: 33,34,35,36
June 2006 33
by Derek Moran
The Slot Machine Fixture consists of a base unit and the Slot
Machine itself, fitted with three adjustable nylon machine-screw feet.
All the parts and hardware for the fixture, ready for assembly.
There is a complete bill of materials on the plans.
The feet allow you to set the height and angle of the hinge pocket.
The radial marks on the hex-head screws help keep their rotation
synchronized.
The completed base assembly. The mark on the platform is the
centerline of the hinge-pocket cut. This is a fast and easy project!
Slot Machine Fixture
THE GREAT PLANES Slot Machine was one of the first tools I
bought when I returned to modeling several years ago. This little
marvel will cut a beautiful hinge pocket in seconds.
I invented the fixture presented here to enable me to
consistently place hinges in proper alignment. Whether you build
from kits or from scratch, this device will improve the speed and
quality of your hinging task.
The fixture consists of a base unit and adjustable-height legs
installed on the Slot Machine. Construction details, including a
bill of materials, are outlined on the plans. This device is quick
and inexpensive to build; most of you will probably find the
materials in your scrap box and odd-parts collection.
You can use any convenient material for the three base parts;
MDF (Medium Density Fibreboard), plywood, and even real wood
will work fine. If your material varies from the nominal 5/8 inch,
adjust the spacer’s thickness so that the platform’s working
surface is 11/4 inches above the base. I used an old particleboard
shelf for the unit in the photographs.
The melamine coating looks nice, but it’s unnecessary.
Whatever the material, the working surface of the base must be
smooth to allow the feet to slide easily.
There are three geometric relationships to maintain as you
build the base.
1) The base must be flat. The working surface of the platform
must also be flat and parallel to the base.
2) The base fence must be perpendicular to the base.
3) The platform fence must be perpendicular to the base fence.
The slot on the base allows you to use a C-clamp to hold the
stock on the platform. The slot will fit most long-reach clamps
A great tool made even better!
Accurately cut hinge slots in any material with the Great
Planes Slot Machine and this simple-to-build device
with a 2-inch opening and 31/2-inch depth. Be sure to use a
backing block so you don’t mar or crush your workpiece. The 5/8-
inch-diameter hole is convenient for wall storage.
Each standoff has a boss that is turned to an interference fit
with the counterbores of the Slot Machine. The fit must be tight
enough to resist the torque of rotating the feet. A drop of thin
cyanoacrylate glue can lock a standoff that is not quite tight
enough.
I chose nylon machine screws for the adjustable feet so they
would not ruin the base. If you substitute steel or brass, jam nuts
will be necessary to lock adjustments. Jam nuts are rarely needed
with nylon screws because their Class 3A thread form is a tight fit
with the Class 2B standoff thread. I selected 6-32 threads because
the pitch conveniently matches the fractional thickness of balsa
stock. Thus to raise or lower the machine 1/32 inch, you rotate each
screw one full turn.
Precisely aligning the tool is accomplished in four simple, logical
stages. Be aware that there is some interaction between the pitch
and roll axes and the elevation. If you tilt the cutting blades
downward, the entire machine must be raised slightly to maintain
the same center height. By following this procedure you will avoid
most interactions.
You will need balsa for test cuts; a piece of medium-hard (8-12
pounds per cubic foot) measuring 1/4 x 1 x 36 is ideal. Check this
material at several locations along its length with a micrometer or
calipers to make sure the thickness is consistent. It doesn’t matter
what the thickness is as long as it is the same (within a few
thousandths).
Initial alignment is done by eye. Since the test stock is 1/4 inch
thick, we want the centerline of the cutting blades to be 1/8 inch
above the platform. At the same time the cutting blades should be
parallel to the platform when viewed from the front and the side of
the base. Adjust the feet until the blade position looks okay.
It’s time to cut a few pockets. Hold the test stock securely
against the platform fence with your left hand. Hold the Slot
Machine against the base fence with your right hand. Advance the
machine, maintaining contact with the base fence, so that the
cutting blades just touch the balsa. Push the trigger switch with
your thumb and then gently advance as the blades cut the pocket.
Proceed with fine adjustments, starting with alignment in roll.
By roll I mean the side-to-side tilt of the pocket as viewed from
the stock edge.
Cut two pockets approximately 3 inches apart. Partially insert a
hinge in each slot and place a straightedge against the hinge tabs.
Both hinges and the straightedge should be collinear. Raise or
lower the front left foot to make corrections.
Align the pocket in pitch: the dive or climb of the pocket after
34 MODEL AVIATION
The author cut these hinge pockets in 1/16 sheet balsa. He used
Great Planes GPMR4015 blades (.008 thick) and modified them to
cut a 5/8-inch-wide pocket. This setup works well for small nylon
hinges such as Klett RK2 and Du-Bro 119.
If you don’t have access to a lathe, a drill press can turn the bosses
on the standoffs. Mount a left-cutting lathe bit tightly in a vise and
securely clamp the vise to the drill-press table. Tap the table
horizontally to adjust the infeed; advance the stock with the quill
downfeed. Concentricity and finish are noncritical. Make light cuts
and be sure to take safety precautions.
Cutting hinge pockets is easy. Hold the stock against the platform
fence with your left hand; activate the trigger switch and advance
the Slot Machine with your right.
Cutting forces are not high, so you can usually hold the stock with
your hand. The base has provisions for a clamp, for unique situations.
Photos by the author
it enters the stock edge. Cut a new pocket
and then insert a long strip of credit-card
plastic that is the same width as a hinge.
Sight this from the side; any error in pitch
will be magnified by the length of the strip
and can be easily seen. Raise or lower the
rear foot to make corrections.
Center the pocket’s elevation on the
stock edge. Cut a pocket and then flip the
stock top to bottom. Advance the
machine’s cutting blades to the slot and
inspect it closely.
If the pocket is above the blades, raise
the machine half the distance. If the pocket
is below the blades, lower the machine
half the distance. Raise and lower by
turning all three feet an equal amount. The
pocket is centered when the cutting blades
will enter it without rubbing on the top or
bottom surfaces.
Once the machine is aligned, add index
marks to the feet to help keep their
rotation synchronized. Make marks with a
fine-point Sharpie pen, drawing a radial
line that is parallel to the direction of the
cut.
At this point you can adapt to different
standard stock thicknesses by counting
turns of the feet. If the machine is adjusted
for 1/4-inch stock and you want to cut
pockets in 3/8-inch stock, unscrew (raise)
all three feet exactly two turns.
However, don’t blindly rely on this
feature because balsa stock often varies
from its nominal thickness. Always verify
your adjustment by flipping the stock top
to bottom as described in the preceding.
Mark the platform to indicate the
centerline of the cut. Use this mark to
locate the stock when cutting pockets for
your model.
Clamp a piece of stock to the platform,
against the fence, and cut a pocket. With
the stock still clamped to the platform,
place a mark on the fence directly below
the pocket centerline. Remove the stock
and extend the mark along the platform
and spacer using a square. Use the Sharpie
as before.
This fixture will cut hinge pockets in
most common construction situations. Plan
hinge locations early in the building
process and cut pockets while your stock
is easy to work.
Whenever possible, cut hinge pockets
before tapering or shaping the stock.
Tapered stock requires a spacer to level it
on the platform. I like to plot hinge
locations on the fixed surface (wing,
horizontal stabilizer, and vertical
stabilizer) and transfer those locations
directly to the moving surface (aileron,
elevator, and rudder).
Slot Machine accessory blades are
available in various thicknesses and
widths. I use two sizes of hinges in my
building and have a dedicated machine for
each. Changing blades is a straightforward
procedure, but why bother when Slot
Machines are so inexpensive?
Don’t be afraid to modify the cutting
blades for a better hinge-to-pocket fit.
Grind the blades with a hollow behind
teeth to allow for chip clearance. Take
care to keep the blades flat and carefully
deburr the edges.
I couldn’t resist the opportunity to
show off a unique capability of this
fixture. A photograph shows a perfectly
formed hinge pocket cut in 1/16 sheet balsa.
With scrap material and a few hours of
work you can make a tool that will
consistently cut hinge pockets easier,
quicker, and better than any product on the
market. MA
Derek Moran
[email protected]
Sources:
McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs CA 90670
(562) 692-5911
www.mcmaster.com
Great Planes Model Distributors
Box 9021
Champaign IL 61826
(217) 398-8970
www.greatplanes.com
