The steps for making a
string Bahtinov mask are as follows.
- 1. Gather the materials
- 2. layout the lines on the mask
- 3. prepare the string supports
- 4. Cut out the center of the mask
- 5. mount the string supports
- 6. String the mask.
It's a great project on a rainy day after
the honey-do list is completed.
Here are the details:
For the material I used 1/4" plywood , 1/2x1/2 x1/16 aluminum angle
(you can also use 1/2 flat stock), a spool of thin twine ( you
can use fishing line if you want), 4 - 6/32 machine screws
and nuts to bolt the supports to the plywood. (You can
click on the drawing at the right to get a larger image)
Draw a line representing the Diameter of the 9" circle
from top to bottom. This will be the location of the long support
for the strings.
Draw a line representing the radius of the right side to
the center. This will be the location for the short string support.
Now I laid out the holes. I wanted the strings to
be 1/4" apart.
Using the center point of the circle I measured 1/8th of an inch
on either side to get my starting point for the support holes.
Next I drew lines 1/4" apart on the side of
the circle which doesn't have the Radius drawn. Each of these lines
will be parallel with each other and intersect the Diameter line at
Draw the angular lines at 25.5° to
the Short Radius support line. The angle isn't critical but if you
make it too wide the legs of the X in the image of the mask will be
too far apart and make it difficult to judge when the center line is
in the middle. These line must also be parallel to each other
and 1/4 apart.
Use an appropriate size drill bit
for the string you are using and drill holes where these lines
intersect the middle circle.
To make the aluminum supports I
cut a piece of aluminum angle to 9" to match the
diameter and one to 4 1/5" for the radius at the right.
The tricky part is making
the center diameter support since you want an ear on each end
to use as mounting points for the bar to the plywood. (see Picture
- I started out cutting a 12" square of 1/4
plywood and marked the center. Using a compass, I drew a 8" diameter
circle ( the diameter of my scope's objective). I drew another that
was 9" in diameter. This is where I drilled the holes for the
string. and a third circle 10.5" in diameter. outside edge of the
Cut a piece 9" long and one 5" long
a. If you used Flat stock
I. Make four 1/2 "wide " L "
to be used to mount the support bars to the mask
II. Take the 5" piece and bend a 1/2" 90°
"L" on one end.
allow you to bolt the short to the middle of the
b. If you used angle stock:
I. On the 9" piece mark 1/2 in from
each end and cut down till you
other leg of the angle
II. Starting at the saw cut on one
end remove the remaining material
to the saw
cut at the other end. You want to end up with a flat
bar and an
ear on each end for mounting.
III. Do the same same with the 5"
piece except that you only need one ear on the
IV. Measure in 1/2" from the side of the %"
piece that is flat and bend it 90°.
allow you to bolt it to the long support.
Drill holes in each of the
mounting ears to match the screws you have .
Lay the long support on the
mask and mark and drill mounting holes in the mask.
Do the same with the short
support , laying it on the Radius line and mark and drill a mounting
hole in the mask and mark the position of the hole in the ear on the
Find the center of the long
support and measure 1/8" on each side. This is your starting
point to mark and drill the thread support holes. I marked each
location and the center punched it so the drill would not wander
Fasten the short support bar to
the long bar at so that the bar is over the radius line.
Temporarily fasten the
supports to the mask making sure that the holes drilled
in the long support line up with the lines on the mask.
The short support should overlay the radius line.
Mark where the angular lines meet
the short support bar. Center punch and drill this also.
Now cut out the center of the mask
and the excess off the outside using the outside circle as a guide.
At this point you can string
the mask. I started at the left side on the top and brought the
string up from the bottom. Came across to the first hole
in the long support bar and through the top hole on the right
side. Then came back up thru the second hole on the right , thru the
support and to the second hole on the left. I proceed like this all
the way thru the left side.
Looking at the drawing you will
note that there are line on the left side that do not go
across the mask but go from the top of the left side to the
bottom half of the same side. These strings were laces separately.
This is the procedure I used for lacing
the mask. Use what ever method you find best. The key thing
is that the strings on the left MUST be 90° to
the long support bar and the strings on the bottom right MUST
intersect the short bar at the same angle as the ones on the top.
This is an example of
the image thru the mask
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