Today, we 3d print a marking gauge.
The combination square is one of the most
used items in my shop.
I mainly use it to measure and to mark a distance
from the edge.
Over time we accumulated quite a few of these
combination squares in the shop.
However I am using them as a kind of story
stick.
That means I have one of them set to the distance
of a mark from the edge, the other to the
depth and so on.
When you try to keep the important measures
of a project all locked in place you are quickly
running out of combination squares.
While combination square are quite expensive
these stainless steel rulers retail at 4 Euro
for a pack of three - shipping included.
Wouldn't it be great to have a making gauge
or combination square replacement for less
than 2 bucks?
The final result has a small lever to securely
lock the position with one hand.
You can use it for measuring as well as for
marking.
Creating such a tool is super easy - at least
in theory.
You just need a steel ruler, a nail and a
3d printer.
First you have to measure the diameter of
the nail, the width of the ruler and the thickness
of the ruler - all these dimensions should
be measured quite precisely.
Then go to my Thingiverse website, type the
numbers in the customizer and download a customized
STL file for free.
Send it to the printer and in an hour or so
you have everything you need.
Insert the steel ruler in the slot and make
sure it slides freely.
Use a thin needle to align the holes in the
sides with the hole in the lever.
Then clip a nail to the width of the marking
gauge and press fit it into the hole.
After it touches the lever you can drive it
down with a hammer and the marking gauge is
ready.
That's the theory but in practice it took
me 9 tries in order to get the prototype right.
Let me share my mistakes so you don't have
to repeat them.
Let's take a quick look at the design to understand
why it is so tricky to get it right.
I wanted to have an eccentric lever rather
than a screw so that it would be easy to lock
the position with one hand.
In the side view you can see very well how
moving the lever is holding the ruler in place
by friction.
But this animation also gives you an indication
how little margin of error we have in this
construction.
The first parameter is the with of the ruler.
This parameter is critical.
When the slot is too wide the ruler will not
be perpendicular to the workpiece.
I found that adding 0.3 mm to the width results
in a very snug fit on my CR-10.
Even with these settings I had to press really
hard or secure the ruler in a vice and give
the print a few taps with a screw driver handle.
Pro tip: If you break the screw driver handle
by pounding on the print the fit might be
a bit too snug.
For the thickness of the ruler I add the same
amount of play and increase it from 0.6 to
0.9 mm.
If there is too little play the ruler will
catch layers from the print in the opening
and damage the print.
The last parameter is the diameter of the
nail where I only added 0.15 mm allowance.
If the print needs superglue in order to hold
the nail in place the tolerances for the lever
are most likely not going to work out.
So we can also directly aim for a press fit.
If you stick the nail through the hole make
sure that if slides through the side part
without problems before tapping it with a
hammer.
Without support the side part is going to
break if you hit it with a hammer.
If you take all this into account you get
print that slides easyly across the ruler
and is securely locked in place once the lever
is pushed down.
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and have a look at other videos about using
the 3d printer in the woodworking shop.
