Concept Ideas using SketchUp #7: How to make a vernier scale with SketchUp to use on jigs

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Blog entry by George_SA posted 01-23-2018 07:36 PM 1936 reads 1 time favorited 1 comment Add to Favorites Watch
« Part 6: How to draw printable index wheels Part 7 of Concept Ideas using SketchUp series no next part

I am busy with a wooden toy Dump Truck. The jig that I’m planning for cutting the treads in the wheels requires a measurement scale. The first jig that I designed in SketchUp makes use of a digital vernier attached to the jig.

However, I found with my Digital Height Gauge that going digital is a great idea in theory. In practice however digital is quite fiddly. The main problem is that the adjustment mechanism doesn’t match the readout precision. It is like trying to adjust increments of a mm using a 4lb hammer.

That took me back to the drawing board. I decided to try using a printable scale on the jig that works the same as my traditional vernier. (Details of the jig will be in my Wheels blog of the A Dump Truck Adventure blog series. I still need to build the jig and will do so when I start with the wheels. )

I decided however to share what I learned in making a custom printable vernier scale. Maybe it can be of use to someone who wants to use this route. I’m thinking of making another Height Adjustment jig using printed Vernier Scales.

I decided to use SketchUp because
i) it is a free 3D drawing program
ii) I don’t have any other 3D drawing programs and I know how to use it.
iii) It is also quite popular with woodworkers.

(I am not an expert, but I can help myself).

I’m sure the same principals of drawing a Vernier Scale can be used in other CAD programs.

With this blog I assume that you have a working knowledge of using SketchUp. If you are still new with SketchUp or want to give it try, just inquire from Prof Google and his assistant YouTube. There are some excellent tutorials out there. Just use “How to use Sketchup for woodworkers” or something similar as a search phrase.

First thing I had to do was to find out how the scales on a vernier differ from normal ruler scales.
On studying my vernier I found the following:

The primary fixed scale on the vernier is the same as any ruler. 1 mm represents 1 mm.
The secondary movable scale however is where the magic happens. There are 10 major increments (ignore the finer 0,02mm increments) That means that each numbered line on this scale represents 0,1 mm
The first zero increment matches the zero mark on the primary fixed scale and the tenth 0,1 mm increment matches the 49 mm mark on the primary fixed scale. Therefore each 0,1 mm on the secondary movable scale = 4,9 mm on the primary fixed scale.

How does this work? I attempted an explanation with the following pic. There are also excellent tutorials available on the world wide web. Just ask Prof Goggle or his YouTube assistant “How to use a vernier” or something similar. This explanation explains how the metric scales work. Unfortunately I have no idea how the imperial scales work. I see a 1/1000 inch on the top scale, but I haven’t the foggiest how that works. Sorry.

With the knowledge that one 0,1 mm increment on the secondary movable scale = 4,9 mm on the primary fixed scale we can now proceed to SketchUp to draw the scale.

Drawing the secondary movable scale
1) using the “Rectangle drawing tool”, draw a rectangle to work on. For my purposes I used a 16mm x 55mm rectangle (This is determined by the size of the scale that you want to use on your jig.)

2) using the “Tape Measure drawing tool”, draw 10 guidelines spaced 4,9 mm apart on the rectangle (offset the 1st line a bit)

3) Using the “Line drawing tool”, draw 10 lines using the guides from step 2 as reference (I drew the lines 5mm long for the size of my scale), each line representing 0,1mm on the scale.

4) using the “3D Text tool” place the number markers underneath each line increment.

5) Use the same method to draw the fixed primary scale. Line increments are now 1mm apart. Draw the first 10 lines representing 1 cm and the using the “Move, Copy tool” copy and place the other 9 cm on the scale. The primary scale needs to be at least 10 cm long. Just like on a ruler, the number lines are the longest and the un-numbred lines in between are the shortest. The 5 mm increments are halfway in between in length.

The finished scales look like this

6) Follow steps 10 to 12 on my How to draw printable index wheels blog to print the scale 1 on 1. If your printer is accurate the you should get a accurate scale

If you don’t want to go to the trouble of drawing the scales, my SketchUp vernier scale plan is available in the SketchUp 3D warehouse.

Thanks for watching

-- Sometimes life gets in the way of one's woodworking :)

1 comment so far

View Ted78's profile


408 posts in 2810 days

#1 posted 01-23-2018 09:00 PM

I appreciate this explanation. I learned how to read one in shop class years ago and can read one, but never rally understood why it worked.

-- Ted

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