Introduction: Custom Slide Rule DIY

I recently started getting interested in slide rule calculators and I was considering buying one. Meanwhile, using online virtual slide rules to practice, I noticed that I wasn't able to identify the exact model was best suited for my needs. All had some scales I don't need and lacked of some I would find useful.

On the website I found a collection of the individual scales, as image files, that can be downloaded.

So I decided to create my own, with the arrangement of scales I considered optimal to me.

Step 1: Material and Template(with Scales) (or the Opposite?)

As I said I wanted a customized arrangement so I had to prepared my own template.

You can start from the design and then cut the material to the desired size or do the opposite and find a suitable material and then change the size of the print.

I strongly suggest to start finding a suitable bar of plastic/aluminium/wood or similar that can just cut to the desired length since the long edges shall be as straight and parallel as possible. (I strongly regret not following my own advice but the advice originated after the experience). Anyway I first got the material with sizes and then prepared the template.

I had a plate of DIBOND(2 layers of aluminium with a layer of plastic between them and a really nice white paint finish) laying around and I belived it was a good idea to cut it to size. Anyway I cut 3 strips 3cm wide. 2 of them are about 23cm long and the third is about 27cm long. I also cut out a 6cm x 22cm piece to serve as base.

Then I prepared the template using Word. Just insert 3 rectangular shapes, set their dimensions to the desired(it's important they match the width of your strips, the length is not required, A little shorter than the strips it's better) and arrange them one upon the other. Then I insert the images of the scales I desired making sure that the scales C and D face each other on the edge between the middle and lower shape, and the scales A and B face each other on the edge between the higher and middle shape(As you would notice in the download the scale B is actually flipped upside down and is identical to A, so you have to solve the problem somehow).

I share the pdf file of my template in case you are not interested in customizing your own.

Step 2: Print and Cut Out

Check the printer's settings are set for scale=100% or whatever percentage you need to match the width of your strips - for example for 1 inch strips(2.54cm) you can set the printer to 2.54/3=> 85%

Print the template.

Cut out the template as shown in the image, leaving the 3 sections together, they will be divided later.

Step 3: Place the Slider

Aligh the longer strip(will be the slider) in the middle of the base. Use electrical or office tape to keep it in place.

Step 4: Attach Double-sided Tape

Attach Double-sided tape on the exposed areas of the support.

Trim the tape exceeding.

Then peel off the protective layer .

Step 5: Attach the Stators

Place the short strips, one at a time. being careful they are centered on the base and, most impostant, they are touching the central strip.

While repeating the process with the second strip try to get the ends aligned.

Then give a good press to the strip on the adhesive tape to secure them in place.

Step 6: Adhesive

Move the slider in the desired initial position. I decided to have the slider centered and protruding on both ends to be easily handled in both directions.( Another reasonable option could be have one end aligned with the stator's edge such that the tool can be reset easily to the initial position)

Put the template on the 3 strips and mark with a pencil the area that the template will cover.

Then cover the marked area with double-sided tape. Use paper strips(leftover of the cut out) to prevent the tape from contaminating with adhesive the areas that will not be covered.

Trim the excess of adhesive tape and then peel off the protection layer.
My advice is to peel just one (the top one) at first and later peel the others, but you will better understand in the next step.

Step 7: Attach the Template

Now the template must be carefully attached to the body of the slider rule.

The most important thing you have to care about is that the lines dividing the template in 3 parts are exactly aligned with the boundaries between the strips.

My advice is to perform the alignement with the protection layer still in place except the first, so you can freely adjust the alignement without adhesive right underneath, but once the alignement is achieved you can explot the adhesive on the top edge to hold it.

Then peel the other protection layers and stick the template avoiding imperfections. and finish with a good press.

Advice: now would be the right time to cover the template with clear-tape(or other self-adhesive and transparent film) for protection against wear and stains.

Step 8: It's Time to "unchain" the Slider

Use a cutter or an exacto knife to cut the template along the groove between the slider and the stator

Step 9: The Cursor and Hairline 1

Get a rectangular piece of transparent plastic. Mine was 6 cm wide and 11 cm high.

Note that the cursor width should not exceed the double of the distance between the end of the scales and the end of the stator.(For example I have at least about 3.5 cm on each side of the stator and the cursor is 6 cm)

Trace a thin line along the height in the middle. I used the needle point of a compass to engrave a thin line.

Step 10: The Hairline 2

I used a couple of small pieces of the same material as the body(dibond of the same thickness) and sticked them under the clear plastic (the face with the engraved line is facing the scales to avoid parallax) while checking the alignement of the hairline with the scales(keep the line on the 1s of the scales of the stator: A(labeled x^2), K (labeled x^3), and D (labeled X). At the same time these small pieces must achieve a tight fit on the top and bottom stators.

Step 11: The Hairline 3

I used a couple of eurocents glued to the bottom of the shims to keep the hairline in place.

Step 12: Ready to Use (and Possible Improvements)

Now the slide rule is ready to calculate, and you?

Possible improvements:
Maybe in the future I will build a new one with 2 different sets of scales, one for the front and one for the back and mount it on a transparent support (or between 2 transparent supports) and devise a double sided hairline(the tricky part is the alignement of the front and back lines)

I also noticed that the scales lack of the standardized labels (A,B,C,D, DI, K, LL1, LL2 etc etc) and the markings for some important values that are usually maked on good slide rules ( such as pi, e,the way etc)

I WOULD BE HAPPY TO RECEIVE YOUR SUGGESTIONS IN THE COMMENTS about the scales I should put on the back of the future improved model, or any similar advice.