I couldn’t get my self to buy $100 calipers, so I asked my grandfather to make me a set.
http://goodfrank.com/index.php/archives/111
Rick.
NICE JOB, GRAMPS!..i’ll buy a set from you (him?)!..uhhhh…i have $15.
:-\
Sorry. These are a one off. Maybe I’ll get motivated some day and make a couple with his help.
Really nice! I just finished my second set of real shit calipers that are useless. I was going to buy some but didn’t know they were $100. Guess I’ll try again. Tell Gramps he has impressed a lot of Swaylock’s craftsmen.
I made my own too. I was similarly resistant to dropping that kind of dough on such a simple tool so I made it out of scrap plywood and hardware. Total cost was about $2 and they work great. Very accurate. The only hard part was the scale. I drew it in Autocad based upon some simple 10th grade geometry, but transposing it to hard plastic was a challenge. What I ended up doing was printing to transparency and then gluing the transparency to a sheet of clear polycarbonate using resin. That worked ok, but the polycarbonate was soo brittle that it was tough to cut a smooth curve. Any idea how your grandfather made his scale?
To make the scale, it’s by far the most accurate to calibrate the calipers once they are complete.
Hold them against a steel ruler, and mark off the graduations perfectly.
Too inaccurate to work out the angles and circular distances before you assemble it!
It does mean you have a hand written scale, but i’m sure you can make it look pretty.
Heres a simple geometry tip - make the handles longer than the pincers, meaning that the distance from the pivot pin to the end of the calipers is shorter than from the pivot pin to the scale.
This will make them vastly more accurate, as a minute movement in the pincers translates into a greater movement on the scale.
Your scale will not be so cramped together.
It does mean that they will be big long things needing two hands to operate, but thats worth it.
I’m guessing the scale on the ones in that picture is actually more cramped than real inches are?
If you do that it means you remove any errors in your building of the calipers.
Bloody nice job he’s done of those ones!
Get him making surfboards! They’ll probably be works of art!
Kit
He drew the scale directly onto the wood after the salipers were built. Just measured the opening and drew lines, etc. Got to 16th of an inch. Def more than I’ll worry about.
I calibrated the scale when mounting it as well. You must do that. The benefit of using the computer to print the scale is that you only have to calibrate it at one place. I calibrate it at around 2" to further increase accuracy, but you really could use any distance. Makes it very easy to get an accurate scale. If you do it by hand you have to calibrate each demarkation. That’s a lot of work and it is subject to the steadiness of your hand.
I agree with you that making the handles longer makes it much easier to get an accurate caliper, especially if you need high precision. I considered it but am pretty sure that I’d never use such a clunky, unwieldy tool. And it’s not necessary to get 1/16" precision on a computer generated scale.
Here’s a couple pics. Not pretty, but pretty accurate.
Man, they look great to me!
I actually barely ever use calipers anymore though, now that i’m using APS 300 and hotwiring EPS.
My blanks come out exact thickness, I just leave enough for one pass of the planer.
If I need to take the thickness down at all, I just count how many passes I make at the depth my planer is set at.
Maybe I should be checking my work for consistency a bit more!
I’ll probably copy your design for my next set, thanks for the info!
Kit
Same here. I’m making my own close tolerance rocker templates from CAD and hotwiring my own blanks so I rarely use the calipers when shaping. I occasionally use them to check thicknesses on existing boards though.