« TechNotes

Pin Registration

I find trying to line up negatives on top of a gum or platinum image over a light box is usually difficult and seldom accurate. I know some people advocate using pins to push holes through the paper and negatives to aid alignment, but that won't work for papers mounted on aluminum. I've settled on a cheap and easy to use system that will also work with aluminum. The whole construction process takes a few hours in the shop.

This system requires a few tools for assembly, but nothing out of the ordinary. This is for anyone handy in the shop (or for any photographers who know someone with a shop, do a trade...)

The materials used:

A few scraps of plywood
A 1/8" diameter zinc-plated round steel rod (a few dollars at the local home-improvement store)
Four 1/8" Drill Bushings ($2.80 each) - Lee Valley 25K62.02 (http://www.leevalley.com)
Four inserts for the bushings ($2.80 each) - Lee Valley 25K62.20
A length of 1/4-20 x 24" Rod ($2.00) - Lee Valley 05F01.04
A pack of 3-Prong T-Nuts ($1.00) - Lee Valley 00N22.03
Two 1-1/2" Four-Arm Knob, Female ($2.80 each) - Lee Valley 00M55.30

Optional items, if you have a light box that magnets will stick to:

A pack of 3/4" rare-earth magnets ($8.60) Lee Valley 99K32.11
Two steel cups for the magnets ($1.40 each) Lee Valley 99K32.54

I listed the Lee Valley references only because that's what I used. They're a great resource, but you can probably find the parts elsewhere.

The build:

First build the clamping bar that will hold things in place while puching holes. Glue together a strip of 3/4 inch ply and one of 1/2 inch ply, about 2" x 18" (baltic birch is nice but probably not necessary).  After gluing, clean up the sides and glue on another piece of 1/4 inch ply about 1"x18".

Next build the base. Glue up a 1" x 18" strip of 1/4 inch ply to a piece of 12" x 18" 1/2 inch ply. You should end up with something that looks like this:
ply sandwich

To finish the clamp, set the clamping bar down on the base, hold the bar and the base together and drill a 1/4 inch hole all the way through at each end. Remove the clamping bar and mount the T-nuts to the bottom of the base like this:
ply sandwich

The T-nuts will hold 3 inch lengths of threaded rod. Cut the two pieces of rod, clean up the ends, and screw and glue them into the T-nuts with some epoxy. Here's the assembled base and clamping bar holding a sheet of paper:
assembled

Now the registration guides: With a drill press, drill two 5/8 inch holes through the clamping bar, centered 10 inches apart, 1/2 inch from the front edge of the bar. Assemble the bushings and inserts, and hammer one set all the way in from the bottom side of the clamping bar, and hammer the other set as far as they will go into the top of the clamping bar.

Add the registration pins: Clamp the bar to the edge of a strip of 3/4 inch plywood, about 16 inches long and as high as the top of your light box. Using the bushings, drill into the 3/4 inch ply to allow the pins to be set. Cut the pins from the 1/8 inch rod, chuck the pins into a drill and round the ends on course sandpaper or preferably a mill bastard file (this will make it easier to push your paper or negatives onto the pins). Then just push the pins into the 3/4 inch plywood. Here's the assembly with the pins mounted on the side of the light box:
pins

I added magnets to make it easier to attach to the lightbox, you could just use tape:
magnets

Using the system:

Push a sheet of paper (or paper mounted on aluminum) under the clamping bar, tighten down the bar, and drill through with a hand-held drill using a 1/8 inch drill bit. Do the same with strips of plastic (cutoffs of Pictorico work great).

Set the negatives on the light box, put a piece of pre-drilled plastic on the pins, and use magic tape to attach to the negatives. Or line up the negatives on the light box and carefully place under the clamping bar and drill directly through the negatives. When you're ready to print, set the paper on the pins, set the neg on top of the paper and tape them together on one edge (blue painters tape works well). A small spatula helps to pop the paper and neg off the pins.

I find this works well with unmounted Rives BFK, just drilling through the paper, and with papers mounted on aluminum. With aluminum, you may want to sand down the holes on the back side after drilling to clean up any sharp edges.

Change the dimensions or number of pins to work with your print sizes, it's a flexible system.