Tubular Key (Customizable to any code)

About

This is a model of a "standard" 7.8mm (technically 7.92mm) tubular key. The default settings are 7 pin and the key code order is set to Chicago Ace.

Print instructions

Customizing

Use the .scad file to customize. The .stl file is an example export of the key code 1234567.

Key Code

Set the key_code array to the bitting you want to duplicate. If you are looking at the key with the end pointed towards you, the code is read starting at the top moving counterclockwise.

If you have a code from a Fort Lock Gem key, you will need to reverse the order of the code.

If you are duplicating a key with a different number of cuts, you can shorten or lengthen the key_code array. Note that the first cut is cut_shift degrees counterclockwise from the top. If you want a cut at the top of the key, you can rearrange the code so that cut is the last one.

0 Cuts

Entering a key code of 0 causes no cut to be made in that spot. This is useful for key codes of 0 and also when making keys with nonstandard spacing.

For example, setting the spacing / making the first cut 22.5 degrees from the 12-o-clock position, then using a "0 cut" as every other number spaces the remaining cuts 45 degrees apart resulting in the top of the key sitting between 2 cuts instead of lining up with one.

Cut Shift

You can use this model to produce keys with various cut arrangements. Simply adjust the cut_shift to the spacing in degrees between each cut. The default for a 7 pin lock is 45 degrees. This means that the model will start 45 degrees counterclockwise from 12-o-clock before making the first cut, then advance 45 degrees before each subsequent cut.

For an 8 pin lock that is evenly spaced, you would use 22.5 since the first cut is 22.5 degrees counterclockwise from the top. You would need to also put in 16 numbers instead of 8, with every second cut being 0 as mentioned above.

Offset Spacing

7 pin left offset and right offset can be achieved combining the above settings, as well as 8 pin split center.

7 Pin Left Offset

• Set cut_shift = 22.5
  • Insert extra 0s for spacing: key_code = [0,0,3,0,4,0,5,0,4,0,3,0,4,0,5]

7 Pin Right Offset

• Set cut_shift = 22.5
  • Insert extra 0s for spacing: key_code = [3,0,4,0,5,0,4,0,3,0,4,0,5]

8 Pin Split Center

• Set cut_shift = 22.5
  • Insert extra 0s for spacing: key_code = [1,0,2,0,3,0,4,0,5,0,6,0,7,0,8]

Tube Diameter

You can adjust the diameter of the key to fit smaller or larger tubular locks. Use tube_ID and tube_OD to adjust the inner and outer diameter.

Oversize

• 10.16mm OD
  • 8.38mm ID

Standard

• 9.53mm OD
  • 7.92mm ID

Small

• 9.27mm OD
  • 7.62mm ID

Printing and Testing

FDM printing with the end of the key facing up seems to give the best results. Your printer will need to have good z resolution for the key to work.

Cut Radius

If your printer has poor tolerance, you may find that the cuts are not big enough to ensure the pins fall in the cuts. If you suspect the pins are catching on the edge, you can try increasing the cut_radius. I have had success with 2mm, but 3mm will give more clearance.

Web Thickness

If you print on an SLA printer, the "web" or wall between the key cut and the inner wall of the tube may interfere with the pins of the lock due to resin in the corner of the cut solidifying. It may help to change the web_thickness to a lower value, or to even switch it to 0 or negative to cut through the wall completely to avoid unwanted interference. (All of my FDM prints were not able to print the wall anyways, so it should be fine to omit it. Though it does feel and look nicer when the inner rim of the key is continuous.)

Results

FDM

Printing on an FDM printer (0.4 nozzle) with all standard settings resulted in a print that was missing the "web" in between the cut and inner surface of the tube, presumably due to the lateral resolution of the printer. Despite this, the key performed perfectly fine. The FDM prints tended to be a little tight, so it's important to scrape off any unwanted material and to gently insert and remove the key several times to loosen it up.

SLA

The jury is still out on whether I am able to successfully print on an SLA printer. The key seems more accurate in dimensions from the SLA printer (the key is looser when inserting into the lock like a metal key), but I think difficulty on the sharp interior corners of the cuts keep it from working.

FusionJet

I also tried one in nylon a fusionjet nylon printer, that produced some of the best results due to fusionjet's high accuracy - so the key operated very smoothly

Ebay Locksmiths

For a long term replacement, consider giving the code to an eBay locksmith who can cheaply cut a key to code out of brass or steel. While 3D printing works best if you need to check the bitting (to avoid back and forth between a locksmith) or make a replacement in a pinch (if you need it within hours), having a metal key obviously still wins out on durability.