I needed a way of cutting heat shrink tube into repeatable short lengths. It also needed to be safe and not have any exposed blades. the hole is 6mm sq, the largest I could make it without somebody getting their finger in it. It is all 3D printable, The only extras are the guide rods these are K&S stock #508 5/32 music wire that can be purchased at any model shop. A single edge razor blade and 2 light weight springs. WARNING Be very careful inserting the razor blade into the holder. As I have no control over your usage you accept full responsibility for building and using this tool. I had a request for a 50 mm cut capacity, I have added the STL for this. I have not printed it but it should be fine, please let me know if you have any issues with this.Updated 50mm base file due to rod hole being oversizePrint the base and blade holder at .2 layer height with a 30-40% infill. Depending on how well your printer is set up you may need to clear the guide rod holes with a 4mm drill , do not over drill as you need a firm push fit. The end stops need to be printed at 100% as they are a force fit on the guide rods. Likewise the fence is also printed at 100% infill as it needs to be tapped with a 3mm thread. Cut the head off a 3 x 12 mm bolt and glue the fence knob onto the cut end of the bolt A light application of dry Teflon lubricant on the guide rods will help with the smooth operation of the blade holder.