I bought the six vertex frame parts of 2020 Aluminium extrusion for $32 from a seller on the net. The 2020 Aluminium extrusion I bought for 10,000 KRW ($10) has 20.25 mm in size which is little bigger than the specification. It made me do extra work to file down the square holes.
When you insert the aluminium extrusion into the hole of vertex frame, make sure it’s straight before hitting it hard with a hammer. If it stops going in, take it off and file the hole of vertex frame down. Repeat this process until the extrusion comes across the vertex frame.
Vernier caliper: 0.05 mm unit
Hammer: small, medium size
Small square file: width is less than 8 mm
Flat and round square file
Long blot – M6x150
Precision engineering square
Scrap square wooden pieces
T3P3 Kossel Mini Kit
Chapter 1 – Printed Parts Preparation http://www.think3dprint3d.com/