Marko's Workshop: abrasive water jet cutting

Saturday, 23 January 2021

'73 Suzuki GT250 - Part 16 - Stainless steel front brake disc

I had an opportunity to cut a front brake disc for my GT250 out of 5 mm thick stainless steel sheet using abrasive water jet cutting. After googling and looking at different front brake disc designs I decided go with similar style used in aftermarket Triumph Speed Twin front brake discs. Once I was happy with the 3D-model I exported it to a DXF file which was used to program routing for the cutting machine.

After cutting I machined grooves around each bolt hole used to fix the brake disc to the front wheel hub with 14 mm square mill in a vertical milling machine. Once that was done I sand blasted the disc to get a good surface for paint.

This time I decided to use simple spray paint. Before painting I masked outer edges of the disc and cleaned all the surfaces I wanted to paint with acetone. I applied a thin coat first which supposed to help the next heavier coats to stick better. Instructions in the can said to use primer when necessary so I opted to leave it out. I'm curious too see how it works without primer. If it doesn't I will prep it and paint it again. Once paint had cured I installed the disc with a 12 mm spacer I also got cut with abrasive water jet cutter and rolled the bike outside to snap few pictures of it 😊

Design for front brake disc

Dimensions

Blank

Grooves for socket cap screws machined with square end mill
in a vertical milling machine

Sand blasting before...

...masking and coat of matte black spray paint

Dimensions for spacer

I painted the outer surface also with matte black

Sunday, 31 May 2020

'73 Suzuki GT250 - Part 13 - MX footpegs and custom brackets

I had a pair of IMS Pro Series footpegs meant for Kawasaki '99-01 KX125 250 (#293112-4) laying around which I had purchased for a previous project of mine but never ended up using them. After getting rid of that bike I stored them for later use. At one point I had them for sale too but after time went by and I still had them I decided to utilize them in this build.

I designed a pair of brackets to be able to fit them to frame of my GT250K with help of four weldable inserts and M8 bolts. Inserts were turned in lathe out of 18 mm round steel bar and parts of brackets cut out of 6 mm steel sheet using water jet cutter and welded together.

Footpeg assembly

Pair of IMS Pro Series footpegs
for '99-01 Kawasaki KX125/250 (#293112-4)

Pair of pins, 10x49.5 (#92043-1564)
and springs, step (#92144-1951)

Dimension drawing of M8 frame inserts

Inserts were turned in a lathe out of 18 mm steel round bar

Dimension drawing for parts of footpeg brackets

Preview of cut drawing for parts of footpeg brackets

NC-code for water jet cutting

Water jet cutter

Exterior...

...and interior of sand blasting cabinet

Blank after sand blasting

Pieces separated with a hand saw

Since water jet cutter tends to leave chamfers to holes I decided to make them bit smaller and drill them to right size after cutting. I did that in two stages. First time to 8 mm and after mocking up and welding M8 inserts to frame to 9 mm. 8 mm holes allowed me to center inserts perfectly to brackets. They would have been too tight for M8 bolts after painting so I decided to drill them afterwards to 1 mm oversize. I will powder coat both footpegs and brackets later once I have all the other parts such as side stand etc. ready for that as well.