After a number of months out of the shed I finally made a brief start on my weld table project (I will try and run a thread in the projects section). After stripping off the horrible blue paint I quickly came across my first issue. I had designed it such that the table height can be adjusted via a 65mm SHS sliding inside a 75mm SHS. Either due to poor calculations or manufacturing tolerances they do not fit. From memory I had a 75mm x 4mm SHS outer and 65mm x 2mm inner so there should not have been an issue (and it is not just the weld seam causing the interference). i will remeasure the tubes but rather than buy another size I want to try to broach out the 75x4 tube slightly larger. I only need to take around 1mm or less out side to side. Each of 6 SHS are 600mm long.

Having previously watched the Fireball Tool method of removing weld seams I was thinking about something similar to broach out my tube. What are your thoughts on a broach similar to this;

SHS Broach.jpg

The dimensions are not yet firmed up other than the first and last cutter being 1mm difference in width in order to cut out the required metal. Due to the tube length I would propose sizeable gaps in the cutter to capture the swarf without binding. Due to the surface area being cut I would expect it would require multiple cutting edges such that each only takes a small amount. Material wise I am not sure and am open to suggestions. I have plenty of 4140 that I could try to harden and temper. I could try to get fancy and attach tool steel to a mild steel core (sounds complex). It could all be cut on the mill.

I would most likely pull this through the material using maybe M20 all-thread. My press is of the small chinesium 12T type and might not be suitable.

Am I off with the pixies on this one or do you think this is feasible? Maybe I am over-complicating my life for the sake of buying alternate SHS. To harden anything I would need to make a heat treat oven although that is a planned project anyway.

Thoughts?
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