Sedgwick MB rise and fall damage

[jetsetwilly]

This would be easy to identify as the threaded portion will be larger than the smooth portion of the shaft as the metal deforms during the rolling process it becomes larger.

You must remember that Sedgwick is a very small artisanal manufacturer of woodworking machinery, there are no special processes or expensive machinery involved in the production of these machines, in fact it's very archaic and they almost always go for the cheapest possible way of manufacture whilst keeping the quality somewhat acceptable. I can say without a doubt that they cut all their in-house threads with dies or single-point cut in the lathe, because when you examine their threads you will often see the burr left behind by the dies or the steps in the thread at the end where they've pulled the cross-slide back and the tolerances vary massively from machine to machine, particularly spindle moulder shafts where one nut will thread on very loosely and another will be so tight to thread on that you need a spanner just to wind it on.

Hmm, interesting, thanks - I'll get a better look at the lifting bar when I get it out, but I expect even a small manufacturer might use rolled threads in something like this as it's potentially just a length of standard stock. I don't know a lot about Sedgwick, this is the first of theirs that I've had my hands on, but I like the simplicity, and I've always thought their castings look lovely.

 

[J-G]

@J-G it's probably rolled as you said which does harden it - point was just that it's a lot harder than the cast iron lifting foot

Thread Rolling doesn't 'Harden' the steel in any way. It does make a stronger thread (compared to a 'cut' thread) - not harder as in an increase in the Rockwell, Brinell (etc.) number - as long as it is done properly, such that the 'crest' does not have a cavity which can be due to the blank bar being marginally too small.

'Cast Iron' is a blanket term with variants having a Brinell Hardness range of 130 to 450 - non heat treated Mild steel has a Brinell range of 95 - 126 and I cannot envisage any 'manipulation' of a mild steel bar - other than specific heat treatment - making a mild steel bar harder than Cast Iron. By 'Harder' I mean in the accepted metallurgical sence.