Bending toolrests
#4
  Re: (...)
Ruler2112's post in this thread prompted me to action.

As you can see in the following picture, I bent this particular bowl-rest whilst turning a bowl (note: the rest is turned 90 degrees counterclockwise). It's actually bent in two planes, only one of which you can clearly see in the picture - the other is a rotational-bend.




I think this is soft steel and I can probably take out the bends, but is there someway I can strengthen the steel to resist re-bending? Is this a candidate for tempering? Or I could bend-, harden- and weld drill rod to the top edge as a stiffener.

Naturally the practical thing to do is get a better quality rest, but where's the fun in that?

-Mark
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#5
  Re: Bending toolrests by MKepke (Ruler2112's post in ...)
Well, I am not sure. From the picture, it looks slightly torqued and bent down at the tip like the McNaughton blades get after lots of use. So, How thick is the rest arm, and how long. 1/4 inch stock should hold for a not very long rest, say 6 inch or so. If it is under 1/4 inch thick hot rolled, then not suitable for the heavy use I would put one through. You could probably twist it back by clamping the end/tip in a vice, and putting a cheater bar on the post.

robo hippy
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#6
  Re: Bending toolrests by MKepke (Ruler2112's post in ...)
MKepke said:

I think this is soft steel and I can probably take out the bends, but is there someway I can strengthen the steel to resist re-bending? Is this a candidate for tempering? Or I could bend-, harden- and weld drill rod to the top edge as a stiffener.

Naturally the practical thing to do is get a better quality rest, but where's the fun in that?




I don't know what kind of steel your rest is made out of, but if it is mild (low carbon) steel, it will not harden.

Background: Hardening is the process of heating it above a certain temperature, slightly different for each type of steel but usually around 1550, and then quenching it in a some type of cooling medium, anywhere from air to oil to water to brine. Hardening transforms the steel's internal structure to do just that - make the steel harder. However, the harder it is, the more brittle it is and a tool rest will likely break on the first impact if some of the hardness is not drawn out. Tempering is heating a hardened piece of steel to a lower temperature, again different for each type of steel but usually around 300-400 degrees, and allowing it to cool. This again transforms the internal structure to relieve stresses and make it tougher.

It *might* be possible to harden & temper the rest, but you'd have to know how to 'spark test' the rest to find out about how much carbon is in it. (Carbon is the element that allows steel to harden.) It's not something one can really talk somebody through - you have to see it to be able to judge; I've done it many, many times and still am not good at it.



Best route to go is probably close to what you mentioned - adding mass. The more steel you have, even soft, the harder it will be to bend.

When you weld something, it gets above the temperature needed to harden and allowing it to slow-cool will remove the hardness from it. However, since the weld is localized, different areas will have different hardnesses and the stress on the hardened top will be tremendous. I'd guess that the hardened drill rod will crack. (At the very least, it'll no longer be hard after welding.) If you know how to braze, that is a low enough temperature operation that it will not damage the hardened material. (Whenever I have to join two pieces of metal after heat treat, I always have them brazed rather than welded.) The possibility exists of heat treating the rest after welding the hardenable steel to it, but I probably wouldn't try this; the different steels will react differently to heat treatment and you might end up with two (or more) pieces of steel again.

I'd suggest finding one or more pieces of steel the same height as the bent part, bend them to the same profile as your rest and then weld them to the rest after straightening it. You'll have to grind/sand/file the top to make it smooth, but it'll certainly be more difficult to bend if you double or triple the thickness of the crossbar.


Either that or just get some solid steel rod from HD and make a couple new ones. The round rests are awesome.

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