DN NA Class

I am looking for some pointers on straightening hardened Stainless. We made about 24 runners of various types, lengths, ect. The material is 420HC, they are hardened and tempered to RC56. The heat treating was done in a vacuum furnace.

Some of the runners have a bit of a bow in them, I would like to hear how people work at straightening. If using a hammer, which side to you hit, convex or concave?

I can deflect them straight, is there any chance i can shim my angle shaped  stiffeners to make them straight, or would the temperature changes make the bow too variable?

  I'm pretty sure you hammer on the concave side but I've never had much luck with it because I probably was too timid with the hammer. What I do works well for me but takes a little practice. What I do is to locate the center of the bend and mark it. I then place the blade on 2 pieces of 4X4 spaced at least 1 foot apart. Next a I place a stack of spacers centered under the blade that are a little lower then the 4X4's. Now comes the fun part, I place either a bottle hydralic jack or a scissor jack over the center of the bend. I run a 4X4 post up to a floor joist in my basement and jack the whole mess down to the spacers. Remove the jack assembly and check for straightness. If it isn't straight yet, remove a spacer and jack it down again. Continue doing this till it's straight. You don't want to over straighten it or you`'ll have to go back the other way. I typically make the spacers 1/4"-3/8" thick. Once you get the hang of it, it goes pretty quick. 
   I typically use a bottle jack. To keep it from kicking out when under a load, I drill a hole in the bottom of the post for the jack to fit into. You don't have to get the steel perfectly straight, just as close as you can.The runner bodies will straighten them a little plus when you sharpen them you can fine tune the blade. I'm sure others use other methods, this is mine and I hope it helps.   Bob

Thanks Bob, that helps me a lot. I had tried bowing them in a vice with no luck. I,ll give this a try.

Surprisingly, the only runners that have much bow are the short 26"  and those will be steering runners. I have 30", 36", and 42 as well, they seem straight enough to take care of in the stiffeners and with the edge grind. My 26" runners are off about 1/16"
 

Bob: does that technique work with hardened steel? 
I'd be afraid RC56 stainless would be too brittle to take that kind of bending.

  I've done it on 300 series stainless and on 440C hardened to RC54 with no adverse effects.

I think you need to be careful in your setup.
I was straightening a 440c ss 1/4 using the side  of a sledge  hammer as anvil and it was working well using a ball peen hammer concave side up I had it close and decide to give it one more sharp hit and broke it in half. $200.00 mistake, had it welded back together.

I believe Ron Sherry uses a piece of I beam and some soft  non slip fabric material  you use to line shelves with. Home depot product
Might want to contact Ron as he probably has most experience .
 Good luck

Any thoughts on just shimming them straight? I am making 1-1/2 x 1-1/2 f/g&carbon angle stiffeners. I'm sure I can shim them straight, but I'm not sure what happens when it gets cold.

For steering runners is it that critical?

The only thing more important than straight is parallel. My first home made inserts are a bit concave though the edge is perfect. They are slow in snow.

Ball peen hammer on concave side works. Flame and spray same side works too but messes up temper.

Ken is right, straight is critical.  Straightened alot of badly bent or slightly bent hardened runners by peening them w/ a pneumatic hammer on the concave side. (think of it as  stretching the metal on one side)  Use a blunt tip and run the hammer up and down the side of the runner(wear ear protection) If you can get most of the peening in the area in the runner body thats best but sometimes you need to run the whole height of the runner.  Do not sand out the peening dents as that will just let it go back to being bent.  This is by far the quickest way and usually only takes a few minutes to do.

Thanks for all the comments guys.

Ken...what is flame and spray? do you mean heat the concave side and then quench it? For the amount of bow I have, I think I may be able to stay away from the edge and do this. Would I need to tourch it to red hot?

Yes, the principle is to heat with a torch and quench with a spray bottle. 

Its and art, and I am not the artist, so I would not even pretend to offer the color description and how hot is hot, how fast to spray to cool.   But there are welding artists out there who will do it for the price.  My best runners came from steel from Ron Sherry, and they have peen marks on one side.  Ball peen strikes push metal away from the dimple, and that puts the local material in compression, pushing out the warp.  Good advice from Bill Condon not sanding or smoothing the dimples.

Ken

Ok, thanks, I have temp sensors, and the tempering specs, I'll figure it out. Thanks for the help and ideas!

Well... I tried the heating approach at several temperatures on the concave side with no effect. Then I tried heating the convex side...This time much effect but to increase the bow! Then I went back to the concave side and was able to recover to the initial bow only. Next I tried applying force to straighten past concave to convex and then heat to relieve the stress...maybe a little imrovement.

I gave up, 24 runners to do!!  I went out and bought a 20Ton press. I'll try the 3 point bend apprach next  8)

I know...just buy them!  I live in a snow belt and maybe sail what 1-2 times a year? most of the fun is in the learning and challenge of the build!  ;D

I'd give the peening method a shot. It's really quite fast.

I didn't want to peen the surface because we are electro polishing these. They will have a mirror finish. Also, this brings Cr to the surface and provides improved surface toughness.

Probably should have....Set up my new press, took a 26" steer runner and started at it. Had it pretty close and decided to give it one more shot. Bad move!! I now have 3 pieces of runner to weld back together! :o

The second 26" steer runner went well, I wasn't as fussy. 8) I set up a dial indicator to monitor the amount of bend so I can develop a repeatable process. I hope to have this figured out before I get to the rear runners.

You are way overthinking this process.  A few peening marks, especially if you can get them in the runner body area will be fine.  24 runners to straighten should take no more than an hour or two to do.  Get them straight, then sail them!

The press method is find and no dimples. No issues since adding the dial indicator. No harm in a little thought!