How to Flatten a Thin Steel Plate?

Today's Mission Impossible is to make a Stainless Steel kick plate for a wooden garage side-door.

From a slightly larger off-cut I've successfully trimmed a plate to fit (765 x 170 x 1.2mm / 30" by 6¾". Unfortunately on close inspection the metal is not quite flat and that will complicate fitting it to the door.

Searching the web hasn't helped much: the closest suggestion I found not requiring an industrial roller was to clamp the bent plate between two thicker true plates, heat the whole to red heat. and then cool slowly. I don't have the facilities to do that.

Can anyone suggest a way of taking mild bumps and curves out of thin steel sheet please?

Thanks,

Dave

Edited By SillyOldDuffer on 20/07/2017 13:41:16

Screwing to a sturdy wooden surface often works for me, kick any high spots flat

Bright yellow (Incandescent) heat and rollers.

Regards Ian.

How about just glueing it into position with a thick lump of something clamped across it until it sets?

^^^^ This.

If it has bumps and curves in it, the metal will have been stretched. To get it back flat again you would need to shrink the metal back to original size. Stainlness, being a mongrel to work, due to its tendency to work harden, will resist this process. Not worth the vig.

Would love to know the answer to that one too !

I love the idea of a thick lump of "something".

Hi Dave

Take out your trusty joiners plane and take a shaving off the door - then you won't need to kick it to get it open and you can use your piece of stainless steel for something more creative!

Norman

Hello Dave,

​After a number of years spent using a hydraulic press to straighten out heat treated spring steel plates, I found the secret was to over bend the plate from the side with the bulge to put a 'set' back into it in the opposite direction.

Don't overdo it, but you do need to see it bent slightly. Then ease it back again to take out some of that set; it should then be essentially flat and it should lie flat on the surface you attach it to

Regards
Brian

.

I dont think Dave needs the plate so as to be able to kick the door open. I,ve seen these plates on many garage doors,they appear to be there to protect the bottom of the doors from------What?

I have never managed to flatten any piece of thin strip,so I,m listening !.

Kick plates tend to get used more to hold the door open with a foot while your hands are tied up carrying something through the doorway, particularly if it is a door into the house where the fire door should be fitted with a closer of some sort. In commercial properties they will also protect against floor polishers etc much like a skirting protects the bottom of a wall.

Good clout with a hammer should do the job (with a dolly if we're being dainty), As well as a little manual compression. I wouldn't bother trying to make a jig or machine to do it. I even use my own bench vice and soft jaws to neaten things out.

If anything when you fix the plate to the door that should have some kind of straightening out of it's own provided you can get it relatively even and straight.

The only time you've got to worry is when the stainless is 304, because it's a pig. 316 or 303 are easier to work with.

Any residue marks that remain will just have to be rubbed off manually, if it's bothersome. 

Michael W

Edited By Michael-w on 20/07/2017 18:49:33

Thanks again chaps. A mix of overbending and hammering against a thick plank of wood plus some judicious vice work improved things considerably. Far from perfectly flat but close enough for my purpose.

One thing I would do differently given a second chance. I used a hand nibbler to cut the sheet to size. On the long edge it left a ripple effect that shows up when the light hits it at the right angle. Nothing I tried shifts that pesky ripple. I suppose sawing it might have caused other problems. I hate stainless steel!

Cheers,

Dave

Edited By SillyOldDuffer on 20/07/2017 21:02:03

Hi Dave,

Like I said,your posts are always interesting.I wonder how a band saw would cope with s/s?. I have used my wood band saw to cut mild steel sheet,with a metal cutting blade but it,s too slow. Never knew there were so many different grades of stainless. I have a few bits of it,no idea what they are,just that they are hard to cut and harder to drill. Think I,ll just give it a miss,life is too short !

I use a thin cutting wheel in my angle grinder for jobs like this. You can get special discs for SS, not tyerribly expensive.

I would second Duncans suggestion. I have been doing quite a lot of stainless for the cladding and funnel of my steam launch boiler and have been using 1mm discs that Bosch sell in a round tin. The tin is also useful afterwards for storing small items! I don't know what grade the stainless is it came from the scrappy but it is about a millimeter thick. Rolling it to form the funnel was a bit of a mission, and I also had to make a transition piece at the bottom from round to rectangular, which was a good exercise for 3D CAD.

John

Thanks Duncan & John. I didn't know you can get cutting wheels for stainless! But then I hadn't thought of using an angle grinder either. Pity, because using the nibbler has done my fingers in. I woke up convinced I'd suddenly got rheumatism. Wrong again, it's the effect of unaccustomed exercise.

Dave