Gauge Plate

Hello all. I bought some 25x6mm ground finish gauge plate and reduced a 140mm length to 21x6mm. It is now curved (3 thou hollow) worse towards the edge that was milled off. I had expected that it would have been annealed sufficiently to avoid this. Am I being over optimistic or am I justified in berating the supplier?

Second issue is can I save it, since there are a quantity of small tapped holes which took time to do and I would rather not have to repeat. I could scrape it flat but don’t want that finish. Considering heating to red and cooling slowly in the hope it might relax. Any thoughts are much appreciated.

Hi Phil,

I'm afraid that's par for the course with a lot of steels including gauge plate. Even though it is ground it still has a lot of stresses in it which machining long edges such as you have done quickly releases.

Possibly the only way to save it but reducing it in width I'm afraid is to take a very fine cut off the convex side to bring it flat then reverse and remove the high points on the other edge. In my day at work this would have been done beforehand to relieve the stress before machining to final size. It's a very rare occasion indeed it gets used these days at home except for the odd cutter.

It might move with heating but that might also bring in further distortion too. I've heated an awful lot of it at work but it's always been quenched and then ground.

Personally I wouldn't hold the supplier to account for it

Not the friendliest of material to machine - hope that helps some

Tug

Edited By Ramon Wilson on 27/11/2022 18:28:35

I would try straightening it in a press, but I have a lot of experiance with such things. You could try it in soft vise jaws with shims. A shim taped on either end and one in the middle, shim width about 10% of the overall job. the object is to only spring it in small stages, about 1mm at a time and check each time before adding shim thickness. The best result would to make it about the original bend, but in the opposite direction. Then apply pressure in the reverse direction and it will straighten and stay there. If I was cutting gauge plate, I would cut the long axis in line with the grinding marks.

Edited By old mart on 27/11/2022 19:00:55

Edited By old mart on 27/11/2022 19:03:40

+1 for giving it a go under a press.

Edited By Baz on 27/11/2022 19:33:11

The trouble with using a press is that you introduce more stress. Thermal cycling in the future then allows those stresses to distort the material.

Martin C

First thought is I wouldn't done it that way. To second previous comments I'd have machined both sides equally first and then drilled and tapped the holes.

Rectangular gauge plate is only ground on the wider sides. The narrow sides are left as sawn, so there may be some stress from the sawing. However, I suspect technique and/or material may be the problem. Where was the gauge plate sourced?

When I made the slidebars for my traction engines i machined 20mm x 10mm gauge plate down to 3/4" x 10mm. I took approximately 0.5 mm off each narrow side. The slidebars are 8.5" long. They are on the engines so I can't measure them against a surface plate. But with a rule held along the machined edge i can't get a 1 thou feeler in. So it should be possible to do what is required without distortion.

To save, I'd clean up the narrow edges to remove the bowing. Not much to remove so I'd draw file rather than try and machine. How much bow is acceptable?

Andrew

Edited By Andrew Johnston on 27/11/2022 20:48:45

Andrew,

did you have to take any precautions with the gauge plate I sent you?

the cutters came out perfectly.

Regards, Martin

Well I guess you could attempt to straighten it but at just 140mm long, and on edge, you are going to need a fair bit of pressure to get that past it's flex point enough to stay not to mention that it may induce a curve in the flat surface in doing so - though that would be much easier to press out of course.

No, if it has to be 21 mm wide exact then I'd say it's make another bearing in mind relieving the stress first by milling each side.

Tug

Edited By Ramon Wilson on 27/11/2022 22:36:42

None at all, just clamped them down as normal. I'll have a look tomorrow and see if I can dig out some pictures.

Andrew