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Milling a hardened shear blade?

JasonPAtkins

Hot Rolled
Joined
Sep 30, 2010
Location
Guinea-Bissau, West Africa
Hi all,
A local welder brought an unmarked bench shear in to be "adapted". I don't see how the blades that are on it are original to the machine, because they overlap each other a good 0.300". The only fix is to take thickness off of one or both of them and then resharpen them.

I started shaving thickness off on my manual surface grinder, but taking a thousandth off at a time got old REALLY fast.

The blade is about 3/4" thick, probably 1.5" x 8" or so.

Is there any possibility that I can take a few .050" passes with a carbide insert facemill to get close, and then go back to the grinder to finish up?

I don't know the manufacturer, alloy, or HT of the blades, but I imagine they must be pretty hard if they're meant to cut mild steel.

I can try it to find out, but would rather not ruin 6 inserts in the process if everyone already knows carbide won't be able to touch it, or will heat it enough to ruin the HT of the blade. :)

Thanks!
 
Solid carbide end mills can cut most hard steel I've successfully cut HSS tooling,ball bearings and races,iorn worker knives ect
I like a .5 4 flute end mill that I hand grind a .05 ish 45` lead on I'd start at 1500 rpm .001 fpt no coolant use air blast full doc small step over like .010 climbing cut and up feed and rpm from there
 
Solid carbide end mills can cut most hard steel I've successfully cut HSS tooling,ball bearings and races,iorn worker knives ect
I like a .5 4 flute end mill that I hand grind a .05 ish 45` lead on I'd start at 1500 rpm .001 fpt no coolant use air blast full doc small step over like .010 climbing cut and up feed and rpm from there

Good starting point, thanks. I've turned a lot of hard and forged steel with carbide (since junk yard car parts are most of my available stock), but didn't know how much harder a shear blade would be. Hard turning can bog my 5hp lathe down on a lot of DOC, I imagine my 2hp mill will be like 10th the MRR because of the geometry of the two tools. However, I don't have a ton of volume to remove, so I'll give something like that a try.
 
Hi all,
A local welder brought an unmarked bench shear in to be "adapted". I don't see how the blades that are on it are original to the machine, because they overlap each other a good 0.300". The only fix is to take thickness off of one or both of them and then resharpen them.

I started shaving thickness off on my manual surface grinder, but taking a thousandth off at a time got old REALLY fast.

The blade is about 3/4" thick, probably 1.5" x 8" or so.

Is there any possibility that I can take a few .050" passes with a carbide insert facemill to get close, and then go back to the grinder to finish up?

I don't know the manufacturer, alloy, or HT of the blades, but I imagine they must be pretty hard if they're meant to cut mild steel.

I can try it to find out, but would rather not ruin 6 inserts in the process if everyone already knows carbide won't be able to touch it, or will heat it enough to ruin the HT of the blade. :)

Thanks!

You might take passes about .005" deep at the most. But you can feed it pretty hard, so it shouldn't take all that long. The shock of exiting the cut at the edges and near holes will kill your inserts, though. For this abusive sort of work, I'd grab an old 1/2" solid carbide endmill and sharpen up the tip (even just intelligent bevelling of the corners of a used up cutter would be good enough to create short life cutting edges). Crank your way around inside the profile avoiding unnecessary exits until you're near the end.
 
Depending on the HP of your grinder deeper cuts may be possible. I have only 1hp. To do that job I'd cut a step on the wheel, start with a .005 step on the first .100, feed down .005 and see how it cuts. Cold air or better to handle the heat. Increase or decrease feed as needed, step across at .020, and increase from there.
The steps generate less heat than a single .010 cut.
 








 
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