Sorry for the world's dullest topic...
Have to certify hardness on a casting that won't fit on a Rockwell tester. Weighs about 10 lbs. Only induction treated on one small appendage.
I can cut off the treated part, but have to use a hand grinder without coolant, so the hunk might get hot. OK, cut slowly with lots of air or use a spray bottle and a raincoat.
But then the chunk has no flat / parallel surfaces to set on the stage. Would have to take off 1/8 to 1/4 inch (don't know the depth of penetration). Maybe could use a small vise but not sure if that would affect the reading. OK, try that with a reference piece to find out...
Mostly I was hoping to use a Leeb on the intact casting. So we bought the world's cheapest Leeb (literally eBay "sort by price") called DY-10 for $200. I know, didn't expect much. We don't have much budget for test equip. I could have convinced them to pay $5000 but would be buying a pig in a poke as we have no experience with Leeb. If it didn't do the job they would remember me for that. So the cheapie was just to get my feet wet.
(We also have a cheap ultrasonic tester that is completely worthless. It will read HRC 20 to 70 totally at random. Our calibration service said to throw it out, but there is one job where it seems to work as a go-nogo check so I kept it. It has a diamond bigger than my wife's ring so maybe I'll pry it out for our anniversary.)
Surprisingly the little Leeb seems to work pretty well. Consecutive readings have low variance (maybe twice that of the Wilson on an as-machined surface). Seems to correlate pretty well with Wilson (for my purposes +/- 2 is OK). But it is hard to compare, as the Leeb only works on heavy objects and the Wilson only works on small or cut-off pieces.
Surface prep is necessary (on a rough casting) but I am hoping a Dremel sanding drum is good enough. We have a surface grinder but some of these odd-shaped castings would be difficult or impossible to hit the desired area. And that can overheat the surface very easily - 4140 can be hard to drill after surfacing (the way I do it anyway ).
So far I haven't really asked a question other than putting my ignorance on display but that never stopped you guys from offering helpful advice!
Have to certify hardness on a casting that won't fit on a Rockwell tester. Weighs about 10 lbs. Only induction treated on one small appendage.
I can cut off the treated part, but have to use a hand grinder without coolant, so the hunk might get hot. OK, cut slowly with lots of air or use a spray bottle and a raincoat.
But then the chunk has no flat / parallel surfaces to set on the stage. Would have to take off 1/8 to 1/4 inch (don't know the depth of penetration). Maybe could use a small vise but not sure if that would affect the reading. OK, try that with a reference piece to find out...
Mostly I was hoping to use a Leeb on the intact casting. So we bought the world's cheapest Leeb (literally eBay "sort by price") called DY-10 for $200. I know, didn't expect much. We don't have much budget for test equip. I could have convinced them to pay $5000 but would be buying a pig in a poke as we have no experience with Leeb. If it didn't do the job they would remember me for that. So the cheapie was just to get my feet wet.
(We also have a cheap ultrasonic tester that is completely worthless. It will read HRC 20 to 70 totally at random. Our calibration service said to throw it out, but there is one job where it seems to work as a go-nogo check so I kept it. It has a diamond bigger than my wife's ring so maybe I'll pry it out for our anniversary.)
Surprisingly the little Leeb seems to work pretty well. Consecutive readings have low variance (maybe twice that of the Wilson on an as-machined surface). Seems to correlate pretty well with Wilson (for my purposes +/- 2 is OK). But it is hard to compare, as the Leeb only works on heavy objects and the Wilson only works on small or cut-off pieces.
Surface prep is necessary (on a rough casting) but I am hoping a Dremel sanding drum is good enough. We have a surface grinder but some of these odd-shaped castings would be difficult or impossible to hit the desired area. And that can overheat the surface very easily - 4140 can be hard to drill after surfacing (the way I do it anyway ).
So far I haven't really asked a question other than putting my ignorance on display but that never stopped you guys from offering helpful advice!