Rockwell hardness testing files

I have some small parts that have been heat treated. They are too awkward to fit in a Rockwell tester. I have seen Rockwell testing files in the Wholesale Tool catalog. Has anyone used them? Good, Bad, Indifferent? Thanks.

I've used the files available from MSC and they work well on tool steel, casehardened parts that are carburized are usually OK, and parts that are quick cased or cyanide cased probably should be very careful as the case is VERY thin, Craig.

Sounds silly, but always start with the harder ones and work down. Otherwise you end up with a bunch of worn files.

But they do work fine.

Either the file cuts the part or it doesn't. Pretty simple.........

My experience is that they'll get you in the ballpark, but aren't very accurate when compared to a penetration type tester. First, there's the question of the file accuracy itself. Then your own interpretation of "did it cut?" Plus variables of how hard you push the file into the work, wear on the files, etc. Still, if ballpark is all you need . . .

Would something like a portable hardness tester (e.g. Ames) or one of the ultrasonic ones work for your application?

Hardness testing files are basicly a set of sharp to dull files.
If you have a rockwell tester, get out some old files and some heat treated scrap in the range you want to test and see what files will cut at what hardness. Mark them and see if the part in question is in the ball park.

Rebound and other portable testers can be excelent or they can be random number generators. Most rebound types need parts in the 20 lb class or larger. Smaller parts deflect and bounce away giving reduced readings.

If you use a portable unit, check it against parts that fit in your standard tester.

Hopefuly you specified on the print where to hardness test the part. If the part is not uniform in thickness, it did not heat uniformely when it was tempered and you will have some variation in hardness accross the part. This can be a complication if you have a bad part and try to take it up with your heat treater.

Another issue I have seen on bar stock is the heat treater not holding the part at temperature long enough to raise the core above critical temperature. ASTM requires the tensile bar be pulled at mid radius, so they heat it long enough to get the tensile bar to pass and no more. Same alloy from the same mill, and one outfit wont get it hard to the core, the other does it every time.

ahall said:

Hardness testing files are basicly a set of sharp to dull files.

Click to expand...

Ideally, they're all sharp -- just heat treated to different hardness. Might be able to tell something from a handful of files from various batches and ages, especially if the part had been heat treated "file hard." But an assortment of regular files from new to worn would not have been heat treated as soft as the softest or as hard as the hardest in a test set.

The advantage of something like an Ames tester is that it is penetration tester. Agree that the rebound types depend far too much on variables like thickness of the part, how the tester is set, etc.

It is a skill with a short learning curve

Like anything you have to learn a little. Get some parts with known hardness and practice a little.

A good scale can be used to .010 pretty easily. .005 with practice. .003 if you are good.

A lady in one shop had perfect pitch and would throw a rivet stem om thr floor and tell if it was hard or not. Damn frustrating, she didn't miss.

It is a course tool. If you really need to be accurate, within a point or so, you are fooling yourself.

I drone on, sorry.