[QuinnSjoblom]

I'm a knife maker that would like to be able to test my blade hardness. I already have a set of files for getting within 5 points or so hrc but that's just not accurate enough. I've been searching for an affordable Rockwell tester but they are very expensive and I'm just not ready to spend 1000+ for that right now. I'm wondering if I have another option.
First of all, I remember seeing in an nyccnc video John had a tester that seemed to consist of just applying a specific force to an indenter and then measuring the diameter of the resulting indent using a magnifier with a scale and that correlated to a hardness. I haven't been able to find any tester like this but I have no idea how accurate that would be. What I do already have is a 200x digital microscope and a press that I could set up with the needed indenter and apply a specific force using a lever and weight. I have a glass slide for my scope that has .01mm graduations that I could use to accurately measure the indentation. Calibration would be done simply by purchasing various hardness calibration blocks, apply the indent to it, measure the result and write a table of indent diameter vs hardness. The range I'm looking to measure is 55 to 65 hrc Again I have no idea how accurate this is cabable of being, but it's the cheapest option I can think of.

If this method of measuring an indent diameter isn't capable of any better than a few points hrc accuracy, then the next option would be building a setup that does an actual hardness test the same way more expensive machines do. It applies an indenter first with an initial load, then a secondary larger load, then backs off to the original load and measures the rebound distance of the indenter. I believe I might be able to build such a machine for a few hundred bucks including some parts I already have. I have some ideas on how to do it, but it wouldn't be quite as convenient as the usual machine. I have some linear rails and ball screws laying around that might be useful. I'm thinking maybe the ball screw for the downward force would make it easier to accurately apply the force by applying a specific torque to the screw. Better resolution than just applying a specific force to the lever of an arbour press or something. The height measuring could be done by just having a dti mounted to the indenter assembly that I can position on the piece being measured while secondary load is applied and zeroed out, then measure height gain as I back off to the initial load. I have a cnc mill and I believe I could design and build something in a weekend.

So here's where I need some advice/input. First of all, is there currently something I can buy for a couple hundred bucks capable of 2 point accuracy between 55 and 65 hrc?

Second, is anyone familiar with the shortcut method of just applying an indent with specific force and measuring the diameter of indent? If so, how accurate is it?

And third, if I build a more traditional Rockwell tester, where would I find a detailed layout of the test data? I would need to know how much force is needed specifically for initial and secondary load, as well as how the rebound distance correlates to the hrc scale. I have no idea what kind of resolution we are talking and I would need to know that before I could decide if it's something I would attempt to set up myself.

In the end it will be easy to test the accuracy of whatever setup I use just by testing hardness calibration blocks, but I don't want to waste the time if it's unlikely I will be able to build something capable of consistent accurate results.

[fc60]

Greetings,

Watch eBay for a good used Ames Portable Hardness tester.

https://amesportablehardnesstesters.com/

Make sure all the parts are present.

Especially the 62 HRC calibration disk.

For knives, the Model 1 will suffice. The Model 2 will also work if the price is right.

They are still in business should you need parts.

Cheers,

Dave

[QuinnSjoblom]

Greetings,

Watch eBay for a good used Ames Portable Hardness tester.

https://amesportablehardnesstesters.com/

Make sure all the parts are present.

Especially the 62 HRC calibration disk.

For knives, the Model 1 will suffice. The Model 2 will also work if the price is right.

They are still in business should you need parts.

Cheers,

Dave

Yeah, I've been checking ebay weekly for months and it seems like a decent used tester is approaching 1000 bucks. I've seen that ames tester a few times but I think 700 is the lowest I've seen. I'm sure that's a good deal compared to new, I just have other things higher up on the list for that kind of money. I'm really hoping to find at least a temporary solution for a couple hundred bucks. Might not be a realistic expectation. I'm somewhat early in my knife making endeavors. Just finished refining my design a couple months ago and have a small batch ready to sell to people who are waiting, but I don't feel great about handing over knives that just pass the 55hrc file and questionable on the 60. I really have no idea if my heat treat is optimal.

[jaguar36]

Why not just get a used one? They show up frequently at a auctions for a couple hundred bucks. Or get one from HGR, they have a bunch right now.