Build Your Own Rockwell Style Hardness Tester

[Ray Rogers]

Have you ever used files, drop tests, or phases of the moon to try to figure out how hard your blade was? Ever wished you had a Rockwell tester but couldn't make yourself spend $1000 to get one?

Stop guessing about your blades, get off your duff, and build your own hardness tester!

All kidding aside, after months of fiddling around, calculating, building, tearing apart, and building again I have finished the design and complete documentation on a functional Rockwell style hardness tester that almost anyone can build. If you can build your own belt grinder you can build my hardness tester. My tester is a completely original design and does not look like a commercial unit but it works on exactly the same principle and it can be built with commonly available parts.

If you would like to see the prototype and learn more about it, look here:

The Rogers Hardness Comparator

[VSMBlades]

Wow Ray that looks awsome.

How long do you think it would take to build one with a basic understanding of welding and fabrication?

[jdltd]

Those look great. I honestly hope you sell a lot of them!! Best of luck

[Ray Rogers]

VSM,

I was teaching myself to use my new stick welder when I built this thing (as you can tell by the ugly welds) but, even so, it didn't take long to do the basic assembly. I'm a full time knifemaker so I could only work on it an hour or two every couple of days which makes it difficult to estimate the total time but I'd say anyone with fabrication experience could come pretty close to doing all the major work in one day if all the parts and pieces were cut out and on hand. Anyone with 4 or 5 days of free time should be able to do it - it's easier than building a folder!

JDLTD,

Thanks, I need the money :-D

[andy gascoigne]

Great work Ray I'm a big, build it yourself fan and will be sending for your plans soon as I've finished installing the digital control on my home built HT furnace.

Have you compared your readings against a factory made Rockwell tester?? How close can you get?

Are the dimond penetrators very expensive?

Best regards,

Andy..

[Ray Rogers]

Andy,

I have a factory built Rockwell tester so I spent a lot of time comparing them. The same diamond penetrator was used on both machines, in fact. The accuracy comes from how consistant you are when you use it and how well you have calibrated the machine - which is exactly true of the commercial unit as well. The major difference is in the dial indicator but getting within one Rockwell point is not difficult. My commercial unit is accurate to about half a Rockwell C unit.

The diamond penetrator is the single most expensive part of the machine at $75. A parts list is provided with part numbers, sources, phone numbers, websites, and current prices.

I built this thing because we see so many questions in the forums about how to tell how hard a blade is when you don't have a Rockwell tester. It's been a little surprising to see so few questions on the first new major tool to come along in years, especially from a group so interested in building their own equipment....

[Quenchcrack]

VERY interesting! Have you checked the performance of your unit against standard calibration blocks? Most commercial machines will calibrate from about Rc 20 to about Rc 60 but if yours would calibrate from Rc 40 to Rc 60, it would be a bargain.

[Ray Rogers]

I have standard calibration blocks for my commercial unit and I used them on the RHC (Rogers Hardness Comparator ) It worked in all the ranges for which I have blocks - 20, 40, and 60. Of course, I can only speak for the commercial unit I actually own - and a $4000 unit that I used to own - but neither of them would accurately read from Rc 20 to Rc 60. The instructions say to buy a test block in the range you expect to be working in, for knives that would be the 55 - 65 range block. I have several of these blocks and they all measure 62,4 and 62,5 for some reason. If you calibrate to that, you will get reasonable accuracy at Rc 60 but when you get into the low 50's things start to drift. In the 40's I'm not sure it's even in the ball park anymore. Just the nature of the beast.

So, to answer your question, no, I haven't tried to see how wide a range of accurate readings I can get out of the RHC. I will stipulate that the range is probably less than my commercial unit but some of that will be affected by your skill in using the machine. What I can say is that if you put two blades under the penetrator and you know both of them are Rc 60 exactly, you will get the same reading on the dial and that's basically all any Rockwell style tester does.

Right now, the way I imagine this machine should be used would be for the user to learn what readings he gets on a Rc 58, and Rc 60, and an Rc 61 block. Then, assuming you want your balde to be between 58 and 60 you can tell when it's in that range. If it's outside that range, you may not know exactly what it is but you know it's either harder or softer than you want it to be....and that's really all we need to know.....

[Ron Claiborne]

Got Ray`s set of plans today and im really excited to get started on the project ,Ray has done a great job with this and its step by step, heck even i can understand it .
I can now have a Hardness tester in my shop that i feel will no doubt be of great use .
thanks Ray for all the work and your effort in making this project doable and in term that us laymen can understand ,you engineers and physics people will love it .

[Ray Rogers]

Thanks to the many supportive and imaginative knife makers out there - including a surprising number from overseas - I was able to recoup my developement costs on this hardness tester project. Full time knife makers usually have pretty tight budgets but, even so, I can now afford to reduce the price on these plans and make them more widely available.

My sincerest thanks to all those who supported this project with your encouragement as well as your cash..........