Measuring and testing equipment

Starfish

Starfish

Joined
Jun 14, 2001
Messages
1,256
Now that I have decided on a sharpening system (thanks all who helped!), I want to pick up some equipment that will help me to assess the knife in terms of edge thickness, polish level, sharpness, etc. I am thinking of the following items:

1) Calipers - for measuring the thickness of the edge, determining edge angle (via trigonometry), etc.

2) Loupe

3) Razor Systems edge tester

Are there other items that would be useful to me in assessing a knife edge? What are your recommendations for manufacturers and models?

Thanks,

Matthew
 
You'll find that a loupe or even a small microscope will teach you a great deal about sharpening.
 
Gollnick right, what ya need to do is learn what sharp looks like magnified.

Examine a knife that's sharp magnified then look at a dull one magnified, once you know what sharp is, you'll be more likely to recognize it when you do it.
 
A loupe or small microscope...that's a good idea. Any recommendations as to minimum power that will help me see the difference between a sharp edge and a dull edge?

Thanks,

Matthew
 
Starfish said:
A loupe or small microscope...that's a good idea. Any recommendations as to minimum power that will help me see the difference between a sharp edge and a dull edge?

Thanks,

Matthew
Click to expand...
Radio Shack makes a small handheld microscope under $10... goes from 60x-200x. Works great.
 
cbwx34 said:
Radio Shack makes a small handheld microscope under $10... goes from 60x-200x. Works great.
Click to expand...

Thanks cbwx34! Is this the microscope you mean? It says only 60x-100x though.

Any recommendations out there for a decent set of calipers? I have no idea whether to get a vernier or dial caliper, nor do I know the precision requirements for measuring knives...

Matthew
 
Calipers...
Verniers are okay, but a bit hard to read with precision, although you can get .001" resolution.
Dial calipers are nicer, as they have .001" resolution, are easier to read, but You do have to watch to keep metal particles ( and dirt ) out of the rack that drives the indicator assembly.
Digital calipers - same or better accuuracy and resolution, plus you don't have to worry about getting them a bit dirty (at least the ones made these days.
Other features that are nice to have is carbide tipped jaws. Less wear in the long run, but at a greater cost up front.
Digitals also can be switched from inches to metric on some models.
A 6" caliper is about the standard size carried everywhere.
 
Starfish said:
Thanks cbwx34! Is this the microscope you mean? It says only 60x-100x though.

Any recommendations out there for a decent set of calipers? I have no idea whether to get a vernier or dial caliper, nor do I know the precision requirements for measuring knives...

Matthew
Click to expand...
Yup... that's the one... and my bad...it is 60x-100x. Wow on sale 6.99... not bad. I use mine alot... it has helped me often to answer why won't this knife sharpen?
 
Something like these would probably be more practical
http://store.yahoo.com/egeology/magnifier.html
They are easy to use to check your progress and strong enough to see fine scratch patterns. I keep one handy to check to see that I'm getting to the edge and when it is time to switch to the next grit. (a jewler's eye loupes or spectacle lenses like they sell here http://www.gesswein.com/catalog/index.cfm?cat=17&sub=2&catalog=1&CFID=413564&CFTOKEN=99369092 would also work)

I've got one of these http://www.lwscientific.com/LWS/Sco...eo&CatSub=Dual+Magnification&ProductID=VIS-13 in 10-30x with spare eyepieces to get 20-60x Fun to look at an edge under higher power, but the depth of field is so shallow that even 30x is a pain and of little use other than to admire your handiwork.
 
howiesatwork said:
Calipers...
Verniers are okay, but a bit hard to read with precision, although you can get .001" resolution.
Dial calipers are nicer, as they have .001" resolution, are easier to read, but You do have to watch to keep metal particles ( and dirt ) out of the rack that drives the indicator assembly.
Digital calipers - same or better accuuracy and resolution, plus you don't have to worry about getting them a bit dirty (at least the ones made these days.
Other features that are nice to have is carbide tipped jaws. Less wear in the long run, but at a greater cost up front.
Digitals also can be switched from inches to metric on some models.
A 6" caliper is about the standard size carried everywhere.
Click to expand...

Howiesatwork,

Thanks for your review. What I'm getting out of your post is that I should be looking for a pair of calipers that have at least 0.001" resolution. How much should I expect to pay for that level of resolution, and do you know of any decent brands?

Here's a pair of dial calipers at the Home Depot near me. Would this suffice?

Thanks,

Matthew
 
Hi Starfish. Excellent quest.

on the loupe; I used to tell my salesmen that I was their #2 teacher. Loupe was #1 teacher.

At least 10X- I think for you 12X would be best, try Edmund scientific. I use 10, 12, 20 and 50 (that I carry with me) and a 50-100 stereoscope in the lab.

sal
 
Sal's on the money on the magnification. 10-12X is fine. 60x-200x is way too much. A loupe would work well, but a nice Stereo microscope would be even better as it lets you see a 3d image, but of course would be a bigger investment.

For calipers, you can probably get by with a $20.00 chinese set from Harbour Freight. I have a pair and check them against my Mitutoyo Digimatics and an old set of American made Starrett dials and they seem to work fin for casual work.

If you want real precision measurements, but a 0-1" Micrometer. Then you can get resolution to .0001. Even the best calipers are usually only accurate to .001 even though a lot of the digitals claim .0005 resolution.

John
 
These aren't too bad for a larger 16x magnifier http://www.frostproof.com/catalog/m37.html
They have a nice lens size comparison chart too http://www.frostproof.com/handlens.html the 12x Eschenbach Doublet has a decent size lens too

Edmund has Hastings triplets but, like B&L, their lenses are a bit smaller than others. They do have 6x direct measuring comparators though...
http://www.edmundoptics.com/onlinec...d90016de5-2C83AB43-3048-41AD-8456B2C437E5D476 that allow you to measure things optically
 
jmxcpter said:
For calipers, you can probably get by with a $20.00 chinese set from Harbour Freight. I have a pair and check them against my Mitutoyo Digimatics and an old set of American made Starrett dials and they seem to work fin for casual work.

If you want real precision measurements, but a 0-1" Micrometer. Then you can get resolution to .0001. Even the best calipers are usually only accurate to .001 even though a lot of the digitals claim .0005 resolution.

John
Click to expand...

John - what are the drawbacks to a cheapie form Harbour Freight? Is it that the calipers won't hold up as well, or that it won't be as precise as a more expensive pair (precise being the repeatability of the measurement)?

Also - a more general question about loupes; what kind of information will I be looking for in the loupe? Will I use it solely to determine when I have finished sharpening at a particular grit level? Will I be able to see a burr? Will there be other information I can glean from looking at the edge under magnification?

So many questions!

Thanks,

Matthew
 
My number one testing equipment would be a good, bright and not too diffuse lamp, were you are sharpening. Look at the reflection from the edge, you can see blunt sections of the edge easily with the bare eye and often you can even see the burr as a destinct "fuzzy" reflection on the edge. Scattering of light is a very powerful tool, you don't get to see an image but it allows you to see features that are actually below the resolution of a top notch light microscope. You can see dust particles in a ray of sunlight by the light scattering that you would need an electron microscope to resolve. If you see ANY light scattering of your edge, you will know, that you still have some work to do.
 
Hmmmmm, a loupe is cool and all but if you really want to see how sharp your knife is, and how your sharpening skills are working, cut something.

Cut what? It depnds on what you use your knife for, if you do a lot of utility work, maybe cardboard, carpet, stuff like that. Do a lot of kitchen work, try carrots, onions or something.

Like I said, loupes are cool for seeing stuff, but knives were meant for cutting, and the proof is in the pudding.
 
HoB is correct.. The loupe will help you learn what those glints mean, like maybe a small part doesn't reflect like the rest, and the loupe will let you see that you must have rocked the blade a little and missed getting a little sliver of it with the last stone. It also shows the actual scratch patterns so you can better see when you can go to the next finer grit. Or maybe you blade isnt flat (I've got some small pocket knife blades that seem to have curve to them and gave up trying to grind them flat, so until wear eventually does grind them flat, the loupe helps me touch up areas around the bend on one side and the dish on the other).
 
Really, mostly what you'll miss is pride of ownership if they're for occasional use. I bought them before I got serious about my shop and bought all this other expensive stuff, but I use the HF ones most often. I've never bounced them, but I'd feel a lot better if they hit the floor than some of my more expensive and "better" tools. They probably won't hold up as long in the long term, but I've had them for a couple years and so far no complaints. The action is not as smooth as the Starrets, but they were probably only 20% or less than what the Starretts were new. They're really quite good considering the value. Absolute accuracy isn't what dial calipers were made for in the first place. The jaws allow for too much flex for real precision. That's what a micrometer is for. Calipers are for "pretty close" work. They seem pretty repeatable to me so far.

John

Starfish said:
John - what are the drawbacks to a cheapie form Harbour Freight? Is it that the calipers won't hold up as well, or that it won't be as precise as a more expensive pair (precise being the repeatability of the measurement)?
Click to expand...
 
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