How are you measuring your edge thickness?

Matt Rochester

Matt Rochester

Joined
Nov 28, 2014
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1,864
How are you measuring your edge thickness before sharpening and do you have a tolerance? +-.001”?

Happy thanksgiving!!!
 
I use a digital caliper. But I agree a mikrometer would be more convenient.
Also, you can just look at it I guess.
 
I guess I should’ve been more specific. I use a dial caliper currently but was wonder more about the process I guess. It’s a little inconsistent without knowing for sure how far up the edge you are measuring. I don’t know how off your readings would be but if you measure.093” up at one point and .005 at another then your readings will vary. Maybe I’m overthinking it but I’m trying to ensure that I’m getting the edge thickness as consistent as I can. I’ll check out the sheet metal gauge.
 
it makes a big difference how far up you measure which is why it hard to measure exactly. This also depends on the grind. A FFG 2" chef knife vs a low bevel saber. Usually I take my knifes till they're forming a burr and then case the edge back to the thickness I want.

I would be handy to glue a little stop on the caliper right at the edge so you always measure a consistent depth in from the edge.
 
scott kozub said:
it makes a big difference how far up you measure which is why it hard to measure exactly. This also depends on the grind. A FFG 2" chef knife vs a low bevel saber. Usually I take my knifes till they're forming a burr and then case the edge back to the thickness I want.

I would be handy to glue a little stop on the caliper right at the edge so you always measure a consistent depth in from the edge.
Click to expand...
That’s the kind of stuff I’m looking for. I will get a dedicated pair of calipers and try and make a stop on one jaw about .005” up and always measure with the edge resting on that. That will give you a real close idea of what your “behind edge” thickness is after sharpening.
 
scott kozub said:
it makes a big difference how far up you measure which is why it hard to measure exactly. This also depends on the grind. A FFG 2" chef knife vs a low bevel saber. Usually I take my knifes till they're forming a burr and then case the edge back to the thickness I want.

I would be handy to glue a little stop on the caliper right at the edge so you always measure a consistent depth in from the edge.
Click to expand...

Gear Tooth Vernier Calipers are made to do just that.

Starrett ones are something like $1,600
but you can get cheapie digital ones on the amazon

non digital imports 75us$
https://www.shars.com/20-2-10-1-diametral-gear-tooth-vernier-caliper
 
Matt Rochester said:
That’s the kind of stuff I’m looking for. I will get a dedicated pair of calipers and try and make a stop on one jaw about .005” up and always measure with the edge resting on that. That will give you a real close idea of what your “behind edge” thickness is after sharpening.
Click to expand...
It is much easier to calculate BTE and it will be 100 % accurate .Real close idea of what BTE thickness will be , depend on sharpening angle too.So where you think that you need to measure on 0.20mm thick edge and 25 degree sharpening angle to get 0.30mm BTE ?
Use micrometer , don't waste money for nothing .....Set it on say you want BTE 0.30mm and see how deep it goes upper on blade with guess that sharpening angle will end up there :)
 
I usually go until it starts forming a burr or chipping a little. I'm generally making thin kitchen knives, so go as thin as i can then add a very small secondary gets me a good result.
 
A sheet metal gauge will be the simplest method of measuring the edge. Place the edge on the slots and go down until it doesn't seat on the slot. The last one was the edge thickness. If your gauge doesn't have the inch or mm size on it, use a chart to convert gauge to inch/mm.

Calipers can do it, but you need skill to get it right. many variables can affect the reading.
 
I use digital calipers and measure at the transition point from the primary to secondary bevel. It's important to specify what the edge angle is at when you do measure though... An edge .010" thick at 20 dps will be much thicker than an edge .010" thick at 15 dps. Most people miss this point.

For convex edges blended into the grind it must be measured differently.
 
Hand ground primaries are pretty much always a little apple seed shaped at the very edge due to the nature of hand grinding and the little bit of give on a belt. This tends to make the measured edge thickness appear a little thinner than it really it. With this in mind it is a little more meaningful (to me) to measure edge thickness just a tiny hair back from the edge rather than trying to measure the very edge (which gets removed during final sharpening anyways). I use calipers.
 
razor-edge-knives said:
I use digital calipers and measure at the transition point from the primary to secondary bevel. It's important to specify what the edge angle is at when you do measure though... An edge .010" thick at 20 dps will be much thicker than an edge .010" thick at 15 dps. Most people miss this point.
Click to expand...

This isn't exactly right. If your measuring right at the transition point (primary to secondary bevel) the edge sharpened at 15dps will be thicker than the 20dps as the transition hased moved further up the blade. However if your measuring a set distance from the edge somewhere within the sharpened edge than the 15dps will be thinner than the 20dps.

Another way of thinking of it is to think of a true scandi grind. The tbe is very thick because its so high up the blade but the cutting edge is extremely sharp as its only about 7dps or so. The tbe say 0.002 from the edge is very thin.
 
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