Chart of Blade Angles for Flat Grinds.

Status
Not open for further replies.
Steven Penner

Steven Penner

Joined
Jan 29, 2006
Messages
606
Chart of blade angles for Flat Grinds.

I thought I would share this with everyone.

I know that many of you can eyeball everything and it turns out spectacularly.
But I find that I think, sketch, measure and draw things many times over until I can visualize it properly and get close to what I want.

I like to know the grind angles in degrees. It helps me to draw up a design by visualizing the blade cross section with a protractor, as well as setup my grinder.

I found myself calculating angles over and over again.

I finally put my Excel spreadsheet skills to work and created a chart for myself. With a quick glance, I can now see what the angle may be and adjust the stock thickness or bevel width accordingly.

The chart gives the angle on each side of the blade.
It can be used to set the platen angle when the blade blank is held perpendicular to the rest.

The blade angle at the edge is actually double this angle.

By Bevel Width- I mean the length of the longer angled line- the Hypotenuse
Although at these small amounts, it doesn’t amount to much difference if you just use the whole stock width.
 

Attachments

Last edited:
Since Keith mentioned it, I re jigged my formulae to compare both methods of measuring the bevel height.

I calculated it so that the Bevel Height is the Adjacent side.
They work out exactly the same for the degree of precision displayed in the chart.

You can measure the bevel height on the flat, just as you would draw out a pattern on a paper.
 
Last edited:
thats cool thanks it will make picking razor spine thickness to blade length even easer for the non STD. sizes and still get the right angle
 
Thanks Steven, I find myself calculating and re-calculating those same angles. I will print this out and hang it on my shop wall.

Thanks again!

John
 
I could have buggered something up – lets see.
Math is not my strongest skill

5/32 spine thickness and 1” bevel height

5/32 .156 25 is the spine thickness and the smallest side of an Isosceles triangle.

74px-Triangle.Isosceles.svg.png


In order to use trigonometry, imagine we split the blade down the middle of the spine…to get a pair of right angled triangles.

HALF the stock thickness is the “opposite” side.
Opposite:
.156 25 / 2
.078 125


Bevel width is the “adjacent” side
Adjacent:
1.000”
Tangent of an angle is the ratio of the length of the opposite side to the length of the adjacent side.

Tan = Opposite / Adjacent

180px-Trigonometry_triangle.svg.png

I ripped this photo from wiki - it's not scaled right for our example


.078 125 / 1
= .078 125

Inverse Tangent of .078 125
= 4.47 Degrees

For ONE side of the blade
Set platen 4.5 degrees off of perpendicular.

Total angle is about 9 Degrees.

Anyone else ??? if this is the correct formula, I can add 5/32 to the chart
 
Just my most humble opinion, and I mean no disrespect at all, and I realized a good while back that I am a dinosaur in this field when it comes to understanding the use of so many jigs, gauges, major machinery, and mathematical equations in order to turn out a hand-made knife, but I think, again, just my opinion, please don't take offense, that you have found the perfect solution, to a non existant problem. Carry on. Maybe one day I'll get it, but I really have my doubts on that.
 
Thanks for posting the chart. It looks like alot of good info. I'm not sure I understand the definition of '' bevel with'' though. Could someone please clarify?
 
By bevel width - i mean the width of the flat grind

On a full flat grind it's edge to spine.

or on less than full grind it's edge to grind line...
 
Steven Penner said:
I could have buggered something up – lets see.
Math is not my strongest skill

5/32 spine thickness and 1” bevel height

5/32 .156 25 is the spine thickness and the smallest side of an Isosceles triangle.

74px-Triangle.Isosceles.svg.png


In order to use trigonometry, imagine we split the blade down the middle of the spine…to get a pair of right angled triangles.

HALF the stock thickness is the “opposite” side.
Opposite:
.156 25 / 2
.078 125


Bevel width is the “adjacent” side
Adjacent:
1.000”
Tangent of an angle is the ratio of the length of the opposite side to the length of the adjacent side.

Tan = Opposite / Adjacent

180px-Trigonometry_triangle.svg.png

I ripped this photo from wiki - it's not scaled right for our example


.078 125 / 1
= .078 125

Inverse Tangent of .078 125
= 4.47 Degrees

For ONE side of the blade
Set platen 4.5 degrees off of perpendicular.

Total angle is about 9 Degrees.

Anyone else ??? if this is the correct formula, I can add 5/32 to the chart
Click to expand...

Hey Steven, Sorry for bringing up a dead post, but nobody answered your last question and I remembered you created this and wanted to reference it. I don't know about the trig, but the first four collums for a bevel width of 1" are in 1/32" increments at 0.9 degrees per 1/32." Assuming you are correct to that point, it looks like you nailed the 5/32" spine width. .9 * 5 = 4.5. Thanks for the chart.

EA
 
ERIK KNIVES said:
Hey Steven, Sorry for bringing up a dead post, but nobody answered your last question and I remembered you created this and wanted to reference it. I don't know about the trig, but the first four collums for a bevel width of 1" are in 1/32" increments at 0.9 degrees per 1/32." Assuming you are correct to that point, it looks like you nailed the 5/32" spine width. .9 * 5 = 4.5. Thanks for the chart.

EA
Click to expand...

I'm sorry, but some of you guys are just too funny to take seriously.
 
Erik, Steven hasn't posted in 4.5 years. I doubt he will answer you.

LRB was right in that this is an answer to a problem that isn't there..... it stiil is.

All bevel angles are less than the secondary edge angle, so just pick a height and thickness that fits the use. The actual angle is irrelevant.


Thread locked.
 
Status
Not open for further replies.
Back
Top