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  #41  
Old March 20th 18, 06:32 PM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default milling machine

John B. writes:

On Mon, 19 Mar 2018 22:43:37 -0700, Jeff Liebermann
wrote:

On Tue, 20 Mar 2018 10:59:44 +0700, John B.
wrote:

On Mon, 19 Mar 2018 19:48:03 -0700, Jeff Liebermann
wrote:


Incidentally, sharpening all my kitchen knives to an edge sharp enough
for shaving was NOT a good idea. I'm cutting myself quite often and
am slowly destroying my cutting boards and dishes. Paper plates no
longer work as my knives cut through the paper.


I don't do kitchen work but periodically my wife hands me a bunch of
kitchen knives and says "Sharpen them". Generally these are cheap
stainless knives and I've found that simply making a pass across a
grinding wheel on each side works pretty well. It produces a sharp
edge which is not perfectly smooth, more like a very fine tooth saw
which seems to cut better then a perfectly smooth blade.


Disclaimer: I am a beginner on knife making but am learning fast.

It depends one what and how you're using the knife to cut. If you
draw the knife as if you were sawing through the food, a rough edge is
quite superior to a razor sharp edge. However, if you're pushing your
way through the food with the knife, the razor edge works better.

What I did was buy about 15 assorted knives at a local outdoor flea
market and 10 more at a local thrift shop. I used these for practice
to learn how to sharpen them and how to modify the shape of the blade.
Most were stainless but I also found a few 1095 high carbon steel "Old
Hickory" knives.
https://www.knivesplus.com/OLD-HICKORY-KNIVES.HTML

I bought a Harbor Freight 1x30 belt sander and belt assortment from 80
grit to 800 grit:
https://www.harborfreight.com/power-tools/sanders/1-in-x-30-in-belt-sander-60543.html
an angle guide:
https://www.amazon.com/Knife-Sharpening-Angle-Guide-Sharpen/dp/B01HVXFP80
and a collection of whetstones:
https://www.ebay.com/itm/Japanese-Whetstone-Knife-Grit-1000-8000-Sharpener-Sharpening-Water-Stone-Stand/222660726466
I also setup a binocular microscope so I could see what I was doing to
the edge:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
After a few frustrating failures, I determined that I could produce a
usable but rough edge with the belt sander, and then refine it to a
razor sharp edge with the water stones. The sanding might only take a
few minutes on the belt sander, but the water stone polishing can
easily take hours. I can easily see the difference with the
microscope.

I have 6" grinder, but I would not use it to sharpen knives. It takes
off too much metal too quickly to maintain control. When I tried it,
the result was a rather "wavy" edge. Even a belt sander takes off too
much metal if you use a rough (80 or 120 grit) belt. If you have a
belt sander, try starting with 120 grit to remove the dings and chips.
Then use increasingly finer belts until you get to 400 or 800 grit.
You can probably just quit there, or if you want a smooth edge, use a
succession of water stones (1000 to 3000) to improve on the edge.


Somewhere around the Net is a site that talks about super sharp, or
deadly sharp, or some other fancy name. That guy used plain old emery
paper on a flat block to sharpen a knife.


Scary sharp.

I've tried it and it works pretty well except that if you move the
blade forward - leading with the sharp edge - it scrapes the abrasive
off the paper :-) But it does work pretty well if you pull the blade
"backward" with the sharp edge trailing. I usually have a couple pf
wood blocks with emery paper glued to one side laying around the
bench. If you are cutting something like glass cloth a couple of
swipes across the blocks every cut or so keeps a pretty good edge on
the knife.


I have not tried this with knives, but it works well on plane irons,
chisels, and such, moving forwards or backwards. The advantage is that
a wide variety of grits are easily available, and the surface stays as
flat as it started. I just use a granite floor "tile", which is flat
enough for my purposes.

The disadvantage is that abrasive paper costs considerably more than
sharpening stones if one sharpens a lot.

I made several "work knives" - sort of a substitute for a folding
pocket knife, after I broke mine - out of "All Hard" power hacksaw
blades. The edge holds up pretty well to abuse but doesn't "take an
edge" as well as say old files.

There is a Usenet group "rec.knives" that used to be pretty active but
I haven't been there for quite a while.


--
Ads
  #42  
Old March 20th 18, 06:33 PM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default milling machine

Frank Krygowski writes:

On 3/20/2018 2:25 AM, John B. wrote:
On Mon, 19 Mar 2018 22:43:37 -0700, Jeff Liebermann
wrote:

On Tue, 20 Mar 2018 10:59:44 +0700, John B.
wrote:

On Mon, 19 Mar 2018 19:48:03 -0700, Jeff Liebermann
wrote:

Incidentally, sharpening all my kitchen knives to an edge sharp enough
for shaving was NOT a good idea. I'm cutting myself quite often and
am slowly destroying my cutting boards and dishes. Paper plates no
longer work as my knives cut through the paper.

I don't do kitchen work but periodically my wife hands me a bunch of
kitchen knives and says "Sharpen them". Generally these are cheap
stainless knives and I've found that simply making a pass across a
grinding wheel on each side works pretty well. It produces a sharp
edge which is not perfectly smooth, more like a very fine tooth saw
which seems to cut better then a perfectly smooth blade.

Disclaimer: I am a beginner on knife making but am learning fast.

It depends one what and how you're using the knife to cut. If you
draw the knife as if you were sawing through the food, a rough edge is
quite superior to a razor sharp edge. However, if you're pushing your
way through the food with the knife, the razor edge works better.

What I did was buy about 15 assorted knives at a local outdoor flea
market and 10 more at a local thrift shop. I used these for practice
to learn how to sharpen them and how to modify the shape of the blade.
Most were stainless but I also found a few 1095 high carbon steel "Old
Hickory" knives.
https://www.knivesplus.com/OLD-HICKORY-KNIVES.HTML

I bought a Harbor Freight 1x30 belt sander and belt assortment from 80
grit to 800 grit:
https://www.harborfreight.com/power-tools/sanders/1-in-x-30-in-belt-sander-60543.html
an angle guide:
https://www.amazon.com/Knife-Sharpening-Angle-Guide-Sharpen/dp/B01HVXFP80
and a collection of whetstones:
https://www.ebay.com/itm/Japanese-Whetstone-Knife-Grit-1000-8000-Sharpener-Sharpening-Water-Stone-Stand/222660726466
I also setup a binocular microscope so I could see what I was doing to
the edge:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
After a few frustrating failures, I determined that I could produce a
usable but rough edge with the belt sander, and then refine it to a
razor sharp edge with the water stones. The sanding might only take a
few minutes on the belt sander, but the water stone polishing can
easily take hours. I can easily see the difference with the
microscope.

I have 6" grinder, but I would not use it to sharpen knives. It takes
off too much metal too quickly to maintain control. When I tried it,
the result was a rather "wavy" edge. Even a belt sander takes off too
much metal if you use a rough (80 or 120 grit) belt. If you have a
belt sander, try starting with 120 grit to remove the dings and chips.
Then use increasingly finer belts until you get to 400 or 800 grit.
You can probably just quit there, or if you want a smooth edge, use a
succession of water stones (1000 to 3000) to improve on the edge.


Somewhere around the Net is a site that talks about super sharp, or
deadly sharp, or some other fancy name. That guy used plain old emery
paper on a flat block to sharpen a knife.

I've tried it and it works pretty well except that if you move the
blade forward - leading with the sharp edge - it scrapes the abrasive
off the paper :-) But it does work pretty well if you pull the blade
"backward" with the sharp edge trailing. I usually have a couple pf
wood blocks with emery paper glued to one side laying around the
bench.


After trying many techniques over the decades, my favorite tool for
sharpening knives is a steel block whose top surface is impregnated
with industrial diamond abrasive. It seems to last forever, which for
practical purposes means it stays flat. I have other whetstones that
have gradually gotten concave, which makes it tough to maintain the
proper edge angles.


That diamond "stone", if it is wide enough, will flatten other
whetstones quite nicely. Although if you wait until the stones are
seriously dished it's not worth the effort.

I use the classic technique, which is sharpen the main bevel at
something like 20 degrees, then lightly sharpen a smaller bevel at 45
degrees, and touch up or polish the edge with a hone or other piece of
hard steel. I use the hone far more often than the abrasive. Lots of
times, the edge just needs touching up, not actual grinding.


--
  #43  
Old March 20th 18, 06:46 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default milling machine

On 3/20/2018 1:33 PM, Radey Shouman wrote:
Frank Krygowski writes:

On 3/20/2018 2:25 AM, John B. wrote:
On Mon, 19 Mar 2018 22:43:37 -0700, Jeff Liebermann
wrote:

On Tue, 20 Mar 2018 10:59:44 +0700, John B.
wrote:

On Mon, 19 Mar 2018 19:48:03 -0700, Jeff Liebermann
wrote:

Incidentally, sharpening all my kitchen knives to an edge sharp enough
for shaving was NOT a good idea. I'm cutting myself quite often and
am slowly destroying my cutting boards and dishes. Paper plates no
longer work as my knives cut through the paper.

I don't do kitchen work but periodically my wife hands me a bunch of
kitchen knives and says "Sharpen them". Generally these are cheap
stainless knives and I've found that simply making a pass across a
grinding wheel on each side works pretty well. It produces a sharp
edge which is not perfectly smooth, more like a very fine tooth saw
which seems to cut better then a perfectly smooth blade.

Disclaimer: I am a beginner on knife making but am learning fast.

It depends one what and how you're using the knife to cut. If you
draw the knife as if you were sawing through the food, a rough edge is
quite superior to a razor sharp edge. However, if you're pushing your
way through the food with the knife, the razor edge works better.

What I did was buy about 15 assorted knives at a local outdoor flea
market and 10 more at a local thrift shop. I used these for practice
to learn how to sharpen them and how to modify the shape of the blade.
Most were stainless but I also found a few 1095 high carbon steel "Old
Hickory" knives.
https://www.knivesplus.com/OLD-HICKORY-KNIVES.HTML

I bought a Harbor Freight 1x30 belt sander and belt assortment from 80
grit to 800 grit:
https://www.harborfreight.com/power-tools/sanders/1-in-x-30-in-belt-sander-60543.html
an angle guide:
https://www.amazon.com/Knife-Sharpening-Angle-Guide-Sharpen/dp/B01HVXFP80
and a collection of whetstones:
https://www.ebay.com/itm/Japanese-Whetstone-Knife-Grit-1000-8000-Sharpener-Sharpening-Water-Stone-Stand/222660726466
I also setup a binocular microscope so I could see what I was doing to
the edge:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
After a few frustrating failures, I determined that I could produce a
usable but rough edge with the belt sander, and then refine it to a
razor sharp edge with the water stones. The sanding might only take a
few minutes on the belt sander, but the water stone polishing can
easily take hours. I can easily see the difference with the
microscope.

I have 6" grinder, but I would not use it to sharpen knives. It takes
off too much metal too quickly to maintain control. When I tried it,
the result was a rather "wavy" edge. Even a belt sander takes off too
much metal if you use a rough (80 or 120 grit) belt. If you have a
belt sander, try starting with 120 grit to remove the dings and chips.
Then use increasingly finer belts until you get to 400 or 800 grit.
You can probably just quit there, or if you want a smooth edge, use a
succession of water stones (1000 to 3000) to improve on the edge.

Somewhere around the Net is a site that talks about super sharp, or
deadly sharp, or some other fancy name. That guy used plain old emery
paper on a flat block to sharpen a knife.

I've tried it and it works pretty well except that if you move the
blade forward - leading with the sharp edge - it scrapes the abrasive
off the paper :-) But it does work pretty well if you pull the blade
"backward" with the sharp edge trailing. I usually have a couple pf
wood blocks with emery paper glued to one side laying around the
bench.


After trying many techniques over the decades, my favorite tool for
sharpening knives is a steel block whose top surface is impregnated
with industrial diamond abrasive. It seems to last forever, which for
practical purposes means it stays flat. I have other whetstones that
have gradually gotten concave, which makes it tough to maintain the
proper edge angles.


That diamond "stone", if it is wide enough, will flatten other
whetstones quite nicely. Although if you wait until the stones are
seriously dished it's not worth the effort.


I had a nice Arkansas stone that broke before it went concave, sadly.

My next best stone was a large one (maybe 2" x 6") given to me by the
machinist who lived next door. But it was concave to begin with, and
it's very concave now. I suppose I should find a way to flatten it. It's
too big for my little diamond stone. Any advice?

--
- Frank Krygowski
  #44  
Old March 20th 18, 08:59 PM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default milling machine

Frank Krygowski writes:

On 3/20/2018 1:33 PM, Radey Shouman wrote:
Frank Krygowski writes:

On 3/20/2018 2:25 AM, John B. wrote:
On Mon, 19 Mar 2018 22:43:37 -0700, Jeff Liebermann
wrote:

On Tue, 20 Mar 2018 10:59:44 +0700, John B.
wrote:

On Mon, 19 Mar 2018 19:48:03 -0700, Jeff Liebermann
wrote:

Incidentally, sharpening all my kitchen knives to an edge sharp enough
for shaving was NOT a good idea. I'm cutting myself quite often and
am slowly destroying my cutting boards and dishes. Paper plates no
longer work as my knives cut through the paper.

I don't do kitchen work but periodically my wife hands me a bunch of
kitchen knives and says "Sharpen them". Generally these are cheap
stainless knives and I've found that simply making a pass across a
grinding wheel on each side works pretty well. It produces a sharp
edge which is not perfectly smooth, more like a very fine tooth saw
which seems to cut better then a perfectly smooth blade.

Disclaimer: I am a beginner on knife making but am learning fast.

It depends one what and how you're using the knife to cut. If you
draw the knife as if you were sawing through the food, a rough edge is
quite superior to a razor sharp edge. However, if you're pushing your
way through the food with the knife, the razor edge works better.

What I did was buy about 15 assorted knives at a local outdoor flea
market and 10 more at a local thrift shop. I used these for practice
to learn how to sharpen them and how to modify the shape of the blade.
Most were stainless but I also found a few 1095 high carbon steel "Old
Hickory" knives.
https://www.knivesplus.com/OLD-HICKORY-KNIVES.HTML

I bought a Harbor Freight 1x30 belt sander and belt assortment from 80
grit to 800 grit:
https://www.harborfreight.com/power-tools/sanders/1-in-x-30-in-belt-sander-60543.html
an angle guide:
https://www.amazon.com/Knife-Sharpening-Angle-Guide-Sharpen/dp/B01HVXFP80
and a collection of whetstones:
https://www.ebay.com/itm/Japanese-Whetstone-Knife-Grit-1000-8000-Sharpener-Sharpening-Water-Stone-Stand/222660726466
I also setup a binocular microscope so I could see what I was doing to
the edge:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
After a few frustrating failures, I determined that I could produce a
usable but rough edge with the belt sander, and then refine it to a
razor sharp edge with the water stones. The sanding might only take a
few minutes on the belt sander, but the water stone polishing can
easily take hours. I can easily see the difference with the
microscope.

I have 6" grinder, but I would not use it to sharpen knives. It takes
off too much metal too quickly to maintain control. When I tried it,
the result was a rather "wavy" edge. Even a belt sander takes off too
much metal if you use a rough (80 or 120 grit) belt. If you have a
belt sander, try starting with 120 grit to remove the dings and chips.
Then use increasingly finer belts until you get to 400 or 800 grit.
You can probably just quit there, or if you want a smooth edge, use a
succession of water stones (1000 to 3000) to improve on the edge.

Somewhere around the Net is a site that talks about super sharp, or
deadly sharp, or some other fancy name. That guy used plain old emery
paper on a flat block to sharpen a knife.

I've tried it and it works pretty well except that if you move the
blade forward - leading with the sharp edge - it scrapes the abrasive
off the paper :-) But it does work pretty well if you pull the blade
"backward" with the sharp edge trailing. I usually have a couple pf
wood blocks with emery paper glued to one side laying around the
bench.

After trying many techniques over the decades, my favorite tool for
sharpening knives is a steel block whose top surface is impregnated
with industrial diamond abrasive. It seems to last forever, which for
practical purposes means it stays flat. I have other whetstones that
have gradually gotten concave, which makes it tough to maintain the
proper edge angles.


That diamond "stone", if it is wide enough, will flatten other
whetstones quite nicely. Although if you wait until the stones are
seriously dished it's not worth the effort.


I had a nice Arkansas stone that broke before it went concave, sadly.

My next best stone was a large one (maybe 2" x 6") given to me by the
machinist who lived next door. But it was concave to begin with, and
it's very concave now. I suppose I should find a way to flatten
it. It's too big for my little diamond stone. Any advice?


I have seen a flat surface and sandpaper advised, but haven't tried it.
Diamond lapping plates up to 4" wide are easily available, albeit not
cheaply. Norton and others sell flattening stones intended for
waterstones, but I would bet they work fine with Arkansas or other
oilstones.


--
  #45  
Old March 20th 18, 11:54 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default milling machine

On Tue, 20 Mar 2018 12:25:58 -0400, Frank Krygowski
wrote:

After trying many techniques over the decades, my favorite tool for
sharpening knives is a steel block whose top surface is impregnated with
industrial diamond abrasive. It seems to last forever, which for
practical purposes means it stays flat.


If it's this type, that has the diamonds imbedded in a sheet of
plastic, they are probably NOT flat.
https://www.harborfreight.com/3-piece-2-inch-x-6-inch-diamond-hone-blocks-36799.html
If it's a far more expensive diamond plate with mono crystalline
diamonds and where the diamonds are embedded in a more stable
substrate, they work very well:
https://www.dmtsharp.com/sharpeners/bench-stones/dia-sharp/
The problem is that the grain size of the diamonds is rather small. In
order for them to remain in place, about two thirds of the diameter
needs to be imbedded in the plastic, aluminum, or whatever. That
leaves very little sticking out to do the cutting. If the substrate
is bent a little less than the height of the diamonds, you'll be
sharpening on air, not diamonds.

This video covers the problems quite well:
"WATCH THIS before you buy diamond stones for tool/knife sharpening"
https://www.youtube.com/watch?v=zBND6emsSE4

I have other whetstones that
have gradually gotten concave, which makes it tough to maintain the
proper edge angles.


Stones are easy to flatten. Take a soft pencil and mark a grid on the
stone surface. Find another stone with a rougher grit and rub the two
surfaces together. The pencil markings will disappear as you grind
from the high spots. Keep grinding until all of the penciled grid
disappears simultaneously.

I use the classic technique, which is sharpen the main bevel at
something like 20 degrees, then lightly sharpen a smaller bevel at 45
degrees, and touch up or polish the edge with a hone or other piece of
hard steel.


I use 15 to 20 degrees for kitchen knives depending on blade
thickness. Mostly, I try to duplicate the original angle from the
manufacturer. I haven't tried any compound angle grinds yet.
http://blissknifeworks.com/wp-content/uploads/2016/10/Grind-Angle-Chart-copy.jpg

I use the hone far more often than the abrasive. Lots of
times, the edge just needs touching up, not actual grinding.


I look at the edge with a magnifier or microscope to see what I'm
dealing with. If it's dings, gouges, or chips, I use the belt sander
to remove these before sharpening. If it's just a little rough, then
I use a finer stone.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #46  
Old March 21st 18, 06:07 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default milling machine

On Tue, 20 Mar 2018 14:55:32 +0100, Emanuel Berg
wrote:

AMuzi wrote:

http://www.yellowjersey.org/gth8.jpg


Right, but are the tubes typically that thin?
If so I see the point.



High end tubes are typically less then 1mm wall thickness. A Columbus
"Spirit" top tube is 0.38mm ( wall thickness ) and is butted on each
end to 0.5mm.
--
Cheers,

John B.

  #47  
Old March 21st 18, 06:11 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default milling machine

On Tue, 20 Mar 2018 15:09:49 +0100, Emanuel Berg
wrote:

AMuzi wrote:

http://www.yellowjersey.org/gth8.jpg


Also, how does one know how much to file away?
Like if you have one tube that has diameter A,
and another has diameter B, and A B, and you
want the second tube to be at an angle X from
the first?


There are quite a number of simple computer programs that given the
diameter and wall thickness and the angles the tubes are joined will
print out a template that you can use to mark the tube.

I use Tubemiter.exe that dates back to DOS days :-)



If we return to the lathe guys they have
a small thing with rods that can be pushed back
and forth to form a pattern, perhaps something
like that can be used to do a template if it is
difficult to compute?

--
Cheers,

John B.

  #48  
Old March 21st 18, 06:14 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default milling machine

On Tue, 20 Mar 2018 15:36:07 +0100, Emanuel Berg
wrote:

Jeff Liebermann wrote:

I don't know if a drill press will work,
probably not.


What's the problem with a drill press? If the
tubes are as thin as in AMuzi's photo, I don't
see power being a problem assuming the tubes
can be fixed robustly which one has to do
anyway with a milling machine?


"Hole Saws" are often used to miter tubes and yes, you could use a
drill press assuming that you have some sort of fixture to hold the
tube.
--
Cheers,

John B.

  #49  
Old March 21st 18, 06:14 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default milling machine

On Tue, 20 Mar 2018 17:07:17 +0100, Emanuel Berg
wrote:

AMuzi wrote:

1.0mm for heavy touring tube, mostly 0.9 and
0.8 tube in my repair photos. The latest air
hardening tubes are drawn as thin as 0.3mm.


?

I have an aluminium frame here which is 2.065kg
and the head tube is 3.7mm and the saddle tube
is 2.35mm!



And Andrew was talking about steel frames...
--
Cheers,

John B.

  #50  
Old March 21st 18, 06:24 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default milling machine

On Tue, 20 Mar 2018 12:25:58 -0400, Frank Krygowski
wrote:

On 3/20/2018 2:25 AM, John B. wrote:
On Mon, 19 Mar 2018 22:43:37 -0700, Jeff Liebermann
wrote:

On Tue, 20 Mar 2018 10:59:44 +0700, John B.
wrote:

On Mon, 19 Mar 2018 19:48:03 -0700, Jeff Liebermann
wrote:

Incidentally, sharpening all my kitchen knives to an edge sharp enough
for shaving was NOT a good idea. I'm cutting myself quite often and
am slowly destroying my cutting boards and dishes. Paper plates no
longer work as my knives cut through the paper.

I don't do kitchen work but periodically my wife hands me a bunch of
kitchen knives and says "Sharpen them". Generally these are cheap
stainless knives and I've found that simply making a pass across a
grinding wheel on each side works pretty well. It produces a sharp
edge which is not perfectly smooth, more like a very fine tooth saw
which seems to cut better then a perfectly smooth blade.

Disclaimer: I am a beginner on knife making but am learning fast.

It depends one what and how you're using the knife to cut. If you
draw the knife as if you were sawing through the food, a rough edge is
quite superior to a razor sharp edge. However, if you're pushing your
way through the food with the knife, the razor edge works better.

What I did was buy about 15 assorted knives at a local outdoor flea
market and 10 more at a local thrift shop. I used these for practice
to learn how to sharpen them and how to modify the shape of the blade.
Most were stainless but I also found a few 1095 high carbon steel "Old
Hickory" knives.
https://www.knivesplus.com/OLD-HICKORY-KNIVES.HTML

I bought a Harbor Freight 1x30 belt sander and belt assortment from 80
grit to 800 grit:
https://www.harborfreight.com/power-tools/sanders/1-in-x-30-in-belt-sander-60543.html
an angle guide:
https://www.amazon.com/Knife-Sharpening-Angle-Guide-Sharpen/dp/B01HVXFP80
and a collection of whetstones:
https://www.ebay.com/itm/Japanese-Whetstone-Knife-Grit-1000-8000-Sharpener-Sharpening-Water-Stone-Stand/222660726466
I also setup a binocular microscope so I could see what I was doing to
the edge:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
After a few frustrating failures, I determined that I could produce a
usable but rough edge with the belt sander, and then refine it to a
razor sharp edge with the water stones. The sanding might only take a
few minutes on the belt sander, but the water stone polishing can
easily take hours. I can easily see the difference with the
microscope.

I have 6" grinder, but I would not use it to sharpen knives. It takes
off too much metal too quickly to maintain control. When I tried it,
the result was a rather "wavy" edge. Even a belt sander takes off too
much metal if you use a rough (80 or 120 grit) belt. If you have a
belt sander, try starting with 120 grit to remove the dings and chips.
Then use increasingly finer belts until you get to 400 or 800 grit.
You can probably just quit there, or if you want a smooth edge, use a
succession of water stones (1000 to 3000) to improve on the edge.


Somewhere around the Net is a site that talks about super sharp, or
deadly sharp, or some other fancy name. That guy used plain old emery
paper on a flat block to sharpen a knife.

I've tried it and it works pretty well except that if you move the
blade forward - leading with the sharp edge - it scrapes the abrasive
off the paper :-) But it does work pretty well if you pull the blade
"backward" with the sharp edge trailing. I usually have a couple pf
wood blocks with emery paper glued to one side laying around the
bench.


After trying many techniques over the decades, my favorite tool for
sharpening knives is a steel block whose top surface is impregnated with
industrial diamond abrasive. It seems to last forever, which for
practical purposes means it stays flat. I have other whetstones that
have gradually gotten concave, which makes it tough to maintain the
proper edge angles.

I use the classic technique, which is sharpen the main bevel at
something like 20 degrees, then lightly sharpen a smaller bevel at 45
degrees, and touch up or polish the edge with a hone or other piece of
hard steel. I use the hone far more often than the abrasive. Lots of
times, the edge just needs touching up, not actual grinding.


But the emery paper and wooden block are so cheap :-)

The various angles required to arrive at a cutting edge are very
dependent on the use to which the cutting device is to be put.
--
Cheers,

John B.

 




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