Polishing the edge with lapping film

[buzzy]

Once the bevel is set (I'm using a DMT 1200) and I start to polish the blade with 12um film, how do I know when it's time to change for a finer grit? I have 12um, 5um, 3um and 1um.


Is the cutting edge supposed to be like a mirror (no scratches at all) when I'm done?


I'm having a hard time differentiating the scratches from 12um and 5um...

Thanks!

 

[Wid]

I go from 1K to 5um, no 12um. Using a loupe it's not all that hard to tell the difference.

Yes, when you're done the bevel should have a mirror look.

 

[buzzy]

I go from 1K to 5um, no 12um. Using a loupe it's not all that hard to tell the difference.

Yes, when you're done the bevel should have a mirror look.

Well, I tried to hone a razor yesterday and I couldn't tell the difference

Maybe the DMT leaves scratches that are too deep and I need to spend more time with higher grits. Is it normal if it takes more than 20 minutes to remove them?

 

[global_dev]

Well, I tried to hone a razor yesterday and I couldn't tell the difference

Maybe the DMT leaves scratches that are too deep and I need to spend more time with higher grits. Is it normal if it takes more than 20 minutes to remove them?

i would think you would need to spend more time on the relatively lower grits, not higher. are you positive the bevel was set?

 

[buzzy]

i would think you would need to spend more time on the relatively lower grits, not higher. are you positive the bevel was set?

Yes, I'm sure the bevel was set. I got a good shave with the straight this morning but the bevel wasn't exactly what I would call a mirror.

What I meant was maybe I need to spend more time on the 5um to remove the scratches left by the DMT. I had the impression that this could be done relatively quickly but it seems I need to spend more time at this stage...

 

[Wid]

How are you determining when to move on to the next film?

 

[buzzy]

How are you determining when to move on to the next film?

Did you notice you are asking me the same question I asked in my original post

Right now, my answer would be : I don't know for sure, so I just take a guess.
Not a good answer because I can't get a mirror finish.

Do you have a better answer that could put me out of my misery?

Thanks a lot!

 

[BDF]

If you use the same blade angle (the angle of the blade relative to the direction it is moving across the film or stone) for each grit but change the angle when changing grit size, you will be able to see any remaining scratches left by the previous grit size. That may not make much sense but for example: say you set the bevel with 1K grit size (stone, film, lapping paste, whatever), and make the last five laps with the blade facing directly forward and no X strokes. Now all the honing marks in the blade edge are in-line with the blade; when you change to, say, 5 micron film, make five strokes with the toe of the razor leading the heel by something like 20 degrees and again, no X strokes. Look at the edge of the bevel and you will clearly see if there are any 1K scratch lines left because they were straight from bevel to spine while you new, finer scratch lines are all at a 20 degree or so angle. Keep honing on that grit size until there are no more lines left anywhere on the bevel that are straight across the razor- that means you have removed all the lines from the 1K honing step. Then move to the next finer grade of film and either go back to holding the razor square to the direction of movement and hone until all the 20 degree scratches are gone and you will know you are finished with that grade of film also. The particular angles used for each grit do not matter, only that the last set of laps on each grit are all in one direction so that any previous scratches stand out because they are in a different direction. You also do not have to do all the laps on a given grit the same way, only the last handful (say 5 laps or so) so that the only pattern left by the current grit you are using are all in the same direction, and that direction is noticeably different than the direction used on the previous grit.

Brian

Do you have a better answer that could put me out of my misery?

Thanks a lot!

 

[buzzy]

If you use the same blade angle (the angle of the blade relative to the direction it is moving across the film or stone) for each grit but change the angle when changing grit size, you will be able to see any remaining scratches left by the previous grit size. That may not make much sense but for example: say you set the bevel with 1K grit size (stone, film, lapping paste, whatever), and make the last five laps with the blade facing directly forward and no X strokes. Now all the honing marks in the blade edge are in-line with the blade; when you change to, say, 5 micron film, make five strokes with the toe of the razor leading the heel by something like 20 degrees and again, no X strokes. Look at the edge of the bevel and you will clearly see if there are any 1K scratch lines left because they were straight from bevel to spine while you new, finer scratch lines are all at a 20 degree or so angle. Keep honing on that grit size until there are no more lines left anywhere on the bevel that are straight across the razor- that means you have removed all the lines from the 1K honing step. Then move to the next finer grade of film and either go back to holding the razor square to the direction of movement and hone until all the 20 degree scratches are gone and you will know you are finished with that grade of film also. The particular angles used for each grit do not matter, only that the last set of laps on each grit are all in one direction so that any previous scratches stand out because they are in a different direction. You also do not have to do all the laps on a given grit the same way, only the last handful (say 5 laps or so) so that the only pattern left by the current grit you are using are all in the same direction, and that direction is noticeably different than the direction used on the previous grit.

Brian

That makes a lot of sense. I just tried that and I could still see some scratches.

I did a test with a junk blade that has large hone wear. I did several laps with my DMT1200 and could clearly see the scratches on the spine. I tried to remove them with 5um film, holding the film in my hand and squeezing the spine like I would do with
sandpaper and no matter how hard I tried the scratches stayed there. I tried the same thing with 1500 grit sandpaper, then 1000, then 800, then 600!. With 600 I finally managed to remove the scratches in a timely manner.

I did the same tests with a DMT600 and I needed 320 grits sandpaper to remove all the scratches.

It seems my DMTs leaves some deep scratches!

Any suggestions? I'm not sure I want to start honing on sandpaper...

 

[Wid]

Try and break in the DMT with a butter knife, chisel or some other metal. Once broken in it shouldn't leave such deep marks.

 

[Doc226]

It really should not take 20 minutes on any portion of the honing to remove the previous stones scratches.

I look at the fluid wave being undercut and go by the feel of the razor on the stone or the film

I woudl say that "most" of the time 40-50 laps should be sufficient-of course it may take more it might take less.

I loupe helps a lot.

 

[buzzy]

Try and break in the DMT with a butter knife, chisel or some other metal. Once broken in it shouldn't leave such deep marks.

How long does it take to break in? I used it for more than one hour for sure (just added about 20 minutes) and there is no way for me to remove the scratches without sandpaper (at least 600 grits).

Kinda discouraging...

 

[Wid]

It can take a bit, just keep at it.

 

[Seraphim]

Go out to your garage to the tool box and grab a chisel.

TAke that chisel and rub the big wide flat back of the chisel back and forth rapidly on your DMT plate. Water on there is a good idea. Do that for a couple of minutes, you should be able to see a change in the scratch pattern on the chisel.

Put the chisel away and go hone some razors!

 

[joser]

It really should not take 20 minutes on any portion of the honing to remove the previous stones scratches.

I look at the fluid wave being undercut and go by the feel of the razor on the stone or the film

I woudl say that "most" of the time 40-50 laps should be sufficient-of course it may take more it might take less.

I loupe helps a lot.

Doc-

Would you please elaborate on the bolded line above?

Thanks!

 

[Wid]

I'm not Doc obviously but it's when the water rides up over the edge.

 

[BDF]

It is going to take a long time to get the 'lumps' off the DMT hone by using it on straight razors. There just isn't enough force generated in honing a razor to knock off the high spots of diamond clumps. As Seraphim said, use something like a chisel or even a thick putty knife to really put some pressure against the hone to knock off the little clumps of diamond that are sticking up when the hone is new. Those deep scratches left from a new DMT hone are much larger than the actual grit rating of the honing plate itself (more like 200 grit spots here and there on a new 1200 grit hone). Also, hitting those high spots with the leading edge of a straight razor is likely to chip the razor and be very counterproductive in establishing the bevel. That won't happen with a chisel or similar tool.

Brian

How long does it take to break in? I used it for more than one hour for sure (just added about 20 minutes) and there is no way for me to remove the scratches without sandpaper (at least 600 grits).

Kinda discouraging...

 

[buzzy]

Go out to your garage to the tool box and grab a chisel.

TAke that chisel and rub the big wide flat back of the chisel back and forth rapidly on your DMT plate. Water on there is a good idea. Do that for a couple of minutes, you should be able to see a change in the scratch pattern on the chisel.

Put the chisel away and go hone some razors!

It seems the back of my 1" chisel isn't that flat... I get no scratches in the middle section, only near the tip and near the base. I even did a sharpie test to confirm that.

 

[BDF]

Great- you can kill two birds with one stone (hone?): by the time your new hone is broken in your chisel should be flat. Sorta' like the Yin Yang thing.

Grind the chisel on the hone until the hone leaves an even finish without any obviously deep scratch marks. The diamond grit used on a DMT hone is extremely consistent but it can clump a bit when the steel plate is plated with the nickel / diamond. You want to knock off all of those clumps off so the entire hone face is a consistent grit. You should also notice it getting smoother and less aggressive pretty quickly while pushing the chisel across the surface.

Once you are using it for a while it will tend to clog with steel swarf from the razor(s). The hone will get less and less effective, and you will notice a light tan color on the surface of the hone. Cleaning it under running water with abrasive cleaner works wonders in restoring the hone to a good cutting surface again. I use Comet with a sponge and it cleans right up- you will see the surface of the hone become bright and silver while you are cleaning it. The Comet (or similar) will not hurt the diamond surface so I don't think you can really overdo it but the hone always works much better for me after I clean it.

Brian

It seems the back of my 1" chisel isn't that flat... I get no scratches in the middle section, only near the tip and near the base. I even did a sharpie test to confirm that.

 

[BDF]

Another thought but you might want to try using more of the edge of the chisel rather than the flat face. You are going to want to try to knock the clumps off the hone surface and an edge will do that better than a flat surface. You won't have to lift the chisel off the face, just try to put most of the pressure against the cutting edge rather than across the entire flat surface.

Brian

It seems the back of my 1" chisel isn't that flat... I get no scratches in the middle section, only near the tip and near the base. I even did a sharpie test to confirm that.