DMTs & does anyone have a micrometer?

Hope that piqued everyone's interest.

There was a Norton 4000/8000 lapping question recently where Randydance mentioned that he checked a newb's DMT 325 grit with a straightedge and the plate was NOT flat. That got me thinking in a concerned way since I have a DMT 325 & a new 1200. I took both to a pal's machine shop and we laid them both on a grade A pink granite surface plate.

Long story short, both the 325 & 1200 were about .001" off. The 1200 was .001 higher in the center (convex) and the 325 seemed to have a .001 slope upward.

It's been said that .001" or less will not affect honing a razor's edge. It's also been said, and fervently believed by many on SRP that taping a spine, for bevel setting, etc then removing the tape for polishing is a bad bad idea since the removal of the tape lifts the edge off the hone by the width of the tape which is enough to prevent polishing of the edge thereby accomplishing little (think of the tape as a shim. Removing the shim lowers the spine but raises the edge OFF the hone).

So........How thick is a piece of black electrical tape? How thick is scotch tape? If the thickness of tape can interfere with the overall honing process (unless the tape is kept on the spine from start to finish), is a tape's thickness dramatically far off from .001"??? I wonder. I have no micrometer to check, but maybe one of us does?

Why do I bring this up? What do I want to find out? I want to know if in fact .001" variance from flat will have absolutely no effect on honing a razor (this assumes the razor is flat). Maybe I'm making a mountain out of a mole hill, but I'd like to know.:shrug:

No need for a micrometer, 3m specs theirs. The Scotch® Super 33+ Vinyl Electrical Tape is 7mil or 0.007" thick.

As for the DMT plates, I'm pretty sure the spec on those is within 0.001" of total flatness. If you are really really concerned about flatness, you might as well spring for a Shapton Reference Plate, either the glass or cast iron based diamond one... either way you're looking at a significantly higher price.:eek:


Regards

Christian

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Originally Posted by Chrisl

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So........How thick is a piece of black electrical tape? How thick is scotch tape? If the thickness of tape can interfere with the overall honing process (unless the tape is kept on the spine from start to finish), is a tape's thickness dramatically far off from .001"??? I wonder. I have no micrometer to check, but maybe one of us does?

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My black tape mikes out to right around 0.007".

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Why do I bring this up? What do I want to find out? I want to know if in fact .001" variance from flat will have absolutely no effect on honing a razor (this assumes the razor is flat). Maybe I'm making a mountain out of a mole hill, but I'd like to know.:shrug:

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Removing 0.007" of tape from the spine will change edge angle (per side) by about 0.5348 degrees on a 6/8 blade and about 0.4584 degrees with a 7/8 razor.
EDIT: Half a degree on a 7 to 8 degree bevel is quite a change when sharpening.

So a 0.001" change from edge to center of a 8" DMT is an angular change of about 0.014 degree. Fourteen thousandths of a degree variance is plenty good enough for razors (IMO).:D I know, TMI...

My DMT plates are all perfectly flat as indicated by my machinist straight edge. You can easily see the effect of honing a razor with tape. Just set the bevel with tape on the razor then color the bevel with a permanent marker. If you take the tape off and hone the razor you will find that it will take a significant amount of work to remove the marker all the way to the edge unless you torque the edge into the stone/plate.

Well, I build pipes in my spare time, so I just happened to have a digital micrometer laying about...a piece of electrical tape that I use for...well...electrical stuff comes in at 0.0065 of an inch (measured in three places, all came out the same). Just thought I'd confirm the 3M data.

Mark

That does not sound like much of a variance on the DMT. I would not be concerned.
The one I used made really bad grooves in the hone, not little ones but really big, wide ones.
I am sure it was a fluke. Many people here are using them and none have reported a problem.

I just checked the DMT website and indeed, I was correct on the flatness claims:

Here's a quote regarding the D8 series (8 x 3)

"The precision-engineered surface flatness to + / -0.001” will remain flat forever, offering the sharpest edges with no maintenance."

and in reference to the coarsest stone:

"With a surface flatness to +/- 0.001" Double-X is perfect for flattening water stones, Arkansas stones, and synthetic stones."


Now, considering that +/- 0.001" over 8 inches is pretty much the standard for basic machinists squares, it will have no discernible impact on razors or flattening hones. There is of course always the chance that a defective hone might get out and if so I would expect DMT to make it right. Personally, I think the D8 series is one heck of a bargain.

Regards

Christian

Another difference is that the tape affects the angle of the razor in a consistent way, while a slight variance in the hone will probably be gradual enough that the razor can adjust to it as you hone. A good X pattern stroke should compensate for some slight unevenness. My Belgian blue hone is way off flat when checked against a straight edge, but it works fine with razors of all sizes and shapes. :)

Josh

Well, if the consensus then is that .001" variance has no effect on adversely affecting a razors edge during honing, I'll live with that and chalk up my tribulations to my inexperience rather than being able to blame my lackluster results on the plates and hones;)

SRP member Sticky had mentioned in an recent post that the average thickness of a pencil mark is four billionths of an inch. With that in mind, aside from seeing where a hone is "out of the box", I see no need whatsoever to go through the trouble of ever doing a pencil grid for re-lapping a hone after the initial lapping. Why even bother taking the time to remove 4 billionths of an inch if a .001 variance has no ill effect? I ask this rhetorical question because I've used the pencil grid when re-lapping hones in the past. I'll do nothing more than some brief refresher passes on the diamond plates to clean the surfaces of my Norton 4000/8000 more than anything else and call it plenty good enough.

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Originally Posted by Chrisl

SRP member Sticky had mentioned in an recent post that the average thickness of a pencil mark is four billionths of an inch. With that in mind, aside from seeing where a hone is "out of the box", I see no need whatsoever to go through the trouble of ever doing a pencil grid for re-lapping a hone after the initial lapping. Why even bother taking the time to remove 4 billionths of an inch if a .001 variance has no ill effect? I ask this rhetorical question because I've used the pencil grid when re-lapping hones in the past. I'll do nothing more than some brief refresher passes on the diamond plates to clean the surfaces of my Norton 4000/8000 more than anything else and call it plenty good enough.

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The pencil mark was somewhere between 4 to 17 billionths as measured electronically with a Wheatstone Bridge. Geometric analysis agreed with the Bridge.

The rational behind drawing a second grid and re-lapping is because the first lapping will introduce errors (much larger than 4 billionths), from the operator, the initial unevenness of the hone, and the DMT plate. The worse your hone is at first, the bigger the introduced errors. If your hone starts out pretty flat, then the errors will likely be small. Many times small enough to be fine for razor use (depending on the operator's skill at lapping).

I only re-mark and lap twice under 3 conditions:

• This is the first time I am lapping this particular hone. OR-
• Using a 6" machinists rule, before beginning to lap (new or previously lapped-by-me): I see more than about 0.006" or 0.007" of daylight, at any point, between the rule and hone.
• I have the slightest suspicion/feeling that I might need to...

The only way a lapping job could be w/in 4-17 billionths of an inch is if all of your grid marks disappeared equally and at the same time. This will be impossible on a DMT plate because the DMT is not that accurate. All of us operators are even worse...:eek:

I think the pencil grid is just for reference to the flatness of the hone you'e lapping. If the pencil wears away only on the edges with a few laps, then you know the stone was way off from being flat. I heard someone (probably Josh) also say that once they have lapped completely flat the first time, they re-do the grid and give a couple laps. That's all it should take to erase the pencil and you will know it is flat.

Also, I know nothing about micrometers, but isn't it possible that with ANY machined product, even digital, there could be a variance in its measurement? i.e. 0 to a micrometer that may be off could really be 0.0001 or something so that over a large measure, the number will be slightly off, if only by maybe .001"?

On a new hone I would always lap twice. On a hone that I have used for several razors then I would lap twice, maybe.
I always lightly lap my hones on 1000 grit before each honing session so the amount of wear on my hones is never very much.

"Sticky" has a very relevant work backround and consequent insight to the subject of flatness and how it is, and is not, obtained. I will be paying close attention to his comments.

For those of you who believe that 0.001" is too much, I just hopped over to the Shapton site and checked the specs on the two Diamond Reference Plates they offer.

The Diamond Glass reference plate is accurate to 5 micron or 0.0001968498" and sells for a quite reasonable $289.00. But, you say... you want MORE... err LESS.... Ok, enter the big gun in Diamond Reference plates, the two sided, cast iron model which is accurate to an incredible 3.5 microns... that's 0.0001377949" for you non-metric types and it goes for a paltry $489.00. :D The two sides, one for lapping stones and the other for lapping bevels on plane irons and chisels etc. and would not be suitable for razors based on it's pattern with rather large holes to swallow up swarf etc.

So in a sense, you would have to spend at least $234.00 more to gain approximately 0.0008" in accuracy across an 8" length over a DMT.

Many of us have been quite happy using nothing more than wet/dry paper on a floor tile or a piece of reasonable (we're assuming now) flat glass. I doubt they approch anything near the 0.001" that DMT specs for their diamond plates. Lets not forget that 50 years ago, when straight shaving was more the norm... few if any gents went to these lengths to get their hones flat... I recall my dads hones ( he was a barber and was quite skilled with the straight), they were all clearly hollowed in the center from years and years of use... I suspect they all matched up more or less as he didn't seem to have any problems getting business in his shop for shaves nor haircuts.

I'm all for these kinds of discussions but sometimes we need to do a reality check to keep us in the real world. Well... at least I need to... I'm usually the first one to buy something new and improved only to find out that the old stuff worked just as well.

Regards

Christian

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Originally Posted by kaptain_zero

For those of you who believe that 0.001" is too much, I just hopped over to the Shapton site and checked the specs on the two Diamond Reference Plates they offer.

The Diamond Glass reference plate is accurate to 5 micron or 0.0001968498" and sells for a quite reasonable $289.00. But, you say... you want MORE... err LESS.... Ok, enter the big gun in Diamond Reference plates, the two sided, cast iron model which is accurate to an incredible 3.5 microns... that's 0.0001377949" for you non-metric types and it goes for a paltry $489.00. :D The two sides, one for lapping stones and the other for lapping bevels on plane irons and chisels etc. and would not be suitable for razors based on it's pattern with rather large holes to swallow up swarf etc.

So in a sense, you would have to spend at least $234.00 more to gain approximately 0.0008" in accuracy across an 8" length over a DMT.

Many of us have been quite happy using nothing more than wet/dry paper on a floor tile or a piece of reasonable (we're assuming now) flat glass. I doubt they approch anything near the 0.001" that DMT specs for their diamond plates. Lets not forget that 50 years ago, when straight shaving was more the norm... few if any gents went to these lengths to get their hones flat... I recall my dads hones ( he was a barber and was quite skilled with the straight), they were all clearly hollowed in the center from years and years of use... I suspect they all matched up more or less as he didn't seem to have any problems getting business in his shop for shaves nor haircuts.

I'm all for these kinds of discussions but sometimes we need to do a reality check to keep us in the real world. Well... at least I need to... I'm usually the first one to buy something new and improved only to find out that the old stuff worked just as well.

Regards

Christian

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Excellent comments. I have long suspected that back in the day, hones were seldom or never flattened and yet they worked just fine. Barber hones are hard enough that I can't imagine anyone would be able to flatten them without the benefit of 21st century equipment. Out of the box they aren't really flat, and unless you have an extra extra coarse diamond hone, those hones are a real beast to lap.

Glad to get some confirmation on my theory. :)

And I agree that we can go waaaaaaay overboard here. I think the unavoidable variations in the operator's stroke--human error--play a much bigger role than the hone's flatness to within a few thousandths of an inch.

Josh

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Originally Posted by heavydutysg135

My DMT plates are all perfectly flat as indicated by my machinist straight edge.

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Nothing is perfectly flat. I am reasonably sure that your DMTs have more than 0.00000000001 " error to them.

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Originally Posted by JoshEarl

Excellent comments. I have long suspected that back in the day, hones were seldom or never flattened and yet they worked just fine.

Josh

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Here's the "rub" so to speak on both of these posts...
I unfortunatly totatly agree with them, "back in the day" I do believe that people got perfefctly accapetable shaves from barbers hones and concaved Eshers and such, heck we see the proof....
Here is the one point I would bring up, How many razors have you passed up buying because the hone wear was way out of line, huge smiles, huge frowns, or worse a 3/8 toe with a 6/8 heel. I am of the belief that all these things are related.....FWIW

The great joy of having flat hones is that you can go from one hone to another without being forced to re-establish a new bevel on each hone. Flat hones will also give you a much faster sharpening job, assuming your workpiece/razor is also relatively flat.

A hone that is moderately flat in the spine direction can be heavily dished in the long stroke direction, and give nice edges (using an X-stroke). As long as that particular razor stays with that particular dished hone. As soon as that razor sees a flat hone, you'll be working a while on the "new" bevel. Hence the popularity of a flat hone. Maximum portability.

Glen,

I don't think those hone wear patterns are from the shape of the hone as much as from improper pressure during the honing stroke. You can create similar patterns on a flat hone by applying too much pressure during the middle or end of the stroke.

It's hard to say, though, because we all have so many razors that we don't hone them very often. :)

Josh

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Originally Posted by Sticky

The great joy of having flat hones is that you can go from one hone to another without being forced to re-establish a new bevel on each hone. Flat hones will also give you a much faster sharpening job, assuming your workpiece/razor is also relatively flat.

A hone that is moderately flat in the spine direction can be heavily dished in the long stroke direction, and give nice edges (using an X-stroke). As long as that particular razor stays with that particular dished hone. As soon as that razor sees a flat hone, you'll be working a while on the "new" bevel. Hence the popularity of a flat hone. Maximum portability.

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Good point!:)


Thats what I like about these forums. A significant amount of civilized discussion that increases our knowledge and allows us to make our own decisions. This has been a very good thread.

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Originally Posted by Sticky

The great joy of having flat hones is that you can go from one hone to another without being forced to re-establish a new bevel on each hone. Flat hones will also give you a much faster sharpening job, assuming your workpiece/razor is also relatively flat.

A hone that is moderately flat in the spine direction can be heavily dished in the long stroke direction, and give nice edges (using an X-stroke). As long as that particular razor stays with that particular dished hone. As soon as that razor sees a flat hone, you'll be working a while on the "new" bevel. Hence the popularity of a flat hone. Maximum portability.

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Steven,

I'm not sure this is true. I have a significantly dished hone (Belgian blue) sandwiched between my DMT 1200 and flat coticule. I don't have any problems with this or I'd just lap the blue more often. :)

If you think about it, the slight arch of a dished hone is probably like a 24' radius. Since the spine is only 5/8" from the edge, the difference in angle during the stroke is minimal enough to not screw things up.

Josh

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Originally Posted by Sticky

The great joy of having flat hones is that you can go from one hone to another without being forced to re-establish a new bevel on each hone. Flat hones will also give you a much faster sharpening job, assuming your workpiece/razor is also relatively flat.

A hone that is moderately flat in the spine direction can be heavily dished in the long stroke direction, and give nice edges (using an X-stroke). As long as that particular razor stays with that particular dished hone. As soon as that razor sees a flat hone, you'll be working a while on the "new" bevel. Hence the popularity of a flat hone. Maximum portability.

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Excellent point. You know your stuff, Sticky! It makes perfect sense that a flat hone will give a much faster sharpening job for the simple fact that.....more of the blade is in contact with more of the abrasive!

A Shapton rep I spoke with today did nothing for me other than pour gasoline on my HAD (and a disorder it is!) by answering all my questions and making me ga ga over the diamond on glass plate flat within .5 micron across its surface. Shame on him!!! He painted a good visual: If the abrasive on a specific hone is .5 micron and the variance across the surface of the hone is .5 micron, then on a pass, the edge will be in contact with only 50% of the abrasive. I'm not quoting him directly and I may have skewed his explanation; hopefully not. His point was think of the difference between .5 micron variance and .001" variance.

I admit, our discussions here and others like it are over analyzing this issue to an absurd degree. I'm not saying HAD is good, maybe HAD is bad. I have HAD.

I was thinking about the following as a possibility for me:.........Sell off the DMT 325, 1200 and my Norton 4000/8000 and go with the Shapton Diamond on Glass lapping plate (replaces the DMT 325), getting a Shapton ceramic on glass 1000 grit (replaces the DMT 1200) and run with that setup along with my belgian blue and yellow coticule.:hmmm:

Maybe someone can offer me counsel, give me a few slaps on the face and tell me to snap out of it. Please someone, help alleviate my HAD!:D:(:confused:

Give you counsel about your HAD? Ha! Fat chance!:)
Not until you have more hones than I do. You have 200 more to go!:D

Beats drinking,:tu

I'm looking for my Tormek manual, there was some mention of the issues of using the round 10" stone on the Tormek for sharpening the bevels of chisels. In use, the bevel is used to support the edge in the cut and those who swear by using flat hones for sharpening claimed that the "deep hollow" would cause loss of control in the cut. My math is rusty so I can't just whip up the numbers but on a typical chisel bevel, the hollowing only amounted to about 1 thousands of an inch or so... It's there, you can see it with the naked eye etc. but in practical use it's not an issue. Considering the width of even a well worn razors bevel is far far less than that of a typical chisel and that the kind of dishing we're talking about on a flat hone is so much less than the profile of a 10" grinding wheel I can't really see how a few thousands of an inch dishing is going to make much of a difference. It DOES make a big difference when polishing large flat bevels with a very fine stone such as chisels and plane blades, but I don't see it on the minuscule bevels of a straight razor.

Oh well, enough theory for tonight.... I need to go shave. :D

Regards

Christian

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Originally Posted by randydance062449

Give you counsel about your HAD? Ha! Fat chance!:)
Not until you have more hones than I do. You have 200 more to go!:D

Beats drinking,:tu

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I was going to say something like that, Randy. Thankfully it beats a lot of things. 200 Hones! :rolleyes::eek::bow

The thing that makes me a fan of the DMT hones is their versatility. You can use them for other stuff around the house. Once you get used to the Belgians, I'll wager you won't use the Norton much. Bruno's about the only guy to use Belgians and switch to a Norton. And he's from Belgium! :)

Josh

I like DMT so much I'm gonna' convert to all DMT except for one finishing hone. I might even put 'em in my avatar....

We need a "DMT brotherhood." :)

Josh

This is how the radiused edge mathed out:

• Assume a bevel width of around 0.015" (my razors average around 0.008" to 0.015"). Assume a radius of 12' to 24'. The distance from the radiused bevel surface to getting the bevel flat maths out to under 1 millionth of an inch (97 nanoInches to 200 nanoInches).

I would say that any flat hone following a dished hone is cutting the curved radius off to a flat so rapidly that it isn't, in most cases, a practical issue. The info on using a dished Belgian (or any hone) is extremely interesting.

My real worry with dished hones is that changing the spine angle (e.g. to heel leading/trailing) during the stroke will wear either the heel or tip unevenly? I was thinking the operator would have to be extremely consistent to avoid it. Is the dished out portion consistent? It's just so easy to make most hones flat, that I can't see any reason not to do it. Flat avoids all kinds of potential problems. For a new fella' like me anyway.

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Originally Posted by Sticky

. Flat avoids all kinds of potential problems. .

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Yup! What he said!:)

When a surface is flat to .001, that is the specification for its flatness. It's not "off". If you want to get it to .0001, you can do that but it will cost a lot of money. "Flatness" is just a question of money. Look at your friend's surface plates or better yet, look them up online in the Starrett catalog or MSC or Enco. You'll see that as they go from Grade A to B, they're certified at lower levels of flatness.

Flatness is spec'd to the performance requirements of the tool. I don't believe that going beyond .001 will result in a better shave. Your face varies a whole lot more than that!

I have a bunch of new digital micrometers in boxes if anybody wants to start measuring their stuff.

I spent a few years in optics (for an aerospace company) then I became a quality engineer for a medical device company that makes optical devices. The subject of flatness is a very serious one in the world of precision manufacturing. All proper metrology labs have at least one lab grade granite surface plate that is calibrated to be "flat" and more importantly, "repeatable" as specified by Federal Specification GGG-P-463c. What does that mean? Here's an article that explains it in great detail:
http://www.qualitydigest.com/aug03/a..._article.shtml

What does that mean to us razor owner/honers? Realistically not much. While we may strive for perfection, the world in which we live is so full of variables that our stones and razors are probably moving more than .001" over any given twenty-four hour period while sitting on a shelf. I have to agree with Kaptain Zero when he says that we can be happy flattening our stones with wet/dry sandpaper on a piece of glass.