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DuoSharp 10" Not Flat

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Review by Ocelot posted 02-15-2016 05:41 PM 3508 views 0 times favorited 37 comments Add to Favorites Watch
DuoSharp 10" Not Flat No-picture-s No-picture-s Click the pictures to enlarge them

A few months ago I bought (for not very good reasons) the DMT DuoSharp Coarse/Extra-Coarse 10” “stone”.

Upon receiving it, I put new bevels on a few plane blades – for which it did a quick and fine job, and quickly flattened the sole and sides of a No 4 sized bench plane – one I didn’t particularly care about. The plane seemed flat enough, and cuts excellently, but I didn’t pay much attention while doing this first one.

Recently, I’ve bought 5 block planes and decided to flatten the soles of 3 of them.

I use the diamond stone dry – as the instructions say it can be used wet or dry.

The first one, a Stanley 60 1/2, I did the same way as I had done the No 4 bench plane, by grinding it back and forth the long way of the plane the long way of the “stone”. I wasn’t particular and ended up, I think using the Course side mostly for this task – and was satisfied with the result.

The second one, a “New Britton” branded plane – exactly like a Stanley 220 (about 14 square inches on sole), I decided to be more deliberate about. So, first, I used the Extra Course side of the stone – moving the plane side to side (the short way of the plane) side to side on the stone (the short way of the stone). After I produced a scratch pattern on the entire sole, I flipped the stone over to the course side and began to work the sole of the plane the long way.

It was immediately clear that only the central area of the plane sole was contacting the stone. I thought this was odd, but continued for awhile. Then I marked the sole with a permanent marker and ground away some more. It became very clear that the plane and the stone are not flat. Best I can make out, the entire stone is bowed or cupped so that the Extra Coarse side is concave (producing a convex surfaces on the sole of the plane), while the Coarse side is convex – trying to produce a concave surface on the sole of the plane.

Here’s the sole of the 220 plane after first being ground side to side on the Extra Coarse side of the stone, then ground about 2000 strokes (I counted) the long way on the Course side. I still haven’t reached the edges.

The packaging of the DMT stone and the little paper inside say the stone is “flat”, but do not specify a tolerance. On the other hand, there is something like a satisfaction guarantee on the edge of the package.

Well, I’m not, at the moment, satisfied.

I’ve heard many good things about the products from DMT, and figure that I just got a bad one, but until the matter is resolved, I’m feeling fooliish for paying $120 for this thing (ordered from Amazon).

It’s hard to look at the stone with a straight edge and a feeler gauge since it is gritty and has holes in it. I’ve tried, and I think I see the bow in the stone, but it’s hard to take a picture of and a feeler gauge is not going to give a meaningful result.

-Paul




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Ocelot

2083 posts in 2788 days



37 comments so far

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TheWoodRaccoon

364 posts in 1079 days


#1 posted 02-15-2016 07:09 PM

Clean the stone thoroughly with water and pat dry. Lay a reliable straightedge across the stone length wise and across. Shine a small flashlight along the seam where the straightedge and stone meet. If the stone isn’t flat, you should be able to see light between the straightedge and the stone from the other side, in the center or on the edges, depending if it’s concave or cupped. If there is indeed a gap and it’s as bad as you make it seem, you should be able to see it clearly without the use of a feeler gauge.

If you can’t detect any gaps by eye, Its most likely fine.

-- still trying to think of a clever signature......

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Ocelot

2083 posts in 2788 days


#2 posted 02-15-2016 08:23 PM

Racoon,

I have washed scrubbed, dried the stone and done as you say.

Because of the holes in the steel, you can always see light – also the grit on the stone makes it impossible to have the straightedge down hard on the steel.

If the stone is fine, how does it produce the cupping that I see in the plane sole? If I have used the wrong procedure, somebody please show me the right way!

-Paul

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OSU55

1871 posts in 2139 days


#3 posted 02-15-2016 09:16 PM

You dont say whether you checked the plane sole for flatness with a straightedge. Its possible the sole is that far out and the stone is fine.

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Ocelot

2083 posts in 2788 days


#4 posted 02-15-2016 09:58 PM

OSUSS,

I did check the plane sole with a straight edge. I should have said that.

In any case, since I worked the plane first on one side of the stone and then on the other, the difference between the two sides is clearly revealed by the scratch marks made on the plane. If the plane sole was flat (except for extra-coarse scratches), then working it on the other side (Coarse side) of the stone should create scratches all over the sole immediately. The pattern shown in the photos makes clear that the area of contact is limited to the central part of the sole, indicating that either the sole or the stone or both are not flat…. after being thoroughly worked over on the extra-coarse side of the stone.

-Paul

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Ocelot

2083 posts in 2788 days


#5 posted 02-15-2016 10:17 PM

Here is an annotated version of the photo. Sorry the web site shrank it when I uploaded, but I believe the text can still be read.

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TheWoodRaccoon

364 posts in 1079 days


#6 posted 02-15-2016 10:54 PM



Racoon,

I have washed scrubbed, dried the stone and done as you say.

Because of the holes in the steel, you can always see light – also the grit on the stone makes it impossible to have the straightedge down hard on the steel.

If the stone is fine, how does it produce the cupping that I see in the plane sole? If I have used the wrong procedure, somebody please show me the right way!

-Paul

- Ocelot

You’re not supposed to press hard with the straightedge, just laying it on the surface is fine.
How coarse is it? To me it sounds like you have a surface akin to the gravel in a driveway.

-- still trying to think of a clever signature......

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Ocelot

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#7 posted 02-15-2016 11:14 PM

DMT calls it 220 grit, but apparently diamond grit sizes are calculated differently than other abrasives, so it seems much more abrasive than normal 220 grit sandpaper.

-Paul

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TheWoodRaccoon

364 posts in 1079 days


#8 posted 02-16-2016 12:48 AM



DMT calls it 220 grit, but apparently diamond grit sizes are calculated differently than other abrasives, so it seems much more abrasive than normal 220 grit sandpaper.

-Paul

- Ocelot

You should be able to lay a straightedge flat even on something even as coarse as 80 grit! Im really having a hard time understanding the problem you’re having with the straightedge method. Also, what “holes” are you referring to? There shouldn’t be any. Maybe you can take some pictures of the stone?

-- still trying to think of a clever signature......

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Ocelot

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#9 posted 02-16-2016 03:04 PM

Raccoon,

I didn’t realize you were unfamiliar with the product. I should have posted a product photo.

Here’s a picture and video from the manufacturer.

https://www.youtube.com/watch?v=Rf3NR8GBzRw&feature=youtu.be&hd=1

And DMT’s web page for this product. https://dmtsharp.com/sharpeners/bench-stones/duosharp/

View MrRon's profile

MrRon

5090 posts in 3393 days


#10 posted 02-16-2016 05:05 PM

There is a good chance the plane soles are not flat. In the first place, I wouldn’t use diamond to flatten a large area like a plane sole. You will be prematurely wearing down the diamond. I would use silicon, paper backed abrasive sheets on a flat surface (table saw table, etc) and save the diamond for small jobs. Personally, I don’t like DMT stones. I prefer the stones that are fully coated with diamond dust (no holes). EZE-lap stones are the ones I use.

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Ocelot

2083 posts in 2788 days


#11 posted 02-16-2016 05:29 PM

MrRon,

I’m not sure I understand your comment. My goal was to flatten the plane sole, so yes, it is not flat.

Wearing an abrasive surface is just part of the cost of using it. It was my aim to save time by using diamond rather than using sandpaper on my granite surface plate. Even if time is not money, time is life and life may be too short to flatten many planes on sandpaper. I did one number 4 bench plane and used I think 8 hours of my life. I’m sure I’ve wasted more time doing less important things, but still, I’m willing to wear down the diamonds to save life (time).

The holes, in theory, capture the “fines” as they call them, that is the ground iron – so that your plane sole isn’t floating on a layer of ground iron but instead is down on the diamonds. In theory…

-Paul

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Mainiac Matt

8436 posts in 2478 days


#12 posted 02-16-2016 05:52 PM

I’ve found that a set of feeler gages and a known good reference surface (granite plate or known flat plate of thick glass, etc…) are the best way to check the flatness of surfaces.

The DMT “stones” will flex, as will the plastic mounting bases. So if you’re applying downward pressure while stroking the plane back and forth, I suspect that is what may be causing your problems.

Try using them on a flat surface and clamp a couple strips of wood down to prevent them sliding about and see if that doesn’t help you out.

-- I yam what I yam and that's all what I yam

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Ocelot

2083 posts in 2788 days


#13 posted 02-16-2016 09:03 PM

Matt,

I do have a granite surface plate, but I was working on my table saw table (cast iron) not using the plastic base, but with the “anti-skid” mat (supplied with the stone) under the stone.

The thing is, if it were flexing, I would expect it to flex both ways – that is, that the coarse and extra-coarse sides would both be convex, but that’s not what’s happening.

I intend to call and talk to them. They do have telephone hours, but only when I’m supposed to be at work.

-Paul

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TheWoodRaccoon

364 posts in 1079 days


#14 posted 02-16-2016 09:10 PM



Raccoon,

I didn t realize you were unfamiliar with the product. I should have posted a product photo.

Here s a picture and video from the manufacturer.

https://www.youtube.com/watch?v=Rf3NR8GBzRw&feature=youtu.be&hd=1

And DMT s web page for this product. https://dmtsharp.com/sharpeners/bench-stones/duosharp/

- Ocelot

Oh THATS what you have? LOL! I thought you had the ones that are 1/4 inch thick solid nickel alloy, like my 6” DMT stone!

-- still trying to think of a clever signature......

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Ocelot

2083 posts in 2788 days


#15 posted 02-16-2016 09:16 PM

... and until today I didn’t know they make a solid nickel alloy version.

:-o

In any case, since they recommend flattening plane soles and even waterstones with this thing, it should be flat.

-Paul

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