Thread: Plane sole flattening, again...

Here are the results for the testing of the plane lapped at 6 microns.

Plane flattening study 051819a_Page_6.jpg

Note the Y axis in comparison to the above presented data for the plane at 9 microns (#67). Here is the same plot re-scaled to match the scale of the 9 micron plot above .

Plane flattening study 051819a_Page_7.jpg

Now to 3 microns.

3 micron lapping.jpg

Getting this stage done didn't take much energy compared to prior efforts. Just barely shiny enough for optical flats.

first optical flat fringes woodriver block plane 051919a.JPG

first optical flat fringes woodriver block plane 051919b.JPG

Rob; your at 3 micron honing compound. Can you explain that deep scratch pattern on the planes sole.

They're scratches and they're consistent over the entire surface suggesting either that the lap is contaminated or that the diamond compound is or perhaps (less likely) that they're being carried over in the relatively soft plane body. I don't see such scratches using this combination of compound and lap with harder materials such as chisel backs.

Nonetheless, they've been present all along at every stage of this work and the consistency of the cutting action of the plane keeps improving.

A quick check with my New Age hardness tester confirms that the plane is very soft with a reading returned of HRC ~15. This is below the calibrated range of my instrument and well below the NIST suggested minimum of HRC 25 or so but suffice it to say it's pretty soft, extremely soft by chisel and plane blade standards.

Originally Posted by rob streeper

They're scratches and they're consistent over the entire surface suggesting either that the lap is contaminated or that the diamond compound is or perhaps (less likely) that they're being carried over in the relatively soft plane body. I don't see such scratches using this combination of compound and lap with harder materials such as chisel backs.

Nonetheless, they've been present all along at every stage of this work and the consistency of the cutting action of the plane keeps improving.

Rob; that would seem the likely case.

Here are some magnified shots. The lap was cleaned at several points during this work so I suspect that the compound is the culprit.

D12 shot of 3 micron lapped plane.jpg

D12 shot of 3 micron lapped plane b.jpg

I switched to a fresh lapping plate using the same 3 micron compound and plane. The scratch pattern remains as above suggesting that the particle size distribution and the softness of the plane body are the cause. The same degree of flatness is preserved.

first optical flat fringes woodriver block plane 051919d.JPG

Here are some better shots of the interference fringes.

first optical flat fringes woodriver block plane 051919f.JPG

first optical flat fringes woodriver block plane 051919g.JPG

The rep rate of my phone camera is apparently close enough to one of the fundamentals of the sodium vapor light used to show the patterns that it is difficult at times to photograph what is clearly visible to the eye. I often get wandering black bands in the whole camera image depending on the position of the camera relative to the workpiece.

The fringes here represent differences in the surface of about 11.5 millionths of an inch.

More information here: https://en.wikipedia.org/wiki/Optical_flat, https://www.kemet.co.uk/blog/lapping/how-to-measure-flatness-technical-article

If you look on the net you can find a couple of decent PDF files freely available. The one by Knight optical is short and very useful, it is copyrighted so I can't post it here. Seek and ye shall find...

Here are some images of the plane sole at 3 microns to a 4 micron lapped standard. The instrument is a GAR B1 microfinish comparator.

The instrument is an illuminated split view comparator.

GAR surface finish comparator.jpg

It makes use of standard strips with ranges of prepared surface finishes.

surface finish standard strip.jpg

These are a little harder to see but the surface of the plane lapped at 3 microns is comparable to the 4L (4 micron lapped) standard.

3 micron plane bottom compared to 4 micron lapped standard in GAR comparator.JPG

3 micron plane bottom compared to 4 micron lapped standard in GAR comparator b.JPG

In both of the above photo's the 4L standard is on the right. Thus even though scratches are visible the finish is consistent with what should be produced by 3 micron lapping compound. The plane surface is a lot finer now than it would be after rubbing it on 120 grit sandpaper on a table saw top.

It would be interesting to see what would happen if you put the plane in the freezer and then checked it for flatness. I doubt it would move, but still would be interesting to see if the flatness changed with temperature and if so, how much.

Originally Posted by D.W.

It would be interesting to see what would happen if you put the plane in the freezer and then checked it for flatness. I doubt it would move, but still would be interesting to see if the flatness changed with temperature and if so, how much.

I could add that to the list of things to look at when I get the surface shiny enough. For Alaskan woodworkers? What about global warming?

I was thinking more like my shop!

It's not as hot as where you are, but my shop is part of the way underground and semi-heated. If it's zero outside, my shop is 32(F for the Aussies. about 20 below C outside and zero C in my shop). In the summer, it can be 85F in my shop (29C), which sounds like no big deal except that's usually when it's mid to high 90s outside and high humidity in the shop - the RH in the shop goes bonkers, above the 63 percent threshold where things will rust without the presence of any standing water.

It's probably the humidity more than the temperature, but my wooden tools move seasonally. I orient the wood in them so that any movement is minimal and not in a direction that matters (e.g., I don't put anything less than pin straight beech in a plane so that it doesn't twist).

Temperature and absolute moisture sort of go together, as does the temperature differential outside to inside in my shop (since that can drive up the RH when my shop is cooler but close to the outside).

Curious about the stability of the castings in these older planes - if they've seasoned to a point where temp makes the metal expand or contract, but not do anything funny otherwise.

I've got a Stanley 9 1/2 that I'm thinking of working on when I'm done with this one. Never been messed with as far as I can tell. If flex is an issue it should show it to a greater degree than this relatively heavy WoodRiver.

Here's some shots showing the comparison of the plane sole lapped at 3 microns and the 8L (8 micron lapped) standard.

3 micron plane bottom compared to 8 micron lapped standard in GAR comparator a.jpg

3 micron plane bottom compared to 8 micron lapped standard in GAR comparator b.jpg

3 micron plane bottom compared to 8 micron lapped standard in GAR comparator c.jpg

The 8L standard is much rougher than the plane bottom is.