floatglass as a surface plate thickness?

[ali27]

What do you think about my idea of using several(3-5) plates of floatglass on top
of each other to provide the necessary rigidity?

Ali27

I think that would be going to a lot of complication and effort to avoid buying a cheap granite surface plate of certified accuracy.

How much does your glass cost?

How big a plane to you hope to flatten?

Do you have other uses for a reference flat?

However, as Jacob sort of pointed out, if you already have something you trust be flat and rigid enough, just use it.

Personally I don't have a large cast iron power too (no room), and my surface plate cost 14 US dollars.

BugBear

Bugbear,

5 pieces of 60cm by 10cm by 1 cm cost 35 euro. I think weighs about 10kg
not sure. If I want a surface plate with that length(not counting diagonal)I would be paying about 100 euros or so at least and weight 50 kg or so(24´ by 18´ 4´).

Check this list:
http://www.mw-import.de/shop/pruefplatt ... atten.html

My biggest plane now is a no6, but I will buy no7 in the near future.

I don´t have any other uses for now, but will I think in some time.

Ali

 

[bugbear]

Bugbear,

5 pieces of 60cm by 10cm by 1 cm cost 35 euro. I think weighs about 10kg
not sure. If I want a surface plate with that length(not counting diagonal)I would be paying about 100 euros or so at least and weight 50 kg or so(24´ by 18´ 4´).
Check this list:
http://www.mw-import.de/shop/pruefplatt ... atten.html

My biggest plane now is a no6, but I will buy no7 in the near future.

I don´t have any other uses for now, but will I think in some time.

Ali

The plate you show is far too small for lapping, and much bigger than you need for "reference flattening". To flatten any plane up to 22" (a #7) using the process I recommend, you only need a 12"x18" reference.

Indeed, if you use the method I recommend, the loading forces on the reference and dramatically lower than lapping, and the requirements for rigidity lower, so you could probably simply use your 10mm glass, taking the recommended precautions.

I used my surface plate to make the rule in my s/h Moore & Wright combination square straight and parallel (*). It was severely saddle-backed from a lifetime of use.

It's nice to have something you absolutely know to be accurate within fine tolerances.

BugBear

(*) actually, I used the surface plate to make one side straight, and then used a micrometer to bring the other side parallel.

 

[ali27]

Bugbear,

5 pieces of 60cm by 10cm by 1 cm cost 35 euro. I think weighs about 10kg
not sure. If I want a surface plate with that length(not counting diagonal)I would be paying about 100 euros or so at least and weight 50 kg or so(24´ by 18´ 4´).
Check this list:
http://www.mw-import.de/shop/pruefplatt ... atten.html

My biggest plane now is a no6, but I will buy no7 in the near future.

I don´t have any other uses for now, but will I think in some time.

Ali

The plate you show is far too small for lapping, and much bigger than you need for "reference flattening". To flatten any plane up to 22" (a #7) using the process I recommend, you only need a 12"x18" reference.

Indeed, if you use the method I recommend, the loading forces on the reference and dramatically lower than lapping, and the requirements for rigidity lower, so you could probably simply use your 10mm glass, taking the recommended precautions.

I used my surface plate to make the rule in my s/h Moore & Wright combination square straight and parallel (*). It was severely saddle-backed from a lifetime of use.

It's nice to have something you absolutely know to be accurate within fine tolerances.

BugBear

(*) actually, I used the surface plate to make one side straight, and then used a micrometer to bring the other side parallel.

Bugbear, the floatglass plate I wrote about is actually smaller than the granite plate you suggest. If you mean longer ok, but a 12´´ by 18´´ granite plate is bigger than a 60cm by 10cm wide float glass plate.

Also couldn´t I use three float glass plates to create 3 flats? I have never done
this technique, but once understood it should be quite straightforward, no?

One could always correct the flattness of those float glass plates my the 3 surface
technique, but with a granite plate you wont know after a while.

Also 5 pieces of 60cm by 10cm by 10mm thick pieces of float glass weighs only
about 10kg or so I think. A granite plate with a diagonal of 60 cm would be much
heavier. I have a small room.

Nice job on the combination square!

I will be doing scraping once I have a surface plate. I have not yet decided whether
or not to buy a granite plate or float glass.

Where did you get your scraper? Is it HSS or carbide?

Ali

 

[bugbear]

Bugbear,

5 pieces of 60cm by 10cm by 1 cm cost 35 euro. I think weighs about 10kg
not sure. If I want a surface plate with that length(not counting diagonal)I would be paying about 100 euros or so at least and weight 50 kg or so(24´ by 18´ 4´).
Check this list:
http://www.mw-import.de/shop/pruefplatt ... atten.html

My biggest plane now is a no6, but I will buy no7 in the near future.

I don´t have any other uses for now, but will I think in some time.

Ali

The plate you show is far too small for lapping, and much bigger than you need for "reference flattening". To flatten any plane up to 22" (a #7) using the process I recommend, you only need a 12"x18" reference.

Indeed, if you use the method I recommend, the loading forces on the reference and dramatically lower than lapping, and the requirements for rigidity lower, so you could probably simply use your 10mm glass, taking the recommended precautions.

I used my surface plate to make the rule in my s/h Moore & Wright combination square straight and parallel (*). It was severely saddle-backed from a lifetime of use.

It's nice to have something you absolutely know to be accurate within fine tolerances.

BugBear

(*) actually, I used the surface plate to make one side straight, and then used a micrometer to bring the other side parallel.

Bugbear, the floatglass plate I wrote about is actually smaller than the granite plate you suggest. If you mean longer ok, but a 12´´ by 18´´ granite plate is bigger than a 60cm by 10cm wide float glass plate.

I was responding to your mention of a 24x18 granite surface plate.

If you wish to originate your own flat surface - good luck. I understand the theory, and have read a couple of accounts of just how much effort is involved. I have no plans to go there.

If you've read my pages on sole flattening, you'll know that I don't think scrapers are "the answer"

BugBear

 

[ali27]

The plate you show is far too small for lapping, and much bigger than you need for "reference flattening". To flatten any plane up to 22" (a #7) using the process I recommend, you only need a 12"x18" reference.

Indeed, if you use the method I recommend, the loading forces on the reference and dramatically lower than lapping, and the requirements for rigidity lower, so you could probably simply use your 10mm glass, taking the recommended precautions.

I used my surface plate to make the rule in my s/h Moore & Wright combination square straight and parallel (*). It was severely saddle-backed from a lifetime of use.

It's nice to have something you absolutely know to be accurate within fine tolerances.

BugBear

(*) actually, I used the surface plate to make one side straight, and then used a micrometer to bring the other side parallel.

Bugbear, the floatglass plate I wrote about is actually smaller than the granite plate you suggest. If you mean longer ok, but a 12´´ by 18´´ granite plate is bigger than a 60cm by 10cm wide float glass plate.

I was responding to your mention of a 24x18 granite surface plate.

If you wish to originate your own flat surface - good luck. I understand the theory, and have read a couple of accounts of just how much effort is involved. I have no plans to go there.

If you've read my pages on sole flattening, you'll know that I don't think scrapers are "the answer"

BugBear

I need to read more on the technique about creating 3 flats before I attempt it.

Bugbear, did you ever check the flattness of floatglass on your granite plate?

Ali

 

[Vann]

What do you think about my idea of using several(3-5) plates of floatglass on top of each other to provide the necessary rigidity?

While I've not had experience with float glass, I can tell you that 4 sheets of 1/8" steel plate have nowhere near the rigidity of a sheet of 1/2" steel (i.e the same thickness). The effect will be the same for glass.

I would estimate that 5 sheets of 10mm glass will be less rigid than a single sheet of 20mm glass.

But then I would estimate that 1 sheet of 10mm glass on a solid MDF base would be flat enough for what you need to achieve in a woodworking plane.

Cheers, Vann.

 

[ali27]

What do you think about my idea of using several(3-5) plates of floatglass on top of each other to provide the necessary rigidity?

While I've not had experience with float glass, I can tell you that 4 sheets of 1/8" steel plate have nowhere near the rigidity of a sheet of 1/2" steel (i.e the same thickness). The effect will be the same for glass.

I would estimate that 5 sheets of 10mm glass will be less rigid than a single sheet of 20mm glass.

But then I would estimate that 1 sheet of 10mm glass on a solid MDF base would be flat enough for what you need to achieve in a woodworking plane.

Cheers, Vann.

Hi Vann,

It doesn´t sound right to me. My guts
say that you might be correct in that 5 sheets of 10mm glass will not have
the rigidity of 50mm floatglass, but I have the feeling it will be more rigid
than 20 mm glass.

To be honest, I don´t think MDF makes much difference. MDF probably
like all wood has low rigidity. I think a solid mdf base underneath 10 mm
thick floatglass has the same rigidity as 12mm thick floatglass.

How is your plane passion going Vann? Hope your doing well.

Regards,

Ali

 

[Vann]

How is your plane passion going Vann?

Hi Ali,
It's seriously out of control. I have gathered heaps of old wrecks to do up (e.g. I have 15 Record 04s in various states of disrepair) , but only found time to do up two (and then to a low standard). And there's even less time to actually make shavings

Ahh, the trials and tribulations of having a full time job and a young family.

Cheers, Vann.

 

[bugbear]

It doesn´t sound right to me. My guts
say that you might be correct in that 5 sheets of 10mm glass will not have
the rigidity of 50mm floatglass, but I have the feeling it will be more rigid
than 20 mm glass.

Resistance to bending varies with inverse cube of thickness, all other things being equal.

So 20mm thick should be 8 times as stiff as 10mm thick. A simple stack of 10mm stack will increase stiffness linearly, so Vann appears to be correct.

BugBear

 

[bugbear]

To be honest, I don´t think MDF makes much difference. MDF probably
like all wood has low rigidity. I think a solid mdf base underneath 10 mm
thick floatglass has the same rigidity as 12mm thick floatglass.

Even assuming your MDF has infinite rigidity, if your floatglass is forced (by the load) to conform to the MDF surface, your flatness is now the flatness of the MDF, not the floatglass.

BugBear

 

[ali27]

It doesn´t sound right to me. My guts
say that you might be correct in that 5 sheets of 10mm glass will not have
the rigidity of 50mm floatglass, but I have the feeling it will be more rigid
than 20 mm glass.

Resistance to bending varies with inverse cube of thickness, all other things being equal.

So 20mm thick should be 8 times as stiff as 10mm thick. A simple stack of 10mm stack will increase stiffness linearly, so Vann appears to be correct.

BugBear

Thanks for the reply Bugbear. Very interesting. I need to read
more about this.

So, roughly how much stiffer would a 4 piece stack of 10 mm be compared
to 1 plate of 10mm? Would it even make sense to do so or just get the
thickest piece of float glass, 25mm is best in this regard.

I don´t know/understand how you calculated that 20 mm floatglass is 8times
asstiff as 10mm, but I would guess then that 25mm thick glass is at least
12 times as stiff?

Ali

 

[ali27]

How is your plane passion going Vann?

Hi Ali,
It's seriously out of control. I have gathered heaps of old wrecks to do up (e.g. I have 15 Record 04s in various states of disrepair) , but only found time to do up two (and then to a low standard). And there's even less time to actually make shavings

Ahh, the trials and tribulations of having a full time job and a young family.

Cheers, Vann.

Vann, you need a plane detox my friend!

Ali

 

[ali27]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Floatglass is supposedly very flat and the spotting technique
does not put a lot of weight on the plate so it could work
quite welll, no?

Bugbear ,did you ever check the flatness of floatglass with
your granite surface plate?

Ali

 

[studders]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Ali

Depends what Newspaper it is and, what pages you use, page 3 would be no good at all. :wink:

 

[ali27]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Ali

Depends what Newspaper it is and, what pages you use, page 3 would be no good at all. :wink:

:mrgreen: :mrgreen:

Would the sports section of the newspaper provide enough support?

Ali

 

[bugbear]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Before I got a surface plate, I flattened a #5 bailey plane using 6mm glass supported on router mat on a flattish support.

When I checked the plane, having got the surface plate, it didn't need any more work.

In your position, I would proceed with a single piece of 10mm glass, supported as recommend, and "see how you go".

I've never flattened anything bigger than #5.

A further practical hint - it may be best in the very early stages of a badly warped sole to use the "lapping" method, on any old flattish surface you have (e.g. MDF).

This will VERY rapidly remove the high spots, and you can then proceed with the prussian blue approach.

It's like planing (scrub-jack-jointer) or golf (drive, chip putt).

BugBear

 

[ali27]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Before I got a surface plate, I flattened a #5 bailey plane using 6mm glass supported on router mat on a flattish support.

When I checked the plane, having got the surface plate, it didn't need any more work.

In your position, I would proceed with a single piece of 10mm glass, supported as recommend, and "see how you go".

I've never flattened anything bigger than #5.

A further practical hint - it may be best in the very early stages of a badly warped sole to use the "lapping" method, on any old flattish surface you have (e.g. MDF).

This will VERY rapidly remove the high spots, and you can then proceed with the prussian blue approach.

It's like planing (scrub-jack-jointer) or golf (drive, chip putt).

BugBear

Thanks for the advises Bugbear.

One more question about stacking floatglass for more stiffness. Now as you
wrote stacking seems not to increase stiffness very much. What about expoxying
the plates together. If I´d epoxy 3, 10mm plates. Would that give me the stiffnes
of a single 30mm plate?

Epoxying would probably worsen the flatness, but just wondering about
the stiffness.

Ali

 

[Jacob]

Bugbear,

Do you think a piece of 25mm thick floatglass(supported
with some newspaper) would be stiff enough to flatten a plane
by the spotting(prussian blue) method?

Before I got a surface plate, I flattened a #5 bailey plane using 6mm glass supported on router mat on a flattish support.

When I checked the plane, having got the surface plate, it didn't need any more work.

In your position, I would proceed with a single piece of 10mm glass, supported as recommend, and "see how you go".

I've never flattened anything bigger than #5.

A further practical hint - it may be best in the very early stages of a badly warped sole to use the "lapping" method, on any old flattish surface you have (e.g. MDF).

This will VERY rapidly remove the high spots, and you can then proceed with the prussian blue approach.

It's like planing (scrub-jack-jointer) or golf (drive, chip putt).

BugBear

Thanks for the advises Bugbear.

One more question about stacking floatglass for more stiffness. Now as you
wrote stacking seems not to increase stiffness very much. What about expoxying
the plates together. If I´d epoxy 3, 10mm plates. Would that give me the stiffnes
of a single 30mm plate?

Epoxying would probably worsen the flatness, but just wondering about
the stiffness.

Ali

Stiffness would be fine but with a laminate construction you could get distortion due to temperature differentials through the stack (think "bi-metal strip") specially if you are working hard on the grinding process and heating up the topmost plate. I'd suggest keeping the plate stack unglued and possibly lubricated, and to keep exchanging the topmost plate for a lower one, shuffle the stack as it were. It would also help to turn the plates top to bottom, end to end, to distribute and nullify any localised distortion.
Sharpening is not easy!

PS oh no we haven't got to sharpening yet. That's when things start really getting tricky :shock:

 

[bugbear]

Stiffness would be fine but with a laminate construction you could get distortion due to temperature differentials through the stack (think "bi-metal strip")

That applies even for a solid reference. Indeed, for very high precision work (tenths and hundredths of thous), temperature control is critical. Even sunlight shining on the upper surface of a 4" granite plate can (ever so slightly...) warp it.

specially if you are working hard on the grinding process and heating up the topmost plate.

Not an issue in this case - Ali isn't using the reference as a tool, only as a reference, keeping both loads and heat low.

BugBear

 

[Dangermouse]

Well my brain is spinning after reading all these posts. I try to keep things simple, being a simple Cornish country lad. You don't need to get the plane sole dead flat in an engineering sense, thats an impossible task anyway, just theory. The LN standard is 1.5 thou, the Clifton standard is 3 thou, around those figures is fine for any plane you use. If you can get a consistent 2 thou standard your ok. To get better would take a huge amount of work and time, not worth the effort. I use a slab of polished granite I got from my local stone mason, 32 inches long, 8 inches wide, 4 inches thick. Nice and flat to the tolerance needed, tested with my engineers straight edge. I paid all of a crisp fiver it and it will outlast me and never flex. Job sorted.
George