Granite surface plate/flattening/where to buy?

[ali27]

I have been looking for a granite surface plate
for a while now. I want to use this for accurately
flattening plane soles.

I have used float glass, but I am not happy with this.

Unfortunately the granite surface plate I need is about
20 inches long. The surface plates at this size are
almost as wide and usually 3-4 inches thick which
makes them very heavy and quite expensive(shipping)

I was wondering if somebody knows where to buy
a granite sp that is about 20 inches long but only
10 inches max wide and not so thick.

Perhaps if there is much interest in such a surface
plate maybe a vendor/seller would be interested
in offering this.

A 24/18/3 inch granite sp is about 80 kg or so.
If such a surface plate could be sawn in two pieces
or even 3 pieces, perhaps also only 2 inches thick,
that would make such a plate much lighter(20kg or so?)
easier to use and cheaper I think.

I am sure that a 2 inch thick granite
SP is much stiffer than an half inch thick float glass.

What do you guys think? Make any sense?

Ali

 

[Karl]

Ali - whereabouts in the country are you? I have an 18" x 3" thick granite plate that I could be persuaded to part with in exchange for some beer vouchers.

Cheers

Karl

 

[ali27]

Ali - whereabouts in the country are you? I have an 18" x 3" thick granite plate that I could be persuaded to part with in exchange for some beer vouchers.

Cheers

Karl

Hi Karl,

I live in the Netherlands(2010 world champion football!)

18 inch is unfortunately a bit too short. I want to flatten
jointers as well.

Thanks for the offer.

You English guys love your beer!

Ali

 

[jasonB]

Pop down to your local monumental mason and get then to cut a grave stone in half. Most granite for this type of use and worktops is machine ground to acceptable tollerance for flattening. Infact an offcut of 30mm thick granite worktop would probably do the job, get two bits bonded together if you want more thickness

Jason

 

[ali27]

Pop down to your local monumental mason and get then to cut a grave stone in half. Most granite for this type of use and worktops is machine ground to acceptable tollerance for flattening. Infact an offcut of 30mm thick granite worktop would probably do the job, get two bits bonded together if you want more thickness

Jason

Thnx for the tip. Are those gravestones really that flat? I think
I will be bringing my straightedge with me to check.

Ali

 

[laird]

I got a black granite name plate made for the house at a local gravestone maker. The side he planed for the lettering is flat, to engineering standards. I think your cost ill be minimal as they always have broken bits of stone lying around, too small for their usual use but perfect for you.

 

[Racers]

Hi, Ali

Here is my laping set up its just a piece of 6mm glass on my bench, as long as you stretch the abrasive tight you don't get any problems.

Pete

 

[bugbear]

Hi, Ali

Here is my laping set up its just a piece of 6mm glass on my bench, as long as you stretch the abrasive tight you don't get any problems.


Pete

How confident are you of the actual flatness of the results? What have you checked against?

BugBear (with a teensy obsession in this area...)

 

[Racers]

Hi,

Checked with a straight edge/feeler gages on a surface plate (table saw)
If you keep the grit clean with frequent vacuming and use all the width it works well.

I have done loads of planes from No3 to No8, with 60 grit you can take loads off quite quickly.


Pete

 

[bugbear]

I have been looking for a granite surface plate
for a while now. I want to use this for accurately
flattening plane soles.

I have used float glass, but I am not happy with this.

Unfortunately the granite surface plate I need is about
20 inches long. The surface plates at this size are
almost as wide and usually 3-4 inches thick which
makes them very heavy and quite expensive(shipping)

Since a granite surface plate is nowhere near big enough for lapping (*) (especially a jointer), I presume (and hope) you're using the plate as a reference.

As such, a 12" x 18" is large enough, since the diagonal is 21.6 inches.

This will suffice for everything up to a #7 (22").

The next size up is 18"x24", which will be at least twice as heavy, and possibly more, since larger plates are often thicker too.

I have seen (on various forums) proposals to get large (18x24) plates cut into multiple (e.g.) 6"x24" plates as a forum "group buy", but this has always fallen at the hurdle of cost. Getting granite custom cut is very expensive, and (especially in the USA) Enco sometimes has such cheap deals (including free delivery!) that it's simply isn't a saving.

BugBear

* Dunbar, the populariser of so-called-lapping recommends the lapping surface be 3 times as long as the plane

 

[woodbloke]

Hi, Ali

Here is my laping set up its just a piece of 6mm glass on my bench, as long as you stretch the abrasive tight you don't get any problems.

Pete

This is pretty much the same method I used...worked for me. I used 10mm glass but it doesn't make a lot of difference - Rob

 

[ali27]

I have been looking for a granite surface plate
for a while now. I want to use this for accurately
flattening plane soles.

I have used float glass, but I am not happy with this.

Unfortunately the granite surface plate I need is about
20 inches long. The surface plates at this size are
almost as wide and usually 3-4 inches thick which
makes them very heavy and quite expensive(shipping)

Since a granite surface plate is nowhere near big enough for lapping (*) (especially a jointer), I presume (and hope) you're using the plate as a reference.

As such, a 12" x 18" is large enough, since the diagonal is 21.6 inches.

This will suffice for everything up to a #7 (22").

The next size up is 18"x24", which will be at least twice as heavy, and possibly more, since larger plates are often thicker too.

I have seen (on various forums) proposals to get large (18x24) plates cut into multiple (e.g.) 6"x24" plates as a forum "group buy", but this has always fallen at the hurdle of cost. Getting granite custom cut is very expensive, and (especially in the USA) Enco sometimes has such cheap deals (including free delivery!) that it's simply isn't a saving.

BugBear

* Dunbar, the populariser of so-called-lapping recommends the lapping surface be 3 times as long as the plane

Hi Bugbear,

The longest plane I have is a no6 which is 18 inches long
I think. If I bought a 24 inch long surface plate I would have
some room(the diagonal) to flatten the sole on the surface plate.

A 36 inch long plate would probably be better, but as I said,
they are so bloody heavy, never mind the cost.

Bugbear, I had seen the Enco site. Very nice prices. I wish
the shipping would be free to Europe, but I am sure it is not.

For example at Enco a 36/24/4 granite surface plate is 125 USD. If these would be sawn in 36/6/4 pieces, the cost would be 125/4=
31.25 per piece+sawing cost.

I have no idea how much the sawing would cost. shipping would
be a lot I think, about 100 dollars or so.

Axminster have one also:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
450 x 600 x 100mm

price 95GBP+50 GBP for the shipping=150GBP
This one could be sawn in 3 pieces I think.

Problem is that one still gets a 3 to 4 inch thick plate. Really
heavy plate which one doesn´t need unless.

Bugbear wouldn´t the sawing cost a lot less if the plate would be
only an inch or so thick?

A 40 inch long, 6-9 inches wide, one inch thick plate would be
great don´t you think.

Ali

 

[ali27]

Hi, Ali

Here is my laping set up its just a piece of 6mm glass on my bench, as long as you stretch the abrasive tight you don't get any problems.

Pete

Pete, your setup looks nice. If it works for you great! For me
the glass thing is not working. My glass plate itself is not really
flat and I notice that it does bend slightly.

Perhaps a really flat glass plate with something very flat underneath it(mdf) to support it would work.

I prefer the granite plate tough.

Ali

 

[ali27]

I got a black granite name plate made for the house at a local gravestone maker. The side he planed for the lettering is flat, to engineering standards. I think your cost ill be minimal as they always have broken bits of stone lying around, too small for their usual use but perfect for you.

Thanks for the info. I will definitely check this out.

Ali

 

[bugbear]

Axminster have one also:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
450 x 600 x 100mm

price 95GBP+50 GBP for the shipping=150GBP
This one could be sawn in 3 pieces I think.

Problem is that one still gets a 3 to 4 inch thick plate. Really
heavy plate which one doesn´t need unless.

They're made that thick because that's the thickness you need to have the RIGIDITY for the accuracy to have meaning.

There's no point having something flat to (say) a tenth of a thou, if it can flex by (say) 4 thou under common working loads...

BugBear

 

[ali27]

Axminster have one also:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
450 x 600 x 100mm

price 95GBP+50 GBP for the shipping=150GBP
This one could be sawn in 3 pieces I think.

Problem is that one still gets a 3 to 4 inch thick plate. Really
heavy plate which one doesn´t need unless.

They're made that thick because that's the thickness you need to have the RIGIDITY for the accuracy to have meaning.

There's no point having something flat to (say) a tenth of a thou, if it can flex by (say) 4 thou under common working loads...

BugBear

True, but some people seem to have good results with
float glass that is only 1 cm thick.

I don´t know for sure, but I think an inch thick granite
is much stiffer than 1cm glass, no?

Ali

 

[bugbear]

Axminster have one also:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
450 x 600 x 100mm

price 95GBP+50 GBP for the shipping=150GBP
This one could be sawn in 3 pieces I think.

Problem is that one still gets a 3 to 4 inch thick plate. Really
heavy plate which one doesn´t need unless.

They're made that thick because that's the thickness you need to have the RIGIDITY for the accuracy to have meaning.

There's no point having something flat to (say) a tenth of a thou, if it can flex by (say) 4 thou under common working loads...

BugBear

True, but some people seem to have good results with
float glass that is only 1 cm thick.

But you asked about surface plates!

Which are both flat and rigid.

Glass is merely smooth, and as flat as the surface it's lying on.

But if you want flatness you can TRUST, get a suitable surface plate.

I've also posted my findings on lapping on a (defunct) website, herewith from the wayback machine:

http://web.archive.org/web/200605092205 ... atten.html

BugBear

 

[ali27]

Axminster have one also:
http://www.axminster.co.uk/product.asp? ... e=1&jump=0
450 x 600 x 100mm

price 95GBP+50 GBP for the shipping=150GBP
This one could be sawn in 3 pieces I think.

Problem is that one still gets a 3 to 4 inch thick plate. Really
heavy plate which one doesn´t need unless.

They're made that thick because that's the thickness you need to have the RIGIDITY for the accuracy to have meaning.

There's no point having something flat to (say) a tenth of a thou, if it can flex by (say) 4 thou under common working loads...

BugBear

True, but some people seem to have good results with
float glass that is only 1 cm thick.

But you asked about surface plates!

Which are both flat and rigid.

Glass is merely smooth, and as flat as the surface it's lying on.

But if you want flatness you can TRUST, get a suitable surface plate.

I've also posted my findings on lapping on a (defunct) website, herewith from the wayback machine:

http://web.archive.org/web/200605092205 ... atten.html

BugBear

Bugbear,

What thickness do you think is sufficient(rigid enough) to flatten plane soles? Surface plates are 2,3 and 4 inch thick.

I understand that the thicker the better in terms of rigidity/stifness, but how thick is enough for flattening plane soles?

I had read your info about scraping and filing. I might try that
as well.

Ali

Ali

 

[ali27]

Maybe if there is enough interest we can persuade
Matthew to sell them.

What do you think Matthew?

Ali

 

[Lons]

I regularly fit kitchens with granite worktops and I would be surprised if a standard 30mm thick worktop is not flat enough or rigid enough to cope with flattening the sole of a plane.
Offcuts are always available from granite suppliers locally who would be happy to cut to size and polish the stuff.

Bob