Official Luthiers Forum!

     I have been building a while and though I have about anything you can concieve that will make sawdust or metal chips , I saw somthing I never gave a thought about.
     When I needed a true flat surface I used to use my table saw top and a piece of sandpaper glued to the top and then used the ripfence.
    I joint many top and back plates this way. Well I bought a granite plate a month ago. All I can say is that this was something I should have purchased a long time ago. IF you can afford one a 24 inch square plate is a Godsend. You can true anything to an accuracy that will amaze you.
    PSA ( pressure sensitve adhisive) backed paper makes this a device for joining plates, squaring the top to the sides and flatening necks for joining fingerboards with accuracy and gives you some of the best glue joints possible.
    Thanks for listening to me type but I feel this is info that tool junkies would like to hear.
john hall
blues creek guitarstippie5338753.7414814815

It's been on my wish list for a while. Maybe next month for my birthday.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Thanks, John. These blocks always looked very appealing for lots of operations. As a cheap alternative, I've been using 1/4" glass for surfacing wood, truing blades and flattening old plane soles. As a machinist with the need for precision, were you able to actually measure the differences from your table saw vs. the granite?

If I lived close to Grizzly, the granite blocks would be very affordable...unfortunately, shipping costs more than the product. Nonetheless, I'll snoop around locally for one. Thanks for the info.

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JJ
Napa, CA
http://www.DonohueGuitars.com

I was contemplating buying a granite slab from Lee Valley. The claim the surface to be flat within a .0001 (ten-thousandths)of an inch... And for the price I'm definitely going to buy one the next I'm there. Check it out: http://www.leevalley.com/wood/page.aspx?c=1&p=32526&cat=1,43 513,51657

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I'd like to be able to prove, just for once, that money wouldn't make me happy...

I have heard of some using cabinet grade granit slab drops. Be aware that cabinet grade granit has a flatness tolerance of +or-.02" per foot. That meand that cabinet cut and polished granit slab can have a valley or rise in it. A percision ground and polished granit slab or block has a tolerance of .001" per foot.

Most monument retailers can order these for you as well as lee Vally ond Grizly and others. I got mone from a local monument company and paid no shipping as it came in with an order of headstones I also cost about 10% less that Grizly. I use mine mainly to true planes and chissles.

this should be a new forum," Tidbits from Tippie"
Thanks John, I was going to order one from Grizzly
but like JJ said shipping was more than the granite itself.

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Anderson Guitars
Clearwater,Fl. 33755

Hey, Michael...Great idea! Every community seems to have a monument company nearby. I'll make some calls tomorrow and see what happens.

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JJ
Napa, CA
http://www.DonohueGuitars.com

There's a pretty affordable 9x12 plate at Woodcraft:
http://www.woodcraft.com/family.aspx?familyid=4864

It's what I use for sharpening. One of the reasons I like it better than float
glass is that it's sheer mass keeps it in place when you're sanding
something on it.

Jay

oddly enough, I just ordered one of these from Grizzly the other day.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

     I have a 24 square. 18 by 24 is as small as I can recommed. Tolerance will vary by grade. A B is usuual within .001 per foot. We have some at work that are 4 by 5 foot and have a tolerance of .00005   That is flat.
    Checking from the table saw to the granite block there was at least a .01 accuracy factor to the block. thier weight and mass alone make them great devices.
John Hall
PS check your local machine shops , they may even have on or can get you one at a decent price.

I remember reading a thread on one of the woodworking forums about a year ago that dealt with sharpening and one of the contributors mentioned that he had gone to the local granite monument company and purchased a piece of ground granite for a very reasonable price.

I stopped by the local shop this past summer which was only a few miles from my home and ended up with a piece of 1" thick marble 12" x 12" to use for sharpening. I think he only charged me about $7 or $8 for it. It was a remnant from one of their jobs. I have run my indicator over it and it has little runout. I couldn't argue with the price either.

I'll have to stop by again and see if he has anything larger. Thanks for the tip John!

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Peter

I bought one from grizzly a couple years ago. They are great, usefull for more than you think.

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Tickle your guitar daily, and it'll tickle you back.

Thanks for the precious tips guys, really worth looking into it.

I can't believe that granite from a monument company would be ground with any kind of accuracy.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

I've got one of the 9X12" granite plates from Lee Valley, and FINALLY I've got something that is actually flat! I believe their .0005" claim--I can't find any deviation with my straight edges. I use it for reference, and for sharpening (with sandpaper). I've retired the big pile of water stones I have--they were messy and they seemed to vary from stone to stone, though I spent about three times (or more) the time to lap them (over and over) as I did sharpening! The granite is great for lapping planes, too. I sure would like a larger plate, but man, the shipping is a deal breaker, and their weight is a back breaker. If you order, be sure to check the weight so you know what you're facing when the truck arrives!CarltonM38753.9781481481

I got one from a job I done, unforunatly it's 3 1/2ft X 3ft" X 1 5/8" and I can't get it off the floor!!!!!!!!!!!! Heath38754.1593055556

Yeah, I have been thinking about that too. The one I just ordered from Griz is 400lbs. I am pretty sure I can get it to my basememnt ok on a refrig dolly, but getting it up into the stand that goes with it might be a big of a challenge.   

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

   They ain't light that is for sure. I have them in a few sizes as they did throw some inspection plates out from where I work. most are under 12" but are flat .
    I know that getting them down is easier than gettng them up. So grab a few buddies and hope for the best
john

[QUOTE=old man] I can't believe that granite from a monument company would be ground with any kind of accuracy.

Ron[/QUOTE]

Not normally, no. But the same mills that produce headstone also produce index plates to the machine industry therefor some monument companies will special order them in for you.

There was a granite mill just a few miles from me. I knew the owner and some of the folks who work there, and headstones, counter tops and even floor tiles(they did some beautiful high end stuff!) aren't ground to anything other than "cosmetic perfection". In other words, if it looked fine, it was. They didn't even have machinery to measure the flatness of their work because none of it had to be certified flat.

Yes, it is the same basic machine that cuts and flattens the stone, but in the pretty stuff, the polishing stages can and will make the surface less than flat, where the surface plates are ground to a satin sheen with specialty equipment.

I had lots of off-cast bits of granite, and none were flat enough that I'd joint with them, though the were great for sharpening and such. Gave most away, but I still have a large section(about 20" x 40") that I want to inlay into one of my benches again.

Not saying you can't find a dead-flat piece at the thombstone place. All I'm saying is that don't assume all granite is flat granite.

And what's with the thread title? How does that relate to what the thread is about?!? Geeze...Mario38754.4070833333

Mario that is why I said some. It does depend on the mill and their capabilities. maybe I got lucky. Don't know, but all I did was go down to the major monument company in town and iquired. As it turned out the provided index plate to the regonial machine shops

What would the tolerance be on plate glass? I have made concrete countertops with granite tile embedded in them and thought embedding a large piece of glass in a bag of concrete could give you a nice surface with the mass required. The concrete should have some "hair" and some latex additive thrown in to prevent cracking and promote adhesion to the glass.

Kurt

Mario
Why are you allways so grumpy? Isn't a little humor good for the soul?
John Hall

I spoke to my local monument dealer. What a "posterior orifice"!!!He sounded like he wasn't used to doing work for those of us still alive. He blew me off and suggested I speak with someone who milled granite for machinists.

I politely thanked him and told him I would be using an urn for my ashes rather than use one of his monuments

On an even lighter note I came up with a few alternatives:

...take a drive to the local cemetary and look for flat horizontal headstones. Wipe off the bird droppings and sharpen blades and level fretboards. Clean it off when finished and replace the bird droppings.

...next time I visit Tippie, stop at the local Grizzly store and buy one. Drive back to Indiana with the front wheels off the ground.

...stick with glass until I find something more realistic

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JJ
Napa, CA
http://www.DonohueGuitars.com

JJ...The 9X12" granite plates usually ship at the standard rates, and you can get one quite inexpensively from Grizzly or Lee Valley. In fact, I think Grizzly may even ship their 12X18" plate at standard. They're not the ideal size for lutherie, but you can certainly use them for sharpening, and, I've found, with some careful fiddling, I can use my 9X12" to flatten longer boards like neck stock and fingerboards.

Maybe I've been especially unlucky, but I've never been able to find a flat piece of glass, except for a little 4X8" piece of double-thickness glass I got a few years ago (and it broke when I applied pressure on a surface that wasn't perfectly flat--another downside of glass!). I bought a mail-order piece of "sharpening" glass a while ago, and on one side my straight edge would rock, and on the other side, I could slip a thick piece of paper under the straight edge. That's not flat enough for sharpening! Thick float glass might be good, at least that's what I keep reading, but it seems to cost as much as the Chinese-made granite plates, so why bother? Only flat is flat enough!