Where to get a perfectly flat surface for sanding the bottom of a saddle?

[ii Cybershot ii]

Turns out my marble counter top isn't flat. When I place the saddle at different places on the counter top and shine a back light under it, I can see various amounts of light coming under it.

Where can I pick up a perfectly flat thing or piece of something for this purpose? Preferably under $10... Thanks.

[HHP]

Thought most people used a sheet of glass.

[ii Cybershot ii]

Originally Posted by HHP

Thought most people used a sheet of glass.

Brilliant, this is what I wanted to hear!

[ZekeM]

Or a granite block that is actually flat. Somewhere had some on sale a while bak but I dont remember where.

[MikeVB]

Finding a flat surface isn't nearly as big a problem as holding and maintaining it perfectly vertical.

After struggling for years with hand sanding the bottom of saddles, I started doing what I saw several luthiers do in person. I walk over to my little belt/disc sander and just use that. Faster and promise you can't tell the difference sonically. But you can ruin a saddle or two (and a knuckle) if you're not vigilant.

[Ed422]

I went to a local tile store and asked if I could go through their trash. I found a nice 12"x12"x.25" tile with a little chip out of the side. Then a buddy who works for a stone countertop company brought home a 1 inch thick sink cutout slab. I can glue down whatever grit paper I want. Either is great for sharpening chisels, good flat saddle bottoms, etc.

Ed

[dekutree64]

Originally Posted by Pater Familias

Finding a flat surface isn't nearly as big a problem as holding and maintaining it perfectly vertical.

Yup, as well as getting even pressure along the whole length so you don't end up with a slight hump or hollow along the bottom of it.

I use an 8x3" extra-extra-coarse DMT dia-sharp stone, which is also extremely useful for flattening the backs of new blades and regrinding bevels and such, and handy as a sanding block for wood too $77 at Lee Valley. Although if you're only doing setup work and not any actual woodworking, then it would be excessive. Glass or plexiglas or granite with sandpaper works fine.

[fazool]

I got lucky and have a couple granite chemistry lab bench tops I bought when a company was moving.

[ZekeM]

Originally Posted by dekutree64

Yup, as well as getting even pressure along the whole length so you don't end up with a slight hump or hollow along the bottom of it.

I use an 8x3" extra-extra-coarse DMT dia-sharp stone, which is also extremely useful for flattening the backs of new blades and regrinding bevels and such, and handy as a sanding block for wood too $77 at Lee Valley. Although if you're only doing setup work and not any actual woodworking, then it would be excessive. Glass or plexiglas or granite with sandpaper works fine.

Just got me a course/extra coarse off eBay for $60. There are a lot on there. I hadnt thought about flattening saddles and such with it. Great idea Dennis !

[dekutree64]

Originally Posted by ZekeM

Just got me a course/extra coarse off eBay for $60. There are a lot on there. I hadnt thought about flattening saddles and such with it. Great idea Dennis !

Make sure it's actually flat first. I have a couple of the smaller double sided stones and both are a little bit curved... no problems with the 8x3" single sided ones, though.

The XXC is a lot better than XC, IMO. Coarse enough to use on wood, much faster for everything, and either way you're going to need something finer afterward for sharpening. I go right to XF as the second step. Doesn't take long at all to smooth out the scratches, even on the large surface area of a plane iron back (I only do the last inch or so, not the entire thing). Then the diamond lapping films from Lee Valley, although they're wearing out a bit quickly so I may switch to a water stone for the final polishing. Trevor Gore says he uses an XXF dia-sharp for the final pass, but mine leaves much too rough of a surface... I think I just need to use it more and get it worn in. Or sell it since it was expensive :P

[printer2]

How do you know the bottom of a saddle slot is perfectly flat?

[bnjp]

I take a different approach. I built a jig that allows me to hold the piece and move a block that is loaded with sandpaper.



This setup works every time. Just email me if you want any better photos, etc. and as for how I know if the saddle is flat, I use a little X-acto square that tells me pretty much everything I need to know.

[ii Cybershot ii]

Thanks for all the replies guys...

So I also called Stew-Mac and asked what to use, or if they had a useful tool. They gave me a list of things from their store that I could use for this, one of which was their 6" fret leveler... which I happen to have!

They recommended putting the leveler in a vise, but I just held it with my hand. I put the saddle up to it and with very light and even pressure I slid it against the leveler... it took about 30 seconds of this and afterwards I held it up to the edge of my Stew-Mac fret rocker against a light and BAM, PERFECTLY flat.

Hopefully anyone with a question like this in the future will happen upon this thread because there are a ton of great answers in here.

Thanks again.

[ZekeM]

Originally Posted by dekutree64

Make sure it's actually flat first. I have a couple of the smaller double sided stones and both are a little bit curved... no problems with the 8x3" single sided ones, though.

The XXC is a lot better than XC, IMO. Coarse enough to use on wood, much faster for everything, and either way you're going to need something finer afterward for sharpening. I go right to XF as the second step. Doesn't take long at all to smooth out the scratches, even on the large surface area of a plane iron back (I only do the last inch or so, not the entire thing). Then the diamond lapping films from Lee Valley, although they're wearing out a bit quickly so I may switch to a water stone for the final polishing. Trevor Gore says he uses an XXF dia-sharp for the final pass, but mine leaves much too rough of a surface... I think I just need to use it more and get it worn in. Or sell it since it was expensive :P

I've checked and it is dead flat on both sides. The XC on my duo sharp is 220 which should do for a saddle. For sharpening I only use the duo sharp for primary flattening or reforming the main bevel and flattening my waterstones. After that I go to the waterstones. I go 1000, 4000, and polish with 8000.

[mc1]

it would be neat if there were a little vise mounted to wheels. the vise would hold the saddle vertically, and the wheels would allow it to move back and forth over sandpaper. it wouldn't even need to be a vise, i suppose, as long as it had a flat surface at 90 degrees one could hold the saddle against.