Surface Plate

I use the cast iron top of my table saw for things that don't fit on my tiny 6" x 9" cast iron surface plate.
 
Keep in mind that granite countertop is not machinist flat, its "pretty good". Don't expect 0.001" accuracy. Better than nothing, and the price/performance ratio is good!

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I believe a good thick piece of plate glass is actually a pretty good surface, or so I have heard. Needs to be backed up against something flat and rigid regardless of thickness.
 
I have a 9"x12" surface plate from Little Machine Shop. It was inexpensive - $30 or $40 I think. It has been more useful than I expected. But yes, it is not essential. Tooling is essential.
 
You can also potentially use polished granite tiles from your local big-box store. Yes, it is not likely as precision ground as a proper plate but they are quite flat. I actually use a ~14" square one as the backer for 3M abrasive film to sharpen my straight razors.
 
I might be a bit odd, but I absolutely love my surface plates and would consider both of them essential. I'm really good at blowing past dimensions, so layout lines are a must for me. Dykem + a height gauge + a surface plate lets me do all of my layout work very quickly and quite accurately.

I also have a second cheapy surface plate that I use for sanding because I'm a bit obsessive when it comes to flatness of parts.
 
Like Badabinski, I like doing layout with the ht. gage on the surface plate. But being a bit lazy I'll often just pencil & paper the readings I need to follow on the DRO. More prone to errors though. I've found putting the origin (0,0) into both the abs & inc locations saves a lot of messing around when I screwup and loose it on the abs. Planning the sequence of operations ahead of time has improved my results. Found that out after discovering how hard it is to get there when I've machined away my reference.
 
Larry$ said:
Like Badabinski, I like doing layout with the ht. gage on the surface plate. But being a bit lazy I'll often just pencil & paper the readings I need to follow on the DRO. More prone to errors though. I've found putting the origin (0,0) into both the abs & inc locations saves a lot of messing around when I screwup and loose it on the abs. Planning the sequence of operations ahead of time has improved my results. Found that out after discovering how hard it is to get there when I've machined away my reference.
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I thought I was the only one that machined away the reference...leaving me to wonder "now what?" :laughing:
 
You need a reasonably flat surface for layout but it doesn't need to be surface plate flat for most home shop jobs. I have a small one in my Michigan shop and it's handy but I don't think I've ever done anything that really needed it. I'd buy the height gauge first and use it with a granite/marble countertop piece for layout.

That being said, if you don't mind something that's not perfect you can get used or new surface plates pretty cheap. I think I paid about $100 for mine, it's small but works for most of my stuff.

John
 
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