Granite Surface Plates For A Hobbyist's Shop

At one of my favorite shopping venues 20240502_115615.jpg20240502_115620.jpg20240502_115640.jpg20240502_115633.jpg
 
They have lots of tooling machines benches20240502_124320.jpg
 
The black one is at a great price. The Rhan one looks well used, but at around 150$ it would be a good deal.
 
MikeInOr said:
From what I can tell the need for a surface plate all depends on the parts you are building and the the precision you need. For the parts I build I don't need a surface plate and have passed on some of the used ones I have found for sale.

If I was more into machining my own fixtures and accessories I could see how I would need a decent surface plate since measuring errors have a way of telegraphing and multiplying through the parts made on those fixtures and accessories. From what I can tell this path kind of inevitably leads to a surface grinder.
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Your surface grinder comment nailed it.

Basically if you don’t have access to one, a surface plate is overkill and takes up valuable space.

The problem with glass is that it’s flexible where a surface plate is not.

And while the 400x400 or 16”x16” may seem “Big enough” it’s kinda smallish.

Figure your indicator is 3-4” or 80-100mm long and add another 3” for your surface gauge, you’ve already used up half of the real estate and haven’t even put your part on.

I would want 18-24” to have room to grow.


ETA: yeah, scary man?
 
After using many surface plates of a lot of different sizes, a 12X18" is barely adequate. 18X18 is mminimal, and 18X24 is an ideal size to be big enough and small enough.
 
Dabbler said:
After using many surface plates of a lot of different sizes, a 12X18" is barely adequate. 18X18 is mminimal, and 18X24 is an ideal size to be big enough and small enough.
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Even a 12" would require me to get rid of some other tool. There's just no space in my tiny shop. Even "cold storage" for little-used tools is full up.
So this idea that everyone needs a granite plate — false! I used them at work for years, granite and cast iron, definitely know what they're for, yet in 30+ years as a hobbyist I have never needed nor really wanted one at home.

Just in case there are any beginners reading this: wait until you know you need one, then you'll know how big to get. Until that day (which may never come) you can have plenty o' fun without one.
 
I have a 12 x18 .
I find it useful for many things. Set ups of difficult items, measurements.layout. checking items for flatness.
When you have one you find uses for one BUT I think a 12 x18 or 18x 24 is more than adequate.
I believe most people can live without one.
 
A huge advantage to finding a used surface plate used locally is shipping. Grizzly offers many smallish inexpensive granite surface plates, but the shipping often exceeds the cost.

Example their grade B (+/- 0.0001") 12x18x3" (305x457x76mm) granite surface plate.
Weight is 80lbs (36kg).
The surface plate only costs $99 but the shipping adds $199. In fact shipping is the same price as the larger 18x24" and 24x24"

They do offer free shipping on their 9x12x3" (228x305mm) and smaller surface plates which weigh 40lbs or less.


I have a 12x18" cast iron surface plate, and a 9x12x2" granite surface plate. Nice to have them available but I've only used them a few times. I was given the cast iron and got the small granite for like $20 so they don't need to do much work to earn their keep. I spent 10x more for the cart that they live in.
 
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