Surface Plate Table
- Thread starter eriksalo
- Start date
Does the stone lie flat on the steel plate or are there supports in between the steel and the granite?
The stone lies flat on the angle iron. I looked at Starrett's website and some others and the best practice is to support the plate by three points, 20% of the length in from the edges. Here's a good summary:
For my purposes, I decided the above was overkill. I'm a hobby shop and don't need to ensure 0.00001" accuracy on my plate, the workbench is probably flat enough for my actual needs. However, if you want to do it right, I believe the three point method above is the best practice.
"Another common cause for calibration variation is a plate that is improperly supported. A surface plate should be supported at three points, ideally located 20% of the length in from the ends of the plate. (Erik Note: These should be the same three points the plate was supported by when it was made in the factory). Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered. Only three points can rest solidly on anything but a precision surface. Attempting to support the plate at more than three points will cause the plate to receive its support from various combinations of three points, which will not be the same three points on which it was supported during production. This will introduce errors as the plate deflects to conform to the new support arrangement. If the plate is properly supported, precise leveling is only necessary if your application calls for it. Leveling is not necessary to maintain the accuracy of a properly supported plate."
For my purposes, I decided the above was overkill. I'm a hobby shop and don't need to ensure 0.00001" accuracy on my plate, the workbench is probably flat enough for my actual needs. However, if you want to do it right, I believe the three point method above is the best practice.
A surface plate is really just a very flat surface. The primary use (and my use) is for measuring metal parts. There's a useful measuring tool called a, "cadillac guage" that really only works in conjunction with a very flat surface.
While you can buy smaller plates than mine, you can also purchase much larger plates for measurement and layout of large things. Many shops have surface plates larger than 4'x8' and they are more than a foot thick.
While you can buy smaller plates than mine, you can also purchase much larger plates for measurement and layout of large things. Many shops have surface plates larger than 4'x8' and they are more than a foot thick.
Falcon67
Well-known member
Very flat - as in super flat. Inspection grade 2x3 would be around +/- .0001" flat across the surface. You can buy 'em down to around 50 millionths IIRC.
Some are very big.
arkangel06
Banned
Nice plate and nice welds.
dolfans
Well-known member
I worked at Starrett and have seen those plates. My brother use to inspect them to make sure the specs were correct
Steve from Socal
Well-known member
Actually you should consider using a kinematic mounting system( 3 points) this will reduce the twisting effect and maintain the flatness of your surface plate.
Nice fab work on the cart.
Steve
Nice fab work on the cart.
Steve
e-tek
Well-known member
Hmmmm, I'm not convinced it's all that flat....
arkangel06
Banned
arkangel06
Banned
A quality built one by a skilled craftsman.
nate379
Banned
srmofo machinists are **** about it being perfect.
I was working on something with my brother (he is a machinist) and I thought he was going to **** a brick when I told him it was close enough because it was off like 1/16"
I was working on something with my brother (he is a machinist) and I thought he was going to **** a brick when I told him it was close enough because it was off like 1/16"
When I do woodworking, I maintain tolerances of between 0.005" and 0.010".
Metal working is much better, I strive for 0.0005" but will accept 0.001".
Maybe if it was more than a hobby, I would be compelled to value speed over accuracy but I'm in a position where I can execute projects to my own standards. Many people ask me to make things for them. I accept jobs now and then but I never take any money beyond materials and never promise a schedule. They get it when I'm happy with it and I don't provide progress reports.
You won't improve what you don't measure. While I've spent my career designing computers I have a degree in mechanical engineering and learned in my first job out of college that good parts are made by the ability to make accurate measurements. If you have a mill, I propose you need a good surface plate.
Metal working is much better, I strive for 0.0005" but will accept 0.001".
Maybe if it was more than a hobby, I would be compelled to value speed over accuracy but I'm in a position where I can execute projects to my own standards. Many people ask me to make things for them. I accept jobs now and then but I never take any money beyond materials and never promise a schedule. They get it when I'm happy with it and I don't provide progress reports.
You won't improve what you don't measure. While I've spent my career designing computers I have a degree in mechanical engineering and learned in my first job out of college that good parts are made by the ability to make accurate measurements. If you have a mill, I propose you need a good surface plate.
ohh its used while milling a project out. I was just trying to imagine welding some angle together it had to be perfectly flat.
thinking to myself Ive always just used the floor.I can understand the perfectionist aspect, I like things done the right way also, I just dont do much metal work....yet. hopefully in the next few years I can start shopping for some home equipment, just too many projects on the table as it is right now.
nate379
Banned
My tape measure don't read that small! 
+- 1/8" is plenty fine for any woodworking I do!Used by tool makers and machinists to check parts to very very close tolerances. Like comparing piston skirts to each other or laying out parallel lines. You really need a hight gage or a surface gage in order to use one. They can come in handy in the home shop but very few will ever need one.
http://www.inversesolutionsinc.com/graphics/Gaging.JPG
http://t3.gstatic.com/images?q=tbn:...elinehair.com/home/height_gage_scribe.jpg&t=1
http://www.mfg-support.com/images/gallery/HeightGage.jpg
http://www.cncind.com/assets/images/height_gage_4.jpg
http://www.cnccookbook.com/img/MillStuff/KurtViseStop/P7083541.JPG
http://www.cnccookbook.com/img/LatheStuff/TailCamlok/P1010353.JPG
Last edited:
russlaferrera
Well-known member
He would love to work for NASA. They have specs +/- .00005 @ 70*
Those are some perty coarse specs in some circles. Take a look at the nozzles on your inkjet printer. They are measured in microns.
http://findarticles.com/p/articles/mi_m0HPJ/is_n5_v39/ai_7036983/?tag=content;col1
lg
no neat sig line
buildyourown
Well-known member
- Joined
- Jan 8, 2010
- Messages
- 185
Nice looks just like mine except I did mine when I was just learning to stick weld. 8yrs later, I'm a MUCH better weldor and am embarrassed to have people look at it.
The 24 x 36 plates are nice. You get spoiled.
The 24 x 36 plates are nice. You get spoiled.