Lightweight Surface Plate Cover

[Paul Jones]

This easy to build surface plate cover is for a small 12” x 18” x3” granite surface plate. The cover adds protection to the top surface of the plate and can be used as a tray for small layout tools needed at the workbench. The custom milled red oak T-shaped edging is approximately 3/4” x 5/8” in cross section and the cover is 3/16” thick red oak plywood. DAP contact cement was used to glue the 1/2” wide center section of the edging to the plywood. This produces a very strong bond and does not require any fasteners. I applied several coats of clear polyurethane from a spray can to seal the wood and protect it from oil.

The completed surface plate cover and tool tray.





A view of the bottom section of the red oak edging after gluing with DAP contact cement to the 3/16”oak plywood. The lower skirt of the oak edging fits around the surface plate and holds it in place. Note the pencil line on the 45 degree cut. When fitting the fourth and final framing part cut with 45 degree corners, I always cut longer than marked and test fit which in this case allowed the part not to be cut too short.



A cross section view of the oak edging.




Thank you for looking,
Paul

[PJs]

Classy Top and handy tray Paul. I really liked the way you have all your tools laid out on it and can set it to the side to work from it. I have a bath towel draped over mine and try not to set anything on it but mine is 18x24x3 and in my small shop its really difficult Not to set stuff on it. I like that your tray is a hard protective surface so if I do set something on it, it's better than just a towel. Thanks for the idea and tip! ~PJ

[Paul Jones]

Thanks PJs,
I would have preferred a 18x24x3 or larger granite plate. The cool thing about this cover design is the custom milled T-section rails can be scaled-up in size to provided more strength for much larger covers or the rails could be made from an aluminum T-section rails and attached to the plywood cover with either DAP contact cement or pop rivets.
Paul

[rossbotics]

Looks great Paul, You have just inspired me to do that to mine.

Thanks
Doug

[C-Bag]

+1 Paul, add me to the list of "I'm gonna do that too".

Good tip on the aluminum T edging, that I could pull off. I've been thinking about needing to put something besides the rubber mat I've got on my plate but didn't want to bodge the edges.

[DIYer]

Thanks Paul Jones! We've added your Surface Plate Cover to our Storage and Organization category,
as well as to your builder page: Paul Jones's Homemade Tools. Your receipt:

Surface Plate Cover by Paul Jones

tags: plate

[frugalolegeezer]

Hey Paul, How much does that piece of granite weight and where in the world did you come up with a 3 inch slab? Good job, I also will be making one of those.

[Paul Jones]

Hi frugalolegeezer,

Thanks. The black granite slabs are surface plates available from MSC ( https://www.mscdirect.com/product/details/00150011 ) and other tool distributors such as Grizzly. I have a Grade B surface plate of 12" x 18" x 3" and has an overall unilateral flatness tolerance of 0.0001". It weights around 80 lbs and I would prefer the next larger size of 18" x 24" x 3" but it weighs around 150 lbs. In the case of the smaller import surface plates, the shipping costs can sometimes cost more than the surface plates. I bought mine years ago from ENCO (now part of MSC) for less than $50 and when they had a special offered for free shipping.

I have a project planned in 2017 to make adjustable three point leveling pads epoxied to the surface plate bottom.

Paul

[mklotz]

Paul,

You probably know this already but let me throw it out here for the benefit of future readers.

If you mount your surface plate on three points it's possible for it to tip if a heavy object is placed outboard of the single point of support..

Three point supports should have two near-to-touching supports outboard of the single point. These structures do not actually touch or support the surface plate but rather serve to "catch" it if it begins to tilt. Normally, they are only a few thousandths shy of touching so, if the plate tilts, it can only do so very slightly and anything on the plate will not slide off.

[Paul Jones]

Marv,

Thanks for pointing out the tipping issues. There are exact ways to calculate the ideal position of the three support locations on the bottom of the surface plate. Most surface plate manufactures use a Fed spec to locate the support positions or companies such as Starrett recommend using the rule of thumb: "A surface plate should be supported at 3 points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered".

Other surface plate manufactures such as Standridge Granite mark the bottom of their surface plates to shown where it was supported during the surface lapping and inspection process and expect the owners to support the plate in the same locations.

Paul