"Surface Plate" Workbench

**Crusty** · Jun 29, 2019, 12:30 PM

I found a slab of granite counter top leaned against the dumpster at my local hospital and after breaking it into two pieces because I couldn't lift it as a single piece I brought it home. I made a stand using lumber and hardware I had left over from previous projects and purchased 15 ½" lag screws which I installed in the top edge of the stand as adjustable plate supports. Using a long straight edge and a feeler gauge I was able to adjust the top within a tolerance of .010" overall and less than .005" in smaller areas, and this level of precision will be more than adequate for most of my projects. Now I've got an adequately flat and sturdy work surface that cost me the price of 15 lag screws and it will be an enhancement to my capabilities. The makeup mirror in the background (also from the dumpster) is handy to direct and focus sunlight onto my work so that I can see what I'm doing better.

"Surface Plate" Workbench-work-bench.jpg

**neilbourjaily@gmail.com** · Jul 7, 2019, 05:38 PM

I love it! That's like my cylinder square, a wrist pin from a CAT big diesel. It cost me some nice talk and a fish through the recycle bin at my local CAT mechanic.

**Crusty** · Jul 7, 2019, 06:08 PM

I actually got to use it today for the first time and it makes my life better. I bought a cheapo HF machinist tool chest and it had separate locks (and keys) for the top and the front drawers cover and I modded it by making a couple of spring loaded pins that pin the front cover closed when the top is closed. Finding things (such as lock keys) becomes increasingly difficult these days and I've eliminated the need to find at least one key plus the new tool chest has already gone a long way towards centralizing and organizing a bunch of my small tools. It was a pleasure to do all that on a flat, solid work surface. That HF wooden tool chest is not bad (~$65) though when you get it you may have to glue or nail some things back together, but like I said it's not bad and the savings over a pro tool chest is huge. I've got a diamond saw blade on the way and when it gets here I'm going to try and clean up the broken edge on the work bench.

**Toolmaker51** · Aug 2, 2019, 11:01 PM

top within a tolerance of .010" overall and less than .005" in smaller areas certainly acceptable for lots of work.......but if you'd care to improve that down the road, supporting by the Airy Points with [could] reduce it to a minimum. If adjustments proved to reduce it when built, I'm convinced Airy calculations will be successful.
https://en.wikipedia.org/wiki/Airy_points

**DIYSwede** · Aug 4, 2019, 10:01 AM

Now - this is qualified nit-picking, as the difference would be very minute to Mr. Crusty:
-Umm, don't you mean the Bessel points (at .559 L)? Airy points (at .577 L) keep the ends vertical,
Bessel points gives minimum deflection along the entire length.

1 cent
Johan

**Toolmaker51** · Aug 5, 2019, 09:32 PM

Originally Posted by DIYSwede

Now - this is qualified nit-picking, as the difference would be very minute to Mr. Crusty:
-Umm, don't you mean the Bessel points (at .559 L)? Airy points (at .577 L) keep the ends vertical,
Bessel points gives minimum deflection along the entire length.

1 cent
Johan

Possibly. It could be advertising copy mistakes, subbing Airy for Bessel. I don't recall seeing "Bessel" anywhere but engineering texts. Mr. Airy got himself a better agent.
Like tap handles among plumbing fixtures. http://www.homemadetools.net/forum/t...472#post139154

**Crusty** · Aug 6, 2019, 11:49 AM

Not wanting to become involved in any lofty discussions, I just used a long straightedge in many positions across the surface and then probed with a feeler gauge under it to determine the approximate deviations. I do have an actual 12"x18" machinist's surface plate if I ever need to measure to better accuracy than I can machine for some reason. It's working well for me and it's a quite nice surface to work on (but not for any hammering). I did buy a Dewalt diamond blade for my circular saw to clean up the ragged edges and it worked astoundingly well.

I thought that I could reduce small deviations by providing adjustable point support at many locations underneath the slabs but the granite proved to be too stiff for this to work.

**Toolmaker51** · Aug 10, 2019, 09:08 AM

The mention of Airy/ Bessel weren't to complicate your secondary plate.
I for one, often find myself posting to 'lurkers' that follow ongoing discussions, unwilling to participate but interested in solutions. There being 16k something HMT'ers, yet so few are recognizable.