# Which surface plate?



## gi_984 (Dec 16, 2012)

Getting set up to start scraping and would like advice on purchasing a surface plate.  I'm looking at a A grade 24X36(?) from Enco.  Plan on building my own stand from wood with casters to roll around.


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## turbotadd (Dec 16, 2012)

Just a word of caution, you'll probably want to build the frame out of steel as wood will move, and a surface plate's flatness depends on a rigid 3-point mount. I'm sure Richard will elaborate. I just got a 24" x 36" double ledge from a local auction, can't imagine what shipping would cost from enco. They often show up on CL too.


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## Richard King (Dec 16, 2012)

Tadd took one of my classes....Go for it Tadd and teach.    I always ask my students to pass on my knowledge and teach.   You know the answer.  Don't be shy.


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## DMS (Dec 16, 2012)

If you have the space, larger ones show up for pennies on the dollar around here. I have one of the cheap import ones. It works OK. I got it because I wasn't sure how much I would use it. If I did it again, I probably would have gone with a Starrett. I have a 12x18, which has been large enough for what I have needed it for (reference for scraping, and for layout). That 12x36 is gonna be _heavy_, so be prepared


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## turbotadd (Dec 16, 2012)

When you look at a big surface plate you think surely that thing can hold its shape no matter what right? Not so. In the class that Richard taught this summer, we had a guy from a local company stop by and show us how he calibrates surface plates. We had a 4' x 4' plate that checked out pretty good, but we heard stories of plates that weren't mounted properly or abused, and I was amazed with how far from flat they can go. Granite will creep just like any other material, so supporting the weight of the plate evenly is crucial to maintaining flatness. Ever sit on a tippy bar stool you know that it's virtually impossible to get even weight distribution on all four legs. Supporting on three points is critical. If you do design your own frame, plan for three support points where you will put 2" or so diameter rubber disks (1/8" or so thick) that the plate can rest on. This pic illustrates the idea http://www.flickr.com/photos/gomezaddams/2243574164/
I also found this PDF, see page 5 for dimensions. 
http://www.evenfallstudios.com/woodworks_library/fed_spec_GGG-P-463c_for_granite_surface_plates.pdf


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## gi_984 (Dec 17, 2012)

Thanks for the info.  Yes, I've been hunting the craigslist ads without any luck.  My (almost) last resort is to order from Enco.  I've considered even buying a used plate locally and paying to have it re-ground and calibrated.  Problem is nothing decent has been come up so far.


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## Richard King (Dec 18, 2012)

A couple of other points.  The spec sheet Tadd gave you is for new plate mfg.  If you buy a plate from Enco or who ever look at the bottom and if the rubber pads are glued to the plate or there is X's at 3 locations put you rubber pads there as that is where they had it sitting when they lapped.  It may vary a little.  I have always been taught to use 30% from the end and sides on the 2 pad end and one at 30% and directly in the middle on the single end.  I use to sell Starrett plates and they use 25%, an optical machine building is know uses 28%.  Many precision machines are built using 3 points, take for an example a Swiss made Sip Jig bore.  It sits on 3 points, but the 2 sides end they have the points under the columns where the heaviest area's are and the other is 30% from the other end directly under the table.   So the spec sheet isn't for all uses of the Kinematic mount principal or 3-Points.   I also like to see you put adjustable leveling screws around the perimeter of the plate with a light touch, so when you set something heavy on the plate especially on the single point end it won't twist. .  Many can debate the spot if your a scientist in a lab looking for billionths, debate  but for the average machine shop owner use 30% it's easier to remember and you can hold millionths.  If you make a stand, make it so you can adjust it level with the earth too. Thanks Tadd for your help.


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## gi_984 (Dec 21, 2012)

Richard and Tadd,
     Thanks again for the information.  I just ordered the surface plate from ENCO.  Got 20% off plus free shipping!  I'm going to weld up a stand.  What color and brand of marking fluid do you like for scraping and on the surface plates?


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## Richard King (Dec 22, 2012)

I have used all the different brands and I prefer water based brand named Canode 2243.  My favorite before that was Dykem High Spot blue, but it would stain your fingers and the surface plate.  I was doing some scraping seminars at GM in Indianapolis when I first saw the Canode and at first I did not like it, but I could go to the sink and wash off my hands and no stained fingers was wonderful.  You can buy it from DAPRA, ES Dyjak and a company called Volt who advertise on the net.    The Japanese and Taiwanese have a great product that looks a lot like shoe-polish and is red, but I have never seen it sold in the USA.  The Canode also comes in different colors; Blue, Red, Orange, Yellow.  They used to make black and white but have discontinued those colors.  I use the Yellow as a red lead substitute and dilute it with window cleaner and I spread it and the blue ink with foam paint roller.  The rule of thumb when spreading all the inks you roll on an even coat so you can see the surface thru it.  If it is on to thick and you can't see thru it, the ink will smear.   Another thing is you always run your hand or fingers thru it so you can feel any dirt that may be in it.  You can feel the dirt with your hands, but if you wipe it with a rag you can impart dirt and lint into it.  That's why my hands would get dirty and stained using the Dykem.  If you use the Dyken use a foam roller or a piece of leather to spread it.  Maybe Tadd has some pictures he can add.


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## turbotadd (Dec 22, 2012)

Sounds like you got a sweet deal from Enco! Can't beat free shipping on a plate. Here is a picture of the plate we used in class. I use the Canode water based stuff too, the Dykem is used for pranks like the old anti-seize under the toolbox drawer pull because as Richard says it never comes off! Its a few bucks for a small bottle. I use the 4" wide foam ~1" diameter roller to blue the plate like the one pictured on the left. You will end up with two sections of blue on the plate: first one is where you drizzle the blue and saturate the roller - this will be too thick to use for spotting. Second area is where you apply blue to the plate with the roller, this is where you will blue up the part. As Richard said it is imperative to pull your hand across the blue to wipe the little bits of crud that will inevitably make there way in there. You'll be able to see the littlest bits of crud show up when you blue your part. They show up as little swirls of blue that look like they make by the tip of a needle.


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## gi_984 (Dec 23, 2012)

Nice picture Tadd.

Chris


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## Richard King (Dec 24, 2012)

joelaycheck said:


> Would a grade B plate be good for the home shop scraper or is grade A required



What do you plan on rebuilding?  I have Grade AA plates, but I scrape jig bores and CNC machines and I need to scrape my straight edged to that accuracy..  But the mfg. says I need to use  my AA  in a temp control room which I don't.  

If you are going to be using it in your garage to scrape occasionally a conventional machine  Grade B should work for you.  (see below)
A Grade B is 1/2 the spec needed.   


Grade B +/- .0001" /12"
Grade A +/- .000050" / 12"
Grade AA +/- .000025" / 12"

When we scrape machines we have 2 standards
Conventional;  Engine lathe, vertical and horizontal milling machine, surface grinder,  shaper, planer, etc    accuracy +/-.0001" /12"   
I generally just say .0002 / 12"  and skip the +/-/
Precision;  Jig bore, jig grinder, CNC machining centers, precision surface and cylindrical grinders, etc.  accuracy  +/- .000025" / 12"
I generally just say .00005" / 12"  and skip the +/-/

Price can be a factor too as a AA compared to a B, the price is 50% to 75% higher.


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## gi_984 (Dec 30, 2012)

The plate is 425 pounds on a pallet according to the trucking company.  Will be coming next week.  I have a loading dock at work where it will be delivered.  Simple process to then put into my truck.  Would hockey pucks work for the three support points?


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## Richard King (Dec 30, 2012)

gi_984 said:


> The plate is 425 pounds on a pallet according to the trucking company.  Will be coming next week.  I have a loading dock at work where it will be delivered.  Simple process to then put into my truck.  Would hockey pucks work for the three support points?




I would think so, but if they have some with it use them.   Pucks are how thick  1"? Might be a bit to high.


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## gi_984 (Jan 5, 2013)

Holland freight delivered the plate strapped to a pallet.  Had them deliver it to the loading dock at my worksite.  I was able to lower the dock and move it onto my truck via a pallet jack. Got it off the truck and into the shop with my engine hoist and leveler.  Anyone considering ordering this size of plate needs to be PREPARED!  Now to building a suitable cart.


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## 4GSR (Jan 5, 2013)

Richard,

You mention using a piece of leather to spread the media.  I've always used a piece of dense felt to spread the media.  Dad always did it this way and I guess that's how he was taught.  I will agree, felt will leave lint once a while and have taken impressions smeared from the lint.  I'll have to try the leather, I have a few belts that are too short for me now, I'll cut one up and try it.

Ken


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## Richard King (Jan 7, 2013)

I use a foam ink roller on V's and Flats and a paint brush with 60% of the bristles cut off to get into dovetails.  I've used hard felt but as you said it leaves lint.  I have used a tongue from an old pair of boots and the thumb off an old glove.   If you use the Canode Water based Inks (blue for blue and Yellow for the red lead highlighter.  You can wipe things off with your hand feeling for the lint and dirt and I can't remember the last time I had blue stains on my fingers from using the Dykem High Spot Ink.   But as I have said many times.  I don't care what you use for a scraper, your equipment, your techniques, your ink as long as you get the same results in the same amount of time...  That's all that really mattesr.


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