--- On Fri, 8/26/11, Wonk <tiwonk@yahoo.com> wrote:
From: Wonk <tiwonk@yahoo.com>
Subject: [gingery_machines] Re: Surface plate support
To: gingery_machines@yahoogroups.com
Date: Friday, August 26, 2011, 5:21 PM
Well Dave you can turn off the flames now! After reading your posted digest article, I see that my statement that temperature does make a difference is true! I quote>>>>"
No flame intended just stating fact. A surface plate is calibrated at the point of manufacture in a controlled enviroment. when setup in the shop it is to be used in is should be recalibrated. Inspection grade surface plates should be a similar enviroment. This is not or may not be the case depending on the required use.
Surface plate care
Support. Whether large or small, all surface plates must be supported at the same three points used for support during its manufacture. From the user's perspective, if you don't mount the plate using the same three points, the plate will settle differently and possibly be out of tolerance. Three supports are used because it's physically the only way to repeatably support any static object without the weight shifting from one leg to another.
Not all surface tables give you these locations so best guess is in order.
Care. Laboratory-grade plates should be kept in a controlled environment of between 68° and 72° F and 40-percent humidity.
Key word here is should, depends on your intended use. A surface plate is used as a flat surface for inspection and is calibrated for flatness and repeatability only. It is not a measurment tool. It creates a plane to take measurments from.
A monthly inspection using a repeat measuring gage is advisable. Some labs do this every day or every week, depending on how they use the plate. " End quote.
Not even useful for the home/hobby shop.
I also see that it is recommended to follow the manufactures method of support to which you say "is not needed". and support can be X4
If you don't know how the plate was manufactured how you support it is up to you. Use 3, 4 or 6 or even 100 if it suits your fancy, for the home shop will it make a difference, no. You'll have this problem with Chinese plates, or so I've heard. If you look at the Grizzly tools, Harbor Freight etc. most use 4 point mounting. Same table legs used to mount the tool grade and the inspection grade is the same.
Again I say you cannot always believe what is posted here on the internet!
I know you didn't just say I didn't know what I was talking about, right.
Please drop the thread as it is likey to become a flaming war!
Subject will be dropped no need to start a cranking the heat up. but if you'd like to continue off group I'll bring up the subject with the certification group at work and give your their thoughts. I was just stating, for the home/hobby shop it will probably not matter which table you get or how you set it up.
Wonk
--- In gingery_machines@yahoogroups.com, David Patterson <odd_kins@...> wrote:
>
> http://www.qualitydigest.com/aug03/articles/03_article.shtml
> Wonk I work in an inspection department and have been using granite surface tables for about 40 years. The key is temperature stability. As long as you maintain an even temperature you table will be as accurate as is needed, regardless of temp., within reason anyway. inspection rooms are temperature controlled for only one reason. and that is to maintain the accuracy of all the inspection tools an the stability of surface table. A laboratory grade is flatter than a toolroom grade. Laboratory tools have a more controlled enviroment to elimiate any deviation of the inspection tools. Calibration of inspection tools take place in this type of enviroment. Calibration of a surface table takes place in the enviroment it is used in. A laboratory grade surface table used in an 80 deg temp can be just as accurate as one used in a 50 degree temp. the temerature change effects the height gage and rulers used to measure the part. Colder temp
measuring tools
> shrink, higher temp and the measuring tools grow. But the table in a stable enviroment remains flat. The difference between a toolroom and inspection grade is so slight in home shop use will make little to no difference if used for building tools or patterns. if using for accurate inspection of parts, buy a Starrett inspection grade and setup and calibrate per instructions and keep the room climite controlled. Â
>
> Dave Patterson
> odd_kins@...
> http://home.comcast.net/~oddkins/foundry_home.html
>
> --- On Fri, 8/26/11, Wonk <tiwonk@...> wrote:
>
>
> From: Wonk <tiwonk@...>
> Subject: [gingery_machines] Re: Surface plate support
> To: gingery_machines@yahoogroups.com
> Date: Friday, August 26, 2011, 11:42 AM
>
>
> Â
>
>
>
> Were still talking apples and oranges! This thread started due to someones desire to not use a grade B plate and wanted accuracey of AA in the home shop. See a google search for the differing grades all say in a controlled inviroment except B.
>
> YMMV?
> OVERALL FLATNESS
> The overall flatness specifications of STANDRIDGE Granite products meet and surpass the requirement set forth by Federal Specification GGG-P-463c. This publication defines the three standard grades of tolerance for surface plates as follows:
> AA - Laboratory Grade:
> For high precision operations in consistent temperature gauging rooms and metrology departments
> A - Inspection Grade:
> For general use in quality control areas
> B - Toolroom Grade:
> For shop work and production checking
>
> You cannot believe all that is read on the internet but the federal spec's are available!
>
> Wonk
>
> --- In gingery_machines@yahoogroups.com, David Patterson <odd_kins@> wrote:
> >
> > For what is done at home, about the only precaution neede would be to keep the surface table out of direct sunlight. If you build a seperate room that is well insulated keep it there if you need. North side of building may be best with an sealed/insulated door. But for a 3' X 4' table that is used for building parts/tools, this would be overkill. If you use the table for accurate inspection or layout The precautions maybe worth while. I personally would not go through all that, put the table in the back corner of the shop and start building. Tool room or inspection grade would work for me. Which ever is on sale when I'm ready to buy.
> >
> > Dave Patterson
> > odd_kins@
> > http://home.comcast.net/~oddkins/foundry_home.html
> >
> > --- On Thu, 8/25/11, Wonk <tiwonk@> wrote:
> >
> >
> > From: Wonk <tiwonk@>
> > Subject: [gingery_machines] Re: Surface plate support
> > To: gingery_machines@yahoogroups.com
> > Date: Thursday, August 25, 2011, 5:49 PM
> >
> >
> > ÂÂ
> >
> >
> >
> > Dave how does one depend on a slow change in temperature in the home shop? My shop is mostly uninsulated and I provide heat as needed in the winter but during these hot days it sometime gets to the days high rather fast as the sun emerges from the trees and hits the building. I have seen it go from 55 to 75 in a couple of hours. At these swings my surface plate moves considerably although might not bother some, but the topic was very close tollerance. I make do and have many things I've made work fine but maybe not to rocket spec's!
> > For my purposes a grade B surface place works as good as a grade A since I can't depend on temperature swings! Even if the plate stays flat the measuring devices change so we each must rely on some error during our homebrew machining and correct as best we can for the conditions. The world is not perfect and neither am I.
> >
> > Wonk
> >
> > --- In gingery_machines@yahoogroups.com, David Patterson <odd_kins@> wrote:
> > >
> > > If the temp changes gradually, a flat table will stay flat. Temperature changes from one end to the other will cause the table to loose it's accuracy. Inspections rooms are kept at about 68 to70 degrees because inspection tools are calibrated at this temperature. As soon as you remove it from the inspection area, don't measure the part anymore. The surface table is still flat but a height gage measuring 24" off the table will change height with the temperature change, the surface table may be slightly larger or smaller depending on the temp but with a uniform, gradual change it will stay just as flat.
> > > ÂÂÂ
> > > Dave Patterson
> > > odd_kins@
> > > http://home.comcast.net/~oddkins/foundry_home.html
> > >
> > > --- On Wed, 8/24/11, Wonk <tiwonk@> wrote:
> > >
> > >
> > > From: Wonk <tiwonk@>
> > > Subject: [gingery_machines] Re: Surface plate support
> > > To: gingery_machines@yahoogroups.com
> > > Date: Wednesday, August 24, 2011, 9:38 PM
> > >
> > >
> > > ÂÂÂ
> > >
> > >
> > >
> > > Temperature is important due to the fact that if you measure and lay out something on a cold day, the measurement will change if a hot day. A good machine shop will have a steady temperature where the surface table is located. I've installed many HVAC systems in such places over the last 40 years and it wasn't for the comfort of the employee! Same reason you heat or cool parts to make a close tollerance fit! Things move when temperatures change!
> > >
> > > Wonk
> > >
> > > --- In gingery_machines@yahoogroups.com, David Patterson <odd_kins@> wrote:
> > > >
> > > > A surface table will hold it's accuracy regardless of temperature. As long as the change is gradual and uniform. having part of the surface table in the sun and part in shade, or having the whole thing in front of a window getting full sun where the temperature change is rapid, is a bad thing.ÃÆ'‚ Pick a dark corner of your shop and addÃÆ'‚ enough lights to remove shadows. If kept clean and waxed, I used johnsons floor wax, you can use it a glueup table for making patterns. Also 4 point support works as long as the supports are adjustable and have a rubber pad under each support.ÃÆ'‚ÂÂÂ
> > > >
> > > > Dave Patterson
> > > > odd_kins@
> > > > http://home.comcast.net/~oddkins/foundry_home.html
> > > >
> > > > --- On Wed, 8/24/11, Wonk <tiwonk@> wrote:
> > > >
> > > >
> > > > From: Wonk <tiwonk@>
> > > > Subject: [gingery_machines] Re: Surface plate support
> > > > To: gingery_machines@yahoogroups.com
> > > > Date: Wednesday, August 24, 2011, 10:16 AM
> > > >
> > > >
> > > > ÃÆ'‚ÂÂÂ
> > > >
> > > >
> > > >
> > > > Unless you can control the temperature of where your surface plate lives and have a way to hold that temperature the plate might not give you true accuracy no matter how good it is. As a hobby machinist this seems non doable. My shop has a 50 deg F temp swing from summer to winter when I'm out there working, and probably much more when I'm not. Temperature along with dust and other problems plague most of us so how good is good?
> > > >
> > > > Wonk
> > > >
> > > > --- In gingery_machines@yahoogroups.com, Jim Ash <ashcan@> wrote:
> > > > >
> > > > > I didn't mean to denigrate the grade B surface plate. My concern was that the lower tolerances on it (as compared to an A or AA plate) would possibly approach bad enough to contribute negatively to my work, and I wouldn't really have a good way to find out how good is good or how bad is bad. I originally bought it with the expectation that even a grade B plate would probably be an order of magnitude better than I would care about for hobby machining and the Gingery road.
> > > > >
> > > > > Since I posted my original inquiry, I've done some reading/web surfing on the subject. A plate should be supported properly and calibrated while using those supports. Changing the support system changes the shape of the sag and could make it out of tolerance (admittedly, I haven't seen this quantified). A calibration sheet should also be included with the plate to indicate how it was supported during calibration, which should be used for the final setup. Mine did, but the paperwork got moved somewhere away from the plate to points unknown. Some plates have markings on the bottom indicating the support points, but mine doesn't. One claim (I think from a pissed US manufacturer) is that the surface plates coming from China haven't got this documentation and aren't traceable back to a NIST standard. The questions remain - How good are they and how much do I care?
> > > > >
> > > > > The Feds have a standard (http://www.vermontphotonics.com/FlatnessSpec.pdf) which I can't say I've read, but they do supply a suggested mounting which I'll probably use. There's a point where you've gotta decide for yourself how much reading and cogitatin' you're going to do versus just doing it and seeing what happens. I'm way past that point, so I'm just going to pick some mounting points and call it a win. Still, I find the reading interesting lunchtime activity when I'm stuck at my desk and can't get my hands dirty.
> > > > >
> > > > > I'd thought about using three globs of silicone. but this thing weighs a lot and I was thinking it might be enough to squish it down to the nuthins'. I've got some sheets of gasket rubber that I could probably stack a couple dots up at each point and call it a win. I like the hockey puck idea, but I don't want my plate raised higher than the edge of the rectangular angle-iron box around the perimeter. I'd also thought about using heavy adjustable furniture feet like Keith had suggested.
> > > > >
> > > > > My plan was to build a basic rectangular support out of angle iron, then drop a couple cross braces across it at the right place on the x-axis (like the slats on an old bed frame), then put the support points on them. I'm also going to fabricate a plywood box for a cover, with a felt lining inside. I've got a very bad habit of cluttering up my work areas, so I refuse to set this plate up until it's built. A friend (actually his wife) succinctly calls it the 'the Horizontal Surfaces Rule' - (paraphrasing) All horizontal surfaces are required to be covered with something. Although I live by it also, I find it amusing she has assigned this behavior a name.
> > > > >
> > > > > Jim
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > -----Original Message-----
> > > > > From: Nelson Collar
> > > > > Sent: Aug 23, 2011 9:41 PM
> > > > > To: gingery_machines@yahoogroups.com
> > > > > Subject: Re: [gingery_machines] Surface plate support
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Jim
> > > > >
> > > > > I myself go with the angle iron. As far as the three point, why not just put a nice bead of
> > > > >
> > > > > silicone alowing to dry then set your stone on it and see how level it is? If it is good lift the
> > > > >
> > > > > stone out and put another bead of silicone and set the stone on it soft, when dry it will give
> > > > >
> > > > > support all around and have a softer than steel. Wood is for furniture and raw wood will take
> > > > >
> > > > > on moisture and dry out, causing expansion and contraction. "B" grade is nothing to snub
> > > > >
> > > > > your nose at for it is better than most have and the tolerance of +/- is closer than we need
> > > > >
> > > > > in the home shop. Unless you are picky!
> > > > >
> > > > > Just an idea
> > > > >
> > > > > Nelson Collar
> > > > >
> > > > >
> > > > > --- On Mon, 8/22/11, kabowers@ wrote:
> > > > >
> > > > > From: kabowers@
> > > > > Subject: Re: [gingery_machines] Surface plate support
> > > > > To: gingery_machines@yahoogroups.com
> > > > > Date: Monday, August 22, 2011, 12:55 PM
> > > > >
> > > > >
> > > > >
> > > > > On Sun, 21 Aug 2011 22:50:16 -0400 (GMT-04:00), you wrote:
> > > > >
> > > > > >
> > > > > >I've had a B-grade surface plate from Enco for quite some time and am interested in setting it up on a stand. The plate is 18x24x3, 0-ledge. I've got some heavy 2" angle with which I can fabricate a sturdy stand. Here and there I've read a surface plate should be supported at three points (called Airy points). Normally, I would have just supported the plate around its perimeter out of ignorance. The commercially-available stands I've seen on the web for this-sized plate appear to be supported by intermediate cross-members, but they don't look like they're providing 3-point support.
> > > > > >
> > > > > >I guess I have two questions here. What have those of you with these surface plates done to support yours? And am I being overly-anal about this or is improperly supporting it going to significantly effect the flatness of the plate within the tolerances I'm going to care (this is, after all, a cheap B-grade surface plate)?
> > > > > >
> > > > > >Jim Ash
> > > > > >
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