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-   -   Certi-flat table tops (https://www.shopfloortalk.com/forums/showthread.php?t=53837)

Oscar 06-12-2022 02:33 PM

Certi-flat table tops
 
1 Attachment(s)
I ordered two 3x4 Pro Top kits that need to be assembled. Two because I can make a single 4 x 6 ft table together, or separate them if I don't need that much area.


Proper clamping and quadruple checking ! I already had to grind out the tacks on the underside of the 1st table since I wasn't happy with how flat it ended up. Granted I won't be doing ultra-precision work, it would be nice to get in the ball-park of the manufacturer spec of ± 0.015" (not sure over what span, I need to ask).

greywynd 06-12-2022 03:22 PM

.015” over that size with a weldment? Best of luck.


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Oscar 06-12-2022 03:39 PM

Perhaps you are making an assumption as to just how much weld is to be used. IF you over-estimate that, then I can see why you would say that 0.015" over that size is out of reach. And besides, it's ± 0.015", not absolute. So there could be up to 0.030" absolute variation, which is fine for what I need it. Hint: It's not welded as much as you think. ;)

milomilo 06-12-2022 05:06 PM

Quote:

Originally Posted by Oscar (Post 784864)
Perhaps you are making an assumption as to just how much weld is to be used. IF you over-estimate that, then I can see why you would say that 0.015" over that size is out of reach. And besides, it's ± 0.015", not absolute. So there could be up to 0.030" absolute variation, which is fine for what I need it. Hint: It's not welded as much as you think. ;)

Did you check the flatness of the clamped up assembly before you tack welded?

greywynd 06-12-2022 08:00 PM

Quote:

Originally Posted by Oscar (Post 784864)
Perhaps you are making an assumption as to just how much weld is to be used. IF you over-estimate that, then I can see why you would say that 0.015" over that size is out of reach. And besides, it's ± 0.015", not absolute. So there could be up to 0.030" absolute variation, which is fine for what I need it. Hint: It's not welded as much as you think. ;)


Meh…it’s a welding table.

I’m a toolmaker by trade, I have a granite surface plate is I need absolute flat. Next is an aluminum reference/fixture plate, think of a cast iron surface plate, except in aluminum, about 30” x 54” long, and within likely +/- .003” or so over the entire surface.

Last is my 3’ x4’ welding table, 1/2” thick, maybe within 1/16-1/8”? Usually the aluminum plate is on it anyway so it gets used as a welding surface. [emoji4]


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digger doug 06-13-2022 07:03 AM

How can 3/16" hot rolled be expected to hold .015" ?
And for how long after you assemble it ?

JBFab 06-13-2022 08:55 AM

Quote:

Originally Posted by digger doug (Post 784875)
How can 3/16" hot rolled be expected to hold .015" ?
And for how long after you assemble it ?

By the way it's built. If you look at those tables there's only something like an 8" square that is unsupported. Reference surfaces are clamped tight to a laser cut edge. I agree .015" is a lofty goal, but I bet they get pretty close. They are really only tacked together (and only need to be) to help prevent warping.

midmosandblasting 06-13-2022 09:22 AM

Please let us know on completion what was attained .

Oscar 06-13-2022 09:48 AM

Quote:

Originally Posted by milomilo (Post 784865)
Did you check the flatness of the clamped up assembly before you tack welded?

yes, it's a work in progress. I actually ground out many tacks and had to re-do them to try to get it at as flat as I can.

Quote:

Originally Posted by digger doug (Post 784875)
How can 3/16" hot rolled be expected to hold .015" ?
And for how long after you assemble it ?

The slats on the bottom are laser-cut to ± 0.003", so when the top is clamped down to them, they help bring it down to their level. Obviously they will flex too, so that is where the judicious selection of clamping pressures comes into play as well.

Quote:

Originally Posted by midmosandblasting (Post 784877)
Please let us know on completion what was attained .

I will. Initial testing showed pretty close the mfg spec, but then again I was using a box level to check against for flatness, which likely isn't super duper straight on it's own. I ordered a machined straight edge (± 0.003") so I will do a little more testing and loosen up some tacks and re-do as needed.

digger doug 06-13-2022 10:36 AM

Quote:

Originally Posted by Oscar (Post 784878)

The slats on the bottom are laser-cut to ± 0.003", so when the top is clamped down to them, they help bring it down to their level. Obviously they will flex too, so that is where the judicious selection of clamping pressures comes into play as well.

The website made no distinction from the ribs to the "top" materials.

Hot rolled plate is not that accurate in thickness, so saying that the top will be held to the .003 tolerance of the laser cut notches is meaningless, unless you are using the underside.

Is your continued touting of these because you have a financial interest ?


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