Big Red’s garage - New fab table.

Oregonredford · Jun 9, 2019

Well I am finally building a full size fab table for my garage. It’s just under 48x96. I had a local shop with a fiber laser cut the 3/8” thick top for me. A572-50 plate with 5/8” diameter holes on a pattern I designed. I’ve designed some tab and slot brackets to hold it to the frame.
More to come.
I will post pictures as I put it together. My design should stay pretty flat. (Within about 5 to 8 thou.

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f150skidoo · Jun 9, 2019

Interested to see how you are going to put this together. I'm a little skeptical on that table to be able to hold that tight of a tolerance with being only 3/8" plate.

LXCam · Jun 9, 2019

Ya had me at 5-8 thou

.

So that made me look BR and here was the down and dirty from one source.

TOLERANCES
Tolerance Over Specified Thickness, For Widths Given, in Inches

Thickness Thru 47" 48 to 59" 60 to 71" 72 to 83" 84 to 95" 96 to 107"
3/8 to under 5/8 0.03 0.03 0.03 0.03 0.03

Sorry, the format wouldn't stay.

However, holding 30 thou is still damn cool :beer:

Source: https://www.speedymetals.com/information/Material61.html

Oregonredford · Jun 9, 2019

LXCam said:
Ya had me at 5-8 thou .

So that made me look BR and here was the down and dirty from one source.

TOLERANCES
Tolerance Over Specified Thickness, For Widths Given, in Inches

Thickness Thru 47" 48 to 59"60 to 71"72 to 83"84 to 95"96 to 107"
3/8 to under 5/80.03 0.03 0.03 0.03 0.03

Sorry, the format wouldn't stay.

However, holding 30 thou is still damn cool

Source: https://www.speedymetals.com/information/Material61.html

That .03 tolerance is the Mill spec for thickness not flatness.
I built a few tables for shops with a .01 flatness tolerance

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LXCam · Jun 9, 2019

Oregonredford said:
That .03 tolerance is the Mill spec for thickness not flatness.
I built a few tables for shops with a .01 flatness tolerance

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Ya copy that, but that also goes hand in hand. BTW, I'm not doubting your skills, I'm just super interested in seeing what ya do holding that tolerance with something that's not in tolerance to begin with. :beer:

Oregonredford · Jun 10, 2019

LXCam said:
Ya copy that, but that also goes hand in hand. BTW, I'm not doubting your skills, I'm just super interested in seeing what ya do holding that tolerance with something that's not in tolerance to begin with.

I’ve been in the industry a long time. The thickness and flatness don’t go hand in hand.
Thickness is measured within 2” of a master plate at the mill. A master plate can have a mild crown in it. The sub plates you get out of a master plate can come from anywhere in the master. The sub plates and the master plate can also be a uniform thickness. Just because the mill spec say you can have a tolerance
of +.024 to -.006 doesn’t mean you will see a .030 difference in one place on a plate vs another. A single plate is actually only allowed about .006 to .010 variant within that plate.
An example of a typical master plate is 8 to 10’ wide and 20 to 40’ long.
Or it could be coil stock depending on the thickness. Typically 3/8” thick is out of a master plate.
Flatness is measure with a CMM and can be clamped to a flat surface like a granite slab. An option to check flatness at the edges is to use a tapered feeler gauge under the edge to see how much deflection you have at any given place around the material. If you have a cmm your granite slab is the datum representing a true 0. Then you measure the plate with the machine and take an average reading less the material thickness and you can get your flatness.

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Robert Haas · Jun 10, 2019

Oregonredford said:
I’ve been in the industry a long time. The thickness and flatness don’t go hand in hand.
Thickness is measured within 2” of a master plate at the mill. A master plate can have a mild crown in it. The sub plates you get out of a master plate can come from anywhere in the master. The sub plates and the master plate can also be a uniform thickness. Just because the mill spec say you can have a tolerance
of +.024 to -.006 doesn’t mean you will see a .030 difference in one place on a plate vs another. A single plate is actually only allowed about .006 to .010 variant within that plate.
An example of a typical master plate is 8 to 10’ wide and 20 to 40’ long.
Or it could be coil stock depending on the thickness. Typically 3/8” thick is out of a master plate.
Flatness is measure with a CMM and can be clamped to a flat surface like a granite slab. An option to check flatness at the edges is to use a tapered feeler gauge under the edge to see how much deflection you have at any given place around the material. If you have a cmm your granite slab is the datum representing a true 0. Then you measure the plate with the machine and take an average reading less the material thickness and you can get your flatness.

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That is a lot of typing to try and not sound like you made a mistake when you claimed you were controlling tolerances to 5 to 8 thou.

Math is tricky, but the difference between those digits on the right side of the decimal point matter :spit:

Robert Haas · Jun 10, 2019

FYI 3/8" steel plate looks pretty darn flat till you actually put a instrument on one and take a few "shots"

If you have ever been to the steel yard and watched them haul a 4 x 8 plate around on their fork lifts and watch how much they let that steel bow and warp as it is transported from its "none flat" storage rack to it's delivery vehicle you will come to realize that piece of stock is about as flat as the street in front of your house.

Oregonredford · Jun 10, 2019

Robert Haas said:
FYI 3/8" steel plate looks pretty darn flat till you actually put a instrument on one and take a few "shots"

If you have ever been to the steel yard and watched them haul a 4 x 8 plate around on their fork lifts and watch how much they let that steel bow and warp as it is transported from its "none flat" storage rack to it's delivery vehicle you will come to realize that piece of stock is about as flat as the street in front of your house.

I’ve seen bad. This plate is pretty clean and really quite flat.
We will see how it all turns out when complete. I’m confident in my ability

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The Tool Tyrant · Jun 10, 2019

Even if your plate was Blanchard ground (which it's not) it still has to sit on a frame, which again would HAVE to be with-in the same specs, as a 3/8" plate is not thick enough to span inconsistencies in the sub-frame. Then again, the sub-frame would require adjustable feet to correct any 'twist' that could be caused by inconsistent concrete. I won't even get into 'thermal dynamics'.

My certified granite table is 6" thick for a reason...other than curtailing theft. :shocking:

Robert Haas · Jun 10, 2019

A fab table within a half a tenth is considered dream like in my shop.

Robert Haas · Jun 10, 2019

Here is a "medium size" fab table that is Blanchard ground to .025" sitting on a 24" thick concrete slap.

I toured Boeing's large assembly facility back in the 80's. they have a 35'x150' inspection fixture. It has internal refrigeration as well as the slap it sits on to control thermal variation. the fixture has to be adjusted annually to retain its certification. Things are placed on it and allowed to "normalize" for up to 72 hours before measurements are performed. To this very day it is one of the most amazing man made devices I have ever seen.

Oregonredford · Jun 10, 2019

Size does matter when you are looking at the tolerance.
My frame does have adjustable feet. The flex is always something to consider.
The frame will bed fit and welded on a granite slap at the big shop I run.
I’ve also been designing and building machining fixtures for a number of years holding +\- .0005 for machining titanium aircraft parts. All in temp controlled environment and everything is ground.
This table will be a task to hit .015 but we will see. My original thought of 5 to 8 may be a dream [emoji51]

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bdbecker · Jun 10, 2019

Trying not to be distracted by the flatness statement... I think that top is a going to be pretty sweet!

Allowing myself to be distracted by the flatness statement.... When you say you are going to achieve 0.005"-0.008" of flatness, is that across the entire surface of the table?

Oregonredford · Jun 10, 2019

bdbecker said:
Trying not to be distracted by the flatness statement... I think that top is a going to be pretty sweet!

Allowing myself to be distracted by the flatness statement.... When you say you are going to achieve 0.005"-0.008" of flatness, is that across the entire surface of the table?

Originally yes. I think .015 is attainable.
Once it’s all fabricated I will have the one surface ground. I’ve got a few favors owed to me.

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bdbecker · Jun 10, 2019

Gotcha... I didn't know you were going to have the surface ground - that'll definitely help quite a bit.

NORTON'S SHOP · Jun 11, 2019

Oregonredford said:
Originally yes. I think .015 is attainable.
Once it’s all fabricated I will have the one surface ground. I’ve got a few favors owed to me.

In every reply you state an additional "and then I." You're starting with a 3/8" plate and then will have it surface ground? You may end up with a 1/4"+/- plate when finished.

I wish you all the luck in the world. I've been in the Tool & Die industry since I graduated from high school almost 40 years ago. Seems like a lot of blowing smoke. Hope in the end you achieve what you're looking for.

Jcrapola · Jun 27, 2019

I been a toolmaker awhile myself, and one thing I am sure of. There is always someone or other telling you it can’t be done. I have seen some pretty amazing things get built by talented people. Spending a few minutes on this forum is always humbling.

I throw no rocks, and get annoyed at the folks with nothing better to do than tell you they know better. I wish I hand the space for a table that size myself! Good luck brother!

bullnerd · Jun 27, 2019

LOL! Im with ya Crapola!

I'm happy to be in a place where we can show each other the junk we build in our shops.

Guy hasn't been on since the 16th, probably tired of all the belly aching.

Oregonredford · Jul 16, 2019

Thought I’d update this thread. After successfully assembling my table I have one corner that has a little warp in the plate. Other than this corner (about 3” from an edge) I have an average profile over the top of .007 which is close enough without any grinding or other Bs.
It’s all about the frame prep in my mine.

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Oregonredford · Jul 16, 2019

With exception to the one corner I feel like the fab of this table is a complete success. Having kept the welding of the top to the frame at an absolute minim via tab and slot connection plates it was fairly easy.
I used 1-5 acme rod leveling feet with 10” of throw for work height adjustability.

The one corner is about .027” out but neither a .008 feeler gauge or a tapered feeler gauge will fit under a 48” straight edge.
I’ve got a friend coming in a few weeks with his Romer arm even though this isn’t the best tool for the job it will show us even more so where the corner issue starts.
It turned out so well I’ve got two shops asking for tables in my area.
This was all built for less than $1500

Success

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Oregonredford · Jul 16, 2019

Jcrapola said:
I been a toolmaker awhile myself, and one thing I am sure of. There is always someone or other telling you it can’t be done. I have seen some pretty amazing things get built by talented people. Spending a few minutes on this forum is always humbling.

I throw no rocks, and get annoyed at the folks with nothing better to do than tell you they know better. I wish I hand the space for a table that size myself! Good luck brother!

Thanks for the confidence. I let things settle. Sometimes people who whine a lot are blowing their own smoke because they haven’t figured out something can be done.
It’s all good. I’m quite please with my creation.
Have a great day

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rattle_snake · Jul 16, 2019

Only issue I have is that you built your table after I made mine, and I would have stolen the slot/tab attachment scheme.

Nice work.

Natemade · Jul 16, 2019

What method did you use to adjust the table top flat before welding it to the frame? It looks like its just sitting flat on your frame? Did you machine the top sides of the tube, or shim it as you worked down the table?

Oregonredford · Jul 16, 2019

Natemade said:
What method did you use to adjust the table top flat before welding it to the frame? It looks like its just sitting flat on your frame? Did you machine the top sides of the tube, or shim it as you worked down the table?

I built the frame on a machined table from work.
I brought the frame home and leveled it out with a laser. Then I set the top on the frame and used the holes in the top to clamp the top to the frame. I checked the top at that time for flatness and it was really good.
The way the tab and slots work it keeps the heat from warping the top. So I welded the tabs to the top only in the slots and then welded the tabs to the frame on the Verticals only.
I have a 3D model and drawings.

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