Need to flatten 5/8" thick aluminum plate

Hi Folks,

I screwed up and went cheap with the purchase of aluminum for the table of my router. I purchased 5/8" mill finish 6061 aluminum plate that is 27" x 48". I rolled the dice in hopes it would be somewhat flat, it isn't. It is curled .090" at the center. I know, I should have purchased MIC 6 but like I said, I went cheap and now I have to pay the price.

Any suggestions on how to flatten this thing? I am in the Chicago area, does anyone know of a company that has the equipment to flatten it?

I am open to ideas, and hopefully this is a lesson to others, don't be cheap because you have to pay the price no matter what.

Thanks in advance!

Chris D

Mount it on the table, high side up and surface it on the machine a little bit at a time?

unfortunately that won't work, the table is larger than the travels of the machine.

Thanks though.

Chris

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Originally Posted by Chris D

Hi Folks,

I screwed up and went cheap with the purchase of aluminum for the table of my router. I purchased 5/8" mill finish 6061 aluminum plate that is 27" x 48". I rolled the dice in hopes it would be somewhat flat, it isn't. It is curled .090" at the center. I know, I should have purchased MIC 6 but like I said, I went cheap and now I have to pay the price.

Any suggestions on how to flatten this thing? I am in the Chicago area, does anyone know of a company that has the equipment to flatten it?

I am open to ideas, and hopefully this is a lesson to others, don't be cheap because you have to pay the price no matter what.

Thanks in advance!

Chris D

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Find a company that has a Blanchard Grinder in your area, it is a little on the thin side at 5/8 thick they can Grind it, 6061 will be better then MIC6, MIC6 is good but is a little softer than your 6061 even Ground MIC6 a piece that size could easily be .012" or more over 48" The accuracy of Ground MIC6 is normally .005" per foot

I'm not quite sure why the suggestion made by he1957 won't suffice if it's only the center that is high and not a significant amount at that. Additionally you aren't going to be cutting larger than the travel of your machine anyway so the surface would be flat within your cutting area. If you really needed to secure material larger than your cutting area simple shimming should suffice. This is a router right? Not a mill so extreme precision for machining metal isn't really a factor either?
How is the table top to be mounted? If the surface it's mounted to is flat (or even it's it's not) and you are using recessed screws/bolts in the top or have threaded holes in the plate to attach from underneath, it may flatten enough when secured. Using shims when mounting and securing may also be an option to pull it flat. I would think the cost of having it ground at a shop would be excessive in comparison.

Similar to @coherents suggestions. The reason for high-side up in my original comment. That leaves the lowest points around the edges but outside the cutting area. Essentially the whole top surface should then be quite flat. Unless you also screw down the middle of the plate there might be a hollowish lack of contact with the table and frame but you could use some high compression rubber padding strips between the table bottom and the frame top to allow for this and to help with vibration dampening.

Hi guys,

To clarify my point.

The plate is 27" x 48", the travels of the machine are 19.4" x 39.5"

The plate is shaped like a flat "U". I could mount it as a "U" or I could mount it as an upside down "U". It will mount to 6 rails of 1" x 3" 8020 extrusion which is on edge.

Regardless of which way I mount it, if I mill this on this machine, I will end up with what will look like a groove down the center along X axis that is .090" deep in the middle or at the ends. That groove will stop short of the ends by about 4.2" making it look like a pocket.

Bolting the 5/8" thick aluminum to the 8020 frame will most probably distort the frame, even if using shims.

No matter how I do it, it isn't the right way and it will look like a hack job.

If I have to spend $200 to get it straightened it is worth it to not have something that looks like a hack job.

With that said, I really do appreciate the suggestions, that is what makes this forum so good!

Chris D

Without flattening out the plate before machining on it, you will wind up with a plate that is about 1/2 inch thick.

You are going to have to heat and press flat before machining to true flat. If you don't heat to ''relax'' it, it will turn into a pretzel when you machine on it. You need to find someone with an annealing oven large enough for the piece, and also has a large platen press that will take the piece, or at a minimum a large H-frame press that the piece will fit in.

Hi Jim and Chris - If you anneal the plate it will be too soft to use as a machine base. It's a 2mm bow which is way out of the supply spec. If it's not too late read the supply spec and if the plate is out send it back. Straightening a plate like that is hard. If you put it in a press and push it it will probably end up with a double kink. I'd use it for some other job or machine parts and buy a new flat piece. Cheers Peter

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Originally Posted by coherent

I'm not quite sure why the suggestion made by he1957 won't suffice if it's only the center that is high and not a significant amount at that. Additionally you aren't going to be cutting larger than the travel of your machine anyway so the surface would be flat within your cutting area. If you really needed to secure material larger than your cutting area simple shimming should suffice. This is a router right? Not a mill so extreme precision for machining metal isn't really a factor either?
How is the table top to be mounted? If the surface it's mounted to is flat (or even it's it's not) and you are using recessed screws/bolts in the top or have threaded holes in the plate to attach from underneath, it may flatten enough when secured. Using shims when mounting and securing may also be an option to pull it flat. I would think the cost of having it ground at a shop would be excessive in comparison.

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You can not machine a Router table in place and expect it to be flat the one main problem is you have no reference to Traming the spindle, so you need a surface that is already flat with the table and then you can tram the spindle once the spindle it tramed then you can cut the table if you need to

Without the spindle being Tramed the table will never be flat

27" x 48", 090" > 70 x 125, curved2.3 pfff :)

with a bit of luck, you may accentuate the curvature each time you cut it, because there is remanent tension inside the plate; you have to 'calm' it down

i believe you won't send it back, and you wish to keep it : tie it with a rope, and hang it on a wall, just like a painting :) play tennis for a while ( try fast aces ) ... you could warm it a bit before, or just leave it in the sun ... from time to time, jump on it

when it reaches a curvature < 0.5 mm, try to machine it / kindly :)

ps : about tennis : it was used to de-stress chasis, by shooting balls at it, and using a torsion machine

It does not Need to be Level milling machine tables onboard a Navy machine shop are never level. :wave: So tram your router Z to be true with your cross bars (the ones that would hold the spoil board) on the machine use a sheet of plate glass or what to be the router spindle trammed true . Use a saw or what suits to cut the plate to fit your router table. Put in a milling cutter suited to the metal your truing and mill it flat taking light cuts. It will be true or the exact same distance from the gantry and that all you need.

I contacted the vendor and was informed that Alcoa's standard is .1" longitudinal and .125" transverse and they will not replace it.

Oddly, other vendors specs are below .032" for this size plate.

So far, I have sent out about 5 RFQs in the Chicago area for: grinding, straightening, or plane milling, none have responded thus far. Very interesting there has been no response, makes me think the shops are so busy they don't need the work, or, they are not business savvy and are losing business because they don't check their own electronic forms that are used for RFQs.

Still pondering all options.

I have a brand spanking new VMC just outside of my office that is plenty large enough to machine this plate. Unfortunately, the company doesn't want to "dirty it up" because the machine is for sale (we are an importer). Too bad there isn't a customer requesting a test cut on it, that would open the door for me to use it for this purpose!

Oh well, that's what I get for being cheap!

Chris D.

Chris its not a big job so nobody is interested. One user suggested grinding, I have not seen a wheel able to grind aluminum, The way I look at it, you can try to sell on maybe Craigslist locally or try one of the fixes I and a couple of others suggested. You have nothing to lose except your time
A wood working shop may have a drum sander that wide, 30 inches, you will need to buy them a new sanding drum, or someone in your area might have a CNC router table that can do light aluminum. Heck I can do 48 x 27 I think you said. .

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Originally Posted by wmgeorge

Chris its not a big job so nobody is interested. One user suggested grinding, I have not seen a wheel able to grind aluminum, The way I look at it, you can try to sell on maybe Craigslist locally or try one of the fixes I and a couple of others suggested. You have nothing to lose except your time
A wood working shop may have a drum sander that wide, 30 inches, you will need to buy them a new sanding drum, or someone in your area might have a CNC router table that can do light aluminum. Heck I can do 48 x 27 I think you said. .

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How do you think they Grind Aluminum Tooling Plate you can Grind any type of material you want to put on a Grinder if you know what you are doing, most all companies that have Blanchard Grinders will do Aluminum

Your Router or even a big Mill would not machine this piece of Aluminum Plate flat enough for a Machine Table, Grinding is the only way to do it, some planer Mills could do it but would not be as good a surface finish or as accurate

Some of these company's have in stock Ground 6061 stock sizes or custom, snip of a 12" X 12" piece

Ground Brass and Part of a Aluminum Injection Mold Aluminum that I did on my Grinder

Mic6 Plate comes in sizes up to 60.5" x 144.5" Ground finish

Quote:

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Originally Posted by Chris D

I contacted the vendor and was informed that Alcoa's standard is .1" longitudinal and .125" transverse and they will not replace it.

Oddly, other vendors specs are below .032" for this size plate.

So far, I have sent out about 5 RFQs in the Chicago area for: grinding, straightening, or plane milling, none have responded thus far. Very interesting there has been no response, makes me think the shops are so busy they don't need the work, or, they are not business savvy and are losing business because they don't check their own electronic forms that are used for RFQs.

Still pondering all options.

I have a brand spanking new VMC just outside of my office that is plenty large enough to machine this plate. Unfortunately, the company doesn't want to "dirty it up" because the machine is for sale (we are an importer). Too bad there isn't a customer requesting a test cut on it, that would open the door for me to use it for this purpose!

Oh well, that's what I get for being cheap!

Chris D.

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Even with that Big Mill you would have a job to keep it flat while milling it would move all over the place, Blanchard is really the most accurate way to machine your plate or double disc Grinder that will do both sides at the same time

It would certainly be a challenge to mill it flat with that much bow. It would require a lot of flips and special clamping to get it from the sides and no top clamping.

I am currently pricing out some MIC 6 that is ground to within +- .005 which I am ok with. I may end up cutting this bowed piece into smaller pieces as I need them. Can never have too much raw material!

Interesting range on the prices so far - ranges from $220.00, $380.00, and the highest is at $550.00, none include delivery.

Chris D