# Magnetizing the Downdraft Table (part 1)



## MtnBiker (Mar 5, 2022)

We want to make metal finishing easier without having to buy one of those giant conveyor belt style sanders - the ones that cost a mint and eat up all the space in a garage shop.




Something like this Time Saver above - not gonna happen. And a precision surface grinder is not a good way to make the kind of brushed surface finish we're looking for (and way too small for anything close to reasonable money).




First step is to adapt our downdraft table for a smaller, hand-held metal finishing tool like this Walter. The idea is to replace the stainless steel top on the downdraft with something custom made that will allow us mount electro-magnets flush with the work surface. We don't want to chase the workpiece around the table or ruin the finish. We'll design the new top in F360 and then fabricate on the CNC plasma. 





We're trying out magnets used for security doors (when they buzz you in). Open to ideas though. Cheap and don't take much power - but the fit does need to be flush. We wired a power supply into the main power switch on the table. Will put another witch on the circuit when we don't need magnetizationing.

Needed a box for the power supply - pretty harsh environment for electronics inside that table. Gave us a chance to try out the new pan brake (Grizzly G0542). Bending is important in metal fabrication and we just don't have the space for a proper commercial press brake. Pretty happy with this Grizzly (obviously Chinesium but not horrible). Will bend up to 12 gauge and 20 gauge is laughably easy. Fit and finish is pretty good on the parts that matter and typical on the parts that don't. Best of all, very quick and efficient for one-off work which is closer to what we do.









Technically not capable of reverse bends on two axes but we forced the issue a bit. Not terrible for our first go on sheet metal bending I think.

More to come as we run our little science experiment.


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## brino (Mar 6, 2022)

MtnBiker said:


> We're trying out magnets used for security doors (when they buzz you in). Open to ideas though. Cheap and don't take much power - but the fit does need to be flush.



I have seen people convert old microwave oven transformers into magnetic vises.

I personally have used one to demonstrate electromagnetics to kids. 
Using only two AA-cells no could pull it off a 1/4" steel plate.

Stay tuned, I will post back with some links.......

Brian


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## brino (Mar 6, 2022)

Here's the thread with a video:
https://www.hobby-machinist.com/thr...rom-the-guts-of-a-microwave.85743/post-763641
.....and my contribution to it:
https://www.hobby-machinist.com/thr...rom-the-guts-of-a-microwave.85743/post-763862

Brian


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## Cadillac (Mar 6, 2022)

I have a friend that has a good side business with his plasma cutting table. He cuts signs from 20g to 14g all the time. Biggest part of jobs is deburring slag. 
 I e been on him to get a drum sander Self feeding as you pictured. I see them all the time at auctions and for what they do I think thats the ticket. They are actually easy to build Acquiring the parts is the harder part. 
  What I ended up doing for him was at one of the auctions I attended they had a large electro mag for a large surface grinder. 12x24 electro mag with the controller for opening bid of 100 bucks. 
  So we recessed the mag chuck in his grinding table so it’s flush with the surface. Then he throws a thick plastic welding screen material over the table. He has the same handheld drum sander you also pictured from Eastwood company. Flip the switch on the mag and it secures parts while he deburrs. When done he demags and removes the plastic. Which keeps all the grinding dust from sticking to the mag. Idea works really good if you can get a large mag chuck. Doesn’t have to be electric either. I have a manual one I use for holding parts for finishing


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## MtnBiker (Mar 8, 2022)

MtnBiker said:


> We want to make metal finishing easier without having to buy one of those giant conveyor belt style sanders - the ones that cost a mint and eat up all the space in a garage shop.
> 
> View attachment 399185
> 
> ...


We had an oversized 4x10 sheet of 1/8" laying around (literally laying on the floor cuz where else you gonna keep it in a garage shop). Great opportunity to play with work envelope on the 4x8 CNC plasma table.




No problem with the oversize - the XR can handle about 52" wide and about 100" long...or in this case about 2' of overhang.




Design was pretty smooth. We added up the area of the new holes vs the old holes and it was about the same. No issues on the cut even with holds-o-plenty. Fairly complex...needed pretty good precision.




Testing fit post cut for this 19" x 59" table top. Perfect. No runs, no drips, no errors. A little cleanup and this will look good. Holes came out great. We'll machine some custom brackets that will let us fine tune the height of the magnets. Fun little project.


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