Flattening my CNC's table top (finally!)

Jason Beam

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1,364
Location
Sacramento, CA
Well after futzing around with my dust shoe and a few other distractions, I finally got around to flattening my top... Here's a video I shot of the dry run and the first pass ...


I built the router mount with some intentional play for this very thing. I knew it'd have to be done and was prepared. I'm kinda surprised it was as close as it was, actually. The mount has slightly oversized holes which allow me to wiggle it around a bit. I still need to play a little bit with the same adjustment in the X plane but I don't think it's too bad as I ran a couple cross passes earlier that didn't seem to have any trouble at all.

Anywho - after a .005" second pass, all the pencil marks were gone which was nice - i figure i was out only .010" total across the entire surface. Not bad for an MDF torsion box without actually TRYING to get it very flat!

With it now flat, I've begun the fun task of coating it with poly. My reasoning is that MDF is not uniform in density - the top surface is much denser than the inner stuff and machining off that top "skin" has exposed a much less durable surface. By thinning down poly and flooding it on till it quits soaking in, my hope is that this surface will be very durable and should accept double stick tape really well.

I first put a 15-20% mixture of poly on, it soaked WAY in - used a whole pint jar on the first pass. The 2nd coat was a bit thicker, about 30% and soaked in another pint jar's worth. The 3rd pass today was about 50% and I had to work to get it to soak in all of that pint jar. I'll let this dry a couple days then lay down a full thickness coat and probably run a very light skimming cut to knock down any swelling - probably another couple coats of poly after that and it should be a finished surface that I can use for years. :D

Thanks for lookin!
 
Dave, you should put a long string with a rubber band on it to attach to the middle of your vacuum hose, keep it off the table and out of the way, but have lots of play in it too!
Great job!
 
Stu - yeah i'm working on that very thing ... i was pleased with how well it behaved for the most part except for the dragging ... I'll be working out something for that - I was considering something like a curtain rod with a few sliding clips that would carry the weight but allow it to move fore and aft yet ...

Still doing some headscratchin' on that one :D
 
Looks great, Jason. Are you planning on using it enough to warrant the space dedication, or just to see if you could? While I would love to have something like that, I don't think I'd do enough with it to justify the space required. But wew all do different things and I can't wait to see what you do with it!
 
Looks great, Jason. Are you planning on using it enough to warrant the space dedication, or just to see if you could? While I would love to have something like that, I don't think I'd do enough with it to justify the space required. But wew all do different things and I can't wait to see what you do with it!

That's exactly what my secret decoder ring said when I ran my wife's questions through it!

I do plan, eventually, to use it for hire to some extent. My near term plans are to play and learn as much of it as I can and probably won't try selling anything for the first year or so. I figure it'd be unfair to charge anyone right now as I'm not sure what realistic costs are yet. Once I have a few of my own projects under my belt, I'll have a better sense of that and can start doing some business with it.

And for my shop, this really wasn't an additional use of space. It sits where I used to have a cabinet for outfeed support. In that cabinet was a lot of air because I never got around to organizing it. There's actually a good deal of space on the shelf below and I'll likely put together some boxes or drawers for down there. In the end, I look at it more of a refinement of previously used space. That cabinet was really more about outfeed support and the CNC table is perfectly level with the TS so it's now outfeed support. By sending the gantry all the way to the side, I can still rip ply just as before.

But I think this is the last "air" I'll be able to refine in this space - it's getting tight these days. If my brain latches on to some other obsession, I'm gonna have to add onto the building! :p
 
That's a great idea of using the table for outfeed.

There are dozens of things that you can do with it, just need to decide if you've got time to do manufacturing or just want to have it for your own use. I had started to do zero clearance plates with mine just before I sold the last house. Found I could make them repeatedly without standing around and watching the machine. I was listing them on ebay and making a little money to pay for barley pop. However, as you said, you need to determine your cost for running the machine + wear/tear; then decide what your bottom line is for doing projects to make it worth the effort.
 
Oh ZCIs are a great idea. I like that!

I was also casually considering the idea of designing a smaller benchtop CNC machine that I could cut parts out on for and let the buyer assemble. Like a little 18x18 or something ... or 18x24. I have a good source for aluminum and thought that might be a fun project.

Then again - repetition doesn't sound much fun - once I've figured something out, i make one or two and then move on to the next challenge. Maybe custom signs are a better fit for my brain.
 
I hope you're planning on a masonite/hardboard cover for the CNC table for its second job as an outfeed table. It'd be a shame to do all that flattening work then damage it.... in machine shops, guys get FIRED for using surface plates for anything but measurement related work.
 
I hope you're planning on a masonite/hardboard cover for the CNC table for its second job as an outfeed table. It'd be a shame to do all that flattening work then damage it.... in machine shops, guys get FIRED for using surface plates for anything but measurement related work.

I'm not - i don't have the clearance, actually - maybe a formica scrap would fit - but honestly, I'm not too worried about damage from outfeed. My previous cabinet's outfeed was never damaged so i'm not terribly concerned that anything i feed through the saw would hurt the CNC. Maybe I'm having a failure of imagination here... but it doesn't seem that high a risk to me?
 
.......But I think this is the last "air" I'll be able to refine in this space - it's getting tight these days. If my brain latches on to some other obsession, I'm gonna have to add onto the building! :p

Come on Jason, be real here, you have a TON of unused space in your workshop, from what I've seen on your videos, TRUST ME, on this one, LOTS of under utilized space, heck, I can see bare wall all over the place :D
 
I'm not - i don't have the clearance, actually - maybe a formica scrap would fit - but honestly, I'm not too worried about damage from outfeed. My previous cabinet's outfeed was never damaged so i'm not terribly concerned that anything i feed through the saw would hurt the CNC. Maybe I'm having a failure of imagination here... but it doesn't seem that high a risk to me?

1/4" hardboard would do the trick. Dunno what you've actually made it from, but it looks like MDF which is pretty soft. It's your table, but if it were mine, I'd cover it when not in use.
 
Come on Jason, be real here, you have a TON of unused space in your workshop, from what I've seen on your videos, TRUST ME, on this one, LOTS of under utilized space, heck, I can see bare wall all over the place :D

LOL!

Ok i can't really compete with you, Stu! I did have an 8x24 shop when i started and I crammed almost all of what i have (smaller TS and only one BS, no metal working tools) into it and got some good productivity out of it. When I moved to this one, I wanted to be sure I didn't have to struggle too hard to work anymore. I've gone to great lengths to only have to move out the occasional tools now - router table, table saw, workbench, drill press and miter saw are all readly available unless I've got crap lying on it. Everything else typically gets pulled out when needed.
 
1/4" hardboard would do the trick. Dunno what you've actually made it from, but it looks like MDF which is pretty soft. It's your table, but if it were mine, I'd cover it when not in use.

It is MDF, good catch. If I have the clearance, I'll give it a shot - the TS might only be about 1/8" above the table - I might have some scrap formica laying around that I could use. I do appreciate you pointing out the concern - for sure. :)

Being as the top is just MDF, I guess it wouldn't be the end of the world if it got dinged up from time to time. the machine can always re-flatten itself as needed, too.

Maybe I just need to learn the hard way - I'm coating it pretty heavy with poly so it *should* be reasonably durable - i'm hoping. Time will tell, eh? :)
 
It is MDF, good catch. If I have the clearance, I'll give it a shot - the TS might only be about 1/8" above the table - I might have some scrap formica laying around that I could use. I do appreciate you pointing out the concern - for sure. :)

Being as the top is just MDF, I guess it wouldn't be the end of the world if it got dinged up from time to time. the machine can always re-flatten itself as needed, too.

Maybe I just need to learn the hard way - I'm coating it pretty heavy with poly so it *should* be reasonably durable - i'm hoping. Time will tell, eh? :)

Oh, NOW you tell me. :D Poly would go a looooooong way towards protecting it. Applying it should be interesting, though. How are you going to keep it off the t-track? Of course, if you're flattening to a thou, you'll have to reflatten the poly... :eek:
 
Oh, NOW you tell me. :D Poly would go a looooooong way towards protecting it. Applying it should be interesting, though. How are you going to keep it off the t-track? Of course, if you're flattening to a thou, you'll have to reflatten the poly... :eek:

Doh - I shoulda said that from the start - sorry bout that!:whistling:

Well I masked the track a fair bit but I'm still sloppy - shoulda covered the whole thing. I've taken to just wiping it with a rag dampened with mineral spirits - hopefully it won't have an adverse effect.

I hear ya on having to flatten the poly. I laid down a super thin coat (about 15% poly) and it soaked up a pint jar of it and woulda taken more, for sure. The 2nd coat was thicker at about 30% and a third coat at 50%. That last coat took all of a pint but I felt like I had to work at it that time. It's had a couple days to harden now and I'll run a skim cut to see if it swelled any. It may take a few runs at it but eventually I'm hoping the poly will firm up that squishy MDF left behind after removing it's outer skin.
 
Ya know, Jason.... I just went through and read all the words you typed with your video in the original post. Family Woodworking needs a facepalm icon. :bang:

I look forward to seeing the great things you produce with your new toy. :headbang:
 
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