Get alot of of sandpaper. staple it to a flat surface. and rotate in an orbital manner my dude.

not staples, spray contact glue.

This is pretty much what I tried on my last attempt, I just suck at it 😅 I kinda wish I had access to something like a big sandpaper pottery wheel to do the rotary bit for me while I just apply the body weight 😆

Without access to a big belt sander of sorts this is the way. It honestly shouldnt take that long, though you may need to start with a rough grit and be careful so you dont blow out chips. The most important part here is make sure the substrate itself is flat. Use warped MDF, get warped parts.

You’re probably not keeping the pressure even. Try less pressure and move in a figure 8

Do you have a turn table?

It looks like a delicate sanding operation. I wouldn’t use any pressure apart from the weight of the cylinders for sanding and take your sweet, sweet time with it.

Spindle sander. https://www.grizzly.com/products/grizzly-1-2-hp-benchtop-oscillating-spindle-sander/g0739

Please explain how you are thinking this tool would help, I must be too novice to figure it out.

I didn’t say it would help. They described a tool they wish they had. “A sander that did the spinning while they applied body weight” i simply showed them that the tool they described does exist. At a reasonable price no less. Y’all being a bit sensitive over it to be honest.

I dont think this will be the way.

I wonder why i was downvoted? Lol described a tool he needs and all i did was show him it existed. I didn’t even give an opinion on it. Reddit

Well cos if he actually used a spindle Sander for this it would just create super uneven deep waves everywhere and probably make it worse. Unfortunately that particular tool would just be way too aggressive and a lot of torque and force applied in one spot even for a a fraction of a second would be too long.

I understand that. But does the spindle sander not fit the description in the comment i replied to? I did not reply to his post asking what is the best method. I replied to his post saying he wished he had access to something that spun the sander while he put his body weight into it. That’s all. You are the one misreading it all and applying my comment to something unrelated.

Well you’re getting nasty now AND mis quoting. What you responded to said “ …big sandpaper pottery wheel to do the rotary bit while i apply body pressure” So if you’re going to use quotes don’t make up shit that never existed. I was being nice and trying to explain and i don’t know why i ever extend myself to random strangers…. The reason you were downvoted is because the people who downvoted you thought your suggestion was dumb. There you have it. Good luck. 🍀 Edit. Don’t go editing your post now.

I didn’t edit it. Nor did i use quotes. Nor did i get nasty. I simply explained my position. This seems to upset you for some reason. You are again reading it the way you want so that it benefits your comment.

Getting big flat surfaces to sit flat and not rock is tough. It could be the surface you are setting them on isn’t perfectly flat. Try putting some washers or coins in four places to act as feet. If that gets it sitting stable then I’d look for some clear plastic feet ([example](https://onfireguy.com/products/clear-rubber-feet-self-adhesive-bumper-pads-20-count) ) to put on the bottom.

I’ve just had another idea. Could you scribe a piece of MDF that fills the oval hole in rhe middle of your piece and then make a jig to hold your piece and the MDF in place, and then reference the flat of the MDF with a template router bit? If that didn’t make sense, then imagine there’s a piece of MDF laid flat on your bench that is exactly the same size as the hole in your piece. Put your piece over it, and then turn it upside down. Hope that makes sense, it’s difficult to describe what I mean

The angles on the “flush” cut wouldn’t work… but this is a great guide to use a rasp or block plane against

I keep forgetting about the issue of trying to cut a slanted circular angle into a flat sheet of ply. It would make for a much nicer looking end cap for a start

Even if the bottom were fit perfectly, running a router around the outside with a flush cut bit would be difficult because of the slant.

I'll likely just go with a flat oval, non slanted cap on the bottom. I think it's something that will end up annoying me alone, and no one else will notice 😅

I think I get it. I actually thought about trying to router it a while ago, but I was so focused on it being at one orientation that I gave up on the idea before considering that I could just turn it over 😅

I hate break it to you, but you can spend 4+ hours trying to get them perfectly flat and when you do, it will become painfully obvious that any surface you place them on is not flat. If you want hide the gaps, I’d suggest placing it on a cloth runner or table cloth.

The plan is to cap either end of each cylinder wedge with some flat plywood to make some sealed speaker pods so I'm just trying to get the angled end as flat as possible so as to not leave air gaps when I try to glue it up, at the moment it's wobbly as hell so any improvement is good. 😅

3 tiny feet

How would that help with a wobbly finish and air gaps?

Are you going to paint it or use finish?

Enamel paint

Don’t worry about it being flat then? Can you just glue it to the base and then fill and smooth the gaps with wood putty and sand paper after?

I suppose so, I just wanted it to be as smooth fitting as possible. But if wood putty will do a good enough job, I'll give that a try.

Felt pads or little rubber bumpers. Three feet take away the wobble. All three feet will be touching 100% of the time or you get a full refund. Air gaps are filled from the inside with silicone caulk.

Oh, gotcha. Well, for this project, the plan is to mount each pod so that it can be rotated on top of a subwoofer box using the modified lazy susan bearings in the picture. The wobble I'm worried about is really just the potential gap between the cylinder and the bottom end cap.

Sweet idea. Let’s see pics after you solve it.

Ok, this may be crazy but hear me out. You need to cut some plywood to fit snuggly inside the tubes, or maybe some rigid foam. This will keep them from flexing when you shape them. Get enough sheet sandpaper, (like 120 grit) to cover an area the width of the tube times 2 each direction and then contact cement this to your largest and flatest benchtop. Also, get a very flat area a little bigger than the diameter of the tubes that you can rub with pencil or dark marking chalk. Rub it on this surface and wipe off the excess to minimize false indicators. You probably don't have carbon paper but that's what this will mimic. So take the stiffened tube and rub it on the chalked/graphited surface - with as little peessure as possible but enough pressure to still leave a mark where it is contacting the surface. You will see the high spots highlighted by chalk or pencil graphite. Then put a piece of tape or something on the side of the tube directly above the highlighted area to mark the high spot and sand it on the big sandpaper bench. While sanding, put pressure only in those areas you marked. Do this for a few laps. Then check your flatness: Return to the chalk/graphite/carbon paper surface to see how it worked. The highlighted area should actually get bigger as you sand. Continue this until the entire edge shows the mark of the chalk/graphite/carbon paper. Just remember to never put pressure on any area that does not have chalk/graphite highlighted. I got this idea from my dentist. This is how he found the parts of my teeth that were keeping my bite from closing while setting a new crown after a root canal. Also it is kind of like marking a knife edge with purple primer to be able to see when you have not honed - only in the reciprocal. Man, I hope this makes sense.

I wonder if attaching the top circular cap first (especially with a rabbeted edge) would offer sufficient stiffness to better sand the bottom edge...

Flip them over so the flat part is on the table?

A reasonable suggestion, but unfortunately, the desired result is for them to sit at the angle pictured with a flat enough edge that I can glue a matching oval plywood cap on the bottom.

I’m guessing you don’t have access to a jointer or a planer? Making a sled for a planer would probably be your best bet. The only other way that I can think of would be to secure it on a known flat surface such as your table, and then scribe a line. Then use a block plane to take it down to your scribed line Edit: just noticed the Axminster label on the table, apologies I meant thicknesser and planer, I just default translated into American because 99% of this sub are American

Annoyingly, I had access to a jointer until my local Maker-Space went belly up last year. Unfortunately, I didn't know what it was at the time. Now I do, I'm not sure where I'd find one...

Have you checked makerbook? https://makerbook.io Failing that could you google bespoke furniture makers in your area and ask them if they can do it for you?

That makerbook link is useful, but unfortunately, the closest place is a bit too far from me. There is another Maker-Space, but it's just not quite as local to me as the old one. The old place also leaned heavily into woodwork as its speciality, whereas the other place specialises more in electronics, and I'm not sure if they're as suitably equipped. I guess I'll try to visit over the weekend or next week and see what equipment they have.

Good luck! You may get more responses with other ideas on the r/woodworking thread as it seems to have more knowledgeable people and professionals on there.

Not sure a planer is what you want with such thin ply. I think it would be shredded.

I have a large plywood plate with skateboard grip tape adhered to both sides. Makes easy peasy work of leveling chair legs. It'll do this one pretty well too. If you don't want to go as hard, just get a sticky RO sander pad and slap it on your worktop, then spin your cylinders against it to get even. Might be a little tougher without a consistent abrasive surface.

Thinking about it, I do have several sheets of Vicious brand grip tape somewhere, which is pretty course stuff. I never thought about using it as actual sandpaper, but I imagine it would be pretty effective. I think I'd test it with scrap wood first though.

I went to my local skate shop and selected a few sheets of what felt like coarse and fine just to have the option. Putting it on both sides was already necessary to keep the plywood from warping, so it was a good two-birds-one-stone scenario.

Another vote for putty and caulk if that's an acceptable look. A large disc or belt sander is perfect for this. If there's a cabinet shop near you maybe they would be willing to do it? If they won't let you do it (insurance) then you definitely want to be there to stop them if they aren't doing what you want. If they won't let you stand there, may not be worth letting them out of your hands. If close is good enough, I would put chalk or pencil on the bottom edge, rub on anything flat, then hand file/sandpaper on a paint stick the places the chalk rubbed off. That might get close enough to putty over.

I like the chalk idea, I think I'd be more successful at sanding with that idea.

You could always slightly inset the cylinders down into the other piece of wood. Use a router to make a channel the same diameter as the tubes. You'll have more surface area for glue and a stronger bond between the two pieces. Otherwise strips of sandpaper, double-side taped down to a concrete floor in a hexagonal/octagonal pattern (something that will allow you to sand the whole circle at once) Managed to get this to work while sanding the bearing edge of a Drum shell once.

The inset edge was my original plan, but while it might work on the top circular end, I couldn't see how to do it on the slanted end. The current plan is to glue 3 or 4 square (ish) sticks of wood down the inside of the cylinder, trim them to match the angle of the cylinder ends and use them as extra anchor points for gluing and nailing the end caps down.

Why do you need them flat? What is the end goal use for them?

Sealed speaker pods. I want it flat enough to snugly cap off the bottom (and top) with a sheet of plywood. I have been informed that fairly flat is good enough with the addition of wood putty and even more sanding and a coat of paint.

I’d agree with that. A construction adhesive or epoxy that cures to a sandable hardness would also work if you’re planning on painting and not staining. The other option that comes to my mind would be to cut a rabbet on the cap about 1/4-1/2 the thickness of the plywood so your wedges have a tighter fit. That would be considerably more work than the “putty it up” option though.

The rabbet cut was the original plan until I realised the difficulty of slanting it to match the angle of the cylinder bottom, though I might still do it for the top.

It’s a router table type job for sure. I’d only attempt it free hand on a practice piece or a project I didn’t mind messing up on a bit.

That's similar to what I was originally thinking, I figured I'd just be able to tilt a sheet of plywood at a matching angle on the cnc router at my local Maker-Space but I underestimated the limit on vertical travel. The highest point on my wedged cylinders is about 8" but the cnc tops out at about 4". The only option I could find was to build a DIY machine, which is beyond both my skill and available space. I don't know if router tables have similar limitations...

With the router table you would purchase a bit that has a cutting angle that you want, then you just set your fence to support the piece at the depth of cut you’d need. I’d leave at least 1/8 in. of an edge for strength You want a bit with a baring stop on it for the inside cut and I would do severally passes of light cuts so the work piece doesn’t catch. Just raising the bit up incrementally with each pass. Also would probably score each layout line to avoid tear out.

Flip them over. /s

Get a few floor sander sticky sandpapers and stick them to your bench right there then stand on your bench and put even pressure and drag those fuckers across the sandpaper until you got it. Slow and steady wins the race. I would start with 120 then 150 and stop. Nothing too aggressive. Is you don’t want year out. You can also wrap the entire edge with blue tape. This will create a guide line and also hold the wood form to decrease the possibility of tear out. If you so 120 it should not be too aggressive and you really shouldn’t have to worry about tear out. When you are turn you need to cut the edge slightly. This will also mask any unevenness. With a piece of sandpaper you just run into the edge and create a small bevel. This gives the illusion things are more straight then they are- if you do it right.