Increase strength of the edge of MDF?

[DaOld Man]

I am currently working on a rotating monitor project in the Project Announcement forum.
I have cut a circle out of 3/4" MDF.
I plan to mount the monitor in this circle, then have the edge of the circle ride against bearings to allow rotation.
My question is:
Is there a way to strengthen the edge of the MDF so it wont fray or fail during years of riding on the bearings?
I was thinking of a coating that will soak into the wood and bond it.
Such as elmers wood glue?
Any thoughts on this?

edit: posted a pic that might better explain what Im asking..

[EwJ]

Some possible options?
1)Slot it and run some t-mold around circumference?  Don't know if that would enable it to grip better or cause it to slip, but if it wears it's easy to replace.
2) Trash the MDF and use a good hardwood.
3) Glue some rubber like old bicycle tube material around circum.
edit: add 3)

[Jdurg]

Use some type of epoxy, then take a very thing strip of aluminum that is the same width as your MDF and epoxy it to the edge of the cutout and then the circle.  You'll then be able to use something like WD-40 or a lubricant to ensure smooth turning.

[ChadTower]

Hrm... it may be the MDF is just the wrong material for that.  If you must use it I'd seal the edge with some sort of epoxy for strength.

Don't use WD40.  It is not a lubricant, it is a cleaner.  It actually attracts debris and makes things worse when you try to lubricate with it.

[DaOld Man]

Hmmm I like the idea of using epoxy, then putting a strip of thin metal over the edge.
Whats that strip called that is used to cover two edges of linoleum?
if I could find one 3/4" wide would be neat.
I havent used that material in years, but I think it has small nail holes in the center of the strip, may not be desirable for this because the holes might bump against the bearings.

[sstorkel]

A) Plywood is lighter, stronger, and stiffer than MDF. I would expect it to last considerably longer...

B) You can use a thinned, 2-part epoxy to reinforce the edges of the MDF. By the time you've found it, mixed it, treated the wood, and recovered from the fume-induced headache you'll probably wish you used plywood to start with. There's a product called "RotFix" that has the exact consistency you need, but it's expensive. I don't think there's anything special about the epoxy they use, you're just paying for the convenience. You can probably buy a generic epoxy from System 3 or West Systems for a lot less.

[Jdurg]

Hmmm I like the idea of using epoxy, then putting a strip of thin metal over the edge.
Whats that strip called that is used to cover two edges of linoleum?
if I could find one 3/4" wide would be neat.
I havent used that material in years, but I think it has small nail holes in the center of the strip, may not be desirable for this because the holes might bump against the bearings.

I was just at Home Depot looking at aluminum strips with a friend of mine who is building a trailer.  I believe they have 1/20" thick aluminum strips that can be used to cover the edge of your MDF.  At that level of thickness, even if it's a bit wide you can easily cut it with some shears.  Aluminum is very light, very flexible, but will also hold up to the rotation of your monitor in there.

[EwJ]

Thin aluminum would be easy to work with.  If you go that route and they don't have thin sheet stock at the local hardware store, any machine shop could likely shear you off a strip the thickness of your mdf inside of a few seconds for cheap.   Another good source is soffit/fascia/aluminum siding companies.  If there's any house construction in your area, the soffit installers would prob be happy to shear you off a strip on the cheap - they usually have rolls of thin stock on hand to cover window frames, etc.  Epoxy or maybe contact cement in place and would be very easy to trim to exact length on assembly with some aviation snips.
Just noticed your project thread for this - off to read it.
Good luck.
 

[DaOld Man]

You guys dog-talking using MDF for this may be on to something.
But Im hard headed, and since Ive already got the stuff cutout, I am going to try to make it work 
Thanks for the aluminum strip info guys, looks like I got to plan another excursion to home depot.
(Those people are making a fortune off my projects.  )
EWJ: Im not the only one working on rotating monitors.
Be sure to read everyones posts. Most others are using LCD monitors, mine is CRT.

[Franco B]

If you stuggle to get some aluminium give me a shout. I have some sheet at work that would be ideal. Let me know the circumference and ill cut you a long 3/4" piece.

No charge, just pay shipping.

[shardian]

I think everyone in this hobby gets carried away with MDF. It should only be used in projects that will be painted and on which wood grain is undesirable. For structural and mechanical functions such as you are doing, you should definitely not be using MDF. Do yourself a favor and scrap the MDF for this circle and go buy a $5 1/4 sheet of sanded ply.

[DaOld Man]

If you stuggle to get some aluminium give me a shout. I have some sheet at work that would be ideal. Let me know the circumference and ill cut you a long 3/4" piece.

No charge, just pay shipping.

PM sent

[DaOld Man]

I think everyone in this hobby gets carried away with MDF. It should only be used in projects that will be painted and on which wood grain is undesirable. For structural and mechanical functions such as you are doing, you should definitely not be using MDF. Do yourself a favor and scrap the MDF for this circle and go buy a $5 1/4 sheet of sanded ply.

Thanks Sharidan, I value your opinion..
I chose MDF because it is very smooth. I may have to go with plywood.
That door aint closed yet.
I am using a pretty heavy CRT, do you think 1/4" ply would be strong enough?
Also I do plan to prime the MDF, to seal it.
I have applied some PVC glue to the edge of a piece of scrap.
I'm working midnight shift this week, so I havent had a chance to test it.
But it seemed to soak up pretty good.
I tried two pieces, one with CPVC glue, and the other with all-purpose PVC types glue.
I will post what I find when I get back out to the shed..

[whammoed]

do you think 1/4" ply would be strong enough?

1/4 sheet, not 1/4"
as in a 2 foot by 4 foot sheet of plywood.

[shardian]

1/4 sheet, not 1/4"
as in a 2 foot by 4 foot sheet of plywood.

What he said.

[DaOld Man]

Oops, my bad...

I found a sheet of ply in my wood pile, Its either 1/2" or 3/4" thick (Pretty sure it's 1/2. I haven't measured it yet.)
Anyway, I think I will go ahead and cut out a piece of it.
If the MDF looks like it is wearing on the edge, I can easily swap it with the ply.
Thanks for the input guys..

[ChadTower]

You may still have edge issues depending on whether or not there are any voids, but if there are, you can just bondo those and put the aluminum over that.

[Paul Olson]

Where can you find 1/4 sheet plywood for $5? I had to buy 1/4 sheet MDF last week and it was almost $9 at home depot. I live in Reno, are wood prices really that much cheaper in other parts of the country?

[shardian]

Where can you find 1/4 sheet plywood for $5? I had to buy 1/4 sheet MDF last week and it was almost $9 at home depot. I live in Reno, are wood prices really that much cheaper in other parts of the country?

Home Depot and Lowes both have 1/4 sheets of 3/4" sanded ply for $5. I suppose out west the prices can be higher. Wood in general is thru the roof in price - and quality of said wood is thru the floor.

[scotthh]

How much pressure do you think the wood is going to get? Perhaps you should just seal the cut ends of the MDF with a PVA glue or a watered down PVA glue mixture. You mentioned Elmer's in your first post, and I've been using Titebond II for a number of different projects and was happy enough to buy a second bottle of it.

I've attached links to two threads that are more about sealing MDF for painting as opposed to for strength, but I think they're relevant:
Best way to seal/paint MDF
Fozzy's post in spray painting MDF thread

[DaOld Man]

Well, what I am doing is creating a disc to mount a CRT to.
The CRT weighs approx 50 lbs (?)
I am going to use skate board bearings as the support. each bearing has an outer diameter of about 1-7/8"
The race width is about 1/4"
I plan to double them, so there will be contact across most of the width of the MDF.
I plan to have 3 support bearings on the bottom, at about 8:00, 6:00 and 4:00 (o'clock).
I havent figured out how much weight will be at each spot on the mdf.
Its probably not going to be an issue, but I know how easy MDF dents when you drop it on its edge.
I did seal the perimeter of the MDF circle with all purpose PVC type glue.
That looks pretty good.
Thanks for the links, i will check them out.