New Material for MFT tops, HDPE

[Warrior]

I recently had to purchase some frosted plastic for some light diffusers and priced out some other plastic while at the shop. I am thinking about having a MFT top made from 3/4" HDPE. The plastic shop has a CNC machine that will cut it to size (915mm x 2030mm) and bore the 20mm holes in 96mm OC pattern. While this is very expensive I think it is worth it. The HDPE is very flat and extremely ridgid, will not harm any cutters ( I will not be cutting into it), and no adhesives will bond to it. It has a textured surface so it won't be to slippery. I have made 3 large MFT tops so far and am getting tired of having to spend extra time protecting them from squeeze out. I may want to make 2 tops out of the one 4x8 sheet instead. I'll have to think about that one. The cost of the sheet is 375.00 plus 90.00 for the CNC machining. As long as I don't cut it up the top should last forever.

What do you think?

Eiji

 

[Brice Burrell]

Well, the price is pretty high for the HDPE, I'd rather just keep making or buying MDF tops. It sounds like your main issue is glue, it so have you tried putting some type of finish on your MDF top to offer a little protection? I would spend the money on another MFT, but its not my money we're talking about. I'd be interested in hearing how it works out if you decide to go for it.

I just had another thought, how about a thin layer of HDPE that you could put on top of the MDF when gluing??

 

[Warrior]

Brice,
I have yet to buy one MFT. I have just made my own. They are just too small for me. My work surface needs to be around 36 x 80 or 915mm x 2030mm for me to be able to build anything on it. I know you can connect them but to me it doesnt make any sense to have to bring 2 mfts, connect them and level up 6 legs when I can just bring my 1 large mft and set it up in about the same or less time than it would take to set up one MFT. Plus my MFT is nearly as solid as a traditional bench.

I use the holes in the top to keep my glue ups flat so a thin sheet would not help.

Eiji

 

[Mark Carlson]

I've been thinking about making a MFT top out of phenolic plywood.  Glue is easily removed from phenolic and you can get a 3/4 in sheet
for about $70.

~mark

 

[JayStPeter]

I've used 2 different solutions for the same problem in my shop.  First is simple formica.  Second is a replaceable hardboard top layer on top of a ply or MDF surface.  I use both on various surfaces in my shop and will continue to do so.  One of the problems with formica is that it is sometimes too slippery to reasonably hold things in place  But, it does repel glue well.  It does stain when it gets wood stain on it though.  I purposely don't use formica on some surfaces (including my assembly table) because I didn't want the surface that slippery.  A buddy of mine just made a work table top out of 2 layers of 3/4" ply with a piece of 1/8" Aluminum on top.  I kind of like that one, it doesn't look that great though since it scratches easily.  But it repels almost everything.

 

[Warrior]

i still like the HDPE idea since it is not just a layer on top and if any glue drips in the holes it wont stick. I need it light enough to cart around to the job and it seems I am always chipping my mdf top. The lack of friction my be an issue but since you want to clamp everything down anyway this is most likely not a big deal. I think that when sanding or light routing the sanding/routing pads would stick alot better. If I do this I will never have to make another MFT top. Unless I want another one. IF I dont, I easlily see myself making at least 5 replacement tops in the next 10 years. With getting the material, cutting and routing the holes it is at least a 2 hour operation. That is about 180.00 for a 3/4 top and 210.00 for a 1" top each. That is figuring the value of my time or the opportunity cost in making the top myself.

 

[ericbuggeln]

Eiji, you may want to look into Benjamin Moores Industrial moisture cured urethane.  It is used for public buildings, basketball courts, etc.  Extremely durable.  Eric

 

[Eli]

Well I think it sounds like a good idea. If you think the cost is worth it, the material sounds like the killer app. See if they have it in lime green.  ;D

 

[semenza]

Hi,

      It sounds like a great material for a top. How sure are you about it not sagging though?    Also how much cost saving  (and weight savings) might there be , using  3/8" or 1/2" HDPE with a little more cross support underneath?

Seth

 

[Warrior]

Hi,

       It sounds like a great material for a top. How sure are you about it not sagging though?    Also how much cost saving  (and weight savings) might there be , using  3/8" or 1/2" HDPE with a little more cross support underneath?

Seth

I didnt even think about using 1/2". hmmmmmmmmm maybe. I will explore that option but I think I will stick with the 3/4. My top extends out past the bench about 3-4" without support on each side and is about even on the ends. When I want to work on doors I have the top even with the support on one side and all the overhang on the otherside. Unless I change that then I'll have to stick with the 3/4.  I'll check the weight and post it when I get the info.

Eiji

 

[Warrior]

The top will be a little heavy. the 36 x 80" top will weigh in at 59.4 lbs. after the holes are bored. My 1" MDF top the same dimensions weighs in at 68.5 lbs. and I have no problem throwing it around. So I guess it wont be an issue until I'm Seth's age. ;D Then I'll make a special lifting cart to go with my bench. ;D 

I got my figures by calculating the cube cm x density. HDPE - .95 and MDF- .7  grams/cubic cm.

 

[b_m_hart]

It sounds like a sound business decision to me.  I think it really boils down to what you value your time at.  I'm guessing that you spend more than just a trivial amount of time making your MFT tops.  If you had the time you put into making those three tops back, and used it to do billable work, would you come out ahead of the $465?  If you do come out ahead, then buy it.  If not, then I guess you'll have to figure out how much time it will save you in the future, then factor that in...

It also sounds like there are some other tangible benefits that are harder to attach a monetary value to, such as the glue aspect that you'll have to figure in as well.  Also, what did you spend on materials for the previous tops you made?

 

[Les]

Eiji,

You haven't replied about putting a poly barrier on your MDF top. Have you tried that? It works for me. Any squeeze out or drips scrape right off.

It sounds like your HDPE top would be the ultimate top. Have they given you any info on tolerances? Using the holes for alignment and squaring is a big plus.

 

[Warrior]

Les,
Applying poly to the MDF top is time consuming considering getting the poly onto the surfaces in the holes as well. Also the end grain of the MDF is so porous that it is hard to seal.

I havent given the tolerances that much thought since all the holes would be drilled out on a CNC guided router. I just assumed that it would be accurate with a CNC but I will find out what the tolerances are. I do need to figure out if the top will sag or distort with temperature differences. I know that my MDF top moves a lot if I am in a sunny area and want to cup. I just flip it over and it flattens out and starts to cup again as the top side gets hot in the sun and the underside stays cool. Sorry for the run on sentence but you know what I mean. This is never an issue inside regardless of humidity. I would have to think (but I'm not sure) that this would be less of a problem with a white plastic top. Maybe I should just always set up in the shade. I just hate going out side in the sun to cut just after being inside installing or visa versa. Making my eyes have to readjust all the time drives me nuts.

 

[poto]

Hey Eiji - off topic, but since you brought up the problem of your eyes adjusting when you go from inside to outside on a sunny day, you might consider doing what the pirates did: wear an eyepatch! The eye patch will stop one eye from adjusting to the bright sun so that when you go inside, you just lift it up, and presto - you can see! Pre-adjusted for the dim light. It really works. I saw it on Mythbusters, so it must be true!

Poto

P.S. Bet I'm the only person in Hong Kong right now wearing a Rotex anniversary Festool watch!

 

[Dave Rudy]

P.S. Bet I'm the only person in Hong Kong right now wearing a Rotex anniversary Festool watch!

Guaranteed you're the only one with a Rotex watch AND an eyepatch!

 

[Tim Sproul]

I would worry about dust and the HDPE and static electricity.  Plastics build up static and this can attract dust like crazy.  Not sure if it will be a problem or not....just something to ponder.

 

[b_m_hart]

I would worry about dust and the HDPE and static electricity.  Plastics build up static and this can attract dust like crazy.  Not sure if it will be a problem or not....just something to ponder.

Attach an anti-static strip to it, and find something to ground it to from time to time and you'll be fine, wouldn't you?

 

[robtonya]

I was going to replace my router table fence with some 3/4 in. HDPE. I liked the idea. And a table top sounds even better to me.

 

[Rescue U]

Try applying a coat of silicone free wax to the surface of your mft, it will resist glue and spills.  Works great for me, just allow it to dry for a day or two.