I'm talking about the sticky back piece that is permanently attached to the drum... the 12 x 24 pieces...
So that 'could' be pieced together?
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Yes, I think it would work fine. It doesn't have to be spiral wound either. Your drum needs to be coated with something that hardens and smooths the surface. I don't know how strong the adhesive is when applied to MDF that is fuzzy.
The adhesive is the most aggressive I have ever dealt with when applied to clean freshly machined PVC surface.
That's why I was clarifying that the sandpaper layer is the one that should not be spliced because it can snag.
CarveOne
I was planning on sanding and sealing it all with water based polyurethane before applying the backing.. Think that would work?
The smoother the surface is the better the grip, up to when the poly peels off. :) It should penetrate the MDF fairly deeply, but I don't use the water based kind on MDF, so I'm not familiar with how much it will make the MDF grow. Try it on a scrap piece unless you already know that it works ok.
CarveOne
Water based polyurethane take about 30 days to fully cure. I wouldn't stick it before that.
I think that anything that penetrates too deeply, might throw off the balance. How about spray lacquer?
Doesn't Lacquer take a long time to cure as well?
No, a few light coats will each dry in a few minutes, and it should be fully cured overnight.
We've shipped millwork 2 hours after spraying it.
I did a little reading, and it seems to not fully cure for a week or two, maybe more. At least that's what's recommended before rubbing out a lacquer finish.
However, it'll be hard overnight, where as water based poly will still be soft a week later.
I know that I can sand water based poly within two or three hours no problem... but if I try to sand lacquer that soon (even the next morning) it will gum up the sand paper and pull gum all over the piece being sanded...
I'd be tempted to use a thin coat of 1 hour epoxy...
Some Pictures of yesterdays efforts...
Here's the feedbelt frame, cut, squared and ready for welding..
http://www.mountaincraftworks.com/pi...eedbelt004.jpg
http://www.mountaincraftworks.com/pi...eedbelt005.jpg
And here is it after welding... I will be welding a 1/4" x 6" x 30" piece of steel on each underside of the thing today, for mounting all the support structure to (for raising lowering, etc.)...
This frame will hold the feed belt, as well as the infeed and outfeed tables, and the backing table under the belt...
http://www.mountaincraftworks.com/pi...eedbelt006.jpg
http://www.mountaincraftworks.com/pi...eedbelt007.jpg
And here's a couple of the first drum... Pieces are just dry fit for now... I'm not going to glue them up until the table is a lot farther along in the assembly, so that I know exactly where on the shaft I want to put them, and I can cut the shaft to it's final length without the discs on it...
http://www.mountaincraftworks.com/pi...eedbelt008.jpg
http://www.mountaincraftworks.com/pi...eedbelt009.jpg
I don't know what kind of lacquer you used, but it should be dry enough to sand in about 30 minutes or less, unless you're spraying too heavy.
Keep in mind that lacquer just doesn't sand as easily as water based poly does. It will gum up paper, even when dry. Use stearated (white) sanpaper and you should get better results.
That's why they make lacquer sanding sealer, which is easier to sand.
So, I've had a couple setbacks.. When welding up the feedbelt frame, it distorted the unistrut slightly, bending it.. I was trying to avoid that by welding in small bits, but in hindsight I should have welded the business end of the strut 'first'.. So it's causing sticking on one side of the adjustable end of things.. So I gotta take it all apart, and grind that a bit, and then I think I'll reverse ends as the other end seems to still be straight and true...
When I picked up the used thickness planer I bought yesterday, I took a few minutes to check out how the beltfeed was installed and adjusted on it.. It's a smaller machine, with a larger diameter drum, open ended on the feed, with the adjuster raising and lowering the drum housing...
It's a smaller belt in both width and length, and it appears that the rollers are not crowned at all.. It also doesn't use any 'springs' but just has a screw tensioner on each side of the one roller...
I think the key will be to get the 'fixed' roller 'very square to the frame, and then just carefully adjusting things... In any event, I have a plan 'B' should I not be able to get the belt feed working...
The plan is to build the main frame, using vertical half inch rods at each of the four corners for the belt feed frame to slide up and down on.. These will keep it from shifting or canting as the mechanism underneath adjusts the height of the belt feed frame.. I'm planning to initially, use 1/2" threaded rod in these spots and just use wing nuts to adjust the height in the four corners during start up and initial testing.. I'll build the beltfeed lift/adjuster last..
I also ordered the aluminum Tee slot and knobs that are to be used on each side of the drum enclosure.. These will be for mounting and and adjusting a tilt fence on top, where the top of the drum will be exposed (removable cover) for hand feeding it the opposite direction (like many of you have your drum sanders set up)...
Have most everything worked out in my head.. with dust extraction being the last major hurdle...
Okay, a bit more progress...
Here's where I was when I discovered I had a problem..
I had mounted everything on the newly constructed feedbelt frame, and discovered the binding, and the belt wouldn't track very good...
http://www.mountaincraftworks.com/pi...eedbelt010.jpg
http://www.mountaincraftworks.com/pi...eedbelt012.jpg
http://www.mountaincraftworks.com/pi...eedbelt013.jpg
http://www.mountaincraftworks.com/pi...eedbelt014.jpg
So then I took it all apart, took a hammer to things to widen the strut where it narrowed, and then reversed everything so that the fixed end and the sliding bearings were flipped on the frame.. Then I ditched the springs..
The whole thing seems to track way better.. seems to not walk at all anymore, but I won't know for sure until I put power to it... It is also a lot easier/faster to adjust now...
http://www.mountaincraftworks.com/pi...eedbelt015.jpg
http://www.mountaincraftworks.com/pi...eedbelt016.jpg
I need a new welding helmet so I can see what the heck I'm doing.... Half my welds wandered off the joint.... Then the switch on the handle was acting up, and I ran out of gas... Perseverance.. not real pretty, but solid and square where it needs to be.. :o
So next I'll cut the infeed and outfeed tables out of 1" MDF, as well as the center underbelt support table, and get those mounted.. Will probably glue some #16 sheet metal on top of them... I also priced out the steel I need to build the main frame, and that is what I'll work on after the feedbelt tables... So far so good...
When a hammer won't tune it into spec, get out the 5 lb hand maul. Works every time for ME. :)
Will there be an aluminum plate between the belt axles to provide a solid support surface? I never looked inside a wide belt sander before. The 6" one I have has a cast aluminum surface behind the belt rollers.
CarveOne