Teaching Microscope Table

[jdbnsn]

More progress today, I hope to get the other side done tonight.

[DonT-FeaR]

another quality build

[jdbnsn]

Thanks bro!

I got a little more work done. To support the axles I cut 4 small blocks and drilled holes in them and the inner panels.

Then using some scrap stainless steel I cut and bent brackets to support the axles, eight in all.

Then I used 29/64" drill bit to countersink the holes from the inner side to fit some nylon spacers I picked up. This will keep the wheel pedals from rubbing up against the MDF on either side.

I have removed all of the brackets and stacked waiting to be sandblasted and painted. Last thing for tonight is covering up that ugly pine with some plastic. I dropped by the local plastics distributor and picked up some ABS (acrylonitrile butadiene styrene) and used it to cut panels fitting the triangle shaped braces. Tomorrow I'll do the same for the cross beams.

[DonT-FeaR]

looking good.... i like it

[SgtM]

Awesome build Jon! When can I use it?

[jdbnsn]

Thanks fellas! And Rick, anytime you want to come on down to Kansas and peek through the scopes or watch an autopsy you're more than welcome! I've gotten a bit more work done but haven't got the pics off my camera yet. Maybe tomorrow.

[jdbnsn]

Okay, got some pictures of the current state of progress. I hope to slap a coat of paint on this puppy today and finish it up within coupe of days.


I sandblasted the stainless steel brackets for two reasons, there was some paint from it's original purpose (that I don't know since it was scrap that I kept from an old job) and the sand blaster leaves a nice looking texture. When drilling, grinding, filing, and sanding harder metals like steel it's pretty tough to get the scratches and defects out but the sandblaster paints away all of those things with ease. Here are the brackets after a pass with the sandblaster.

Here you can see the difference between the original paint (which barely scuffed on a bench grinder's wire wheel, heat stripper, or scraper but came right off with the sandblaster).

I lined them up and hit them with a couple of coats of primer...

Now if you've ever worked with MDF you know that it has a unique set of properties that make it both beneficial and cursed. It's pretty heavy and dense, it cuts very nicely, can be shaped with a router easily, and sanding is a breeze, which all make it nice to work with when building simplified furniture/cabinets, etc...

The downsides are that it is not very strong (i.e. flexible and will bend out of shape if a long enough piece is left with room to sag), it chips very easily when drilled, cut, or even bumped against a strong surface. One property of MDF which can be a big problem is it's vulnerability to moisture. If your MDF stock gets wet, it's over. Anytime you finish MDF you must seal it with water-free primer and paint, 100% acrylic based primer is a good choice, stay away from latex paint/primer.

The composition of MDF is basically very fine sawdust and a mixture of glue which includes wax resins and urea-formaldehyde which can be quite harmful if you do not wear a respirator while cutting and sanding. And since the sawdust base is so fine, cutting, sanding, or any such action causes huge amounts of powder to become airborne.

Now, I'm pretty close to being ready to paint so I have to fix an inherent problem with MDF. If you try to prime MDF you'll find that the edges soak up the paint as fast as you apply it due to it's highly porous nature. So google taught me a little trick. Take some wood glue and dilute it with water (use 3 parts glue to 1 part water) and paint the edges with a couple of coats of this mixture and let it dry for a couple of hours sanding in between coats. Since the water is mixed with mostly glue, it doesn't cause swelling. This is what I did on all of the edges that will be painted...

I painted the brackets with some Krylon black spray paint and screwed then in position to mark the holes for the mounting screws.

Almost ready for it's paint job...

[jdbnsn]

Today is going to be mostly painting.

I wanted the screws to match the brackets and I couldn't find black screws at the hardware store so I decided paint the screws that I had. I know it will not hold up when being screwed in place but I'll touch that up as I go.

This is the primer/sealant that I am using...

Got a first coat painted on...

I decided to test the edge-absorption theory I read on the web by painting an edge that will end up being sanded down later anyway and it's very true. It doesn't show up well in the picture but the edge on the left of the base was sealed with the glue/water mixture and the edge on the right was not. Even after 3 passes with the brush it still needs more to be sealed. So the glue and water tip works great!

[Luke122]

Killer work Jon!

[jdbnsn]

Thanks bro!