Granite Surface Plate

[Deanimator]

I picked up a great tip on YouTube this morning.

Instead of trying to grind off the mill scale, I'm going to soak the plate in vinegar for a couple of days (possibly only one). Theoretically the scale should rinse off so that I only have to remove the sharp edges and smooth the surface before painting.

I picked up a large tub and three gallons of vinegar on the way to work last night. I'll submerge the plate in vinegar at a friend's place tonight before I go to work. I'll take a look at it tomorrow.

[Deanimator]

The plate was too big for the tub.

I ended up buying a cheap blow up kiddie pool. It took 5 1/2 gallons of vinegar.

As it turned out, the vinegar leaked out over night, but it did its work anyway. It removed the scale.

This evening, I did most of the angle grinder work, wire brushing off the surface rust that appeared after the vinegar removed the scale, and breaking the sharp edges. There's still rust on one edge and a few sharp edges. I rubbed it down with WD-40 to keep it from rusting again.

I won't get back to it until Sunday afternoon. I'll remove the reset of the rust and make sure all of the sharp edges are gone.

While I was waiting for the friend who's garage I'm using to get home, I used a piece of aluminum bar stock to make a drilling template. I redesigned the configuration so that the horizontal piece is always in place, with the vertical member bolted to it when necessary. It now only requires three holes for M8 bolts. I ran out of T-nuts, so I ordered some more. That'll give me enough for mounting the horizontal member to the plate and all of the bracing to mount the vertical member.

I'm using a small linear bearing as the base for the subject stage. I had originally purchased a lever brake handle for it, but it's too big to work when the horizontal profile is mounted to the plate. I found a knob small enough to work, especially with a larger platform mounted to the bearing.

Painting MIGHT get done next Monday.

[Deanimator]

I got the three center line mounting holes for the profile done. It took way longer than it should have because my first pilot hole was done with a crappy drill bit, probably sub-Harbor Freight quality. Things went much faster when I switched to better larger sized bits for enlarging the holes. The final 25/64" holes were done with a good DeWalt(?) bit.

Layout was tough because:

1. I didn't have something long enough to mark the scribe lines from end to end. At the far end, I had to wing it.
2. The edges of the plate aren't square. They don't need to be in order to use it, but it makes it hard to lay out the holes without a square side for reference.
3. The YouTube suggestion of using a scratch awl to deepen the scribe marks where they cross was a bust. I just dulled the point on the awl.

On the plus side, a Sharpie is an excellent substitute for Dykem.

I'm not sure the holes are exactly in line, but they're well within the tolerances of the slot in the bottom of the horizontal profile. My flat head screws turned out to be too long, but that's easily remedied by grinding or replacing with shorter screws. (I ordered a selection of lengths from Amazon last night).

I didn't get to the handles. It's in the '60s in Lakewood, Ohio, but in the high '80s in my buddy's garage. I was worn out after laying out, drilling and countersinking the three holes. I'll drill the holes for the handles and paint the plate next Sunday and Monday.

[Deanimator]

I drilled the holes for the handles today. The holes in the handles were smaller than 1/4". I drilled them out to 17/64" for a loose fit. I only drilled one handle as I've misplaced the other one someplace, probably in my friend's garage. Hopefully, I'll drill that one out tomorrow.

I tried attaching the 80/20 with the right length screws, and it's solid. It's visibly cocked to one side, but the plate isn't exactly square and I designed the rig so that the plate is nothing but dead weight and a place to set accessories (lights, etc.). The rail could be at a 45deg. angle to the long axis of the plate and it wouldn't affect usage one bit.

I'm going to go back tomorrow morning, clean up any surface rust, degrease with Zep, and put on two coats of primer, and at least one of paint. At least in theory, it should be ready to take home Tuesday before I go to work.

[mawyatt]

I found that muratic acid (dilute HCL), or swimming pool acid, diluted, scrubbed on with an old toothbrush works well on rust. This is what we use for marine SS when it rusts, the acid attackes the rust and oxidizes the Chromium in SS which acts as a barrier for more rust.

Be careful, use proper technique with acids and wear latex gloves when using.

Best,

[Deanimator]

I found that muratic acid (dilute HCL), or swimming pool acid, diluted, scrubbed on with an old toothbrush works well on rust. This is what we use for marine SS when it rusts, the acid attackes the rust and oxidizes the Chromium in SS which acts as a barrier for more rust.

Be careful, use proper technique with acids and wear latex gloves when using.

Best,

This is just a little light surface rust AFTER having removed the mill scale with vinegar, which even though it leaked out, did a very good job.

I'll probably just go over the plate lightly with a 120grit flap disk, degrease and wipe down with a microfiber cloth before priming and painting. The key appears to be light coats applied quickly. I'm not painting a hot rod or a high power rocket, so I just need to do a reasonable job that'll prevent rust and not flake.

[enricosavazzi]

I found that muratic acid (dilute HCL), or swimming pool acid, diluted, scrubbed on with an old toothbrush works well on rust. This is what we use for marine SS when it rusts, the acid attackes the rust and oxidizes the Chromium in SS which acts as a barrier for more rust.

Be careful, use proper technique with acids and wear latex gloves when using.

Best,

This is just a little light surface rust AFTER having removed the mill scale with vinegar, which even though it leaked out, did a very good job.

I'll probably just go over the plate lightly with a 120grit flap disk, degrease and wipe down with a microfiber cloth before priming and painting. The key appears to be light coats applied quickly. I'm not painting a hot rod or a high power rocket, so I just need to do a reasonable job that'll prevent rust and not flake.

A couple coatings with primer will usually make the paint more resistant to peeling than applying the paint directly on metal.

[Chris S.]

I agree, Enrico, but apparently, Deanimator does too. (Emphasis mine in his quote below.)

A couple coatings with primer will usually make the paint more resistant to peeling than applying the paint directly on metal.

. . . clean up any surface rust, degrease with Zep, and put on two coats of primer, and at least one of paint.

--Chris S.

[enricosavazzi]

I agree, Enrico, but apparently, Deanimator does too. (Emphasis mine in his quote below.)

A couple coatings with primer will usually make the paint more resistant to peeling than applying the paint directly on metal.

. . . clean up any surface rust, degrease with Zep, and put on two coats of primer, and at least one of paint.

--Chris S.

I just wanted to make sure he did not forget, since he did mention "not flake" in his last post. These threads will always be useful as a general reference, anyway.

[Deanimator]

A couple coatings with primer will usually make the paint more resistant to peeling than applying the paint directly on metal.

Thanks for the reminder.

I've watched a number of YouTube videos on painting metal, and read posts on other forums. And that's the recommended method, albeit there's a lot of disagreement regarding drying times between coats.

I'm going to go with a couple of light coats of primer within an hour, followed by a couple of light coats of gloss black in the same time frame.

[Deanimator]

I found the second handle and got it drilled out.

I got the plate primed and painted. I ran into some problems with the wind blowing the drop cloth that the plate was sitting on up over it. Some of the pain pealed away with it. I repainted, but some of it pealed. The plate will dry overnight. I'll probably have to repaint those spots on the edge.

The plan is to attach the handles tomorrow and take it home before work.

[Deanimator]

I picked up the plate today.

The paint at the rear of the upper side is indeed screwed up. It peeled away with the plastic down to the primer. It's a relatively small area. Any repair suggestions?

I haven't had time to clean all of the still life gear off of the table yet. I'll probably try to do at least a little after I get home from work tomorrow morning.

Even with the handles, it's a bear to move. I'll probably bring in from the car tomorrow morning and lean it against something so that I can get the screws and T-nuts installed so that I can slide the 80/20 on and tighten it down.

I've got four of the heavy duty Sorbothane hemispheres for it to sit on.

[enricosavazzi]

[...]
I've got four of the heavy duty Sorbothane hemispheres for it to sit on.

Sorbothane is the best material for dampening vibration, but under continuous load it tends to flatten a little with time.

If it is overloaded, on the other hand, after a few weeks it can slowly split into pieces like a dropped watermelon. I had this happen to me with an excessive load. At the beginning it seemed to work fine, but after a few weeks I had to pick up the pieces.

You may want to hold up the plate with wood wedges under the corners, or similar supports, when the equipment is not in use, so that the sorbothane feet are not under continuous load. If the load on the feet seems excessive, you may want to double or quadruple the number of sorbothane hemispheres.

[Chris S.]

Also, if the Sorbothane isn't sufficiently loaded, it won't dampen as effectively. My sense (IIRC), from running and re-running calculations using Sorbothane's free software, is that properly selected and arranged Sorbothane should be deformed, under normal load, by about 20-25 percent. More deformation will break down the Sorbothane; less will reduce vibration mitigation. (Again, IIRC.)

Many members of this forum have described what sounds like blindly buying Sorbothane feet, without running calculations to make sure they were buying the size, shape, durometer rating, and number of feet appropriate for their rig. However, Deanimator is saavy and careful, so I'm hopeful he has done this.

Also, Sorbothane headquarters, in Ravenna, Ohio (USA) are just an hour away from Deanimator's home. I'm even closer to Sorbothane--maybe 25 minutes. Sometime back, I called Sorbothane's engineers with questions about how best to use their products to dampen my rig. They were friendly and helpful, and suggested I bring the rig in so they could help me set it up properly. While I didn't ask about price, I got the impression that they weren't looking for consulting fees--just nice guys looking to help a customer, and interested in what we're doing with these rigs of ours. So my sense was that I'd just pay for parts needed, with the advice thrown in for free. Since I've been doing fine with no dampening whatever, I haven't taken them up on their offer (I live in a forest and work in a basement--very quiet, vibrationally.)

This said, I'd like to meet the vibration engineers at Sorbothane, in hopes of learning from them. Deanimator, if you ever decide to pay them a visit, mind if I tag along?

--Chris S.

[Chris S.]

The paint at the rear of the upper side is indeed screwed up. It peeled away with the plastic down to the primer. It's a relatively small area. Any repair suggestions?

I'm no expert in painting metal (prefer powder-coating for my rigs), but have used primer and paint on other steel projects. Here are some thoughts for your specific case: If the primer in your bad spots is intact, I'd get some very fine steel wool (such as 00--AKA "double ought" steel wool), and use it to scrub off any loosely-attached paint. I'd also use it to gently challenge the primer, to make certain it is adhering well. If the primer is good, I'd repaint with a couple of thin layers of paint on top of the primer. If the primer is bad, I'd remove the primer, clean the metal, reprime, let the primer dry, reprime again as a second coat, let it dry, then add a couple thin layers of metal paint.

To remove bad primer or paint, I'd sand with emory paper, and maybe clean with acetone or a heat gun with razor scrapping (be careful using heat and acetone together--acetone is flammable until it has finished gassing off). This, in order to remove any elements of covering that don't seem sound. My sense of painting metal goes as follows: First, get it clean--really, really clean; remove rust, remove dust; remove oils and such with acetone; then remove other contaminints with alcohol. Once these have gassed off, apply primer, let dry, then apply another coat of primer. When dry, paint in one or two layers. All this said, I find that powdercoating is more robust, and often cheaper.

Does any of this make sense?

Even with the handles, it's a bear to move. I'll probably bring in from the car tomorrow morning and lean it against something so that I can get the screws and T-nuts installed so that I can slide the 80/20 on and tighten it down.

I hear you! My rig (plate plus other stuff) is about 87 pounds. It has nice handles, but it's not easy to move. But how much harder would it be without handles??

Cheers,

--Chris