Gallery, Projects and General > How do I??
Quartz Surface Plate?
krv3000:
if you intend to bond the glass to a suitable top just use builders adhesive comes in a variety of cullers and is made for the job
sparky961:
So, among the other things that life has required of me lately I've spent about 4 hours working on flattening one piece of counter top that I obtained. Considering that when I started I was seeing a 0.010" swing in some places on the indicator, lots of progress has been made. It's been going well enough that I've switched from the 0.001" indicator to the 0.0001" indicator to better discriminate the deviation. I'm down to about 0.0015" max, with lots of large areas not moving the needle more than 0.0005".
Two words: Silicon Carbide. That's all you need to know. :) Maybe diamonds would cut faster, probably in fact. But I don't have diamonds. I did have an old green Silicon Carbide grinding wheel that was too small to mount but otherwise in good shape. I thought "what the heck, I'll see what it does". I used the side of the wheel to take down the high spots prior to lapping, not to mention leaving the abrasive grit between the two plates for faster cutting action. I've been going back and forth between the stone and another piece of countertop. I have three on the go now, and I'm using one of the larger pieces to span a greater distance across the largest one. I had noticed some dishing after the first session, which I hope to rectify with the larger piece.
I'd be very pleased if I could get this locally flat to within +/- 0.0002 or so using this method. I may start running into problems with deflection around that point though because that's about how much it deflects under it's own weight when you pick up an edge.
There's been lots of talk about bonding various things to others in this thread. What about making a stack of granite with epoxy between? I guess even something like builder's adhesive should be fine. Differential expansion shouldn't be an issue because it's all granite. The little bit of epoxy shouldn't affect that. Rigidity will be increased significantly.
There are some pretty distinct stages one can observe:
1. Smooth - Two pieces begin rough and offer little resistance to sliding over each other
2. Grabby (very scientific, I know) - When using a liquid with grit, this happens when you're starting to get pretty flat. There's strong suction that causes the plate to move with greater force or stop completely over irregularities. It seems to indicate that you're gotten rid of most really high spots and are starting to get flat.
3. Slick - The big piece of rock you're sliding around begins to feel almost like it's floating. It will just about spin on it's own.
My advice if anyone wants to try this is to have patience and perseverance. It's not the most exciting thing to do but it does seem to be working.
Manxmodder:
Looking good,Sparky. I'm watching this effort with interest as I do have a few decent sized pieces of this granite counter top lying around looking to be used for something......OZ.
hanermo:
I went through this exercise, to align my scratch built VMCs linear rails, 2200 mm long.
I found a vertex ground CI straightedge, about 150€, new in the UK. Accurate to 0.04 mm.
A better option is a granite long parallel, but they are about 600 for 1.4 m long iirc.
Still thinking about it.
Machine builders square spirit levels, == 0.02 mm/ metre, were about 70£. I got two, and they make aligning stuff quite easy.
Testing the straightedge on a real granite surface plate, 600x440 mm, proves that you can easily see errors of about 0.01 mm, with a light behind it.
Putting a cig paper as a shim on either end, shows the lift clearly.
Since you dont need perfect, testing from the center to the edges should get you close.
Its feasible to sand steel pretty flat, ime.
I used a big, heavy, large belt sander.
Marking with a spirit permanent marker pen and sanding it off, shows you can get decent control on maybe 0.02 mm depth or so.
The edges get rounded.
The rails are mounted, and very well aligned, except at one spot. Its either high, low, twisted, or wanders from the front rail in some direction.
Plan is to put a dti on the ram, and check for rail error in the 3 axes.
Then just use a screw-jack to push it straight, and then tighten the mounting bolts.
You can easily feel any error over 0.01 mm while pushing the ram back and forth. Asain, cig paper as shims proves this quite easily..
The blocks are strong, and wont come to any harm from hand-forces.
I used 35 mm linear rails and blocks.
Hope this helps.
BTW - Pics of the machines will only come once they are polished, for commercial reasons.
Machine is commercial quality, with commercial components, and costs, and I need to clean them up before pics.
Hope to get them polished inside a month.. but this is not a reliable estimate.
sparky961:
I've had the chance to spend a few more hours rubbing two stones together and I'm surprised to say that I wasn't really bored throughout the process. It's rather relaxing and very rhythmic; albeit very messy as well. It's to the point where I have one fairly large slab pretty much floating around on top of the other with little resistance. Actually, a few times it just about got away on me and slipped off the other side onto the floor! These pieces aren't light! It's a bit strange to spin one atop the other with almost no resistance. Hours of fun, in fact.
Now, the two issues I'm struggling with are as follows:
1. Flatness doesn't seem to be improving beyond around 0.001" max deviation over about 6". Lots of places sit closer to a few tenths plus or minus but not as many as I'd like to see.
2. How to translate indicator readings into "map" of surface, most importantly the high spots. The way I see it, a + or - reading could mean a small surface variation at the indicator tip, a large variation at the tip, or that the base is sitting on/in a variation that's causing the tip to erroneously read high or low.
How do you sort all of this out?
Is it possible without the fancy gadgets and software that professionals use?
Would 3-point contact of the height gauge base be of more benefit than the flat base that can rock a bit on imperfections?
Is this where it becomes easier to use a level?
For #1, I'm thinking it could be just that I haven't done enough work on it yet. But what I don't want is to keep working and not see any improvement. Hence #2, I want to be able to ensure its getting better, not worse or just shifting the variations around.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version