[nateman_doo]

I never advocated it's use; just mentioning that if I DID have to use wood, that's what I'd use. We don't always get to use what's ideal, though we use what's available or what we know of.

Heck, steel moves, epoxy granite moves, cast iron moves... Polycarbonate absorbs moisture, but it doesn't stop us from using it for shields and enclosure windows.

As to the AC boardwalk, it did have 100 year old ipe. Superstorm Sandy took care of that. Many of the boards were found over a quarter mile away, in ironically newly built housing.

i almost dont even recognize seaside anymore. Was at the sawmill this past summer. The shore is a shadow of its former self.

[petruscad]

Moving on with the infamous and controversial wood base!

Here are the pieces being fitted to the mill base to see if everything lines up.
Attachment 273730

And here is the box structure completely glued and the casters installed on each foot.
Attachment 273732

This is a closeup of the anatomy of a foot. The plate is glued and screwed to the foot (note that this also effectively seals the end of the leg!). The casters are simply screwed through the plate and into the leg itself.
Attachment 273734

Each caster is rated for 110lb so I have 440lb per foot. When fully loaded it may not be very easy to roll the whole mill around at will, but that's not the purpose. The purpose is only to be able to move the mill from the middle of the garage where it will be assembled to against one of the walls where its final place will be (~10 feet) without the use of a forklift or any other contraption of that sort.

[nateman_doo]

how much were the castors? They look very "mcmaster-ish". I like them.

[petruscad]

how much were the castors? They look very "mcmaster-ish". I like them.

Harbor Freight, $1 or $2 each. They have different sizes too.

[RCaffin]

Hi petrus

I have (bigger) hard rubber wheel casters on my wood base, but my 'concrete' floor is close to 100 years old and not what you would call 'flat' any more. Not real good concrete either. Oh well.

I was concerned that the hard rubber wheels might deform over the years, so once I got it into position I jacked it up with a crowbar and slipped wide wood blocks under the timber frame at the corners. Now the wheels are free. And I shimmed each block so the top was pretty level and very stable. Works for me.

Cheers
Roger

[nateman_doo]

Hi petrus

I have (bigger) hard rubber wheel casters on my wood base, but my 'concrete' floor is close to 100 years old and not what you would call 'flat' any more. Not real good concrete either. Oh well.

I was concerned that the hard rubber wheels might deform over the years, so once I got it into position I jacked it up with a crowbar and slipped wide wood blocks under the timber frame at the corners. Now the wheels are free. And I shimmed each block so the top was pretty level and very stable. Works for me.

Cheers
Roger

I was going to suggest that to him, and anchor it to the floor.

[RCaffin]

> anchor it to the floor.

Ah well, there must be 500 kg there, trolley plus CNC. Gravity seems to do a fine job of anchoring it down for me. And the wood is not very slippery.

Cheers
Rogr

[petruscad]

Now the fitting of the stand to the mill base.

These are the three beams glued up being fitted to the bottom of the base.
Attachment 274036

And then I placed the frame on top of them and lined everything up. The mating surfaces for every foot were shimmed and then epoxied in place to fill in all remaining gaps.
Attachment 274038

And here is the finished base. You can see the metal pads on which the feet of the mill base will rest. The pads are screwed to the beams with a plywood plate in between to spread the load a little. The few shiny spots is the epoxy that was placed between the feet and the plywood plates.
Attachment 274040

I will not paint the wood yet. I will leave it for a while, until it completely dries and most of the dimensional changes take place. Then I will add shims under the beams as needed and paint the wood.

I will now need a crane to lift the base on the stand, hopefully over the weekend!

[mcphill]

Any further progress on this build? Very interested in your progress and updates...

[petruscad]

Not much progress other than the base being lifted and placed on the stand. The lifting was done with a friend's engine crane.

Here it is strapped to the beam of the crane.
Attachment 276034

And here it is being slowly pushed into place. The crane's does not reach far enough so it cannot simply be lowered onto the base, some pushing was needed.
Attachment 276036

Done!. Sitting on six contact points!
Attachment 276038

Now the grinding flat can begin followed buy drilling, tapping and mounting the rails.

[mcphill]

What method do you plan to use to grind it flat, keepin the two surfaces planar? Please keep posting, we are all watching with great interest!

[petruscad]

What method do you plan to use to grind it flat, keepin the two surfaces planar? Please keep posting, we are all watching with great interest!

There are several techniques:

1. Standard surface plate method. Use a flat surface large enough to cover one side of the base. Cover the surface plate with Prussian blue, rub in on the base and then grind off the spots where it touches.
2. Fixed surface plate method. Support the surface plate on 3 points in the middle of the base. Move a surface gage on it with a dial indicator touching the base and progressively grind the high spots until the required precision is obtained.

Its important to realize that not the whole surface needs to ground to the same level of precision. Only the area where the rails will mount to needs to be ground to extreme straightness and planarity.

I will probably use both methods. I have a large surface edge, not as large as needed but large enough, which I can use. I also have a variety of smaller straight edges, machinist blocks, parallels, gage blocks, etc. I have the needed surface gages with thousands and ten-thousands indicators.

For grinding I will use a 6" coarse diamond coated lapidary disk as well as smaller diamond plates, disks etc, to do rough, global grinding as well as local, fine grinding.

[RCaffin]

Cover the surface plate with Prussian blue, rub in on the base and then grind off the spots where it touches.

Um ... that does sound as though it could take a lot of prussian blue and a lot of time?

Will you bed the rails on epoxy as well?

Cheers
Roger

[gary_808]

When we calibrate our big inspection granite tables at work, we use a a lapping plate and lapping paste. 3x2 meter tables flat to with in 2-3 microns.

[petruscad]

When we calibrate our big inspection granite tables at work, we use a a lapping plate and lapping paste. 3x2 meter tables flat to with in 2-3 microns.

Well, I wish I had such a granite table and the equipment necessary to measure its flatness.

[petruscad]

Here are some of the tools I plan to use for grinding the epoxy granite. First, I need something that cuts hard stone - diamond. The first is a 6" 80 grit lapidary disk mounted to a flat aluminum disk; it can be used for coarse grinds. The plates are coarse and fine grit diamond coated, used for knife sharpening. Then there are a variety of diamond disks of various grits. You can see that some of them were already used; the milky dust on them is what ground EG looks like. It is extremely fine.

Attachment 277452

Then I need some straight edges to use as references. These are pretty small. The metal paralleles are 17" x 3/4" x 3/4" and can be used for rough checks of local flatness. The white one is a ceramic edge that is 12" x 1" x 2"; small but very precise.

Attachment 277454

This is a larger and much heavier steel straight edge that's 18" x 3" x 1.5". It's solid steel which makes it very rigid, just what you need for a reference.

Attachment 277456

And this is the real thing! This is a 31" x 5" x 3" hollow, man-made ceramic straight edge. This is the straightness and planarity "reference" I will use for all surfaces and rails.

Attachment 277458

I also have a small 18" x 12" surface plate that will be useful for some things. A larger one would be much better but I'll have to do with this one...

Attachment 277460

And then I'll need some indicators and surface gages to check the progress of the grinding process. The middle gage has a thousands indicators with a 1" disk contact point for "coarse" measurements. The left one has a ten-thousands indicator and a much smaller contact point for fine measurement. The right one is for.. some other type if measurement!

Attachment 277462

I'll start the grinding soon and see how it works out.

[Voyager77]

Hi Petrus

Good to see you're keeping at it. Looks like you got the right gear to get the job done! Still asking myself though why you didn't cast in flat & pre-drilled metal bars as base for the linear guides?
By the way, I did like your design with a wider saddle and smaller table on top, thanks for explaining that.

When you grind the epoxy, please wear a mask and gloves; epoxy dust is toxic and can cause severe allergic reactions.

Cheers
Frank

[petruscad]

Still asking myself though why you didn't cast in flat & pre-drilled metal bars as base for the linear guides?

Steel inserts as long as the rails are very hard to work with. I would need to have access to some horizontal mill or something like that to machine them after casting. Or, hand scraping. But let me ask you, did you ever scrape steel? I did, its horribly hard. It takes hours of work to remove a couple of thousands over a 10x10cm area. Cast iron would be easier to scrape but then its hard to find cast iron bars like that.

When you grind the epoxy, please wear a mask and gloves; epoxy dust is toxic and can cause severe allergic reactions.

I don't seem to get any reaction from it... Anyway, most grinding needs to be done wet (with water) to cool down the diamonds; so you get a slurry and not dust.

[RCaffin]

Interesting how shaving a few fractions of a millimetre off a surface gets progressively more and more expensive as the amounts get smaller. The 'law' seems to be that going from 0.1 mm to 0.01 mm costs 10 times as much, and so on.

Optical flats are often made three at a time. These can be flat to a fraction of a wavelength: better than 0.1 micron. By grinding A against B, then B against C, then C against A, the only stable endpoint is FLAT. However, I guess that is not much use here :-)

Please do keep us up to date.

Cheers
Roger

[CaptainVee]

When you grind the epoxy, please wear a mask and gloves; epoxy dust is toxic and can cause severe allergic reactions.

As far as I know the individual components of epoxy are toxic to some extent and can indeed cause allergic reactions that can build up over time.
Always wear gloves when handling and mixing and clean spills from your hands using vinegar.

But the cured end result is (again, as far as I know) quite safe, as long as when they are mixed in the correct proportions!!!
If you can point to information that shows the opposite, I'd love to read it.