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That is an awesome idea. We could only do two sides though because the pan is rectangular and only fits in one long side or the other.

He's gonna stick with the depth stop strip in our case. Perhaps if someone else builds one they can capitalize on this idea better than us. He was originally thinking about a disk under the bit but had difficulty with how to keep it in place and he saw the infinitely adjustable depth strip as a more viable solution.


He said he never thought about the gluing 4 of them down on 4 sides thing. He said if he would have thought of that he might have went with a square steam pan and done just that.

A square pan in a rig like this would pull that trick off nicely though.

Hubby is going to scribe a grid of positioning lines set at measured intervals into the pan bottom, which he can line the edge of the depth strip up with to make setting the depth strip easy. He will just use the depth strip as his straight edge to scribe the lines. He will make some pretty deep scribe lines then go ahead and
cover the lines with black magic marker, the wipe the excess off lightly/carefully with acetone leaving nice black alignment lines in the bright stainless bottom.

Another change/improvement in design involves the motor mounting plate where hubby has decided to make the lower holes for the locking bolts on the pivot section into slots instead of through holes. The slot will extend from the current hole to the edge of the plate so the mount can be pivoted up without fully removing the locking screws, but rather by simply loosening them. Explained in image below:

The motor mounting plate, having not previously mentioned anywhere is made of 16 gauge steel (1/16"thick.)
Tomorrow's project: Make the depth stop strip. Hopefully out of stainless.

Hubby went and fabbed up the motor mounting plate as far as he could except the holes to mount it to the risers and the motor stud and shaft holes. First he measured and laid it out using a black sharpie and a six inch steel scale.


He went out to the pole barn with his angle grinder and cutting wheel and 3 Lb. sledge and came back in fifteen minutes later with this:


Below: It's a perfect fit on the motor risers. Not too shabby for a guy with a sledge, angle grinder and a bench vise. (He has a metal brake but it's buried in a bunch of our son in law's stuff out in the pole barn.)

He is going to drill motor mounting plate to riser holes next. 

Hubby's layout for the motor mounting plate he has to fab and bend.






Hole placement will be determined when we get the motor.

Well, I said he might go out and powder coat it and he did.
Here it is before re-assembly

Re assembled:

With the pan installed side/rear view. Look at the reflection of the table and mouse cord. It's gloss black.

From the front

The powder coating came out pretty good and makes the frame look way nicer. It contrasts nicely with the stainless steel water pan.

Now, all we have to do is wait about two weeks to buy this:

That is hilarious

The build progresses a little more. In the photo below he shows all four feet on the frame.


Next shot shows the spacer plates he installed so he wouldn't need to notch the pan for the motor risers.


Last shot shows how the motor risers will be attached. They are held on by c-clamps for the photo. When done they will be held on by 1/4-20 socket head cap screws.


The only thing left he can do until we get the motor is actually drill and tap the riser bolt holes and screw them together. The risers were made extra long so if too much is there when we get the motor, they will simply be shortened then. Unfortunately, the mounting stud measurements aren't on the motor order page so hubby is going to wait until it comes to fabricate the actual motor mounting plate.

You might want to keep those pillow blocks greased up. They are exposed to the grit in the oil. I hate to criticize because it is a fantastic build, but those pillow blocks probably should have been mounted outside the tub. There would have been more drop in the clamp also. Looks like you could have gotten another couple inches if the bearing wasn't under the clamp.

At the very least you should put a cover over them. The less dirt that has the possibility of contaminating the bearing grease the better. Covers are a good alternative to a complete re-design. Other than that, awesome saw.

Like most things in life, there is a really simple workaround solution for the dilemma of water and mills. The answer is: Put the stone in a plastic container filled with water.......Wow....who would have thought of that.  Clamp the entire assembly down. 
I'm not going to waste my time explaining this anymore so just go to this link and read all about it (the page is written in three steps (pages) and the answer is not on the first step.) BTW, the author of this article actually uses a CNC milling router and not a bridgeport. I think you could swing this simple slot on a bridgeport though. A good machinist (like my hubby) would have no issues at all.


Since I have never personally used a milling machine to put a slot on a rock, I could only guess how they cooled the bit without wasting the table and ways. Well, that is why there is google. I googled "milling in rock" and voila, just like that I had the answer to the coolant question. Google is your friend. 

I did know, before I opened my mouth to answer juddlerguys question however, that milling machines are being used for stuff like that.

OH yeah, the bits used are like sintered diamond tool steel rods, much like the bottom picture that i posted. With something like a milling machine in your arsenal, you would be stupid to try and do it any other way.

They also make (really costly) purpose built CNC stone routers,

where the stone is clamped down to a table and the milling/routing head moves instead of the table. It is on fancy machines like these that the fancy diamond bits with built in coolant holes are used.

The one pictured above looks like it might use flat linear motors for all the x and z axis moves (also known as Mag Drives.) Please, don't ask me to explain what that is....(although I could because hubby used to install them almost everyday.) That might also be a simple rack driven x/z axis but he can't really tell from the photo. He says the small steel rail next to the main linear bearing rail looks like what might be a rack and the one up top on the moving bridge also looks like a gear drive rack.

These are basically the same kind of machines that my hubby used to design and build for a company called Glassline Corp. but the ones he made were used for cutting/edging glass, not rocks (working with glass requires tools with machining done to extremely small tolerances, capable of working with one of the more brittle and shatter prone substances that are worked this way.)

Go one step beyond the simple CNC mill/router and you have the multiple axis stone cutting mill/router. It can carve statues and busts for crying out loud.


I don't think the Petoskey slot was done on one of those. That would be overkill for a simple 3" long slot. But it could have been.
Oh, and the coolant on this machine??? Looks like simple H2O. Probably not. The water presents a rust issue inside the mill and the stuff being used is most likely filtered and recirculated.

Based on all the facts, I would say that the most likely way that slot was put in that Petoskey was with a regular mill with a diamond bit with the rock submerged in a tank of water. I chose the regular mill based on the fact that Petoskey stones are not a mass manufactured kind of thing. It was likely done as a one off or maybe he does them more than that. Petoskeys don't come made to order so the chances of having enough stones of that size to make a bunch of them are slim to few.
Probably a product likely made by a lone lapidary probably somewhere in Michigan using a re-purposed vertical mill using diamond bits with the rock in a tank is the most plausible answer.

How could it plausibly be done with no mill? Once again, first submerge the piece in a plastic tub filled with water  Very carefully drill a series of adjacent holes to the exact same depth as close together as possible. Break or saw the space between the holes. Use large diamond drill bits or a diamond oscillating  blade and smooth down the ridges in the hole until it looks like a smooth slot (which would take a long time I think.)

A mill would be way easier.

A Bridgeport mill could probably do that. (with the right end mill bit)

Hubby made holes in steel that way. They're called slots. The piece is clamped to a moving table that moves under a massive drill. The drill uses special bits called end mills. The bits are held in the mill by something called collets.

Wouldn't be too hard to do on that Petoskey with one of those.

I imagine they used a diamond bit. Probably something similar to this:


Or one of these. Advertised as a diamond end mill bit:

If it can mill granite, Petoskey is a piece of cake.
You can buy a nice used Bridgeport mill for probably anywhere from around $3,500 to $5,000. They only weigh about 1500 lbs.