You mill drill guys....

[torker]

I've been asked many times to show the 3" post I cemented into the column on this mill...and to show the jacking bolt setup I use to aid in tramming this thing. The bolts also add stability to the lower base. Without them the base can actually flex. This whole affair ties it all together. It's ugly.. I did it in a hurry and grabbed whatever fit at the time. The big bolt in the bottom of the shaft goes right through and jacks against the base toward the front. You can figure the rest out I guess. Some of the stuff is welded on afterwards...way inside. More bracing to steady things.
Add this to the "Million Ways to Improve A Mill Drill" deal that everyone hates

Russ

[BobWarfield]

Good stuff torker!

I am engaged in filling my mill's base and column with epoxy granite to dampen vibration and increase its dynamic strength. At least that's my story, and I'm sticking to it!

The fill material is a mixture of granite gravel, sand, and epoxy. It molds real nicely:



Filling the base was very straightforward:





What you see there is all dry and solid as a rock. It increased the weight of the base from about 100 lbs to nearly 200 lbs. I will be partially filling the column as well as increasing the strength of the connection between column and base with a monster big bolt to add to the existing bolts.

The nice thing about the epoxy is it bonds well to the cast iron, it adds no moisture so does not promote corrosion, and it is pretty neutral in terms of changing size as it sets up.

I like your jacking screw arrangement for tramming your column.

Lastly, I am adding a one shot oiling system I'm fabricating.

You can do quite a lot to improve these machines.

Best,

BW

[Doc Nickel]

That's an interesting idea. It had been suggested to me many years ago to fill the column of my JET mill-drill with concrete, to help stiffen it and damp vibration, but as noted, I was concerned with moisture and corrosion.

The column of my mill is cast iron, thinner walled that I'd have expected (especially given the weight of the head) and extremely rough inside.

I eventually made a heavy table with supports on either side of the regular column, and that did help some, but I have been gathering ideas to optimize it more so it's more useful.

Is this epoxy granite a commercial item, or does one just mix fancy fishtank gravel with some JB weld and call it good.

Doc.

[Doc Nickel]

Here's a photo of the stand:



It's all heavywall pipe and plate, fully welded. The perforated legs are "gun casing"- oil well casing that's dropped down the well full of a seies of small shaped explosive charges. The charges perforate the casing, crack the rock, and allow greater oil production.

But I digress.

I put a lot of miles on this poor mill before I picked up the Bridgy clone- you can see the "shadow" on the wall, notably behind the leftmost upright just above the table, of the "spray" from cutting oils, chips and other swarf.

The one thing I didn't do, though, is build in any option to tram the mill- I'd assumed that the fixed column couldn't be trammed, so I fitted the upper bracket as closely as I could and called it good.

Doc.

[KiloBravo]

That's an interesting idea.
Is this epoxy granite a commercial item, or does one just mix fancy fishtank gravel with some JB weld and call it good.

Doc.

You can read all about it on his website/blog

http://www.cnccookbook.com/CCMillEpoxyFill.htm

[Pete H]

Very cool, and some tips for working with epoxy that I'd never come across elsewhere - like using a little torch for popping bubbles.

One point - I've had epoxy "cook off" on me - get hot enough to smoke, when it was in large volumes. Could that be a problem in the column? Or is the volume of epoxy low enough that it doesn't really get very hot?

WEST makes a "high-temperature" hardener for use in the Summer (that is, it's slower than the regular hardener), and that would slow the reaction down.

Thanks for a very good, and easily-followed, description.

[BobWarfield]

I've had epoxy "kick" and get real hot too, but have not seen that for this project. It could be the West epoxy I'm using, or it could be that I mix it up in relatively small batches added one after the other, but I have hardly felt it getting warm to the touch, let alone hot.

FWIW, there is a cheaper epoxy supplier than West Marine that is mentioned on the original CNCZone E/G thread. I don't have the link handy, but you can find it. My West epoxy cost about the same because I got some "scratch and dent".

As to how precise it all has to be. There are thousands of posts over on CNCZone about minute details. Those guys were ordering precision aggregates in 5 sizes, "Zeospheres", wetting compounds, deairing compounds, lamp black, you name it. It's not clear to me that they were getting dramatically better results from all that, and I wanted to get on with a project using locally available materials.

Filling existing castings is a much less demanding task than casting up entire machines from this stuff, which is what the CNCZone guys were after. I think this simplified approach will work very well for filling castings. Since I am lucky enough to have 2 identical mills, I intend to try to cook up some tests of some kind to quantify how much this has helped. Any ideas would be appreciated.

Meanwhile, DocNickel, I like your column brace and as mentioned I really like Torker's jacking arrangement too.

One thought if you were to fill a column entirely. You may want some kind of vibrating arrangement to help the air out of the mixture inside the column. Some of the CNCZone guys were using concrete vibrators from Harbor Freight for the purpose.

Cheers,

BW

[lazlo]

You can read all about it on his website/blog

http://www.cnccookbook.com/CCMillEpoxyFill.htm

I'm surprised that Bob's Blog never mentions that a great deal of the hard work on the CNCzone epoxy granite thread, including the optimal aggregate forumula that Bob quotes, the sources for the aggregates and the West Epoxy, came from Cameron ("ckelloug") -- an active member here.

Cameron's "optimal" formula, which Bob quotes on his blog, was derived by some heavy-duty mathematical analysis of the de Larrard Packing Models and then computer simulation of the classic 3D packing problem: how to fill the greatest percentage of the 3D volume with the smallest spacing between the aggregate components.

The reason the packing density is important (and the reason the commerical epoxy granite mixtures are trade secrets) is that the tighter you pack the aggregate, the higher the dynamic strength of the resulting pour.

Cameron's optimal mix achieves someone on the order of 93% packing, which is amazing:

20% Agsco #6 Aluminum Oxide
20% Agsco #4 Quartz
20% Agsco #2 Quartz
20% Agsco #2/0 Quartz
20% 3M #800 Zeeospheres

...and here's what Cameron's formula looks like when you pour it. That entire block is epoxy granite:

http://www.cnczone.com/forums/attach...1&d=1186248447


Cameron wrote a paper on the analysis and derivation of the formula here:

http://www.cnczone.com/forums/attach...9&d=1203602933

He posted a general synopsis of the problem and his solution here:

http://www.cnczone.com/forums/showpo...postcount=1824

Great job Cameron!!!

[speedsport]

why not just fill it with lead?, prolly cheaper.

[lazlo]

Lead would work exceptionally well to damp vibration Speedsport, but it wouldn't do anything to improve the dynamic stiffness.