Drilling and turning petrified wood

[TNC]

Greetings everyone! I have a unique project and could really use some expert advice. First, I'm a woodworker who really enjoys making pens. How that connects to this forum is that I'm researching ways to use petrified wood as the material for a pen. So far I'm golden on how to cut the stock pieces, but where I'm still lacking in certainty is drilling and turning.

What I've found is that a diamond coated sintered core bit is the best way to go for drilling, with good water flow for cooling and evacuation. Does anyone have any other ideas/recommendations for that?

Secondly, for the actual turning process. I know a steel chisel is almost guaranteed not going to cut it (sorry, bad pun). I have carbide tipped chisels, but again I'm uncertain if that would destroy the cutting edge or possibly shatter the stone. Would it be best to use diamond grit files and simply shave down the stock piece, "wet sand" as it were?

Any and all advice is both welcome and appreciated. Thanks for reading!

 

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[kcm]

I've never done anything like that, but I think your use of using the diamond drill bits would be your best bet. If you could afford to or if you have some spare material to test with, you could try using solid carbide bits (or maybe burrs, if not to large diameter) to make an initial hole quickly. Could then go back and clean it up with diamond.

I think a lot is also going to depend on the petrified wood - density, hardness (just what minerals have impregnated it), cracks/fractures, etc.

In what order do you intend to do the drilling; before roughing the outside or after? It would keep the blank stronger to drill out the inside first - at least with a rough hole.

I like your idea - very original. If it works for petrified wood, then the same process "should" work for other rock types. Please let us know how it turns out.

 

[TNC]

The basic process for making a pen starts with (1) cutting a "blank" into a roughly square rod of appropriate size. (2) Next is drilling the appropriate sized hole down the length followed by gluing in the brass tubes. (3) Third step is putting it on the lathe for turning and then applying the finish, which is just going to be polishing in this case.

Speaking of the polish, I have some microfiber pads ranging from 1500 to 12000 grit, and I have my doubts about how well those would work. I could get some diamond paste, but that's also adding more cost. If I can make this work, we are talking about one expensive pen!

 

[kcm]

Yes, am familiar with the process using wood blanks - though have never done it myself. Never did use a lathe for my woodworking - only for some metal working long, long ago.

I'd say the diamond paste would be the way to go. Just remember, a little goes a long way! Using too much is only wasting money. On the other hand, you could also use fine grits of tungsten carbide. Look up rock tumbling supplies - polishing media. You'll probably find the best prices there.

...Maybe I shouldn't even be posting right now. This is the LAST post at the end of a very long day! My last remaining brain cell is mush! So please, forgive my horrid rambling tonight.

....Once you have the hole drilled and you start to turn the outside, I'd probably go with a small angle grinder with a diamond blade. The blades are quite inexpensive. Don't know what kind of lathe you have or if it's possible to use coolant, but I'd probably just use the dry-grind blades and a good respirator, rough to shape, then finish up with increasingly fine grits of carbide grit followed by very fine diamond paste.


With that, I have to call it quits tonight. It's taking longer to correct my mistakes than when it does to not make them in the first place.

 

[hvacker]

Need to remember petrified wood is no longer wood, it's silica. Forming the pen with a cab machine wouldn't be hard but I'm sure how to drill the hole.
In a lathe start a diamond bit small and gradually going larger. I say start small because a larger bit would have too much torque and I would think it would break the work.
Diamond bits I have are very short. I hope the bit doesn't take a quick exit out the side.

Come to think about this my diamond bits are only diamond on the cutting end.
Maybe a core bit like ones used to cut holes in concrete. I've used 6" & 8" but maybe there are smaller ones made.

 

[TNC]

Not sure what you mean by "cab machine". As for diamond tipped bits, have you seen any of normal length? Depending on the pen kit, I would need to drill over 5 inches deep. The average is about 2.5 inches. Also, minimum diameter is 7mm, and some kits go up to 9/16" and 37/64", which are going to be quite large for petrified wood.

So far I'm still researching and haven't bought any specialized tools for this. I have a company that specializes in this and will custom make any size drill bit for a base of $140 and up. I'm not sure there's any other viable solution at this point.

 

[kcm]

...Have you considered looking into ultra-high pressure waterjet cutters? Ones for making small parts like pens shouldn't cost an overly large amount, I wouldn't think. The prices of these machines is coming down all the time. Not sure if one would go through far enough for your needs, or do it without deflecting and blasting out the side of the blank.

 

[TNC]

Hmmm, I really don't know much about this realm of tooling. Mostly just what I've researched for this project so far. Sadly I would anticipate that style of tool would not create a high precision and concise hole all the way through. There is very little room for slop.

Since you recommend diamond paste for the polishing, do you have any advice on how to use it? I never have before, just my microfiber pads and other typical sand papers. Now for the tumbling grits, I like that idea also as those are DRASTICALLY less expensive and far more abundant. I looked up Moh's hardness scale and the tungsten carbide is just under diamonds at 9, petrified wood and most other semi-precious fall in the 6.5-7ish range.

As for other stones, I hadn't thought of that but very much like the idea of a tiger's eye pen and such. I could make a small fortune with this if it works out well.

Sadly, it won't happen any time soon. I've got lots of other things going and this will require quite a bit of new setup to construct. But I am a bit excited for it.

 

[kcm]

For polishing your pieces, chuck into a lathe. Take varying grits of polishing paste and multiple strips of medium to heavy felt. Can color-coordinate the felt for different grits, but I would simply use white felt and a sharpie to mark the grit on each end. While the piece is spinning in the lathe, place small amount of grit on center of a felt strip, then use as if you're using a strip of sandpaper. Keep a little water on hand to keep the felt slightly moist if needed, but ONLY if needed. Don't worry when the cloth turns black - that means it's doing its job. Just keep using, and use the paste sparingly.

Just as with sandpaper, go from coarse to progressively finer grits.

For some other thoughts about lapidary polishing, check out this site:
Lapidary Polishing Compounds » Juxtamorph » United Artworks

This guy says he doesn't care much for diamond polishing, so this should provide some alternatives to think about.

As for the waterjet, it might be worth contacting someone with a waterjet cutting machine and asking them if this could possibly work. Might even could send in a blank and let them try, as they are already experienced. Normally, even waterjet cutters have to use abrasive media when working with stone - so that might be a whole other issue as well. Is just a thought.

If you ever make one, you'll have to post it for us to see!

 

[stdenis_jd]

Talk to the guys/ladies here:
Lapidaryforum.net - Index

I just got into lapidary and they have been an amazing resource. Endless amounts of knowledge there.

I personally can't think of a good way to drill a hole long enough to make a pen, so you may have to resort to "sectioning" but that's my rookie opinion.

 

[Eu_citzen]

I have most of the equipment required..

For polish:
Cerium oxide on felt, just give the felt a spray of water, will polish it nicely. You need to cool the stone and prevent dust from forming.

Use grits as follows: 80, 220, 600, 1200, 3000 (optional) and then polish.

I prefer ultrasonic drills for long pieces to be drilled.. They have a "needle" which vibrates, if you add either diamond or siliconcarbide and water, it should work nicely!

But mind you; its going to be expensive any way. Working stone takes way longer then wood. And in stone, 7 inches is a LONG way.

 

[hvacker]

A cheaper way is a core bit but I don't know if it would work. I like a core bit as they are sturdy and probably won't go sideways.
Check out Rio Grande
https://www.riogrande.com/category/tools-and-equipment/burs-and-drills


I checked out EU's suggestion of an ultrasonic drill and it does sound like the best way but $$$

 

[kcm]

I had NO IDEA they made diamond coring bits that small!!

Ok, that's what you want.

 

[Kwillie]

I have some petrified wood I brought back from Saudi Arabia. Worked with US Army OPM SANG.

 

[TNC]

Certainly some things here I never knew about. So far these guys are the best affordable option I've found:
Diamond Core Drills, Universal Application - Call (661) 257-2288

They will custom make any size bit I need, and their own water swivel attachment would allow me to just push right through without damaging anything (assuming I don't use hulk strength). I estimate roughly around $350 for their setup, maybe more depending on what they charge for the core bit.

Good information on the polishing techniques. Same practice as using a wax/friction polish on wood.

Now, another idea I've been working on for the actual "turning" process I'd like to bounce off you guys. In my searches, I saw a stone lathe for large building sized stone columns that used a cutting wheel which very, very slowly crept sideways using the large flat surface of the disc to grind off the stone while the lathe rotated, also at a very slow rate of maybe 60rpm. What I can do is build a mount/carraige assembly for my dremel and use diamond coated discs to replicate that on a very small scale. Still working out how to set up the water cooling system safely. The lowest RPMs I can manage is 600 on the lathe and 5000 for the dremel, so that's a LOT of spray I don't want...

 

[kcm]

Chuck your dremel bit (diamond disc or bit) into a drill for lower RPM's. I don't know if I'd rough it using a disc or using a nickel-bond diamond bit. ...Guess you could even use the face of a diamond hone!

That huge lathe you saw probably turned a lot of marble and alabaster, I would think. With larger diameters, they had to use lower RPM's. But using the grit of a diamond, you will be able to turn at a much greater speed than they did.

Try to make a setup to where you can have a recirculating water supply continuously pumped over the piece while being turned to provide cooling, while at the same time shielding or somehow preventing the water from splashing to any motors, etc.

...How do you intend to mount the blank on a lathe or spindle once the hole is drilled? What shape will your hole be, straight? Will there be any inner contour? Also, it might be possible to knock down the corners of the blank using a belt sander with a diamond-impregnated belt, then put in your lathe setup for final shaping. Guess a lot depends on whether you're looking to make one at a time or go into production.

 

[TNC]

Yes, that big lathe I saw was turning an 8 foot post or similar, and at least 10 inches diameter.

The drilling is a straight cylindrical hole through the length of the piece, then a brass tube is glued inside. After that, it's either put on a special mandrel for the lathe, or directly on the centers using special bushings for sizing. That's why I'm leaning toward the core bits, which would leave me with a stone cylinder that on a larger pen kit could become a blank for one of the small kits, increasing the yield of the stock.

Thinking in a different direction, since the lathe itself is capable of good speeds, I could simply buy diamond hones/sharpeners and mount one of those on a carriage to move it sideways in a very slow progression. My lathe can go up to 3600 RPM so I really don't think the dremel's speed would be any kind of help, and possibly a hindrance by over-speeding the grinding surface. Also its much easier to build a mount for a simple panel vs. the dremel.

 

[kcm]

How well can your lathe and its parts handle water?

...Instead of diamond hones, which can be somewhat spendy, you might consider using diamond angle grinder discs. Of course, I haven't priced them lately, either.

 

[TNC]

The first thing about the water is putting down plastic/vinyl sheeting to cover the lathe. I'm not the tiniest bit interested in rust. Might even go so far as to craft some solid wooden shielding for a couple parts, with rubber bushings at key points.

I'll look at fish tank gear for the pumps and such to circulate the water, that won't cost very much. Probably end up building my own "enclosure" out of plexiglass and silicone RTV. Same would go for the drilling.

As for the diamond hones, those are fairly inexpensive. I live in Japan where quality knives are quite common place as well as sharpening them at home. I can go get very affordable diamond tools at the local hardware store, or from Amazon.co.jp.

 

[kcm]

Just make sure to post us a pic when the time comes.