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                                                         (some basic information on air scribe and stylus selection)


PaleoTools has designed and manufactured 8 tools- the Mighty-Jack, the Super-Jack, and the Micro-Jacks 1-6. We also do an "extreme makeover" on the Aro tools and call it the "PaleoAro" and the Chicago Pneumatic type tool and call it the "ME-9100". PaleoTools has been involved with engraving tools for 28 years now and the following information is based on the experiences of working with each tool.


The PaleoTools Mighty Jack


This tool is designed to work on large blocks of matrix containing fairly large bones. We have used it on a 1500 lb. (680 Kg) block containing a vertebral column from an Allosaurus and worked right up to the vertebra and ribs.  It works like a very large airscribe in the sense that you have to let the tool do the work. If you bear down hard on it, it just stalls out. It runs at about 8,000 to 10,000 CPM. It seems to work best in the 100 to 120 PSIG (6.9 to 8.3 BAR) range and it takes somewhere around a 5 Horse Power compressor to keep it going. If your air pressure gets down to 80 PSIG (5.5 BAR), shut the tool off and let the compressor pump up again as the Mighty Jack gets very wimpy at this and lower pressures. Using the Mighty Jack with two hands, it is very controllable and we have worked within 1/8" (3mm) of the bone or fossil. 

The important point about the Mighty Jack is that it doesn’t have "rock shattering" power.

It comes with a solid tungsten carbide stylus that is ¼" in diameter and protrudes from the bushing about 3". We have found in testing, that either a two sided chisel or a four sided pyramidal shaped stylus worked best, the flat chisel on softer matrix and the four sided on harder. The stylus is locked in the tool so it cannot rotate. The Mighty Jack comes with an eight foot long flexible rubber hose. This tool has enough air consumption that it can be worth putting an "air tool oiler" in the line feeding it. We recommend about six drops of oil per hour put in the end of the air hose if oiling by hand.

There is the option of a handle which can be slipped on or off the tool in a matter of seconds. The handle can make guiding the tool simpler.The Mighty Jack needs to be lubricated as it has reciprocating parts in it. I use 6 drops of a good air tool oil in the end of the air hose every three or four hours of operation.


The PaleoTools Super Jack


The Super Jack was developed to fill the gap between the ME-9100 type of tools and the Mighty Jack. At some point, preparators that use the ME-9100 begin asking for more power. The Super Jack was designed with a piston having twice the area of a ME-9100 thus giving it twice the power of a ME-9100. It operates well between the pressures of 100 PSI and 120 PSI.

There are two styluses available for the Super Jack, a flat chisel and a four sided pyramidal pointed one. The chisel is best if you are just planing down a large block of matrix that isn’t too hard. When you get into really hard matrix, there are several other shapes of styli which work better and don’t have a tendency to break the point. Special grinds are available at no extra charge. Some preparators prefer the four sided pointed stylus as they can get in closer to the fossil and not take off too much matrix at once.

The tool is quite controllable. It’s like using a large airscribe rather than a Jackhammer. I walked into a prep lab one day and found a young lady using the Super Jack one handed, so that attests to its controllability. We also manufacture a quick slip on handle for the Super Jack. The Super Jack has a throttling type air valve built into it. You can control the speed of the tool from 0 to wide open. Most folks run it full open as they are trying to get the most work from it.

We also have adapted an on/off ball valve for the Super Jack which is simpler than the throttling valve type. If you have the throttling type and wish to switch to the ball valve, we can make that change for you.


PaleoTools Micro Jack 1


This was the last Micro Jack developed after a number of years of working with preparators on what was needed. The #1 is the smallest and most delicate of all the Micro Jacks. It has a number of features to make it more accurate and capable of doing some fantastic prep. To begin with, the stylus is only .046 inches (1.16mm). The stylus is locked in so it can't rotate. This means that even if the tip of the stylus is ground off center, it will still strike in the same spot each time.The tool was detuned and we know it will run down to 80 PSI with no trouble. One of our customers is running down in the 40 PSI range.

The tool normally comes in a stubby configuration which makes the whole tool, stylus included, about 4 inches long. We normally supply it with a 1/8" diameter hose and with the shut off valve at the air inlet end of the hose. This makes the tool the smallest, lightest and most maneuverable of all the Micro Jacks.

Now, having said all that, we can offer this tool set up in a number of configurations. The on/off valve can be mounted on the tool iteself if this is more convenient for you, but it increases both the length and weight. This tool is also available in a full length model, which makes it look like a Micro Jack 2. If you have large hands, the longer tool might be more suitable for you. We also offer 2" long styli for the Micro Jack 1.


Paleo Tools Micro Jack 2-6 


There are many of you that work on small delicate fossils, from small insectivores to micro-vertebrates and other tiny fossils. Most of this type work has been done using pin vises and needles. Now, I have an alternative to offer you. Paleo Tools has developed six air scribes that begin one step smaller than the Aro and go down five sizes. We have named these small air scribes the "Micro Jack" series. They are the Micro Jack 6, Micro Jack 5, Micro Jack 4, Micro Jack 3 and the Micro Jack 2 in descending order of power. These air scribes all use a 1/16" (.063") diameter tungsten carbide stylus ground to a fine point. They operate at 40,000 cycles per minute except for the Micro Jack 2 which is above 55,000 CPM.

So, now you have the opportunity to match an air scribe to the job you have at hand. Please keep in mind when using them that if the amount of matrix you have to remove is overpowering the abilities of that Micro Jack, then you need to go to a larger air scribe or Micro Jack. Once you have worked the heavy matrix off, go back to a smaller and smaller air scribe to do the detail work. These air scribes are mostly intended for use under a microscope although the Micro Jack 6, 5, and 4 can be used with the unaided eye. The Micro Jack 3 and 2 are best for use under a microscope for doing the very finest work. The Micro Jack 3 through 6 all chip the matrix away. The Micro Jack 2 turns anything the stylus touches to dust. However, keep in mind that it is removing very small amounts of matrix. But with a steady hand and with the EXTREMELY sharp stylus, you can work the toe bones of a mouse. It is an unbelievable tool if you're working on that delicate of fossils.

In order to make them as light and easy to use as possible, the handle is manufactured from aircraft grade aluminum, and then hard anodized to make it durable. The front end that holds the stylus is steel and is heat treated. An air filter is also supplied with the assembly, as the orifice in the Micro Jack is either .016" or .020" in diameter and a tiny piece of lint or dirt would easily plug it.

Are you unsure which Micro Jack to order for your needs? My suggestion if you can only purchase one, is to start with the larger sizes and then work down. If you purchase one that is too small, you may not be able to use it to your advantage on your prep job. But if you purchase one and it is too big for your current project, you will always have future projects come through your prep lab where it can be used.

Air Pressure requirements.(VERY IMPORTANT!!) 100 PSI minimum! They work best up at the higher pressures. The preparators that did testing for me, report that they work best at higher pressure. Some times they are reluctant to start and run when the pressure is below about 100 PSI. My suggestion is to purchase a small one or one and a half horsepower compressor that will run at 100 psi MINIMUM PRESSURE to operate the Micro Jacks on. The Micro Jack consumes less than one CFM of air so a small compressor that can be plugged into a wall outlet is sufficient. 

Just as a note to show the power of the Micro Jacks, with the size 4 , 3, and 2 you can write your name on your finger nail with no fear of puncturing through. That is something you would never try with a CP or even an Aro with a sharp stylus! I also have customers that are using the Micro Jack 3 and 2 for doing "Scrimshaw" on ivory as they can etch their pictures much easier with this tool than by hand.

Here's something new we have learned about the Micro Jack 5 & 6 and I've seen it on one #4. If you try to rush and push the tool past it's capabilities, it will "buck" or jump in your hand. What is happening, is that the stylus stalls as it's pushed back against the "O" ring in the stylus drive plate. Then the air pressure builds up to a point where the stylus is forced forward and this is that bucking or jumping that you might experience. If this happens, back off and let the Micro Jack do the work.  If you don't ease up, is that it will break the drive plate off of the stylus.


THE ME-9100


There are several tools on the market that are all copies of each other.  The original tool was produced by Chicago Pneumatic and was known as a “CP 9361” air scribe.  “Air Scribe” is the trademark of Chicago Pneumatic.  Some years ago Chicago Pneumatic left the U.S. and the last genuine CP that was sent to me had a “made in Czechoslovakia” sticker on it.  This type of tool is generally known in the industry as an “Air Scribe” no matter what tool it is.  PaleoTools uses an American made exact copy of the CP 9361.  All parts are interchangeable which is handy when it comes to making repairs and retro fitting parts.  PaleoTools purchases the ME-9100 in pieces.  Some parts are modified and the tool is assembled with our patented bushing and styli.  Some of the modifications increase the power of the tool and others are for reliability.  
The ME-9100 is available in six configurations and even more choices of styli.  The ME-9100 comes with either a short bushing and 1 ½” or 2" point stylus or engraving stylus. A long bushing and 3” point stylus or long bushing and 4” point stylus.  It can be had with a short chisel bushing and 2” chisel or long chisel bushing and 3” chisel stylus.  The stylus can be swapped for a 1 ½” engraving style which is called the “fish stylus” by the Green River Fish guys or the Mineral guys use it for work on really hard rock like Quartz.  It can also be had in a 2” length.  And, we have made styli as long as six inches for some special project.
The ME 9100 runs at about 15,000 CPM.  It consumes about 2.5 Cubic Feet of Air per minute.  Since it has reciprocating parts, it does need some lubricant.  Give it one or two drops of oil per hour, put into the end of the tool air hose.  Use an oil like “air tool oil” or 3in1 oil or Marvel Oil.  Do not use anything that you would put in an engine.
A note about bushings.  The chisel bushing and regular bushing for sharp tipped styli do not interchange.  The chisel styli must be locked in so it cannot rotate as the tool is running.  You need to be able to guide the chisel and if it is rolling up on its side, it is about worthless.  So, it is captured in the bushing and you guide it where and how you need it.  The sharp tipped stylus can rotate and it doesn’t make any difference.  The chisel is really great for gross matrix removal.  It will remove two to three times more matrix than a sharp tipped stylus.  But, you cannot do any kind of detail work with the chisel.  If you need both types of styli, the most practical way is to purchase a second front end with the appropriate bushing and then just screw one front end off and screw the other one on.  It takes about sixty seconds to make the switch.  You cannot just swap bushings as the bushing is pressed in and after being removed a couple of times, will no longer stay in the front end piece.



We offer four different lengths of styluses and two lengths of bushings for each of the different air scribes. The bushing is the end piece that the stylus fits through and supports the stylus.

  • The short bushing (1") is normally used with the two shortest styluses, although I have had customers use the longest stylus with the short bushing. This is not recommended, but sometimes it may be all that will work for you.

  • The longer 2" bushing is used for the two longer (3" and 4") styluses.

  • The shortest (1 ½") stylus is designed for close work. It protrudes about ½" from the bushing and can be re-sharpened a number of times. It isn’t the best stylus if you have a lot of matrix to remove, as the angle you use it at (in relation to the fossil) is pretty steep. For close work though, it has the best control being the shortest.

  • The 2" stylus is much better for matrix removal. You can get a much shallower angle and it will peel the matrix off much quicker. It can be used in moderately deep holes etc. and works well for all around prep work.

  • The 3" and 4" long styluses are for use in cranial cavities, working out the neural canals of large vertebra and sometimes for even getting between bones to remove the matrix so they can be separated. These long styluses are surprisingly strong and do not easily break, however, if pushed down into a hole and pulled sideways, they will snap (of course).





The Aro runs at about 30,000 CPM. Unlike the CP and IR, the Aro has no pistons, etc. in it. On the end of the stylus is a "stylus drive plate" that is cup shaped. An "O" ring fits inside the cup and a spring pushes the stylus drive plate back against the body of the Air scriber where the air inlet hole is. When air is turned on, the "O" ring in the stylus drive plate acts as a seal and the stylus drive plate is pushed forward until the air is released when the "O" ring seal is broken. The stylus return spring pushes the stylus drive plate back creating the seal again and the air pushes the stylus drive plate and stylus forward again. So it becomes a balancing act of the diameter of the cup of the stylus drive plate, the strength of the stylus return spring and the amount of air pressure and volume of air going through the tool. Because of the reciprocating back and forth movement of the stylus drive plate over the “O” ring, the only part of the “O” ring that receives any wear is the outer surface where the “cup” of the stylus drive plate rubs on it.  The “O” ring will wear a flat on this surface and as it does that, the tool will begin to stall and be difficult to start.  As a matter of course, if an ARO type tool is not running properly, I change the “O” ring in the stylus drive plate.  Ninety Nine out of a hundred times, this will correct the problem.  Often times people will look at the “O” ring and think it is good, but take my word for it, change the “O” ring to a new one and see if that doesn’t correct the running problem.  If you need to tap the tool to get it started, I usually tap the side of the tool against the work bench rather than bump the stylus like you do on a ME 9100. This makes for a very simple engraving tool. Instructions given with the tool say to turn the air on full to get the tool going and then begin closing the valve just to the point where it is running the way you wish it.

The Aro type of tools are capable of doing relatively fine work. They won’t remove near the amount of matrix that a CP or IR will, but the Aro transfers very little energy into the fossil, so work on some pretty delicate fossils can be done. Recommended air pressure from the factory is 90 PSIG (6.2 BAR) and air consumption is shown to be 2 CFM.

Even though the Aro doesn’t have a reciprocating piston, a little lubrication helps keep the stylus and the "O" ring in the stylus drive plate lubricated. Three or four drops of oil in the end of the air hose should be sufficient for each 8 hours of operation.

Paleo-Aro Tool

We are making an up-graded version of the All Air Products model 8315-B Aro type tool. We call it our "Paleo Aro". We have had numerous complaints about the stock tool having the hose come apart and the front end unscrewing itself from the tool while using it, etc, etc. So...... I now take the 8315-B when received and completely disassemble it. I only keep three pieces of the tool. The body, front end (minus the bushing) and the air valve. I throw away the 5 ft. air hose that comes with it and install an 8 ft. long American made hose. The hose is a 1/4" 200 PSI nylon type hose. It comes with the quick disconnect type fittings so if anything happens to the hose, YOU can now just slip the old hose out and either shorten it and then plug it back in or purchase a new piece of hose and plug it in. I install an air filter which not only keeps dirt from getting into the tool, but it gives something to grip when trying to couple the hose into a quick disconnect and I supply a standard male quick disconnect coupling. Next I machine an "O" ring groove in the body of the tool right where the front end seats against it. Now when I screw the front end back on, the front end seats over the "O" ring. This is a friction fit and keeps the front end from unscrewing off of the tool. You don't have to tighten is any more than finger tight and it will stay there. I hate seeing air scribes that have obviously had pliers use on them to tighten and then loosen the front end. For those of you who would like this "O" ring up-grade, send me you Aro and for $10.00 plus shipping I'll be happy to machine it. The old bushing is pressed out from the front end and our bushing installed. All new bushings beginning about the middle of 2003 will come so you can use either the non-rotating chisel stylus or the standard 2" long PaleoTools stylus. The new stylus the tool comes with protrudes from the end of the bushing about 1/2". When we get through, you have a good tool designed for fossil preparation and not engraving. If you purchase one of these tools, you'll be happier and you won't have need to complain to me which will make me happier too.


As with the CP and IR, Paleo Tools manufactures two bushing assemblies and four different lengths of styluses. Selection of the length of stylus is dependent upon your needs.

  • The original stylus is .078" (2mm) in diameter. By going to the longer lengths of stylus, I increased the diameter to .093" (2.38mm) to increase the column strength of the stylus. This means that the Paleo Tools stylus will not work in the stock factory bushing as it is about .016" too small.


Note: Everyone from Aro to Suhner to Dayton to the Taiwanese are making copies of the original Aro. In measuring them, I found that the internal dimensions where the bushing fits in the front end are all a little different. A bushing that was perfect for one tool either wouldn’t go into another or would fall into the hole in the front end. I finally decided that the best solution would be to provide the front end with our bushing installed. This front end will screw onto ANY of the Aro and the Aro knock-off tools and work satisfactorily. So this is why Paleo Tools sells the front end with the bushing as an assembly.

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