Kronos Robotics Review Series

Scroll Saw Review

I was working on a book project and needed to create several walker robot prototypes with several small curved parts of various shapes and sizes. I have a large band saw but it was just too difficult to cut the small curves and details needed and there was no way to make the inside cuts required for many of the pieces. Several years ago I had a small 15" scroll saw and tried to cut acrylic but just could not achieve a smooth cut. The plastic would melt and fuse back together behind the blade. Recently at a local tool show I managed to talk some of the scroll saw exhibitors into letting me cut some scrap plastic I had with me. After a few tips I was cutting expanded PVC and acrylic like a pro. I decided it was time to look into purchasing a scroll saw and visited a few local retail stores in my area. After a bit of research the following three saws represented a good mix of what was available for $400 or less. Ryobi SC164VS 16" scroll saw Dremel 1800 18" scroll saw Dewalt DW788 20" scroll saw I decided to purchase all three and give each a whirl. I also picked up several blade types so I could see which ones would work best for this project. Scroll saw blades come 12 to the pack and are rated by the number of teeth per inch. With 3 saws and 480 blades I decided to build three complete bots on each saw. This would get me past the learning curve and help me get a real feel for the saw and its capabilities Two of the bots would be made from 1/8" Baltic birch plywood, the kind you get from craft stores. This plywood has no voids and finishes up very nice. It is lighter and firmer than expanded PVC and is more heat resistant. Even if you plan to build a robot in expanded PVC or acrylic, I recommend using the Baltic birch plywood for the prototype. I also cut the parts for a walker bot out of expanded PVC. I did enough parts for 1 bot on each saw. Now lets take a look at each saw and see how they performed the task.
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Ryobi SC164VS

This was the

least expensive saw I tested. While it worked ok and I was able to build the three walker bots, I found myself constantly at odds with this saw. The removable key lock is a nice feature if you have small children running around the shop. The saw is also the lightest and the easiest to transport. Unfortunately, these are the only nice things I had to say about this saw. The blade tension is adjusted at the rear of the saw. I found this irritating as I had to reach around the saw to tension the blade. I don't like saws where the power and speed controls are located under the table. This makes them difficult to reach in an emergency shutdown. There are three problems that stand out with this particular saw. There is very little room under the table to access the blade clamps and thumb screws. This makes blade changes very difficult. The table was very rough. No amount of waxing could smooth it out. This makes turning tight corners difficult. I eventually made a top out of waxed 1/8" plywood and attached it with double sided tape. While this is not the only solution to the rough surface it worked quite well for me. The rubber knob that tightens the table tilt mechanism is very easy to break. The knob on this saw broke with only one use. There after I had to use a wrench to loosen and tighten the table. This was not much of a problem since you won't be tilting the table with most robotic projects.

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www.kronosrobotics.com
This saw represents the low-end class for scroll saws. You will find saws in this class that are very similar in size, shape and design. Many of them may have been built in the same factory. I just can't see these or other low-end saws holding up to everyday use.

Dremel 1800

Purchase Dremel 1800 Here
http://www.amazon.com/exec/obidos/redirect?link_code=ur2&tag=kronosrobotic-20&camp=1789&creative=9325&path=external-search%3Fsearch-type=ss%26index=blended%26keyword=Dremel%201800
Dremel calls this an 18" scroll station. While the included 5" disk sander is an added feature, you won't be using it much on your robotics projects. I did not use it once on the three walker bots I built using this saw. You would be better off purchasing the optional flex shaft and using one of the Dremel sanding drums. The disk is somewhat of a pain to get on and off so you will have to choose one or the other. Like the Ryobi this saw will accept both pin and plain-end blades. There is a hinged access drawer that makes changing the blades a bit easier than the Ryobi. The saw has almost twice the weight of the Ryobi and with this it vibrates much less. The table is polished cast iron and only took 4 layers of paste wax to get a silky smooth surface. For blade storage there is a small drawer under the table but I don't recommend it for serious users. Most blades are impossible to tell apart so I suggest some sort of sorting tubes for your blades. The controls are all up front on top of the saw so it's very easy to access them. One real nice feature is a small led light www.kronosrobotics.com

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located on the saw. While it won't illuminate your work surface it will keep a beam on your saw line. The saw has a flexible air tube that puts out quite a bit of air that will keep your saw line free of sawdust. However, when I cranked the RPMS up past 1000 the vibration caused the flex tube to eventually drop to the table surface. A scroll saw stand or bolting the saw to the table will probability alleviate this problem. Another area that was of concern to me was the large blade insert. It had very large blade grooves and did not sit flush with the table surface. Luckily the design was simple, and by tracing the insert on to 3mm birch plywood I was able to create an insert that I could wax and drill a very small hole for blades. This was perfect for the small pieces I cut for my walker bot projects.
The saw has small vinyl covers on the power and light switches. These are used to keep dust out of the switch mechanisms. They both eventually came off during use and I found it made using the switches much easier. The saw weighs in at over 50 lbs so you won't be toting it around the shop, but there is a handle in the top just in case you feel up to it. I liked this saw. It worked very well on wood, expanded PVC, and acrylic. Dremel also makes a 16" scroll saw with cast iron table and a 45 degree tilt both ways. It's about $80 cheaper so if you want something a bit smaller and cheaper you may want to look into that one.

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Dewalt DW788
Purchase Dewalt DW788 Here
http://www.amazon.com/exec/obidos/redirect?link_code=ur2&tag=kronosrobotic-20&camp=1789&creative=9325&path=external-search%3Fsearch-type=ss%26index=blended%26keyword=DW788
A high end scroll saw can cost you well over a $1000. Are they worth it? Well that depends upon your use of the saw. If you use it once or twice a year it may be better to purchase a smaller less expansive saw. If, on the other hand, you plan on using the saw everyday a high end saw is right for you. The Dewalt scroll saw has a $399 street price and is the closest thing to the high end saws that I could find locally. The saw is actually manufactured in Canada by the same company that manufactures the Excalibur (high end) line if scroll saws. All scroll saws vibrate; It's just a matter of how much. From the $60 saw to the most expensive $3000 saw, it's the nature of the beast. The saw's mass will affect vibration; the heavier saws don't vibrate as much as the lower weight saws. You can also lower the vibration by bolting the saw to a heavy table or stand. Design can affect vibration as well. For instance, on the Dewalt the pivot points for the arms are up front near the blade. This provides for less moving mass and yields much less vibration. Couple this with the fact that this saw weighs in at over 70 lbs, and you get a very smooth running saw. The Dewalt is the epiphany of simplicity. Things just don't get simpler. The open design under the table means you can access and change a blade in a matter of seconds. If you check out other high end saws they all seem to have this open design. The Dewalt is so open that they have actually added a small guard in front of the clamp mechanism. This is to keep you from accidentally pinching a finger while the saw is running.

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Blade clamps are in a fixed position so they are easy to tighten and loosen. This also means less blade deflection. The dust blower is sturdy and does not change position during operation. The table is cast iron and was so smooth that I only needed two coats of paste wax. The table has a small hole for the blade which is perfect for the small pieces you will be cutting. You won't have to worry about making a new insert. All controls for the saw are upfront, and with this design you can adjust the blade tension while the blade is in motion. The tension lever is also indexed so you can get the exact same blade performance each time you remove and attach a blade, which is very important for inside cuts. Of the three saws I tested, the Dewalt was the only saw with no dust collection port. This did not bother me as I had not planned on using a connected dust collector with any of the saws. Scroll saws have small blowers that keep the scroll line clear, so they tend to blow a bit of dust in the air. The simplest and most effective solution for dealing with the airborne dust is to use a small window fan with a filter taped to the front positioned nearby. This tends to capture all the airborne dust and is fairly quiet. Saw Choice Conclusions The fit and finish on all three saws was very nice. All three saws had no problems cutting the wood, plastic, and acrylic needed for my walker bots. However there was no way my boss (wife) was going to let me keep all three saws, so I had to choose only one. I decided on the Dewalt saw mainly because I see myself using the saw on just about every robot project in the future. This saw features full ball bearings and less overall maintenance than the other saws. Factor this with the ultra low vibration and my choice was made for me. Had the cost been more of a factor I would have chosen the Dremel 1800. If you decide to purchase a scroll saw here are some of the features to look for: Table finish Variable speed Plain-End blade support

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Ease of blade change Blower for clearing stock line
You will also want to pick up some sort of light. I like the inexpensive $7 clip on lights. You can add as many as you want. Use a 40 watt bulb to keep the heat down.

Techniques

Inside Cuts Making an inside cut with a scroll saw is very easy.
Step 1 Lay out your cut. In this case we are cutting a servo mount. Step 2 Drill a small hole in one of the corners just touching two of the sides. This hole should be large enough to insert the saw blade. As an option you can drill 4 holes, one in each corner. Step 3 Unclamp the blade at one end. Insert the blade through the hole then clamp the blade back in place. You can release the top or bottom of the blade, it does not matter. www.kronosrobotics.com

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Step 4 Cut the stock. Once cut unclamp the blade and remove the stock. In this case I drilled the holes with a drill press.
Shape Transitions There are times when you want a vertical piece to transition to a horizontal piece. In this case we are making a bot leg that will be connected to a servo. We could apply heat and bend the leg, but bending is not an option in many situations. For instance, with expanded PVC it would yield a leg that's just not rigid enough to support the weight of the bot. If you are using plywood, heat alone is not enough to bend the leg. In this case we cut two pieces with slots where the pieces will overlap. The slot is 1 half the length of the overlap. The width of the slot is the thickness of the stock.
Once cut, the pieces are joined together by sliding the slots into each other. This makes for a very strong and rigid leg. In most cases you won't even need to use an adhesive to hold them together. While this technique works well for both wood and expanded PVC it is a bit more difficult when using acrylic. Acrylic is a little more brittle and will break if the slots are too tight. In this case you are better off cutting the joints a bit large and laying down a bead of hot glue.
Cutting Multiple Pieces There are times you need to cut multiple pieces that are the same shape. To do this, stack several of the pieces together using thin strips of double sided tape. Carpet tape works nicely.

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If you are cutting expanded PVC or acrylic you will also want to coat the top with masking tape. Not only does the tape aid in the cutting of the stock, but it also gives you a surface to transfer your pattern.
Once the pieces are cut you can do all your sanding while they are still connected. There are some disadvantages to bulk cutting. If you make a mistake you will ruin all your pieces, not just one. Also, you will have to use a coarser blade which will yield a rougher cut. To cut the stock shown here I had to use a #4 blade verses the #1 I normally use.

Scroll Saw Blades

Scroll saw blades come with plain-end and pin-end configurations. Most high end scroll saws only use the plainPlain-end Scroll end type. There are many more types of scroll saw blades available in the Saw Blade plain-end configuration. Generally, pinend blades should be easier to change; however on the saws I tested I found this not to be true. The Ryobi and Dremel accept both types of blades but because they accept both the blade connectors are a bit more complicated.

Pin-end Scroll Saw Blade

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Once you decide on the blade end configuration there are many types of blades available in various widths and tooth patterns. These range from skip tooth to reverse tooth types. There are even spiral blades that will cut in any direction. There is a universal number system used to reference plain-end blades. Most manufacture's use it and it's a good guide when selecting the finish type and cutting radius of a scroll saw blade. The smaller the universal number, the thinner the blade and the more teeth per inch. I have found that a #1 blade works very nice in 1/8 plywood or plastic. It leaves a very fine finish and requires no clean up. You can just about turn in place to cut extremely tight corners.

Materials

The three materials I tend to work with the most when building my robots and prototypes is wood, Expanded PVC, and acrylic. On occasion I have also cut softer metals. Wood I used 1/8" Baltic birch plywood for most of the bots in this project. You can purchase 12" x 24" sheets for $4 at most craft and hobby stores. You can also cut up to 2" thick pine with ease. Hardwoods such as oak and maple will start to get more difficult as the thickness increases and you will need to use a larger blade. Expanded PVC Expanded PVC is very easy to work with. When this material is cut the edges will yield a dull course surface. While the finest blade will create an ultra smooth surface you will never get the glossy type finish as on the flat surface of the plastic. I

RYOBI 16 in. (406 mm) SCROLL SAW MODEL NO. SC164VS REPAIR SHEET
RYOBI 16 in. (406 mm) SCROLL SAW MODEL SC164VS
The model number will be found on a plate attached to the motor housing. Always mention the model number in all correspondence regarding your Scroll Saw or when ordering repair parts.

PARTS LIST

Key No. 23 Part Number S1605007 S1605004A TSC11007 TSC06001 TSC07008 S1601009F TSC11003 TSC05001 S1601004C TSC05002 S1601001 S1601006C S1601012 TSC07009 S1601010 TSC11004 S1601008 TSC11008 TSC07001 S1604005 S1604001 S1602001B2 TSC11005 Description Qty. Key No. 46 Part Number TSC07002 S1601003 TSC07010 TSC13001 S1604004 S1602001B1 TSC06002 TSC07003 S1602003 TSC11006 S16020021 TSC04001 TSC12001 S1603005B1 TSC07004 TSC11009 S1603005B2 TSC07016 S1603005B3 S1603004C S1601016A S1603003 TSC07011 Description Qty.

* * * * * *

* * * *
CIRCUIT BOARD.. 1 POWER CORD.. 1 SPRING WASHER (M6).. 8 HEX NUT (M6)... 6 SCREW (M5 X 10 mm).. 5 COVER PLATE.. 1 SPRING WASHER (M8).. 2 BOLT (M8 X 25 mm).. 2 BASE... 1 BOLT (M6 X 16 mm).. 4 HOUSING ASSEMBLY.. 1 TABLE SUPPORT... 1 SCALE INDICATOR.. 1 SCREW (M2 X 12 mm).. 1 BEVEL SCALE... 1 SPRING WASHER (M5).. 3 SPRING.. 1 WASHER (M6)... 3 SCREW (M6 X 40 mm).. 1 SPRING.. 1 BLADE TENSION ASSEMBLY.. 1 LOWER ARM.. 1 SPRING WASHER (M4).. 6
* SCREW (M4 X 10 mm).. 2 OIL BUSHING.. 4 * SCREW (M5 X 6 mm).. 1 * CARRIAGE BOLT (M6 X 25 mm). 4 RETAINER.. 2 UPPER ARM.. 1 * HEX NUT (M5)... 1 * SCREW (M5 X 20 mm).. 1 SPACER... 2 * LARGE WASHER (M6).. 1 LINK ASSEMBLY.. 1 * HEX KEY (M4)... 1 STRAIN RELIEF.. 1 BLADE ADAPTER... 2 * SCREW (M5 X 25 mm).. 1 * WASHER (M4)... 4 CLAMP JAW.. 2 * SCREW (4.2 X 10 mm).. 1 SPRING.. 2 THROAT PLATE.. 1 TABLE LOCK KNOB.. 1 BLADE... 2 * SCREW (M4 X 16 mm).. 2
WARNING: Improper repair of a double insulated tool can result in damage to the double insulation system possibly causing electrical shock or electrocution. Any repairs requiring disassembly of your tool requires safety testing and should only be performed by a Ryobi Authorized Service Center. For the service center nearest you call 1-800-525-2579. * Standard Hardware Item May Be Purchased Locally 3
Key No. Part Number S1601014 TSC11001 TSC09001 S1605006M S1605001H S1602005B S1601007 TSC07006 S1601018 S1601015 S1601020 S1601019 TSC11002 TSC07007 TSC07017 TSC07012 TSC07013 TSC07014 TSC07015 S1601017 S1601011 S16020022 S1601005 S1605005F S1605003A S1601032A Description Qty. Key No. 96 Part Number TSC07018 S1601023D S1603008 S1604011 S1603009 S1605010 TSC11010 S1605011 S1604010A S1605001H1 S1605001H2 TSC11011 S1605003A1 TSC07019 TSC14001 TSC06003 S1606007F S160600411 S1606003Z 080900063903 S1606012A S1606009 S2-14-08 (REV:01) Description Qty.
DROP FOOT.. 1 * TOOTH WASHER (M5).. 1 ROLL PIN.. 4 SWITCH PLATE.. 1 MOTOR.. 1 ECCENTRIC.. 1 SAW TABLE.. 1 * SCREW (M6 X 30 mm).. 1 PLASTIC TUBING... 1 ADJUSTMENT LEVEL.. 1 BELLOWS LOCK.. 1 BELLOWS... 1 * TOOTH WASHER (M4).. 4 * SCREW (M8 X 8 mm).. 1 * SCREW (4.2 X 8 mm).. 1 * SCREW (M5 X 8 mm).. 2 * SCREW (M4 X 6 mm).. 2 * SCREW (M5 X 35 mm).. 5 * SCREW (M5 X 30 mm).. 3 DUST BLOWER.. 1 DROP FOOT LOCK KNOB.. 1 BEARING RETAINER.. 1 BOLT RETAINER.. 2 SWITCH BOX.. 1 ON/OFF SWITCH.. 1 RUBBER FOOT.. 2

* SCREW (4.2 X 13 mm).. 4 COVER PLATE.. 1 T-HANDLE HEX KEY (3 mm). 1 BLADE CLAMP SCREW. 2 ARM BEARING COVER.. 4 POTENTIOMETER.. 1 * WASHER (M5)... 1 VARIABLE SPEED KNOB.. 1 FOAM BUSHING.. 1 CARBON BRUSH.. 2 BRUSH CAP.. 2 * LOCK WASHER (M10).. 1 SWITCH KEY.. 1 * SCREW (M5 X 10 mm).. 1 BEARING.. 2 * HEX NUT (M10).. 1 SPEED INDICATION LABEL.. 1 DATA PLATE.. 1 WARNING LABEL... 1 LOGO PLATE.. 2 BLADE WARNING LABEL.. 1 BLADE TENSIONING LABEL.. 1 GROUND LABEL.. 1 OPERATORS MANUAL
* Standard Hardware Item May Be Purchased Locally 4
RYOBI 16 in. (406 mm) SCROLL SAW - MODEL SC164VS

BLACK WHITE BLACK

SWITCH
WHITE SPEED KNOB WHITE RED RED

BLACK GREEN

CIRCUIT BOARD

POWER CORD

WIRING DIAGRAM