DIY with Jon Garner

Tips On Working with Acrylic


Many DIY projects contain some acrylic components, knowing the right tools and techniques to use with acrylic will make DIY projects easier and more successful. One of the main problems in working with acrylic is that it does not transfer heat very well. Always keep this in mind when using tools with acrylic. Heat from a tool will put stress in the acrylic, which may cause crazing later. Remember to always wear safety glasses when cutting, routing or drilling acrylic, because small plastic chips can come flying off of the tool. It is best to begin with small projects to hone your skills before tackling major projects such as building a large tank.

Cutting Acrylic

There are several ways to cut acrylic. A water-jet cutter is one of the best ways to do it, but a water-jet cutter is too expensive for most of our budgets. If there is a large machine shop locally they may have one. For a simple DIY acrylic project at home, a table saw or radial arm saw with a blade that is designed for cutting acrylic will work fine. A Freud LU-94-10 saw blade works very well for cutting acrylic, it has a triple chip grind, 3-degree hook and .110" kerf. McFeely's* carries the Freud LU-94-10 for $69.50. A zero clearance table saw insert and a pair of blade stabilizers would also help make better cuts by reducing blade vibration. Rockler* carries zero clearance table saw inserts for $21. Woodcraft (1-800-225-1153) carries blade stabilizers for $15. Always try to feed the acrylic into the saw blade at a steady rate, feeding it too fast or too slow may case the edge to melt. Many plastic shops use a panel saw to cut acrylic. It works well for the core of their business, but may not give a cut that is accurate enough for the precision required in the construction of a sump or tank. If you decide to have a plastic shop cut your acrylic, be sure to tell them that all of the sides must be the same width and length. Acrylic of 1/8" or less thickness may be scored like glass and snapped apart. This process may not, however, leave an edge that is flat enough for capillary gluing.

Freud LU-94 sawblade
Zero clearance
Acrylic scoring knife

Drilling Acrylic

Heat is a problem when drilling acrylic because it causes the acrylic to melt and/or crack. Normal twist drills may chip and crack acrylic because of their tendency to lift and twist the acrylic rather than scraping it like a drill, which is designed for acrylic. A normal twist drill can be modified for use on acrylic with a bench grinder. Instructions for this modification can be found in the DIY section of my website. Specially ground and polished drill bits designed just for acrylic are available from U.S. Plastic* in a few sizes. When using a drill bit made for acrylic there will be a long curly strand of acrylic created during the drilling process. The drill press should be set from 500 to1000 RPM. Always start and end the hole at a slow feed rate. Once the hole is started a feed rate of around 3 1/2" per minute works well. If a number of holes are being drilled, be sure and let the bit cool off frequently so as not to overheat the acrylic. Normal hole saws can be used to make large holes in acrylic, however it is very difficult to keep them from melting the tiny acrylic chips, causing the chips to stick to the side of the hole. A hole saw should be fine if you are making a hole to be used for a bulkhead fitting. It always helps to have a piece of plywood behind the acrylic being drilled so it has some backing when the drill bit cuts through. Remember: don't drill too close to the edge of a piece of acrylic as it has a tendency to crack towards the edge. A hole should not be drilled any closer than 1.5 times the diameter of the hole measured from the center of the hole to the edge of the acrylic. Unibits are also good for drilling thin acrylic because they only have one straight flute, which does a very nice job of scraping. Enco* carries them at a respectable discount.

Holesaw
Unibits
Plastic drill

Tapping Acrylic

A tap is used to cut the threads in a hole for a bolt. Normal taps made for steel may be used to tap acrylic. Simply drill the proper size hole and tap it. The tap will have a tapered end, thread it through the acrylic until the straight part of the tap comes out the backside of the acrylic. There are taps without a taper for tapping a blind hole (one which does not go completely through the acrylic). Taps may be found at most stores that carry tools. Tap drill tables for metal are different than those used for plastic. Beside normal fractional drill bits, there are also number bits which run from 1 to 60 and letter bits that run from A to Z. These drill bit sets can be found at most online tool stores like Grizzly* if they cannot be found locally.

Tap
Drill bit set

 

Tap Drill Table

ScrewSize

Tap
Drill Size

Clearance Hole
Drill Size

# 0 80

3/64"

50

 
 
 

#1 - 64

#53

46

#1 - 72

#53

46

 
 
 

#2 - 56

#50

41

#2 - 64

#50

41

 
 
 

#3 - 48

#47

35

#3 - 56

#45

35

 
 
 

#4 - 40

#43

30

#4 - 48

#42

30

 
 
 

#5 - 40

#38

29

#5 - 44

#37

29

 
 
 

#6 - 32

#36

25

#6 - 40

#33

25

 
 
 

#8 - 32

#29

16

#8 - 36

#29

16

 
 
 

#10 - 24

#25

7

#10 - 32

#21

7

 
 
 

#12 - 24

#16

1

#12 - 28

#14

1

#12 - 32

#13

1

 
 
 

1/4" - 20

#7

H

1/4" - 28

#3

H

1/4" - 32

7/32"

H

 
 
 

5/16" - 18

F

Q

5/16" - 24

I

Q

5/16" - 32

9/32"

Q

 
 
 

3/8" - 16

5/16"

X

3/8" - 24

Q

X

3/8" - 32

11/32"

X

 
 
 

7/16" - 14

U

15/32"

7/16" - 20

25/64"

15/32"

7/16" - 28

Y

15/32"

 
 
 

1/2" - 13

27/64"

17/32"

1/2" - 20

29/64"

17/32"

1/2" - 28

15/32"

17/32"


Bending Acrylic

There are expensive systems for bending acrylic, but for low volume work a heat tape should work just fine. U.S. Plastic* carries heat tapes for bending acrylic in 24" and 48" lengths that will work on acrylic of 1/4" thick or less. To bend right angles in a piece of acrylic make a fixture to form it over. When the acrylic gets hot enough to bend, it is very soft and may bend to an undesirable angle without a form. Some people have luck using a heat gun, but it is very easy to burn the acrylic.

Heat tape
Heatgun

Finishing Acrylic Edges

How well the edge of a piece of acrylic needs to be finished depends on its intended use. If it is going to be glued, the type of glue being used and if a clear joint is desired will all affect how the edge will need to be finished. Flat edges without voids will work best for solvent cementing. Using the right saw blade to cut the acrylic will reduce the amount of edge finishing that will need to be done. Remember to not let the edge overheat in the finishing process. A router or jointer can be used to make a rough edge become flat and smooth. U.S. Plastic* carries an edge scraper, plastic plane and carbide router bits for acrylic. A variable speed router is helpful because the cutter speed can be adjusted so it shaves off thin pieces of acrylic without melting them. Experimenting with the router and some scrap acrylic will help find the appropriate bit and feed speed.

Edge scraper
Plastic plane
Router bit

Gluing Acrylic to Acrylic

There are many options when it comes to gluing acrylic. Acrylic cements come in various degrees of thickness. Water thin cements make very nice joints because they work into the joint by capillary action, but won't fill any voids. The thicker cements will fill voids, but do not flow into a joint as well as the thin cements. To make thicker cements put acrylic shavings into some thin cement until it reaches the desired thickness. This mixture should be sealed and allowed to sit for 24 hours before using. Pre-thickened cements are also available ready-made. Always remember to work in a well-ventilated area to avoid inhalation of vapors and wear gloves to avoid skin contact. Do not smoke or work around flames as some of the cements are very flammable. Always read the MSDS (Material Safety Data Sheet) for the exact cement being used before using it. Follow the exact cementing procedures of the manufacturer for the particular type of acrylic being used, because different types of acrylic have slightly different cementing procedures.

Gluing Acrylic to Glass

Oceanic uses GE Contractors Silicone SCS 1200 to glue the acrylic corner boxes into glass tanks. U.S. Plastic* sells SCS 1200 in translucent and assorted colors in caulking gun sized tubes. The key to a good bond is for both surfaces to be completely clean, as even one fingerprint will cause the Silicone not to adhere well to it, creating a poor bond. Always allow 48 hours for it to dry and another 7 days to cure completely.

Silicone sealant

Making Acrylic Flanges

An acrylic flange is common to many DIY and production designs, so it is handy to be able to make them properly. There are two types of flanges: a tube flange has the same ID as the tube it is attached to, while a cap flange has the same OD as the tube flange. The cap flange is used to make a removable cap on a tube. Two of the tube flanges can be used to attach two tubes together. One of the easiest ways to make a flange is with a router and circle-cutting attachment. Rockler* carries several different circle-cutting attachments for routers. U.S. Plastic* and Onsrud* carry straight carbide router bits for acrylic. If a hole is needed in the center of the flange for a fitting, or if this is a tube flange, first drill the pilot hole for the circle-cutting attachment, and cut the OD of the flange. The piece of acrylic should be fastened down so it does not move around while the flange is being cut. For a tube flange, set the circle-cutting attachment to the flange ID, and cut it. To make a flange cap without a hole in the center, use the circle-cutting attachment to cut a circle out of plywood with the OD of the flange. Use the foam type of double-sided tape to attach a piece of acrylic to the plywood disk. Two short strips of tape should suffice to hold the piece of acrylic to the wood pattern. Use a pattern-cutting bit and a router to make a copy of the wooden disk on the acrylic. Pattern-cutting bits are straight-sided, and come with a bearing on the top or bottom. Drilling the bolt holes to attach the two halves of the flange together should be done with care, so that the flanges will easily line up in any position. To do this, make a paper pattern of the flange, and draw another circle halfway between the OD and ID. This will be the bolt circle. Decide on the number of bolts that will be needed in the flange. Divide the bolt circle into that number of equal length sections. Make a copy of this drawing for each flange half. Cut the patterns out, tape them to the flanges and drill the holes. If one side of the flange is going to be tapped, be sure to drill the side that the bolt will pass through with the clearance hole size bit and the side that will be tapped with the tap drill size bit from the table above. U.S. Plastic* and Aquatic Eco-Systems* sell nylon bolts, nuts, washers and wing nuts. Holes that are going to be bolted should have the edges of both sides of the hole relieved with a zero flute countersink. JL Industrial* has zero flute countersinks for $6.

Tube flange
Flange cap
Circle cutting attachment
Nylon bolts
Foam tape
Pattern cutting bits

Acrylic is very easy to work with and can be used to make many useful things for your system. It is one of the most flexible and reef safe materials available to work with. Knowing how to work with it is critical. It is my hope that these tips, coupled with some practice, will help you succeed in whatever acrylic project you undertake for your marine aquarium.

* Web links for listed businesses are in the table below.


If you have any questions about this article, please visit my author forum on Reef Central.

Supplier Links and Additional Information Sites:

U.S. Plastic
Rockler
JL Industrial
Aquatic Eco-Systems
Enco
Grizzly
Onsrud
McFeely's
Cryo Industries
IPS Corp (Weld-On)
Ridout Plastics
Piedmont Plastic
San Diego Plastics



Reefkeeping Magazine™ Reef Central, LLC-Copyright © 2008

Tips On Working with Acrylic by Jon Garner - Reefkeeping.com