Home › Forums › Workshop Techniques › Cutting Aluminum Sheet/Plate
Cutting large pieces of aluminium
In issue 151 of MEW Dave Fenner talks about the difficulty he had cutting large pieces of aluminium for his metal mangle and suggested that someone might like to address the problem with an article.
I am not sure that it will stretch to a full article but here is some of my experience.
Some years ago a mate of mine bought a bank building when the Australian Banks were going through one of their “To serve you better” phases and shutting down loads of branches. The bank took out everything that wasn’t bolted down and left everything that was. Everything that was included all of the bits protective stuff that they put in, the shutters, heavy office panelling and the like. The idea according to one of the designers I spoke to later was that the staff should be in an area that was mortar proof. To that end the shutters are 10mm armour plate. The panels for the Manager’s office are 16 mm bullet resistant aluminium plate with a 6mm air gap and then another sheet of 6 mm bullet resistant aluminium.
Needles to say I am quite well endowed with 16mm and 6 mm aluminium plate as well as huge barbecues of 10mm armour plate.
I wanted to build a multi-purpose saw/router/planer bench. I had had a Triton for over twenty years and never been entirely satisfied with it. I decided on a single plate 900mm square x 16mm thick. I needed to cut it to size, square it all up and then cut a hole with a rebate in it to take a piece of 6 mm plate. This was before I had a milling machine or a lathe bigger than a Unimat SL.
I made the beast and it works like a charm. The router bolts onto a plate and drops into the hole. Similarly the 9 1/4” circular saw and the 75mm Makita planer.
This is what I found out about cutting large pieces of aluminium and the tools I tried.
1 Hacksaw
2 Jigsaw
3 Reciprocating saw
4 Circular saw
5 Band saw
6 Abrasive disk
7 Water saw
8 Router
Test method
I tried cuttibng with each tool except the router and water saw. I don’t have any aluminium router bits at present and I also do not have a water saw.
I laid a piece of 900 mm wide 16mm bullet resistant aluminium plate on a pair of saw horses and with my daughter manning the timer cut with each tool for a period of one minute. You can see the results in photo AC1 and AC2. The cuts from bottom to top are as per the list in table 2
Tool quality
There are quite a number of people who are of the opinion that you are better off to just buy a cheap tool and throw it away when it is knackered than to buy a good and considerably more expensive one and look after it. There is a fallacy.
1 Quality of finish. Cheap tools like Ozito, GMC and to a lesser extent Ryobi have poor quality bearings and windings in them and as a consequence the bits that do the cutting wether saw blade or router bit wobble about like Jayne Masfield or Sabrina. The finish is less accurate.
2 The second is a little more estoric. We all have to look after the planet and 2.5 kg of saw bits being thrown away is 2.5 kg of bits. The quality of manufacture has no bearing when the item becomes land fill. There is an opportunity cost to using oil for making junk instead of a quality item. Once we make a piece of junk we do not have those particular raw materials to make another item. Just like in the scrap box. What you use today you do not have for tomorrow
Lubricants
This test was made without lubricants or means of cooling except for the circular saw blade which had its teeth rubbed with candle wax in accordance with the manufacturers instructions.
In the past I have tried various lubricants on the jigsaw and reciprocating saw. WD 40, RP7, Penetrene, sterate/paraffin wax, Cool Tap and gear oil. I did not use kerosene (liquid paraffin) because of the spark risk from the jigsaw commutator. Although I felt better using a lubricant I can’t really say that there was a marked improvement in blade life because as I mentioned, I got through the 900mm cut with the blade still in good condition. If anything I would have to say that the addition of a lubricant tended to cause puddling of swarf around the cut rather than it being thrown off by the action of the saw. It also tends to make the swarf stay in the gullets. The gear oil was too heavy and prevented the saw from cutting.
Safety:
I have had more accidents than most people. I have had more skin, bone, muscle and artery grafts than anyone I know. I am not a safety nut. I accept responsibility for my actions and I still have enough between the ears to work out for myself when something is dangerous.
All of the machinery listed here is noisier than your average lathe or milling machine where you have lots of mass to help absorb the sound.
I urge you to wear hearing and eye protection when engaged in using the above tools. I also suggest a dust jacket with tight sleeves. If you do try the router I suggest a full face shield.
If you use the abrasive disks you will also require a breathing mask of some description because of the fine powder that results.
Hacksaw.
A new 18 tooth bimetal hacksaw blade will help you develop a massive bicep and deltoid muscle with a little extra added to the latissimus dorsi. You will be able to cut to the depth of the hacksaw frame but it will take a long time and unless you are good with the saw will probably end up with too much cleanup work due to wobbly cutting. Not recommended.<
Different makes of blade can make a difference. Starrett fairly recently introduced some new hacksaw blades that use a different system of welding to other manufacturers. I have a stack of Sandvik Bimetal blades in various tooth numbers that I purchased many years ago. The difference between the Sandvik and the Starrett is almost but not quite like the difference in cutting brass with a carbon steel blade and a standard Bimetal blade.
Starrett are welding the HSS from front to back (HSS to steel) rather than a longitudinal weld as has previously been the case. This makes for a less brittle blade and allows them to put a much more aggressive angle on the tooth resulting in significantly faster cutting. The cost of the Starrett blades is comparable with other good quality Bimetal blades.
Jigsaw
Bosch makes a very large range of blades for jigsaws. I was really surprised when I went to a local tool specialist who had just set up a 4m long display of the full range. The one that caught my eye at the time was the T127D HSS blade designed to cut up to 16mm aluminium. These blades have an almost flat tooth angle, are very sharp, have a surprisingly deep gullet and have minimal set. The small degree of set means a narrow kerf which in turn means a comparatively large radius if cutting anything other than straight. (Photo 1) The price was about $14.00 for a card of five. (Photo 2)
My old Bosch jigsaw is one of the earliest models with a pendulum cutting action. It does not have variable speed. (Photo 3) I have the pendulum set to (1) and do not force to tool.
Reciprocating saw
The reciprocating saw is a strange beast. It is designed for hacking things, for demolition work, for cutting pipes and the like. There is not a chance of being accurate with it. The construction and mode of operation of the device obscures the cutting line so you end up guesstimating where you are going. Cutting aluminium using this saw with a hacksaw blade is a waste of time, in fact just about any metal cutting with a hacksaw blade (bottom of photo 6) in this saw is a waste of time.
Bosch makes a range of blades for the reciprocating saw. Not as extensive a range as for the jigsaw but none the less rather good. Taking into account what I said about accuracy there are times when you just have to make the cut. I had a block of 200 x 100 x 100 ally that I wanted to cut in half. The jigsaw was not going to do it and neither was the sliding compound mitre saw. I didn’t have a band saw at the time so it fell to the reciprocating saw to do the job. The same shop I bought the jigsaw blades from –Total Tools- also sold reciprocating saw blades. I bought two types, the S1411DF (top in photo 6) and the S711DF (middle in photo 6). The S1411DF is a 300mm 6TPI blade designed to cut wood and aluminium sections of up to 60mm x 5mm wall. The S711DF is a 150mm x 6TPI blade which is designed to cut the above and epoxy products from 8 to 50mm. The third blade in photo 6 is a Makita P-04905 24 tooth. It is handy for stirring drinks and filling up your tool box.
Like the jigsaw blades, using a lubricant is a waste of lubricant. Although the blades where not designed for cutting sections like the one I needed to cut I gave it a go and although it was difficult to keep on or near the cutting line both blades did a passable job. The 300 mm blade is really too long for this type of work, there is too much flex in it and the far end bangs abound like a prick in a shirt sleeve. The 150mm blade was the blade of choice. When cutting with these machines it is necessary to rock the saw so that you are presenting small sections to the blade. The difference in doing that and not doing it is noticeable. Even with the depth of tooth gullet on these blades there is a high chance of clogging if you do not rock the blade. You get close to a doubling of cutting speed by rocking over straight cutting.
If you decide to make a cut like the one I did you do have to be careful with your rocking motion. Rocking up will put a lot of strain on the furthest extent of the blade. If the blade is going to break it is at this point that it will do it.
If you have to use one of these saws to do the job you certainly can but it is not the best tool in the box. I can’t recommend it.
Circular saw.
If you want to just make an occasional cut in large section aluminium then you can just use a reasonably close tooth TC tipped wood cutting circular saw blade. They are cheap enough these days that for a big job you can afford to treat one as a consumable. If you plan to do more than the odd cut then get a proper aluminium cutting blade. (photo 7)
I have a number of saws. The afore mentioned jig and reciprocating saws plus an 8 ½” sliding compound mitre saw, a 9 ¼ ” and 7 ½” hand held circular saw, a 10” table saw and a 14” band saw.
I bought the Hitachi compound saw second hand on Ebay a couple of years ago for $325.00. Given the condition of the saw I think I got a bargain. The bloke who sold it to me had used it for cutting aluminium window frames and so when he passed it on to me it came with an excellent Koyo aluminium cutting blade. These are a fairly expensive blade, about $120.00 new. Record-Irwin blades are about half that price. There is about half the metal in them over something like the Koyo. This particular blade is an 80 tooth. The teeth have a negative hook
on them so they tend to slice rather than chisel at the material. The proper lubricant to use with these blades is a sterate/paraffin wax. It is available from larger hardware stores and tradies tool suppliers in cardboard wrapped stick form. Although it looks like candle wax it is a different formulation. I am told that they are not interchangeable though when I did this test I used a $2.00 garden candle and it cut without a problem. The wax is applied to the blade before cutting and prevents aluminium chips from sticking to the face of the tooth. Incidentally, a dab of wax on a linisher belt helps minimise clogging when sanding Aluminium.
For cutting sheet aluminium you can buy a Record-Irwin blade in just about any blade size to suit the most common hand held circular saws. As with all operations in this article you really do have to use correct safety gear. I am not being a nanny about this. You have to use hearing protection because a circular saw cutting aluminium howls like a banshee and will knock the top 5 kHz off your hearing double quick. You also MUST wear eye protection because the saw will spit out little bits of aluminium all over the place. Getting aluminium out of your eye is more difficult than steel swarf because it is not magnetic.
For sheet work use a hand held circular saw or a table saw. For cut off work try using a mitre saw with the work clamped. In both cases the finish is superior to any of the other methods here.
If you want to get the job done today then use a circular saw. If you want a contemplative monastic experience then use the 24 tooth blade in the reciprocating saw.
Use feel to determine the best feed rate. Better a little slow than too fast.
Band saw
I really like using a wood workers bandsaw for aluminium. It is fast and fairly accurate. I use the bandsaw for rough slitting of clamps and the like then finish off with a slitting saw because it is just so much quicker. Almost any profile roughing work is performed faster on a bandsaw. The blades are nothing special, just a standard spring steel bandsaw blade. The normal three teeth rule applies as it does to the jig and reciprocating saws. At least three teeth have to be in contact with the material to avoid blade damage or damage to the work.
Given the three tooth rule, the thinner the material the greater the number of teeth required. For thick material I use a ten tooth blade and for general cutting a fifteen. The blade speed is about 300 SMPM or 1000 SFPM. Cutting speed is generally less than you think. It is important to let the saw do the work and take a light cut. If you press to hard you will end up a number of problems
• Uneven tension. The bottom of the blade will be under greater tension than the top allowing the top to flex and make the cut deviate.
• Clogging of the gullets will cause the blade to jam and possibly break the blade or polish the rubber of the tyres which means less grip on the blade requiring greater tension which leads to
• Blade breakage.
Use no lubricant or you will make a mess of the tyres. Photo 8 shows a fifteen tooth 1/8” blade that will cut a minimum radius of about 3/8” in aluminium. It will cut a tighter radius but you start generating a lot of heat in the blade which just does it no good.
When using a wood workers band saw for aluminium it is very important to ensure that you have it set up correctly. The blade must be tensioned fairly tight. The blade must be tracking accurately on the wheels. The guide blocks or bearings must be adjusted correctly and the top guide must be as close as possible to the work.
The very best book available on setting up a band saw is Mark Duginski’s Band Saw Handbook.
Abrasive disk
Dave mentions trying a metal cut off wheel and finding that it clogged rather than cut. Pferd, Flexovit and several other manufacturers make aluminium abrasive cut off wheels in the normal sizes. They are of a special non loading construction. They are used in the same way as steel cut off wheels. For occasional use I think they are excellent. They have a longer life than their steel cutting counterparts.
(photo 9 – courtesy Pferd. http://www.pferduse.com) As mentioned in the safety section, use a face mask to avoid breathing in the aluminium powder.
Water saw
If you are getting serious and need a lot of complex, thick parts cut then water saw is the way to go. A water saw squirts a thin jet of water at 50,000-60,000 PSI out of a nozzle at your work. The work is fairly relaxed about this gives up the struggle. Garnet dust can be injected into the stream to make the stream more abrasive. Water saws can cut pretty much anything from sponge cake to 125mm thick granite to hardened (63 HRC) steel. Although there are versions that allow for freehand cutting the ones you are most likely to come across are CNC. Google for your nearest operator.
Router
If you have a 1500 watt or greater router you can use that for cutting large chunks of aluminium. A number of manufacturers make solid carbide spiral router cutters. Two patterns are available, a spiral up cut and a spiral down cut. The up cut tends to pull the router down on to the work and the down cut tend to push it away. The up cut relies on having a very good quality accurate undistorted chuck so that the cutter does not pull out. The up cut deposits chips on top of the work. This is important if you are making a blind plunge cut. Having the swarf deposited on top of the material means that unless you have effective dust extraction you run the risk of trapping swarf under the router sole plate with the concomitant tendency to damage the surface.
Down cut deposits swarf behind and below the material. This is okay if your cut has an open end or if you have completely penetrated the material.
A 1500 watt router running at full speed – about 20,000 RPMs will allow you to take ½” wide cuts about ½” deep. A CNC router will take a deeper cut but it is better braced than you will be. My experience is that you can take a ½” x ½ “ cut if the router is firmly pressed against a well clamped straight edge but only for as long as you are properly balanced. If you have to reach past your safe balance point the router will take off and wreck the job and maybe you too.
The actual cutting depth and feed rate is dependent on the cutter so check with the manufacturer.
Be very careful NOT TO CLIMB MILL. It will take off on you and wreck everything, quite possibly including you in the carnage. An out of control router is like the Tasmanian Devil in Bugs Bunny cartoons.
If you are not familiar with routers then I suggest you do not use one for this work. They can be really dangerous.
You can also get solid carbide burrs that are designed for aluminium. Generally they are ¼” shank. Fitted to a die grinder they are sensational for free hand sculpting and rapid metal removal in aluminium. Be very careful.
Material to cut: 16mm aluminium plate of no particular grade
Method Speed Noise Effectiveness* Cost
Hacksaw Dead slow Low Poor Cheap
Jigsaw Slow Moderate Reasonable Cheap if you have a good jigsaw to hand
Reciprocating saw Moderately fast Moderate Just does the job Don’t buy one just for this sort of work.
Circular saw Excitingly fast Awful Very Cheap if you already have one.
Band saw Fast Moderate Very Expensive but an excellent investment
Abrasive disk Fast – depends on size and wattage Loud Moderate Cheap
Water saw Moderately fast Low Excellent National Deficit
Router Moderate Loud Moderate – needs a guide Moderate
*Effectiveness is whether you can cut complex shapes and the ease with which the job is done
This table lists the cutting implement used, the quality of finish obtained, a photo of the finish and the distance cut over 1 minute.
All cuts timed over one minute in 16mm bullet resistant aluminium
Tool Quality of finish mm/min cut
1 S711CF 6 tooth Photo 6 top, Reciprocating saw RAG* Very rough, need milling to clean up Photo ac1 38mm
2 S1411DF 6 tooth Photo 6 middle,, Reciprocating saw As above Photo ac2 49mm
3 P-04905 24 tooth photo 6 bottom,, Reciprocating saw Rough. Milling would be best but a number 1 bastard file or 14 grit AlO will get there Photo ac3 12mm
4 Flexovit FH38 A36S-BF41 ALU 230 mm in 9” angle grinder Good. If the cut is accurate clean up with 120 grit to reasonable finish Photo ac4 144mm
5 Flexovit FH38 A36S-BF41 ALU 100 mm in 4” angle grinder As above Photo ac5 68mm
6 Koyo Aluminium blade 80 tooth in 9 ½” saw Best finish. If some swirl marks do not offend then you can leave as cut. Photo ac6 900mm in 55 seconds
7 15 tooth Bandsaw blade Good finish. Straight vertical lines will need 80 then 120 grit Photo ac7 untimed
8 Starrett Bi-metal 18 tooth hand hacksaw RAG. Needs milling Photo ac8 35mm
9 Jig Saw A little rougher than the band saw but not much Photo ac9 38mm
*RAG Rough As Guts
Conclusion
My suggestion is to estimate what other use you can get from the various tools listed here. As metal workers you probably already have angle grinders so for occasional use buying cut off wheels makes sense. This article is about thick section material and although the 100mm grinder did work it is really underpowered and too small for the job. The 230mm wheels cost just twice as much as the 100mm but cut twice as fast and because of their diameter will cut much further.
If you like trepanning and need another hole in your head then I suggest you get a reciprocating saw. I bought the reciprocating saw convinced that I needed it, that it would attract the ladies and that I would never need Viagra. What a fool I was. I haven’t yet found a job at which it excels at or is even enjoyable to use. It is slow to prune trees. Uncomfortable to use at almost any angle, inaccurate, noisy and a waste of cupboard space. But I won’t sell it.
The jigsaw is fine if you do wood work. Don’t buy one unless you need to do lots of cutout work.
Sliding compound mitre saw. Excellent saw to have if you need to dock and mitre wood. For the type of work the average MEW reader does it is not really the best option. A metal cutting band saw is of more use.
Circular saw. If you don’t have any of the other tools then to my mind the most frequently needed is a circular saw. As it is the fastest, most accurate and give the best finish of all I would just buy a decent 8 ½” saw and an aluminium blade. Why 8 ½” over a 9 1/4” ? a 9 ¼” saw blade is a beast. It is heavy and difficult to manage. A 7 ½” is the nicest size that cuts the majority of timber that most people need but when it comes to cutting aluminium or steel an 8 ½” just has a little more guts that makes the job easier.
(he used to be a sales manager at Freud but I didn’t know about these blades then
)Edited By Sid Herbage on 23/07/2010 21:49:52
Home › Forums › Workshop Techniques › Topics
Started by: SteveP
in: I/C Engines
JasonB
Started by: Alan Ambrose
in: Manual machine tools
Bill Phinn
Started by: COLIN MARTIN 2
in: Materials
fredjscipione
Started by: Bill Dawes
in: General Questions
Bill Phinn
Started by:
David George 1
in: CAD – Technical drawing & design
Mark Rand
Started by: Buffer
in: General Questions
Phil P
Started by: Chris Crew
in: The Tea Room
Chris Crew
Started by: Dougie Swan
in: General Questions
Ian P
Started by: James A
in: Manual machine tools
Andy Stopford
Started by: Andrew Tinsley
in: Workshop Tools and Tooling
Clive Foster
Started by:
dee
in: Related Hobbies including Vehicle Restoration
duncan webster 1
Started by: Harry Broadbent
in: Model Engineer & Workshop
vintagengineer
Started by: Bill Dawes
in: General Questions
Dalboy
Started by:
Michael Gilligan
in: Clocks and Scientific Instruments
Kiwi Bloke
Started by: Tony Ray
in: Workshop Tools and Tooling
bernard towers
Started by: lucerne
in: Manual machine tools
bernard towers
Started by:
dean clarke 2
in: I/C Engines
dean clarke 2
Started by: jimalm
in: Electronics in the Workshop
Vic
Started by:
duncan webster 1
in: Electronics in the Workshop
duncan webster 1
Started by:
Neil Wyatt
in: Manual machine tools
Howard Lewis
Started by:
JasonB
in: The Tea Room
jaCK Hobson
Started by: Roger Harvey
in: Workshop Tools and Tooling
ega
Started by: Andrew Tinsley
in: Workshop Tools and Tooling
Andrew Tinsley
Started by: Dalboy
in: General Questions
Graham Meek
Started by: Peter Simpson 3
in: Beginners questions
Peter Simpson 3


