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brunneng
03-07-2003, 06:57 PM
I read several times about cutting aluminum sheet/plate on the tablesaw with a carbide blade. Now, is this a good idea? Is it safe?

At the speeds a table saw runs, swinging a 10" carbide tipped saw blade. If this is done then what's the safe way to do it.
What the thickest plate you would cut, how many teeth on the blade, any particular brand of blade?
I'm thinking kickback would be nasty.

Kevin

KACHINKOO
03-07-2003, 07:51 PM
Brunneng, I do it all the time. Just finished two custom radar masts with all the fixens for lights, horns, antenna's and tangs. 4 inch sched.40 alum pipe, .25 alum. plate with a small bit of .5 plate as well. The carpenters go nuts when they see me do it until they realise I have my own blade on the saw.Most of the time I use a 7.25 in. Dewalt thin kerf finnish carbide blade altho most any carbide blade will work.I also have a 12 in.dewalt blade for heaver stuff but rarely use it. You don't need any wd-40 or the like as long as your saw is dialed in and you take it slow.Kick-back has never been a problem with me but I always wear gloves,complete face shield, long sleve shirt and safty glasses. I saw a carbide tooth embed itself in a workers hand once from a skill saw so I never take a chance.Make damn sure the saw guards are in place!!!! Good luck Dave

Dave Opincarne
03-07-2003, 08:24 PM
Kevin - Is this a good idea? Well not compared to pulling out the plasma cutter or press shear but if you don't have one then...well yes it's doable. As a mater of fact it's pretty common in a lot of trades. I've seen table saws dedicated to this purpose for sale at Boeing Surplus and at other tooling and pattern shops. I have done this operation myself on occasion. It is realativly safe with proper precautions but it is realativly more dangerous (and less presise than other operations in the wood or metal shop because you're dealing with higher cutting forces on a workpiece that is not clamped down. It can be a mess because of the chips so be prepared for a lot of clean up. A lot of heat coupled with fine chips can lead to an aluminum fire so be careful the chips aren't forming into a concentrated pile. Also make sure the area is clear of wood dust, clean the cabinet out compleatly and disconect the dust collection if so equiped. As long as the heat's not building up there's no great risk of fire but take precautions. The blade should be a moderatly high pitch (60 teeth for a 10") with modereate rake. A triple chip blade seems to work well but a combo blade is fine. The blade should be sharp to reduce heat and HP requirements but don't use a blade you're planning on doing precision cuts with again. A blade with an anti-kickback tooth design is a good idea since it will limit overfeading the material and damaging a tooth. Inspect the blade first to make sure there are no chiped teeth, If one's going to fly off the higher loads are going to make it fly off now. Kickback can be reduced by raising the blade higher than normal so that cutting forces or directed more into the table than back twords the operator. Be sure the gaurd and splitter are in place with more blade exposed. The higher blade will also reduce the number of teeth in the cut and again reduce load. Have someone else there with you in case the blade does jam to shut off the machine. It's no fun wrestling an angry saw with one hand and reaching for the kill switch with the other. (wich has now shrunk to half its size and moved just out of reach when you realy need it)

The accuracy of the cut will be no better (and possibly worse) than that for cutting wood (+/-1/32")so expect to do some clean up with a file. As far as thickness of stock, limit yourself to aluminum plate (1/8" to 1/2") for alluminum sheet you can find a finer piched blade but consider using a band saw or reciprocating saw.

If you have a band saw available with the capacity you need consider making the rough cut with it and bringing to final dimension with a 1/2" router running on a fence.

This is very do-able but it's not like ripping a 2x4 either. Think the process through first and test a small piece first. AND DON"T WEAR GLOVES AROUND THE TABLE SAW!

Dave Opincarne
03-07-2003, 08:27 PM
One more thing (applies for all sawing opperations): Don't stand so that you're sighting down blade as it's running. That's the path that a loose tooth or chip is going to take if it comes off.

brunneng
03-07-2003, 08:33 PM
Thanks guys,

I do have a small metal bandsaw and the first thing I wanted to do was to cut some .5 al plate to size for a table to use on it to cut the rest of the metal on the bandsaw. So size isn't that important for this one.

Wish I had a plasma cutter or shear.

Alistair Hosie
03-07-2003, 08:34 PM
I have cut aluminum on a tablesaw many times and so long as you pick a good quality high tooth blade with a slow feed you should be okay cut it like you would any hard wood. Watch out to clean up well afterwards as it leaves tiny fragments which must be cleaned away if you go back to cutting wood.As far as kickback is concerned the main reason for kickback is either careless feeding,or when the sawblade is cutting, and the stock being cut is twisted or moved during cut,or not applied to the blade when flat on the table, or that when cutting say twisted ,wet, or damp, timber with a saw without a riving knife and the damp or twisted timber which does not sit on the table properly closes behind the blade after the initial cut is commenced throwing it back at you.
To more fully understand how or why it does this you should understand how a blade functions.If you look at a stationary blade from the side ie crouch down at the side of your saw with the machine preferably off, raise the blade to full height to look at it during this excercise and look at it carefully, draw an imaginary line down the centre of the blade top to bottom,I E seperating it front from rear you will see that , the first half of the blade I e the half of the blade towards the front of the saw when spinning ,(Assuming as the blade is spinning in the correct direction) IE towards you as you stand at the front of the saw (actually you should always stand to the side a little in case of kickback) will push down the stock in the direction of the table as the blade is revolving in this direction. When the stock passes the halfway point of this imaginary line towards the back half of the blade you will notice a sudden change as the tendancy of the blade will be not to push the stock down but to lift it up in the direction it is going.So long as the blade is not hindered i e does not make contact with this rear portion as it is revolving helped by a riving knife being in position which should be just slightly thinner that the kerf of the blade in use,kickback should not be a problem as the kerf will produce a slot big enough to clear this part of the blade before it passes this point.Obviously as said the chances of kickback are greatly increased if the stock wanders or twists during cutting so a fence is very important and it should be fed slowely being pushed slightly towards the fence to avoid twisting or moving during the cut.
Also I would not advise anyone to try to cut very small pieces on the tablesaw in aluminum.Better to cut sheet stock as I did I cut 3/8th stock with a ten inch blade with about 68 teeth tungsten or more actually you can buy blades specially designed for this .When setting upjust leave just a little of the blade exposed above the thickness of the material about a few millimetres below the gullet of the blade,I E so that the only part of the blade showing during the cut is the tips and gullet below the cutting teeth plus a little more say a few millimetres,dont raise the blade any more than this as it is unsafe. This should also reduce the likelyhood of lift.I hope this is clear.If you feel nervous about it leave it alone and use a small jigsaw /sabre saw with a fine metal blade.Alistair

brunneng
03-07-2003, 09:10 PM
No, I'm comfortable with using the saw (been using it for 20 years) just never on metal. I'm familiar with the technology/safety procedures, etc... I know you don't know that about me however... http://bbs.homeshopmachinist.net//wink.gif and you never know about who else will read this.

I figured you'd cut it similar to expensive high density plywood. Minimal exposure of blade above material to limit blade rub and tearout of surface from the rising back teeth.

Believe me, I respect the power of a tablesaw. I've seen 2x4's thrown through a wall when ripped down the middle.

Rich
03-07-2003, 09:21 PM
brunneng:I'm a woodtick by trade but have cut alum sheet on my table saw on occasion.For a few cuts any carbide blade will work--be absolutley sure you have control of the work piece and use a slow feed.
Dave:I understand your theory about raising the blade to force the cut towards the table,but I feel this creates more surface area on the blade to launch a kickback.I cut with the tip of the tooth barely above the surface.
Alistar:I agree on not cutting short pieces.My motto is "Short pieces make short fingers"
Kick back is a nasty thing on the table saw.My most memorable one was a 26" piece of 2x6 to the nose.Between the unique pain and handfulls of blood I had to figure out if my nose was still on the front of my head.All I ended up with was an embossed woodgrain bruise.
And yes,carbide teeth do come off some times---I caught one with my safety glasses once.
Rich

wierdscience
03-07-2003, 09:35 PM
Always on aluminum run the blade all the way up!Never with the minimum exposed,with the blade up the sawteeth arc down to the table on a high angle there by reducing kickback and lift up if you are worried about the top of the blade being exposed cover it with a gaurd suspended from the ceiling if lift up is a problem attach an ajustable hold down roller or feather board.If you make the cut at a low blade projection the force of the cut is directed at you instead of down against the table.I saw 3/4"plate routinely in this manner with no problems.It also helps to give the blade a shot of wd-40 or similar before every cut.As for kick back be sure and adjust your fence perfectly parallel to the sawblade.Also a sharp(new)blade is a must.

George Hodge
03-07-2003, 09:53 PM
I've cut aluminum sheet,angles and bars on both my 10in.Dewalt radial arm and tablesaw.Both do a good job. Wear ear protection and eye protection. It's really noisy and like everyone says it makes a mess. But if your saw makes smooth cuts on wood,it'll do the same with aluminum.On the radial arm,I clamped the material down. On the table saw,be sure the material doesn't slip under the fence.Try some parafine on the saw blade.

Dave Opincarne
03-07-2003, 10:08 PM
I'm a patternmaker currently and my last job was at a very high end custom cabinet (read built in furniture). Worse case of kickback I know of (wasn't there at the time) was on a 14" Altendorf. The forman in the production half of the shop was missing a couple of fingers. Not from the blade, but when the board he was ripping kicked back it hit him in the hand taking his fingers with it on its trip across the shop where left a bloody dent in the wall.

Rich, while raising the blade higher above the work does increase the dangers assosiated with the exposed blade, it definetly reduces the area the blade cutting through. Think of it this way: the shortest distance through the material is perpindiculer to the surface. As the angle of the cut becomes shallower, the linier distance from the front of the cut to the back of the cut is increased. Keep in mind that I'm talking about the area were actual cutting is occuring, not the leangth of the blade in the kerf. If the blade has a decent amount of relief and the fence is adjusted parallel to the blade, lift from the rear half of the blade is negated. Additionaly, if the splitter and guard are in place the increased danger of an exposed blade is minimised since they will be covered.

This advice is specific to the situation in the original post. For wood cutting I place the blade so the gullets are fully exposed but no higher. Note that the risk of kickback is higher with wood which twists and binds as it is cut.

-Dave

Rich
03-07-2003, 10:41 PM
Dave:Just relating what has worked for me in the past.I'll try it your way next time though.I still say control of the work piece is paramount though----no matter what the tool.
Rich

Dave Opincarne
03-07-2003, 10:52 PM
No argument there. http://bbs.homeshopmachinist.net//smile.gif

wierdscience
03-07-2003, 11:13 PM
I have been thinking about a rubber tire with a sprag clutch inside to eliminate kickback totally ,woodworking has a similar set of kick back rollers made out of green plastic and they seem to work pretty good.I figure a go cart tire fore and aft ought to do it and you could adjust the air pressure for hold down force,just a tought.

Dave Opincarne
03-07-2003, 11:35 PM
For what kind of machine/operation?

SJorgensen
03-08-2003, 12:26 AM
I can see the logic of raising the blade to decrease the tangential kickback force, but as the angle of approach to the blade increases, less teeth are in contact with the material. Shouldn't some thought also go to that rule of having at least three cutting teeth in contact with the material at all times?

Spence

Sprocket
03-08-2003, 12:33 AM
I cut aluminum on a 14" Delta bandsaw all the time, It's a single speed, and that is a little fast, but it does a great job on any aluminum that is not too gummy, 2024, 6061 cut fine, there was some 3000 series I think that gummed up the blade. For the most part, it works like a very consistent hardwood

docsteve66
03-08-2003, 01:21 AM
All the above agrees with my experience but I routinely use a plain steel saw (10 inch) on 1x6 inch Al. Have used both table and radial. I prefer the radial for this although for wood I do not like the radial. Ifyou in feed on radial clamp the work well, on out feeds keep the saw from climbing. I use a regular cross cut blade with coase teeth.

I keep wondering if one of those "steel saws" (almost round blade, some slots and i think they cut tin by friction) would work.

Thrud
03-08-2003, 01:57 AM
Rich
I agree with you. First rule of safe table saw operation is to use minimum blade height.

For Aluminum a 80T ATB or TTG carbide blade works best. A chop saw can be used to cut structural Aluminum but be advised to clamp it down well on both sides of the blade. I used to use our 18" Cold Saw (Pnuematic hold downs) - I was cutting a 6"x6"x1/2" angle on a 45* and the one hold down broke. Geezus H. Murphey I nearly had to clean me shorts out! More excitement that I needed that day.

darryl
03-08-2003, 02:35 AM
I've cut a lot of aluminum in my time on the table saw. Use a carbide blade with lots of teeth. There's lots of good advice above, I would just add that it helps to have the blade stiffened up, put a 'washer' either side of the blade, make two up on the lathe. bore to a nice fit on the arbor, and give the inner sides a slight concave. That way, when you tighten the nut, these washers compress slightly, giving the blade the best support it can get. Make these 3 inches dia. or more, depending on your blade, it doesn't help much with a 10 inch blade if the washers are too small. Next point I'd like to make is to have minimum 3 teeth in the metal at all times. The blade will follow the kerf better. This is where setting the height of the blade is critical. Not too low, there's too many teeth in the metal, and there'll be too much heat. Not too high, the interrupted load on the teeth is too much, and this can knock the teeth off. There is a setting that works right, eyeball a test cut, and see how many teeth are in the groove at one time. I usually wear gloves when cutting al., as the swarf is sharp, hot, and may cause you to flinch, possibly lessening your grip on the workpiece. Also, the aluminum will get hot, and you'll want to let go of the piece. This could be fatal. Of course, make sure you don't get the gloves caught in anything, that stands to reason. I think, mho, that it's safer to wear gloves for this use, but safer to not wear gloves for wood and plastic cutting.

[This message has been edited by darryl (edited 03-08-2003).]

Rich
03-08-2003, 09:54 AM
Dave:Care to share any comments on the patternmakers trade with us?It sounds like a very interesting branch of the woodworking industry----challenging projects,top end equipment and materials,or so I've heard.Is it still a viable trade or are you being displaced by CNC routers and synthetic materials?
Rich

Cass
03-08-2003, 02:00 PM
I have cut 2 inch thick 6061 and 7075 aluminum plate on my 10 inch Unisaw with no problem. I have cut large amounts of 1-1/4" plate 7075 aluminum. I use a combination tooth carbide blade. 1/2" to 1" thick cast aluminum tooling plate also cuts nicely. I extend the blade just above the material thickness just as I would when cutting wood. I advance the material somewhat slower than wood as determined by how it appears to be loading the saw motor. I want the blade speed to be constant and not much slower if any than when cutting wood. I do not worry about metal fires and have never had one when mixing chips with wood chips. The chips are much too large to cause a chip fire. I think it is hazardous to feet too slowly as that creates a lot of frictional heating which is likely to cause the blade to be damaged. From other machining operations it has been determined that there seems to be no upper limit on cutting speed on aluminum such as there is with steels for example. The surface feet per minute for wood cutting is just a nominal speed compared to modern high speed milling where end mill speeds get to 50,000 rpm. I do not use coolant like WD 40 as it does nothing other than make a mess. It is required to use ear plugs, safety glasses and preferably a full face shield, I do not use long sleeves or gloves which are dangerous. I do stand to the side which is good general practice with any table saw operation. I have seen very little wear or built up edge on the carbide blades I have used. I think a standard blade is much better than a thin blade because of the higher lateral stiffness. I think one of the most important features is to have a powerful saw. I would not do this operation on a lightweight table saw. The Delta 10 Unisaw is heavy and powerful enough to allow the material to be feed to the blade fast enough to limit frictional heating due to rubbing.

Dave Opincarne
03-08-2003, 02:21 PM
Thanks for the invite Rich. I'll try and give you a quick picture. Most of my experience has been in aerospace tooling (com posite) which is very similar to patternmaking in many ways.

It is easy to romantisise about a trade with a lot of specialized knowlege. Like most things, reality is different than perception. The popular image (read wishful thinking) is of a bunch of gentlemen craftsman crafting wood largly by hand. BOGUSS! We only use wood to hold the large quantity of bondo together.

The trade is dying due to asian foundrys that sell castings by the pound. Fortunatly, the company I work for specializes in custom trackwork and rail road crossings and switches which are cast from manganese steel so we are able to keep going. Most of our new work is made on the CNC router but it is time and labor intensive to finish on the router so we only mill out the rough shape and finish by hand using lots of bondo. Fortunatly, we still make coreboxes and core prints by hand so we still have some interesting work to do. Also, we spend a lot of time repairing and modifying existing patterns. Patterns get dirty and beatup fast so rework can be dirty and unpleasent with lots of hidden screws. Also there's lots of bondo, did I mention the bondo? We do get to make new patterns by hand on ocasion but those are usualy small ones. Pattern work is a strange combination of precision and crudeness. Many forms are done on large disk sanders and are just roughed out unless they need to be precise. The real trick is knowing what needs to be acurate and what can be good enough. The biggest chalenge is gaining the specific knowlege relative to railroad track work.

Pattern work is a very strange amalgum of different disaplines. There's a lot of layout so drafting skills are required, we do use a lot of skills common to machinests as well. Materials are not top quality wood. We use a lot of pine with big pitch pockets, "perfect plank" which is made of finger jointed shorts glued up to make large blocks, and poplar when we need a "hard" wood. We use a lot of other materials like leather for fillets, wax, clay, and castable urathane. Oh and also bondo!

-Dave

lynnl
03-08-2003, 02:36 PM
My son-in-law's shop has a large DOD order for structures made of 6" Alum channel, about 3/8" thk. Lots of angles involved. He bought a 10" radial saw for that purpose and says it's working great. Of course w/radial arm saw you have to feed the carriage backward into the cut and have it clamped down securely. I didn't see it mentioned above, but I think a TCG (triple chip grind) blade is what's recommended for aluminum. I had made a trial cut for him before he bought the saw, and that's the blade I used.

Rich
03-08-2003, 04:09 PM
Dave:Thanks for smashing my image of old-world craftsmen clad in white shirts and black vests creating a labor of love out of yard wide planks of old growth Mahogany with nothing more than a sharp spokeshave.On the other hand ,my perception of Bondo has been elevated far beyond the common application of mudding up gapping holes in a 67 Chevy.(You did say Bondo,did'nt you?)Our local paper ran an article a while back about an entrepeneur who purchased the now defunct Beloit Corp. plant in Beloit,WI.Along with it he got about 500,00 patterns from decades of production.Beloit Corp was a large manufacturer of paper making machines.These patterns are now being utilized by artists and designers for sculpture and furniture projects.They offer tours of the plant so I'm think'in that might be a good road trip some weekend.
Rich

brunneng
03-08-2003, 04:40 PM
Dave: That's cool on 2 counts. On one hand I'm into model railroading and I'll eventually get into the 1-1/2" scale stuff as we have a local group doing that with a couple acres of track.

Also I worked with some guys who make fiberglass RC planes and we used bondo to cover the core models for the fiberglass molds. That stuff can get sooo smooth. Then cover it with automotive paints and buff to a high gloss so the epoxy will release smoothly and the finished bodies/wings don't need any cleanup other than at the joins.

jfsmith
03-08-2003, 05:08 PM
I found an old Sears Craftsman, all steel table saw at a yard sale for $5.00 I replaced the motor on it and only use abrasive blades and diamond wafer blades on it. It's only purpose it to cut metal. Plus I can cut slots in metal with it.

Jerry

wierdscience
03-08-2003, 09:31 PM
No,I don't mean use wd-40 for coolant ,just one shot on the blade now and again to keep the gooey alloys from sticking to the teeth.I also get good results from the Tapmatic tool sticks.

tattoomike68
03-09-2003, 02:56 AM
a little wd40 will do it but dont be a puss you have to shove it though fast and keep the feed rate up and the wd 40 will keep the chip weld down.
i cut 1" on a tablesaw and routereed a .75 endmill for making matchplates at a foundry and it was bad but worked.
ask me about any prob if you have them.

Paul Alciatore
03-14-2003, 01:28 AM
Have a 10" raidial arm saw at work and use it for cutting 1/8" to 1/4" aluminum from time to time. The kickback problem is non-existant when "cross cutting" (to use the woodworking term) as the blade rotates to push the aluminum against the fence - away from me. A "rip" cut would be significantly more dangerous as stock should be fed against the rotation of the saw and can kick back. The saw and it's manual has several warnings about feeding with the rotation. The workpiece can be pulled from your grip and be sent flying across the room at great velocity. Very dangerous! The saw has a anti-kickback paw but I don't know if it would work with metal. I have not attempted any "rip" cuts in metal. I don't plan to either.

I use a 48 tooth, 10" blade and cut dry. The most important thing is to carefully control the feed rate. If the blade diggs in, it will feed faster and jam. I clamp the work down so both my hands are free and use a two handed grip on the saw head (one pulling and one pushing) to control the feed rate.

Some words of wisdom (experience) about the radial arm saw. I heard many bad things about their accuracy and discovered the reason for this when I attempted to align it per the manufacturer's instructions. Fact is, these are not made with heavy metal castings like machine tools. The frame of the saw is made of sheet metal and; surprise, surprise; it bends. It warps. It twists. After returning one saw and two more unsuccessful attempt to align the second one, I performed a single step of the process and then moved the saw about 3 inches sideways. Lo and behold, the alignment step I had just performed to perfection was now off by a lot. The one installation step that the manual omitted was: BOLT IT TO THE FLOOR AND NEVER, EVER MOVE IT. After I did that, it aligned perfectly and has held for several years now. The irregularities in the floor were only about 1/16".