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BobS
27th Jan 2005, 04:39 PM
I need some advice on how to work with Aluminium eg
Grinding it down to size, sanding / polishing it etc

I have found an aluminium frame from an old built-in cupboard that I'd like to use as the mitre track in a Router table, however it's going to need need some work first

PS I know from harsh experience not to go near the grinding wheel !!

Regards
Bob S

Termite
27th Jan 2005, 04:43 PM
Bob, with the price of aluminium extrusions I'm not sure that I'd bother modifying something. However, you know about ginding wheels and ally will choke a file in nothing flat. Sorry I cant be a bit more positive on this matter. :o

scooter
27th Jan 2005, 05:42 PM
Gday Bob, & welcome aboard!

Aluminium can be cut with a hacksaw (less tpi the better, fine teeth will clog) or using a power saw (ie. mitre saw) with a carbide tipped blade. WARNING - aluminium cutting blades usually have negative rake teeth, different to wood blades; however if you only have a few cuts to make you CAN cut Al. with a wood cutting blade provided you take it fairly slowly and carefully. I have done this successfully with my mitre saw & it went OK for me. Read a tip suggesting you put duct tape where the cut will be prior to cutting, haven't tried it but it apparently made a huge difference to the amount of swarf on the exit side of the material.

Al can be filed, but will need to chalk the file first (as it reads, rub chalk into the teeth on the file), this will prevent clogging. If you get some clogging anyway, use a file card to clean the file, and the corner of a bit of sheetmetal to push out any stubborn bits (a clogged file is called a "pinned" file BTW.)

If the al. is oxidised there are a number of compounds to polish it up, one of the best is Autosol paste, brings al. up a treat.

Good luck mate...........cheers.............Sean the heavily oxidised

bitingmidge
27th Jan 2005, 07:52 PM
I know from harsh experience not to go near the grinding wheel !!


I've heard all sorts of things about people who have been incinerated by explosions grinding steel after some idiot has ground al on the same wheel, but always believed them to be urban myths.

What DO you know about grinding aluminium from harsh experience?

Cheers,

P :confused:

Barry_White
27th Jan 2005, 08:10 PM
As well as cutting aluminium with power saws you can also use a router on aluminium just so long it is securely clamped. I have cut it with my mitre saw as well as on the Triton saw bench. As Scooter says there are proper aluminum blades made for it Irwin make them, a 10" 80 to 100 tooth blade for about $160.

BobS
27th Jan 2005, 09:30 PM
Thanks for the feedback

Bitingmidge - sorry no explosions but I do have an old Aluminium Oxide grinding wheel that now resembles a lamington.

I was particularly interested in what I could use to remove (grind off) a 1mm lip from one side of the profile.

Bob S

Barry_White
27th Jan 2005, 09:40 PM
You probably need to dress it up with a dressing wheel either hardened steel or diamond. Try Carbatec.

Groggy
27th Jan 2005, 09:47 PM
I've heard all sorts of things about people who have been incinerated by explosions grinding steel after some idiot has ground al on the same wheel, but always believed them to be urban myths.

What DO you know about grinding aluminium from harsh experience?

Cheers,

P :confused:
Well, as a young sprog I had my **** kicked by a foreman for grinding aluminium. He told me that the pores in the wheel clog and the heat cannot dissipate. So when steel is ground the wheel can heat up to the point where it can't expand, then it cracks. Since it is spinning so fast people claim it explodes. In reality it is just a very sudden release of energy and high velocity particles flying around the work area (hang on, that sounds like a ....).

As Barry White mentioned earlier, the Irwin blades do a good job cutting aluminium (although you can cut it with any blade with a large amount of teeth - 100+ on my 10" Irwin blade). Just make sure to spray the blade with some CRC Cutting Oil or equivalent to ensure the aluminium doesn't stick to the blade. It's a royal pain to get off if you don't, and the cut quality will suffer markedly too.

Oh yes, and prepare yourself for an unbelievable mess. I cut aluminium on my SCMS and found the workshop looked surreal when I had finished. Everything glittered like tinsel. Recommend you wear eye and respiratory protection - and a hat.

CHJ
27th Jan 2005, 10:06 PM
Well, as a young sprog I had my **** kicked by a foreman for grinding aluminium. He told me that the pores in the wheel clog and the heat cannot dissipate. So when steel is ground the wheel can heat up to the point where it can't expand, then it cracks. Since it is spinning so fast people claim it explodes. In reality it is just a very sudden release of energy and high velocity particles flying around the work area (hang on, that sounds like a ....).


Yes second that from experience, have seen results of wheel that had (initially) a large chunk break away and culminated in a guard case full of wheel sections.
Unfortunately for the individual using it at the time he stopped the 10% that wasn't contained from injuring his mates.

Cause: grinding of Brass and sharpening of Pencils, supervisor got a rocket for not controlling use and monitoring state of equipment.

A good guide for detecting a wheel that is clogged is a need to apply more pressure to obtain a cut, unfortunately this need can creep up on you.

soundman
27th Jan 2005, 11:19 PM
There is no real problem with files & aluminium you just have to clean them regularly.
It works quickly & relatively cleanly with a file.
It machines well with normal carbide wood working tools but it makes a lot of noise & mess and you must have very very firm controll of the job and the tool.
A good wax or liquid lubricant is a must for any power cutting.

Its also quite cheap if you buy it in the right place.

DanP
28th Jan 2005, 01:27 AM
Rub chalk on the file before filing aluminium, it slows the clogging.

Dan

Big Clint
28th Jan 2005, 11:53 AM
Gday Bob, & welcome aboard!


If the al. is oxidised there are a number of compounds to polish it up, one of the best is Autosol paste, brings al. up a treat.

Good luck mate...........cheers.............Sean the heavily oxidised


I came across something I think is better than autosol. Mothers aluminium and mag wheel polish, Comes in a tub (supercheap sell it here in perth). I found it works alot easier and the black stuff (not sure what that is caused by exactly) all rubs off easier. it is also good for stainless.

sailingamerican
28th Jan 2005, 06:09 PM
One, why bother polishing the aluminum? Won't make the table any better. Time better served working. Two, Use a hand 4 or 5 inch grinding wheel on a hand grinder. Three, They do make wheels for the bench grinder just for aluminum. Four, do you have a way to weld the aluminum? you can do it with a torch and special rod. You can use a regular wire welder with aluminum wire. You will need to use a little larger orfice so it will not hold up and you must keep your lead streight. You can weld in one inch lengths with no problem I do it all the time. Finaly make the thing out of plywood or MDF. You can make a great protable router table from a half sheet. I have made many of them. I can make two in an hour. No give, no warp I do have two comercial router tables. one has a cast top and a sliding table. I have used my wood ones for 25 years. They are great for the job site when needing to make special little moldings on site. My tables have a 24 by 30 inch top. I make them big because it supports the work so much better. I work with a private school shop that runs on a budget. I made 6 of the tables for them years ago and they are like new. They are used every week.

Yes, regular wheels can explode from build up. I was a tool and die maker before I became an Architect and contractor. I have seen them explode.
Another safty note for welders. Do not keep a disposible lighter on your person. Sparks can burn through and blow the lighter up. I have seen pictures of a man who blew his leg off from having a lighter in his pocket while welding.

DanP
28th Jan 2005, 07:47 PM
Do not keep a disposible lighter on your person. Sparks can burn through and blow the lighter up. I have seen pictures of a man who blew his leg off from having a lighter in his pocket while welding.

Richard,

Still use a zippo lighter to this day for that exact reason. Found one of my plastics one day with a bit of spatter burnt into the side of it :eek:

Dan

gatiep
28th Jan 2005, 08:36 PM
Maybe migrating here was a mistake, I should have gone where the knowhow is! LOL.


:D

bitingmidge
28th Jan 2005, 08:46 PM
This thread has some great stuff in it, meanwhile at the top of the page BobS has finished his bit of mitre track, failed to explode his grinder, polished all his cooking gear, relocated his cigarette lighter, and welded all the aluminium bits in his car together for practice!!

Phew!!

P
:D

journeyman Mick
28th Jan 2005, 11:09 PM
Okay, just some tips for working ally from someone whos done a bit of shipwrighting/fabrication on a few 25M boats and 18M semi-submersibles.
Tools for cutting/shaping: Jig saw, bandsaw, reciprosaw, circular saw with ally blade (high tooth count, negative rake), router with TCT bits, anglegrinder with meataxe or multi cutter blade. All to be used with plenty of lubricant, either metho out of a spray bottle or liberal applications of wax.

The meat axe or multicutter blades are pretty frightening. The meataxe is a 4" circular blade with triplechip tungsten tips about 5mm wide. It's used to gouge out butt joints in hull plating so you can get a proper v-joint to weld into halfway into the plate thickness. You tack the plates together, gouge out one side, fully weld it, then gouge out the other side of the plate and fully weld it.
The multicutter blade is also 4", but very thin kerf, about 2mm. Will cut its way through 6mm plate (or arms, legs, bone or tendon) in the flash of an eye - I've seen one horrific accident and had to give first aid! :(

Grinding/sanding. 4" angle grinder with thin flexivit discs, wax regularly. Sanding discs on rubber backing plate in angle grinder. Bench grinder with a wire wheel on one side and a linishall (6" sanding disc and a sanding belt) on the other.

Welding: You must deoxidise the surface before welding with a uncontaminated stainless steel wire buff. If using a MIG welder it must have a plastic liner in the feed line. It doesn't need to be kept straight and you should use the correct size tip for whatever size wire you use, ie .8mm wire, .8mm tip. You will need a hell of a lot more power than when welding steel as the ally just sucks the heat up. If welding thicker sections than your MIG can handle preheat with an oxy set. TIG gives the best results, oxy welding with a filler rod is a waste of time.

Mick

gatiep
29th Jan 2005, 02:41 AM
Hey Mick, are you sure, because you are contradicting some other posters!


Have a good weekend

:)

soundman
29th Jan 2005, 11:07 PM
Interesting stuff aluminium, I've noticed that it seems to evoke all sorts of pasonate comments about working & engineering with it. It even seems to have its own culture of wives tales.

I think this may be because the approprite methods vary widely depending on, the task, thickness, compound, very much on what equipment you have to work it with and how much risk you are happy with.

Even discussing lubricants can get exciting, I've found that a lubricant that is wonderfull for one cutting operation can be completely useless for another.

Example
Was cutting holes in dicast boxes ( common sound guy thing) ( hole saw kept exclusively for ally) some of the boxes cut nicely without lubricant ( smooth, clean, good waste clearance ) different brand needed a brew of metho & detergent bassed cutting compound or the hole saw clogged fast & hard.


Continue.... :D

Cheers

vsquizz
29th Jan 2005, 11:41 PM
There is no problem whatsoever in grinding aluminium provided you use the right disc's or wheels. Thousands of boilies do it everyday. Your standard wheels for steel grinding can have a problem as pointed out. Flexovit provide good quality grinding discs and wheels for aluminium. For hand held grinders the disc will usually be "for masonary or aluminium".

All the shops I worked in had a knob of wax at the designated Aluminum Grinder for keeping the wheels in good nick. Don't get your wheels/disc's mixed up. When you buy a aluminium wheel/disc give it a spray of bright paint around the hub so that if the label comes off you still know which is which.

As an apprentice I was warned of the "exploding wheel" when ally was ground on standard wheels. I think the failures had more to do with vibrations setup by the imbalance when aluminium clogged the wheel.

Ask your supplier for his tech sheets (guidlines) from the manufacturer if you are unsure. Have a look at DOCEP:

http://66.102.7.104/search?q=cache:toJ9cxsbaIUJ:www.safetyline.wa.gov.au/pagebin/pg000383.htm+Aluminium+grinding+wheels&hl=en

Squizzy who has never shattered a wheel in his life but has seen the results of a few.

Cheers

sailingamerican
30th Jan 2005, 04:17 PM
Okay, just some tips for working ally from someone whos done a bit of shipwrighting/fabrication on a few 25M boats and 18M semi-submersibles.
Tools for cutting/shaping: Jig saw, bandsaw, reciprosaw, circular saw with ally blade (high tooth count, negative rake), router with TCT bits, anglegrinder with meataxe or multi cutter blade. All to be used with plenty of lubricant, either metho out of a spray bottle or liberal applications of wax.

The meat axe or multicutter blades are pretty frightening. The meataxe is a 4" circular blade with triplechip tungsten tips about 5mm wide. It's used to gouge out butt joints in hull plating so you can get a proper v-joint to weld into halfway into the plate thickness. You tack the plates together, gouge out one side, fully weld it, then gouge out the other side of the plate and fully weld it.
The multicutter blade is also 4", but very thin kerf, about 2mm. Will cut its way through 6mm plate (or arms, legs, bone or tendon) in the flash of an eye - I've seen one horrific accident and had to give first aid! :(

Grinding/sanding. 4" angle grinder with thin flexivit discs, wax regularly. Sanding discs on rubber backing plate in angle grinder. Bench grinder with a wire wheel on one side and a linishall (6" sanding disc and a sanding belt) on the other.

Welding: You must deoxidise the surface before welding with a uncontaminated stainless steel wire buff. If using a MIG welder it must have a plastic liner in the feed line. It doesn't need to be kept straight and you should use the correct size tip for whatever size wire you use, ie .8mm wire, .8mm tip. You will need a hell of a lot more power than when welding steel as the ally just sucks the heat up. If welding thicker sections than your MIG can handle preheat with an oxy set. TIG gives the best results, oxy welding with a filler rod is a waste of time.

MickOn small portable welders the lead must be kept streight, the moter is not strong enough to feed the stiff aluminum. It does not matter the brand. Works every time. I went to the international wending convention in Detriot last year where I grew up. They are the ones who told me how to do it. By the way I worked for Boeing aircraft as a machinest and General Motors in their expermental division. I also workd as a sheet metal mechnic for the US Navy while running my construction business during the day. I had one grandfather that was a tool and die maker and had many aircraft patents. I went to a high school trade school and passed all the test for tool and die by the time I had graduated form high school. My other grandfather was a farmer and contractor. I got the best of both world. I had a contractors lisence by the age of 21 and at 41 went back to the university receiving a degree in architecure with a momor in math and physics. I have over 75 pieces of machinery and thousands of tools that I have been collecting for over 40 years. I can build you anything. Even the gears. I have the hobby shop insured for $250,000 USD. No I am not one of those know it all. Just been damn lucky that God put me in the right place and gave me a good brain. I teach industial arts in a private school. I do not get paid. Not bad for an orphan. My mother died from polio when I was 10 months old and my father died in the Korean war. I lived with the grandparents. They had the old fashion work ethic. They never quit until the day they died. I spent all my time working or hitting the books. I new no other life. I never went out on the town. By the time the the construction day and farm work was done in the summer I was so tired I fell asleep by 8pm . My wife is an Aussie and we spent part of the year at our cond in Coffs. If we did not have 7 children I think we would move to Australia on a perment basis. Now what is it that you all do? Richard Have a G'day mates.

gatiep
30th Jan 2005, 05:32 PM
MMMM with all you did in your life I'm quite surprised that you had time to have seven children....................must have been quickies or wind polination as you rushed past from job to job and you are only 54!! LOL. Good on you! I never did much and only have two daughters....twins, perhaps I was tooo lazy to try for singles or more twins!




On a correction: with the mig welders you omitted to say that the liner needs to be replaced with a nylon one when using the soft aluminium wire, as it rubs off on steel liners and causes malfunctions.


Seems like I should have migrated to USA, then perhaps I could have caught up on some training. We are very backwards in the rest of the world as you KNOW! Or perhaps we are not as outspoken and prescriptive. I really don't know.


:D

Jon
30th Jan 2005, 08:56 PM
aluminium files nicely with a dreadnaught file and doesn't pin (clog the file)

Jon

journeyman Mick
30th Jan 2005, 11:46 PM
Sailing American,
I haven't got nearly as much experience as you do, but I did supervise the building and fitout of three 25M aluminium boats. Even on smaller MIGs without a push/pull gun we found it okay to bend the leads as long as there was an undamaged plastic liner fitted. You must have a plastic liner to prevent contamination of the wire and excess friction. Had about 20 welders there, less than half of them had push/pull guns. We even had a small 150amp Lincoln MIG welder there for odd jobs/tight spots. When you build a large boat it's impossible to keep the run of the torch in a straight line. Now you may have a lot of qualifications and experience but all the MIGs you've used must have been pieces of junk.

Also you say :"You will need to use a little larger orfice so it will not hold up....". Now in my experience (very limited I know,) if you use a tip that's got a worn orifice it will definitely hold up. The wire needs to be a snug sliding fit in the tip, if it's not you'll get an arc between the tip and the wire which will weld the wire to the tip. So using a larger orifice sounds crazy to me. The tip is there to act as a electrical contact for the wire, so having a loose orifice would be counterproductive. But then what do I know, I'm only a carpenter.

Mick

gatiep
31st Jan 2005, 02:55 AM
Hey Mick,

You have overlooked one aspect. Everything is different in the states.
Maybe the keeping the leads straight, enlarged orifices etc has to do with their different voltage at 110V.

LMAO.

:D

Joe.......... the two jobs for life man............... gee I must be dumb!

DanP
31st Jan 2005, 08:21 AM
You've gotta hate a large orifice.

Sorry, couldn't let that one go.

Dan

scooter
31st Jan 2005, 10:20 PM
...and a worn one Dan.... :eek:

As mick says, a snug sliding fit is the go, and as soundman said, sometimes you need the appropriate lubricant and sometimes you don't.....

Hang on...........was that some kind of sexual innuendo you were hinting at...... Oh my... :o :o :p


Cheers...............Sean the immaculate

PS. Thanks Clint for the Mothers tip :)