Machining Aluminum

Can't say I'd use a single flute "bit".

I'd use either a rotary file or a 4 flute end mill, and take my time. Tool wear and wander would be a concern, especially over 42".

Was thinking about 4 flute but friends told me that 4 flute will plug much faster since aluminum is soft. Anyway I will have lots of cutting to practice and see which one does a better job.

Wear is expected and have a few bids to replace as needed

Wander will be very bad and was looking for ideas, if any, to prevent it

Don't understand the rotary file; what is it?

Lubrication will help with clogging. Use a solid grease stick. Whatever you use, USE MORE THAN YOU THINK YOU NEED. Remember industrial cutting/milling operators FLOOD their work with lub/coolant. If your work area is clean, you aren't using enough coolant. Some guys think you can machine/cut aluminum with no lubricant.

There are many Al lubes offered.

Same with rotary files.

Rotary Files Catalog.pmd

There are 2-flute bits made especially for aluminum. I would use a 1/2" bit if your router will take it. otherwise a 1/4" bit. 1/8" is too small. It will break quickly. Check with http://msc.com for those bits.

Onscrud also makes single flute bits for aluminum as used in CNC routers.

'...perfectly level and square...'

'...any better ideas?...'

.

The closest you are going to get to perfectly square and level will likely be scraping.

.

Though it will likely take a little while to learn...and take a while to finish a piece once you do...there are some benefits:

.

You can do it yourself with inexpensive or shop made tools.

.

Precision can be obtained that would be difficult to rival with any other method.

.

You are working in aluminum, so although sweat equity will be invested....not nearly so much as with many other metals.

Don't really understand your post

As I mentioned in my 1st post I did some slots last year and they were perfect (the location, width and length of them was critical). This doesn't mean that my current machining will also be perfect but I'm willing to give it a try and if the 1st piece does not turn as expected, then its time to look for alternatives

The purpose of this thread on the forum is to ask other experienced members to share their ideas and perhaps suggest different ways to complete my project

I am suggesting you consider taking up hand scraping.

.

Hand scraping provides an inexpensive way to attain very high levels of precision for a number of parameters important to tool making (which is at least in part what you are, as I understand, building a cnc machine).

.

I'm not belittling your previous work, or your ability to do this project.

.

I do think we are probably not communicating well due to having different definitions for some important words in this discussion.

.

When I read the word 'perfect' in relation to machining a piece, it means the piece was finished within the required tolerances. It means that to me, in part, because it cannot mean the piece was machined to exact dimensions with no error.

.

It might be a good thing to keep in mind that the lowest tolerance to which you build the functional parts of a machine tool, can easily end up being the ceiling for the most precise tolerance possible for work produced on that machine...much worse if you are not lucky.

.

So on your previous pieces, what tolerances were required? You noted size tolerance was critical. What type of accuracy was required/did you achieve?

.

In addition to size (some people say dimensional) tolerance, there are some other things that need to stay with bounds for most functional pieces. Among these are usually geometric tolerances and surface condition.

.

Even with width, height, length, and locations to cut slots all within spec, a piece can be physically very different depending on straightness, flatness, parallelism, perpendicularity, profile, run out, concentricity, blah blah blah.....

....you get my point.

.

Basically what I am suggesting to you is that if I understand you correctly in that you are constructing a cnc machine tool, that hand scraping can make accessible the best precision for things like flatness over distance very inexpensively.

.

Furthermore, hand scraping can provide a way to make your own highly accurate standards with which to compare things like flatness, perpendicularity, parallelism, etc.

.

Lastly, if either I have grossly misunderstood what you were doing, or if you are of the belief that 'perfect' (in the sense of being exactly a certain specified dimension) have been and will be made (and are unwilling to reconsider that notion), please just consider this the ramblings of a mad man....unworthy of reply. :-)

I have no problem with lubrication and lots of it. The Jarvis site looks very interesting and will study more later.

I do have 1/2" and 1/4" bits and will give them a try. My router will take them but I though the smaller the better; guess we always learn

Thank you both

You are only going to be within a few thou.

In a pinch I have used lots of WD40 as a lubricant - I just kept spraying it on.

A back fence that is true and at least 2x the length of your longest piece helps keep things straight. Use "fingers" (not yours) to press the piece against the fence,and take the cuts on the opposite side from the fence.

You will not be any better than your fence - try a piece of 3" aluminum channel.

I am surprised at using aluminum for a base for a milling machine - are you making a base for a small bench top unit? If that is what you are doing then use standard structural steel, weld it together, use heavy duty anchors into the concrete floor, then shim your machine as required. To check for alignment, put a dial gauge in the arbor and rotate the gauge across the table - it should have zero run out. If not, then adjust your shims.

Thanks for the info GW

I'm also hoping to be within a few thou, it will be great

The 2"x 2" fence I have it is an aluminum channel

Yes that's a base for my cnc, approx 30"x 40" cutting area. Structural steel is excellent but I'm not equipped to work with it plus my welding knowledge is not that great

Aluminum plate (if provided by a retail metal supplier) will most likely be cut on a table saw with a carbide tipped blade. Regardless of the amount of coolant used in cutting. The aluminum ALWAYS twists/distorts.

I would try an Aluminum manufacture (Reynolds Aluminum etc. Google Aluminum Manufactures for listings) and ask for extruded aluminum tooling plate in the width that you require. (6 in. x length) They can provide you with their manufacturing tolerances which would be much closer than commercial tolerances for aluminum plate. If the tolerances are within your requirements, you'll save a lot of your time.

I'm not sure of the alloy, 6061, 6063, 7075, or the temper. I believe they can offer you the most economical solution for your project.

I'm trying to keep my answers short and sweet. A lengthy post keeps getting dumped!! (I assume timed out)

Alcoa Aluminum~Lancaster PA. (800 543-6265 or 717 393-9641 x-1396) lists a Cast Aluminum tooling plate MC 6 Cast Aluminum Tooling plates

pdf specs on~line:thickness tolerance +-.005 on all material

flatness tolerance .015 on 1/4 to 5/8 thick material

.005 on 3/4 to 4 in. think material

Finish 20 micro inch/both sides

You might give them a call regarding 6 in width availability or charge to cut to 6 in width.

If these tolerances are within your requirements and cost is within budget, your in high cotton.

Tooling plate is very expensive, compared to flat stock, but worth a look.

In the description of what you are trying to do you will soon learn why the 75 dollar set up fee. As the placement of your fence is going to be critical to getting the tolerance your asking for. A hand router turns at a high rpm to high for aluminum with out a coolant.

What I don't understand is why the base has to be so perfect. The linear rails or bars for motion I can see. And those can be adjusted with shimming to and irregular surface their mounted to.

The new one will be similar but larger and with additional features etc.

In my area its not easy to find what I need and sourcing aluminum from aluminum manufacturers / distributors its very expensive especially in small quantities.

Ordering flat bar instead of plate is another solution if maching with my router is not succesful. Then I can shim as needed to achieve what I want (that's what I did on the previous cnc)

That is am amazing piece of fabrication!

Your frame is actually not that critical, I would guess if you are within .050" you would be OK, especially if the pieces match each other, you just need a nice finish. Go ahead and use the router, with some coolant. Your final tolerance comes from the precision of the linear slides, so as long as you fasten the frame to the floor as a "massive" stable anchor, then you can shim the rails for the parallel and level that you need.

Again, I would swing a dial indicator on a long arm in your arbor to get a final square head and level table.

-One job I did for Alcan on a rolling mill - they used kerosene as the coolant / lubricant. (But it did catch fire occasionally - they used CO2 for extinguishing the fires and never stopped the machine.)

I agree. I think you can handle the task before you with great skill and precision.

Good luck, why not blog it here?

Admin is looking for craftsmen such as you, and many of us would be keen to follow your progress.

Beautiful work. Looks like you have quite a bit of money invested. Can you salvage any of the metals for your new machine?

Since you are only a few miles north of the U.S. It is possible you could order what you need from a U.S. company; have it UPS'ed to the nearest depot closest to the border and then you could drive over and pick it up. This could save you money and especially most companies don't ship to Canada.

If you still have that cnc table why not use it.

Glad you liked my old cnc and I agree that going with flat bar instead of plate will be the best and least expensive solution (plate is almost double the cost). Ordering aluminum from USA is too expensive because I will still have to pay the taxes + you add the custom fees + the transportation cost to the border and still have to drive to the border to get it. I'm very happy with the shop I have here, I can buy at a very good price 1 piece or as many I want and they deliver it the same day free of charge (if I order early in the morning)

Regarding blogging my progress, I started a thread at CR4 here when I wanted help with the vacuum system and so I will blog on that thread because I was asked the same from other members

Right now I'm building a model out of 1/2" thick MDF. When the model is done I will order the aluminum pieces I need as per my model so I know they will fit. I have also ordered the linear rails / ball screws from China and they should be here towards the end of the month

Since I had to drill precisely the edges of 48" long aluminum pieces and they did not fit on my bench top drill press, I had to modify the press as shown on these pictures. Kind of primitive but it worked.

The cnc table you see in the pictures was sold last X-mas

depends on what your fixture is.

At the ship yard, we used 3/8" and 1/2" carbide cutters, single and double spiral down cut (Down cut because we used a vacuum table for securing the piece) 1/4" per pass, we had larger routers, don't recall what rpms or feed rate, Also, an 1/8" bit is small, 2 IPM should cover that but careful with burning up your bits. Remember your chip load may not be high enough to carry your heat away.