Thread: Cutting Aluminum with a Router

Hi Luke

That's a curly problem you have there.

The way I see it, the tool you use is less important than being sure that you avoid cross contamination between cores.

We're taking lots of samples which need to measure contaminants in parts per million, billion, and even trillion, so nothing can be added.

I don't think a circular saw will cut it (please excuse the pun), even if you use a new blade for every core. Too much risk of contaminating the sample.

are the cores sufficiently uniform in diameter and lexan thickness that a saw could cut almost but not quite through the lexan?

do you sample a whole 6' section of core or only small sections of it?
if it's small sections, can you use a pipe cutter to extract the (say) 6" long core sample, drop the section into liquid nitrogen to snap freeze it than push the snap frozen sample out of the tube?


also, what you are doing is not "unusual". I'm sure the geologists and core drillers I worked with in the past had methods of extracting sand and silt samples from a core -- I recall two part sleeves that just separated when you placed the core on the storage tray.

I have some experience setting up ultra clean labs used for cutting up and decontaminating polar ice and sediment cores so presumably some decontamination process will be needed.
This is because the core drill (and in case of the ice cores, kero lube used) cross contaminates the layers on the outside of the core.
Plastic sediment cores are usually just pushed into the sediment but some degree of layer cross contamination occurs on the outsides.
Decontamination usually involves stripping away the outer layers of each core.
In the care of 100 mm diameter cores we used to remove up to 37.5 mm from the outside leaving a 25 mm inner core which we did measurements on.
Isotope measurements of the shaved ice were used to track contaminants right into the inner core dues to cracks in the ice - these sections of core had to be discarded for the most sensitive measurements

At once stage we used SS blades driven by a power drill and a flexy shaft to removed the outer core layers by cutting slices along the core lengths.
We had 11 separate SS blades and used to cycle them through nitric acid cleaning baths cleaning baths.

A special ice core holding "indexing lathe" made of acrylic, teflon, and SS was made to hold a short sections of core while the blade travelled along the length of the core.
The lathe/rig had to operate at -18ºC in an ultra clean lab and so was driven pnuematically for cylinders of ultra clean nitrogen.

The rig was only used with circular blades for a short time before the decontamination methods reverted to using custom made SS chisels (see second photo) to shave small amounts of ice of the core at a time as this was deemed safer and produced less cross contamination. The contamination of the ice by the chisels was tiny but significant and had to be subtracted along with other contamination from the measured results.

DSCN1417ap.jpg
DSCN1344p.jpg

15 years on and a completely different method is now used.
The outer layers of the core are cut away with a BS and the inner half melted vertically on a slotted SiB (bluish) hotplate with holes in the bottom.
This rejects all bar the inner 20 mm section of the core and the liquid water goes direct into analytical instruments for analysis
Ice-Core-Melters.jpg

The lathe went into retirement, then surplus and finally it disposed of last year and I managed to get hold of most of the bits and pieces and still have them. I made my TS OH guard from one of the chunky pieces of acrylic.

We do have to focus on cross contamination, but not to the point of glove boxes, fume hoods etc. We just use a lot of clean gloves, plastic matting, tyvek suits, etc. We also decontaminate everything thoroughly.

When the core is cut (some of them can be opened with mechanical shears) it will ooze out a bit, but not much. It's high in silt and clay content, so it's relatively well consolidated.

I've bought 5 bits which can be used for cutting acrylic. Solid carbide so they shouldn't rust. I've gotten a Festool router with an adjustable fence and a dust collector. My plan is to set the plunge depth such that the bit will project just through the acrylic and not sling mud everywhere. The oozing effect of the sediment has a bit of a delay, so I think that moving the router with a solid feed rate should be more than enough to avoid soaking it in mud. Using the fence should eliminate the problem of the router wobbling, and keep the bit centered. It will still be able to drift, and won't cut a perfectly straight line, but we don't need that.

I think it's going to work... I have faith that I haven't blown it too badly here and it'll all be fine.

I will know Monday... The router came without a fence, so Festool is overnighting one to me and it arrives then.

Cheers,
Luke

Sidenote: Bob, what do you do? In another lifetime I was a glaciologist. I wasn't involved in ice core analysis, and was more on the fluid dynamics side.

Originally Posted by Luke Maddux

Sidenote: Bob, what do you do? In another lifetime I was a glaciologist. I wasn't involved in ice core analysis, and was more on the fluid dynamics side.

I've been retired for 4+ years but in another lifetime I was an academic in a University physics department. The research I was involved in required the use of ultra clean air laboratories (hence my interest in dust) and built a complete 6 x 4 m clean lab back in 1985/6. I did all the plumbing (all plastic), electrics, built the PP and HDPE ducted air filtration/handling/extraction etc from 8 x 4 sheets of plastic and the lab benches were made of plywood and finished with 7 coats of epoxy. It was cheaper to employ me as a uni researcher than to get all the different tradies involved. It was only just possible within a Uni environment to do that back at that time whereas these days it would just not be permitted. I have also been involved with the design and building of 3 other clean labs.

Originally Posted by Luke Maddux

My plan is to set the plunge depth such that the bit will project just through the acrylic and not sling mud everywhere.
Luke

I would set it just short of full depth so that the very thin remaining piece could be cut with a box cutter and avoid all of the mud slinging.

Originally Posted by Bohdan

I would set it just short of full depth so that the very thin remaining piece could be cut with a box cutter and avoid all of the mud slinging.

Agree


I'd also mount the router on a morticing jig -- the type that straddles the piece being morticed.
That way the cutter should stay centered on the core.

Originally Posted by Luke Maddux

I've bought 5 bits which can be used for cutting acrylic. Solid carbide so they shouldn't rust. I've gotten a Festool router with an adjustable fence and a dust collector. My plan is to set the plunge depth such that the bit will project just through the acrylic and not sling mud everywhere. The oozing effect of the sediment has a bit of a delay, so I think that moving the router with a solid feed rate should be more than enough to avoid soaking it in mud. Using the fence should eliminate the problem of the router wobbling, and keep the bit centered. It will still be able to drift, and won't cut a perfectly straight line, but we don't need that.

I think it's going to work...

I will know Monday...

So, did it work , or are you covered in mud?

It worked! It was highly praised by the project manager.

It's a pretty horrific cut, but it gets it done. It is jerky and by no means straight. Lexan is one hell of a material. Nonetheless, none of that matters as long as we can scoop the core.

No mud slinging either. The projection is perfect.

Now to just convince them to give it to me when the job is done...

Originally Posted by Luke Maddux

It worked! It was highly praised by the project manager.

It's a pretty horrific cut, but it gets it done. It is jerky and by no means straight. Lexan is one hell of a material.

Glad it works.

If you want a dead straight line use a negative raked circular saw blade, it cuts Lexan like butter..

Originally Posted by Luke Maddux

It worked! It was highly praised by the project manager.

doesn't get much better than that

Originally Posted by Luke Maddux

Now to just convince them to give it to me when the job is done...

crossing my fingers for you

for future readers, a link to this information on milling plastics was posted on the Metalwork forum
Selecting the Right Plastic Cutting End Mill - In The Loupe - Machinist Blog