Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Sacrificial backing material

I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...eat=directlink

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i
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Ignoramus30138 wrote:
I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...eat=directlink

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i


Get a piece of 3/4" MDF - medium density fibercore - looks like brown paper
bags pressed together because that's basically what it is . But it's cheap ,
it's rigid , and it won't hurt your cutters . And you can buy less than a
full sheet at ho-de-po or Blowes .
--
Snag
Learning keeps
you young !


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On 2010-12-17, Snag wrote:
Get a piece of 3/4" MDF - medium density fibercore - looks like brown paper
bags pressed together because that's basically what it is . But it's cheap ,
it's rigid , and it won't hurt your cutters . And you can buy less than a
full sheet at ho-de-po or Blowes .


I thought that it actually is abrasive and also clogs the coolant
pump.

i
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Ignoramus30138 wrote:

On 2010-12-17, Snag wrote:
Get a piece of 3/4" MDF - medium density fibercore - looks like brown paper
bags pressed together because that's basically what it is . But it's cheap ,
it's rigid , and it won't hurt your cutters . And you can buy less than a
full sheet at ho-de-po or Blowes .


I thought that it actually is abrasive and also clogs the coolant
pump.

i


It's not a good idea to use coolant when using a wood / wood product
backer. This is one of the many times that it's best to machine aluminum
dry and just vacuum up the chips and backer dust when it's done.
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Ignoramus30138 fired this volley in
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I thought that it actually is abrasive and also clogs the coolant
pump.


both.

And the statement earlier that "most" woods don't contain much silica is
rife with problems. As wood selections get cheaper, and more and more of
the scrap is salvaged, more bark, root, and knot sections get included in
plywood and press-board products, raising the silica content beyond what
you want on your nice tools.

LLoyd


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On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus30138 fired this volley in
:

I thought that it actually is abrasive and also clogs the coolant
pump.


both.

And the statement earlier that "most" woods don't contain much silica is
rife with problems. As wood selections get cheaper, and more and more of
the scrap is salvaged, more bark, root, and knot sections get included in
plywood and press-board products, raising the silica content beyond what
you want on your nice tools.


Lloyd, do you think that I could use 2x4 and 2x6's for this sort of
purpose, as a backer on my mill, and with coolant?

The wood "chips" would not be so fine as with MDF or some such.

Right?

i
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Ignoramus30138 fired this volley in
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Lloyd, do you think that I could use 2x4 and 2x6's for this sort of
purpose, as a backer on my mill, and with coolant?

The wood "chips" would not be so fine as with MDF or some such.

Right?


Right, and you can, but you have all sorts of "prep" work to do to the
backing that will generate lots of shavings and dust.

Go to a local plastics supply and ask them for some cut-offs and scraps.
Just avoid insolubles like PE,PP,Delrin, or Nylon, because you cannot
glue effectively to them (well, to nylon you can), and you can't dissolve
them off the work if you want to.

The more I think about it, the more PVC and styrene have their
attractions. For small work, you could even "convert" flat-bottomed pipe
caps to work backers.

LLoyd


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On 12/17/2010 02:34 PM, Ignoramus30138 wrote:
I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...eat=directlink

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

Well, it can be. Finely powdered wood can make a big mess in your
coolant system. What I would have done is use a boring process with an
end mill. I have a program that writes the G-code to bore out holes
like that. depending on the size and thickness, I have versions to
either obliterate the entire hole or to just trim around the edge and
then let the slug drop out, then finish the OD. I use this technique
for almost everything. This is not quite as fast as a twist drill, but
if you have to go very easy due to workpiece deflection, then the boring
approach may end up almost as fast.

Jon
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Ignoramus30138 wrote:

On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus30138 fired this volley in
:

I thought that it actually is abrasive and also clogs the coolant
pump.


both.

And the statement earlier that "most" woods don't contain much silica is
rife with problems. As wood selections get cheaper, and more and more of
the scrap is salvaged, more bark, root, and knot sections get included in
plywood and press-board products, raising the silica content beyond what
you want on your nice tools.


Lloyd, do you think that I could use 2x4 and 2x6's for this sort of
purpose, as a backer on my mill, and with coolant?

The wood "chips" would not be so fine as with MDF or some such.

Right?

i


Go down to your local Mal-Wart and get a cheap poly cutting board as
your sacrificial backer.

And remember, you *do not* need coolant for most machining operations in
aluminum.
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"Pete C." fired this volley in news:4d0be94a$0$9804
:

And remember, you *do not* need coolant for most machining operations in
aluminum.


But you need _lubrication_, or you get false edges built up on the tooling.

All the more reason to use a polymer for the backer instead of wood.

LLoyd


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On Fri, 17 Dec 2010 14:34:57 -0600, Ignoramus30138
wrote:

I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...eat=directlink

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i


FWIW, I use AL plate. Used stuff taken off a scrap machine. One plate
will last for hundreds of parts.

Karl

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Ignoramus30138" wrote in message

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.


I've had pretty good luck epoxying (5 minute variety) aluminum to MDF then
applying heat when finished to soften the epoxy and release the aluminum.

I'll clamp up the MDF, and mill it flat, then mill alignment ridges or
pockets if needed before gluing the aluminum in place.


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"Lloyd E. Sponenburgh" wrote:

"Pete C." fired this volley in news:4d0be94a$0$9804
:

And remember, you *do not* need coolant for most machining operations in
aluminum.


But you need _lubrication_, or you get false edges built up on the tooling.


Not if you are using sharp tools and the correct speeds and feeds. You
can also use compressed air to blow the chips out of the way further
reducing the risk of chip welding.


All the more reason to use a polymer for the backer instead of wood.


Either will work, the MDF will be cheaper, though likely to get reused
less before being tossed, so probably a wash price wise.
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On Dec 17, 4:00*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Ignoramus30138 fired this volley om:

I thought that it actually is abrasive and also clogs the coolant
pump.


both.

And the statement earlier that "most" woods don't contain much silica is
rife with problems. *As wood selections get cheaper, and more and more of
the scrap is salvaged, more bark, root, and knot sections get included in
plywood and press-board products, raising the silica content beyond what
you want on your nice tools.

LLoyd


Excellent point.

I have seen significant silica in solid wood...knots and bark injury
can cause sand to be anywhere in a wood product.

TMT
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On Dec 17, 2:34*pm, Ignoramus30138 ignoramus30...@NOSPAM.
30138.invalid wrote:
I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...uTAdxO3bjAhN7B...

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i


Ig...since you do know how to reuse materials, try going to the local
thrift store and get the $1 picture frames with clear panes of
PLASTIC.

Works great for sacrificial backings.

If you buy the frames that use aluminum extrusions, you will have
building stock also.

TMT


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On Fri, 17 Dec 2010 16:19:44 -0800 (PST), the renowned Too_Many_Tools
wrote:

On Dec 17, 2:34*pm, Ignoramus30138 ignoramus30...@NOSPAM.
30138.invalid wrote:
I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...uTAdxO3bjAhN7B...

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i


Ig...since you do know how to reuse materials, try going to the local
thrift store and get the $1 picture frames with clear panes of
PLASTIC.

Works great for sacrificial backings.

If you buy the frames that use aluminum extrusions, you will have
building stock also.

TMT


Cheap dollar store cutting boards provide some useful material too. It
machines quite nicely.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4d0be94a$0$9804
:

And remember, you *do not* need coolant for most machining operations in
aluminum.


But you need _lubrication_, or you get false edges built up on the tooling.

All the more reason to use a polymer for the backer instead of wood.

LLoyd


I have never succeeded machining aluminum without coolant. Broke a few
endmills.

i
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Ignoramus30138 wrote:

On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4d0be94a$0$9804
:

And remember, you *do not* need coolant for most machining operations in
aluminum.


But you need _lubrication_, or you get false edges built up on the tooling.

All the more reason to use a polymer for the backer instead of wood.

LLoyd


I have never succeeded machining aluminum without coolant. Broke a few
endmills.

i


I've never machined aluminum with coolant, and I've machined a lot of
aluminum and never had a problem. If I recall you were running with way
too low a feed rate at the time causing more rubbing than cutting, chip
welding, etc. I use high feed rates and moderately heavy cuts so I get
decent sized chips flying away.
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On 2010-12-18, Pete C. wrote:

Ignoramus30138 wrote:

On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4d0be94a$0$9804
:

And remember, you *do not* need coolant for most machining operations in
aluminum.

But you need _lubrication_, or you get false edges built up on the tooling.

All the more reason to use a polymer for the backer instead of wood.

LLoyd


I have never succeeded machining aluminum without coolant. Broke a few
endmills.

i


I've never machined aluminum with coolant, and I've machined a lot of
aluminum and never had a problem. If I recall you were running with way
too low a feed rate at the time causing more rubbing than cutting, chip
welding, etc. I use high feed rates and moderately heavy cuts so I get
decent sized chips flying away.


Maybe one day I will try it again.

i
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Ignoramus30138 wrote:
On 2010-12-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
"Pete C." fired this volley in news:4d0be94a$0$9804

And remember, you *do not* need coolant for most machining operations in
aluminum.


But you need _lubrication_, or you get false edges built up on the
tooling.

All the more reason to use a polymer for the backer instead of wood.


I have never succeeded machining aluminum without coolant. Broke a few
endmills.

Coolant, or lubricant? They're not necessarily the same, although I'd assume
your coolant has some lubricity.

I've used plain, ol' ordinary lard (Crisco will also work) on aluminum; it
works good and smells good too! ;-)

Cheers!
Rich



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On Fri, 17 Dec 2010 14:34:57 -0600, Ignoramus30138
wrote:

I am drilling this aluminum sheet:

http://picasaweb.google.com/lh/photo...eat=directlink

This is a holder for a (almost complete by 1/64) set od DA collets
that I have in a bag.

Unfortunately, when drilling, it flexes more than I would like. It is
under control but I now realize that I should have used some
sacrificial backing material, or a step drill.

The question is, what material is friendly to the mill. I thought that
wood (plywood) was somehow bad.

thanks

i


MDF


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