Milling thin materials
Chas
capabilities and characteristics of lathes for small scale (2mm railway)
model making, and received excellent guidance. At the end of that thread the
topic got on to milling machines, and as it was already quite large, I have
started a new one to ask similar questions.
So, materials at small scale will often be quite thin. 5 thou to 40 thou
(0.12mm to 1mm) brass would be quite common. There's probably little need
for a milling machine for very thin material, and if I get a mill it would
most probably really be for thicker stuff, but anyway I am intrigued to
understand what is realistic on the sort of mill that I might get - around
50Kg weight or less (important to me), and probably �500 or less. I wonder
if I would ever use the mill on these sort of materials.
What is the thinnest material I can realistically expect to mill?
It may seem impossible, but I know even less about milling than about
turning. But I suppose the operations to consider are edge-milling a shape
on thin sheet, and surface milling thinner areas. I guess there may be
techniques for handling thinner materials like laminating with something
thicker?
To get slightly off topic before we've even started, Dave Littlewood, in the
Turning Small Diameters thread, said:
>BTW, and back to your original question, I think you would find a
>milling machine about as much use as a lathe for modelling work. Be sure
>to get one which retains position as you move the head or knee - many of
>the smaller oriental types have a round column with no register, so if
>you move the head you lose position
Mills in my size range seem not to have a knee at all - which I assume is
the component that moves vertically on the column and supports the milling
table. The table just rests on the base, and all the Z-axis movement is
achieved from the milling head movement. Any mill I would consider would
have a square column. The mill I have looked at most is the Sieg X2,
basically because that's the one covered in depth on the excellent mini
lathe site that is my main source of info (minilathe.com).
But I don't really understand your point. I assume you are talking about
maintaining X-Y position after Z-axis head movements - unclamping a head on
a round column would allow the head to rotate and lose position? But even
the little Sieg X0 type micro mills, with a round column, use some sort of
racked arrangement for Z-axis movement that I assume retains X-Y position? I
must be getting the wrong end of the stick, as usual.
Chas
David Littlewood
<c_new...@compuserve.com> writes
>In a separate thread, Turning Small Diameters, I asked about the
>capabilities and characteristics of lathes for small scale (2mm railway)
>model making, and received excellent guidance. At the end of that thread the
>topic got on to milling machines, and as it was already quite large, I have
>started a new one to ask similar questions.
>
>So, materials at small scale will often be quite thin. 5 thou to 40 thou
>(0.12mm to 1mm) brass would be quite common. There's probably little need
>for a milling machine for very thin material, and if I get a mill it would
>most probably really be for thicker stuff, but anyway I am intrigued to
>understand what is realistic on the sort of mill that I might get - around
>50Kg weight or less (important to me), and probably �500 or less. I wonder
>if I would ever use the mill on these sort of materials.
>
>What is the thinnest material I can realistically expect to mill?
I don't know the answer to this. I don't think I have ever gone below
about 1/16". If I had to profile something thinner I would fix it to a
sacrificial block (probably with screws and glue) or (for really thin
stuff) clamp between two blocks. There must be some kind of limit beyond
which the material will bend or tear without such measures. Probably for
very thin material, etching is more suitable, especially for fluting
rods etc. Hand filing is also an option...
>
>It may seem impossible, but I know even less about milling than about
>turning. But I suppose the operations to consider are edge-milling a shape
>on thin sheet, and surface milling thinner areas. I guess there may be
>techniques for handling thinner materials like laminating with something
>thicker?
>
>
>To get slightly off topic before we've even started, Dave Littlewood, in the
>Turning Small Diameters thread, said:
>
>>BTW, and back to your original question, I think you would find a
>>milling machine about as much use as a lathe for modelling work. Be sure
>>to get one which retains position as you move the head or knee - many of
>>the smaller oriental types have a round column with no register, so if
>>you move the head you lose position
>
>Mills in my size range seem not to have a knee at all - which I assume is
>the component that moves vertically on the column and supports the milling
>table. The table just rests on the base, and all the Z-axis movement is
>achieved from the milling head movement.
This is pretty well universal for small mills; the knee type is found on
larger machines, I only mentioned them for completeness (not always the
best thing for clarity!).
> Any mill I would consider would
>have a square column. The mill I have looked at most is the Sieg X2,
>basically because that's the one covered in depth on the excellent mini
>lathe site that is my main source of info (minilathe.com).
>
>But I don't really understand your point. I assume you are talking about
>maintaining X-Y position after Z-axis head movements - unclamping a head on
>a round column would allow the head to rotate and lose position?
Yes.
> But even
>the little Sieg X0 type micro mills, with a round column, use some sort of
>racked arrangement for Z-axis movement that I assume retains X-Y position? I
>must be getting the wrong end of the stick, as usual.
>
The racks are not always fixed in position or precise enough for the
job. A square/rectangular column is best, though a dedicated keystrip on
a round column is OK. My Emco FB2 uses one of these and holds position
very well.
The Sieg X0 is arguably not a real mill, it's a little drill with very
limited milling facilities. A useful mill should have (1) a fine down
feed by leadscrew as well as a handle-fed quill, (2) some kind of taper
in the spindle for holding tooling (a drill chuck will emphatically not
do for milling), (3) a decent X-Y table with good graduated handwheels,
(4) a decent speed range (some don't go low enough - something like 50 -
2000 rpm would be ideal).
A mill with a quill downfeed is ideal for precision drilling and tapping
as well as milling. In fact, with DRO and stub drills, it is probably
the best thing you could reasonable have for putting holes in *exactly*
the right place. I have a drilling machine, but since I acquired the
mill, the drill only gets used for woodwork.
I would guess my mill gets used more than either of my 2 lathes,
probably about as much as the two added together. This obviously depends
on the type of work you do.
Where are you based?
David
--
David Littlewood
Cliff Coggin
"Chas" <c_new...@compuserve.com> wrote in message
news:ULdLm.8844$9o1....@newsfe23.ams2...
> But I don't really understand your point. I assume you are talking about
> maintaining X-Y position after Z-axis head movements - unclamping a head
> on a round column would allow the head to rotate and lose position? But
> even the little Sieg X0 type micro mills, with a round column, use some
> sort of racked arrangement for Z-axis movement that I assume retains X-Y
> position? I must be getting the wrong end of the stick, as usual.
>
> Chas
Unfortunately no. The X0 head swivels the column round as soon as the tool
encounters a significant side load, no matter how tightly the column nut is
done up. The head will also rotate about the column if you loosen the clamp
bolt to raise it.
Cliff Coggin.
Richard Edwards
wrote:
IMHO the simplest way to create "thin bits" is to start off with
thicker bits and stick (cyanoacrylate) or solder them to a much
thicker block to hold them for machining. The "Thick" block is
sacrificial but reusable after removing the part and skimming. The odd
hole here and there is no problem. The odd block of brass bought from
your local scrapyard is perfect for this. Square up first to ensure
all faces true.
With regard to machinery based on your size requirements I would
suggest an X1 or X2. I have an X2 but am looking to change to a bigger
machine, however for your requirements it would suffice IMHO.
The size of the machine makes it simple and cheap to add a DRO. I have
a YADRO with chinese scales and it really works very well. The main
problem with the X2 is the crappy Z axis control, however with a DRO
it is simple to drive low then raise to the required position thus
ensuring that the head is "sitting" on the rack. This and ALWAYS
clamping the Z make the unit well capable of your requirements. The
use of the YADRO or any DRO means that you are not bothered if the
base machine is "Metric" or "Imperial" either are now available with
the DRO.
A belt drive is definitely preferable to the standard gear drive.
(Noise)
Richard
Chas
Thanks
> IMHO the simplest way to create "thin bits" is to start off with
> thicker bits and stick (cyanoacrylate) or solder them to a much
> thicker block to hold them for machining. The "Thick" block is
> sacrificial but reusable after removing the part and skimming. The odd
> hole here and there is no problem. The odd block of brass bought from
> your local scrapyard is perfect for this. Square up first to ensure
> all faces true.
Right, I figured maybe something like this. So this might be a way of
milling thin areas (say 20 thou) into, say, a 40 thou sheet?
How about edge milling? This may be a daft way to do it, but would it be
possible to layer 2 sheets of say 40 thou, and mill e.g. loco frames?
I guess with something sacrificial under them, drilling wouldn't be a
problem, but I really have no idea about the edges.
Which raises a specific question which doesn't really matter - do you think
a mill could edge mill PCB?
Obviously it isn't essential to use a mill for these things - I'm just
trying to gauge what use a mill might be for actual model components.
> With regard to machinery based on your size requirements I would
> suggest an X1 or X2. I have an X2 but am looking to change to a bigger
> machine, however for your requirements it would suffice IMHO.
> The size of the machine makes it simple and cheap to add a DRO. I have
> a YADRO with chinese scales and it really works very well. The main
> problem with the X2 is the crappy Z axis control, however with a DRO
> it is simple to drive low then raise to the required position thus
> ensuring that the head is "sitting" on the rack. This and ALWAYS
> clamping the Z make the unit well capable of your requirements. The
> use of the YADRO or any DRO means that you are not bothered if the
> base machine is "Metric" or "Imperial" either are now available with
> the DRO.
> A belt drive is definitely preferable to the standard gear drive.
> (Noise)
OK, thats taken on board. There are so many accessories and conversions,
that it's hard to know which are really worth while. I have read up wherever
I can on the web about the Z-axis backlash and the consensus there seems to
be what you say - it cannot be eliminated but working in one direction only
allows repeatably precise work.
mick
> possible to layer 2 sheets of say 40 thou, and mill e.g. loco frames?
> I guess with something sacrificial under them, drilling wouldn't be a
> problem, but I really have no idea about the edges.
Chas,
I have been away for a while, so just chatching up.
Edge milling thin sheet is easy. I do 25mm sq 0.05mm thick aluminium
foil with 1.6mm holes 3mm in from each corner on a regular basis, 50 at
a time. You need a 30mm sq mild steel plate about 6mm thick, 0.05mm
brass sheet on that then the 0.05m foil, brass again, then foil and so
on. Top that off with another 30mm sq mild steel plate. Clamp that lot
on the milling table, mill two edges to size, clamp over those two
edges, then remove the original two clamps. Mill the second edges to
size then drill the holes as far and into the bottom plate without
hitting the machine table.
--
mick