I have a metal disk with pins in it (~118mils diameter) that is part of a grinder machine. I believe the disk and pins are both hardened steel since it is used for grinding plastic flakes into powder but I have no idea what kind. I heated the disk to ~1100F for ~2hrs to burn off some resin that got stuck to it that I was grinding. After heating the plate all the pins are all loose. I did not realize that the pins were press fitted into the disk.

My question is, can I reverse the process by reheating. Should I heat the metal plate without the pins in it. Will quenching the plate cause the holes to shrink further ? Any thoughts or ideas would be greatly appreciated

Thanks

Andy

WAG response would be that you need a new part or you'd need to fit slightly
oversize pins in the existing disk, although the hardness of the disk may
have been compromised by the heat soak, and could be annealed now.

Not knowing what the metal alloy(s) are, you should probably get a new
replacement part from the machine maker.

Another possibility is that the pins may have been shrunk-fit into the
disk.. which has little meaning now that the holes are oversize.

Some plastics are abrasive, and HSS pins may exhibit considerable wear if
used to grind some plastics.. also, plastic may be more likely to stick to
HSS.
Carbide pins would likely be brittle (depending upon how far they protrude
from the disk) but more durable/less wear, and less likely to have the
plastic stick to them.

When you say "mils" while talking about dimensions of parts, it's unclear
what sizes you're trying to describe.

Mils are common to film thicknesses.. heavy duty trash bags are 3 mils, or
coatings thicknesses/paint coatings etc.

Mils isn't a shortened term meant to represent mm or millimeters (like
tranny for transmission or the other s/he kind).
Whereas a tranny fitting would generally be referred to as an adapter (or
possibly a dressmaker term).

Millimeters are millimeters or MM/mm, so 118mm is about 1-3/4".

Mils are thousandths-of-an-inch, but 0.118" isn't expressed as 118 mils..
and 0.118" would be smaller than 1/8" in diameter.
Maybe you're referring to the diameter of the pins, but it's not really
clear.. 3mm is 0.1181").

Finally, if you expect to have frequent questions or comments regarding
metalworking, home shop practices or similar topics (all welcome here in the
RCM usenet newsgroup), get a news reader program, or use your email program
with a news subscription or news feed service, instead of posting thru the
"diybanter" or other online/web reader.

--
WB
..........


"asd108b" wrote in message
...

I have a metal disk with pins in it (~118mils diameter) that is part of
a grinder machine. I believe the disk and pins are both hardened steel
since it is used for grinding plastic flakes into powder but I have no
idea what kind. I heated the disk to ~1100F for ~2hrs to burn off some
resin that got stuck to it that I was grinding. After heating the plate
all the pins are all loose. I did not realize that the pins were press
fitted into the disk.

My question is, can I reverse the process by reheating. Should I heat
the metal plate without the pins in it. Will quenching the plate cause
the holes to shrink further ? Any thoughts or ideas would be greatly
appreciated

Thanks

Andy




--
asd108b

Wild_Bill Inscribed thus:

Millimeters are millimeters or MM/mm, so 118mm is about 1-3/4".

Surely you mean 4-3/4"

--
Best Regards:
Baron.

mill == 0.001 inch

How about cleaning off the pins and holes them super glueing them back in

But of course 4-3/4", Marilyn

--
WB
..........


"Baron" wrote in message
...
Wild_Bill Inscribed thus:

Millimeters are millimeters or MM/mm, so 118mm is about 1-3/4".

Surely you mean 4-3/4"

--
Best Regards:
Baron.

Thanks for the replies. I was referring to the pins being 0.118" in
diameter. I guess the term mils (=1/1000th of an inch) is not used
for larger dimensions.

I am getting a quote from the manufacturer for a replacement disk, but
I am guessing it is going to be in the $1000 to $2000 range (german
made machine). The vendor did mention that the pins are press fitted
as they are meant to be replaceable as the pins wear over time

Since I have nothing to lose, I may try just some two part epoxy to
glue the pins onto the disk from the back (the pins stick out the
other end).

I will look into the newsreader suggestion

Andy

Well, you may have at least a couple of options.. and one consideration
would be how much damage will occur if some pins came out while running the
machine.

If making a new disk is within your capabilities (you still haven't stated
if the disk is small or large/how thick or how many pins there are or how
they're arranged), shrink fitting is performed at safe temperatures which
wouldn't affect the hardness of either the disk or pins.
Future replacement of the pins may be more difficult if they're shrunk-fit.
You haven't mentioned how hot the pins may get during operation, which could
be very detrimental to an epoxy product.
Loctite makes compounds that are used for semi-permanent assembly of parts.

As I mentioned in a reply to DoN, you're the only one who can see the part..
If the disk is thin, epoxy is likely to fail.
If there is much heat generated during operation, your options are fewer.
Points or other features on the pins such as different lengths may affect
the assembly method options.

Using slightly larger diameter pins in the original plate/disk may work,
although unpredictable, since the original characteristics of the plate are
unknown.
Fabricating a new plate/pin assembly may be cost effective, but not as
durable as an original replacement part.
New pins wearing down may not be as bad as having them come out and damage
an extruder or other part of the machine.

The size of the holes in the old plate/disk won't be reduced by reheating..
it would take some kind of stamping or swaging process to displace the metal
around the holes, but that would make the metal thinner around the pins.

--
WB
..........


"andrew" wrote in message
...
Thanks for the replies. I was referring to the pins being 0.118" in
diameter. I guess the term mils (=1/1000th of an inch) is not used
for larger dimensions.

I am getting a quote from the manufacturer for a replacement disk, but
I am guessing it is going to be in the $1000 to $2000 range (german
made machine). The vendor did mention that the pins are press fitted
as they are meant to be replaceable as the pins wear over time

Since I have nothing to lose, I may try just some two part epoxy to
glue the pins onto the disk from the back (the pins stick out the
other end).

I will look into the newsreader suggestion

Andy

On Sat, 28 Jan 2012 21:03:07 -0800 (PST), andrew
wrote:

Thanks for the replies. I was referring to the pins being 0.118" in
diameter. I guess the term mils (=1/1000th of an inch) is not used
for larger dimensions.

I am getting a quote from the manufacturer for a replacement disk, but
I am guessing it is going to be in the $1000 to $2000 range (german
made machine). The vendor did mention that the pins are press fitted
as they are meant to be replaceable as the pins wear over time

Since I have nothing to lose, I may try just some two part epoxy to
glue the pins onto the disk from the back (the pins stick out the
other end).

I will look into the newsreader suggestion

Andy
Using epoxy will probably fail. Using Loctite made for cylindrical
fits might work, it needs to be heated to 450 degrees F in order to
make it release. But I wouldn't count on any type of glue. Instead I
would buy a .1245 dia reamer to ream the holes larger and some 1/8
diameter dowell pins and press them in. Dowell pins are available in
the hardened condition (most common), soft, and in stainless steel.
They are ground accurately to size and they are cheap. If the plate is
quite thin, say 1/16 inch, a .1240 dia reamer would be better. Even a
1/8 inch thick plate might be better reamed to .1240. But any thicker
..1245 to .1247 should hold the pins in.
Eric

On 2012-01-27, Wild_Bill wrote:

[ ... ]

When you say "mils" while talking about dimensions of parts, it's unclear
what sizes you're trying to describe.

Mils are common to film thicknesses.. heavy duty trash bags are 3 mils, or
coatings thicknesses/paint coatings etc.

[ ... ]

Mils are thousandths-of-an-inch, but 0.118" isn't expressed as 118 mils..
and 0.118" would be smaller than 1/8" in diameter.
Maybe you're referring to the diameter of the pins, but it's not really
clear.. 3mm is 0.1181").

Why not? The spacing of leads on the old DIP chip packages were
specified as 100 mils (0.100"). It all depends on the field. Some use
mils just as he has apparently used them.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Yep, it depends upon the particular field when mils are commonly used.. and
I mentioned a couple of examples.
I've never heard of feeler gage thicknesses expressed as mils, either.. and
yet they are.

IC pin spacings have commonly been specified in decimal/inch dimensions as
far back as I can remember using them, in the '70s.. not as a component or
board designer, just as catalog descriptions and datasheet specs.
But pin spacings in highly compact dimensions are leaning toward metric
dimensions more recently.

The OP is often the only one who has seen a part, and lots of folks seem to
leave out descriptive details, which then require several exchanges of
questions to get an idea of what the original question was.

Just sayin'

--
WB
..........


"DoN. Nichols" wrote in message
...
On 2012-01-27, Wild_Bill wrote:

[ ... ]

When you say "mils" while talking about dimensions of parts, it's unclear
what sizes you're trying to describe.

Mils are common to film thicknesses.. heavy duty trash bags are 3 mils,
or
coatings thicknesses/paint coatings etc.

[ ... ]

Mils are thousandths-of-an-inch, but 0.118" isn't expressed as 118 mils..
and 0.118" would be smaller than 1/8" in diameter.
Maybe you're referring to the diameter of the pins, but it's not really
clear.. 3mm is 0.1181").

Why not? The spacing of leads on the old DIP chip packages were
specified as 100 mils (0.100"). It all depends on the field. Some use
mils just as he has apparently used them.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---