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

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 ---

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 Sun, 29 Jan 2012 17:06:28 +0000 (UTC), wrote:

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

I haven't followed this whole thread, so this might have been
mentioned, but...

There are two reasons those pins might have loosened in the first
place, and one of them may still be a problem. First, it's possible,
if the plate constrained the growth of the holes upon heating, that
the pins simply compressed against the holes and displaced some metal.
When it all cooled, the pins could be loose.

The other thing may sound strange, but, if I followed the situation
accurately, is the more likely reason, IMO. Martensite -- the hardened
state of the steel -- is less dense than the softened state (say,
ferrite, to keep it simple) Pins in their hardened state are slightly
larger in diameter than they are when they're annealed. The amount is
very slight, but in something like this, they could be noticeably
looser when the metal is soft. Again, it depends on how much the plate
was hardened in the first place and how much its shape constrains the
enlargement or shrinkage of the holes.

So you have to be careful when measuring and fitting the pins to do so
after you've hardened them to their final state. If you fit them soft,
and then harden them, you have a problem.

This is an old issue that used to come up in the making of drill jigs.
In fact, it's the reason that Dick Moore invented the jig grinder,
after having had success with the jig borer. You could get everything
right with the borer, harden the tool, and then discover that the
drill bushings wouldn't fit in their holes, and that the holes weren't
in exactly the right dimensional relationship anymore.

The solution was to finish-grind the tool after hardening. It's pretty
much the same situation -- again, if I read the early posts correctly.

--
Ed Huntress

On Sun, 29 Jan 2012 17:06:28 +0000 (UTC), wrote:

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

Very good post!!


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

Thanks for all the suggestions. I wanted to let you know where I am

Firstly: Here is picture of the machine almost identical to the one I
have; http://www.aaronequipment.com/usedeq...pz-ii-43905001
If you look through the pictures, you can see that there are two
plates with pins - one fixed and one rotating. It was the pins on the
rotating plate that I ruined by heating to 600C. The pins go through
the rotating plate

Well, I initially tried Loctite in the gaps and epoxy on the back side
- but the loctite did not cure and I did not have all the pins at
exactly the same height, so it was scraping on the fixed plate and on
the back side when rotating (the gaps are just a few mm's on both
sides of the plate). So I burnt everything off in the oven - again
and used just 2 part epoxy very liberally on the back side - all over
the pins and plate. The back side does not see the chips that are
grinding

So far after about 10-20 runs at~5000rpm, it seems to be holding - all
the pins are still tight. SInce the gaps are so tight, there is no
danger of the pins falling out, so I thought I can take the chance
with this approach for now. I am not really a machinist to be able
to rework the part and I do not know enough metallurgy to know what
kind of heat treatment would work so this seemed to be the only
approach for me

Thanks again

Andy

On Wed, 29 Feb 2012 14:22:37 -0800 (PST), andrew
wrote:

Thanks for all the suggestions. I wanted to let you know where I am

Firstly: Here is picture of the machine almost identical to the one I
have; http://www.aaronequipment.com/usedeq...pz-ii-43905001
If you look through the pictures, you can see that there are two
plates with pins - one fixed and one rotating. It was the pins on the
rotating plate that I ruined by heating to 600C. The pins go through
the rotating plate

Well, I initially tried Loctite in the gaps and epoxy on the back side
- but the loctite did not cure and I did not have all the pins at
exactly the same height, so it was scraping on the fixed plate and on
the back side when rotating (the gaps are just a few mm's on both
sides of the plate). So I burnt everything off in the oven - again
and used just 2 part epoxy very liberally on the back side - all over
the pins and plate. The back side does not see the chips that are
grinding

So far after about 10-20 runs at~5000rpm, it seems to be holding - all
the pins are still tight. SInce the gaps are so tight, there is no
danger of the pins falling out, so I thought I can take the chance
with this approach for now. I am not really a machinist to be able
to rework the part and I do not know enough metallurgy to know what
kind of heat treatment would work so this seemed to be the only
approach for me

Thanks again

Andy
Greetings Andy,
I'm surprised that the epoxy is holding so well. And that the Loctite
didn't cure. Loctite is an anaerobic curing chemical compound so maybe
there was too much exposure to air for it to cure. I would still try
to press 1/8 diameter pins into the plate after reaming out to .124 if
the epoxy does fail. Apparently though the epoxy has a high enough
compression strength and sticks well enough to take the strain. Good
for you for trying your solution and reporting your success here.
Nothing beats the empirical testing of your ideas, especially advice
from folks like me who aren't holding your part in their hands.
Cheers,
Eric

wrote in message
...
Greetings Andy,
I'm surprised that the epoxy is holding so well. And that the
Loctite
didn't cure. Loctite is an anaerobic curing chemical compound so
maybe
there was too much exposure to air for it to cure. ...
Eric

http://forums.1911forum.com/showthread.php?t=148176

jsw

"Jim Wilkins" fired this volley in news:jimcs3$gev$1
@dont-email.me:

http://forums.1911forum.com/showthread.php?t=148176

I disagree with that. I think it depends upon the particular version
you're using.

I use 747 "removable", and it cures on both aluminum AND stainless (and in
combination).

It even cures in contact with plastics and aluminum, although it takes a
few hours.

Lloyd

On Wed, 29 Feb 2012 14:22:37 -0800 (PST), andrew
wrote:

Thanks for all the suggestions. I wanted to let you know where I am

Firstly: Here is picture of the machine almost identical to the one I
have; http://www.aaronequipment.com/usedeq...pz-ii-43905001
If you look through the pictures, you can see that there are two
plates with pins - one fixed and one rotating. It was the pins on the
rotating plate that I ruined by heating to 600C. The pins go through
the rotating plate

Well, I initially tried Loctite in the gaps and epoxy on the back side
- but the loctite did not cure and I did not have all the pins at
exactly the same height, so it was scraping on the fixed plate and on
the back side when rotating (the gaps are just a few mm's on both
sides of the plate). So I burnt everything off in the oven - again
and used just 2 part epoxy very liberally on the back side - all over
the pins and plate. The back side does not see the chips that are
grinding

So far after about 10-20 runs at~5000rpm, it seems to be holding - all
the pins are still tight. SInce the gaps are so tight, there is no
danger of the pins falling out, so I thought I can take the chance
with this approach for now. I am not really a machinist to be able
to rework the part and I do not know enough metallurgy to know what
kind of heat treatment would work so this seemed to be the only
approach for me

Thanks again

Andy
Greetings again Andy,
After thinking about Loctite I remembered that whenever I used it with
stainless steel assembly I always used a primer because otherwise the
Loctite would cure very slowly or not at all. Maybe that's why it
didn't work for you.
Eric

On Wed, 29 Feb 2012 17:42:01 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Jim Wilkins" fired this volley in news:jimcs3$gev$1
:

http://forums.1911forum.com/showthread.php?t=148176

I disagree with that. I think it depends upon the particular version
you're using.

I use 747 "removable", and it cures on both aluminum AND stainless (and in
combination).

It even cures in contact with plastics and aluminum, although it takes a
few hours.

Lloyd

Loctite uses several different adhesives for their various products,
but the original thread-locking and related products are
anaerobic-cure acrylic adhesive. It does its intended job very well,
but for the record, its shear strength and compression strength are a
fraction of the strength of good epoxy.

However, there's a lot more to it than the bulk strength and ideal
bonding strength of the adhesive itself. Epoxy can be tricky in terms
of the actual adhesive bond, and the stronger it is, the more
vulnerable it is to peel and cleavage failure.

Acrylic works better on surfaces that are less than perfectly clean.
Epoxy needs near-perfect cleanliness unless it's formulated to work on
less-clean surfaces.

One of the most interesting examples of the latter is the bead-type
thread-locking epoxies used in industrical production. The resin and
the hardener are each encapsulated in tiny, sealed beads. You mix the
two types of beads together, as a coarse, dry powder, before use and
then they're applied to the threads you want to lock, using a
temporary adhesive (sometimes just starch and water) to hold the beads
onto the threads. When the threads are engaged, the beads break and
the epoxy begins to cure. It's an epoxy formulation that seems to work
well even on oily surfaces. But they're not trying for really strong
bonds, just the kind you get with acrylic Loctite thread-locker.

--
Ed Huntress

I think the reason the loctite did not cure is because I did not have
an air tight seal between the pins and plate. I'm keeping my fingers
crossed on the epoxy (3M DP-100 two part expoy is what I had in hand
and used)

On Thu, 1 Mar 2012 10:00:24 -0800 (PST), andrew
wrote:

I think the reason the loctite did not cure is because I did not have
an air tight seal between the pins and plate. I'm keeping my fingers
crossed on the epoxy (3M DP-100 two part expoy is what I had in hand
and used)

Well, good luck. If I remember the description of your job, it only
requires shear strength. DP100 should be Ok for that. It's made for
use on a wide variety of materials so it's probably somewhat flexible
-- generally a good thing. Like most fast-cure epoxies, it's not
particularly strong or water-resistant. But it's probably all you
need.

'Hope it holds.

--
Ed Huntress

I use 747 "removable", and it cures on both aluminum AND stainless
(and in combination).


BTW... I have NO idea where that number came from...(duh!)

It's #242 removable! blush!

LLoyd

"Lloyd E. Sponenburgh" wrote:

I use 747 "removable", and it cures on both aluminum AND stainless
(and in combination).


BTW... I have NO idea where that number came from...(duh!)

It's #242 removable! blush!


It was a typo, plane & simple. ;-)


--
You can't have a sense of humor, if you have no sense.