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