[GreenKeys] 32/33 print hammer
gil smith
[email protected]
Sun, 24 Aug 2003 14:21:21 -0700
Folks:
A correction to my earlier post. I just dug out a bag of 33 parts, and
found an NOS hammer. It is very soft now. The diameter is pretty darn
close to 0.5", and the outside edge measures about 0.18". However, it
designed to snap around a disc for retention, so the center is only about
0.085" thick. Well, that is the best I can tell, according to my
micrometer sloppily oozing into goo that was once useful rubber.
Unless we find someone with an end mill to burrow a hole into the rubber
(if rubber can be milled at all), we are left with applying a flat sheet
for hammer replacements. Which, as best I can tell, should be about 0.085"
thick.
So I went to pull off the old hammer on the 33, which I thought had
hardened, judging by the cracks around the edge. It was actually soft goo
as well. But I could see, well, feel, the raised disc that the hammer
snaps over, for retention. It is flat on top, so the hammer would glue
onto it directly. I suppose if the glue oozed around the mounting disc, it
would add a bit of lateral retention as well.
Robert Downs seems to know the materials science end of this elastomeric
mystery. If you guys find an appropriate sheet rubber source and adhesive,
I'd be happy to punch them out.
gil
At 01:08 pm 8/24/03, Bob Camp wrote:
>Hi
>
>Half inch diameter sounds easy to hit with fairly simple stuff. I suspect
>that something near 0.2 inch thick is a standard sheet thickness.
>
>Is the original part flat on both sides or is there a retaining bump on the
>back of the part?
>
>My recollection of the original rubber used was that it came fairly close to
>an eraser on the end of a pencil. It was a little softer, but not by a lot.
>Of course that's based on a quick observation 20+ years ago. I may be way
>off ....
>
>The main idea about the punch was to make it quick to run off a bunch of
>them. One person could probably wack out a lifetime supply for everybody on
>the list in a few hours. Postage to distribute them would cost more than the
>material and the time.
>
> Enjoy!
>
> Bob Camp
> KB8TQ
>
>
>----- Original Message -----
>From: "gil smith" <[email protected]>
>To: "Bob Camp" <[email protected]>
>Cc: <[email protected]>
>Sent: Sunday, August 24, 2003 3:47 PM
>Subject: Re: [GreenKeys] 32/33 print hammer
>
>
> > Hi folks:
> >
> > My quick measurement of a 33 hammer shows it to be about 0.5" dia by 0.2"
> > thick.
> >
> > I like Don's idea of using the peel-n-stick bumpers -- I have some 3M
> > bumpers from DigiKey (#SJ5012-0), that measure about 0.5" dia by 0.15"
> > thick. Dunno if slightly thinner is a problem or not. The rubber seems
> > kinda soft -- anyone know what the original rubber was like? The original
> > one in my machine is rather hard with age. Bet this bumper would work
> > though, even if it needs a small shim to make it thicker. The big
>question
> > would be the bumper's adhesive.
> >
> > If someone finds a rubber sheet that is appropriate, you probably don't
> > need to punch it into a nice circle. I'd bet that hacking it to an
>octagon
> > with an xacto knife would suffice. Though I do have a bench punch with a
> > 0.5" die set if anyone wants a bunch made. I have some 3M 467 sheet
> > adhesive that could be applied before punching; then you just peel off
>the
> > paper backing and apply the new hammer pad. 467 is a pretty good
>adhesive,
> > but, as mentioned previously, how it stands up in heat and oil is a good
> > question.
> >
> > Before mounting the bumper, you would want to clean the hammer mounting
> > plate with something like lacquer thinner, to remove all oil.
> >
> > gil
> >
> >
> > At 11:12 am 8/24/03, Bob Camp wrote:
> > >Hi,
> > >
> > >One fairly simple thought:
> > >
> > >Sheet rubber is a common item. You can get all sorts of compositions and
> > >thicknesses fairly easily. Last time I went shopping there were several
> > >local suppliers. They would sell you a couple of square yards of stuff
> > >without any real hassle. The question always is which rubber to use.
>Again
> > >there are zillions of different compositions.
> > >
> > >Once you have the raw material you need a punch to blast out the print
> > >hammers. Last time I looked at one (gulp .... *several* years ago) they
> > >looked like a round disk without any real fancy stuff associated with it.
> > >Don't remember if they had a little nubbin on the back side of them or
>not.
> > >
> > >Even if it's a punch you can't buy at the leather working counter down at
> > >Hobby Lobby a rubber punch is not to hard to make.
> > >
> > >Given the punch and the raw material making a couple hundred imitation
>print
> > >hammer pads shouldn't take more than an hour or two.
> > >
> > >The questions:
> > >
> > >What are the dimensions of a "real" print hammer pad?
> > >
> > >What's the right material to use (need one that's soft enough and holds
>up
> > >to heat and oil) ?
> > >
> > >Given that information the rest *should* be fairly easy.
> > >
> > > Enjoy!
> > >
> > > Bob Camp
> > > KB8TQ
> > >
> > >
> > >
> > >----- Original Message -----
> > >From: <[email protected]>
> > >To: <[email protected]>
> > >Sent: Saturday, August 23, 2003 6:53 PM
> > >Subject: [GreenKeys] print hammer
> > >
> > >
> > > > What i need are suggestions as to what material to use and what type
>glue
> > >to use to make a print hammer for my Model 32. It is my understanding
>that
> > >print hammers are not availiable as they all turned to mush.I no longer
>like
> > >the idea of my model 32 just sitting here idle because of a little round
> > >peice of rubber.Shurly someone out there has solved this problem and got
> > >their machine back into service.Wayne WB0CTE
> > > >
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