[TheForge] Delrin hammer guides?

Mon Apr 7 22:09:00 2003

Actually in my haste I forgot to list the materials I prefer as bearing
guides, delrin is one, also nylatron, which is impregnated with oil, so no
grease or oil is ever required.  both of these materials do well in a high
abrasive variable temperature environment.

----- Original Message -----
From: "gblacksmith" <[email protected]>
To: <[email protected]>
Sent: Monday, April 07, 2003 9:56 AM
Subject: [TheForge] Delrin hammer guides?

> All hands:  Could you use Delrin (acetal) in this application?
>
>                                         Grant
> ----- Original Message -----
> From: "Tom Troszak" <[email protected]>
> To: <[email protected]>
> Sent: Monday, April 07, 2003 5:40 AM
> Subject: [TheForge] Re: UHMW hammer guides
>
>
> > Message: 4
> >     Date: Sun, 06 Apr 2003 21:59:29 -0700
> >     From: Ian <[email protected]>
> >     To: TheForge <[email protected]>
> >     Subject: [TheForge] Air Hammers
> >     Reply-To: [email protected]
> >
> >     Instead of using brass bearings for the hammer and slider, has
anyone
> > used
> >     UHMW ...
> >
> > Dear Ian,
> >
> > I have made dozens of power hammers using UHMW for guides.  The most
> > important thing is that the steel side has to be smooth at lease a 60
> > microinch finish or better.  I have built some hammers that strike
> > 30,000,000 blows per year, and the brass guides had to be replaced every
> > three or four months as the brass needs constant oiling, and most guys
oil
> > about once a day. The good thing about brass guides is that even after
> > 100,000,000 blows, the rams still looked like new.  When the brass
guides
> > were replaced with UHMW, there was no appreciable wear on the UHMW after
> > even six months.  However, in a solid fuel shop, (coal or coke fires),
or
> a
> > place where you do a lot of grinding, microscopic particles of grit get
> > "bedded" in the plastic forming a "lapping tool" which actually eats the
> > steel. there does not seem to be a good cure for this, but the grooves
in
> > the steel do not seem to impair the performance, they just look "bad".
> >
> > Brass guides can be tightened up to a very "crisp" alignment with only a
> few
> > thousanths play and still slide well, UHMW guides always feel a little
> gummy
> > by comparison. You have to make a fairly tight fit, almost pinching to
get
> > rid of the "wobble" but the UHMW is so slippery that it works well. The
> UHMW
> > has virtually no structural strength at all, so in any application it
> needs
> > to be "backed up" structurally some way. UHMW is very spooky stuff. An
> > unsupported bar will deform from it's own weight, yet it is virtually
> > indestructible in many applications, but rough surfaces will erode it
> fairly
> > quickly.
> >
> > Another plastic that I have used successfully for hammer guides is
> > oil-filled nylon, also called Vecton (and other names I'm sure)  It is
> olive
> > green in color and is structurally much stiffer and tougher than UHMW.
I
> > have used it in fully automatic applications where no lubrication is
> > allowed. It is not usable for food grade applications, however. You just
> > "prime' it with a little swipe of light oil as you assemble the machine
> and
> > then it runs for years with no further oil.  The steel side needs to be
> > smooth, as with UHMW.  Believe it or not, regular nylon works pretty
well
> > even without constant lubrication, but I would not recommend it for high
> > speed applications.  I discovered this by accident when a supplier
> > accidently send plain nylon instead of the oil-filled stuff, the hammer
> ran
> > great anyway.  It is more expensive than brass, but very cool stuff.
The
> > caution about dirt applies here as well. It is not as slippery as the
> UHMW,
> > but perhaps a little more slippery than bare brass.
> >
> > I hope this is useful.
> >
> > Tom Troszak
> >
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