Since the thread starter was questioning what bolts to us on Rohn 65G tower
the comment about crushing a tower leg irrelevant.
The original question remains unanswered. Since I have some 65 clone
sections that may be supporting a large dish Im also wondering if Grade 5 or
8 is required. Based on the galvanizing issue Im going to guess that
galvanized Grade 5 is what the manufacturer recommends/provides.
Carl
KM1H
----- Original Message -----
From: "Charette, Douglas" <ChareDo@tulsaschools.org>
To: <TowerTalk@contesting.com>
Sent: Friday, October 19, 2007 11:28 AM
Subject: Re: [TowerTalk] Galvanized grade 8 bolts
> Frank, I have to disagree. The reasons you mention for not using an SAE
> grade 8 fastener for the most part don't make any sense. They do not
> require any special training to "install correctly" beyond the ability
> to use a torque wrench, with the thought in mind that any fastener in
> any application has an appropriate torque. The special methods you
> speak of apply to certain applications only, such as certain automotive
> cylinder heads where a torque is applied and then the fastener is
> further tightened by measuring degrees of rotation. As such, these
> fasteners are only good for a one time use and must be replaced if
> loosened. Same when measuring stretch with a micrometer. Neither is
> the case here, as you aren't going to tighten anything to a point that
> is just short of the material's yield strength. Grade 8 bolts are most
> definitely NOT brittle. This implies that they will shatter. And as a
> mechanic with 40 years experience, I've just never seen that happen. I
> have seen some shear when over torqued, and I've seen some break when
> over torqued...but never shatter. If they do exhibit this type of
> behavior, then the heat treating was done incorrectly in the first
> place. At the typical level of torque used on say R25, you'll collapse
> a tower leg before you damage a grade 8 bolt.
>
> That said, they are totally unnecessary for the task and add needless
> expense. Cheap they are not. A good quality (not hardware store) grade
> 5 galvanized bolt is fine for a tower. The case hardening provides a
> good load bearing surface, and the underlying alloy provides appropriate
> toughness. They still should be installed with a torque wrench in any
> case.
>
> 73,
> Doug, W5GA
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of
> donovanf@starpower.net
> Sent: Friday, October 19, 2007 9:26 AM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Galvanized grade 8 bolts
>
> Jeff,
>
> Please check the head markings on your galvanized Grade 8 bolts.
> If they're actually Grade 8, they'll have 8 radial lines marked on
> the head. The reason I ask is that I've never seen a galvanized high
> strength alloy steel bolt. Grade 8 bolts are typically plated and
> have a gold color.
>
> The ASTM A490 specification for high strength bolts does not allow
> galvanizing because of the high risk of reducing the strength of the
> heat treated steel alloy during the hot dip galvanizing process. SAE
> Grade 8 bolts use the same high strength alloy as Grade 8 but they're
> less expensive (and more common in consumer stores) because the SAE
> specification doesn't require testing.
>
> I understand that some overseas manufacturers do offer mechanically
> galvanized (N O T hot-dip galvanized) high strength steel alloy bolts.
> I suspect they're much more expensive than plated SAE Grade 8 bolts and
> they're probably not readily available in the USA.
>
> The alloy steels used in high strength bolts are brittle and achieve
> their fastening strength only when properly tensioned by
> professionally trained installers with special tools and methods. Its
> very unlikely that high strength bolts actually achieve any benefit in
> amateur installations, and can actually be very hazardous if not
> professionally installed.
>
> My advice: Don't use high strength bolts unless you're a trained and
> experienced professional. In critical applications, use ASTM A325
> bolts which can be safely installed by non-professionals. In less
> critical applications use SAE Grade 5. If you must use high strength
> bolts, obtain the training and equipment to use them safely.
>
> 73
> Frank
> W3LPL
>
> ---- Original message ----
>>Date: Thu, 18 Oct 2007 13:13:18 -0700 (PDT)
>>From: Jeff Walker <k4bp@yahoo.com>
>>Subject: [TowerTalk] Galvanized grade 8 bolts
>>To: towertalk@contesting.com
>>
>>
>>Galvanized grade 8 bolts are available in bulk at a
>>VERY reasonable price from...
>>
>>Gulf Coast Fasteners, Inc.
>>1626 Town Hurst
>>Houston, Texas 77043
>>
>>(713) 464-1555
>>
>>__________________________________________________
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