Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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DE
 
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Default Repair Question




I'm working yet again on my aging fleet of farm equipment and have
a few metalworking questions for the group.

The machine is a 60's vintage OMC mower conditioner and the
parts are of the sickle drive area. Specifically a couple of 7/8"
grade 8 bolts that have wear on them. Maybe 1/32 deep X 1"
long on one side. I want to build up with arc welding and turn down
on lathe for a precision fit on bearing. Any reason not
to do this? What rod will give max wear and still be machinable?
7018?
Is the HAZ zone a issue on *8 bolts if welded? I suppose spray arc
would be best but not an options for me. Durability is desireable.
It will get new bearings.

I replaced these bolts maybe 20 years ago and can't complain
about the service , just enjoy utilizing the shop and usually can
improve upon the factory design in the process.. I still have the
origional bolts to play with. The bolt/bearing fit is not real
precise to begin with, needs to be dissasembled regularly for
servicing the cutters.

This is a recipocating drive and get hammered @600 strokes/min. I
know I should just replace em but would rather spend the money on shop
tooling of course.....

Interested in any thoughts...

DE

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RoyJ
 
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Grade 8 bolts are listed as "Medium Carbon Alloy Steel, Quenched and
Tempered" with a proof load of 120,000psi and a minimum tensile of
150,000psi. Welding them up with a 70kspi weld rod does not sound like
the best approach.

http://www.americanfastener.com/tech...ings_steel.asp

DE wrote:



I'm working yet again on my aging fleet of farm equipment and have
a few metalworking questions for the group.

The machine is a 60's vintage OMC mower conditioner and the
parts are of the sickle drive area. Specifically a couple of 7/8"
grade 8 bolts that have wear on them. Maybe 1/32 deep X 1"
long on one side. I want to build up with arc welding and turn down
on lathe for a precision fit on bearing. Any reason not
to do this? What rod will give max wear and still be machinable?
7018?
Is the HAZ zone a issue on *8 bolts if welded? I suppose spray arc
would be best but not an options for me. Durability is desireable.
It will get new bearings.

I replaced these bolts maybe 20 years ago and can't complain
about the service , just enjoy utilizing the shop and usually can
improve upon the factory design in the process.. I still have the
origional bolts to play with. The bolt/bearing fit is not real
precise to begin with, needs to be dissasembled regularly for
servicing the cutters.

This is a recipocating drive and get hammered @600 strokes/min. I
know I should just replace em but would rather spend the money on shop
tooling of course.....

Interested in any thoughts...

DE

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Harold and Susan Vordos
 
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"DE" wrote in message
...
snip-----

Interested in any thoughts...

DE



Bad idea. Only under very controlled conditions should one weld on heat
treated items. What are the risks if you have a failure? If none, give
it a go, but I think you'll find it's a false economy. Anything you save in
material you'll spend in labor tearing it down more frequently. You'll
either anneal the bolts by welding on them, or create fracture zones so they
fail if they are still heat treated when you're finished. Being carbon
steel, I think they'll be annealed instead, so you'll have lost all the
advantages of grade 8 bolts, and introduced stress areas.

It will be interesting to hear how this goes.

Harold


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Robert Swinney
 
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Harold knows exactly how to cut through the BS, doesn't he?

Harold, Harold - he'll true you true
If he don't know it,
Nobody do.

Bob Swinney

"Harold and Susan Vordos" wrote in message
...

"DE" wrote in message
...
snip-----

Interested in any thoughts...

DE



Bad idea. Only under very controlled conditions should one weld on heat
treated items. What are the risks if you have a failure? If none,
give
it a go, but I think you'll find it's a false economy. Anything you save
in
material you'll spend in labor tearing it down more frequently. You'll
either anneal the bolts by welding on them, or create fracture zones so
they
fail if they are still heat treated when you're finished. Being carbon
steel, I think they'll be annealed instead, so you'll have lost all the
advantages of grade 8 bolts, and introduced stress areas.

It will be interesting to hear how this goes.

Harold




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Nick Müller
 
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DE wrote:

I replaced these bolts maybe 20 years ago and can't complain
about the service , just enjoy utilizing the shop and usually can
improve upon the factory design in the process..


As others said, don't weld!

But if you are seeking for new shop equipment that solves the job:
Get a "metal sprayer". It is basicaly a OA torch with a (gravity
operated) spray gun like feeder. This feeder puts some metal powder into
the flame's blast where the metal melts and is blasted onto your
surface. You get quite a big selection of powder to use. Among them is
wear resistant bronce.
The process is quite simple, so you might also be able to build one by
yourself. Also, it doesn't heat up the base material too much. After
spraying the metal on, you can use your lathe to get the part back to
size.


Nick
--
Motormodelle / Engine Models:
http://www.motor-manufaktur.de
Ellwe 2FB * VTM 87 * DLM-S3a * cubic
more to come ...


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DE
 
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On Thu, 25 Aug 2005 11:28:35 -0700, "Harold and Susan Vordos"
wrote:


"DE" wrote in message
.. .
snip-----

Interested in any thoughts...

DE



Bad idea. Only under very controlled conditions should one weld on heat
treated items. What are the risks if you have a failure? If none, give
it a go, but I think you'll find it's a false economy. Anything you save in
material you'll spend in labor tearing it down more frequently. You'll
either anneal the bolts by welding on them, or create fracture zones so they
fail if they are still heat treated when you're finished. Being carbon
steel, I think they'll be annealed instead, so you'll have lost all the
advantages of grade 8 bolts, and introduced stress areas.

It will be interesting to hear how this goes.

Harold

After posting I did a search and found bolts online for much
less than the local guy. Story over.

But said machine has a rod end bearing holder that need some
attention.
The stresses on the insert bearing are rated at around
1400 lbs dynamic and half that static. So the 7/8" grade
8 bolt is way over that. The grade 8 bolt must be for wear
purposes.

The bearing holder insert is a
self centering type bearing . Have a bunch that I picked up
new surpluss. The holder is a Fafnir proprietary item @ $120. I
use 4. Only one is loose presently and it looks like a forged piece
with a 7/8 14 male threaded end. Looks like one of these but
is fitted with different type bearing

http://www.qbcbearings.com/RFQ/defau.../B610P168.html

Maybe drill/tap a setscrew/jamnut
to hold bearing tighter?

The failure risk is of non injury type only money....
I can hear when things are coming apart and can get shut down
before total failure.

The machine has some design shortcomings that I manage to find
workarounds and I enjoy the challange of keeping it running.
I paid $350 for it back in 74 and it paid for it self the first couple
of day I ran it...It is stout as hell and could go another 50 years
easy the way I run it.

Tnks for the input

DE

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carl mciver
 
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"DE" wrote in message
...
SNIP|

| I replaced these bolts maybe 20 years ago and can't complain
| about the service , just enjoy utilizing the shop and usually can
| improve upon the factory design in the process.. I still have the
| origional bolts to play with. The bolt/bearing fit is not real
| precise to begin with, needs to be dissasembled regularly for
| servicing the cutters.
|
| This is a recipocating drive and get hammered @600 strokes/min. I
| know I should just replace em but would rather spend the money on shop
| tooling of course.....
|
| Interested in any thoughts...
|
| DE

I don't quite understand the exact application, but I'll throw this out.
If the fit is loose, then it will beat itself up and wear out. The hole
slop is the reason. The more it ages the faster it wears.
How possible is it to bush the holes the bolts fit in, all in order to
make it a much tighter hole, if not downright virginal? I've seen high
stress joints with double and triple bushings or something like that (forgot
the title) where a small fastener is there simply to hold it all together.
A wear bushing of high carbon steel exists in the joint to provide the
bearing surface, and a second bushing inside snugly fit provides the shear
strength. Then a much smaller bolt with special washers or flanges on each
end simply keeps them from sliding out.
In this case I'm thinking that bushing each part that the bolts join
individually, with very tightly fit hardened bushings. Pressed in, that is.
Inside that put a full length bushing of equally hard material as the outer
bushings. Then inside bolt fits snugly and keeps the wear bushing together
while it itself provides the shear strength. This makes the best
application of the strengths of each material, and the tight fit keeps
things from banging themselves apart.

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JohnM
 
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I think I'd buy a couple of new bolts..

John
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DE
 
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I don't quite understand the exact application, but I'll throw this out.
If the fit is loose, then it will beat itself up and wear out. The hole
slop is the reason. The more it ages the faster it wears.
How possible is it to bush the holes the bolts fit in, all in order to
make it a much tighter hole, if not downright virginal? I've seen high
stress joints with double and triple bushings or something like that (forgot
the title) where a small fastener is there simply to hold it all together.
A wear bushing of high carbon steel exists in the joint to provide the
bearing surface, and a second bushing inside snugly fit provides the shear
strength. Then a much smaller bolt with special washers or flanges on each
end simply keeps them from sliding out.
In this case I'm thinking that bushing each part that the bolts join
individually, with very tightly fit hardened bushings. Pressed in, that is.
Inside that put a full length bushing of equally hard material as the outer
bushings. Then inside bolt fits snugly and keeps the wear bushing together
while it itself provides the shear strength. This makes the best
application of the strengths of each material, and the tight fit keeps
things from banging themselves apart.



I've been thinking exactly what you describe. High speed
recipocating movement tends to tear itself apart. When I refurbish
that drive it sounds like a sewing machine, but after some wear is
starts to chatter and the wear accelerates. The unit is built around
weldments, not real precise. I'm thinking along the lines of using
locking sleeves that lock the inner race to the shaft. Or somehow
make the bolt into an expanding mandrel sort of a thing.

Newer drives that solve this problem are expensive by several orders
of magnitude.

DE

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