Rebuilding the Central of Georgia #408

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kvom
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Re: Rebuilding the Central of Georgia #408

Post by kvom » Wed Jun 24, 2015 6:44 am

I was planning to use 10-24 screws on mine. Any reason I shouldn't stick with 10-32s?

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Re: Rebuilding the Central of Georgia #408

Post by Harold_V » Wed Jun 24, 2015 3:00 pm

Assuming the threads are in steel, the fastener itself should have greater tensile strength when selecting a fine series (in this case, the 10-32), as the minor diameter of the thread is larger than it is with the course series (10-24). However, if the mating thread (the B, or internal thread) is in soft material (aluminum, cast iron), the coarse thread is likely a better choice.

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Fender
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Re: Rebuilding the Central of Georgia #408

Post by Fender » Wed Jun 24, 2015 3:44 pm

Harold,
But isn't this also a function of the length of thread? For example, a threaded hole two or three diameters deep in aluminum or c.i. should not strip out, even with a fine thread screw.
Dan Watson

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Re: Rebuilding the Central of Georgia #408

Post by Harold_V » Thu Jun 25, 2015 1:46 am

Fender wrote:Harold,
But isn't this also a function of the length of thread? For example, a threaded hole two or three diameters deep in aluminum or c.i. should not strip out, even with a fine thread screw.
Correct. If memory serves, a thread (of proper diameter) with 1½ times the diameter in length of engagement should be stronger than the bolt itself. That, of course, isn't true of softer materials, so greater length of engagement is a good idea. However, I think I'd still be inclined to use a coarse thread in cast iron. It's pretty easy to damage fine threads.

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John_S
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Re: Rebuilding the Central of Georgia #408

Post by John_S » Thu Jun 25, 2015 11:48 am

For those curious, the socket head cap screws I'm using (same as on my mogul boiler steam dome lid) are Kerr 10F75KCS 10-32x3/4, with a tensile strength of 180,000lbs/inch.

Got the inner firebox sheets all ready to go and clamped together to test the fit and squareness. Everything looks good so it's almost time to put the electric glue to it. I have to do my welding outside the back of the shop but it's already in the mid-90s with about 834% humidity here ... I think I'll wait until tomorrow morning to go out there and have at it.
408_106.jpg
Inner firebox test fit before welding

Jawn
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Re: Rebuilding the Central of Georgia #408

Post by Jawn » Thu Jun 25, 2015 12:56 pm

John_S wrote:I have to do my welding outside the back of the shop but it's already in the mid-90s with about 834% humidity here ... I think I'll wait until tomorrow morning to go out there and have at it.
Ain't this weather wonderful?

Curious, what sort of welding process is acceptable for boiler work like this?

redneckalbertan
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Re: Rebuilding the Central of Georgia #408

Post by redneckalbertan » Thu Jun 25, 2015 1:32 pm

Jawn wrote:Curious, what sort of welding process is acceptable for boiler work like this?
Stick: 6010 roots 7018 fills and caps. DCRP. If you can get to both sides of a weld, no need for a root. First pass with 7018 grind or gouge to sound metal from the other side then filler up!
TIG: ER70S2 or ER70S6 wire, 2% thoriated electrode (although there is a new one out there that I have no experience with but like what I have read and I can't remember the name if it right now), DCSP

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John_S
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Re: Rebuilding the Central of Georgia #408

Post by John_S » Thu Jun 25, 2015 6:00 pm

redneckalbertan wrote:
Jawn wrote:Curious, what sort of welding process is acceptable for boiler work like this?
Stick: 6010 roots 7018 fills and caps. DCRP. If you can get to both sides of a weld, no need for a root. First pass with 7018 grind or gouge to sound metal from the other side then filler up!
TIG: ER70S2 or ER70S6 wire, 2% thoriated electrode (although there is a new one out there that I have no experience with but like what I have read and I can't remember the name if it right now), DCSP
For all the mild steel stick welds on the boiler I will be using 6011 for root passes and 7018 for cover passes.

I will be doing TIG with 312 filler for the stainless bushings to the mild steel with thoriated (red) tungsten electrodes.

redneckalbertan
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Re: Rebuilding the Central of Georgia #408

Post by redneckalbertan » Thu Jun 25, 2015 7:17 pm

I should have said 6010 or 6011 for the root. 6010 is a DC rod, 6011 is the AC equivalent.

What grade of stainless fittings are you using?

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John_S
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Re: Rebuilding the Central of Georgia #408

Post by John_S » Fri Jun 26, 2015 9:46 am

redneckalbertan wrote:I should have said 6010 or 6011 for the root. 6010 is a DC rod, 6011 is the AC equivalent.

What grade of stainless fittings are you using?
6011 can be run DCEP, which I plan on doing. Did my mogul boiler root passes with that and it worked wonderfully.

All of the stainless bushing and pipe fittings are 304.

Got the firebox tacked together this morning. It's only 10:40am and it's already getting too hot, especially wearing jeans and a long sleeve shirt! As you can see I have it clamped together with hardwood blocks to prevent it from warping out of shape while welding. I'm also doing my tacks in a crisscross pattern to help prevent warping as well. Tack one corner, then tack the opposite one on the other side, then back... like the star pattern you use when tightening wheel lug nuts. It's working well as everything has stayed in place thus far.
408_107.jpg
Tacking the firebox together
That's all for today ... I plan on finishing the exterior welding tomorrow morning. Sorry this next photo is a tad fuzzy.
408_108.jpg
Finished tacking.

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John_S
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Re: Rebuilding the Central of Georgia #408

Post by John_S » Sat Jun 27, 2015 12:20 pm

Finished up the root passes on the outside of the firebox. Time for some Honey-Dos.
408_109.jpg
Root passes done.

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John_S
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Re: Rebuilding the Central of Georgia #408

Post by John_S » Tue Jun 30, 2015 8:26 am

Finished up the inner firebox yesterday. I'm happy with it. Only minor bowing inward of the side sheets, which can be corrected later when I weld the mudring.
408_110.jpg
408_111.jpg

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