[How-To] Help Please. How would you repair this Cracked Cast Iron Lathe Apron (Off a Smithy Granite). Braze or Weld?

[bill70j]

I would appreciate any and all of your thoughts on how to repair the cast iron apron casting on my lathe that I damaged when crashing the machine several years ago. The apron is off a Smithy Granite 1324 3-in-1 machine. The damage has caused the thing to jam up - rendering it completely useless.

Here is the apron before disassembly:


Here is a Front View of the damage.
(The casting is not cracked through in all locations, so it will not "crumble" despite taking some pretty heavy whacks with a dead blow.)


Here is a Top View


Hear is a Rear View



And another Rear View



Right after this happened, I tried to buy the casting alone - but Smithy persuaded me to buy the entire assembly, saying that assembling the existing components into a new casting had been a problem for others in the past. So I bought and installed a new assembly and have been using that ever since. I am repairing this assembly as a spare, so it is a "nothing lost" situation.

I have MIG and oxy-acetylene, but no TIG. Thanks ahead of time!


Key Words: bronze braze cast iron repair cracked cast iron casting lathe apron repair Smithy apron carriage how to repair cast iron casting

 

[graham-xrf]

OK - we have a whole lot of experts here. I am not exactly one of them, in the sense that I do not yet have the hands-on skill, but I do know some from watching others, and what I have learned in this forum.

Before even we get into whether the part is repairable, or would yield to a repair fix by cutting away the damaged stuff, and bolting/welding in a new support section for the pinions, just on the level of metals, consider what would weld that stuff. Using nickel based welding rods/fillers are the norm for stitching bust castings as cast iron, or cast semi-steel. The latter is the very common tough, stable casting material used for machines.

The other thing I know is that there is a huge plus to heating up the whole part before welding into prepared vees, slots, etc. I have seen it done (from a safe distance) on a full size steam engine cylinder, where they drilled a hole at the end of the crack, ground out a V trench, with a root at the bottom, then heated up the while thing to dull red, and proceeded to weld with huge rods like as used for ship decks. All that, of course, is not for your situation, but for me, the lesson was that cast iron welds just fine if it is clean, and heated up, and you use nickel.

From the pictures, the cantelever pinion bushing support took a huge force, with a torque twist, and this bent the face outwards. If you put a steel rule edge up to it, you may find the distortion goes well beyond the ends of the cracks, and might affect other shafts.

I would say that part of the casting is pretty much trashed. You could maybe cut away all the wrecked casting, then fit in a new chunk of metal, not necessarily of cast metal, not necessarily the same internal shape. Instead of bushing shoulder supports, just use a real thick chunk of metal.
The way the repair plate gets attached is also variable. Welded along it's edge, or even some arrangement of bolted on, whatever. If you do weld in a steel chunk, then a milling and drilling operation could restore all the shaft supports and bushings.

Please take these as possible half-assed suggestions. I don't really know the detail of the thing. I do know that in metal like that, nearly anything can be made like new. It is true that the time and labour to do it very likely makes the cost beyond worthwhile. That is - unless another is simply not available, or you enjoy fixing it up, and it will work in your kit .

[The thought occurs that drilling the crack ends through, then using a mini-grinder to open all the cracks, and a little "persuasion" to knock the face straight again, might have some mileage. Welding it up, including the bushings holes, then re-drilling, might yield a repair nearly like new! ]

 

[sdelivery]

Nope, sell it or the contents for parts

 

[macardoso]

Personally I'd scrap it, especially since you have a working replacement.

I have no welding experience but have seen others turn out good repairs with TIG brazing. The temperatures are low enough to not melt the iron and reduce the stresses of welding. Perhaps not as strong as the original material, but plenty strong nontheless.

Another option is Lock-N-Stitch cast iron repair system. Very time consuming but a proper way to repair damaged castings.

Metal Stitching & Thread Repair Inserts. - Turlock , CA - LOCK-N-STITCH, Inc

LOCK-N-STITCH Inc. provides cast iron repair services such as metal stitching, emergency thread repair, fusion welding, & machining services for industries in power generation, gas compression, shipping, and pumps.

www.locknstitch.com

 

[benmychree]

I agree with the above post, save or sell the undamaged parts and scrap the casting, it is not worth the trouble to (try) to repair, especially if you do not have the skills to attempt to perform it.

 

[Abowie]

Successfully welding cast iron is well nigh impossible.

Brazing it together might work but it would have to be done so as to maintain the alignment of mounting holes for the parts which on something so small would be very difficult.

That is too small for stitching etc. and stitching is an incredibly skilled process.

I think the best place for it is the bin.

 

[Tozguy]

Are you happy with the new assembly from Smitty? What are the chances of damaging the new one?

If the cracked apron just gives you an opportunity to try your hand at welding cast iron then I understand but you might never need to install it and never find out how good the repair is.

 

[Flyinfool]

I can believe that thing was binding up in use, that casting is not just cracked, it is bent A LOT.

To make a repair you will need to completely disassemble it. Then you will need to grind deep V grooves just short of being all the way thru the casting. Since the crack goes into shaft holes you will not need to drill stop holes. Once you have that done you will need to straighten the casting to get everything back where it belongs. Once you have it bent back to straight. Then you can use your OXY with a big rose bud tip to heat the casting up to just below red hot and then braze the cracks full. you will then need to clean up the bores that the shafts are in to get the proper fit back.

I have recently in another post heard of MIG brazing witch should have the same or similar benefits of TIG brazing, but I know very little about it, just throwing it out there.

Because the casting is bent and cracked there is a high possibility that you can do all this repair and some of those shafts might still be out of alignment due to other parts of the casting that are bent that you can not see and still cause binding. There could also be shafts that are bent and or bearings damaged. This is most likely why they recommended replacing the assembly.

On the other hand, the attempted fix is not real expensive to do, so it may be worthwhile just for the experience and learning opportunity for when you really need to have to fix something. OR even a good excuse to buy some new tools.........

 

[Ulma Doctor]

put a fork in the apron, it is DONE.
as mentioned a couple times above, salvage what you can from the old assembly and move on

 

[Nutfarmer]

Welding up the casting is not a problem . The casting will warp enough that trying to line up all the shaft bores will not be worth it. All the shaft bores will probably have to be rebored and bushed. Could be a good learning project,but if you have a new one to replace it I would find a fun project like a steam engine .