fixing pin holes in cast iron?

metalmagpie · Jul 12, 2021

I had a cast iron part welded and after machining it has a lot of pin holes. Of course, I could fill them with Devcon but then the part would be speckled with black dots. I'm told it is common to drill out holes then ream them tapered and affix tapered cast iron pins with Loctite. Those pins are not too spendy for one or two but they come in boxes of 100. I'm not sure I should spend another $100 on something I don't know about.

What do you think?

metalmagpie

Cyclotronguy · Jul 12, 2021

Plugging on structural parts can be dodgy, as you've just added a stress riser point from drilling.

Back in the Day wieh I was buying a lot of machines out of So Cal, you had to be careful. The unscrupulous would hide defiects in cast iron with lead solder.

If the pieces were a bit dusty and light not so good, you might not catch it; first time around.

atomarc · Jul 12, 2021

You might try going to an automotive machine shop in your area. They plug holes and cracks in cast iron heads with threaded fasteners...which I believe are cast iron as well. The fasteners are threaded into tapped holes, snap off, then are finished to be flush with the surface. If all that's accurate, and that process fits your application, they may sell you a few plugs. Just a thought!

Stuart

TomBoctou · Jul 12, 2021

I've occasionally had porosity problems when welding old oil-soaked cast iron car or motorcycle parts. The first cause I've identified is that I'm a hack welder. The second cause is that oil soaks into some cast iron. I've taken to baking the parts over 500F for at least an hour after I think the whole part has gotten up to temperature. I sometimes find burnt oil spots on the surface of parts that started off clean enough to eat off of. Sometimes I still get porosity, so I grind out most of the weld and redo. I've tried filling the pores with silver but I don't think that's ever worked very well.

There are epoxies, Devcon included, with metal powder in them, they might give a better color match if the problem is purely cosmetic.

metalmagpie · Jul 12, 2021

tom_boctou said:
I've occasionally had porosity problems when welding old oil-soaked cast iron car or motorcycle parts. The first cause I've identified is that I'm a hack welder. The second cause is that oil soaks into some cast iron. I've taken to baking the parts over 500F for at least an hour after I think the whole part has gotten up to temperature. I sometimes find burnt oil spots on the surface of parts that started off clean enough to eat off of. Sometimes I still get porosity, so I grind out most of the weld and redo. I've tried filling the pores with silver but I don't think that's ever worked very well.

There are epoxies, Devcon included, with metal powder in them, they might give a better color match if the problem is purely cosmetic.

The guy who welded it for me offered to reweld it. And he told me that a lot of the problem was in the nature of the iron cast into my part. He already lost money on the job because it took over six hours to weld and used up an inordinate amount of acetylene and oxygen and cast iron rod. I don't want to pay him again and I don't want him to go farther in the hole. So that's why I ruled out rewelding.

I went to a commercial machine shop in South Seattle once. They advised me to fill holes big or small in machined surfaces with iron-bearing Devcon. They showed me where they'd done that on their machine. The patch was black. I have cosmetic issues with black speckling as I mentioned above.

metalmagpie

Andy FitzGibbon · Jul 12, 2021

JB Weld is pretty close to the color of cast iron. I used it to fill some drill holes in a milling machine vise, and it's tolerable.

Sent from my SM-G950U using Tapatalk

metalmagpie · Jul 12, 2021

atomarc said:
You might try going to an automotive machine shop in your area. They plug holes and cracks in cast iron heads with threaded fasteners...which I believe are cast iron as well. Yhey may sell you a few plugs.

Seattle used to have many automotive machine shops. Now I don't know of any. If you have one in Eureka you are lucky. Actually, I could buy a few pins from my welder, but I don't want to drive an hour each way.

For really small holes, say 1/16" diameter 1/16" deep, I may just try solder. I've had problems before getting solder to stick to iron. I've put a blob of solder into a divot before, let it cool, then turn it upside down and let it fall out into my hand. Then I superglued it back in. That was to help balance the rotor of a crappy drill press motor. It never did come out.

Maybe I'll just live with it.

metalmagpie

kustomizingkid · Jul 12, 2021

I would run over the weld with silicone bronze with a tig.

Rob F. · Jul 12, 2021

kustomizingkid said:
I would run over the weld with silicone bronze with a tig.

And have it color match?

thermite · Jul 12, 2021

kustomizingkid said:
I would run over the weld with silicone bronze with a tig.

.. then die-grinder clean it up, "air-pencil" abrasive blast, electrotreat.. and freakin plate it, Parkerize it, cera-coat it.. or JF PAINT it.

Peter Carl Fabergé might have had other ideas but he also had the BUDGET to indulge them.

WTF is this critter expected to BE for a Day Job, anyway?

Surely not a life-sized statue of "Iron Feliks" - Feliks Edmundovich Dzerzhinsky?

Poor bugger probably had poxy skin, anyway.

kustomizingkid · Jul 12, 2021

Rob F. said:
And have it color match?

Kintsugi - Wikipedia

enginebill · Jul 12, 2021

Brazing or metal stitching would have been a better repair, rather than welding.

mjr6550 · Jul 12, 2021

Can you make some pins out of cast iron welding rod? Maybe a slight press fit.

metalmagpie · Jul 12, 2021

I can see I'm not doing a great job describing the situation. Here is my part after I cleaned it before it was welded:

As you can see, there was way more than one weld. Here it is after machining:

Way mo betta but still .. pinholes! Note: you can see color mismatching all over the place because the cast iron rod material looks different than the base casting. Also, although it looks wavy, it's very flat.

metalmagpie

CalG · Jul 12, 2021

Paint it!

Rust-o-leum rusty metal primer.

Never look back!

It's a freaking press drill table!

Jim Christie · Jul 12, 2021

Considering what you had to start with I think that the welding came out remarkably well .
I have only welded a little cast Iron but to avoid all the porosity I think you may have had to have taken a cut across the face of the table with a lathe before welding to expose some fresh metal around the holes and perhaps drilled most of the divots a little deeper again to get rid of the kind of hard skin that tends to form over time on cast iron .
Taking .025 or maybe .050" off the face to begin with would have perhaps eliminated a lot of the smaller divots right from the start without unduly weakening the table in my opinion.
I'm not a metallurgist or an engineer so I don't know the science behind this but the oil and other impurities in bedded in the iron over time could have reacted to form bubbles within the new added material in the welding process.
Maybe someone else can enlighten us.
I might also have tried to bore out a recess around the centre hole about 1/2" deep out to within a 1/4" of the slots and made a cast iron patch insert to either weld in or attach with screws. to eliminate a lot of filling .
Perhaps Instead of welding I might have looked for a used lathe face plate of a similar size in good condition and modified the hub to adapt it to the drill press table base
True it is not an historically correct match for the machine but might have made the machine just as useful with considerably less grief.

1yesca · Jul 12, 2021

wow now that was art work . its a lot of work but it you had a chunk of cast iron and the lathe time you could have made a new one but that's a lot of work . and the real sad thing is we have no foundry's that a hobbyist could afford but that's what the likes of Benz did when he started off . i have repaired things like that by capping and machining but you may or may not be past that point now but that would have been the way i would have done it by first bead blasting then a face cut then find the cap material to use be it iron , steel , brass or aluminum but it sounds like iron is the only thing for you so next i would devcon the cap to the base filling all the void's clamp and install a few holding screws on the bottom then after things set up start machining the slots the hole and the od and face now there will be a thine parting line on the od but that could be fixed with some paint and pin stripping or two or three groves on the od or if you just what to work with what you have how about some iron dust powder and clear glue and fill the pits with that

thermite · Jul 12, 2021

CalG said:
It's a freaking press drill table!

It had been at one time.

And then it was not.

NOW?

It is the most useless waste of welding rod and skilled labour East of the Kalifornickyah State Capitol.

Yah just don't dooo this s**t. It ain't remotely sane.

It is akin to putting a coupla hundred blow-out tire patches on an ignorant 7-Eleven condom, then fussing over Bondo and colour-match.

Yah slab a new top on, over. Buy a stock round disk. Arrives already Blanchard ground if you want that, too

Oversize it a skosh. Now you have a clamping ledge.

Make a new table from scratch. Cast or milled from solid. Or turn from a recycled railway wheel. Mine car size? Even a freakin' MANHOLE cover!

Or re-purpose a(ny) old abandoned large-lathe faceplate seeking a few more years of life.

atomarc · Jul 12, 2021

Well Mr.Magpie, kudos to you for even considering repairing that table. It must have been some heirloom or a drill press that was very special to you. I'm afraid I would have relinquished it to the scrap bin, but I'm not a very sentimental soul.

Stuart

CalG · Jul 12, 2021

Cast iron comes in all sizes. I have a couple of spent lapping plates that could have served as useful overlays.

But,,, hey, It's a free country. do what you will.

fixing pin holes in cast iron?

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