Ok here is the problem, I have a friend that needs to have a broken piece on a cast iron treadle for a vintage sewing machine welded up. I know that it is an O/T item but its very valuable and needs to be done right, and I would feel better knowing a HAMBer did the work because it will be done right. I would do it myself but it is several thousand miles from me and we dont want the chance of it being broken during the shipping process for me to fix it. The young lady is in the Boston area and if anyone can fix it and make it look good then I need to talk to you. This is a German piece (Pfaff) from the teens or tweenties and it is in a spot that has a lot of meat to work with. Ill include a photo of it so you guys can see what your working with. And if you can be easy on the finish around the welded area it would be great.
Hello 51, regarding cast iron repairs. The thing with welding cast iron is as the weld is made the different rates of expansion and then contraction encountered as the weld cools will actually cause cracking at the repaired area. This problem is caused by the brittle properties of cast iron. This is not a problem in forged or other malleable steel such as angle, beams, channels, etc. This can be controlled somewhat with preheating and then gradual cooling while maintaining a post heat with a torch or other heat methods. This is a tricky process and someone with a considerable amount of experience would be most helpful. As far as being easy on the finish of the piece regarding paint or other coatings, the surface at the weld must be very clean to achieve a quality repair. There are cast iron rods made just for such repairs. I have also had good results with brazing rods made of brass. If the damage was caused by a strike or bump or such thing it will be more likely to be durable as it will not be stressed as it would if it failed due to strenuous use such as a lever or foot pedal. Your friend might try contacting professional weld shops that do ornamental iron repairs. Much of the really old iron railings, handrails, gates and things similar were made of cast iron. Also my brothers at Iron workers local 7 Boston 617-268-4777 may be able to recommend just such a shop. Good luck, MickeyC. from the bayou
I'm far from an expert with OA welding but I successfully brazed some cast iron parts of my lathe that I broke. It was easy and worked really well. I know this doesn't help your friend but it does provide another option Pete
mickeyc is right about the importance of pre/post heat for a proper welded repair. But for a vintage sewing machine, that is realistically just an ornament, it would likely be possible to get a "pretty good" repair strength wise, and very good astheticly by TIG welding. I've done it myself on an antique stove. It makes a terrible mess of your electrode, but works none the less.
Mickey, thanks for the number! I am a retired union guy myself and have welded everything from cast iron to titanium and everything in between. Cast is a fun metal to weld but the old German stuff was made of really high quality metal and it welds like a dream. But this treadle will be used ever so often so it needs to be fixed so it wont come back apart. I will give them a call and see what I can come up with. Thanks a million!!
Brazing with brass is the only succesful way I have ever seen it done. Doesn't mean it's the only way though. Used to work with some old die makers that grew up blacksmiths and that's the only way they would attack it.
Just get someone with a Hen-Rob torch to weld it. They work so good that i bought one. I used the Hen-rob to build up a tab onto my SBC exhaust manifold 14 years ago, ground it down drilled it, tapped it and its still good
I've had good luck using my Lincoln mig sp-135 with steel wire and argon; just preheat it with a torch, weld carefully and cool it down slow, place a towel over the weld to keep it warm. has worked for me!! Good luck gaspumpchas "the man had me, Toad....."
First of all, if you are gas welding the 2 parts, 30degree bevel on 4 sides, use a fire brick to perform the job, space the 2 parts 1/16" apart on fire brick, preheat with torch flame with a small "feather" at tip (2") when both parts reach a dull red, reduce feather to 1", briefly heat cast iron rod & dip into can of flux (brazing type), dab rod coated flux into beveled parts while maintaining heat until rod & both parts start to melt together gradually----Then, build up the amount of filled rod to desired height, making sure you have enough to grind back down to original surface.---Then let cool a minute or so, turn part over on fire brick & reheat to dull red again, & repeat procedure---When finished, let cool to touch & grind to desired surface, OK? Now, if you are going to arc weld, use Eutetic cast iron rod, either 3/32 or 1/8, depending on the size of project & thickness!---Again, bevel,space, pre-heat, set welder at correct heat, build up weld, repeat other side, cool to touch, & grind. For wire welding, bevel, space, pre-heat, set machine, weld both sides, cool to touch, & grind----------OK?------------Don
I had a motor out of a truck that was hit so hard that the motor mount boss area broke out. I used nickel rod, dc arc, slight preheat, bevel, and drilled holes at the end of cracks. Flowed in like you were spreading bondo, and ran for years. This was in the 70's when I was a teenager, and I'm sure there are better ways to do it since then.. But it worked surprisingly well, and I ended up with a free small block for my 34 pickup.
Kind of what I was thinking too-I'm not an expert by any means, but the welding shop I used to work at has repaired cast iron by gentle pre heat, and welded up with nickle rod.
You've gotten several options, and depending on the size (relative mass) of the part, you need to make a decision. It definately needs to be preheated to a minimum of 225 degrees. This is to remove any moisture from the casting. Using fire-brick or floor-dry to support the pieces during this process is essential. The fire-brick won't wick-out the heat from the casting. Having the casting cool without protection can lead to cracking of the part. Kitty-litter/floor-dry is also a really big advantage to maintaining heat, controling heat-loss. The advantage to using floor-dry is you can form hollows to support the pieces better than just the surface of a flat brick. Also, post welding heat loss is easily maintained by just covering the welded part with additional preheated floor-dry. Allow the part to remain buried in the floor-dry over night for normalization of the casting. I have and use an old electric stove to heat a metal box of floor-dry to 400 degrees as a heated bed to lay the cast parts on/in. I then most often use silicon-bronze rod with my TIG machine to weld cast-iron. It flows beautifully, and is applied at less than the temperature used to melt the cast-iron. Joint prep before welding is as needed, and should include some if not all of the following: sandblasting, wirebrushing, grinding a bevel as needed and careful positioning before preheating. That's my experience Dan Stevens dba, Steelsmith
It can be done with a TIG and the proper pre and post heat. I've got a set of double hump chevy heads with the exhaust cross overs blocked off with plates welded into the head. Wonderful bead, laid down by the guy who builds my race engines. Very sharp guy. I doubt that I could do it, but it can be done.
It would be helpfull to see what needs repair. If it is circle, square, triangle or rectange shape piece it will pull when cooled and break. Unless the whole piece is preheated & kept hot while welding. Then cool the whole piece slowly. Like cover with floor-dri & let cool over night. Or clean the broken area, grind to a v shape, then preheat in a stove or barrel. Take it out & weld it & put it back in the hot barrel, let the fire go out & cool slowly. Or build a little oven with brick & what ever, heat with rose bud torch, carcoal, wood what ever. If the piece is a straight bar shape it doesn't need all the extra preheat slow cool stuff. It will pull, bend a little bit not crack. The weld process is irelavent, brass braze, stick nickle, cast rod, tig whatever you have is ok. I like brass cheap easy fast, you don't have to peen the weld to relive stress & strong enough for your application. And brass will give a little so it don't snap as easy. My 10cents---Gene
Not only do need to preheat and post-heat, but you need to stress relieve it as you weld. Their are several ways to do this, some are better than others. A needle gun works well.--TV
If he uses a cast iron rod, he would need to use high heat flux, not brazing flux. Brazing flux is for use with.... brazing rod.
The Jalopy Journal
