Just Line Bored My Swing Tower

After lots of reading, talking on forums, and Youtube videos, I've just line bored for the very first time and all went well.

I did the kingpin knuckle (swing tower) from my 1.8 tonne excavator. Now two guys are giving me the doom and gloom saying the swing tower might be made of ductile iron and welding on it has stuffed it. It's always good to hear this stuff AFTER you've read a million posts and asked a million questions, and never seen a line boring video where the bearing holders were not attached by welding.

So does anyone know what the likelihood is that my swing tower is made of ductile iron. I assumed it was a high strength cast steel.

Shouldn't matter too much I've stuffed it. I'm just about at the stage of looking for a job anyway, sick of this tight access industry (never enough work) and always being in the workshop when I'm not digging.

If you have welded and machined it,its cast steel,not ductile iron. If you had welded ductile iron you would not cut it,the weld goes glass hard.
A lot of them are ductile iron though and its easy to check.
Try drilling a small hole in it. If the swarf has graphite dust and small shavings its cast iron.
Get a bit of mild steel and touch it with a grinder. Then grind the tower.Steel will have yellow sparks with sparklers. Cast/ductile will generally have dull red sparks.
Put a small spot of weld on with a stick welder. Try it with a file. If its iron it will be hard.

Thanks very much Ray.

I'll do those tests when I go back in the workshop.

I'm a beginner to this line boring and don't have any bore welding gear which would be the only way to weld up these small difficult to access bores. Instead I'll be sleeving them with 20MnV6 steel. Doesn't really matter if the sleeves don't last as long as a welded and bored out repair, I can easily put new sleeves in again.

I'm starting to think it is ductile iron based on the cuttings which are about 3 mm across (see the pictures). My HSS bit does not have any chip breakers ground in. The swing tower photo shows the welding a bit. Do you reckon I've made of peice of scrap steel out of it





Keith.

The chips look like cast but you said you got it done so what is the worry??

Yes,chips look like cast but there is nothing wrong with what you have done.When you take you mounting plates of it would pay to blend in where ever the weld has pulled out parent metal.
What crush/interferance are you machining the bearings to?

Hi Mike,

like I said in my first post, theirs a couple of guys on a machining forum saying I've stuffed the swing tower by welding on it. I'm not knowledgeable enough to agree or disagree, but I'm hoping I haven't done any significant harm and it was just their way of congratulating me on my very first line boring job. I'll tell you what though, it's been a better way to find out about this ductile iron than if I later do a job for someone, put stress points on their gear by welding on it, then attempt to machine out bores that I've built up with a bore welder, and the weld is glass hard. I'm gradually working my way to producing money with my little workshop, so I can almost look at this as a blessing in disguise.

Hi Ray,

and thanks again.

Where the weld ties into the parent metal it is hard as you explained. I have no idea how cast iron bores can be built up with weld and then line bored if the weld goes so hard. That something else that will bug me until I find out. Maybe there's lots of pre-heat and post heat involved to prevent hardening or something like that. I know one thing, I'll be testing for steel type next time LOL.

I still have to look in my Machinerys Handbook to work out what should be the best press fit size. I know that when press fitting the sleeve can actually "crush" a little and reduce the ID so I'll have to consider that too when I make them.

The bushes themselves are stock standard Cat parts so that's just a press out, press in job.

Keith.

I consider myself extremely lucky now, because I was advised at least two times NOT to sleeve the bores (supposed to brinell and/or come loose), and instead weld them up and bore to pin size. If I had access to a bore welder I would have done just that then I would have been in real deep s**t when I tried to machine them out.

I've also just been told that with ductile iron, sleeving is an "authorised" repair, so my guess is ductile iron bores NEVER get built up with weld, only sleeved.

I also still can't understand why sleeving would not be as good, if they were done similar to the bushes - hardened & ground and press fit. The bushes never come loose or brinell so why would sleeves.

Keith.

Keith,when I do those I clamp them down to a bench and then mount my machine to the bench. That saves welding onto the cast.The other concern is that welding to the cast is not strong and you risk your machine coming adrift when you least want it.
If you weld onto that stuff with any iron based consumable its going to go hard. I use occasionally a Nickel/copper mig wire which is very good and also very expensive so you have to pick your jobs with it. On your job sleeving or putting a bearing in is good.

Took the finishing cut about an hour ago with a brand new TSA C6 grade bit. Finish came out quite satisfactory, but the starting bore is about 2/100 mm larger than the last bore so the carbide has either worn that much over the boring length or blunted slightly and not dug in as easy (well that's 1/100mm radially or the reduction in toolbit length).

I see what you mean about the lack of strength in the weld, they just about fell off when I started taking everything apart.

OK, quite a few lessons learned and I know quite a bit more now than I did two days ago, thanks mainly to people like yourself.

Thank you again Ray.

I bet making these swing towers out of this material is too make them more difficult to repair so the operators either buy a new one or trade their machine in. Cat won't sell any parts for motors, pumps, track drives, etc. I've nearly been put out of business by their spare part tactics. When I needed the pump/motor shafts for my final drives they only sold complete units, $8000 for the pair. I was lucky enough to find a specialist that could supply internal parts for OEM track drives and I got away with $800 in parts and installed them myself. Needed a fancy seal for the pump but ended up paying $1100 because the gits wouldn't supply it.

Keith.