machine a weld

[pockets]

I have a series of corner /angle welds that I would like tomachine into nice looking fillets. My guess is that a ball end mill would be the weapon of choice, but do I use 2flute or 4flute? HSS makes the most sense, to me, as this is an old Index mill and is too slow for carbide.

Thanks for any guidance.

Greg B.

[CraigS]

I am guessing the welds are in steel. Not yet used a ball cutter but I posted a message about using them and based on the replys chatter is going to be the problem. Welds are already hard to machine because of the hard inclusions. I would think the best bet would be grinding. If the unit will be painted you could just smooth out the weld with some epoxy putty or body filler like I did on the pylon I build for my mill.

Craig

[awake]

I have a series of corner /angle welds that I would like tomachine into nice looking fillets. My guess is that a ball end mill would be the weapon of choice, but do I use 2flute or 4flute? HSS makes the most sense, to me, as this is an old Index mill and is too slow for carbide.

Thanks for any guidance.

Greg B.

Greg, several thoughts:

1) The process and/or rod/filler will make a significant difference in the machinability of the welds. On mild steel, SMAW welding with 7018 and good technique will produce machinable welds. Welding with 6010 or 6011 will produce bit-destroying hardness.

2) Good welds are never ground or machined; they are admired for their natural beauty. My welds, on the other hand, sometimes get ground. (They get machined only when the weldment is part of a part that is to be machined.)

3) Related to the above, a good weld has a slightly convex surface -- i.e., it bumps out -- rather than a concave surface (such as would be produce by milling with a ball nose end mill). IOW, milling or grounding will compromise strength. If strength is not an issue, then have at it.

4) Accessing the weld with an endmill and/or holding the weldment securely may be a challenge!

[pockets]

Craig and Awake,
Thanks for the responses.

Craig,
The welds are mig welded with, IIRC, 7018 wire. I have machined other areas of these weldments and the welds milled just fine. These are parts of a model and the reason for machining the welds is to reduce the bulk and bring the appearance closer to that of castings

Greg B.

[Al_Messer]

If you have access to a Shaper, this would be a piece of cake with a HSS tool bit ground to the desired radius.

[stevec]

I'm with awake ( I said "with awake " not that I am awake) "2) Good welds are never ground or machined; they are admired for their natural beauty. My welds, on the other hand, sometimes get ground.".
Of course, a pic or two of the weldment would be a help.

[pockets]

I don't have any post weld pics, but here are the assemblies pre-weld...http://forums.railfan.net/forums.cgi?bo ... ;start=160

The bars are 1/2" X 1" HR and the gussets are 1/4" HR. All joints are welded to create fillet material. I need to determine if a 2flute or a 4flute ball end mill would be best.

Normally, I would agree that a nice weld is a thing of beauty. However, for this project it is just part of the raw stock.

Thanks,
Greg B.

[awake]

Craig and Awake,
Thanks for the responses.

Craig,
The welds are mig welded with, IIRC, 7018 wire. I have machined other areas of these weldments and the welds milled just fine. These are parts of a model and the reason for machining the welds is to reduce the bulk and bring the appearance closer to that of castings

Greg B.

Sounds like you're in good shape for the machining. I do not have a mig, but seems like I've read somewhere that most (all??) mig produces low-hydrogen welds. Since 7018 rod is a low-hydrogen rod for stick welding, maybe there is a pattern here. (By the way, I think this only applies to MIG, not to flux-core wire welding -- but again, I have no personal experience, so I'll stop talking! )

[awake]

I don't have any post weld pics, but here are the assemblies pre-weld...http://forums.railfan.net/forums.cgi?bo ... ;start=160

The bars are 1/2" X 1" HR and the gussets are 1/4" HR. All joints are welded to create fillet material. I need to determine if a 2flute or a 4flute ball end mill would be best.

Normally, I would agree that a nice weld is a thing of beauty. However, for this project it is just part of the raw stock.

Thanks,
Greg B.

Greg, I've got one other thought to offer, now that I've looked at the pictures of what you're welding. In the pictures, it looks like the material is 1/4 to 3/8" thick -- is that right? Or am I being misled by a closeup?

If it is 1/4" thick or more, here's something you might experiment with on some scrap: you might try welding it too hot, and see if that gives you more of a "natural" fillet. I do not know that this will actually work, especially with MIG (see my previous post!), but I do know that I have produced concave fillets when running too hot with 6013 stick.

Feel free to skip the explanation, but here's how it happened -- when I was first learning to weld, I had a 110 volt arc welder, an exercise in frustration for the most part. I then bought an ancient 220 volt Marquette arc welder for the grand sum of $25, and the difference was incredible -- suddenly I had power to spare! At last, I thought, I can finally achieve proper penetration. I did some sample welds that to my eye looked beautiful -- nice concave fillets -- and proudly showed them to some experienced welders, who promptly told me I was running way too hot, and that a proper weld should be convex, not concave.

[Harold_V]

It is generally accepted that a four flute end mill is a better choice for machining steel (there are exceptions)----which would likely be right in this instance. It will provide a somewhat more smooth cutting action because there's always a tooth in the cut. I'd recommend conventional milling with the possible exception of a climb mill finishing cut---assuming your mill has the required rigidity.

Being a weldment, it's unlikely that you'll be able to achieve a full cleanup without removing some of the parent metal,

Harold

[pockets]

Thank you, Harold. I don't believe ridgidity will be an issue, with my 1967 Index mill.

Thanks again,
Greg B.

[Harold_V]

Thank you, Harold. I don't believe ridgidity will be an issue, with my 1967 Index mill.

A great deal depends on the condition of the machine (even a heavy machine). There will be a lot of area in contact with the cutter, especially with a ball end mill. If your ways have wear and the gib is loose as a result, coupled with backlash, climb milling can yield a lot of problems, including scrapping the piece and breaking the end mill. Just a heads-up---climb milling is wonderful, but can be troublesome.

Harold