Ajax AJ8 horizontal Mill - cracked casting

I've now picked up the machine and the crack doesn't go right through to the switch gear aperture. It has however opened up more than it first appeared in the sellers original photos.

Would you try to pull it shut before bonding the plate on? I assume that may result in trouble as a result of putting stress back into It?

The seller had alread stop drilled the closed end. They have also screwed through the crack at the open end from under the foot in an upward/inboard diagonal (effectively pulling the crack closed with the screw in tension). The diameter of the scew/bolt is only about 4mm though, so on its own isn't going to do much.

Edited By Mark Davison 1 on 30/03/2018 07:53:13

First thing I would do is make a square plate to connect the four mounting holes to stop the crack moving.I know this will lift the column by the thicknessof the plate. Then stitch it using a backing plate.

Mark , my suggestion would be to grind a sizeable area flat around the diagonally running crack, make a substantial steel plate to bridge it and drill , tap and bolt in place. Use a piece of heavy steel angle , 10mm perhaps, which has its lower surface ground out in such a way that it sits neatly on top of the foot bolting boss and makes contact along the sloping upper surface of the foot with the 'vertical' flange flat against the previously bolted steel plate. Bolt this in place also then securely tack weld the two parts together, remove, weld securely and when cool, trim as required and refit. Perhaps even put a gusset in before welding.

Trevor

Mark,

I wouldn't try pulling it together, but I would increase the size of the stop drilling at the active end of the crack to allow a larger circumferential surface for the stress concentration in the crack tip to dissipate through. Doubling the diameter of the hole will increase the circumference by 4 times and reduce the hoop stress in the hole to 1/4 of what it was. I have seen severe cases extend beyond a stop hole after pausing there for a while.

The crack itself is probably stable enough now and bolting clamp plates, bedded down on epoxy, to either side of it will restore strength to the casting in a stress free way.

Regards

Brian

many years ago a guy at our club had the same sort of problem the repair that was carried out was drilling a hole so the crack could not go any further a plate first bolted on then this plate was taper pinned as well all then covered with Belzona for cosmetic appearance

I would use an internal 5mm steel plate, tapped to accept C/S screws, bedded on resin and pinned with dowels. The screws can then be filled and painted. Colin

+ 1 for bolting a plate on the inside. As said, it will be worthwhile cleaning the inside surface, so that the epoxy can fill all the surface irregularities and bond the plate to the parent metal.

Howard

Spent today shaping a plate, cleaning it all up and bonding and bolting it in place. With a bigger workshop I'm sure it work have been easier to bend the plate, but I got there eventually.

These photos are before I bonded it in but you get the idea.

That looks like a proper job, should stave off any problems for a few decades.

Richard.