Milling disaster: spoiling and rescuing a casting

I bought from the US a casting for a T-slotted cross slide for my Hercus (South Bend copy) lathe. It was a lovely casting and came with excellent full size plan and instructions, and also some helpful links. There is an excellent machining description here: http://www.practicalmachinist.com/vb/south-bend-lathes/machining-t-slotted-cross-slide-177054/ I had spent hours of milling the casting over a couple of days with 32 mm two tip 3 Morse facing cutter, and 12 mm solid carbide end mill. At the start of one session, after switching to the latter, I had not tightened the draw bar enough, and the cutter pulled the collet chuck out of the taper and climbed down into the work. Naturally, this was when close to the final dimension.

I felt quite sick. My first instinct was to throw it in the bin and forget about it, but of course, that is not possible. I sobered up a bit and started thinking about what to do. It was at least on the bottom. I decided to mill an even slot where the dig in was and make a filler piece to repair it. The problem was where to find a suitable strip of cast iron. I remembered I had an off cut of drain grating from the club, so I dug it out and started bandsawing it to managable dimensions.

The band saw really struggled, taking about 40 minutes each side. Eventually the blade broke, a first for me. I thought about a slitting saw for about a millisecond. It seemed very hard, but not chilled material. I thought I'd try the angle grinder as a final attempt. It worked well using a thin disc. I was able to slice out a piece that I could mount in the mill to true up.

I was now in a position to true up the gouge and make a filler piece to fit. I tapped four M3 holes to screw the filler into

I then screwed and epoxied the filler in.

Nice rescue, Simon

The drain grating material actually looks pretty good.

Our local cyclists might get a few surprises

MichaelG.

Well done for having another stab at it. I've been there a few times where i've thought there was nothing i could do, till i went away and thought about it, i would say it's human nature at work and also to make mistakes! You're not alone on that front. I almost start a job now kind of second guessing whether i'll make it through without a hitch.

Michael W

I left it overnight and milled it flush this morning. You can see the screws with their allen sockets mostly milled away, and there is a little more to remove once I've cut the dovetail. None of this was quick or easy, but what started as a very bad day in the workshop became a very satisfying problem solving project in its own right. The repair is at the front, under the protruding deck for the top slide, so should be all but invisible. How on earth I am going to engrave the degrees on that deck is a problem for another day.

Thanks Michael(s). The grate machined evenly but was harder than the casting, which was obvious when traversing the cutter and it hit the filler piece.

No problem, i suppose the only way I can become an expert at broken tap repairs is to break many myself!

Michael W

A very neat rescue operation.

> the protruding deck for the top slide

I thought that was excess epoxy oozing out, I thought you had overdone it...

True confession, my t-slotted cross slide has similar gouges, much smaller, filled with JB Weld - only cosmetic and at the bottom of a t-slot out of sight, but I know they are there and now so do you, so let's keep it bewteen ourselves

Neil

I was given a Myford vertical slide and it has a horrendous milling cutter gouge in it, really deep. I must dig it out and give it a dose of the same epoxy.

WRT the degree scale. Although pretty there is not a lot of point in it. It is never accurate enough for actual setting for tapers anyway and you can make a simple template for screwcutting angles. Better not to risk an error and wait until you have suitable equipment that makes it easy.

That looks like a very neat rescue operation, well done Simon. I guess the casting was expensive, so with some extra work you saved the casting.

Thor

I needed to do a rescue of my own today, i recut a new gear in aluminium for my mill (the old plastic one was making a horrible noise missing a few teeth) Sadly, it lost a tooth down to a nut that wasn't fully tightened on the arbor.

I made a new tooth by pressing some epoxy into the missing one and forming the shape by using the cutter lined up with the adjacent tooth.

Michael W

A good repair and well done for getting it done!

I note the statement 'I sobered up a bit'. I hope it was not caused by machining while 'under the affluence of incahol' Or did It drive you to drowning your sorrow?

Even the best (that doesn't include me, btw) occasionally need to make repairs. Keith Fenner recently had a 'slip and climb' mistake to repair on u-toob. My most remembered failings in the past is that of making two of the 'same handed' items, even (or especially) after knowing they need to be of 'opposite hand'? Now that is annoying for me! Especially if they need to match exactly, dimensionally,