You might have answered this in your clip, but if so, I missed it!

What material is the plate made of?

You have a PM re your AXA toolpost.

Obviously done by the latest ham fisted owner

Regarding the old tool post I found on some of the imported toolholders that they bottomed out on the post before the cam was fully tightened where I have marked in red. Quick touch to the two arrowed areas on a linisher soon had them holding tight. You may also want to look at the areas marked blue for a similar issue.

If you could sort that then the toolpost could be mounted on a raising block ontop of your repaired plate at teh rear of the cross slide.

Nick,

That's a very useful video … a picture's worth a thousand words, and that is certainly worth several thousand.

Like Muzzer; I presume the plate material to be cast iron [and it looks to be of the appropriate quality, too] … Excellent stuff in compression, but poor in tension etc.

I think the most likely explanation is that the initial damage was caused either by running the top-slde into the tailstock, or [more likely] by some 'impact' event … This would initiate a crack at that weak point, although it may only have been microscopic. … The crack then gets extended by a process known as 'Stress Corrosion' [and your rattly toolpost is almost certainly the source of input energy for that].

Excellent news that Boxford still had a spare plate available !!

I wouldn't bother trying to repair the cracked plate … just use it in some configuration where it is only seeing compressive loads.

MichaelG.

Over enthusiastic tightening of the "pad" screw in the front of the plate (possibly with the aid of a hammer) would not have held the tapered spigot of the topslide with a much improved tension, it would however have easily pulled the mounting plate at that point outwards towards the front.

This I would suggest is the primary cause of the radial spllt in the plate to be exacerbated by the rotational forces of the cutting tool.

The QCTP post type previously used are fine if as Jason has pointed out, the parts are correctly made and tightened. The cam action of the cheaper copies is not always correctly set up due to sizing problems. ORIGINAL Dickson TPs did not suffer in that respect.

Vee screws produce a bursting effect on a threaded hole as they have a wedging effect against it so overtightening could cause this type of fracture which is one reason for vices to have a square or buttress thread. Colin

Boxford have used that clamping arrangement on all of their lathes that I am aware of even my ME10 but both screws go in from the back. The cross slide bulges out where the compound sits. The metal thickness at above the holes looks similar. I've never heard of one cracking.

I would wonder if the crack was their when you bought the lathe. Putting the screw at the front like that seems to be a rather retrograde step as cutting forces will be acting directly on them. Maybe the plate can be swung round to prevent that.

The other reason it may crack could be down to well over tightening them. Don't know what is supplied with your lathe but mine has the hex key for them is on one end of the chuck key handle. They only need firmly nipping up as considerable force can be applied via the screw – put the 2 together, plate orientation the wrong way round and the compound slips – more tightening etc.. Crack.

Maybe the marks on the tailstock are down to metric screw cutting if it's an imperial lathe. I assume that on the metric version they supply the same type of screw cutting indicator as they do on the usual older Boxfords. It allows many of the pitches to be cut in the normal way by disengaging screw cutting at the end of the cut and winding back by hand. The choice of 1 of 2 gears on the indicator maintain sync with the thread.

I assume that the power feed is still the same so that wouldn't mark the tailstock badly. It's effectively a friction drive so that it can be run up against a bed stop. On the older lathes the drive is obtained via a slot that runs down the lead screw that drives a keyed bush. The friction level can be adjusted with a knob on my ME10.

I wouldn't think of welding to try and repair it. Cast iron isn't well know for welding well. I'd simply clamp firmly and add some straps to the outside. 6mm thick ms should be fine screwed and doweled or roll pinned to the edge. There is a sort of stapling method but it would need more space than you have. I've seen it used to fix large miller head castings – some one walked away and left the vertical power feed on.

If you want to throw your dodgy QCTP away please use my dustbin. I'd say the problem is too much cam action and maybe incorrect material. Over time I suspect you wouldn't be able to get the screws out of the holders as the ends will bell out. Best fit high tensile screws.

John

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Hello Nick,

The failure has all the hallmarks of a fracture in cast iron, it will be present on the underside of the plate too. Good as you say your welding friend is, he will not be able to repair that satisfactorily for you, it is too thin. Others have suggested fitting a 'strongback' to clamp the crack closed.

I fear that too is a futile solution as the wedging action in clamping the compound slide is very strong and it will still cause the crack to gape and eventually that action will distort the screws holding the strongback in place, leading to complete fracture on the side opposite the present crack.

Now that you have a dependable spare I would be very tempted to make a faithful copy of the plate in decent steel and then use that for normal working. Your intact plate could then be moved as you suggest to the rear of the X slide for use when parting off.

I am sorry to be so gloomy about the prospects for salvage, but I suspect the previous over run into the tailstock started the problem, to then be compounded by the trouble you have had in parting off with slop developing in the tool holding block. I think Jason has shown very well how that might be rectified and brought back from the scrap bin.

Regards

Brian

Edit  I rather suspect that all that has been holding it together across the crack are the mounting screws holding it down on the cross slide

Edited By Brian Wood on 15/07/2015 20:22:29

I was going to say "make a steel one" but Woody beat me to it. That casting is very thin, and seriously weakened by the holes for the clamps. You can't easily thicken it up without raising the centre height of the toolholder, so the thing to do is to use a stronger material.Given that lots of Boxfords went to schools, I feel they may have sold more of these parts than they are telling . Any slackness in the holding down bolts would also put it under extreme strain, especially in a dig in situation. Parting off on a lathe is the purest test of how rigid the machine is (I HATE it)

Phil