626 mill riser block

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awemawson:
And I've got an 'offcut' 5.5 metres long of 5.5" x 5 mm wall tube left over from making the new roller for my flail mower that might perform service as a riser if anyone 'down south' needs a slice cutting off.

John Rudd:
So now back home and in the shop.....

I swapped out the 3 jaw for the 4 jaw indi chuck on my lathe....

The 160 mm chuck is more than man enough for holding this big piece of round bar... :thumbup:

So tried clocking it up, the outer surface is a bit rough, I managed to get it within 5 thou at the free end.....but the chuck end....ooh man its well out of true....

So do I leave as is and true up the diameter as far as I can get to the chuck end or should I clock it at the chuck end and then machine the diameter?

Never done this before so any advice appreciated.... :bow: :bow:

philf:

--- Quote from: John Rudd on November 15, 2016, 11:03:24 AM ---So now back home and in the shop.....

I swapped out the 3 jaw for the 4 jaw indi chuck on my lathe....

The 160 mm chuck is more than man enough for holding this big piece of round bar... :thumbup:

So tried clocking it up, the outer surface is a bit rough, I managed to get it within 5 thou at the free end.....but the chuck end....ooh man its well out of true....

So do I leave as is and true up the diameter as far as I can get to the chuck end or should I clock it at the chuck end and then machine the diameter?

Never done this before so any advice appreciated.... :bow: :bow:

--- End quote ---

John,

Unless you've lots of material to spare on the diameter I'd get the bar fairly parallel to the axis of your lathe and then carefully face off and take a minimal skim off the od just enough to clean up and clear the depth of the chuck jaws. I'd then turn it end over end so the nicely faced off end fits snugly against the chuck and the chuck jaws will have a nice perpendicular surface to clamp on. If your piece of bar is sawn it's quite possible the ends may be quite a bit off-square.

Phil.

awemawson:
John, I know that you say your chuck is more than man enough to hold it, but I'd be nervous with that amount of overhang with such a weight :bugeye:

I reckon your earlier idea of tapping and bolting from the rear of a face plate would be safer - it only needs a tiny dig in with your boring operation to totally spoil your day :scratch:

Pete W.:
If it was me, I'd choose the squarest end and carefully explore for the centre, say with a centre square. Having centre-popped it, I'd chock the piece on the table of the drill-press so that the flanks were at right angles to the table surface. If you've got a big enough angle-plate, stand it on end on the drill-press table and clamp the piece into its 'vee' with a big G-clamp. Centre drill to enlarge the centre-pop. Then I'd transfer the piece to the lathe with the other end in the chuck and the tail-stock supporting the centred end, using a half-centre if you have one. Hopefully, the end in the chuck will be square enough for the chuck jaws to get a good grip - even if the piece only touches the face of the chuck in one place. Face off, leaving the smallest possible spigot in the middle, hopefully small enough to go through the hole in the chuck or face-plate. Marking-blue the end and mark out the holes to attach to the face-plate, remove from the lathe and drill and tap the holes. (If you're feeling really fussy, file off the spigot first.) Transfer to the face-plate and proceed according to John S' method. Having got the piece securely mounted on the face-plate, there might be some merit in facing off the now outer end and putting in a set of tapped holes in that end too.

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