Re: Clamping large dia. for centre-drilling
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Instructions seem odd. The standard way of doing such a bore is TS drilling - but the workpiece is too long for that.
How I would do it is use the extended way bars, intended for wood turning. Clamp the workpiece in the 3-jaw, support it near the end with the steady rest. and put the TS on the extended end of the way bars for drilling.
Now, I realize this does not help you if you have neither the extended way bars or the steady rest. But those are two invaluable accessories for TS drilling on the Unimat (DB/SL).
Martin
-----Original Message-----
From: William Ayerst <willayerst@...>
To: [email protected]
Sent: Thu, Apr 23, 2020 1:35 pm
Subject: [Unimat] Clamping large dia. for centre-drilling
Hello again chaps,
Last question for a long time I hope - I¡¯ve got the majority of techniques tested for the Edenstaal cannon - the last question on it, I hope is that it suggests to centre punch the ends (of a 6¡± x 1¡± dia aluminium rod) for a cannon barrel - but then says ¡®clamp the work to the tool post, using a 3/8¡± drill in the headstock bore the barrel to a depth of 2 3/4¡±.
On the face of it, this doesn¡¯t seem like an unreasonable ask - but after checking it looks like there¡¯s a problem:
- I have the machinist vice attachment, and it just about has capacity for the 1¡± dia rod on the flats of the jaws (which I¡¯ve heard is bad practise) -but the resultant centre line position of the clamped rod is way higher than the headstock centre.
- I also have a milling table attachment I can put on the toolpost, but that raises it up even higher!
The only thing that comes to mind, is using the strap clamps from the milling table directly in the t-nut slot on the tool slot!
Hopefully, that¡¯s my last query - thank you all so much for the help, hopefully some output will be here shortly!
Cheers,
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