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Washout
17-06-2014, 05:30 PM
Hi All,
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I find myself in need of boring a 28.8mm diameter hole into some 6082 round stock, but ideally need it to be 188mm deep.
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I have an 2MT tailstock and/or a tool post that will take 10mm tools, but I can't seem to find anything for my lathe that will go deep enough in all my usual haunts (RDG, Arc Euro, Axminster).
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Any suggestions?
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Chris

mekanik
17-06-2014, 06:24 PM
Hi Buddy
That's a big ask with a 10mm tool.
Drill out as much stock as you can,attack it from both ends.Skim the OD to give yourself a good ref for clocking, set it cock on in 4Jaw bore one end turn round and do other end.
My bad forgot to mention you is going to need a fixed steady(assumed you new that anyway)
Mike

Lee Roberts
17-06-2014, 07:29 PM
Another option is to make yourself a longer boring bar "make a tool, to make a tool" kind of thing? Somthing like 25mm OD 100mm long plus the lenth for your tool holder, take out what you can with long drill bits, again weld extensions on those if you need to, dial the OD in first, flip it, clock it, bore again.

Its only ali but, go slow, take your time, take a final "spring" cut.

You can do it :thumsup:

.Me

irving2008
17-06-2014, 08:02 PM
how big is your lathe if it only takes 10mm tooling? to bore 188mm you're going to need at least 400mm (16") movement on the toolholder unless you use a series of tools or move the tool in the toolholder either of which has implications on the accuracy of the bore dia end to end (and how would you measure it?). To use one fixed tool implies something capable of 18 - 20" between centres, your average 7x14 isn't going to cut it (excuse the pun)!

mekanik
17-06-2014, 08:35 PM
Or previously described method but leaving a tad in the bore and see if anyone can loan you a delapena hone to true it up.
I made a boring bar to go between centres with a 6mm round piece of HSS set @ 45 deg ground with cutting edge and locked with a grub screw, job was clamped to cross slide.
Mike

Washout
17-06-2014, 10:09 PM
Thanks guys,

The lathe is a Sieg SC4 and I have 410mm between centres, so can get a decent sized drill bit in there at least to start things off.

Luckily I have redesigned the part and only need to go in 140mm now, but of course its not going all the way through so will be boring blind.

I think I'll have to create a tool by the looks of it although I might be able to get away with a 2MT boring tool set like this one for most of it: http://www.ebay.co.uk/itm/RDGTOOLS-2MT-BORING-HEAD-KIT-MILLING-MACHINE-LATHE-50MM-12PC-TOOLS-/290728892436?pt=LH_DefaultDomain_3&hash=item43b0cad814

Oh I have a fixed steady which is at least one thing.

mekanik
17-06-2014, 11:15 PM
Can't see how you can make that tool work.
140 deep should be dooable with a decent size homemade boring bar, say 19mm dia with HSS bit in the end.
Good luck on whatever you decide.
Mike

mekanik
18-06-2014, 09:21 AM
Morning washout
This is really obvious but i thought i would mention it, if you do make your own boring bar(20mm dia) remove the topslide as this is a weak attachment point for such a long tool.
Set the bar up in "V" blocks clamped to the cross slide.
Mike

Washout
18-06-2014, 10:15 AM
Will do Mike, thanks

Washout
21-06-2014, 09:26 AM
Hi Gents,
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Thought I'd let you know what I ended up doing here.
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I took a punt on this 20mm boring bar: http://www.ebay.co.uk/itm/RDGTOOLS-20MM-INDEXABLE-LATHE-TOOL-BORING-BAR-DCMT-TIPS-/290583188905?ssPageName=ADME:L:OU:GB:3160
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Clamped a milling vice to my cross slide and then the tool in the vice and took things very slowly <0.5mm DoC per pass and other than a couple of hard spots where the tool "dug in" and stalled, everything worked out OK to a depth of 160mm. I was very naughty having the tool oriented in the vice so it could have slipped downwards as that 's the direction of cutting force and its certainly not something I would have tried in steel for sure.
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I must see if I can find a suitable vertical slide for this machine, as then the tool would definitely be better clamped and would also be handy for the milling head, which I use for light, quick and dirty manual milling.
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Cheers for the advice chaps.
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Chris

mekanik
21-06-2014, 09:59 AM
Morning Chris
Glad it worked out OK
Mike