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Thread: Boring Bar holders for 25mm bars
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11th Jan 2017, 08:50 PM #1
Boring Bar holders for 25mm bars
Has anyone used a boring bar holder which allows the use of a bar with a dia of 25mm or greater in a lathe which was originally using 16-19 mm tooling ?
This is for use in a four sided tool post or at a pinch in a quickchange .
I recently saw Keith Fenner using one when he bored the hub of the fan he made recently.
Michael
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11th Jan 2017, 09:03 PM #2future machinist
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At work we have a 50 mm bar goes alright in the old nuttal lathe. Its a 25mm toolpost but same principal.
BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE
Andre
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11th Jan 2017, 09:13 PM #3
That is exactly what I meant , I may just have to make my own as all of the "machinery suppliers" dont seem to be able to supply one that can be used in multiple different capacity lathes .
They want to sell one for each machine and all will need some changes to be suitable for the intended work.
Michael
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12th Jan 2017, 07:24 AM #4
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12th Jan 2017, 08:16 AM #5future machinist
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BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE
Andre
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12th Jan 2017, 11:11 AM #6
The next step would be to make a new toolpost specifically to hold boring bars. This is one situation where the QCTP is limiting rigidity. Of course if the carriage is moving around it won't make much difference how rigid the toolpost is.
Dean
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12th Jan 2017, 09:33 PM #7
The job which I need this setup for is a brake drum of about 12.8 inches ID which has a slight lip from normal wear , its very difficult to fit and remove presently .
I want to make a main holder to which I can fit split bushes to enable bars to be held from 12mm to 25 mm .
I also want it not to be machine specific as there are currently two lathes and the HBM and the mill which all need to have boring bars for some work.
Michael
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12th Jan 2017, 11:05 PM #8Golden Member
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Making your own holder is probably the best way to get what you want.
I have done the same - on a smaller scale - by making a dedicated boring bar toolpost. Start with a suitable size block of steel, face off one end of the block and drill/bore through so it can be clamped to the compound slide with your usual tool post clamping screw. Then it is simple to use drill/ reamer / boring tool in the headstock to through bore the new toolpost to take a boring bar as big as you need.
Advantages are that the axis of the bar is at centre height, the size of the bar is not constrained by existing toolpost arrangements, and the setup is very rigid with minimal overhangs. Can be sleeved for smaller size bars as you wish.
This may not ideally meet your requirement for use on different machines, but perhaps could be made for the lathe with least centre height and adapted to the other lathe with a riser block. Not sure about application to a HBM or a mill.
Cheers,
Bill
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13th Jan 2017, 11:07 AM #9Member
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[QUOTE=WCD;1916729]Making your own holder is probably the best way to get what you want.
I have made a similar Boring Bar holder for my Hercus Craftsman, taking bars from 10mm to 25mm, grooving and other threading tools.
Also included a Part Off Toolholder.
Not a QCT but very rigid particularly for the 'white knuckle' part off jobs.
Col
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13th Jan 2017, 03:16 PM #10Most Valued Member
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If the boring bar is round, think about holding it in something like an ER32 or ER40 collet. I made such an adaptor up for my Kearns S type HBM. Works fine.
Won't work for the TCT bars with flattened tops & bottoms though. Could make up some sort of sleeve I suppose but now it's getting too much like a major PITA for any possible gain.
PDW
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14th Jan 2017, 05:49 PM #11Banned
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Looking at something similar me-self. Use a straight shank ER holder mounted in a larger boring bar holder. US Shop Tools have a range starting page 188.....
http://www.usshoptools.com/NEW_WEB_2...12_catalog.pdf
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14th Jan 2017, 10:52 PM #12
Just completed the boring of a 25mm hole in a piece of 50mm bar , tomorrow I will weld a tab on the side and then mill tat flat and parallel to the bore.
After that several sleeves to make for the smaller bars .
The 25mm bar that I want to use is as PDW described a round bar with four flats machined on it , it is for gorrving , "o" rings etc.
Hopefully this will allow more use of my boring bars , instead of them being machine specific.
Michael
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