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27th Nov 2017, 09:36 PM #1Golden Member
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Whatsit Called and Why Do they exist ?
See attached jpeg. Its a Morse 3 taper and the bottom end of the tool is 1" diameter.
What are they called please ?
I use this one to run slot cutters and am looking to make another one to run some bigger 1/4" slot cutters
What is the general idea behind them please ? The two pieces of square steel engage with two slots in the quill.
Is this to ensure that the taper can never spin inside the quill ?
Is it to ensure that the drawbar doesnt tighten too much or worse still unscrew ?
Thanks
Bill
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27th Nov 2017, 10:22 PM #2
I am only guessing of course but I would say an arbor?
Grahame
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27th Nov 2017, 10:43 PM #3
Since I am challenged in the English language department I can't really help with the name. I would assume the two square pieces are "drive dogs" to transfer the torque directly from the quill to the Arbor. I know there are milling heads that have slots for this kind of dogs too, in which case when mounted on the arbor the force would be transmitted directly from the quill to the cutter and the Arbor would "only" be used for mounting and centering the cutter.
Peter
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27th Nov 2017, 10:46 PM #4Diamond Member
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I would refer to these as tool holders or alternatively cutter adaptors. Collet chucks would also be in this category.
The lugs when engaged in their slots transmit the torque from the mill to the cutter, while the taper just locates the tool. They do indeed prevent the adaptor or arbor spinning in the spindle.
I have not heard that another function would be to prevent draw bolt over tightening or unscrewing, and I doubt that would be another intended feature.
If I have any of this wrong, I'm sure that a wiser head will put us both straight,
Rob
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28th Nov 2017, 05:19 AM #5Senior Member
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It's a 'Stub Arbor'.
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28th Nov 2017, 04:14 PM #6Novice
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I agree with Peter, I used to use shell end mill cutters with drive slots on the back like this
https://3.imimg.com/data3/JK/QA/MY-7...ls-250x250.jpg
I note the square tongues seem to be removable, and then you would have drive slots. A similar design
https://ae01.alicdn.com/kf/HTB1mauRO...-font-font.jpg
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28th Nov 2017, 07:09 PM #7Golden Member
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Thanks for the answers, the notion that the taper simply centres the tool and the drive dogs transfer the torque helped me to understand things a lot better, I have always been thinking that the taper and the drawbar are sufficient to hold and drive a tool, ie morse taper drills only have the taper to secure them.
Will have a go at making one to drive some slotcutters and dovetail cutters that I got on ebay recently.
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28th Nov 2017, 09:57 PM #8
The stub arbor is used on a mill or similar, and the taper on it's own is not good at resisting side forces as the job is fed into/across the cutter. Because of this, the side loads tend to release the taper in its socket. The drawbar is used to provide a force continuously pulling the taper into the socket to resist dislodgement, but the tool/cutter can still need sufficient torque to twist the taper in the socket, so drive dogs can be used to transfer the drive torque from the spindle to arbor.
With a drill press etc and taper, the natural force is from the spindle through the socket and taper, down the drill and into the work piece. There should be no significant side forces from feeds etc that might loosen the taper in the socket. The MT drill bit or chuck arbor usually has a tang that locks into a reccess at the narrow end of the socket, and the fit between tang and recess can transfer the torque if required.
A tang and a drawbar are mutually exclusive.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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28th Nov 2017, 10:28 PM #9Golden Member
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Tidied up the last bit of confusion
Thanks Mal,
That's tidied away the last bit of confusion.
Should have been able to figure that out for myself but the bit of my brain that sort of already knew that wasn't talking to the rest of me, it just went aha! when it read your post.
Bill
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