I'm about ready to assemble my spindle for my mill. I have acquired and installed a new set screw for indexing tooling into the R8 spindle. I've read a number of things regarding whether or not it's a good idea to have this in the spindle and want to hear what other may offer regarding this
thanks
Brian
R-8 Spindle Key
Re: R-8 Spindle Key
I like having the key. The reason people hate them is because the collet wasn't tight enough or machine crash. Then it is a bigger hassle and it is the key's fault. Well, a key is not a pin, not the threaded end of a loose grub screw. It presents a flat to the slot of the collet, to keep the collet from spinning while tightening and reach the point where the collet taper locks in the spindle. It is not a driving point for a loose collet and consider why a collet would be loose ? Possibly because While it was being tightened, it kept shifting around in the spindle bore.
There is another thing about collets... They aren't all the same in the slot department and that' part of why a key seems too long or so short, it strips.
There is another thing about collets... They aren't all the same in the slot department and that' part of why a key seems too long or so short, it strips.
Re: R-8 Spindle Key
The problem with keys is an example of other areas which become problems. Back when major U.S. Manufacturers were the only source of expensive precise collets, all areas of the collet were final ground to Hardinge specs. I recall Royal would fit a precise bore but others would not. I remember having to take a few strokes off the key depth, in order to use Enco collets. That was because I, like many, acquire an industrial machine tool and still want to save on the tooling. Enco weren't terrible, just a minor difference. The way it goes, is that keys and collets do wear and when a rounded key meets a shallow slot, bad things happen even while tightening. So there is the inevitable slide towards another key thing becoming irrelevant when the intention was proper.
Re: R-8 Spindle Key
Almost all professional machinist's will say that set screw key isn't needed, and it can in some cases create huge problems if it shears off in use and wedges the R-8 shank inside the taper. I've read of some very expensive repairs and regrinding needed due to that pin. If? you never ever forget to tighten your drawbar and never ever do massive hogging cuts, and never ever have a crash with large diameter tooling, then that pin should be just fine.
I have found one use for it. Maybe a temporary use for me though. That pin does index any R-8 shanked tooling so it's located into the same position within the spindle. Something like a Haimer 3D Taster edge/height finder requires the shank it's zeroed in to be indexed into the spindle in the exact same position each time. For myself it's the only reason I'd think of keeping that setscrew pin. A permanent mark on the shank and on my mills spindle would do the same and be a much better idea in my opinion. That setscrew as Spro said prevents tooling such as collets from rotating as the drawbar is tightened. But if you keep your drawbar threads in good condition and PROPERLY LUBRICATED as there designed to be used. And your female tooling threads are maintained as well, then to be honest there's probably very little real need for that pin at all. It was never designed as or intended to be a driving lug.
Pete
I have found one use for it. Maybe a temporary use for me though. That pin does index any R-8 shanked tooling so it's located into the same position within the spindle. Something like a Haimer 3D Taster edge/height finder requires the shank it's zeroed in to be indexed into the spindle in the exact same position each time. For myself it's the only reason I'd think of keeping that setscrew pin. A permanent mark on the shank and on my mills spindle would do the same and be a much better idea in my opinion. That setscrew as Spro said prevents tooling such as collets from rotating as the drawbar is tightened. But if you keep your drawbar threads in good condition and PROPERLY LUBRICATED as there designed to be used. And your female tooling threads are maintained as well, then to be honest there's probably very little real need for that pin at all. It was never designed as or intended to be a driving lug.
Pete
Re: R-8 Spindle Key
This has been interesting and we must see it from different angles or it wouldn't be.
Re: R-8 Spindle Key
Do we think that a Van Norman V5/C5 has a key across into its taper or that all the outside slots in collets don't matter ?
I largely defended the "key" idea in face of overwhelming accounts of its irrelevance. That is, it is not a worthless thing or the original design and engineering wouldn't have incorporated it. Trumping all this discussion, is what works for you. How can I know the internal taper condition of anyone's spindle? Consider the spindle taper is off a few degrees and another collet is off too. You can crank the torque up, over anything level that I would, and still not have a surface lock in the taper surfaces. That nagging pin or key is in the way and takes the torque and shears. This type of discussion has gone on with different tapers and the bottom line is that; No tang and no key is designed to take the torque of the precision dry mate of the angled surfaces.
Things wear or may not have been quite correct at the beginning. There are ways to check the taper and there must be some standard. Otherwise, it is like a virus. Every collet is subjected to over tightening and what? They go on ebay, what?
I largely defended the "key" idea in face of overwhelming accounts of its irrelevance. That is, it is not a worthless thing or the original design and engineering wouldn't have incorporated it. Trumping all this discussion, is what works for you. How can I know the internal taper condition of anyone's spindle? Consider the spindle taper is off a few degrees and another collet is off too. You can crank the torque up, over anything level that I would, and still not have a surface lock in the taper surfaces. That nagging pin or key is in the way and takes the torque and shears. This type of discussion has gone on with different tapers and the bottom line is that; No tang and no key is designed to take the torque of the precision dry mate of the angled surfaces.
Things wear or may not have been quite correct at the beginning. There are ways to check the taper and there must be some standard. Otherwise, it is like a virus. Every collet is subjected to over tightening and what? They go on ebay, what?