Why do lathe tailstock barrels not grip the tang (on MT shanks)?

Perhaps other lathes are not like mine. But my tailstock barrel does not
have a means of gripping the tang on Morse taper shanks. Assuming that this
is common in lathes (and not just an indication of poor design by my lathe's
manufacturer), why is that? Is it supposed to intentionally allow the taper
to slip if subjected to excessive forces?
Reply to
DeepDiver
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I think it's a crime not to have a tang slot in a lathe. I must say that it seems like a relatively simple job to install one. I have looked at mine and it is simply a cross drilled and threaded hole in the right spot on the barrel with a set screw inserted to the correct depth on either side of the barrel.
Bill D
Reply to
Bill
"DeepDiver" snipped-for-privacy@sonic.net
I don't know the answer, but certainly it is very common for lathe tailstocks not to have a radial knockout. Although a slot for a tool tang end certainly seems to add holding capability, I don't think its absence on a lathe TS is anything but a customary design result. You don't want the taper to slip at all, yet TS tapers certainly seem to do that with some frequency when holding a drill bit.
The TS screw is its knockout, so adding a drift hole radially might be somewhat superfluous. Some lathes have them, such as some watchmaker's, which might not have the slot and tang end setup (also no screw), however
Many years ago, before the "thru hole" became so popular for headstocks, these were solid, and the HS spindle had a radial knockout hole, usually but a round hole, on, say, a mid-1800s machine, again, no tang and slot.
Frank Morrison
Reply to
Fdmorrison
And what, exactly, will keep the tailstock ram from turning? Most ram keys are pretty lightweight. If the tailstock ram does turn with the work, the ram screw will advance it. Not a good situation. A dry taper in good shape should give all the driving force necessary. If you need more, a dog on the drill shank is the way to go.
John martin
Reply to
JMartin957
I had thought about that, and also wondered why the keys were so puny.
Agreed--that would be bad! But I doubt the lack of a tailstock barrel tang engagement would provide any measure of safety if the key did fail. Certainly the axial pressure from an uncontrolled feed would do a fine job of locking the taper up tight! I suppose the only benefit to the lack of a tang engagement is to allow the taper to slip *before* the forces get high enough to break the tiny key that prevents the tailstock from rotating.
But the tangential forces of the dog are likely to force the drill off center, thus cutting an enlarged and bell-mouthed hole, no?
Reply to
DeepDiver
I have no idea what would prevent other tail stock rams from turning under load. Mine will not. I could expand the scope of the thread, and also say that I think it's a crime not to have a good substantial ram key with at least the capability to handle drilling operations, but it was not the focus of the discussion. In any case *I* think that's a given and I have a couple of forty plus (sixtyish) years old lathes with pristine tail stock tapers (both MT 3) and I attribute their condition to the having the tang slots. I figure Monarch knew what it was doing when it was installed .
Bill
Reply to
Bill
Gunner snipped-for-privacy@lightspeed.net
And that could occur with any lathe TS and short length taper tool.
You could also buff out the screw end, so as to be able to use the shorter tooling. FM
Reply to
Fdmorrison
I had a similar surprise. Even though my dead centers have no tang, they still get pushed out by the tailstock barrel leadscrew...until I got one that was a little too short. But it is a center I like to use for some applications because it is extended. So I made a short "plug" out of drill rod, chamfered on the ends and then polished so as not to scratch the tapered socket. I stick this into the barrel before inserting the too-short center. The plug allows the leadscrew to push out the center. I use a magnetic retrieval tool to fetch the plug out of the barrel.
Reply to
DeepDiver
Us knuckle dragging HSM's aren't that smart. I magnetized a loose 3/8" ball bearing and stuck that to the end of the too short shank before inserting it in the taper. :>)
Reply to
Jack Erbes
Another thought. The taper shanks are not usually very hard. It is often possible to drill a hole in the back of the center (shank end), and insert a pressed-in extender plug. If it's soft enough to allow tapping, a screw can be used instead. This will add enough length to allow the TS screw to eject the center (or other tool). Once you do this you don't need to remember to insert the loose plug.
Dan Mitchell ==========
DeepDiver wrote:
Reply to
Daniel A. Mitchell
"DeepDiver" >
Way cool idea. I need one of those. I have a live center that won't come out with the screw or a drift. I put a allen key in the slot and crank the ram back to push the center out with the key. If the little plug were magnetic it would stick to the center always, I wouldn't need a magnet to pull it out. Tom
Reply to
Tom Wait
I considered that, but I generally don't like the idea of (permanently) magnetic tooling around my lathe or mill: they tend to attract chips and then one spends more time trying to get the chips off them, than any time saved by having them magnetized. Of course, if the magnetism is a required feature of the tool (like magnetized spacers to attach to your chuck jaws), then one must deal with the chips problem. But in this case, I don't think it's worth it.
Reply to
DeepDiver
Interestingly, it can't happen on our Jet mini woodworking lathe. The tailstock screw and handwheel both have a through hole, so you could insert a rod through the handwheel and screw and touch the small end of the taper. A tap with a hammer and it's out.
Apparently, this feature is there so you can insert a long drill through the tailstock and drill a workpiece being turned between centres. The only use I can see for it is to drill the wiring channel through the middle of a table lamp base that you're going to turn. But it also provides a way of knocking out a stuck short taper. (Backing out the ram is the normal way to unseat a taper on this lathe).
Dave
Reply to
Dave Martindale
I should have mentioned that the live centre *also* has a hole clear through the middle of it. The centre point of the live centre is actually a removable insert that seats in a short taper in the rotating part of the live centre. If you were to do through drilling, you'd remove it, and support the end of the work with the cup centre that remains after the centre point is removed.
Dave
Reply to
Dave Martindale
[ ... ]
And my Clausing (12x24") has the tang slot in its MT-3 ram too. The tang goes horizontal, and if you crank the ram out far enough you see the slots.
The older Clausing tailstock which I used for a while with this machine has a MT-2, and no tang slots.
Enjoy DoN.
Reply to
DoN. Nichols
[ ... ]
Well ... I picked up a live center (MT-3) with changeable centers (both male and female) from eBay. It is a nice fit, but it does not extend far enough to engage the leadscrew for ejection. But it happens to have a thread in the back of the taper, and all I need to do is figure out what the thread pitch is (I suspect metric of some flavor), and turn up a plug to fit that, with enough length to eject cleanly. (Perhaps a touch of Loctite to keep it from vibrating loose in service.) I'll probably make the diameter small enough to clear the tang slots, instead of bothering to make a tang on something which does not get that kind of torque applied (unless the bearings freeze. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
Well, I have my reasons...
This is an extended-length dead center. Because I haven't gotten around to making a pump center, I occasionally use this long dead center as a makeshift pump center. Thus, I need access to the hole in the end of the tool.
Reply to
DeepDiver

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