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Sun God
03-21-2013, 09:01 AM
Why does everyone get so down on lantern toolposts?

I have been driven to madness by the 4 way toolpost on my 12x48 lathe. I feel I can honestly say, I would rather have a single station, that I could easily adjust on to center, than four stations with all the adjustment finesse of a sledgehammer.

I have considered swapping out to one of the ubiquitous Aloris type posts, but as always my lathe makes life difficult - the compound isn't t-slotted, but has a threaded in stud on which the original toolpost rotates. People always complain about the lack of rigidity in a lantern style post, and I would agree when you are sticking a great big Armstrong type holder in there to hold your bit, on top of a rocker - the moment arm is huge. But when I look at your typical Aloris type holder, the moment arm seems equally huge; it is just that the toolpost itself is more massive, but the holder itself is not, and is generally supported in tension only by a single screw.

I was browsing Tony Griffith's lathes.co.uk site the other day when something caught my eye - Looking at the page for the Atlas 6" mark 2 was this toolpost:
http://www.lathes.co.uk/atlas6inch/img46.gif
It seems so simple - threaded on the outside; a hex nut on the bottom to pull up the T nut, a knurled nut in the middle with which to set tool center height, and in my view, above the tool should be a washer, and then another hex nut with which to fix the tool.

Can anyone see obvious fault with a toolpost built to this pattern, of approximately an inch in diameter, designed to hold the half-inch HSS tools I invariably use on this lathe? Holding the toolbits directly in the toolpost, I cannot see how it could be less rigid than an Aloris type holder; the moment arm would be equal, if not smaller. And it would be far more manouvreable than the equivalent Aloris.

Doozer
03-21-2013, 09:06 AM
Where does the force come from to clamp the Tee slot?

--Doozer

camdigger
03-21-2013, 09:10 AM
Where does the force come from to clamp the Tee slot?

--Doozer


Looks like the force comes from the screw inna middle pushing down on the toolbit, etc. At least that's how my lantern toolpost works...

gizmo2
03-21-2013, 09:17 AM
Looks good; only issue I see is sharpening the tool bit. Changes the height a little, which is where the rocker comes in handy. I t looks like you would have to change washer thickness, which makes it every bit as fiddly as anything else.

Sun God
03-21-2013, 09:19 AM
Where does the force come from to clamp the Tee slot?

--Doozer
I believe the T-nut is machined integral to the top (threaded) section of the toolpost. You can see on the very bottom of the threaded section of the post, there is a hex nut - I believe this nut would be threaded down against the top of the compound, which would force the toolpost writ large upwards, and the T-nut would then pinch the T-slot between the top surface of the 'T-nut' and the bottom of the hex nut.

At least, that is how I planned to implement it.

Sun God
03-21-2013, 09:21 AM
Looks good; only issue I see is sharpening the tool bit. Changes the height a little, which is where the rocker comes in handy. I t looks like you would have to change washer thickness, which makes it every bit as fiddly as anything else.

Ah but thats the beauty of the design - you aren't using a washer to set center height, you are using a knurled nut on the outside of the toolpost, so the center height is nearly infinitely finely adjustable. To adjust center height you only have to loosen the tool clamp, finger-adjust the nut to be on height, then re-tighten the clamp.

You can also adjust the toolpost angle without changing center height - just loosen the bottom hex nut, rotate to position, and retighten.

Mcgyver
03-21-2013, 09:38 AM
The design looks similair to the fantastically designed unimat tool post. The post isn't threaded, there's a sleeve going over the post and its threaded (with a cut out for the tool bit). Nut goes on that sleeve. This lets you adjust the height and the tightening the screw from above clamps everything.....I've often thought of making a larger one.

QCTP are good but their bulky designs often get in the way of the tailstock so a post like this could be very useful

Sun God
03-21-2013, 10:02 AM
The design looks similair to the fantastically designed unimat tool post. The post isn't threaded, there's a sleeve going over the post and its threaded (with a cut out for the tool bit). Nut goes on that sleeve. This lets you adjust the height and the tightening the screw from above clamps everything.....I've often thought of making a larger one.

QCTP are good but their bulky designs often get in the way of the tailstock so a post like this could be very useful
Got any pics of the unimat post? I'm always keen for inspiration. Had a google, but no luck.

Clearance is probably my biggest reason for wanting this; was doing a big turning job on the weekend and the 4-way post was seriously fouling the live center. Very irritating.

What was even more irritating, was realising after turning off a lot of diameter at high SFM, low DOC with carbide tooling, I had specifically ground a knife type HSS tool for situations like this just a few weeks before, that would have done the job in a fraction of the time. I swear, those things eat diameter for lunch.

Mcgyver
03-21-2013, 10:12 AM
I'll take some today. I hear on the interference.....you end up havnig the tool sticking out to compensate (that sounded wrong!) or the tails stock barrel extended further....all of which increases overhang and is a good practice to avoid.

becksmachine
03-21-2013, 10:16 AM
People always complain about the lack of rigidity in a lantern style post, and I would agree when you are sticking a great big Armstrong type holder in there to hold your bit, on top of a rocker - the moment arm is huge. But when I look at your typical Aloris type holder, the moment arm seems equally huge; it is just that the toolpost itself is more massive, but the holder itself is not, and is generally supported in tension only by a single screw.

I would agree that the lantern post is a quick and handy way to attach a cutting tool to a lathe, and one of the reasons is that Armstrong type toolholder that generates those major moment arms. They allow access to some confined places that would be difficult with other means. However, possible feed rates and DOC will be limited when compared with other types of toolposts. This may not be as great an issue for the average HSM, but we all seem to like taking one pass instead of 2 or 3. ;)

The moment arm is essentially identical for either tool post. The difference being, a toolholder/bit held in the quick change or even the 4 way post has a much better chance of staying put while being subjected to this moment arm. As far as that goes, the above mentioned posts will probably cause greater forces as they will allow the use of heavier feeds and greater DOC.

One of the major culprits contributing to the instability of the standard lantern post is the rocker wedge that is used under the tool bit/Armstrong holder. One solution I have seen to this problem is to replace the wedge ring with a ring that has a series of flat steps of different heights milled into it for the Armstrong holder to rest on. Multiple rings can be made to increase the range of height adjustment.

Dave

Jim2
03-21-2013, 10:46 AM
I've been using a "threaded sleeve" design as described by Mcgyver for the last few years. Somebody posted this idea on "the other" site, and I made a copy for myself. Here's a pic of mine in use.

http://img.photobucket.com/albums/v280/jasch/Metalworking/Tangential%20Tool%20Holder/ToolInPos-001.jpg

I like it much better than the half-moon key and washer that it replaced!

Jim

Dr Stan
03-21-2013, 11:53 AM
The only real advantage of the lantern style tool post is its ability to get in tight places. Otherwise it is a pain. Hard to adjust center and maintain cutting tool alignment (think threading tool), much much less holding power. If you're running a short run of even just two parts you're spending a lot of time just setting up the cutting tools. With the drop in style holders you can set the tools and just swap out the holder. The last time I used a lantern style TP was on the USS Coral Sea back in 1975 or so and I do not miss them. My Logan came with one and its just sitting on a shelf and will probably stay there until my estate sale.

Mcgyver
03-21-2013, 07:48 PM
To the responses critical of the lantern tool - this isn't you're gramma's lantern tool post :). I just notice Jim's is a large version similair to what I've posted below. He had enough room he didn't have to cut out a section of the threaded sleeve like below.

This style is worlds better than the tradition lantern and williams/armstrong tool holder. imo it goes a long way toward removing most of the faults ot the lantern style. The moment and overhang are minimize, it creates a solid base, and is easily adjusted without frustrations of the old style. Making a larger version would be a nice additional bit of kit for when the big QCTP holder is in the way.

In the follow pics the black parts are from a Unimat DB. The silver I made because I adopted to a Unimat 3. Lots of pics so you can see how it works and replicate. That one on Tony's site has way to coarse a thread imo. Fine would be both stronger, give a finer adjustment and make tightening easier


http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6111-large_zps33a5f8f7.jpg


http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6113-large_zps974cb0b9.jpg

Mcgyver
03-21-2013, 07:49 PM
http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6115_zps1010e5bc.jpg


http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6121-large_zps921326a4.jpg


http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6122-large_zpsea909857.jpg

Gary Paine
03-21-2013, 10:02 PM
http://i20.photobucket.com/albums/b201/michael0100/unimat%20style%20tool%20post/DSC_6122-large_zpsea909857.jpg

This is a very nicely made toolpost, but I have personally avoided using any toolholder with only a round button in the topslide t-slot for fear that a catch would break out the slot. I try to use only large T-nuts or bolts in the slide to provide the most strength possible.
The way around it in a lantern like this is to use a T-shaped washer at the bottom and a short bolt up into the lantern post that has a thinned head.

Mcgyver
03-21-2013, 10:14 PM
This is a very nicely made toolpost, but I have personally avoided using any toolholder with only a round button in the topslide t-slot for fear that a catch would break out the slot. .

This one is off a unimat, so not an issue there. It's worth considering, but I think you'd have to really work to bust a lathe T slot this way on a larger size.... but if concerned you coud easily make a large rectangle on the bottom instead of the button giving it the same cross section in the T slot as other posts. I more put the pics up to show the structure; modify as you see fit :)....its been 10 minutes, you've probably already built one by now :D

dp
03-21-2013, 11:30 PM
My lathe admittedly is a bungie lathe. The compound and cross-slide is more reminiscent of a Inukshuk than a tool. Because the cutter is displaced from the hard point by some distance and in three dimensions it tends to twist under load. Any looseness in the dovetails of the slides compounds the problem and yet they need a certain amount of slop to allow the slides to slide.

On my system this manifests itself in a bound parting tool, for example, or a deep cut that flexes the parts noticeably. Accuracy and repeatability are dreams unrequited. I've spent some time exploring how to replicate the lantern post on my shaper onto my lathe for certain operations like parting that put so much twist into an overly compliant lathe. McGyver's sample looks like it may solve the problem. I've already purchased a second compound slide from Grizzly to use as a foundation for what ever I come up with so I won't be breaking a working lathe in the process. And I don't see any reason a rocker can't be added to the example to preserve that vertical option although I've used shims for that purpose for years. When I bought the lathe it did not have a QCTP, but a simple four-way tool holder that rested on the compound. Any vertical was done with shims so I got lots. Using rockers and shims should solve any problem of the superior lantern and still eliminate the bungie feature I'm so not fond of.

Juergenwt
03-21-2013, 11:50 PM
Works best on small manual lathes. Used it for forty years. For fast set ups - you just can not beat it.

The Artful Bodger
03-22-2013, 02:26 AM
The only thing wrong with lantern tool posts is that they do not come with much in the way of bragging rights.

philbur
03-22-2013, 04:53 AM
I assume under the adjusting nut is nothing but free air. The adjusting thread is only seated as well as the clamp bolt is tightened, apply some more load when cutting and the thread may adjust its seating.

A four way tool post is sitting block of iron on block of iron, with no overhang in the toolpost and absolute minimum overhang of the cutting tool. Apart from a relatively thin adjusting nut the tool in the picture is basically unsupported all the way back to the tool post diameter , and then is only sitting on a thread.

Phil:)


I've been using a "threaded sleeve" design as described by Mcgyver for the last few years. Somebody posted this idea on "the other" site, and I made a copy for myself. Here's a pic of mine in use.

http://img.photobucket.com/albums/v280/jasch/Metalworking/Tangential%20Tool%20Holder/ToolInPos-001.jpg

I like it much better than the half-moon key and washer that it replaced!

Jim

MrFluffy
03-22-2013, 07:04 AM
I have a lantern toolpost setup as above, from I believe a schlaubin lathe which used that design ex factory.
I also had a tripan 111 qctp, and they're so small and elegant I've never had a issue with it that the lantern would solve so have never mounted it.
But, I've recently sold the tripan and its holders on as I found I wasn't using them either, as I now use a great big hulking beast of a multifix B, but Ive found with a little cunning I can use its rotational indexing to get round clearance issues without pain or readjustment. For a while I kept it and made a holder so I could hold the tripan in the tool holder of the multifix for extra weird setups, but never used that either.

I'd never go back to a traditional four post though if given the choice. Dont the lanterns have issues with clearance from the corner of the top slide in use as they sit central on the compound slide not hold the tool off towards the edge?
I think people are down on the lantern type toolposts because with the onset of qctp's the lantern cures a niche itch thats gone away, but if you want to use a lantern for the simplicity and for the best reason in the world (because you can) carry on.

MrFluffy
03-22-2013, 07:14 AM
I just dug it out and snapped a pic of it to contribute to here, no my fingers are not especially giant, its off a small precision schlaubin lathe originally.
http://gallery.pipandphil.com/d/38162-1/lantern_tp.jpg

Mcgyver
03-22-2013, 08:52 AM
I just dug it out and snapped a pic of it to contribute to here, no my fingers are not especially giant, its off a small precision schlaubin lathe originally.


Perhaps they where the original designers of this....Shlaubin are something aren't they? note the chamfered thread ends. German & Swiss, that's where the quality is :)


A four way tool post is sitting block of iron on block of iron, with no overhang in the toolpost and absolute minimum overhang of the cutting tool.

its not either or imo....each would have occasion to shine.

1-800miner
03-22-2013, 09:03 AM
Also notice that they used buttress threads to bear the pressure.

philbur
03-22-2013, 09:21 AM
Also notice that it is from a watchmakers lathe, used for processes where hand held tools are often rigid enough.

It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.

Remember the question was "Why does everyone get so down on lantern toolposts?" Not "does a lantern toolholder have a place in the home workshop?" I think the answer to the question is that they provide insufficient rigidity for use as a general purpose holder.

Phil:)

metalmagpie
03-22-2013, 10:47 AM
To anyone frustrated with height adjustment on 4-sided tool posts: buy cheap sets of feeler gages and take them apart. Now you have a whole bunch of nicely made shims.

metalmagpie

Edwin Dirnbeck
03-22-2013, 10:48 AM
When I was a youngster ,I used a rocker, lantern toolpost for about 10 years full time in a high pressure job shop setting.I swore that some day I would hunt down the guy that invented this abomination and destroy his decendants .These things are an abomination to use and should be thrown in the trash.However I am better and over it. laugh laugh rant over.

MrFluffy
03-22-2013, 11:17 AM
Also notice that it is from a watchmakers lathe, used for processes where hand held tools are often rigid enough.

It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.

Remember the question was "Why does everyone get so down on lantern toolposts?" Not "does a lantern toolholder have a place in the home workshop?" I think the answer to the question is that they provide insufficient rigidity for use as a general purpose holder.

Phil:)
No its not, its from a 102 which schaublin denoted a toolmakers lathe, lathes.co.uk has some shots of the range showing the arrangement they had :-
http://www.lathes.co.uk/schaublin/page2.html


I draw you to my above comment that I dont use this toolholder anymore as I use my multifix b to do everything it can do and more.

MrFluffy
03-22-2013, 11:20 AM
Also interesting to note that the 102 in the later photo's on that page has had its lantern replaced by a tripan 111 qtcp :)

Arthur.Marks
03-22-2013, 11:29 AM
It would be interesting to see a photo of the air gap underneath the height adjusting nut when mounted on the slide.
That is true. The design essentially creates a bridge with either end as supports and the holding pressure bearing down directly in the middle. Usually it doesn't matter, but you can deform a 3/8" square shank if you aren't aware. I still use it on occasion with a disproportionately taller shank toolholder:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/oldsvt_zps087fb33b.jpg

Schaublin later updated the design to eliminate that problem with two hold-down bolts. They then aligned directly above the knurled height-adjustment nut:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/newsvt_zpsc86d2076.jpg

And parts assembly:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/newsvtep_zps051cbe5b.jpg

http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/newsvtep1_zpsa16155a0.jpg

FWIW ;)

Jim2
03-22-2013, 05:28 PM
I assume under the adjusting nut is nothing but free air. The adjusting thread is only seated as well as the clamp bolt is tightened, apply some more load when cutting and the thread may adjust its seating.

A four way tool post is sitting block of iron on block of iron, with no overhang in the toolpost and absolute minimum overhang of the cutting tool. Apart from a relatively thin adjusting nut the tool in the picture is basically unsupported all the way back to the tool post diameter , and then is only sitting on a thread.

Phil:)

Hey, you think that threaded ring has problems--you oughta see the lathe underneath it and the operator turning the handles! The new VMC won't be here 'til next month though, so we just gotta get by 'til then, LOL. . . .

Jim

ptauser
03-22-2013, 07:00 PM
Hi folks, I use small and large watchmakers lathes and will not use lantern tool posts for fear of ripping out T slots. This is real expensive. The suggested cures are not acceptable. If you replace the button on the bottom with a T, it is integral with the top part, and cannot allow the tool post to rotate. If a T is threaded to the top part, every time you rotate it the tool height changes (not a lot with a fine thread , but it matters in watchmaking)
Dave.

macona
03-22-2013, 07:46 PM
Why does everyone get so down on lantern toolposts?



'Cause they suck.

tdmidget
03-22-2013, 08:07 PM
'Cause they suck.

+1 on that. And those of you who love them so, don't even know the proper name. It's a "ring and rocker" toolpost. If lanterns had been as bad as these POS, the light bulb would have come much sooner.

Gary Paine
03-22-2013, 10:09 PM
If a T is threaded to the top part, every time you rotate it the tool height changes (not a lot with a fine thread , but it matters in watchmaking)
Dave.

Dave, If the T is essentially a shaped washer and a shoulder bolt from the bottom engages the lantern post, this is not the case. The tool height does not change with rotation. Instead of a shoulder bolt, I have also used a blind hole and fine tuned the engagement to a slip fit with the T-slot by putting just the right amount of lead shot pellets into the hole and tightening it up.

ptauser
03-23-2013, 09:11 AM
Gary,
My Lorch KD50 has a 2mm T slot. I don't think this leaves enough room for a washer and a shoulder bolt.
Dave.

tdmidget
03-23-2013, 11:10 AM
Gary,
My Lorch KD50 has a 2mm T slot. I don't think this leaves enough room for a washer and a shoulder bolt.
Dave.

What? You have a T slot less than .080" wide?

ptauser
03-23-2013, 01:37 PM
What? You have a T slot less than .080" wide?

No, tmidget . It is 6mm wide at narrowest, 10mm at widest. The important measurement in this context is the button size at the base. It is 2mm thick x 10mm diam.