Calling all Advocates of the "Lammas" 3 way toolpost...

Hi,

I was reading through one of the back issues of MEW, may have been the 25th anniversary edition and noticed the hubbub surrounding David lammas article on the 3 way (as opposed to 4) toolpost.

Obviously a quick change tool post is alot more fiddly and expensive, a way that i've been happily using for a while now ontop of my compound slide.

All of the engagement and movement between these parts made me wonder if this was really a good way to hold a tool after all? some people have remarked on the noticable improvement on cutting once having done away with the compound slide and gone with a rigid bolt down system.

Don't get me wrong, i certainly don't miss having to shim up the tool to centre height with the 4 way i once started with, but how much of a fighting chance did i give this system before i switched to what i thought would be better, QCTP system? probably not much, if it was possible to use all the available positions and put the setup into each once, it's conceivable i would have a tool system thats "quicker than a quick change".

In order to do this it said in the magazine than you can buy castings from "black gate" was it? which is much less effort than carving it from solid and apparently they go fairly cheaply, conceivably you could buy 3 of these monsters and have 9 different tools all setup and ready to go.

I just wondered, A: is there any truth behind this compound slide rigidity myth and B: has anyone given the 3 way a good shot and got more to say on it than me?

I'm contented with my current tool system but sometimes look over the fence and think "is there something i'm missing?", is there an opportunity to be had? as all humans do.

Michael W

Firstly, it depends on which lathe we are talking about and what you are trying to turn,.....ALL lathes flex to some degree as it's simply the laws of physics at play. However, some machines are better than others as most of us here know only too well.

As a basic 'truth' smaller lathes tend to provide a better finish once the top slide is removed and the tool (mounted in a decent block of steel) can unload the turning loads and leverages as directly into the bed of the machine as possible.

The big advantage of the lammas post is that it offers greater ease of space on smaller lathes along with (fairly) quick change. Smaller lathes (in my experience) are not as good with a four way as are their larger cousins.

I use a homebrewed toolpost that mounts direct to the cross slide for all turning except tapers and some screwcutting. Both more rigid than having a topslide in place and on smaller lathes it just makes more room to move between toolpost and tailstock etc.

As far as shims go, I just can't see any big objection to them. I have a pile next to the lathe and with a bit of practice can pretty much look at a tool and know how many shims it will need.

But you should be able to make up some kind of block of steel or cast iron to replace your top slide and mount your existing QCTP on the top of it, thus having the best of both worlds. I fabricated my block out of a couple of scraps of 1" plate welded together and mounted a small 4-way toolpost turret from a boot sale on top of it.

Edited By Hopper on 31/03/2016 12:38:57

Edited By Hopper on 31/03/2016 12:54:57

Your challenge today is to design the 4-way toolpost that is a quick change cartridge you can swap out for another 4 way set (i;m guessing someone has already done that)

The idea of a quick change toolpost is to have enough holders to cover the tools that are used. That can get manic.My boxford came with 12. I reckon I could manage with less but even then it does add to the expense.

If a set of indexable tipped tools such as I mentioned recently are used always with the same style of tip the centre height should be pretty constant so they can be changed easily.

All lathes have a certain centre height above both the top of the cross and the compound slide. The most usable one in most respects is above the compound. A certain size of tool may come out correctly or need a bit of packing. I know of one person who makes his own tangential tool holders. The top of them is at centre height the area around the actual cutter is lower so setting them is just a case of placing them on a flat surface and allowing the tool tip to rest on it. With more complication the same sort of thing can be done with holders that carry ordinary toolbits at an angle. That style of tool holder can be massive on just about any lathe if the toolpost is removed. It can also be of an adequate size on larger lathes - needs more than 1" available in the usual 4 way holder. I've always centred this type by trapping a 6" rule between the work and tool tip and adjusting until it's vertical. May need doing again after the 1st cut has been taken but I generally settle work pretty closely in 3 jaws.

I find rigidity and finish is mostly dependent on slide adjustment. Also cut size and feed rate on a lathe with some wear. Things flex and move and the general idea is to arrange for the cut/feed to keep things firmly were ever they have gone too. This is likely to be far more difficult on many of the new smaller cheap lathes that are about down to other factors as the load on the machine is increased to do it. In that case mounting directly on the cross slide might help.

The 3 way ? The main idea was to keep the toolpost itself out of the way so that it couldn't foul on various things even when angled. I single tool holder might well do a better job of that.

John

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Michael,

I don't [yet] have one, but I have admired the 3-Way from afar ...

To my mind, its biggest merit is the ergonomics; the out-of-use tools look to lie in much safer orientations.

MichaelG.

Yep! Well two way actually 'cos 4 way fully loaded is too much like a porcupine for my tastes.

Promised Neil I'd do a write up of the concept a few weeks back but its been delayed due to me being squashed flatter than a steam rolled pancake for a month by this years flu bug. Having finally crept back up to periscope depth it doesn't seem to be working as a short concept contribution. Be different if I had pictures for a "look what I did" article. So I need to do a long version covering all the related things it grew from and uncovering ideas I'd not thought of before I started. Once thats finished I can haul a simple short form out and we shall see which version Neil likes.

Getting back to the Lammas tool post screw and glue construction from standard plate and bar sections works as well as a casting or carving from solid for this sort of thing. Build up is easier with two and four ways than with three. Less sawing down to size and shape. Made a 4 way in that style "not telling you how many" years ago.

Shimming is much easier if you set up to measure the tool tip height from its bottom off the machine. Then its just matter of selecting the right shims and spacers from stock. Colour coded plastic shims such as RS 681-407 **LINK** make life easier. As does arranging your tool grinding methods to take known increments off the tip height so you don't have to find really thin shims. Going down in 10 thou / 0.2 mm steps or even 20 thou / 0.5 mm steps rather than grinding just enough to make it sharp probably won't much affect tool life.

Clive.

There was a time when the 'Lammas' toolpost was regularly commented on favourably by ME contributors.

I suspect time, the advent of the readily available QCTP and several straightforward designs have all eaten away at it's popularity.

It works better than a 4-way, no doubt, but quite whether is solves all the world's ills quite as effectively as Dave claimed in his article I leave others to judge.

As for top-slide versus a simple raising block, it's indisputable that the latter is more rigid but a well adjusted top slide works fine for most use. It's irrelevant whether you have a QCTP, four-way or Lammas toolholder as you can fit any of them to either type.

Neil

My compound slide came off when I added CNC to my lathe. It became redundant and just complicated things if left in place. I never noticed if there was a change in rigidity.

Martin

I made a mini version of the Lammas toolpost for my Unimat some years ago, and this was subsequently published in the ME. For a tiny lathe like the Unimat there is something to be said for it. I had already made a four way toolpost for it but found that it got in its own way too much. There was a QCTP available when I bought the Unimat, but for the price I could have had another lathe. I would agree that you want about a dozen or so holders for a QCTP, I have about that many for my Myford.

One feature of the Lammas post is that you can really only turn towards the chuck. If your job requires something like turning towards a shoulder at the tailstock end, the toolpost will tend to foul the tailstock, assuming you are using it to support the job. That can be avoided by doing the job between centres and turning it around when necessary. However a lot of guys look very blank when you suggest things like turning between centres. I suppose you could make two bodies for the Lammas, a left and a right, and should be able to interchange them and still index to the same position.

John

Michael,

In this area you will get nearly as many opinions as there are ME's. As usual when discussing these things, the size of lathe and type of work being undertaken is rarely mentioned. There are many here who will advocate QCTH (and how many 'dozen' holders you need) and I'm sure that many find them very convenient. But the fact is that the good quality QCTH system can be quite expensive, especially if buying multiple holders.

This debate has raged for many years but I think it is interesting that most of the "Gurus" of model engineering (GHT, Tubal Cain, Ian Bradley and others) advocated simpler methods for the "amateur". Of course these were different times (and different pockets)

On my Super 7 I still mainly use 'single' tool holders, machined many years ago from castings that CES used to sell (which they unfortunately do not sell these days). My first QCTH was a Chinese economy version that came with my 2.5" EW lathe - and I now know it was one of the reasons that I struggled to get good work out of the EW initially, because of excessive tool overhang.

For some time now on the EW, I've routinely worked without the top slide fitted - using instead a simple steel mounting block directly on the boring table. This has improved things generally but the QCTH is really still a bit too big and I only had a few tool holders (so had to swop between my brass and steel tooling). The question became - do I 'invest' in more tool holders or look for a different solution?.

I went through my old ME/MEWs and looked at all the tool holder designs I could find. I was thinking of making smaller versions of the CES type holders (there have been several similar designs published) when I read a set of articles by Dr RM Rose (ME in the 70's). He advocated a very simple tool holding block and stated why he felt they were ideal for his kind of work.

I cannot report on the truth of his views just yet but the material has been purchased and a number of 'blanks' machined to size. Once I've opened up my 'summer' workshop - the shaper will make short work of the rest. I will use different holders for my brass and steel tooling, as well as make some specials for boring bars and parting tools.

To go back to my original point, I am making these holders for a 'small' lathe - which is generally used to make 'small' things. I do not require a production environment as most of my work is one-off. So Dr Roses solution will (I think) suit my EW needs very well. They clearly would not suit everyone.

Regards,

IanT

If you are thinking of removing the top slide then have a look at the " Gibraltar " toolpost. in ME index. Cant remember if it was GHT or Tubal Cain but I'm pretty sure castings are still available - Hemmingway possibly ? doesn't get round the multiple tool issue but certainly provides good rigidity for smaller lathes eg myford etc.

Bumping this thread from 2016, because it may be of interest those who were following a recently ‘lost’ one.

MichaelG.

As I obstinately stick with my four way because as in the "lost" video thread I find it quicker and easier than a QC to use, I have considered a Lammas 3-way. But when I discovered you need a left had and right hand version to change between things like a turning tool and a boring bar etc, I stuck with the faithful 4 way.

As I said in the "lost" thread, I have machined the Myford 4 way so a standard 10mm indexable tool fits straight in with no shim needed. Then if I use 3/8 HSS tooling I know it needs one of my standard thickness shims under it, plus another if the point has been ground a bit low. Flipping a toolbit upside down on the bench and sliding a shim or two under the tip soon tells exactly how many are needed. But as I use the same tools over and over I know which ones need how many shims. And tend to store the bits with their shims with them ready to use.

I have also machined a couple bits of 10mm key steel into an L cross section just right to hold a piece of 1/4" HSS at centre height. Very handy as the smaller bits are quicker to grind and cheaper.

But for the most part, using standard 10mm insert tooling, no shimming needed.

Plus I like the fact that the 4 way cuts tool overhang down to the absolute minimum.

The Gibraltar was Tubal Cain's.

As has been said, it depends... The Myford Super 7 topslide, with Dickson QCTP is not a rigid set up, and using a parting tool in it can be hair-raising.

To add to my Emco comments in another post: the Emco QCTPs offered for the U3 and Compact 5 are a poor design. The mating faces are tangents to a circle, and their included angle is too large, resulting in very poor kinematic location about a vertical axis. I think Harold Hall's design, with a little tweaking, looks like an excellent, and easily made, QCTP design. One day...

My upside down rear toolpost lazy man contribution

Always on centre, just slide it in (ooh)

Always interesting to see your old posts pop up here.

I still use 'Rose' blocks on my EW but the holding arrangements have changed very slightly over time. There is now a restraint on the rear of the tool holder to stop the tool block moving under cutting pressure (mainly happens if the block's base isn't flat). The top part of the tool holder can also be angled by removing the cap screw - but it normally holds the tool blocks at right angles to the lathe axis (or face - tools can be clamped in two positions). So very simple to make tool blocks and easy to use. Not for everyone perhaps but the original QCTH is now only used for a few tools that can't be fitted to the blocks.

Regards,

IanT

PS Keep meaning to make a lever replacement for the large clamping nut but it never quite seems to get to the top of the round TUIT list....

I use this triangular toolpost, which can be also used by mounting the circular spacer block beneath the triangular toolholder and the spindle run in reverse (if it is safe for your lathe to cut this way) I think it gets a slightly better finish this way.

Alan

Edited By Alan Jackson on 17/06/2023 17:48:23

Edited By Alan Jackson on 17/06/2023 17:49:07

From a design point of view, the three way has advantages over the four way. The Smart & Brown model A at the museum has a four way as standard holding 20mm tooling reduced in height to 17.53mm to eliminate the use of shims. The tools are too long to hold four without far too much overhang, and the toolpost that I made for the second brand new compound that I bought on ebay is a two way because of this. A three way would not have the length limitations of the four way. One remedy possible would be a larger square for the four way, but that would suffer from overhang and increased flexibility. I have a larger four way toolpost, but that is used directly fixed to the cross slide for rigidity and primarily intended for boring bars up to 32mm.

At the moment I am finishing the longer improved cross slide for the Atlas 12 x 36, and although I had bought some 12mm tools for it, the slightly lower design for the compound to sit on will exactly fit the same tools that the S & B uses. We will make some thicker shims for the 12mm tools.

No wonder. 20mm tooling is massive for a lathe that size. Ship's crankshaft machining stuff. I'd be tempted to use 12mm and fit four in more easily.