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Alternative to a QCTP?

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Martin Cargill02/02/2019 21:06:33
95 forum posts

I have recently acquired some old forks for forklift trucks, with the intention of making a QCTP and holders for my Viceroy lathe, I have cut the best sections out of the forks and milled them square/flat ready for further work.

I have stopped work as I have just had a thought. Is there any mileage in making, say, six (or more) standard four way tool posts and simply swapping the complete tool post over instead of swapping single tool holders. I realise that I would loose the ability to have height adjustment, but as all of the tools would be permanently mounted in the tool posts then they would be packed permanently and would not need to be altered (apart from changes caused by tool sharpening).

Any thoughts?

Martin

Mick Henshall02/02/2019 21:54:36
473 forum posts
28 photos

Hi Martin, I made a QCTP to Harold Halls design with 12 toolholders, prior to this I made 4 two way toolposts which I use for boring bars and a holder fot dti for use with 4 jaw chuck, these are just as quick to change over as the qctp ones, I made them 2 way rather than 4 way as I could never fit 4 tools satisfactorily in the 4 way,they were made up using stock materials rather than milled from solid, tools set at centre height no problems, go for it I say

Mick 🇬🇧

Clive Foster02/02/2019 22:42:47
1581 forum posts
45 photos
Posted by Martin Cargill on 02/02/2019 21:06:33:

I have stopped work as I have just had a thought. Is there any mileage in making, say, six (or more) standard four way tool posts and simply swapping the complete tool post over instead of swapping single tool holders. I realise that I would loose the ability to have height adjustment, but as all of the tools would be permanently mounted in the tool posts then they would be packed permanently and would not need to be altered (apart from changes caused by tool sharpening).

Any thoughts?

Martin

Lots and lots of mileage. Pedal to the metal and go for it! A vastly superior way of going about things.

Some years back I put a fair amount of thought into making this sort of system work really well having found the simple swap 4-ways system to be OK but ... on my SouthBend Heavy 10. Got as far as proper concept drawings awaiting dimensioning for the lathe they were to be used on when workshop upheavals and "new to me" industrial sized lathes bought in three Dickson posts and an adequate number of tool holders so things never went further.

My conclusions were :-

Simple screw and glue built up construction from stock sizes is sufficiently strong and easier than milling from solid

Better to make two way blocks rather than four way. Narrower with less of the "sharp points with aggressive porcupine attitude" problem. Essential to arrange some sort of indexing so the blocks always go back in the same place. Can be a proper face spline index as used on industrial quality machines or just a simple pin dropping into either one hole in the slide or several holes in a thick washer style base. My top slides live almost permanently at 25° giving good handle clearance and instant readiness for screw-cutting by the zero-to-zero method so I'd only provide one index hole.

Swopping is a lot faster if you can have a quick release system. When I planned my system I concluded that the most home shop builder friendly system was to make the tool post "stud" free to rotate with a cross drilling for a tommy bar arranged to engage in a hollow castellated nut screwed into the top of each tool block. Once the nut was set for height around 1/3 rd of a turn of the tommy bar would release things enough so the bar could be withdrawn and the tool-block exchanged or rotated to bring the alternative tool into play. Theoretically interrupted threads could be used but they are hard to make. Cam style locking would be nice but packaging isn't as easy as you'd hope and I'm sure the design is a lot more subtle than it looks if things are to hold reliably. I lusted after the up'n over handle used on some Holbrook 4 ways but couldn't figure a way to make it without needing a handle on every tool block which was way too much work. I planned to have 16 or so tools up and ready to go.

If you are interested in taking the idea forward Neil was kind enough to publish concept drawings with accompanying letter in MEW a couple or three years back. Or PM me as I'm sure I have the masters on the computer.

Do make proper arrangements for tool mounting and setting off the machine. Preferably by direct measurement. Much faster to shim if you have a measured value to work with and a sorted selection. I planned to fit an elephants foot to a spare, rather un-wonderful, dial gauge and dedicate it to the job. If you always set the projection the same you can interchange blocks without needing test cuts to verify settings.

Not making off the machine tool setting arrangements was probably the biggest OK but ... item when I was simply swapping 4 ways on the SouthBends. Closely followed by no proper indexing. The Southbend Tee slotted cross slide made for swift interchange but repeatable positioning was tricky. I faked up some on machine templates which I could get along with but objectively they were unsatisfactory.

Clive.

 

Edited By Clive Foster on 02/02/2019 22:44:19

Edited By Clive Foster on 02/02/2019 22:45:44

Mick Berrisford02/02/2019 23:15:10
114 forum posts

I decided to go for extra 4 way posts instead of a QCTP. Didn't make them though bought a couple of Boxford ones from RDG for my Chester DB10. Ideal size apart from being a touch too high, but had plenty of meat in the base to mill a bit off the bottom to get them just right. Prefer to just swop loaded ones over instead of a QCTP when other tools needed. Will probably get round to making some 2 way ones when I get chance.

Clive Foster02/02/2019 23:20:22
1581 forum posts
45 photos

Martin

Looking at the Viceroy pages here :- **LINK** I see they used a Tee slotted top slide like SouthBend. So you could take the same approach as I did with my SouthBend by making complete tool post, Tee-nut, stud and handle sets. Simply releasing the handle by a half turn was allowed my assemblies to be easily slid in and out. Memory says I used M12 threads on the stud.

The bottom picture on the page linked to above shows a compact and rather nice two way post. The Viceroy top slide is nicely flat, unlike the smaller, mostly curvy, SouthBend one, and that tool post has a bit of space round it. You may well find there is sufficient room to arrange an effective, easy to use, location angle template / stop system so that tool posts of similar size can be swopped around and always slid back to the same position. Possibly a round skirt at the base of the tool post with a set of cut outs or drillings at suitable angles sliding up against a part circle stop with s pin or projection arranged to mate with the cut-outs or holes would work. Pin probably better as it could be removed when needing an unplanned angle.

My experience with the SouthBend was that the template / stop system was sound in principle but impossible to execute in a properly satisfactory manner on the Heavy 10. Hence the rotating stud concept.

A system like this is an ideal home for a Geo. H. Thomas boring bar system with eccentric height setting sleeve. With a bit of low cunning you can also squeeze in a rather larger, stiffer, boring bar than conventional tool posts can carry.

Clive.

Vic02/02/2019 23:42:49
1935 forum posts
10 photos

99% of my turning is done with one of three or four tools, a Tangential tool which is height adjustable itself anyway and a parting tool and a couple of insert tools. I have glued or screwed ground flat stock to the underside of the tools so they are permanently on centre height when mounted in my four way tool post. This increases rigidity on my lathe and means I don’t need to make or buy lots of tool holders. One job I need to do is make an on centre holder for my boring bars. For the last insert tool holder I bought I purchased the 16mm shank model and just milled a bit off the bottom until the insert was on centre height. Another advantage in my small workshop is the tools take up much less space than having them in holders and they can’t loose their height adjustment.

John Olsen03/02/2019 00:25:58
928 forum posts
86 photos
1 articles

Have you considered a three way tool post? Sometimes called a Lammas tool post. With three tools, the upside is that you are less likely to snag yourself on the tools not in use. The downside of course is that you only have three tools, but then, if you have more than one holder that is not such a problem. The three way type is a bit more of a challenge to machine, but is a little more compact.

John

Mark Rand03/02/2019 01:16:08
646 forum posts

When I got my original Myford, it had a 4 way tool post. I never could use it fully stocked with tools due to clearance problems and catching on the tools. I found it to be a right royal pain to use.

I made a quick change toolpost to the late, great , John Stevenson's design. This worked very well, but wasn't much faster than using dedicated shims under tools with the standard myford tool clamp. It did have the QCTP advantage of repeatable tool setting.

peak403/02/2019 01:18:44
avatar
694 forum posts
65 photos

I don't use a 4 way, other than when I had one on my little Simat.
I'm with John, if you want to go down that type of route I'm suggesting a 3 way Lammas, though for a slightly different reason.

I'm not familiar with your lathe, but have a look at the clearance on the front of the tailstock. If you're using any particular tool in a 4 way, (for turning towards the headstock) will the next tool, in the 4 way, clockwise foul on the front of the tailstock if you're using it for support? If it does, you've effectively just made a 2 way toolpost, as you can't easily use 2 of the slots.

For my Myford, I went down a different route. Essentially a vertical cylinder bolted to the topside. several solid blocks of metal with a corresponding bore to clamp to the cylinder, and either slotted to accept knife/insert turning tools or drilled to accept boring bars.

Really just blocks of metal bored to suit the cylinder, then split with a slitting saw, and a simple clamping bolt to lock it solid.

A single vertical through hole tapped M6, with a setscrew fitted, allowed for presetting the height for each tool.

Cheap and cheerful, pretty rigid, and it worked/works for me.

Very similar to this, (post 15 second photo) though mine were even simpler, just using a slot, rather than a square hole, or a round drilled hole for a boring bar.

I did also have some carbide insert tipped tools which had too big a shank to fit a conventional slotted toolpost; it would have raised the cutting edge above centre height, if I'd left enough meat in the metal at the base of the slot.

Rather than broaching/filing a square hole, I cheated; I milled a full rebate and welded in some thin angle iron from an old bed frame to complete the other two sides of the square hole.
Hardly conventional, but I was never trained in the "correct" methodology. wink

Bill

 

Edited By peak4 on 03/02/2019 01:21:21

Iain Downs03/02/2019 09:14:38
407 forum posts
212 photos

I've recently replaced my aluminium QCTP (which is rubbish) for a steel one from ARC and I've found the improvement considerable. Parting has even become, if not pleasant, at least more or less doable.

However, I find I still use the aluminium one (it has a boring bar attachment I don't have for the arc one - though I'm making a boring bar which will fit the ARC).

I also have in mind to make a tool post which just does parting. Probably with a carbine insert. I call this FQCTP (Fairly Quick Change Tool Post) as swapping tool posts (even with spanners / hex keys and so on) is much quicker than any machine operations I do.

So I'm all for the Fairly Quick Change Tool Post and have registered the trademark accordingly! £1.50 for each mention in this forum, please...

Iain

Michael Gilligan03/02/2019 09:21:23
avatar
12554 forum posts
545 photos
Posted by Iain Downs on 03/02/2019 09:14:38:

... also have in mind to make a tool post which just does parting. Probably with a carbine insert.

.

Please forgive my typo-spotting, Iain ... But the thought of that brought a wry smile

MichaelG.

.

https://en.m.wikipedia.org/wiki/Carbine

Edited By Michael Gilligan on 03/02/2019 09:22:53

Mike Poole03/02/2019 10:08:20
avatar
1695 forum posts
44 photos

Plenty of ideas being promoted here which I think is the reason to pose the question. My Myford came with a genuine Dickson tool post and I have stuck with it, I now have around 20 tool holders and from some comments made before on this forum this is not uncommon. The Dickson when scaled down to Myford size does I feel lack rigidity but I do like the quick change and only having one tool to look out for. I really don’t feel that using a long or larger boring bar is well suited to the Dickson or probably most QC posts. Probably a good idea to have a Gibralter toolpost and a solid boring bar post to supplement your final choice if you want to take some heavier cuts. I guess that most people are reasonably happy with their choice but if they are completely honest they will have a few minus points, I suppose getting the plus points list as long as possible and the minus as short as possible is going to point the way you go but some of it is going to be a personal choice.

Mike

Vic03/02/2019 10:35:38
1935 forum posts
10 photos

Just because a four way toolpost can mount four tools at once doesn’t mean you need to. As all my tools are fixed on centre height it only takes a few seconds to mount one. I normally only have two in my four way, a turning tool and a parting tool.

Involute Curve03/02/2019 10:44:06
avatar
325 forum posts
84 photos

My new to me Harrison M300 has a QCTP with 8 holders, and rear tool post, I still have the 140 which has both a 4 way and a 3 way plus a dedicated Boring bar tool post and a couple of singles, I am still not convinced the QCTP is the best option, at the moment I think I prefer the 4 and 3 way.

what do other prefer in use

Shaun

steamdave03/02/2019 12:21:18
396 forum posts
33 photos

For many years I used a GHT designed 4 way toolpost on my Myford. In fact, I made 2 - one was to be for non ferrous metals and the other for normal steel turning. Then a few years ago, I fell under the spell of the supposed superiority of the QCTP. In my mind, changing over was the worst decision I made regarding tool holding but couldn't go back because I sold them!

The GHT design was far more rigid, it had accurate indexing and with all my tools pre-shimmed to centre height, it took very little time to change tools when required. Another big advantage was when making multiple parts like special screws, just a spin of the turret and the correct tool was presented.

True, it was only practical to hold 3 tools, but that never was a problem. As has been mentioned earlier, a Lammas 3 way tool post would probably be the perfect compromise. The idea of changing turrets never really happened unless I had a large amount of brass/bronze turning to do.

As has also been said, at the end of the day it is what the individual feels happy with using.

Dav
The Emerald Isle

not done it yet03/02/2019 14:06:28
2581 forum posts
11 photos

A single cutter is likely ideal, from a cutting point of view, as it can be positioned over the centre of the slldes with no overhang - all QCTPs will exhibit some sideways extension or at least have some extra off-centre forces while cutting.

An older lathe, with some wear, might well benefit from the more rigid 4 way TP set up.

bricky03/02/2019 15:10:50
347 forum posts
47 photos

I made a QCT based on an old Pratt Burned one I saw on E bay ,mine has one drawback and that is you have to pack each tool into it's cartridge up to centre height but once done thats it.It has the advantage over my Dixon that the tool cartridges sit directly onto the top slide and the clamp nut is all there is above the toolpost giving uncluttered access to the workpiece.It will fit any lathe above 3.5" by just scaling up.The speed of changing cartridges is quicker than my Dixon.View it on my album.

Frank

Martin Cargill04/02/2019 18:11:04
95 forum posts

Thank you all for taking the time to reply to my post.

Having considered the options that I have, I've concluded that:

1. My original idea of making some four way toolposts is still a valid one, although I will probably use them equipped with two tools. This will depend on how the working clearances pan out. I've considered making three way ones but I don't think the complexities of making them outweighs their advantages.

2. I hadn't thought about the logistics of changing the posts but as my lathe has a "T" slot for holding the toolpost then its probably worth making a bolt and a handle for each one.

3.The toolposts I'm going to make will be from solid blocks (because I have the material) and I have a horizontal mill that will chew them out pretty easily (I have a Victoria U1).

Thanks again for your input.

Martin

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