Video unapproved by the authorities re advertising issues in the past apparently.

Always wondered how the whole QCTP thing got started. It's an inevitably expensive concept due to needing decent engineering and precise manufacture if it is to work well for a useful lifetime. Not to mention system lock in. Of necessity the tool must overhang the support so it's inherently less rigid than simple block sitting down onto the slide.

From a clean sheet of paper perspective it would seem much more economic to make simple slotted block tool posts held down to an indexing base by some form quick acting lock. Either 1/3rd (ish) turn like most QC systems or some sort of lift over latch. Indeed Holbrook at one time made a 4 way system with a horizontally pivoted spade grip handle that was pulled down to latch it onto the face ratchet indexer after turning. Half way to an easy remove system but Holbrook used the usual nut on a stud to hold things together.

Fixed block tool posts were widely used and most industrial English lathes had a well engineered indexing device under the factory four way posts so adding quick release set-up to the block doesn't seem much of a stretch. Given quick release capabilities tool height can be set by direct measurement on the bench so the most objectionable trial and error aspect of on machine shimming is avoided. A simple block with slot(s) must surely be much less costly to make than a QC toolholder.

Maybe 20 years ago I drew out a Model Engineer / Home Workshop friendly version of this concept using two way blocks built up from stock bar and plate sections glued and screwed together. The blocks were to be held down via a hollow castellated nut screwed into the top passing over a rotating tool post stud cross drilled to take a tommy bar sized to engage between the castellations. A partial turn of the tommy bar from tight would allow it to be withdrawn so the block could be lifted off and a different one fitted whereupon the tommy bar could be replaced and things locked with a partial turn.

Some years later Neil was kind enough to publish in the Letters section of MEW a layout sketch of the system as it would have been applied to the SouthBend Heavy 10 I was using at the time of design. Taking the opportunity to step up from the Heavy 10 to a Smart & Brown 1024 complete with a Dickson set up curtailed development. I was never really happy with the indexing on that specific concept but I know how to do it better now.

If you use insert tooling, with its fixed cutting tip height, purchasing a conventional QC system means you are paying lots of money for a versatile height adjustment capability that you will never use.

Clive

Yep, even though the majority of my holders are locked to the height for the tool that stays in them I still have the easy screw adjustment for the couple of holders kept for all the other cutters be they Insert, solid carbide or HSS

Oh and seeing the Lammas tool post mentioned today, I also have a couple of extended tool holders if needed for additional tailstock revolving ctr clearance where a 4-way either means excessive tool stick out if it is not to hit the ctr.

here are the tools used to make the 3 small parts mentioned above that are in the middle of the photo, two brass one stainless. Had I not saw the part off the stainless bar then a second parting tool could be added to the lineup

As we seem to be back to the QCT versus 4 Way Toolpost debate. Perhaps this should be thrown into the mix. I have an original Myford 4 way toolpost and an original Myford QCT set up. Using both, it is quite obvious that the 4 way toolpost is a lot more rigid than the QCT set up.

Andrew.

I have been using Dickson style toolpost and holders on my Myford S7 for years, ever since my apprenticeship and experience in industry. The thought of faffing with shims of varying thickness put me off that route very early on in my career.

However I am well aware that it is not the best toolpost design especially for the Myford, some of my holders never seem to hold the tool height once removed, but it is still quicker to reset the height than hunting around for shims.

Fast forward to now, I am considering changing this style of toolpost to the "piston" style as advertised by Arc Euro as this seems to be a much better rigid tooling system than the Dickson where there is a lot of unsupported overhang.

What do others think about this potential upgrade?, any experience good or bad?

All the best

Del

IanT

I think we are at cross purposes.

I think I'm advocating exactly the same things as you.

Viz

If tool tip height in interchangeable blocks can be accurately and easily set off the machine the sole compelling advantage of the conventional QC systems is the screw adjustment system that makes it relatively easy to set tool tip height on the machine. There is no inherent reason why arranging quick change blocks should be any harder than changing tool holders on a conventional QC system. Whether by your rose blocks, my proposed rotating tool stud or any number of other mechanically satisfactory solutions.

Interchangeable blocks do require an indexing base whilst conventional QC posts can get along without indexing. But plenty of folk regularly shift Dickson and similar 2 or 3 station posts around to different angles without the aid of indexing and the Mulitfix goes to considerable extra engineering effort to include multiple angular settings. It was quite common for industrial users to graft a Dickson onto the indexing arrangement living under the factory 4 way of many makes.

I can't see the extra cost of an indexing base being a significant deterrent.

derek hall 1

The piston post is not inherently better than the Dickson system. Arguably its worse because forces are mostly resolved via the holding piston rather than directly.

In my experience the weak point of a Dickson is that it needs regular cleaning out inside. Mine are positive magnets for itty bitty teeny weeny swarf dust. But it's easy to pop the pistons out and clean. Height retention failures are primarily due to the snail on the locking hex self adjusting the height setting thimble. The lock bolt needs to be tight and the tool holders held in position whilst being locked. Leaving it up to the locking tongue to pull things into position is poor practice. The holder is almost invariably at an angle so the snail rubs against the thimble making upsets more likely. Hamfisted folk can also bend the stud. Which is less than helpful. A quick brush down of the mating surfaces to remove any swarf before fitting is sensible.

Clive