Chester DB10VS – Which QCTP ?

[JasonBModerator @jasonb]

Though with the right tool for the job in a QCTP there is no need for skinny revolving ctrs, DCGT will provide pleany of clearance and allow turning 2.5mm dia with a standard ctr

And for those that still want to use HSS, then a suitably ground tool and QCTP holder will allow similar size work with a standard revolving ctr

 

[RobinParticipant @robin]

Why does everybody else’s lathe always look better than mine?

I think it’s all clever camera angles and keeping it clean 🙂

Robin

[Howard Lewis]

On Howard Lewis Said:

CHG is easy to make

 

It is, but is it really worth spending any time on one?

 

I use a digital height gauge, ‘calibrated’ by turning a piece of stock to a known diameter, and measuring its height from all the positions likely to be used. Subtract half the diameter from those heights, and put a label on the machine listing the new numbers. Any new tool can be set to height in seconds, usually without disturbing any work in progress and the gauge can still be used to mark out any work in the chuck.

 

I consider the QCTP to be the best value I’ve spent on any tooling since I bought my first lathe over twenty years ago, as it’s used every time the machine is switched on. If I ever buy a bigger machine, the cost of installing a different QCTP will be considered an essential part of the price.

[Clive FosterParticipant @clivefoster55965]

I’ve long felt that the D series inserts are a better general purpose choice for Home Workshop and Model Engineering than the W or C series often advocated. As Jason says access is better and a typical home worker can’t really exploit the extra strength of the bigger inserts. The extra corner of a W series may be more economical I suppose.

I do larger work and went for C series to handle the jobs that needed inserts many years ago for reasons I no longer recall but presumably made sense at the time. Probably cost and availability as W were somewhat premium in those days. Over the years D series have gotten much more robust and capable so if I did a do over right now that’s almost certainly the way I’d go. But HSS would probably still be my workhorse.

Given the relative costs of modern inserts against the expense of a proper set up to grind HSS, something rather more workmanlike reliable than a cheap import bench grinder with iffy tool rest, its arguable that its fiscally viable to go all in on inserts from the beginning. Most especially if you cheap out by going DIY block switching rather than paying for a QCTP with a sensible number of holders. Insert carriers repeat so well that there is no need for the, expensively provided, height adjustment ability of a QCTP.

Jason’s second picture shows an extended toolholder. Sometimes a necessary evil but absolutely not one of my favourite things. (I’ll go a long way with workarounds before digging mine out and blowing the dust off.) The tool tip inevitably has to divine its support at considerable distance which offends my engineering sensibilities.

But without an extended holder you can run into this sort of problem where the tailstock barrel needs excessive extension to clear the tool post block. It may be instructive to compare this picture of a D series insert and revolving centre on my small lathe with Jasons similar offering above. Clearly shows the effect of different combinations of components. Jason needs far less tailstock extension than I, he can actually use rather less than in his picture.

As shown my Smart & Brown 1024 needs 2 1/2 inches of extension to clear the Dickson S2 block with a D series insert carrier pulled right to the back of its holder. Poor practice as the clamp bolts aren’t central. With other tooling approaching an inch more may be needed. The hefty 1024 copes just fine but many smaller machines don’t have the tailstock strength or barrel travel.

This sort of clearance issue is easily overlooked during purchasing leading to unpleasant surprises later.

Similar issues can arise with a 4-way block.

As ever the are workarounds. This sort of thing is one reason why a Dickson has 3 tool carrier stations.

The never to be sufficiently cursed American lantern tool post does have the benefit of slimness in such situations. Probably why SouthBend and other American makes think that 2 or 2 1/2″ of tailstock travel is fine.

A nice benefit of having plenty of tailstock barrel travel is the ease of aligning the QTCP or 4 way block with the bed by simply touching a suitable carrier to the barrel. I actually found a use for the MT drill carrier block that industrial Dickson sets usually come with. Yay, go me. It also carries a gash Jacobs MT arbor to use a workstop when setting material extension doing collet held repetition jobs.

Clive

[Howard LewisParticipant @howardlewis46836]

Nick,

I use my C H G every time after grinding a tool, and I suspect that it would still be needed with HSS  tools held in a QCTP.

So, in my book, time well spent. We may not be on piece work, but why spend time shimming / adjusting when you could be productive, cutting metal?

But, each to their own.

Howard

[JasonBModerator @jasonb]

My usual inserts are the “C” type and I have holders so can make use of all 4 corners. The DC** only tends to get used when the tailstock is in use and only then on small dia work or getting down the inside of the web on a crankshaft, etc.

One other thing to remember with QCTP is that the tool goes back in the same 3 axis not just the vertical one that say a tool with shims stuck to it would in a 4-way. So even if doing 2 or 4 items which is not uncommon you can use your handwheels or DRO for each part as you swap back and forth between tools.

Although like Nick I know my ctr height I only really use it when shiming up work on the cross slide. Don’t have  a home made gauge or use a height gauge when setting the odd tools that don’t have their own dedicated holder.

[Author]

Posts