QCTP

[Howard LewisParticipant @howardlewis46836]

Bear in mind that once you buy a particular QCTP, holders from other maunufacturers / suppliers may not fit your basic toolpost, so once you have a system, stay with it!

QCRPs were inventef for industry where time is money.

The advantage is that once set on centre eheight, the tool should stiil be there, the next time that you use it. Useful if you do a lot of tool changing, but less ential (or cost effective) if you use three tools or so, which you can do in a four. Having a rear toolpost,can increase the number of tools available;

So think carefully about these points before you spend money

(We probablly, all have items thast we bought, as “A good idea at the time”, that we never use!)

Howard

[JasonB]

On JasonB Said:

I would have thought a QCTP with a ratchet or index pin is as quick as a ratcheting 4-way and then when you need an additional tool it will be even faster? You also get length ways repeatability when changing a QCTP, shimmed or milled holders will only go back in at the same height not position.

Much like my thinking when I came up with this: http://www.charleslamont.me.uk/iqc_toolpost.htm

[JasonBModerator @jasonb]

I was thinking of the Colchester size Dickson type posts that take 3 holders and have an index pin, similar to yours but with two more holders. And lets face it you can often only get 3 tools into a 4-way particularly if one is a boring bar and just hope you don’t need tailstock support which may mean removing tools to get clearance. Same clearance issue applies to a QCTP in many cases though quick to change to an extended holder when needed.

I suppose those with rigidity problems could take Charles’s design a step further and make the other sides slotted to take the commonly used tools like a 4-way and then just have the one simple dovetail profile for changeable holders  so you could keep a range of tools ready to go in their own holders.

[VicParticipant @vic]

These tools cater for about 95% of the stuff I do. Two Tangential Tools, one bought, one home made. Two carbide insert tools in 12mm holders, both with 2mm gauge plate glued to the underside. A 16mm shank TNMG tool which I trimmed down by 2mm to fit my four way. And a parting tool onto which I bolted a piece of gauge plate to bring that up to centre height.

I also have a boring tool somewhere also set to centre height.

 

One of the whole points of Carbide inserts is that fitted to the correct toolholder, on a suitable lathe, you never need to bother about height setting.

Not my words but someone else: “The problem with a QCTP is that once a tool is fitted to a holder you’re loathe to remove it for another one”. As a result you quickly end up investing in lots of tool holders, many of which don’t get used very often”.

If of course you grind a lot of custom HSS tools then I can see the justification, particularly if you’re a professional and every second counts.

[DiogenesParticipant @diogenes]

..a professional and every second counts?  -no, but perhaps have better things to do than f*nny about with shimstock and araldite during the <two decades that remain..

[VicParticipant @vic]

Another bonus for me is having two tools mounted at once. Often a turning tool and a parting tool. Simply rotate the tool post to use the other tool. I should really have made a three way tool post like some others as this would be even better.

[JasonBModerator @jasonb]

Depending on the QCTP you can also have two or three holders mounted so it is possible to rotate the post to change tools.

If the job suits the way two holders leave a “cut out” where they meet you can have two tools set to work on the same part, quicker as you do not need to rotate the toolpost, quicker as you don’t need to change holeders and quicker as you don’t have to wind the cross slide a long way to bring the rear mounted parting tool into position.

Set up here to do two ops in one, face and profile.

 

[VicParticipant @vic]

I wasn’t aware some QCTP could hold more than one tool at a time. 😉 the ones we had at work were single tool only as are all the hobby size ones I’ve seen.

 

[JasonBModerator @jasonb]

Myford size Dicksons have taken two holders for years, Mine must be 40+yrs old. When you come up in size they take 3 holders and still within the “hobby size” machines like the Colchester mentioned by another poster. Even RDG do one for the little Unimat 3 that takes 2 holders

https://www.rdgtools.co.uk/product-category/quick-change-toolpost-sets-and-holders/quick-change-toolposts-complete-sets/

[John HaineParticipant @johnhaine32865]

The problem with being able to rotate them is losing the tool offset. Mine came with a hole drilled in it for a locating dowel, or at least an anti-rotation dowel.  The block is set up carefully aligned with the lathe axes before drilling a matching hole in the supporting block (I don’t use the topslide). Then I can measure and apply an offset for each tool which shouldn’t change except when the tool is sharpened.  Over the years I’ve acquired quite a few holders surplus, more than I need.

[James AParticipant @jamesalford67616]

Thank you, everyone, for the advice and suggestions.

As nobody had direct experience of the tool post that I posted in my original link, I thought that I would buy one to assess. As it was from Amazon, I knew that I could return it easily should the need arise. It did.

The post came with four tool holders, all of which were decent, solid steel and nicely made. The central block and locking mechanism, however, were less good. The dovetails on the aluminium block were a lot smaller than those in the holders. Although the piston in the block pushed these out firmly, holding them up to the light showed that the contact area was not that good. The piston was also quite small.

The eccentric locking mechanism worked well enough, but needed very little effort to undo, making it uncertain whether it would hold in use.

Finally, despite having two dovetails on the block, it was badly designed and only one could be fitted at a time.

It has gone back and I am waiting for a different style from Warco, as suggested, to return to stock to buy in a couple of weeks.

James.

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