Tool post height

[Martin KyteParticipant @martinkyte99762]

SOD raises indirectly an interesting point in that it is my impression that QCTP's are inherently less rigid than the original 4 way tool post based on the fact it QCTP's have more interfaces between the topslide and the tool tip (one between the toolpost and the topslide and one between the toolpost and the tool holder. They generally have less clamping footprint to the topslide and quite possibly have more overhang although I haven't measured this. In order to be repeatable for tool hight they have to be absolutely clear of swarf especially when machining brass as the hight setting and clamping faces can be compromised and throw everything out. I have to admit to using a QCTP but there are occasions when I have wondered if it would be better to revert to a 4 way especially if the 4 way is in very good condition, indexes properly and has it's tools correctly set. I know industry exclusively uses QCTP's but our lathes are considerably smaller and less rigid in most cases.

I would be interested in comments.

regards Martin

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 07/07/2021 09:52:06:

[…]

I would be interested in comments.

regards Martin

.

‘Less is More’

MichaelG.

[Andrew TinsleyParticipant @andrewtinsley63637]

I have both an original Myford 4 way tool post and a Myford QCTP set up. The QCTP gets more use because I am lazy, but the 4 way tool holder is appreciably more rigid and gets used on the more difficult jobs.

Andrew.

[Alan JacksonParticipant @alanjackson47790]

I entirely agree with SOD and Martin Kyte that the QCTP fitted to a typical small model engineer's lathe suffers from inherant problems, lack of rigidity due to less than perfect fits between the many introduced contact surfaces and increased cantilevered overhang from the support point below. These to reasons alone contribute to more problems than are solved by a QCTP.

Alan

[egaParticipant @ega]

I admit to *not* having used a QCTP but have always thought that an indexing four way tool post is actually *quicker*.

[Martin KyteParticipant @martinkyte99762]

Which brings me to another observation that is often overlooked when the rear toolpost argument starts up periodically. Namely that rear toolposts fit directly on the cross-slide whilst normal toolposts are perched on the topslide adding at least one set of mating surfaces, more if you use a QCTP. Really, when comparing front to back the mount should be similar in order to judge how much improvement rear toolpost actually give.

regards Martin

[Howard LewisParticipant @howardlewis46836]

Re the comment about inserting an End Mill into a Drill Chuck.

Fine if you are prepared to risk the cutter coming out, and ruining the work!

A drill chuck is designed to withstand axial loads, not lateral, and grips on three narrow lines.

A proper chuck for milling cutters, such as ER, 5C or Clarkson, grips the cutter shank almost all the way round, and supports the cutter against lateral loads.

Howard.

[brian jones 11Participant @brianjones11]

I am following the tip given my Pete above and getting a uk set of er20 collets for my DW – why didnt i think of that first – stoopid boy pike

I still have my 4 way tool post but like the way height adjustment is so easily made on a QCTP

I used a lantern tool holder on the colchester at college, what ever happened to them? They were quick and easy

also a JnS drop head holder was good but they are hard to find

I think when I get set up for milling I will skim the top of the combo slide as shown in the video

he made it easily on the ML7. I should be ok on my DW with small cuts.

Funny how you can be so focussed on a problem you dont see the obvious till you come here and a kind soul points to your mistake.

its what we do?

I hope i can make helpful contributions

[Howard LewisParticipant @howardlewis46836]

You probably have already!

There may be others with similar problems, and the thread will, have given them possible solutions, and food for thought.With regard to modifying the QCTP, or the tool holder, my vote would be to mill the underside of the tool holder shanks, but not for the last 12 -15 mm at the tip end.

Removing the minimum of metal will maximise rigidity, to reduce risk of chatter, and maximise accuracy.

A tool, or job that flaps about in the breeze is unlikely to be accurate.

Howard

[brian jones 11Participant @brianjones11]

A real mans tool post Rocker or Lantern? Did Myford ever have one of these?

good thinking

Edited By brian jones 11 on 07/07/2021 17:19:56

[egaParticipant @ega]

The early Myford rear tool post employed the rocker principle.

AFAIK, they never offered a lantern front tool post – best left to vintage American machines.

[Martin KyteParticipant @martinkyte99762]

That's what the Myford boat holders do. They were a form of quick set in not needing shims for tool hight.

regards Martin

[John BaronParticipant @johnbaron31275]

Hi Guys,

I'm not an advocate for QCTP at all having used one and got rid of it in favour of the "Norman" patent tool post and holder. I can use 1/2" inch tools without a problem ! I don't need shims and can set tool height in a fraction of the time it takes to set a new tool using a QCTP. Particularly since I predominantly use HSS tools.

Myford also used the "Norman" patent tool post in the earlier days as did RR in their workshops. I've still got the original Myford four way but its in a box and not used any more.

I do agree about the loss of rigidity with a QCTP particularly the extra overhang that it has.

[old martParticipant @oldmart]

Having lowered the height of a toolholder successfully, why not make your own? Drilling and tapping for the screw is not difficult, you do need to displace the screw by about 0.003" to 0.005" to make sure the insert is pulled into the pocket when the screw is tightened.

[Dave HalfordParticipant @davehalford22513]

Posted by brian jones 11 on 07/07/2021 17:08:49:

A real mans tool post Rocker or Lantern? Did Myford ever have one of these?

good thinking

Edited By brian jones 11 on 07/07/2021 17:19:56

With those all you need to do is change the base for a flat ring to give you centre height on your insert tool and you'll never have to check insert centre height ever again even if you swap from straight to left or right handed holder in the set.

The boat or rocker requires constant checking every time you move it.

If you use Armstrong holders the same applies for HSS till you sharpen them.

Sometimes the old junk is better than the new junk, depending on how much outlay you have invested in the new junk

[Howard LewisParticipant @howardlewis46836]

Give me a proper 4 way toolpost every time. (These earlier things were the best that they could manage at the time )

Boat / Rocker posts don't keep the rake angle constant as centre height is maintained.

The need for greater rigidity and speed brought about the 4 way and the QCTP..

Guess what Industry uses

Their QCTPs are rigid, designed for heavy work, and quick tool changes.

Howard

[JasonBModerator @jasonb]

The other big advantage of a QCTP is that the tool should go back in the same position in all three planes not just the horizontal that dedicated shims etc. give. Ideal if you are doing more than one similar part that needs two or more tools to machine it as you only need measure the first and then use the same handwheel or DRO settings to machine the rest.

[Roderick JenkinsParticipant @roderickjenkins93242]

Lots of "theory" on here about the lack of rigidity of QCTPs. I have never had a problem with mine on my S7. I have a Gibraltar post and have only ever used that with a boring bar that is too big for the tool holder (and for my J&S knurling tool which has a shank which is too big).

Rod

[Tony Pratt 1Participant @tonypratt1]

Posted by Roderick Jenkins on 08/07/2021 13:50:14:

Lots of "theory" on here about the lack of rigidity of QCTPs. I have never had a problem with mine on my S7. I have a Gibraltar post and have only ever used that with a boring bar that is too big for the tool holder (and for my J&S knurling tool which has a shank which is too big).

Rod

I agree, if you tighten a QCTP correctly there should be no problem with lack of rigidity.

Tony

[John BaronParticipant @johnbaron31275]

Posted by Tony Pratt 1 on 08/07/2021 13:54:10:

Posted by Roderick Jenkins on 08/07/2021 13:50:14:

Lots of "theory" on here about the lack of rigidity of QCTPs. I have never had a problem with mine on my S7. I have a Gibraltar post and have only ever used that with a boring bar that is too big for the tool holder (and for my J&S knurling tool which has a shank which is too big).

Rod

I agree, if you tighten a QCTP correctly there should be no problem with lack of rigidity.

Tony

Its nothing to do with how much you tighten a QCTP ! The problem is with the amount of overhang some have. The tool needs to be within the footprint of the cross slide for maximum rigidity.

[derek hall 1Participant @derekhall1]

The thought of going back to fiddling with shims to get a tool up on centre height….urgh! backward step in my opinion.

QCTP works for me if you use it correctly.

Maybe for interrupted cuts or taking large cuts then you may have problems but +1 for the gibraltar tool post, use that instead for these occasions.

I agree though with John Baron above though but again it depends on what you are doing with the lathe…

Regards to all

Derek

[Tony Pratt 1Participant @tonypratt1]

Never had a problem unless I didn't tighten it up properly, yes they do have overhang but in practice they are more than rigid enough for our purposes. Even used them on Haas CNC lathes.

Tony

[Andrew TinsleyParticipant @andrewtinsley63637]

I am afraid it isn't theory. My Myford QCTP is less rigid than my Myford 4 way toolpost. Simple fact!. I can load the tool and note the deflection. Deflection is larger on the QCTP.

As John Baron rightly says,,the problem is the amount of overhang that some (QCTP) have.

If you have both systems, then do a comparative test and let everyone know the result.

Andrew.

[brian jones 11Participant @brianjones11]

Loading up a Myford – like giving a child a bag of cement to carry

[Nick WheelerParticipant @nickwheeler]

Posted by derek hall 1 on 08/07/2021 15:26:48:

The thought of going back to fiddling with shims to get a tool up on centre height….urgh! backward step in my opinion.

QCTP works for me if you use it correctly.

Agreed.

And the height adjustment is a bonus from how a QCTP works. The main reason is the Quick Change. Which means having enough holders so that you rarely have to change the tools in them. Which is expensive, but then so is time.

Take a simple top hat bush which needs: the outer diameters turned to size(one tool); two faces(probably the same tool, but could be another); a hole drilled(tailstock, but at least two drill bits); then the hole bored to size(a third tool); all the edges chamfered(one or two tools depending on what you have); and finally parted off. That's at least four tools, which would be tedious for one part if you need to keep changing the tool and shims and resetting distances. But how often do you make one of these things? And what if you start the parting off, then want to swap back to the chamfer tool so they all match?

I did try the fourway tool post, but having sharp tools sticking out in several directions was not appealing. And turning it to the next tool takes a similar amount of time as swapping a QC holder.

I think the QCTP is the best value thing I've bought for the lathe and mill combined, and that includes ER32 chucks for both with square and hex Stevensons Blocks.

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