Tool post height

[Andrew TinsleyParticipant @andrewtinsley63637]

I am not knocking QCTPs, I use mine most of the time. I am simply saying that I get more deflection for a given tool load. than I do with my Myford 4 way tool post.

As to the convenience or otherwise of the two systems, I am making no judgement. That is up to the individual user.

Andrew.

[Nigel McBurney 1Participant @nigelmcburney1]

At my first job ,there was a Boxford,with four way toolpost,all hss tools in those days, right pain in backside with endless shimming though it was rigid , when I bought my Myford I never considered a 4 way, I just copied a Drummond tool post,a single holder clamped on a round post,worked well,with no shims, when I had to earn a bit of cash in later years ,to be competative I bought a quick change toolholder with 6 holders,that noticeablely speeded up the lathe setting and operation,though it is not so rigid. When I aquired a taper turning attachment for tapered threads my hss thread chasers were too big for the q/c toolholders I went back and used the original Myford tool clamp, and when taper turning the top slide has to be set parallel to the cross slide, I chase threads by feeding at 90 degrees to the work , Usually when threading phosphor bronze the chasers can deflect down, With the single clamp and the cross slide in line with cross slide there is vast improvement when machining phos bronze fittings for bsp threads,I think that with top slide in this position there is no tendency to tilt the top slide across the V ways, the strain is taken over most of the length of the slideways. I do not have a taper turning attachment for my Colchester so the Myford has to take a bit extra load than normal.

[old martParticipant @oldmart]

The Smart & Brown model A at the museum has a choice of 2 four way and 1 two way toolposts,all at the same height, plus a special which holds 26mm blades and 12mm boring bars, also a rear toolpost which is dedicated to 26mm and 32mm blades. All of the tools match the height so no shims are required. A QCTP would be prohibitively expensive with about 50 tools and take up so much space. The largest toolpost can accept 25mm boring bars.

Edited By old mart on 08/07/2021 20:19:09

[John BaronParticipant @johnbaron31275]

Hi Guys,

Just in case there are those that don't know what the "Norman" patent tool post looks like. This is the one that I made and use. The tool slot will hold a 1/2" inch tool and the height is adjusted by altering the silver M6 cap screw that bears on the surface below. The tool holder is secured by a spilt cotter using an M6 thread. It takes about a quarter of a turn on the cotter screw to go from locked to loose.

Drawings for the Myford size one are in my album !

[VicParticipant @vic]

Posted by John Baron on 08/07/2021 15:17:34:

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.

I agree. It’s also not difficult to understand if you compare some of them. I guess if you’ve spent hundreds of pounds on tool holders you’re less likely to find fault though.

Height adjustment is often mentioned as some kind of insurmountable advantage. I use a Tangential tool which has built in height adjustment. I also use insert tooling with tool holders that have been machined to the correct height for my four way or I’ve permanently bonded shims to the bottom.
It seems nonsensical to have height adjustment when using inserts, perhaps that why it’s not used on CNC machines. Of course, if you use lots of hand ground tooling and are a professional then I can sort of see the argument. As for speed, it only takes me a couple of seconds to change tools in my four way.

[MeunierParticipant @meunier]

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

/……. (and for my J&S knurling tool which has a shank which is too big).

Rod………/

I also have a J&S knurling tool which has after 40yrs of inactivity severely seized up the knurls on the pins.
Before getting brutal, have you ever removed/changed the knurls and if so, do the pins punch out easily ? Thanks
DaveD

Edited By Meunier on 08/07/2021 21:04:37

[Martin KyteParticipant @martinkyte99762]

George Thomas was not a fan and had some interesting comments. He began by saying that for Model Engineering work virtually all of our 'cuts' are of short duration and tool changes are frequent. Therefor some kind of rapid tool change system is desireable. To him that meant either the QCTP or the indexed 4 way toolpost. The emphasis being on the indexing function which is actually quicker than swapping holders on a QCTP. His version of the 4 way tool post when on test returned cutting tips to within a few tenths allowing very acurate repetition work to be carried out.

I have been using a QCTP for the last umpteen years and admit to buying one mostly because it seemed like the thing to do rather than any carefully thought out plan. The other reason is I suspect I was not getting the best out of the 4 way, I certainly rarely populated it fully and didn't use the indexing to any advantage. As I have commented in a QCTP tools do not always return to the last position they were in. The system is more unstable, especially in our sizes, but certainly workable and as intimated above there is no indexing system on the tool post itself so I wonder if I could do better with a change of approach.

Personally I feel like a GHT version build coming on, but then I'm a bit of a fan as some of you will have surmised. Especially as I now have two topslides so would end up with the advantage of being able to switch between the two systems.

I suspect the choice really comes down to what we do. I tend to plough on for years using the same sorts of techniques untill something starts me thinking and I begin to count things like how many tools do I actually use on a regular basis. (Usually less than four on most jobs). How much repetition work etc.

As George said both sytems have their protagonists with fairly robust views. I suspect, like most things, there is no absolute answer but that of adopting the system that suits us best.

regards Martin

 

 

Edited By Martin Kyte on 08/07/2021 22:40:59

[SteviegtrParticipant @steviegtr]

I have the QCTP on the Myford. The larger 250-111 model. I've had many a dig on here about it. Especially because i removed 3mm from the compound & then milled the underside of the toolholders down. So i now can use up to 16mm tooling. Was it a mistake. Nah. It's great. Oh but i do still use the old 4 way block. It comes in handy for squaring up the cutters to the chuck face.

Don't bother i already have my coat on.

Steve.

[VicParticipant @vic]

I think my little 8 1/2” x 14” is meant to take 10 or maybe 12mm tooling? I bought a 16mm TNMG holder and trimmed a couple of mm off the bottom and it works well. The holder is quite tough but it wasn’t too much trouble to trim it down with a carbide mill.

[Martin KyteParticipant @martinkyte99762]

Does all this beg the question, why use bigger tooling than that which will fit?

regards Martin

Edited By Martin Kyte on 09/07/2021 08:04:19

[JasonBModerator @jasonb]

Posted by Martin Kyte on 09/07/2021 08:04:07:

Does all this beg the question, why use bigger tooling than that which will fit?

regards Martin

Edited By Martin Kyte on 09/07/2021 08:04:19

When you need the rigidity, I have boring bars that are way too big to fit in the 4-way let alone the QCTP yet they have been the best tool for bores of 6-8" length, Same applies (though less often) when shape of part dictates a lot of stick out from the toolpost.

[brian jones 11Participant @brianjones11]

Posted by Vic on 08/07/2021 23:17:07:

I think my little 8 1/2” x 14” is meant to take 10 or maybe 12mm tooling? I bought a 16mm TNMG holder and trimmed a couple of mm off the bottom and it works well. The holder is quite tough but it wasn’t too much trouble to trim it down with a carbide mill.

wow that looks like the dogs………… ca $10 on Ali

looks like you would use that with a standard myford clamp

https://www.myford.co.uk/acatalog/TOOL-CLAMP–74-1409-1-1278.html

I'll go and check tool height and revert

[VicParticipant @vic]

Posted by Martin Kyte on 09/07/2021 08:04:07:

Does all this beg the question, why use bigger tooling than that which will fit?

regards Martin

Edited By Martin Kyte on 09/07/2021 08:04:19

The smallest tool holder for some inserts is 16mm so no choice. The TNMG is a case in point. I’ve just got some polished inserts for aluminium at a very good price and they work really well. The tool holders are cheap on the auction site.

[Alan JacksonParticipant @alanjackson47790]

MLA version QCTP with no overhang

Alan

[JasonBModerator @jasonb]

Alan, unless I'm missing something the holder still has no direct line of support under the tool and is over hanging from the toolpost which is the "disadvantage" people are talking about

[brian jones 11Participant @brianjones11]

my lathe never been that clean, eat you dinner off it

[old martParticipant @oldmart]

For those who would like TNMG inserts, but don't have a big enough lathe to take the common size 16, (there are smaller, but they are like hens teeth), you can look at WNMG 06 which has all the advantages but is smaller.

[SteviegtrParticipant @steviegtr]

The reason i posted about using the larger tooling was not because there is anything wrong with the smaller items.

The are so many cutters in the larger sizes of good quality over the smaller items, E.G. I have a 16mm boring bar ,which is a TIZIT, used . I paid £8.00 for it.

Steve.

[Alan JacksonParticipant @alanjackson47790]

Posted by JasonB on 09/07/2021 11:22:31:

Alan, unless I'm missing something the holder still has no direct line of support under the tool and is over hanging from the toolpost which is the "disadvantage" people are talking about

Jason, You are quite correct but the cutting tool does not reach (cantilever) beyond the lower support so there is no moment created to make the topslide tend to flex or pivot. If I need a more solid toolpost I use a four way or triangular toolpost.

Alan

 

 

Edited By Alan Jackson on 09/07/2021 17:37:32

[VicParticipant @vic]

I found at the model engineering shows all the bigger stuff was cheaper. I suppose because many model engineers have modest size machines. I’ve paid as little as six or seven pounds for a tool holder. Having machined a Sandvik tool holder for a friend I was confident of being able to machine them when needed.

[brian jones 11Participant @brianjones11]

that looks very solid to me, and simple. These triangle tips have a lot going for them

BTW has anyone come across a prog for decoding carbide language for tools and tips, ie you just put in the code and it spits out the spec

I saw it mentioned somewhere now lost in the mists of dementia

[DiogenesIIParticipant @diogenesii]

There's a useful pdf you can download here – (it's the one that used to be visible at Carbide Depot..)

Midwest Supply – Carbide Insert Designation

[Howard LewisParticipant @howardlewis46836]

Re Carbide tip codes.

There was a thread on here, not too long ago.

Look through previous threads, or use the search facility.

Howard

[brian jones 11Participant @brianjones11]

heres my take on the tool height dilemma

hope it make sense – for illustration only as you must check your own dimensions

so with the desirable and plentiful 12mm holder you can

a) skim 2mm off the holder base (or part skim as suggested leaving a step on the overhang)

b) Skim the top of the topslide – but then the 4 way block will be wrong and you will need shims for a 5/16" hss

c) Make up a 4mm shim piece to fit under the holder and use the elephants foot

d) buy a new chinese machine and stop dickering around

What do you think

Obtw I have made the assumption that a 12mm holder will also mean the height of the tool tip – is this always right?

 

Another member mentioned the use a  16mm holder and doing some skimming to make it fit.  According to my estimate it should fit as is under an elephant foot see below – pls advise as I dont have one of these yet and I was thinking of getting a set with  triangle pieces (in fact it was steviegtr as above)

Edited By brian jones 11 on 10/07/2021 16:02:34

Edited By brian jones 11 on 10/07/2021 16:06:07

[Howard LewisParticipant @howardlewis46836]

Personally am averse to making any irreversible changes to the machine, so would advocate milling the underside of oversize tool shanks.. (But not enough to weaken them seriously. 2 mm off a 12 mm will not be as weakening as 2 mm off a 8 mm shank.

Stiffness is BD^3 / 12 , so keep D as large as possible in the interests of rigidity.

One or two tool shanks have been reduced in depth, but leaving the area immediately near the carbide tip at full section, for that reason..

Howard

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