A QCTP question, or two

I have acquired a small QCTP set (via a man who came down the chimney) which is sold on e-bay for about 25 quid, and I have questions:

1. There are two toolholder positions, but the holders are so long that only one can be used at any time. Is this a mistake or have I misunderstood something?

2. Should I mill away the interfering corners at the end further from the cutting position?

3. The toolholders and the main block are light alloy. Are my doubts about strength, life, etc justified?

4. Would I be better off making up something similar from proper steel?

Seasonal wossnames to y'all

Tim

You're not missing anything Tim. They are intended to hold one tool at a time. As for the alloy, I've never seen one made from that material, only steel.

Pete

Gloster tools make a QCTP in alloy, I've never used one but they have been selling them for a long time.

Are the alloy tool posts anodized or something to stop the alloy parts sticking?

Pete

From what I have seen, the Gloster version is very similar to the one from the far east, so it could possibly be that they do not 'make' it themselves. It is also about twice the price. The one I have looks remarkably like the pictures of both offerings. And while the central block is 'silver coloured' with a fine shot-blast finish, the holders are blackened. I cannot say whether either has been anodised or merely painted.

Regards, Tim

No Tim , as Peter says don't modify your holders. The advantage of the QCTP ( mine is the "conventional" type) is that you have a holder for each tool ( I have 15!! ). You set each up to be on centre height then just change between tools as required.

Regards

Norman

Unlike Norman's picture above it is more common to have the block rotated 90 degrees clockwise from as shown so that one mounting is close to the lathe centre line for holding a boring tool or combined facing and chamfering tool. As every tool becomes expensive to mount it is worth thinking whether you can combine them and also use the other end by using long toolbits.

A QCTP is not just for setting centre height. As they mount repeatably in the same place this is also in the same place relative to one another which you can use to advantage. Use a cranked right hand knife tool if possible so that its cutting point is exactly in line with the facing tool so after facing you do not need to reset your reference for the new tool. Then set the parting / grooving tool left hand front and edge to align with the knife too. Finally align your screwcutting tool for matching depth.

So for example you can face off, cut a length for threading then go straight in with the groove for screw cutting tool clearance, then switch to screwcutting all aligned to each other.

Finally if you set the cross slide index on zero with the tool on a known round figure diameter, eg 1/2 in and don't fiddle with it you know it will be at zero when dead centre. Then you can cut close to required size on the dial and only check for the final precision cuts.

That's a nice collection you have there Norman. Not seen an upside down parting tool holder like that before, did you make it or buy it?

Well spotted Vic! I have another QC tool post that mounts on the back of the (long) cross slide and the "upside down" parting tool is fitted there. Parting is thus achieved by "withdrawing" the cross slide. Having parted off then the conventionally (front) mounted tool can be used for the next item. (Tool post, holder and blade were purchased )

Bazyle yes I agree it is more usual for it to be positioned 90 deg C/W but this photo was taken for a thread many many posts ago just to demonstrate my (bodged up!) mounting for a dti for setting up 4-jaw work.

As to "economising" on the number of tool holders yes you have a point but having the tool you need ready mounted saves time and frustration.

Norman

Sounds like an ideal setup. Can't quite see, is it a "T" parting blade?

Of course you will sometimes also want to set it as Norman has for getting to the outside of a flywheel for example.

That DTI mount is neat and could be a dual use holder by putting a boring tool in the holder having the DTI bracket acting as packing for said tool.

The idea of replacing the tool in exactly the same place is not possible with the kit I have, as the location relies on two sides of a (fairly slack fitting) wedge, pushed out by a piston. Nothing to hold it properly central.

Thanks for the comments, everyone. I now know why the fancy ones are more expensive.

A further question:

I understand the workings of the piston type (even if better located) and the wedge type, and what NJH calls his 'conventional' type, but what is the sort with a short length of coarse thread, cut away on one side, around the adjuster nut called? And how does it work?

Cheers, Tim

PS: Aha, a better look at the NJH upper picture allows me to guess that the cut away thread is on a separate spindle on the central block and it serves to operate the draw-back action of the holding device and to hold down the adjuster flange itself. Is that correct? And apart from 'conventional' is there a name for it?

Edited By Tim Stevens on 23/12/2015 21:25:56

Arguably one of the best types of QCTP is the type shown in Normans picture. These were originally made by Dickson but others have copied the design and some are even interchangeable. The tool posts themselves are available in quite a range of different sizes to suit different Lathes.

http://www.myford.co.uk/acatalog/Myford_Quick_Change_Toolpost_and_Accessories.html

Just one supplier, Chronos also sell something similar.

Edited By Vic on 23/12/2015 21:57:09

Like Bazyle I have a habit of setting all tools where possible to the same X=00 setting, this makes life easier when entering tool offsets into the program when using cnc. Tools that can be set this way are RH, Neutral, LH, Grooving, Parting, Chamfering & External threading.

Emgee

.

Tim,

I am ready to be proved wrong, but; I think you will find that pushing loose-fitting male/female dovetails into engagement [by pressure at about the mid-point] will automatically centralise them ... It would be worth doing a few practical tests on your QCTP.

MichaelG.

My home made QCTP is repeatable to within a few thou, but not perfect.

It was one of my most successful home builds, and transforms the use of the lathe - you do need plenty of toolholders though, I find 12 is not enough!

Neil

Quite right!! I have 23 or 24 and am planning more!!

cheers

Bill

Norman, Can you tell me the source of your Dickson style holders please ? The pattern ones I have bought do not lock up as they should and I could do with buying another 5 or 6 as I only have 4 at present. Genuine ones are to pricey for me. Chris.

Dickson tool holders often sell for around £20 second hand at the shows. No idea what the posts cost though.

Bill,

Didn't know this was a competition! You do not stand a chance!

45 with normal tooling, 1 with 2 wheel knurling tool, 1 with keyway slotter, 2 special, homemade to take 16mm boring bar and very special for variable helix angle screw cutting. 3 known spare unused, so that is 52 and that is just the Myford size.

The Harrison M300 ones are somewhat larger in size but smaller in number. Cost a fortune but time and money has to be interchangeable.

Must make some Barry Jordan style carrousels to hold them sometime

Edited By KWIL on 24/12/2015 10:15:01