Quick Change tool post advice

HI, All.

My minilathe has a standard toolpost and I keep each tool with some shims that pack it up to centre height. Changing tools is a bit of a chore but it's not terrible.

Simon of SPG Tools from whom I bought the lathe was against quick change tool posts because of the reduction in rigidity.

What actually bothers me about the setup I have now is as much getting the tool at the correct angle to the work piece as the time it takes to set it up.

So I'm thinking about a QCTP (as I believe we acolytes of the mysteries are to call it).

Firstly, do you agree with Simon - is rigidity an issue. Secondly, do I go for the eBay type (30 quid) or the UK Provided type (£60)?

The eBay ones seem to offer two mounting points and a cam based locking mechanism (where the tool is pushed out against the dovetail). It also appears from the photos that the toolpost proper is made of aluminium rather than steel which, frankly, concerns me (mass and flexibility).

The ones by our beloved professional UK suppliers (yes, you know who you are!) are all steel, have one mounting point and use a mechanism which draws the tool in, possibly being more rigid accordingly.

Will I get cross with my £30 purchase and need to go out one at twice the price almost straight away?

Thanks all!

Iain

Think you answered your own question, go with the steel one. For the reasons you mentioned it should be more rigid all round.

> Firstly, do you agree with Simon - is rigidity an issue.

Not with mine (on a mini lathe).

Neil

I have a Dickson clone QCTP ( Bison - steel ) with numerous holders; for rigidity I have my tool post set so that the compound slide is wound back some to allow the holder to sit over the end of the compound slide so giving support to the holder whereby the cutting forces are pushing down onto the compound slide as opposed to having a lot of overhang over the edge of the slide. I also have made a brass knurled locking screw which I keep nipped up on to the gib strip to eliminate any slackness on the compound slide. works well for my machine.

George.

A QCTP is less rigid,but the speedy tool change is well worth it, and if a more rigid set up for is required a certain job then go back to older tool holder for that job. Before you buy ensure that spare tool holders are available ,and when you have got used to the quick change,go and buy some more holders as they are very useful,particularly if you machine brass and steel ,and need to use tools with a different rake for these materials,if you wait too long the supplier could go out of business,or use a different source,then you cannot buy extra holders that are decent fit on your block.

As Nigel says they are less rigid but it may not effect your work. I suppose it depends on how many tools you use on a regular basis but I've glued a shim of the correct thickness to my most used tools so they're always on centre height. The only one without is my Tangential tool which has height adjustment built into it. If I used lots of different HSS tools that were likely to change height through sharpening I might consider a QCTP but as I don't the money has been spent on more tooling!

The UK provider ones are fine Lain. I bought one recently along with some holders as cheaper that way. It's no different to the one on my Boxford other than the height on that one is extended - it's probably 40 odd years old.

Mine is the 78175 toolpost

One problem you may have is the fixing - hole to big and stud in the machine too short. My initial thought was to make a stud of the right size for the holder with the other end to suit the lathe. The hole in the post is .438" dia and the over all height is 1.796". The stud on the lathe is 8mm (0.315). Yours may be different.

Then I changed my mind as I didn't fancy getting the stud out of the compound slide so intend to make a sleeve to go at the bottom and a nut with the correct dia on it that extends into the tool post with the same AF size as the current nut. I might just locktite a nut onto a thread on the new nut as the lathe stud is short.

A lot of trouble but there is a useful holder for the Myford tool post. One that hold a 1" indexed tip parting off tool. The normal one will hold a 1/2 x 1/16 blade as well but I have had problems getting the 1/16 in blades. The UK seems to like 3/32 for some reason. They also aught to a holder with a beefed up top to take 16mm boring bars as well. The standard holders take 1/2" tooling all below the lathe centre line. Seems they have forgotten that boring bars tend to sit either side and can be even when made from solid.

To be honest given even the torque available even on a boxford talk of flexure with this tool post size is a bit OTT really. I'm being polite.

John

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I don't know how experienced at making stuff you are, but if you want to make a QCTP there are plans for my 'improved' version of the Nakamura toolpost here:

make-a-quick-change-toolpost

make-a-quick-change-toolpost-part-2

Neil

Considering said mini lathe assume its this type

If so I would strongly recommend not to buy something else.

Rigidity non existent even worse the height adjuster being non repeatable the casting and screws flex.

In general all the other types massively superior and not from monkey metal.

Might be worth taking a look at the new wedge style from arc euro. Similar to the piston style but the holders are pulled in to the dovetail rather than pushed out. It's not much more expensive either. I was tempted by this type but couldn't find a supplier in the UK for the larger size. I went with a Dixon clone in the end.

I believe the Myford ones are heat treated and ground Neil including the holders. The ends of the tool fixing screws don't bell out either making them impossible to remove - at least not the ones on my Boxford so hope the new ones are the same. Given the prices when I bought I wonder if they are being sold off and new stock at some point will be the usual clones that seem to have got worse over time. It might be worth the OP reading the other recent toolpost thread.

My fix for the boring bar holder will be a clone holder with the bits that form the slots removed and a block of steel bolted to it with a suitable size hole in it. I have this large piece of drop forge steel somewhere that should be fine - once I find it again.

I wonder if you milled the tool post on the lathe with your Taig vertical slide?

John

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Edited By Ajohnw on 06/03/2016 00:03:19

That sounds like a good idea for folks with mini lathes George.

That's not the only problem. This is a very expensive "mini lathe"

All really to save making the headstock circa 19mm higher for the same swing over the saddle but in real terms the swing over the saddle is too big for the size of the lathe - makes the numbers look better and @@## the practicalities. The design results in the way the compound is mounted as well. Myford get away with similar thicknesses but make a better job of mounting the compound.

John

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For clarification... the tool holder is also closer to the centre of rotation of the compound slide, as with all these machines there is always a need to tweak this & that to get best result.

George.

So the recommendation so far is 'spend more money'. Gah!

I've found 4 mechanisms so far.

Neil's, which pushes a barrel out to push the holder against the dovetail.

One which appears to have two dovetails one to pull the holder in and one to be pulled against. I think the one JOn hates is of this type. Arceurotrade have one of this sort (which is not to say, that theirs is non-rigid, etc...). I think this is also how the 'Bison' type work link

One which has a moving outer dovetail that pushes in to secure the toolholder, such as this one from Chronos link

One which has a moving inner dovetail that pushes out to secure the holder. ArcEurotrade have this sort ​too

MY own guess is that the ones which pull in (the latter two) would be the most rigid in that they should have more direct metal to metal contact.

At £60+ quid I will have to save up (or add Neil's design to my long list of tools to build)...

Iain

Irrespective of what type you build / use, seriously think about getting rid of the compound slide in favour of a bif thick very rigid steel or cast iron block.

In day to day use the compound is only used for doing angles which isn't all that often but by being there and having the extra slide, hang over etc it impedes rigidity.

You can always fir the compound when it's needed again, usually only two nuts or screws.

That toolpost / holders are my own design. Originally done in a smaller size in about 1980, before the cheap imports to fit a ML7. Think it got published in ME around 1988 ?

It's opposite to the current imports on the dovetail as i wanted something that was easy to make holders, Lets face it you make more holders than toolposts and an external dovetail is far easier to make. Also you can often get closer to the work with the unused dovetail with it being internal.

I can see your point, John, but I'm not sure that would work on my lathe.

there is no real means to move along the lather in a controlled manner except via the topslide (unless you are under power).

The large wheel on the left is far too coarse.

The lead screw is a possibility, but I would need extend the leadscrew and mount a wheel with graduations to turn it.

Mind you the topslide handle gets in the way of the tailstock when turning small diameters on centres, so that would be a bonus.

I think it's a bit much for me at this point in my skillset!

Iain

P.S. can someone tell me how the devil to put linefeeds in without the cursor going back to top of the page?

> The ends of the tool fixing screws don't bell out

Found a source of screws with the ends tapered well beyond the thread depth. Used on M5 my holders and replace the M6 ones on my standard 4-way.

Neil

It would you know, I made a block toolpost for my mini lathe.

You can fit one where the top-slide attachs.

You need two counterbored holes for M6 screws to fix it in place either side of a central hole for the spigot, and a decent length of M10 studding on top.

Neil

Iain,

A great project would be to extend the leadscrew and add a handwheel with divisions.

It may be worth checking the available spares ... there might be a longer leadscrew in the range.

MichaelG.