The body of the Aloris wedge type and clones is hollow, and there is little chance to reduce its height. But the toolholders can go right down to contact the topslide, and perhaps also their lower ledge reduced.

You won’t need to reduce the height of the AXA toolpost itself , just the ‘ledge’ height of each holder; I think you will still need to do this for 3/8 tooling.

It is possible to get ‘slim’ toolholders in this size with a base thickness of 7.5mm / ?5/16″ which might help but it’d still be a bit tight with 1/2″ tooling.

What’s the lathe, just out of interest..?

Could ditching the top slide and putting a solid mount on the cross slide be an option?

Filled with a vague sense of nagging doubt, I went over this afternoon, turned a piece of steel and checked the daylight between the bottom of that and the topslide by inserting parallels and shimstock.

Everything was mic’ed and sums done – centre height on mine seems somewhere between 23.010 and 23.020mm as discerned with the equipment I had to hand.

I also realised that some of my 12mm tools have been skimmed; I’d forgotten that I’d done this, think it was one Saturday morning ages ago when I discovered that some ’12mm’ Glanze tools were actually on 1/2″ shanks.

Most 12mm insert tooling is a bit ‘touch & go’ whether you will be on C/H or not; 1/2″ HSS is likely to sit too high..

Volans, a passing thought for your boring bar holder, depending on the size of the hole through it.
I’ve not yet done so, but my spare one has a hole larger than MT2, so the plan is for an MT2 sleeve to house my boring head.
It will mount in the conventional position, perpendicular to the bed rather than parallel, and form the basis of a radius turning attachment.

Bill

I am also considering changing from my Dickson quickchange tooling (that never seems to work that well) that I use on my Myford.

Two choices seem attractive from arc eurotrade, is the piston type or wedge type. Anyone got any experience and feedback on this type of toolpost?

What are the advantages and disadvantages of piston and wedge type when in comparison?

What size/types are suitable for a myford?

“What are the advantages and disadvantages of piston and wedge type when in comparison?”

In the piston type, the tool holder is pushed away from the toolpost body. It therefore contacts only on the two sides of the dovetail, and the position and angle can vary slightly each time a given toolholder is clamped.

The wedge type toolpost expands so that the toolholder is clamped on both sides of the dovetail. This simultaneously forces the flat interface surfaces together. It therefore has the best chance of always ending up exactly in the same position.

Mark

On initial examination it looks to kinematically be a Dickson type but the offset T-nut style clamp spoils things. As the clamp is operated by a cap head screw rather than a cam device it should be able to go tighter theoretically improving security.

However the whole point of the Dickson double Vee kinematics is that it will always be able to find a stable line and point or two points and a line contact on oppositely distributed between the pair of Vees. Which isn’t how tis toolpost works.

Considering the Dickson first it should be noted that, country to popular opinion, the paired Vee system isn’t over constrained in practice. It simply takes up the first available dynamically stable point and line or two points and line contact. Over constraint requires impossible levels of manufacturing accuracy. The advantage of this design is that stable seating requires only that the pair of Vees on any component be parallel and of constant depth / height given reasonably accurate spacing. The big disadvantage of the true Dickson is that tolerances on the toolpost T-slot, locking T and locking cam need to be very tight if turning the cam is to produce sufficient holding force. Hard to hold the tolerances at affordable import prices.

The offset T-nut of the Enco system destroys the Dickson kinematic balance. For all practical purposes it exploits only the inner sides of the Vees on both tool holder and post. The clamping force pushes the two closest male and female inner Vee sides together whilst the remote inner Vee sides just stop things twisting out of control. All in all not vastly dissimilar to the the kinematics of a stationary tail wheel style aircraft sitting on the ground. Unless something is way out of tolerance the outer Vee faces are primarily guides to ensure its all goes together properly when the toolholder is put on.

Clive

I never quite understood the concept of “over constrained” with respect to the Dickson. Does it mean achieving two side contact on both Vs? This is clearly unachievable in practice for the Dickson design. Or does it mean that any one of two or more stable possibilities will happen at random once clamped? OK, but hardly a useful feature in comparison to designs with a unique, precise and repeatable clamped position. I always felt that the Dickson design would be improved if the “second” V had a degree of flex, for example using well-chosen slotting, to ensure contact of both Vs.

Another feature I dislike is the cam actuation (though not unique to this design). At first sight it seems an attractive low cost actuator, but the mechanical advantage varies with the build up of tolerances, and the angular travel (and hence actuation travel) needs to be limited to prevent loosened by vibration. It ends up providing poor consistency and quite frequent malfunctions unless tolerances are sufficiently tight. The emco screw clamps at least provide constant mechanical advantage at the expense of fiddly tool changes.