True Bore Alignment System

[BuffaloBill]

I ordered a TBAS Monday night and it’s already here (Thursday afternoon)!

The initial setup portion of the instruction manual discusses using a lesser torque (10-15lbft) for the radial adjustment screws, before a chuck is mounted to the radial plate. After a chuck is mounted, the radial adjustment are torqued to 25-35lbft in use. That makes sense to me; a big beefy chuck bolted on there will greatly stiffen that radial plate, allowing a greater screw torque for a given amount of plate deflection, etc.

The ER-50 chuck I’m waiting for has an 18mm thick mounting flange. This would add some stiffness but not as much as a chuck body’s 2-3” thickness or beam height. Perhaps an upper torque limit of 20-25lbft would be appropriate? Intuitively I wouldn’t think much torque would be required to solidify this system for prevention of chatter with the light cuts I’d typically be taking. But I don’t know that for certain.

Any of you material/stress analysis people want to offer an opinion? I didn’t measure screw thread pitch or take the radial plate off to see what sort of beam dimensions remain after the lightening cuts were made on this V3 version.

I can call or email Nate to get his advice on this but thought others here may be interested in an ER50 setup, and would perhaps chime in.

The weight of this TBAS with a D1-6 mount, but without the ER-50 chuck, feels very similar to my 9” 3-jaw. I use wooden cradles that sit on the carriage arms, positioning the chucks at the right height, to make installing them less strenuous and more controlled. I’ll make one custom for this TBAS as the diameters of the axial & radial plates are different which causes it to sit at an angle in my existing wooden cradles.

 

[LVLAaron]

Congrats. Keep us posted.

 

[Sniperhandle]

I ordered a TBAS Monday night and it’s already here (Thursday afternoon)!

The initial setup portion of the instruction manual discusses using a lesser torque (10-15lbft) for the radial adjustment screws, before a chuck is mounted to the radial plate. After a chuck is mounted, the radial adjustment are torqued to 25-35lbft in use. That makes sense to me; a big beefy chuck bolted on there will greatly stiffen that radial plate, allowing a greater screw torque for a given amount of plate deflection, etc.

The ER-50 chuck I’m waiting for has an 18mm thick mounting flange. This would add some stiffness but not as much as a chuck body’s 2-3” thickness or beam height. Perhaps an upper torque limit of 20-25lbft would be appropriate? Intuitively I wouldn’t think much torque would be required to solidify this system for prevention of chatter with the light cuts I’d typically be taking. But I don’t know that for certain.

Any of you material/stress analysis people want to offer an opinion? I didn’t measure screw thread pitch or take the radial plate off to see what sort of beam dimensions remain after the lightening cuts were made on this V3 version.

I can call or email Nate to get his advice on this but thought others here may be interested in an ER50 setup, and would perhaps chime in.

The weight if this TBAS with a D1-6 mount, but without the ER-50 chuck, feels very similar to my 9” 3-jaw. I use wooden cradles that sit on the carriage arms, positioning the chucks at the right height, to make installing them less strenuous and more controlled. I’ll make one custom for this TBAS as the diameters of the axial & radial plates are different which causes it to sit at an angle in my existing wooden cradles.

You are going to be fine, I wouldn't worry about chatter, I have never experienced it on 2 different 1340's and one 1440 lathe, All Asian light duty lathes, Mine has a Gator 6 jaw.

 

[LVLAaron]

For those with a 3D printer and no CNC, I whipped up a fully parametric tapered collet in OpenSCAD.

// Tapered Cylinder with Tapered Hole
// All dimensions in inches

// Parameters
outer_diameter = 1.5;      // Outer cylinder diameter
cylinder_length = 1.75;    // Cylinder length
hole_dia_large = 1.25;     // Large end of tapered hole
hole_dia_small = 1.1;      // Small end of tapered hole

// Relief cut parameters
relief_cuts = 4;           // Number of relief cuts
relief_cut_width = 0.04;   // Width of each relief cut (inches)
relief_cut_length = 1.2;   // Length of relief cuts from front (inches)
relief_cut_depth = 0.02;   // How deep cuts go into wall (inches)

// Convert to radius for OpenSCAD
outer_radius = outer_diameter / 2;
hole_radius_large = hole_dia_large / 2;
hole_radius_small = hole_dia_small / 2;

// Create the main cylinder with tapered hole and relief cuts
difference() {
    // Main outer cylinder
    cylinder(h = cylinder_length, r = outer_radius, center = false, $fn = 100);
    
    // Tapered hole - using hull() to create smooth taper between two circles
    hull() {
        // Large end of hole (at z=0)
        translate([0, 0, 0])
            cylinder(h = 0.01, r = hole_radius_large, center = false, $fn = 100);
        
        // Small end of hole (at z=cylinder_length)
        translate([0, 0, cylinder_length - 0.01])
            cylinder(h = 0.01, r = hole_radius_small, center = false, $fn = 100);
    }
    
    // Relief cuts - alternating from front and back
    for (i = [0:relief_cuts-1]) {
        rotate([0, 0, i * (360/relief_cuts)]) {
            translate([outer_radius - relief_cut_depth, -relief_cut_width/2, 0]) {
                if (i % 2 == 0) {
                    // Even numbered cuts start from front (z=0)
                    cube([relief_cut_depth + 0.1, relief_cut_width, relief_cut_length]);
                } else {
                    // Odd numbered cuts start from back (z=cylinder_length)
                    translate([0, 0, cylinder_length - relief_cut_length])
                        cube([relief_cut_depth + 0.1, relief_cut_width, relief_cut_length]);
                }
            }
        }
    }
}

// Optional: Add a visual reference for hole dimensions
// Uncomment the lines below to see the hole profile
/*
color("red", 0.3) {
    hull() {
        translate([0, 0, 0])
            cylinder(h = 0.01, r = hole_radius_large, center = false, $fn = 100);
        translate([0, 0, cylinder_length - 0.01])
            cylinder(h = 0.01, r = hole_radius_small, center = false, $fn = 100);
    }
}
*/

 

[LVLAaron]

// Tapered Cylinder with Tapered Hole
// All dimensions in inches

// Parameters
outer_diameter = 1.5;      // Outer cylinder diameter
cylinder_length = 1.75;    // Cylinder length
hole_dia_large = 1.25;     // Large end of tapered hole
hole_dia_small = 1.1;      // Small end of tapered hole

// Convert to radius for OpenSCAD
outer_radius = outer_diameter / 2;
hole_radius_large = hole_dia_large / 2;
hole_radius_small = hole_dia_small / 2;

// Create the main cylinder with tapered hole
difference() {
    // Main outer cylinder
    cylinder(h = cylinder_length, r = outer_radius, center = false, $fn = 100);
    
    // Tapered hole - using hull() to create smooth taper between two circles
    hull() {
        // Large end of hole (at z=0)
        translate([0, 0, 0])
            cylinder(h = 0.01, r = hole_radius_large, center = false, $fn = 100);
        
        // Small end of hole (at z=cylinder_length)
        translate([0, 0, cylinder_length - 0.01])
            cylinder(h = 0.01, r = hole_radius_small, center = false, $fn = 100);
    }
}

// Optional: Add a visual reference for hole dimensions
// Uncomment the lines below to see the hole profile
/*
color("red", 0.3) {
    hull() {
        translate([0, 0, 0])
            cylinder(h = 0.01, r = hole_radius_large, center = false, $fn = 100);
        translate([0, 0, cylinder_length - 0.01])
            cylinder(h = 0.01, r = hole_radius_small, center = false, $fn = 100);
    }
}
*/

Here's a version without the collet style relief cuts.

 

[DSMWerks]

I picked up a 31mm ER50 collet from Icarbide on ebay for $19. I've bought other stuff from then and know it decent stuff. Another option is Maritool made in the USA for $46.50 and I love their stuff. All my CAT40 toolholders are Maritool. I also need a 32mm or 1 1/4" for the 1.250" barrels I get now and then. I have not got the ER50 collet chuck mounted yet. My day job wont give me a break. Part of owning a shop I guess.