Customizable V-Block for holding cylindrical parts. I designed this assembly using OpenSCAD as I wanted to try making parametric assemblies.

Disclaimer: Do not use this part for heavy machining. There's a reason these are made out of steel!

EDIT: I have now added an option called clampAngle. This will allow you to specify the angle of the clamping nut and bolt. By specifying clampAngle = 0 this will allow you to clamp round stock. Specifying clampAngle = 45 will allow for clamping of rectangular materials.

Using the customizer app you can easily change the dimensions of the v-block, the clamp to hold parts and adjust the nut and bolt used to clamp your parts.

For this model I used a 5/16-18UNC bolt and nut for the V-Block Clamp. The bolt that I used is 50mm long. Initially only 25mm of the bolt was threaded so I used a 5/16-18 die to thread the entire bolt shank.

Below are the dimensions used to create the show parts:

//V Block Dimensions
//Total V Block Length
Length = 75;
//V Block Height
Height = 50;
//V Block Width
Width = 50;
//Width of v Groove
vGrooveWidth = 40;
//v Groove notch depth
vNotchDepth = 2;
//v Groove notch width
vNotchWidth = 2;

//Notches in side of v block to allow for the attachment of v block clamp
sideDepth = 10;
sideWidth = 10;
//Tolerance of side notches to ensure good fit between clamp and v block
clampSideTolerance = 0.1;

//V Block Clamp Dimensions
//Thickness of Clamp
clampThickness = 10;
//Width of Clamp
clampWidth = Length*0.25;
//Height of Clamp above v block
clampHeight = 35;

//Dimensions of nut/ bolt support on top of v block clamp
//Thickness of Nut support
clampNutSupportThickness = 15;
//Width of nut Support
clampNutSupportWidth = 20;

//Dimensions of Nut and Bolt for securing parts in V block
//Diameter of bolt
boltDiameter = 8.25;
boltLength = 50;

//Width of nut- measure corner to corner distance on nut
nutWidth = 14.75;
//Nut thickness- measure thickness of nut
nutThickness = 7.0;

//Diameter of Bolt Knob
boltKnobDiameter = 20;
//Height of Bolt Knob;
boltKnobLength = 20;
//Number of knurls around Knob Diameter
boltKnobKnurlNum = 15;
//Depth of knurls
boltKnobKnurlDepth = 1;
//Width of knurls
boltKnobKnurlWidth = 1;
//Angle of knurling
boltKnobKnurlAngle = 100;