Vertical Chuck Design


In Varanasi there is a whole community which relies on earnings from producing wooden toys and artifact. The Banaras toy makers are renowned for their skill and variety. The cost of manufacturing and labour is low and this is reflected on their income. As a result, they use primitive technology and tools. There is absolutely no concern for safety.

The tools used/ machines used: Locally manufactured and assembled lathe. The components of these lathes perform basic functions seen in conventional lathes but not as effective. Some workhouses have single lathes some have multiple lathes being powered by a motor.

The driving motor for powering the spindle is external to the lathe. A belt drive connects the motor and the spindle. The belt drive is routed from motor through the shaft high above the workspace and then shared among several spindles.  The lathe is low to the ground which makes the worker sit on the floor and work. Headstock is made of wood through which a spindle is passed through from one side to another. The power comes from one end and is delivered to the chuck on the opposite side.  The foundation of headstock is around 3ft -4ft underground. This gives it more stability and damps vibrations effectively.  The spindle has hollow cylinder which is used as the chuck. The job is first reduced to the size of the opening of this chuck and hammered into this work holding device. The other end of the spindle is a hollow ring with slightly larger diameter than the spindle. This ring acts as a temporary diversion of power which is required for on-line adjustments of the job and regulating the speed during certain operations. The tools used for the operations are all locally made too.  They are all handled manually with bare hands.  Long jobs cannot be worked upon as there is no tailstock to support the pieces. A tool rest plays an important role for supporting the tool. It is free to move and is positioned with respect to the axis of rotation as per the need.

The whole system has been developed with frugal innovation or “jugaad” in mind.

Frugal Innovation is a design innovation process in which the needs and context of citizens in the developing world are put first in order to develop appropriate, adaptable, affordable, and accessible services and products for emerging markets.

The 10 Core Competencies of Frugal Innovation were developed by the Frugal Innovation Lab at Santa Clara University. The 10 Core Competencies are:

  1. Ruggedization
  2. Lightweight: Portable for varying transportation options.
  3. Mobile Enabled Solutions: connectivity anytime, anywhere
  4. Human Centric Design: easy-to-use, intuitive designs that require little to no prior knowledge or training to utilize
  5. Simplification: minimalist features and functional requirements
  6. New Distribution Models: non-conventional channels and access
  7. Adaptation: leveraging existing products, inputs and services
  8. Use of Local Resources: sourcing without importing equipment or materials.
  9. Green Technologies: powered by renewable resources
  10. Affordability: low input and operation costs

The solution which has to be obtained for this problem also has to be within this domain. The cost, manufacturability, Materials available for the system etc. should not be another problem for the community.

Process for making a piece:

The raw material is first made circular and then one end is reduced to make it fit into the chuck.  The fitting is done by hammering the piece into the cylinder. After fixing the job power is supplied and worked upon. The speed of the spindle remains constant and there is no setup for varying this. This limits the type of operations that can be performed. The worker takes required tools and makes the required part. For finishing operation, the worker used sand paper and then lac is added on the surface.

Existing problems:

The first problem we observed was with the ergonomics. The whole setup was uncomfortable for the user. He is forced to sit on the ground. The reason being the spindle was low on the ground. According to him it was easier to apply force on the work piece because he can lean over it. But he could not cite it as a problem because he was already used to it. The solution to it was to work standing on a spindle which is placed high. But he said the job would then come out of the fixture on touching it with the tool.

The second problem is the slipping of the job from the fixture. The existing fixture was just a hollow iron ring fixed to the spindle. The job is hammered in it. But when the job rotates at high RPM and the tool strikes against the irregular projections in the wood pieces the job sometimes flies off. So we need a chuck with jaws that can hold an irregular job. But again the existing high cost lathe chucks cannot be used. And it has to be made locally to avoid high cost maintenance.

The third problem as mentioned by the artisan was about mass production. He encouraged our idea of a replicator which would produce multiple pieces of the same job at the same time.

The 3 problems stated above are solved through different part solutions, which in turn will result in the system solution.  The part solutions are described in detail in the next section.

Problem Definition

Varanasi, the cultural center of India is rich in the craft of toy making and is gifted with a community of craftsman who have been practicing this craft and passing it on from one generation to other.

But as the craftsmen make some innovative prototypes in Wooden Craft, problems faced by them were

Proper ergonomics
Safer Machines
Mass production
Standardization of workpieces
Variation in Products

“Design a lathe on which the worker can work for longer hours.”

The problem definition arrived will lead to system solution, wherein the system solution is a combination of part solutions. The problem could be visualized in two perspectives, either designing the solution with the factor of feasibility and the conditions prevailing in the working atmosphere or designing the solution with the available resources in the best possible manner and trying to fix it into the working environments through iterations.

Previous Part Solutions

V-Block vice was the inspiration. The Vs provide enough surfaces to hold the cylinder in position. Teeth have been provided to extend the range of the diameter it can hold. The closing and opening of the jaws happen when the bolt is rotated counter clockwise and clockwise respectively. It is a simple mechanism in which the bolt has half-length of right hand thread and other half is left hand thread. The Vs have a nut each as their base with corresponding threads.

The challenges we found in the design we came up with was:
1. Material Wastage due to the length of the protruding part of chuck
2. Artisans takes more time to tighten the workpiece to the chuck, compared to the existing mechanism
3. Unequal weight distribution leads to unbalanced forces
4. Manufacturing of Left hand threads.
5. Cranking lever should be attached and detached for tightening / loosening of the workpiece from the chuck.
6. Coupling the chuck to the powering shaft effectively.

Part Solutions

Sl. No Need Part Solutions
1 Proper ergonomics Raising the Lathe Bed Level
2 Safer Machines Proper Work Holding Mechanism
3 Mass production Replicator Mechanism
4 Standardization of workpieces Proper Centering & Template Guiding


5 Variation in Products Tailstock Support Adjustable Chuck
6 Hollowing Tool position Indication Mechanism

System solution

As the problems were not pertaining to a single part or a machine redesigning the entire system seemed the most appropriate and, more importantly, necessary.

Productivity, ergonomics and safety happen to be the three most important factors which directly influence the working hours on the lathe.

To increase productivity a Replicator system which produces multiple pieces at the same time can be a valid solution. But there are a few conditions to be satisfied.

  • The worker will/may have control over just one job and the rest of them are machined through linkages. This means all the pieces must be identical. Wood logs which are cut are never the same. The non-uniformities, deformations etc. are all the causes. So in order to make it work in replicator the raw material must be first made identical. This means a separate worker must be assigned with this job prior to replication process.
  • After the uniform jobs are made, the replicator takes the jobs and operates on it. There are a few configurations possible for the replication system.
  1. Main spindle Horizontal and rest are parallel to it:

In this set up, the replication can happen only with two pieces adjacent to the main spindle. Both left and right to it or above and below. This restricts the production to maximum three pieces, which may be beneficial but not a significant change.

  1. Main spindle is vertical and rest are parallel to it:

In this set up, the spindles can be arranged around the main spindle or next to each other in a line making them pretty close to each other and occupying lesser floor space.

  • Replicator cannot be used for finishing as individual attention is required. Once the replication is done, the pieces can be sent to another worker whose job is to finish it and paint.

To implement this system, we considered four fundamental problems

  1. Single unit: First of all, a vertical lathe is unusual. We first tried to find out where it’s used in the industry. Train wheels are machined using huge vertical lathes. That meant we could work on the concept and think of something on a smaller scale. A single unit has to made first to check how it works and then multiplying this unit can help us setup the system.
  2. Replicator: Once a single unit is made. Setting up several units next to each other and analyzing the best and efficient configuration is essential.
  3. Tool mechanism: The tool mechanism or the tool movement to work on several units at the same time is the most difficult part of the solution. This goes along with the configuration of the replicator. The present tools may be ideal for the horizontal lathe but we cannot use these. A tool rest is also required as a support during machining.
  4. Hollowing: This is an operation performed to remove material inside the log. This is an easy operation on a horizontal lathe with his current set of tools. But for a vertical lathe the condition is different. Hence a new way of hollowing has to be made.

Work in Progress

After successful remaking of the chuck, the next step is the tool movement mechanism and replicator configuration which are mostly related. Several Linear mechanisms and radial movement mechanisms were analysed. But most of them aren’t feasible. This phase is still in progress and can be worked upon after more research into mechanisms which are simple and cheap.


The Workspace redesigning of the Banaras Wooden toy makers is a very unique problem and at the same time complex.  More research into material used, feasibility of mechanisms and manufacturing processes used by the local community is essential. As of now all that could be deduced for the benefit of the worker from our findings is that he has to be able to work for longer. And our solution must provide the right conditions for him to do so.

From the QFD analysis we obtain the fact that the Height of the lathe is the most important of all characteristics. We questioned the basic setup of lathe itself in order to counter this. With the vertical setup with replication he may not have to sit on the ground. The solution is not yet complete but we have a direction.

The initial problem which was raised regarding the safety of the chuck has been solved by altering the simple nut and bolt assembly. The intention was to provide the worker a work holding device which does not let the job fling and is also quick to fasten the piece.

To implement the system solution more research and analysis is required. Hence it is still in progress









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