Lever feed tailstock
This project developed out of a thread on the Model Engineer website in which John Stevenson showed a method of adding a lever feed to a mini-lathe tailstock. His method was based on that used in some Clausing lathes.
The project requires a few extra components but very little modification to the existing standard tailstock, The main new components are:
1. A block which is mounted on the right hand side of the tailstock as shown above. This is fixed to the tailstock with two M4 screws. The old tailstock must be drilled and tapped to accept these screws.
2. A dummy barrel is required. This is shown protruding form the block.
3. A system of levers to slide the barrel into the block and tailstock.
4. A stop block on the extreme right. This serves, together with the block attached to the tailstock, as anchorages for the lever system.
5. An extended feedscrew. This is inside the barrel and cannot be seen in the header photo. John Stevenson made an extension for the existing feedscrew but I have made a totally new feedscrew.
6. There are a number of minor components like the locking pin and lever which protrude from the front of the block.
The project requires a few extra components but very little modification to the existing standard tailstock, The main new components are:
1. A block which is mounted on the right hand side of the tailstock as shown above. This is fixed to the tailstock with two M4 screws. The old tailstock must be drilled and tapped to accept these screws.
2. A dummy barrel is required. This is shown protruding form the block.
3. A system of levers to slide the barrel into the block and tailstock.
4. A stop block on the extreme right. This serves, together with the block attached to the tailstock, as anchorages for the lever system.
5. An extended feedscrew. This is inside the barrel and cannot be seen in the header photo. John Stevenson made an extension for the existing feedscrew but I have made a totally new feedscrew.
6. There are a number of minor components like the locking pin and lever which protrude from the front of the block.
The parts
The block was made from a piece of steel 40 x 38 x 25 mm.
The two holes in the top are attachment points for the lever system. The larger of these was drilled and tapped M5 whilst the smaller one was drilled and tapped M4.
The two 4.5mm holes on the diagonal of the face are for the 4 mm screws to attach the block to the tailstock
The larger hole at the bottom of the side face is drilled out 8mm for the locking pin
The two holes in the top are attachment points for the lever system. The larger of these was drilled and tapped M5 whilst the smaller one was drilled and tapped M4.
The two 4.5mm holes on the diagonal of the face are for the 4 mm screws to attach the block to the tailstock
The larger hole at the bottom of the side face is drilled out 8mm for the locking pin
The 4.5mm holes for the attachment screws are counterbored 7.5mm on the front face.
The M5 screw on the side locks into a groove on the side of the dummy barrel. Thiis allows the barrel to slide but not rotate.
The M5 screw on the side locks into a groove on the side of the dummy barrel. Thiis allows the barrel to slide but not rotate.
The locking pin is a piece of 8mm round steel. This was turned down and threaded M5 for 10 mm at one end.
It was placed in the block before the large 22 mm central hole was bored. It was locked in place during the boring operation by an M4 grub screw though the base of the block..This ensures that the scallop taken out of the pin exactly matches the radius of the hole in the block.
It was placed in the block before the large 22 mm central hole was bored. It was locked in place during the boring operation by an M4 grub screw though the base of the block..This ensures that the scallop taken out of the pin exactly matches the radius of the hole in the block.
The pin has been inserted into the block for this photo.
The nut on the end of the threaded section of the locking pin was made from a piece of 10 mm steel round. Six dimples have been made in the circumference of the nut with a 4 mm drill.
The nut on the end of the threaded section of the locking pin was made from a piece of 10 mm steel round. Six dimples have been made in the circumference of the nut with a 4 mm drill.
The locking lever has been placed on the nut. The lever is attached by an M4 grub screw. The lever can be attached in any of the six positions corresponding to the dimples. This enables the lever to be set in a convenient position for operation when the unit is finally assembled.
The locking lever was machined from a piece of 15 mm steel round and a piece of 6 mm round for the handle.
The locking lever was machined from a piece of 15 mm steel round and a piece of 6 mm round for the handle.
The dummy barrel was an 86 mm length of 22 mm round steel. A 4 mm groove was machined along one side almost to the end. The groove stops the dummy barrel from rotating in the block. The fact that the groove stops just before the end of the dummy barrel means that the dummy barrel cannot be pulled right out of the block.
The dummy barrel was drilled through with a 10 mm clearance hole.
The dummy barrel was drilled through with a 10 mm clearance hole.
The front end of the barrel was recessed and a bronze bush pressed into the recess. The bush is 16 mm diameter and the face is 2 mm below the surface of the steel.
The other end of the dummy barrel was also bushed. Here the bush is slightly above the surface of the steel.
The feedscrew was made from three parts.
On the right is the screw itself. This was made from a 105 mm length 10 mm steel round. This was single point left hand threaded with a pitch of 1.5 mm for a length of 80 mm. The left hand end of the screw was turned down to 6 mm for 25 mm and then the end 10 mm turned down to 5 mm and threaded M5 with a die.
The disc in the centre is 16 mm diameter and 2mm thick. it was drilled out 6 mm.
On the left is a 118 mm length of 10 mm round that has been drilled out 4.3 mm for a depth of 30 mm and then counterbored 6 mm for a length of 15 mm. The 4.3 mm section was then tapped M5.
On the right is the screw itself. This was made from a 105 mm length 10 mm steel round. This was single point left hand threaded with a pitch of 1.5 mm for a length of 80 mm. The left hand end of the screw was turned down to 6 mm for 25 mm and then the end 10 mm turned down to 5 mm and threaded M5 with a die.
The disc in the centre is 16 mm diameter and 2mm thick. it was drilled out 6 mm.
On the left is a 118 mm length of 10 mm round that has been drilled out 4.3 mm for a depth of 30 mm and then counterbored 6 mm for a length of 15 mm. The 4.3 mm section was then tapped M5.
The feedscrew was assembled and screwed together using Loctite. One end was clamped in the lathe chuck and the other in the tailstock whilst the Loctite was curing.
Once cured the feedscrew was chucked in the lathe and the central disc was skimmed.
The other end of the 10 mm round was turned down to 8 mm. .
Once cured the feedscrew was chucked in the lathe and the central disc was skimmed.
The other end of the 10 mm round was turned down to 8 mm. .
The end is turned down for a length of 35 mm and the final 10 mm threaded M8.
A small flat was made on the turned down end as shown here. The flat is 6 mm wide and it starts 18 mm from the threaded end.
A small flat was made on the turned down end as shown here. The flat is 6 mm wide and it starts 18 mm from the threaded end.
This stop block is 38 mm diameter and was bored out 22 mm.
It was cross drilled in two places. At the top it was drilled out 4.2 mm and tapped M5. At the side it was drilled 3.3 mm and tapped M4 for a grub screw.
The hex head screw at the top was machined from 10 mm hex bar and the gap between the head and the ring is just greater than 5 mm.
It was cross drilled in two places. At the top it was drilled out 4.2 mm and tapped M5. At the side it was drilled 3.3 mm and tapped M4 for a grub screw.
The hex head screw at the top was machined from 10 mm hex bar and the gap between the head and the ring is just greater than 5 mm.
I have a graduated dial on the tailstock handle. In order to make an index for this dial another ring 32mm diameter and bored out 22 mm was made and scribed with an index mark.
The lever system was made up from 5 x 14 mm hot rolled bar.
The handle was sheathed with a short length of garden hose which was a very good match to yellow colour of the Clarke lathe.
The handle was sheathed with a short length of garden hose which was a very good match to yellow colour of the Clarke lathe.
Assembly.
The first part of the assembly operation was to remove the original barrel from the tailstock. The thrust plate at the other end tailstock was removed along with the feedscrew.
The next operation is to remove the plug that closes the end of the tailstock and then drill and tap the holes for the screws that secure the block to the original tailstock.
The plug was knocked out using a length of 22 mm bar as a drift whilst supporting the tailstock on the open jaws of the bench vice.
The tailstock was clamped on a drill press vice as shown here. The dummy barrel was inserted into the bore of the tailstock and the block then dropped over it.. The block was held square with tailstock using toolmakers clamps.
The screw holes were spotted through with a 4.5 mm drill onto the tailstock.
The block and dummy barrel were removed and the tailstock drilled out 3.3 mm at the two spotted positions for a depth of 12 mm.
The holes were tapped M4.
The next operation is to remove the plug that closes the end of the tailstock and then drill and tap the holes for the screws that secure the block to the original tailstock.
The plug was knocked out using a length of 22 mm bar as a drift whilst supporting the tailstock on the open jaws of the bench vice.
The tailstock was clamped on a drill press vice as shown here. The dummy barrel was inserted into the bore of the tailstock and the block then dropped over it.. The block was held square with tailstock using toolmakers clamps.
The screw holes were spotted through with a 4.5 mm drill onto the tailstock.
The block and dummy barrel were removed and the tailstock drilled out 3.3 mm at the two spotted positions for a depth of 12 mm.
The holes were tapped M4.
The two holes after drilling. These were tapped M4
The tailstock was re-assembled with the original barrel.
The tailstock was re-assembled with the original barrel.
The block was mounted on the end of the tailstock using M4 screws. The screws were not tightened at this stage.
The new feedscrew was greased up and then slid into the dummy barrel.
This was then inserted in the block as shown here. It is necessary to screw the feedscrew into the original barrel at the same time.
The groove in the dummy barrel was aligned with the screw at the back of the block and this was tightened into the groove.
Once the dummy barrel was as far in as it will go then the clamp pin nut on the front of the block was tightened. The two screws that hold the block on the tailstock were tightened.
This was then inserted in the block as shown here. It is necessary to screw the feedscrew into the original barrel at the same time.
The groove in the dummy barrel was aligned with the screw at the back of the block and this was tightened into the groove.
Once the dummy barrel was as far in as it will go then the clamp pin nut on the front of the block was tightened. The two screws that hold the block on the tailstock were tightened.
The stop block and index ring were added and their retaining screws tightened into the groove in the dummy barrel. The feedscrew handle was then attached.
Finally the lever mechanism was bolted on as shown here.
This modification to the tailstock has a number of benefits. Firstly, tanged tooling can be accommodated in the tailstock. Secondly, the tailstock travel is increased and thirdly it gives the possibility to instantly withdraw a drill using the lever. The lever mechanism can also be used for "peck" drilling small diameter holes.
In use if the dummy barrel is locked fully out of the block using the locking screw then the tailstock operates normally using the handwheel. If the main barrel is retracted and the dummy barrel unlocked then the tailstock can be operated using the lever. Intermediate locking positions of the dummy barrel permit use of the handwheel to advance the chuck which can then be withdrawn using the lever after unlocking the dummy barrel.
In use if the dummy barrel is locked fully out of the block using the locking screw then the tailstock operates normally using the handwheel. If the main barrel is retracted and the dummy barrel unlocked then the tailstock can be operated using the lever. Intermediate locking positions of the dummy barrel permit use of the handwheel to advance the chuck which can then be withdrawn using the lever after unlocking the dummy barrel.