monophoto
Member
A recent discussion suggested that it might be useful to provide some general information on drawbars.
Essentially, a drawbar is a safety device that is used to draw male morse taper fixings into the female tapered throat of a lathe headstock spindle, and retain those tapers so that they don't inadvertently come out as the lathe spins. Drawbars are always recommended when using a morse taper without the tailstock providing additional restraining support at the other end of the spindle. One end of the drawbar screws into a female thread in the small end of the morse taper, while the other end is held in place with a nut that is snugged up against the handwheel, drawing the taper into the headstock spindle. The most common example might be if a Jacobs (drill) chuck is mounted in the headstock for drilling.
Drawbars are most easily shop-made although presumably one could purchase one. Essentially, a drawbar consists of a length of threaded rod (ordinary hardware store all-thread rod is fine), and a nut of some sort to secure the outboard end of the drawbar to the handwheel on the left side of the headstock. Before making a drawbar, check the dimensions of the threads on your tapers to make sure that you are using the proper rod. That said, it is typically the case that MT2 tapers are designed to receive 3/8"-16 threads, while the lathe headstock bore can accommodate a 3/8" diameter rod. Mini-lathes with MT1 tapers usually receive 1/4"x20 threads.
This sketch illustrates the components:
The nut that holds the drawbar on the outboard side of the headstock is turned from two scraps of wood. There should be a cavity in one piece to hold a nut of the appropriate diameter and threading. Alternatively, it is possible to use a T-nut or a threaded insert. Make the nut as plain or fancy as you wish.
I generally put a piece of heat-shrink tubing over my drawbar, leaving about 1/2" of rod exposed at the morse taper end. That prevents the sharp edges of the threads from abrading the inside of the headstock bore when the rod is inserted or withdrawn. The tubing should be slightly shorter than the length of the bore so that it doesn't interfere with the nut.
Leaving sharp edges on the left end of the drawbar is dangerous - DAMHIKT. As a minimum, file or grind the left end to form a smooth ball. Alternatively, I have turned a rounded cap from a scrap of HDPE that threads onto the end. Your left hand with thank you!
When using a drawbar, be aware that it will pull the male morse taper into the female taper on the lathe spindle rather snugly, and removing the taper usually requires gently tapping the rounded end of the drawbar with a mallet.
Essentially, a drawbar is a safety device that is used to draw male morse taper fixings into the female tapered throat of a lathe headstock spindle, and retain those tapers so that they don't inadvertently come out as the lathe spins. Drawbars are always recommended when using a morse taper without the tailstock providing additional restraining support at the other end of the spindle. One end of the drawbar screws into a female thread in the small end of the morse taper, while the other end is held in place with a nut that is snugged up against the handwheel, drawing the taper into the headstock spindle. The most common example might be if a Jacobs (drill) chuck is mounted in the headstock for drilling.
Drawbars are most easily shop-made although presumably one could purchase one. Essentially, a drawbar consists of a length of threaded rod (ordinary hardware store all-thread rod is fine), and a nut of some sort to secure the outboard end of the drawbar to the handwheel on the left side of the headstock. Before making a drawbar, check the dimensions of the threads on your tapers to make sure that you are using the proper rod. That said, it is typically the case that MT2 tapers are designed to receive 3/8"-16 threads, while the lathe headstock bore can accommodate a 3/8" diameter rod. Mini-lathes with MT1 tapers usually receive 1/4"x20 threads.
This sketch illustrates the components:
The nut that holds the drawbar on the outboard side of the headstock is turned from two scraps of wood. There should be a cavity in one piece to hold a nut of the appropriate diameter and threading. Alternatively, it is possible to use a T-nut or a threaded insert. Make the nut as plain or fancy as you wish.
I generally put a piece of heat-shrink tubing over my drawbar, leaving about 1/2" of rod exposed at the morse taper end. That prevents the sharp edges of the threads from abrading the inside of the headstock bore when the rod is inserted or withdrawn. The tubing should be slightly shorter than the length of the bore so that it doesn't interfere with the nut.
Leaving sharp edges on the left end of the drawbar is dangerous - DAMHIKT. As a minimum, file or grind the left end to form a smooth ball. Alternatively, I have turned a rounded cap from a scrap of HDPE that threads onto the end. Your left hand with thank you!
When using a drawbar, be aware that it will pull the male morse taper into the female taper on the lathe spindle rather snugly, and removing the taper usually requires gently tapping the rounded end of the drawbar with a mallet.
