Drawbars for milling tools and work-holding

March 2010

Drawbars for tooling and work holding

Drawbars are very useful, not only to hold MT3 tooling on the mini-lathe but also for work-holding through the spindle bore.

Drawbar for MT3 tooling

For milling work on the lathe, made this drawbar for MT3 tooling for the lathe spindle. A piece of 18mm hex steel stock was turned down to 12mm and a M12 thread made on the end. Made the drawbar with the hex end 25mm long, so it can be mounted and removed without the need to remove the gears cover on the mini-lathe. A 5mm thick washer was made to fit the spindle. A circlip fits a groove on the drawbar to keep the washer in place.

The washer is flat, with no register for the spindle. This is to ensure that the MT taper will fit properly and that the MT taper will align the drawbar and washer, not the opposite.

Drawbars for work holding on the lathe

From the same 18mm hex steel stock, made these two drawbars for work-holding. Sometimes I need to hold parts on the faceplate that can't be clamped other way. Recently I had to enlarge a chuck register that was undersized. Made it with the M8 drawbar on photo through the spindle, faceplate bore and chuck bore, clamping the chuck rear with a single large nut made for it.

Made also a M6 drawbar for smaller jobs, for parts that can be clamped only by a small center hole.

Basically these drawbars are a long nut, a large washer and the circlip to keep the washer in place. Unlike the drawbar for MT3 tooling, these ones have washers with register to center the drawbar on the spindle. One is M6 threaded and the other M8 threaded and are used with threaded rod.

These drawbars are not to be used when a part can be chucked or clamped on the faceplate. They are an alternative for when there is no other way to hold a part on the faceplate. They are not as resistant as clamps and so care and light cuts are needed for the part not to slide.

Whenever it is possible I use three clamps on faceplate, aside the part being turned, to prevent it from sliding.


Drawbars for work holding on the mini-lathe

Like the first drawbar for milling tooling, these ones were also made with a 25mm long nut, so they can be assembled and disassembled without the need to remove the gears cover.

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