I Have 2 of those draw bars. One has the wood hand wheel and the other has one made of Bakelite. Both have the same steel mounting plate on the hand wheels and used 3AT collets. The over-all length of the one with the Bakelite wheel had been lengthened to 15". The first 3 & 1/8" of the tube, at the wheel end is .792" and the rest of it is .750". The tube OD`s may have been larger at one time. The .750" OD is perfect for my South Bend Junior lathe. With the .792" turned down to .750", a new tip to fit my 3C collets and change the length, I will be good to go.
The one with the wooden hand wheel, was modified by me to add 3C collets to my HF 7 by 10 mini lathe. ------ John