Hi Graham.As Bruce said,use a 2mm cord.I had/ have the same problem with mine (tm251 sst)and find it quite frustrating that it didn`t/won`t bump feed.Using the thicker cord (as opposed to what they give you with purchase)certainly improves an ongoing problem.The unit i bought was on special and going by the brand name i thought it would be better than what has transpired. It serves its purpose for the needs of doing small areas at my mums house but i wouldn`t buy it again.Just my opinion.There is a method of once cutting your cord to length,( i cut a metre length off),find the centre and loop it onto the little cut-away in the middle of the cord reel.(I also allow one length 150 mm longer than the other)Grasp the reel with thumb and middle finger and start turning as your other hand holds the cord (a bit like how you hold a cricket ball)(middle and index fingers on bottom,thumb covering top to stop cord winding loose).Once you get to near the ends of the cord click the shorter length into the side cord holder ( a little notch cut-out)and feed the remaining across to other side and into its side cord holder.Grab the winder so cords don`t unwind and slip into the base.It can only go in one way.Press the 'bump' end most of way in,feed loose ends of cord thru eyelet holes and push 'bump' end all the way in.After a few times of cord breakages you`ll get used to doing this almost blindfolded! Well not really but it does get easier each time albeit still a little frustrating.Now, aren`t you glad you bought what you did? Cheers GgordonN