"I was concerned for many years about all the very short unusable "leads" from the various mechanical pencils. I eventually milled a v-shaped trough in a heat resistant plastic. I laid the short leads in there end to end, carefully squaring each end first. I then rigged two electrodes, experimenting with the correct current, and found I could weld all these short pieces together and put the finished product back in the pencil. A little bit of work, but well worth it."