This article might be a useful starter.

Folks who wonder if nylon gears in mini-mill and mini-lathe headstock might be interested to know this is a feature shared with the Denford Synchro.

Neil

Delrin & Hostaform are brand names for FAMILIES of resin. Within each there may be many different grades with tailored properties.

The article compares homopolymer actetal, vs copolymer acetal (without details of composition) vs Nylon 6. Plastics rapidly become fiendishly complex, even within a family. Don't expect a simple answer.

The original Denford gears were made form a material called Technyl A90, whatever that is, probably a nylon as the name suggests. I have made quite a few replacements from Delrin.

I found that the original gear was rather mis-shapen on my lathe and it used to bind after it was worked hard and the heat caused it to swell. The delrin replacement never suffered any of this.

I have always reckoned that gears should be unbreakable not fail safe and that plastic of any sort for this job is used because it is far cheaper to injection mould a plastic gear than to machine a steel one. A sheer pin device would be used if protection was considered necessary but I have known a Tufnol gear to be used in a gear train to reduce noise. If my minimill gears ever strip I shall replace them with steel/cast iron ones and grease them well. Colin.

William, I stuck with plastic gears for the reason that Ketan illustrated, better to replace a sheared plastic gear than an expensive burnt out electrical board. I don’t use my minimill that frequently because I now have a Champion V20 mill which I have fitted with DRO’s and other mods, giving me much more machining capacity. Glad I was able to help solve your issue.

Dave W

Depends on the machine. The lowest spec. mini-lathes don't have. Also, on such mini-lathes, and even on high/low geared mini-lathes which have an overload protection, there is a 'user' element to be taken into consideration. If a new user, then failure – damage is related to how the stoppage occurred – heavy handed due to incorrect/improper/inexperience use?… in which case, probability of gear breakage (nylon) or board failure or both, could be equal. If metal gears + entry level electronics + new inexperienced user, then board failure event probabilities increase. There is no clear reason. Just probabilities related to user.

Ketan at ARC.