NDIY    I’ll be running it from a rotary converter. This drill is designed to run up to 18000RPM. It should come with a set of pulleys enabling this but unfortunately mine has only the smallest which will only give me approx. 2800RPM. As I already have a mill that can do 3600RPM I need to make a large pulley so I can get the benefits from this unit.

I intend to drill small holes in bearing rings for lubrication feed, so high speed will cut down the time spent doing this…but of course the real pleasure is just bringing and old machine back to a full life 🙂

Gerry

After some internet trawling on the likely standard that Herbert have used for this pulley taper, it seems that Fulmen was half right. From some time ago it would seem that industry has generally agreed that the standard for “non-stick” tapers should be 3.5″/foot. This is close to a ratio of 0.3 but not quite.

When it comes to the angle subtended by this specific gradient, there is lots of variation in articles on the net. I ‘think’ this could the result of different ways of measurement leading to people to use Tan instead of Sine and vice versa.

My gauging ball method determined and angle of 16deg 42 mins on my pulley. The 3.5″/ft spec gives a subtended angle of 16deg 36min. This looks surprisingly close but may be more from luck than anything else. However, this raises another question in my mind which time-served designers and machinists may be able to answer. What would be a typical angular tolerance for manufacturing the taper used to couple two parts in a machine?

Gerry

Not time-served, but I don’t think tapers were made by measuring angles, so no need for an angular tolerance.

Dave, surely every feature on a good quality engineering drawing has to have a tolerance?!

You are right that in the process of manual machining the angle is generally achieved by ratios, but I cannot recall a ratio being specified on an engineering drawing. It’s usually specified in degrees and then converted by the machinist, process engineer or cnc programmer for production?

Gerry