double taper turning.

[Wildman]

Having bought some chisels for an 1880's hand mortiser I found they were not all standard tapers, the ones I bought were smaller in Dia than the ones I needed so the decision was made to sleeve them. I started by drilling then boring the taper to receive the smaller taper. Then without changing the setting made a mandrill, with a male taper to receive the new sleeves. For me that was easy as the D13 chuck would not unwind in reverse, so I just repositioned the a tool the the rear and cut an identical taper. (to get the the angle right) The mandrill included a thread to take a nut so the sleeves would be held in place. The mandrill was countersunk both ends so it could run between centres. Most people could then offset the tailstock for the required larger external taper. but I have a gadget to keep tailstock in alignment and use a false moveable centre. The allows me to use power feed and save old fingers winding the topslide to do numerous sleeves. When I am next in the workshop I will take some photos to add.

 

[Wildman]

having drilled a pilot hole the smaller taper was bored. Rust has been a really bad problem in my workshop this year as you can see

 

[Wildman]

topslide remained at the same setting and lathe run in reverse as I cut the male taper on a mandrill, as both the sleeves and mandrill were cut at the same setting they were a perfect fit.

 

[Wildman]

finally turning the outside taper on the sleeves, can be done the same way as previous taper but easier to turn on a mandrill between centres and offsetting the tailstock. Though in my case I used my adjustable centre and do not need to reset the tailstock afterwards. The beauty of this is I can use power feed and the topslide is still set to the correct angle if I need to make additional sleeves. in practice the taper was sufficient to hold the sleeve without the spacer and nut. (Note using the adjustable tailstock centre it is important to have the slideway parallel to the bed so always take out and rotational backlash in the tailstock every time. Next job is to derust the lathe. It was covered but made no difference. Oh the joys of an unheated workshop.

 

[TFrench]

I've found boeshield pretty good at rust prevention. It's expensive but it beats cleaning rust off!