Project: Lathe Hand Crank
Friday, May 12 2017
Sometimes I want to turn the lathe very slowly. Turning the chuck by hand requires two hands and still limits the amount of torque that can be applied. I’m going to build a hand crank based upon various ideas I’ve seen on youtube and web pages. The hand crank I’m building will match stock I have on hand.
I’m starting with an expanding arbor that will fit in the spindle. The spindle access hole is about 24mm in diameter so I will start by turning down some stock to that size. Of course the only stock I had of the desired length and thickness was square. No matter. I’ll make it round. It’s 12L14 steel and machines very well.
The magic tool picture shows the turning in process. My phone somehow managed to capture everything except the head of the turning tool. At this point I was using a carbide tool for higher speed rough turning.
I switched to an HSS tool bit to get a better finish. When the end of the part was at 24 mm I switched to the 3-jaw chuck and reversed the part to finish turning the square stock round. I turned about 75mm of stock to a diameter of just under 21mm. The goal was a nice sliding fit into the end of the spindle.
Saturday, May 13 2017
As I got close to the desired size I removed the chuck with part for some test fits. As the first picture shows, the 24 mm opening in the lathe gear cover is not concentric with the spindle. I took a file to the lathe gear cover to get the part to fit in the spindle without rubbing.
I drilled a 6.5 mm hole through the rear of the arbor. The front end was drilled 10 mm to a depth of 75 mm, meeting the 6.5 mm hole. Then I bored an 8° taper in the front end end. Eventually I’ll machine a tapered plug that will cause the arbor to expand when tightened by a rod, locking the arbor to the spindle.
Not shown is the machining done to the rear end of the part. I turned the rear end down to 1/2" (12.7 mm). Why the switch from metric to inch? I have a 1/2" reamer that will be used, soon. I don’t have any metric reamers.
Sunday, May 14 2017
To finish the arbor I cut four relief holes then used a slitting saw to add four slits. This is what will allow the arbor to expand when the to be machined plug is pulled into the taper at the end.
I blued the arbor and turned my attention to the parts needed for the crank end.
Monday, May 15 2017
I faced the ends of a scrap piece of 1 1/2" aluminum and then drilled and reamed a 1/2" hole in the center. It is a tight fit on the end of the arbor. This is my end piece that will allow a crank to be easily be fitted. I’ll use loctite to semi-permanently mount the end piece when done.
The crank is made from some 1/4" by 1" bar. I’m using a 100 mm section. If that turns out to be too short I’ve more bar stock to make a longer crank. I drilled a 1" hole near the end and filed the corners down so all is smooth when the end piece and the crank are fit over the end of the arbor. I then drilled a 6 mm hole in the crank and marked and drilled a matching hole in the end piece. This is for a pin (yet to be made) to transfer crank motion to arbor motion.
Still to be done: Crank pin, crank handle, tapered plug, adjusting screw for tapered plug, final assembly.
Tuesday, May 16 2017
I turned some brass to a cone matching the 8° taper in the arbor. The end was threaded M6 x 1.0 for the rod that will be used to pull the cone into the arbor, causing it to expand. When that was done I swapped out the 3-jaw chuck for the collet chuck for the next bit of work.
I made a pin out of some tool steel. The pin is held in the crank handle by some retaining compound. Except I ran out of Loctite 638. I did have some Loctite super glue. It seems to be doing the job. If it doesn’t hold I’ll re-fasten with the 638 once I get some more.
Some 6 mm all thread would have been perfect for the tightening rod. To bad I didn’t have any. Instead I turned down the ends of 1/4" 12L14 to 6 mm for threading. Why 6 mm? I want to use a 10 mm nut on the tightening end as everything else on the lathe uses metric tools and a 10mm nut is small enough to not get in the way of putting the crank on and off.
And this is what the crank looks like when it is put together. I used super glue, again, to fasten the end piece to the arbor. All that is needed for installation is an M6 nut and washer. I also have to make a handle for the crank. I was going to use an old wrist pin in my junk pile, but it is not as long as I’d like.
When looking for a handle I found a piece of left over 1/2" tool steel that was about the perfect length. I put a 1/2" hole at the handle end of the crank and used my super glue one more time to hold the handle in place. A little work with a file to round the corners on the crank and I’m done. Unless I decide to blue the crank. Not sure. I can do that at any time.
Friday, Jun 9 2017
The super glue holding the aluminum end piece to the arbor didn’t hold up to serious torque. I first thought the arbor was turning in the spindle. Nope, the aluminum end piece was turning on the arbor. I took it apart and cleaned everything well with alcohol and then put it together with 638 retaining compound. I’d bought a new bottle since starting this project.