Tuesday, January 27, 2015

Lathe: Gibs

I finally took the time to modify my lathe's cross slide and compound gibs the same way I did my mills: http://benchtopmachineshop.blogspot.com/2013/06/mill-gibs.html

The big difference was the lathe's gibs use a 60 degree angle versus the mill's 55 degree angle.

In addition, I also added two extra set screws on both the compound and cross slide in order to give it some extra rigidity. In the picture of the cross slide's set screws you can see I used three different type. The two stock ones were used due to clearance issues, the hex head was used because it's always behind the DRO read head and the hex head allows for adjustment, and the two socket head cap screws were used due to ease of adjustment. It looks a little sloppy, but aids in usability.

After cutting the pockets I reassembled everything with a generous amount of Mobil Vactra way oil on the gibs and ways. While I expected an improvement in the feel, I didn't expect the huge improvement I actually got. Even though they're snug and there isn't any play, both compound and cross slide move very smoothly and easily now. The difference is amazing.

The menagerie of set screws.

Friday, January 23, 2015

Lathe: Leadscrew Handwheel

One of my biggest problems with the lathe is the carriage hand wheel isn't very precise for Z axis movement; it's hard to always stop it exactly. I don't like using the compound for fine Z axis movement since while carriage has a DRO on it, the compound does not. Also, I want to remove the compound eventually and replace it with a solid block of steel; the compound reduce rigidity of the system and I only use it for threading operations.

I know if I could attach a hand wheel to the leadscrew then I could put the leadscrew in neutral, lock the half nut, and slowly turn the leadscrew to move the carriage.

I decided to extend the leadscrew shaft past the pillow block to make a mounting point for the hand wheel. I removed the leadscrew, chucked it in the lathe, and drilled a hole in the end. It's already been center drilled which made things easier. I then took 1/2" steel rod (stolen out of an old ink jet printer) and turned down the end of it to the same size as the new hole in the leadscrew, making sure to leave a precise shoulder. After mating the rod and leadscrew together I welded around the seam, and then turned the weld bead down in the lathe.

Leadscrew extension sitting beyond the pillow block.
I bought a hand wheel from Amazon: http://www.amazon.com/dp/B00EDKIK9G. Since it had a 10mm bore I turned the lead screw extension down to 10mm. I took the hand wheel and drill and tapped three holes in it to accept set screws. After positioning the wheel where I wanted it on the shaft I installed the first set screw fairly hard in order to mark the shaft well. I then remove it and the hand wheel, turned an extended nose on the set screw, and drilled a shallow hole at the marked spot on the shaft. I then reassembled everything and made sure the set screw seated into the hole. I then installed the other two set screws.

It ended up working really well and I now have easy fine Z axis adjustment.

I left the shaft slightly longer than necessary to allow for future adjustments.
The new hand wheel set screws are visible.