VCCA Home Forums GENERAL DISCUSSION General Discussions new lathe owner

As many may have read in the 1928 section "steering gearbox rebuild" I purchased a lathe so I could rework my truck steering gear box.
It's a nice little Atlas/Craftsman lathe. I played around making a couple practice bushings out of some cold roll and brass.
I wanted to clean up my pitman arm shaft a little as there is some room to turn it down a little and get the worn spots out where the bushings run. Took a couple light passes and then did some measuring as I didn't want the shaft to get smaller than the tapered splines on the ends. Upon measuring I am noticing that the shaft is being cut tapered from end to end over it's 7ish inches. So I do some research and talk to a machinist friend of mine, and he immediately says you have to adjust the tail stock and sends me videos on how to do it. Easy peasy, and makes sense (to a degree)

However what doesn't make sense is in watching the videos the guys are chucking up the test shaft in the 3 jaw chuck and measuring with a dial gauge from one end to the other and seeing how much their off, and then adjusting the tail stock accordingly. Now I'm not a rocket scientist but am engineer minded enough to know that unless it's a small shaft that can flex the chuck is going to maintain the centerline it's holding it on and the tailstock adjustment will do nothing more than take the tail stock center off center with the shaft.
The headstock needs to be in the same centerline as the tailstock.
The only way I can see this working is if you don't chuck the shaft and you chuck a center instead and drive the shaft with a 'dog'. And so now your turning between two center points.
Also thinking that if the case is that the headstock is not true to the bed that the cutting carriage rides on, one will never cut a 'true' bushing. I mean if your say only going an inch off the chuck you will notice probably no taper. You get a couple inches off maybe an amount one needn't worry about (IDK)
I frequently overthink things, but this whole thing of just moving the tail stock makes little sense to me.
Help from the experts.
David

Hello Dave, great to see you rebuilding a steering box,

I would like to suggest that if your pitman shaft is worn, then the case hardening, or treatment to produce a hard wearing surface has gone, I believe the best repair would be to take it and have it hard chromed, back to the original size, and then machine new bushings to suit the shaft,

I had a new 1939 pitman shaft, that has a pulley riveted in the end, the pulley was stuck, so I thought I would soak it in a rust remover solution. Well I found out after soaking half the shaft, that the wear surface on the shaft was hard chrome, and ended up with a shaft with half the hard plating removed, and unusable, so be careful whoever you clean hardened gears and the like.

Machinist move the tail stock off centre , and produce a long taper. There should be a centring calibration on the tail stock towards the front side to check and move to zero, the tail stock will have a bolt or bolts which lock the tail stock in position that has to be loosened and tightened when resetting.

When I reset the tailstock on my lathe I used a piece of rod that was larger on the ends than the mid section about 2ft long, then machined a small section on 1 end then moved to the other end without moving the cutting tool and measuring both ends and adjusting the tailstock half the difference. It is a time consuming exercise but if not correct you get unwelcome results.
Tony

Unfortunately, three jaw chucks are not as precise as we think they are. I use a collet attachment for faster and more precise alignment on round stock. A four jaw Chuck is what you should use one an already turned shaft. Align it to zero runout with a dial indicator.
You could check your headstock by using a piece of round rod trued in the four jaw. Drill your center in the end then move it out to your tail stock. You can then turn both ends down some and mike them out. You can then move your tail stock either way to achieve the same diameter at each end of your piece. Don’t trust a three jaw to be true. Three jaws are good for “close to the Chuck” work not requiring tailstock support like making bushings for example. Yes you can use them when using the tailstock but no two pieces will be exactly the same.
I have a WWII era 16” South Bend that I thought was out quite a bit because I had some issues when making multiples using my three jaw. Being an 1943 war production lathe i could only assume it had seen a tremendous amount of work and was most likely at the very least, moderately worn. After I installed a collet attachment I had .001 deviation from end to end over an 8-9” length. That’s close enough for what I make. Before the collets it was sometimes in the .015 range and that was with a trued tailstock.

I suggest that you true the bed of the lathe before adjusting the tail stock. I found a “you tuber” that

has a very good series. Check out “Blondihacks you tube”. Her lathe series is good for beginners

and as a review. Good luck. It is very fulfilling to make your own parts.