# New Operator



## dcms (Nov 20, 2012)

Let me start by saying I am brand new to a lathe.   I am mostly in the process of learning how to operate my SB 10k safely and without damaging anything... including myself.

So far, I have it cleaned up and running.  Overall, it is in pretty good shape.   No busted gears, etc.

I am having a problem running the lathe at the slow spindle speeds.   

Following what I have read in the SB book on "how to Run a Lathe", I have followed these steps.
1.  After opening up the cover to the back gears, I pulled the "bull gear lock pin" out to allow operation of the back gears.
2.  Next I pulled the back gear lever forward to engage the back gears.  

Note:  At this stage, everything seemed to be working.   It appears thet the back gear lever works on a cam, but on my maching, it doesn't appear to lock.

3.  I closed the cover and turned the machine on.  However, each time I do this, the "back gear lever" pops to the rear position and the back gears disenage.  

After going through this process a few times with the same result, I concluded that I must be missing a step.  Everything seems to function and based on my visual inspection, nothing is visably broken.  

Your help is appreciated.  I would like to get the slow speeda working if possible.  

Thanks again.  I hope this is not too stupid a question.


----------



## HSS (Nov 20, 2012)

On my 13"SB there is a screw on the bearing block on the end of the backgear shaft opposite the handle. This screw can be tightened to make the backgear movement stiffer so that it doesn't back out when you start cutting. Hope this helps

Patrick


----------



## FastPauly (Nov 20, 2012)

HSS is definitely correct...my back-gears were kicking out the same way you describe.  A minor adjustment to the screw mentioned and all is well now.

FastPauly


----------



## dcms (Nov 21, 2012)

HSS said:


> On my 13"SB there is a screw on the bearing block on the end of the backgear shaft opposite the handle. This screw can be tightened to make the backgear movement stiffer so that it doesn't back out when you start cutting. Hope this helps
> 
> Patrick



Thanks.  My 10k doesn't have a screw on the end opposite the handle but there is one on the same side of the handle.  Won't be able to do anything on T-day but will look closer on Friday to see if that screw does anything.  

I have another question you may be able to answer.   I have, what seems to me, a lot of slop in the compound rest in the direstion of the lead screw that crosses the main bed of the lathe.   It must be at least 1/8".  The gibbs on the side take out the excess play in the direction perpindicular to the lead screw, but I don't see anything to reduce the play parallel to the lead screw.  Is this normal?  Don't you want it tighter when turning a part to maintain tolerances?

Thanks for the help.

Tim


----------



## ljbenjam (Nov 25, 2012)

dcms said:


> Thanks.  My 10k doesn't have a screw on the end opposite the handle but there is one on the same side of the handle.  Won't be able to do anything on T-day but will look closer on Friday to see if that screw does anything.
> 
> I have another question you may be able to answer.   I have, what seems to me, a lot of slop in the compound rest in the direstion of the lead screw that crosses the main bed of the lathe.   It must be at least 1/8".  The gibbs on the side take out the excess play in the direction perpindicular to the lead screw, but I don't see anything to reduce the play parallel to the lead screw.  Is this normal?  Don't you want it tighter when turning a part to maintain tolerances?
> 
> ...





Tim,


Like you I am new to lathe work. Picked up mine last winter and have been “playing” with it to learn.  Also like yours, I have a lot of slop in the cross feed screw.  Almost a full turn as I am trying to set the bit.  I have had to “get use to it.”  

Hopefully, one of the very experienced folks will give you a better explanation than I am.  I asked this same basic question when I was getting started.  Look for that post in the either the newbie section or general forum.

Larry


----------



## Tony Wells (Nov 26, 2012)

That would be known as backlash, and all leadscrews have _some_. New ones naturally have less, older ones with wear have more. There is a nut attached to the cross-slide that the leadscrew runs through to move it. Generally they are made of brass/bronze. Depending on the lathe, it might be available as a repair part, or you may have to make your own if the backlash really bothers you, or eventually it starts to "jump" a thread. Eventually it will. But many, many old lathes are run with quite a bit of backlash with no problems other than the operator getting used to it. It's standard practice to always dial _towards_ the part when setting a position for a cut. If you overshoot the desired position, you simply wind it back out far enough to get past the backlash and come up to the point again. After a while, it becomes second nature. In reality, it doesn't have an effect on accuracy. You will see a problem with wear on the leadscrew sometimes that does affect accuracy when it is supposed to move 0.010 and the lead is off and it doesn't move the tool 0.010. Some folks simply stick an indicator on it and ignore the dial graduations at that point, or some do it just to double check themselves or enhance accuracy when taking the finish cuts.

Some lathes have a provision for adjustment of the nut, and the nut sometimes is actually either split, or two pieces and they can be spread apart, effectively reducing the "slop", or backlash in the leadscrew. Don't try to get it to zero though. If you set it tight in one place in the travel, it will likely be too tight in another, or still too loose. You'll have to settle for a happy medium unless you replace both the leadscrew and the nut as a set.


----------



## 12bolts (Nov 26, 2012)

dcms said:


> It appears thet the back gear lever works on a cam, but on my maching, it doesn't appear to lock.
> 
> 3.  I closed the cover and turned the machine on.  However, each time I do this, the "back gear lever" pops to the rear position and the back gears disenage.



Hi Tim,
The adjustment screw that limits travel on your back gear engagement should be set so that the cam moves the gears slightly over centre. This stops them from disengaging. You want the gear mesh to be as smooth and quiet as possible, (which is often still rattly and noisy). If the gears are "howling" the mesh is generally to loose, and if they are "whining" then the mesh is probably to tight.

Cheers Phil


----------



## dcms (Nov 28, 2012)

I had a chance to tighten the adjustment screw on the back gears.  Unfortunately, tightening the screw didn't improve things.   Does anyone know of a fix if the adjustment doesn't help?


----------



## 12bolts (Nov 28, 2012)

Tim, I may be missing something here, and what I'm using for reference is a SB9 clone but does the adjustment screw you refer to 





dcms said:


> I had a chance to tighten the adjustment screw on the back gears.


 look something like this---->
	

		
			
		

		
	




You shouldnt be trying to adjust it "tight". This screw provides a stop for the back gear engagement. If you back it right out you should be able to get the back gear lever to rotate a long way past where it should stop at. The adjustment should be made so that when you move the lever to engage the back gears you should feel the mesh get slightly too tight and then go past, (over centre) that to suitable backlash. By getting the adjustment correct here the mesh is not to tight, not to loose, and, the important part, for it to jump out of gear it would need to overcome the effect of tightening the mesh even further.

Cheers Phil


----------



## dcms (Nov 29, 2012)

Thanks Phil

My 10k is similar.    I tightened the screw but no change.... the gears keep popping out of mesh.  I am wondering if I adjusted it too tight????   What happens if you go too far?   

I will try to back it out to see if I can feel the high spot you mentioned in your response.

Thanks again.

Tim


----------



## dcms (Dec 3, 2012)

I wanted to report success.  

After fiddling with the one screw I originally found, I did a little more looking on the web for a schematic of my lathe.  

Found an excellent manual previously published by the Army for the 10k.  It had a great picture and some instructions on how to adjust the back gears.  

My problem was there are actually two adjustment screws. One on each end of the back gear shaft.   Once I adjusted the correct screw,  I was able to adjust the cam to keep the back gears engaged.  

It is working great right now.  

I really appreciate everyone's help on this.

I would post a copy of the schematic and the adjustment instructions that I found on the net, as well as a photo of my lathe,  if anyone could tell me how to attach a pdf or jpg photo to a thread.

Thanks again.

Tim


----------

