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Accuracy issues converting a 3 1/2' bed to 4' bed. 10K

dandak

Plastic
Joined
Apr 5, 2018
Location
NE Ohio
Hello all. First post. I've lurked here awhile and decided to join today having learned so much on this forum. I have a Southbend 10K light 10" lathe that has a 42" bed. Restoring antique firearms as a hobby, and also building large telescopes to help with my astronomy hobby, I find my lathe bed is often a bit short. The 48" bed would do wonders for me. Since I really like my lathe otherwise decided to simply get the longer bed and rebuild the lathe. Wound up with a nice 48" bed and a nice leadscrew for the gear box. Both the screw and the bed are actually nicer than the 42" ones I had been using. Great. Here we go. Switched out the bed, leveled it, rebuilt the lathe, switched out the leadscrew and tried her out.

Problem #1. On the 42" bed, when I tighten the two bolts in the back of the saddle that hold the saddle retaining plate on, the saddle is a nice slide fit on the bed. With the 48" bed, I need to leave the bolts loose about an 1/8" or the saddle is firmly locked onto the bed! Kind of odd. Comments? Should I machine a spacer the exact thickness I need so I can tighten these bolts?

Problem #2. Severe accuracy issues. Turning an aluminum or brass rod I find the diameters are out about 0.0015"/inch. I tested a 6" run at the headstock and also near the middle of the bed. In both cases the diameter was 0.009" to 0.010" out! I then tried it next to the headstock unsupported by the tailstock. Same issue. The 42" bed certainly didnt do that. Thinking maybe some chips got under the headstock I took the headstock back off and cleaned it again, looking for any burrs etc. Put it back together and still had the same issue. The large diameter is the cut away from the headstock, so its almost as if the headstock is aligned at an angle away from the front of the bed. Left it alone awhile as my mothers health issues (she is 92) took me away from my lathe, and then getting back home I had an urgent job on it, so I rebuilt it with the 42" bed again. That's where it stands now but I may have some spare time soon and want to get the 48" bed going. Any ideas? Thanks to all.
 
Hello all. First post. I've lurked here awhile and decided to join today having learned so much on this forum. I have a Southbend 10K light 10" lathe that has a 42" bed. Restoring antique firearms as a hobby, and also building large telescopes to help with my astronomy hobby, I find my lathe bed is often a bit short. The 48" bed would do wonders for me. Since I really like my lathe otherwise decided to simply get the longer bed and rebuild the lathe. Wound up with a nice 48" bed and a nice leadscrew for the gear box. Both the screw and the bed are actually nicer than the 42" ones I had been using. Great. Here we go. Switched out the bed, leveled it, rebuilt the lathe, switched out the leadscrew and tried her out. Problem #1. On the 42" bed, when I tighten the two bolts in the back of the saddle that hold the saddle retaining plate on, the saddle is a nice slide fit on the bed. With the 48" bed, I need to leave the bolts loose about an 1/8" or the saddle is firmly locked onto the bed! Kind of odd. Comments? Should I machine a spacer the exact thickness I need so I can tighten these bolts? Problem #2. Severe accuracy issues. Turning an aluminum or brass rod I find the diameters are out about 0.0015"/inch. I tested a 6" run at the headstock and also near the middle of the bed. In both cases the diameter was 0.009" to 0.010" out! I then tried it next to the headstock unsupported by the tailstock. Same issue. The 42" bed certainly didnt do that. Thinking maybe some chips got under the headstock I took the headstock back off and cleaned it again, looking for any burrs etc. Put it back together and still had the same issue. The large diameter is the cut away from the headstock, so its almost as if the headstock is aligned at an angle away from the front of the bed. Left it alone awhile as my mothers health issues (she is 92) took me away from my lathe, and then getting back home I had an urgent job on it, so I rebuilt it with the 42" bed again. That's where it stands now but I may have some spare time soon and want to get the 48" bed going. Any ideas? Thanks to all.
im not a lathe expert but know these lathe's were assembled by craftsman that hand fit them on assembly. It's not like today where you can order a part and install it and run. Hand scraping is an art. Your problem with the sadle is an example. You will probably have to shim to get clearance but it will change as you move it down the bed.,,,, Wear! ,,,,,,,Find a in between. ,,,,,,,Split the difference or regrind the bed."......"....."....."................................."...........................................................,',,,,,,,,,,, Here is a link to start with.,,,,, http://www.practicalmachinist.com/vb/south-bend-lathes/headstock-replace-align-made-easy-217897/ ,,,,,,,,,,,you need to choose words to google. ,,,,,,,Like , ,Lathe alignment. Lathe assembly.,,, Lathe leveling. ,,,,,',,,,,,,,You may be led to other threads on this forum. I use google. The search function on this forum p's me off.,,,,,,,,,,,,,,,',,,,,,,,,, Google will give you links back here often. ,,,,,,,,,,,,,,,,',,,,',,,,','''',,,,,,','Search utube for Video'. ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,',,,,,Your starting with a step by step fitting process. Not impossible but precise.jthe link I gave you may not be the best. An example only.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,',,,,,,,,,,,,,,,,,,,,,,,,',,,,,,,,,MAKING AND USING A TEST BAR FOR TESTING AND ALIGNING THE LATHE',,,,,,,,,,,my paragraphs all crammed together so I added spacing. Halfacc
 
I know you said you leveled the new bed. But, did you adjust the bed using the leveling screws at the tailstock end bed foot to get rid of twist in the bed after making a test cut. The bed can have twist that may need to be adjusted out.
 
Fundamentals

Thumbnail has a third paragraph. They are discussing a single lathe assembly made from parts dedicated to that single assembly. Beds are about the LEAST interchangeable thing I can think of on a lathe
 

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Pics always help showing how you are checking things.

Were you close enough I would say bring it over and lets scrape it in...I think I can still handle a 9" head,saddle,and tailstock...maybe.:)

Ps- I'm really serious about that, at this point I would welcome the challenge...and if I cant I can show you how...it's not that hard, just planning and patience, plus knowing how to check.
 
One thing you have to remember, even though there were thousands of these machines made, it will be unlikely that you get two beds machine exactly the same. You will need to know how to hand scraped one in. The first problem is the headstock. You would think that the headstock would be easy to replace. But just a few thousandths of an inch difference in the flat versus the Vway, Can make the headstock tilt. It can also throw the alignment off, Just like having a piece of trash underneath it. The next problem area is the saddle. It sets onto Vways, Which doubles the complexity of fitting the part. In this case the saddle may rock while cutting. This can give you an inconsistent cut. The cross slide also needs to be square with the bed. You don't want to be cutting a taper while making a face cut.. A third problem is the distance between the lead screw and the saddle. This is much less of a problem, But it is one that needs to be checked anyway. You may need to shim between the saddle and apron or between the leadscrew bearings and bed to bring the lead screw into alignment. Tailstock alignment is also an issue. The saddle, cross slide and tailstock, All have where issues to consider. You need to check each component and make sure they are properly set up. A problem with one component can cause problems with another component. For instance if the headstock is out of alignment it will make you think that the cross slide is out of alignment. And it can be difficult to determine which is the actual problem, without the proper equipment.

Stay safe and have fun.

Joe.
 
I have a hard time imagining the two beds are that far apart at the headstock mating surfaces. Even if they were off enough to cause the headstock to tilt forward or backward, the spindle axis still should be very close to parallel with the saddle travel vector.

I’m more inclined to think something else is going on, or the bottom of the headstock got bumped/burred during the switch.

I’d pull the headstock, blue up the mating surfaces, and make certain it’s not rocking on a burr.
 
Darn, OP is gone....thought I might get one more little project in...:)

Nope, still here! Lots of time away from home taking care of Mom. Thanks for all the input everybody. I am realizing now that buying a bed was perhaps not the smartest thing to do. I figured I may have a bug or two to work out, but I never figured I'd have to resort to rescraping. Yikes.......don't want that kind of time or hassle. There are no burrs under the headstock, its working fine back on the 42" bed. And there is no twist to the ways, that was checked when it was set up with the 4' bed. Ive actually been looking quite awhile for a nice 10K with a 4' bed on eBay or craigslist but they don't come up too often. More 10Ls out there....may consider going that route and selling my 10K, but again so many are beat and i really don't need another big project...got plenty of those already ahead of me! Also have been looking at the NEW 10L on Grizzly. That would avoid all hassle but of course the price is always an issue. Still...it sure looks nice.

Thanks for the links mllud22, Im checking them out now.
 








 
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