New lathe project

Yes, ugly is right! It's clear that the part is beyond repair. There's just not enough meat there to do anything with to make it functional. The slide itself is no more than a few lbs. I looked at slides on eBay last night to get an idea of what I might do. It appears that many slide assemblies have the dovetail on the base so I need to get a whole assembly with the base and fit the mounting hole to the cross slide. That should present the fewest challenges. The SB 10 appears to be an exception to the dovetail arrangement and the mounting hole on the base looks close to what I need.

Pete

 

Depending on how rare old machinery parts are in your neck of the woods and how well equipped your workshop is, you could machine a replacement slide from a solid block of continuous cast iron bar and ditch the lantern style tool holder before it digs in and breaks the compound again.

 

It's a shame you don't cast iron. This would make an interesting project if you did.

 

If you would, take some measurements of the dovetail, mount and other critical dimensions. My lathe came with an extra compound and if it'll fit yours I'll gladly mail it to you for postage.

 

Ill take measurements and weights when i get home. I really like the direction this thread is going!
Thanks for the offer dtsh. Thats an awfully nice gesture.

 

Yeah casting one would be fun!

Though I'm sure you could grind out the old weld and put in a proper one then mill to dimensions. Arc weldng it like they do when making anvils from bar stock could work.

 

The pics aren't entirely clear to me, but from what I see it looks relatively close to mine. I will say that compund travel on mine feels like it goes on forever, it's nice when cutting a taper.

Here's a pic of mine for comparison, kindly see fresh paint and a well maintained machine instead of what's really there.

 

Ill check the base for a witness mark. The brass degrees ring (help me with the nomenclature) is part of the of the cross slide so the base would have a mark on one end.
I notice that dtsh's base has the swivel hole right at the end whereas mine is closer to center, but i believe that the excessive overhang is just a weak point in the design. I suppose experience with the machine should tell you when and when not to over extend it, but Mark' castings' comments are not lost on me!
Pete

 

The first and third photos show the extremes of travel. I took the gib out of the compound slide so I could get that messy dovetail to move all the way to the end. The second pic shows the components apart. The swivel is part of the cross slide. I found the witness mark. It is a tiny pin punch mark and took some rubbing to find it, but it's there. So I'm confident that it had been assembled correctly.




The compound slide alone weighs a few ozs over 6lbs, and the base weighs just over 3 lbs.

The width of the dovetail on the compound slide is 2.180" at its maximum and 1.831 at its minimum (as best as I could get my calipers in there). I guess I forgot to measure the height of the dove tail. I'll get it in the morning. The swivel hole in the base is 1.750" diameter. I believe the t slot for the tool post is supposed to be 1.75".

Pete

 

I dug out the extra compound and discovered it's not for my lathe, no idea what it came off of. I hadn't ever given it much attention previously as the compound on my lathe worked fine and since it came with the lathe, I just assumed it went with it.

Here are some pics of it, the narrow section of the dovetail came out to 1.90 and looks to be a typical 60 degree dovetail. I'll check how the screw mounts tomorrow, guessing a typical acme or square thread nut, but considering I don't know where it came from it's only a guess. The mount to the cross-slide is not compatible with what you have unfortunately, but the top part of the compound may yet fit, though it will likely reduce travel. If you're still interested in it, measure your screw and thread pitch as best you can, may get lucky and it'll be a match making things much easier. I'll try to get some more accurate measurements of the rest of the dovetail.

I don't think the thing is modifiable to fit the mount on your lathe (which appears to be the same as mine), but I'll pull my compound off and do some comparing. For a drop-in which I thought I had, I'm sorry to say I was mistaken.

 

Well it was a nice thought anyway. It looks like your dovetail may be opposite of mine. I can't really make out the end profile from the pics.

Pete

 

I'm still undecided about the compound slide and may be using it as my first iron casting project. But in the meantime I needed to press on with the rest of the cleaning and inspection. Once I get through that I can get it out of the middle of the floor and into its final spot elsewhere in the middle of the floor.
I took the carriage/apron off as a unit. It was a bit dirty but no visible wear on the gears and was surprisingly oily. I had been unable to get the power feed clutch to tighten and discovered that both guide pins were sheared off. I drilled into the sheared pins as close to center as I could with an undersized drill and used a magical easy-out type gizmo to draw them out. It worked great. I redrilled the holes to fit 3/16 spring pins (I call them roll pins). I went a little oversized with the holes in the beveled insert because I assume the should slide. It turned out great.
The tailstock came apart, cleaned up, and went back together just fine.
Next was inspecting the back gears. Note from one of my previous photos that the handle is broken. I will use what's left of the stub and mount a handle to it. I could also try to recast that but disassembly of the eccentrics out of the castings could be tempting fate so I'll just modify what's there. Otherwise all the gears are in good shape.
Next up will be remounting the motor and countershaft. I may just move the machine to its permenant spot first.
I still haven't figured out why photos always appear at the top of the post and it's too much of a pain to move them on the iPad, so they're up top. They seem to get sorted in random order too!

Pete

 

Some of those pins are designed to shear off to protect gear teeth like a mechanical fuse and fitting hardened pins could cause damage during a feed crash. On the Colchester lathes I have the lead screw drive gear pins were mild steel and the service rep told me they had them made using a nail making machine that was set up so the ends were sheared square and not pointy.

 

Dang that never occurred to me. They obviously performed that function in the past.
I'm not shy about pulling it all apart and cutting them off. I could grind them flush and redrilled new hole as there is plenty of room on the part to do so, but I'm concerned about using the right pin. The originals were steel, but how hard/soft? They also act as sliders so too soft and they may wear out. A little too hard and they would fail to shear.
Note the 3rd photo in post #11. The gear above the leadscrew gear has had its spokes brazed at some point. There's no way of knowing exactly why or if it's even an original gear, but it makes me wonder if I should make a shear point further up the drivetrain.

Pete

 

As far as the type of steel goes, all I can go on, is my newer lathe is using a steel nail cut off as the shear pin. I think if you use plain old soft steel wire of the same diameter as the originals you should be fine. They do go into grey cast iron parts so they can't be at all hard. You could assemble the mating parts and drill and pin one new hole at 90 degrees to the originals and then drill and pin the second hole while the first pin prevents any movement so as to get perfect alignment. The crash that broke the compound probably sheared those pins at the same time.

Definitely ditch the lantern style tool holder as the geometry makes it dig in further during an accident and get some sort of multifix quick change tool holder.

 

I wouldn't worry about wear on soft steel pins. They really don't get much movement. Brass pins the same size as your roll pins would be quicker and still last admirably.