Saving a Logan 825

[wa5cab]

I have four comments, other than that the ball bearings look good, but....

I am not familiar with this machine but if it has a multi-step conical pulley on the spindle and a pin of some sort that locks that pulley to the bull gear for direct drive and the pin is pulled out and the back gears engaged for back gear, the the lubrication note should be to also lubricate the pulley bushings every time that you lubricate the back gear bearings or bushings. The second is that the lubrication frequency should be monthly PLUS whenever the back gears are used, not just whenever the back gears are used.

The third is that whenever you switch from bushings to ball bearings on the Tumbler, the bolts or pins must lock the inner races of the ball bearings to the tumbler. Else Murphy's Law generally guarantees that the bearing inner race will tend to spin on the bolt/pin instead of the outer race spinning on the inner race. And prematurely wear out both bearings and bolts/pins. One way to fix it is to insert an inner race shim under the head that is thick enough to lock up the bolt/pin and inner race.

The fourth is that the photo above shows what appears to be a compound gear, one of which is presumably the 60T gear that you mentioned. You cannot simply replace the keyed bushing with two ball bearings because what you will end up with are two independent idlers. If the input is to the larger gear and the output from the smaller gear, the lead screw will not turn under load. There are several ways to fix this including installing new but otherwise original parts.

 

[bhusted]

I have four comments, other than that the ball bearings look good, but....

I am not familiar with this machine but if it has a multi-step conical pulley on the spindle and a pin of some sort that locks that pulley to the bull gear for direct drive and the pin is pulled out and the back gears engaged for back gear, the the lubrication note should be to also lubricate the pulley bushings every time that you lubricate the back gear bearings or bushings. The second is that the lubrication frequency should be monthly PLUS whenever the back gears are used, not just whenever the back gears are used.

The third is that whenever you switch from bushings to ball bearings on the Tumbler, the bolts or pins must lock the inner races of the ball bearings to the tumbler. Else Murphy's Law generally guarantees that the bearing inner race will tend to spin on the bolt/pin instead of the outer race spinning on the inner race. And prematurely wear out both bearings and bolts/pins. One way to fix it is to insert an inner race shim under the head that is thick enough to lock up the bolt/pin and inner race.

The fourth is that the photo above shows what appears to be a compound gear, one of which is presumably the 60T gear that you mentioned. You cannot simply replace the keyed bushing with two ball bearings because what you will end up with are two independent idlers. If the input is to the larger gear and the output from the smaller gear, the lead screw will not turn under load. There are several ways to fix this including installing new but otherwise original parts.

I appreciate your thoughts. On the backgears, there was no provision for lubricating the backgear shaft originally from Logan, so The fact that there will be a oil port there means that they will get oiled much more frequently than never. I am well aware of the lubrication schedule on the other points on the machine and tend to check/oil every point each time I use it. I'm still in the setup/testing phase of getting this Logan up and running, so it doesn't get used much yet.

For the bearings I used, you can see that there is a step in the back of the gear. This is because the gear is wider than the bearing. The idler shafts were pretty beaten up from previous use and all of the slop in the bushings. I sized the ID of the bearing to fit the tumbler shaft and then machined a .145" long spacer to take up the extra width of the gear + .01" so that when tightened, the spacer traps the inner race on the tumbler shaft. The result is the idler gears being smooth and quiet.

While the gear may look like a compound gear, the 48T gear on the outside is just in "storage" and doesn't actually touch anything. I think Logan did it this way so that if you wanted the top row of course pitch thread or extreme feeds, you could swap the 48T gear in place of the 24T stud gear. The 60T gear in the back is what drives the QCGB from the spindle. I didn't want to modify these, so I found another 60T gear 16DP 14.5 degree pressure angle on eBay for cheap and will bore that to fit some more ball bearings. For less than $30 I'll have smooth running gears. The replacement bushing from Logan is $95 alone.

 

[wa5cab]

OK.

 

[bhusted]

Just to be clear about the spacer I made for the bearings that goes on the back side of the assembly. Here is a picture of the setup taken apart.

 

[wa5cab]

OK.

 

[bhusted]

Another update on this Logan project. I picked up a cheap spur gear from ebay matching the specs (16 DP and 14.5 deg pressure angle) of the 60 tooth gear that links the stud gear to the input of the QCGB. Originally this gear was setup for a 3/4" keyed shaft, but I just bored both sides to press in 1/2" ID 1-1/8" OD ball bearings. There is a sleeve to take up the space between the two inner races and a new shaft for them to fit onto. I could have re-used the original t-nut, but I made the shaft for a 3/8 bolt and the Logan part is for a 5/16 bolt.

The new setup is much quieter and smoother as the original threaded, keyed bearing was badly worn. One less place to have to worry about oiling and the sealed bearing should outlast the rest of the machine. Here it is installed.

Still plenty of fixes and improvements to make on the machine, but it feels like good progress. Another part that I've been working on now that I have it setup for testing is the motor. I love being able to adjust speed with the DC motor and not have to change belts, but I've decided that I want to add a jackshaft to decrease the max spindle speed and increase power. Those parts will hopefully be arriving soon and I can do some more testing.

Another part that I've been thinking about what to do is for the tailstock. While it is functional, there is a fair bit of wear and pitting from rust on the tailstock ram. The morse taper socket in the ram is also badly worn. I cleaned it up with a tapered reamer and it does hold tools, but it is not pretty. Most of the wear/pitting is on the tool end of the ram and measures anywhere between -.003 and -.005. At the screw end of the ram, it is nearly perfectly on size at <-.001. The bore of the tailstock also has some wear in it, again concentrated at the tool end of the bore as much as +.003. I can only reach in so far with telescoping gauges, but the wear in the bore seems to be concentrated to the first 2" of the bore.

I've been hunting for a better condition ram in the usual places, but have not come across any. Of course I could buy a new one from Logan for $270, but I'm looking at my prospects of making one. Has anyone else done something like this before? I've been reading threads on PM and other places about making a tailstock ram. Since the size is a common 1-1/8", I was thinking of getting a 6" section of ground shafting with the keyway already cut in it as a starting point. Just this would cut the clearance in the bore by more than half. I'd love to hear more from anyone that has done this before.

 

[bhusted]

Sorry for the lack of updates here. I disassembled the headstock again yesterday to install the repaired back gears. The oilite bushings the backgears ran on were heavily worn and the bores in the shaft were also oversized, so someone had been in there before. I cleaned up the bores, pressed in new bushings and installed a ball oiler about 2/3 of the way down the shaft so that I can add oil to the space between the bushings at either end. It's a long way down there but the neck on my oil can is long enough that I can reach. Getting the timing of the plunger right is a real pain, but I managed to get that all back together and working.

I haven't done any cuts with it, but I'm happy with how it runs. As loud as I expected with open, straight cut spur gears. A little bit of sticky grease on the gear teeth quieted it down a little bit. The brazed on tooth seems to work fine. The spring loaded lock on the plunger needs to be reworked. It holds the gears engaged, but needs to be longer as it runs noticeably better if I hold the plunger out a little more when running.

 

[Shiseiji]

Thanks for your thoughts. Always appreciated. I've been reading about lots of people removing the compound to increase rigidity on these smaller lathes. I took a break from online meetings and pulled the compound to make some measurements.

The first thing I noticed/remembered is what a pain it is to pull the compound off. With the t-bolts captive and the nuts in the slots on the compound, there is a dance of loosening the nuts back and forth to be able to lift the compound free. By contrast, the compound on my Atlas/Craftsman is removed by simply loosening the 2 bolts and lifting it off of the dovetail plug. I think South Bend did theirs this way too. I guess my thinking here is that if I take the compound off, I'm not putting it back on unless there is a really good reason.

The flange on the bottom of the compound that mounts to the cross slide is 5/16 thick, so removing material here seems like a no go. This would all but eliminate the degree markings on the flange of the compound. My compound is 2.135" tall, so I'd need a replacement that is about 2" tall. What material did you use for your plinth? Are all of the Logan compounds the same style mounting? Is there any variation on the height of the compound between models?

FYI: Logan switched to a pintle at S/N 50843 mid 1952. 1953 is when the 800 series changed to vee belts. I've had both and much prefer the pintle. The serial numbers are posted at Lathe.com but you need a parts manual for the compound information. The pre S/N 50843 parts drawings are side view engineering drawings.

 

[wa5cab]

It appears that all of the US makers of 9" to 12" lathes (Atlas [& Sears], Clausing, Logan [& Wards] and South Bend) started off with the captive bolt and nut style compound swivel and changed to the inverted cone or Pintle style in the mid 1930's. Some made the change coincident with a model number change and some just recorded the serial number.

 

[bhusted]

Time for an update. I have not had a lot of time to work in the shop, but have made some progress on saving this Logan. When I recieved the lathe, the tailstock ram was in very poor condition. It was pitted from rust worn, and the tapered socket was scared. A careful inspection of the parts showed that the majority of the wear was in the ram and that the bore of the casting was still round and true to size.

No suitable replacements were found on ebay and the new part from Logan was $$$. I came across a thread on Practical Machinist where a gentleman had extended reach of his tailstock by making a new screw and rear cap for the tailstock. I figured if I was going to make a new ram, I might as well make some other improvements at the same time. No permanent alterations of the tailstock were made in case it didn't work.

The replacement ram was made from 1-1/8 cylindrially ground drill rod. While probably not the best material for the part, it gave me a starting point where I knew the OD would be a very good fit for the bore of the casting. Indeed the sliding fit of the new "ram" was excellent after a thoughough cleaning of the bore. The keyway was done with the milling attachment on my Atlas/Craftsman and the MT2 socket was roughed out on the Logan and finished with a hand reamer.

The step in aft end of the ram is to make room for the new cap that screws into the end of the tailstock where the handwheel is. I was originally intending to make the new screw, but sourcing a 7/16-10 LH acme tap for the ram was too much. Instead I ordered a length of 1/2-10 LH acme rod that came with 2 brass nuts. I counterbored the end of the ram and pressed the brass nut in place.

The rear cap needed to be redesigned to accommodate the added length of the ram, so I also decided to add thrust bearings, an oilite bushing and a dial to the assembly.

This is with the ram fully extended. I have almost 3.5" of travel now, so all of this gained a little over an inch of travel for the ram. While I don't do a lot of deep drilling, I find it annoying to reposition the tailstock to drill deeper than 2".

Here is the full assembly. I'm not sure that I love the look of the rear cap, but I'll use it and see how I like it. I need clean up the jam nuts and cut the woodruff key slot (tool is on order) in the end of the screw. The dial is reposition able for drilling to depth and made just like the other dials for the cross slide and compound. Someday I'll work on stamping the numbers on all of these... I don't know if I will try my hand at scribing the lines for a scale on the ram itself.