Saving a Logan 825

[HarryJM]

I do not have the dimensions although the thickness seems to be the only significant dimension as the length and cut out have plenty of room for movement. You could always do a wood prototype that would be easier to play with until you nailed the dimensions.

 

[bhusted]

I do not have the dimensions although the thickness seems to be the only significant dimension as the length and cut out have plenty of room for movement. You could always do a wood prototype that would be easier to play with until you nailed the dimensions.

I had considered a prototype from wood and I may still do that. I think the thickness is pretty arbitrary because the headstock doesn't clamp to the bed in a fixed location, the distance from the banjo to the headstock is a moving target. The pin must simply be long enough to engage the banjo. From the pictures I've looked at, I think the thickness is about 1/2".

The reason I'd like to know the slot length and position relative to the pin is because the slot needs to be long enough to accommodate larger transposing gears and get close enough to the pin that smaller gears can still mesh. I'm assuming that some engineer at Logan worked out the limits of what is necessary for these dimensions without making it too long or too weak. I could probably work this out after everything is assembled but with my limited time to work on the lathe at the moment, I thought I'd see if I could get dimensions from anyone.

 

[bhusted]

Time for an update. I haven't had a lot of time to work on the Logan, but have taken an hour here and there over the last few days to get started on the cross slide dial parts. I did something similar to my Craftsman/Atlas lathe and been very happy with the result. For the most part I just made small modifications to the design to fit the Logan. You can see the thread on the previous dial upgrade here. This time around I'm making the dial 2.5" in diameter to give some more space between the marks. The counterbore is for a thrust bearing that will take up the axial load on the leadscrew.

 

[bhusted]

A while back I mentioned that one of the back gears was missing a tooth. I decided to attempt the repair and am happy with the results. Only time will tell if the repair holds up. The first step was to clean and grind away the root of the old tooth and then fill the resulting cavity with brazing rod.

Next I turned the gear round again and trued up both faces. This was very tricky to indicate.

To cut the new teeth, I ground a HSS tool blank that matched the tooth profile as best I could. Then I setup the tool and locked the spindle. The cutting takes place by advancing the tool a few thousandths and moving the carriage across. Repeat the process a bunch of times and you're left with a new tooth.

 

[AmericanMachinist]

Great idea on how to cut the tooth without a mill and tooth cutter. Thanks!

 

[bhusted]

Great idea on how to cut the tooth without a mill and tooth cutter. Thanks!

Thanks. It worked out well in this instance. I don't think this method would be suitable for cutting more than one or two teeth. I haven't installed the back gears yet, but rolling it over the mating gear seems smooth and no issues from the new tooth.

Thanks to Nogoingback for the drawings he made of the carriage lock. I had a couple of hours tonight to make a new nut. Certainly not a show piece, but it looks the part and fits. I won't know if it works or not until I get the saddle/apron assembled and on the bed.

 

[AmericanMachinist]

What would your main concern be cutting multiples?
Getting several adjacent teeth all spaced properly, or doing this process several tomes over?

I have several gears all waiting on 1 tooth each to be repaired, this is a process i could go ahead and attempt with the equipment i have available.

 

[bhusted]

My concern would be just the amount of time required. The process works fine once everything is setup. I was able to index the teeth with consistency. Since this is a form tool the engagement increases drastically as you get deeper. I started out with a .005 cut, but when I got to the bottom, I was really only cutting .001-.002 at a time. I forget what the total infeed amount was, but it was more than .100.

 

[bhusted]

Some of my springs came in, so I was able to assemble the feed clutch and button up the apron. The springs I ordered are metric, but they are the closest I could easily find that were pretty inexpensive on ebay. The specs I used are 3mm OD x 10mm length with a wire diameter of 0.5mm. They are just a bit long, so I cut them down to 8mm and it works perfectly. I think they are a bit too heavy of a spring rate for the back gear latch, so I have some others on their way that have a wire diameter of 0.25mm. Here is a picture comparison to what I think is one of the original springs before I cut it down. The new spring is on the left.

I also did some more work on the cross slide. I pressed in the new oilite bearings and then installed the thrust bearings. This was a little bit tricky because I had to slide them on the screw at the same time as the feed gear. Extra care had to be taken in the design of the new holder to maintain the position of the feed gear. You can see them between the gear and the holder here.

There is another set of thrust bearings on the crank side. They fit into the counterbore and ride against a bushing that will carry the dial. I have not made the dial yet. The end play is taken up by threading the bushing against the thrust bearings and then locked in place with a jam nut.

This last part may be a bit controversial. I drilled and tapped the end of the screw for a 4-40 screw to hold on the handwheel. Because the dial will be much larger, I will lose a small amount of travel in the cross slide because the casting will run into the dial. To get some of this travel back, I opted to move the dial and flange outward on the screw. There would not be enough of the threaded portion remaining for a nut to retain the handwheel, so a screw from the end was the solution. With the keyway in the shaft, couldn't go any larger on the size. I also made a nice stainless washer to finish it off.

 

[bhusted]

Sorry for the delay in this project. In between some other projects/maintenance on my other lathe, baby duty and getting ready for my work to start again, I haven't had a lot of time to work on the Logan. Some progress has been made. I've been putting off working on the bed and just decided to switch gears and put things together as is to see what else I'm missing. I need to build a stand/bench for this machine so it will all have to come back apart and I will deal with the cleaning/painting the bed then. To see if the DC motor was going to be up to the task of running the machine, I made a test stand from a 2x10. This is just temporary before anyone gets worried that I'm not building a rigid base and leveling the lathe. That will come later.

So far everything works. The spindle is quiet and the motor seems to have plenty of power. I stole the toolpost from my other lathe to do some test cuts to put a load on the motor. I chucked up a piece of 1018 and made progressively deeper cuts. I got all the way to .100 DOC with no bogging down and no chatter so I was pretty happy.

I've realized that I'm missing the knob that holds the cover closed on the headstock, so I'll be prowling the web for that. You can see my stand in for the knob. My large dial conversion is almost finished. I need to scribe the lines and stamp the numbers on the dials. The other missing parts are a wrench for the tailstock and an oiler for the tailstock. Eventually I'll make a proper square bolt for the carriage lock, but the nut that I made from the drawing provided by Nogoingback works well. I'm also working on the electrical side to control direction and speed of the motor.