Solution to my 4-way TP Problem and a Question

[tmenyc]

I have a very nice update on my problem of having a 3/8" tool holder be 1/8" too high in my 4-way TP on my Logan 820. JFL4006 offered to mill the 1/8" off for me, and did! He was smarter than this newbie and said he'd take a bit more to ensure there'd be enough, and gave me a whole bunch of shims as well...so, at this point I'm really happy to report that the holder fits with .065" to spare, and I shimmed that, and now it's dead center.
Thanks again John, I'm deeply appreciative. This is a great board...

Yes, I know it's a roughish cut. I'm having a spot of trouble getting the power feed going. I have not been able to find a detailed description of how to do it, what the correct combination of clutch, feed reverse lever, power feed lever needs to be and how each works. I've seen a bunch of videos and read the original manual, but either I"m being thick or none of them tell me the sequence of switches I need to make to go from manual to powered. Help please? Does such a video exist and I'm just missing it?

Many thanks, best for Christmas,

Tim

 

[tmenyc]

Update: I seem to have found the right combination, now it's running a lot quieter and the cut is smoother. The rings are now completely even, but it's not shiny yet. I was using the CCMT insert, read about the differences between CCMT and CCGT, and switched to CCGT since I'm cutting aluminum. So it's better but not right yet. Is the lathe running too slowly? It's on its lowest gear, I believe (learning the gears is my next step, although I have a lot of years of road bikes behind me so am not uncomfortable dealing with gear relationships.) But where can I find the correct speed to use? I feel like I'm getting the pieces of this one at a time, and perhaps that's a good thing.
Tim

 

[Cadillac STS]

One suggestion for shims is to use a set of feeler gauges. The kind that can be taken apart so you end up having several choices of width to get it shimmed right and they fit under your tool. Stack up what you need and add or subtract as needed.

 

[Cadillac]

Update: I seem to have found the right combination, now it's running a lot quieter and the cut is smoother. The rings are now completely even, but it's not shiny yet. I was using the CCMT insert, read about the differences between CCMT and CCGT, and switched to CCGT since I'm cutting aluminum. So it's better but not right yet. Is the lathe running too slowly? It's on its lowest gear, I believe (learning the gears is my next step, although I have a lot of years of road bikes behind me so am not uncomfortable dealing with gear relationships.) But where can I find the correct speed to use? I feel like I'm getting the pieces of this one at a time, and perhaps that's a good thing.
Tim

Looks like you want to slow your carriage down. More radius on the tool will help with the lines also. Start slow on carriage traverse and then speed up to improve your chip.

 

[mikey]

Tim, go here and download the charts: https://littlemachineshop.com/reference/cuttingspeeds.php

Note that there are different charts for turning, milling and drilling so get them all, print them and put them in a folder.

To calculate the speed your lathe should turn, you need to know the material you're cutting, the type of tool in use (HSS or Carbide) and the diameter of the work piece. Then look up the cutting speed for that material under the column for the tool type you're using. For example, the cutting speed for aluminum is 2820 sfm, or surface feet per minute. You then need to plug that value for SFM into this formula to get your RPM: RPM = cutting speed in SFM X 3.82 / Diameter of the work. Again, the SFM comes from the chart, 3.82 is a constant and D is the diameter of the work when turning or the diameter of the tool when milling. So, for an aluminum work piece of 3/4" OD being turned with a carbide insert, you have RPM = 2820 X 3.82 / 0.75 = 14,363 rpm. If you were using HSS, the RPM would be 550 X 3.82 / 0.75 = 2800 rpm.

For soft materials, the cutting speed with carbide and resultant rpm will often be well above what your lathe can run at. Just use the fastest speed you have available. You can now see why HSS is preferred for these older, slower lathes; you just cannot get the speed you need for the insert to work optimally. BUT it will still work.

As for feeds, you will need to play with the gears you have or feed manually. If you feed manually, feed so that you can feel a slight resistance to the feed as you turn the handwheel. If you need a finer finish, slow down.

If you encounter chatter, you can reduce depth of cut, slow the speed or increase the feed.

Play with this and you'll eventually sort out how to make it all work.

 

[tmenyc]

Mikey,
thanks, this is EXACTLY what I knew had to be out there but hadn't found. And yes, I am using carbide now only because I wanted to get started while, on a parallel, path, I grind HSS tools.

Tim

 

[Winegrower]

Is it possible you’re using the half nut for carriage feed and have a high thread per inch setting? The Logan feed rate can be as low as around a thousandth of an inch per revolution.

 

[tmenyc]

I don't think so...I've been learning step-by-step, and haven't touched the gears yet. Basically, I cleaned everything I could get to while it was still disassembled, an expert assembled it, and now I'm learning. The picture shows the current setting, which does look like higher thread/inch setting. Should I move it all the way left? I now know that a big part of not getting a clean cut is that I'm running too slow for aluminum.
thanks!
Tim

 

[tmenyc]

I moved the belts to a higher speed and switched to steel. Works fine. Thanks for the help!
Tim

 

[mikey]

Much better. Be sure the tip of your tool is dead on center height.