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Sherline Tailstock Misaligment
- Thread starter tomw
- Start date
- Joined
- Oct 21, 2014
- Messages
- 2,162
I told you And wait a min, Is your also a 4400, because mine was ether Dec or Jan, And I had some problems with QC on it as well. Like they did not get the plastic finished properly and sharp edged on the chuck to the point I got cut by it. But like I said they are trying to work when things are found. As soon as I get the piece off of mine i'm working on, I will recheck it. As like I said I very rarely use the tail stock, Most of mine has been small short stuff or stuff that did not matter if tapered or something. But now I am starting to do some things that matter more so I better get it checked.
- Joined
- Dec 20, 2012
- Messages
- 9,422
Too bad we lost Joe Martin. I hope Sherline can pull it together because they introduce a lot of folks to machining. The older machines didn't seem to have these QC issues. In fact, the lathes had much tighter tolerances than Sherline published.
I too had a slight alignment issue. I first read all the documents regarding initial setup and alignment, but disregarded the suggestion of using a mallet on the headstock to "bump it over".
The reason I chose to disregard the mallet method was because the gib in the headstock fit very tightly and no amount of "bumping it over" would succeed. Since there was no physical way to move the headstock and reduce the angle of the headstock with the gib in place, I decided to make some room for this allowance. On only 1/2 the length of the gib, I gently used my 1" belt sander and removed microns of material from one of the horizontal sides of the gib. Note the 1/2 length mentioned earlier, next I reinserted the gib only 1/2 the way into its slot and then tightened down the headstock assembly. The taper on the lathe went from a positive taper (.002) over 2 inches to a negative taper (-.002) over 2 inches. Therefore I proved I moved the headstock and a negative angle was achieved. I was able to further adjust the headstock (without using a mallet) and achieved a respectable .0003 - .0005 taper over 2 inches. When such perfection is not required, I can just slide the gib back fully into its slot and the get the predictable .002 taper. BYW, most larger lathes have compound tapered gibs.
The reason I chose to disregard the mallet method was because the gib in the headstock fit very tightly and no amount of "bumping it over" would succeed. Since there was no physical way to move the headstock and reduce the angle of the headstock with the gib in place, I decided to make some room for this allowance. On only 1/2 the length of the gib, I gently used my 1" belt sander and removed microns of material from one of the horizontal sides of the gib. Note the 1/2 length mentioned earlier, next I reinserted the gib only 1/2 the way into its slot and then tightened down the headstock assembly. The taper on the lathe went from a positive taper (.002) over 2 inches to a negative taper (-.002) over 2 inches. Therefore I proved I moved the headstock and a negative angle was achieved. I was able to further adjust the headstock (without using a mallet) and achieved a respectable .0003 - .0005 taper over 2 inches. When such perfection is not required, I can just slide the gib back fully into its slot and the get the predictable .002 taper. BYW, most larger lathes have compound tapered gibs.
I have a 4400 lathe that I bought in 2008 and it had the same misalignment problem as shown in the image in the first post. Being as I was used to working to tolerances as close as +/- .0002 as a tool and die maker, this was totally unacceptable. I thought about modifying the tail stock by using the method shown on YouTube by a guy from Brazil named Luiz Ally. He has a five part series on how to deal with the tail stock problem. I ended up with a tail stock that can be dialed in with a lot of fussing around, but the effort was worth it. Basically, I had my tail stock split in two on a wire EDM machine so I was able to use a combination of clamping screws and shims to get it right. What I did is probably not the best answer to this problem, but it worked for me. Here are some images that I hope will make this a little clearer. The first one shows a pattern of six holes drilled through the tail stock. They are #21 all the way through at this point to allow for tapping 10-32 and clearance drilling as needed. Disregard the two odd holes, as they were not needed when this was all sorted out. These six holes were drilled through at this time to ensure alignment when the two halves of the tail stock were mated up again.
This next image shows the results of the wire EDM process. Finish the clearance drilling and tapping of the 10-32 holes at this point. I had to have the clamp screws enter from opposite sides, as I didn't allow enough room between the top and bottom rows for the screw heads to clear each other. So much for all that tool and die work. Missed something very basic.
When the two halves are ready to be mated again, an alignment rod must be prepared. Start with a 3-1/2" length of 5/8" or 3/4" diameter aluminum rod and make a skin cut 2-1/2" long. Check for any taper in the cut and adjust the head stock as needed. This method is recommended by Sherline to align the head stock. If using 5/8" diameter rod, be sure to take very light cuts, as the final diameter needed is .6188 to match the diameter of the tail stock ram. When the rod is the correct diameter with no taper, the two halves of the tail stock can be set up for the mating and aligning to begin.
Next, you can see the two halves mated up and the clamping screws installed. Now for the fun part. Working with feeler gauges, you need to determine how much shim stock to insert into the gap left from the EDM process and adjust the relative positions of the two halves so the assembly will easily slide on and off the alignment rod. Be sure to have the tail stock gib snug, but not tight on the bed ways. You need to be able move the tail stock along the bed ways, but you also want to minimize any twisting motion. When mine was all done, I ended up with .002 more shim at the dial end of the tail stock than the chuck end. That doesn't seem like much, but when you think about how far out a drill chuck extends and an inch or two more for the drill, that taper over two inches becomes quite a bit more at the point of a drill when you need a hole centered on a work piece.
If you choose to watch the YouTube videos by Luiz Ally, you can see that his method is easier to accomplish than this one when the final alignment is being done. But, I've always done things the more difficult way. A real problem of mine.
Here is a copy of the web address of the video.
Sorry, but I don't know how to make the address clickable. You will need to copy and paste to get to the first of five and go from there.
Well all right then. A moderator or someone who knows how to install a hot link to the video has taken care this. Thanks.
This next image shows the results of the wire EDM process. Finish the clearance drilling and tapping of the 10-32 holes at this point. I had to have the clamp screws enter from opposite sides, as I didn't allow enough room between the top and bottom rows for the screw heads to clear each other. So much for all that tool and die work. Missed something very basic.
When the two halves are ready to be mated again, an alignment rod must be prepared. Start with a 3-1/2" length of 5/8" or 3/4" diameter aluminum rod and make a skin cut 2-1/2" long. Check for any taper in the cut and adjust the head stock as needed. This method is recommended by Sherline to align the head stock. If using 5/8" diameter rod, be sure to take very light cuts, as the final diameter needed is .6188 to match the diameter of the tail stock ram. When the rod is the correct diameter with no taper, the two halves of the tail stock can be set up for the mating and aligning to begin.
Next, you can see the two halves mated up and the clamping screws installed. Now for the fun part. Working with feeler gauges, you need to determine how much shim stock to insert into the gap left from the EDM process and adjust the relative positions of the two halves so the assembly will easily slide on and off the alignment rod. Be sure to have the tail stock gib snug, but not tight on the bed ways. You need to be able move the tail stock along the bed ways, but you also want to minimize any twisting motion. When mine was all done, I ended up with .002 more shim at the dial end of the tail stock than the chuck end. That doesn't seem like much, but when you think about how far out a drill chuck extends and an inch or two more for the drill, that taper over two inches becomes quite a bit more at the point of a drill when you need a hole centered on a work piece.
If you choose to watch the YouTube videos by Luiz Ally, you can see that his method is easier to accomplish than this one when the final alignment is being done. But, I've always done things the more difficult way. A real problem of mine.
Here is a copy of the web address of the video.
Well all right then. A moderator or someone who knows how to install a hot link to the video has taken care this. Thanks.
Last edited:
- Joined
- Jan 28, 2020
- Messages
- 197
I purchased a Sherline 4400 lathe in January 2020. I found that the tailstock was misaligned more than the specification, which is <3 thousandths of an inch. I estimated that the misalignment was 7 thousandths, from the photo. I emailed Sherline about the problem; they told me to send the lathe back -- which I did.
I received an email message from Karl Rohlin, the shop foreman. He wrote that they replaced the tailstock; the misalignment with the new tailstock was 2 thousands. He wrote that they use a lathe mandrel and check between dead centers, with the measurements taken four inches apart. He included two photos showing the measurements.
Karl Rohlin did not state what was wrong with the original tailstock. When I received the lathe back, I saw that the new tailstock included two screws for making the gib friction even at both ends. The original tailstock did not have the two screws; it had unthreaded holes. Ironically, the lack of adjustment screws made repositioning the original tailstock over the other side of the cross slide, to photograph the misalignment, easier to do.
Karl
I received an email message from Karl Rohlin, the shop foreman. He wrote that they replaced the tailstock; the misalignment with the new tailstock was 2 thousands. He wrote that they use a lathe mandrel and check between dead centers, with the measurements taken four inches apart. He included two photos showing the measurements.
Karl Rohlin did not state what was wrong with the original tailstock. When I received the lathe back, I saw that the new tailstock included two screws for making the gib friction even at both ends. The original tailstock did not have the two screws; it had unthreaded holes. Ironically, the lack of adjustment screws made repositioning the original tailstock over the other side of the cross slide, to photograph the misalignment, easier to do.
Karl
Last edited:
- Joined
- Jan 28, 2020
- Messages
- 197
Here are the two photos that Karl Rohlin from Sherline included in an email message to me, showing that the misalignment between the headstock and new tailstock was 2 thousandths inch: zero at the headstock, and 0.002" at the tailstock 4.0" away. I appreciate the documentation.
- Joined
- Dec 20, 2012
- Messages
- 9,422
So what do you get when you put the live center in place? Most of us will almost never use a dead center, nor will we use a center up close to the spindle. What you really need to do is make a test bar and test the tailstock alignment with the tailstock about a foot away from the spindle where it sees the most use.
To make a test bar, find a piece of 3/8" drill rod about a foot long. Use your 4 jaw chuck and zero the rod up near one end. Face the end and drill an accuate 60 degree hole in it with a new sharp #1 center drill. Flip the rod over and repeat on the other end. Now mount this rod between dead centers and use your lathe dog to drive it. Machine a short section, maybe 1/2" long on the end closest to the chuck. I suggest you use a sharp HSS lathe tool and take a 0.010" deep roughing cut, then a 0.003" deep sizing cut, then a 0.001-0.002" finish cut and strive for a clean finish. Once you do this, you have a test bar that will serve you for many years so take care of it.
To use it, remove the lathe dog and mount the test bar between dead centers. Be sure the tailstock is lightly locked down and also lightly lock down the tailstock ram; this is how the tailstock will be configured in use so test it this way. Mount a dial indicator in your tool post and get the tip on center. Now bring the indicator tip into contact with the turned section of your test bar and preload the indicator about 0.015" and zero the dial. Then loosen the tailstock locking screw and flip the test bar so the turned end is now on the tailstock end. Do not touch the dial indicator or the cross slide hand wheel. Use the X-axis handwheel to crank the saddle toward the tailstock until you can position the dial indicator on that turned section. You will need to lift the tip of the indicator away from the rod as you traverse all the way down to the end, then gently bring it back into contact with the test bar. The reading you see on the tailstock end is the amount of offset that exists in your tailstock. Repeat this with the live center in place and that will tell you how much offset there is with the live center in place, which is the information you really need to know.
Essentially, Karl used the same procedure except they used an unturned rod, which is not nearly as accurate as making one as outlined above. You can also test for vertical offset, although there isn't much you can do about it if it is there.
You will find that your readings will vary with how tight you lock down the tailstock to the ways and how tight you lock down the ram. Try to be consistent in how much torque you apply; it doesn't take a lot.
You will also find that the two gib adjusting screws can be a little finicky to adjust but it is well worth the time it takes to get them right. You want to adjust them so the tailstock slides with little effort but there is zero play when you lift the front or rear of the tailstock by hand. The screw in the center, between these gib adjusters, is only meant to lock the tailstock in position. The better you adjust the gib screws, the less force it takes to lock the tailstock to the ways.
Oh, and just so you know, 0.002" is a LOT of offset. I know this is within Sherlines standards but on long work pieces, this much offset will result in unavoidable tapers. This is why I made a live center myself; to get around this issue. That brings me to my point. You may be able to index the OEM live center so that it minimizes or hopefully eliminates the offset. This is where the true value of that test bar comes in. If you can rotate the live center and find a position where the live center has minimal run out, make index/witness marks on the live center and the tailstock ram so you can align it that way every time you use the live center. This will minimize any tapers that occur and it is my sincere hope that you can find such a position.
Hope this helps.
To make a test bar, find a piece of 3/8" drill rod about a foot long. Use your 4 jaw chuck and zero the rod up near one end. Face the end and drill an accuate 60 degree hole in it with a new sharp #1 center drill. Flip the rod over and repeat on the other end. Now mount this rod between dead centers and use your lathe dog to drive it. Machine a short section, maybe 1/2" long on the end closest to the chuck. I suggest you use a sharp HSS lathe tool and take a 0.010" deep roughing cut, then a 0.003" deep sizing cut, then a 0.001-0.002" finish cut and strive for a clean finish. Once you do this, you have a test bar that will serve you for many years so take care of it.
To use it, remove the lathe dog and mount the test bar between dead centers. Be sure the tailstock is lightly locked down and also lightly lock down the tailstock ram; this is how the tailstock will be configured in use so test it this way. Mount a dial indicator in your tool post and get the tip on center. Now bring the indicator tip into contact with the turned section of your test bar and preload the indicator about 0.015" and zero the dial. Then loosen the tailstock locking screw and flip the test bar so the turned end is now on the tailstock end. Do not touch the dial indicator or the cross slide hand wheel. Use the X-axis handwheel to crank the saddle toward the tailstock until you can position the dial indicator on that turned section. You will need to lift the tip of the indicator away from the rod as you traverse all the way down to the end, then gently bring it back into contact with the test bar. The reading you see on the tailstock end is the amount of offset that exists in your tailstock. Repeat this with the live center in place and that will tell you how much offset there is with the live center in place, which is the information you really need to know.
Essentially, Karl used the same procedure except they used an unturned rod, which is not nearly as accurate as making one as outlined above. You can also test for vertical offset, although there isn't much you can do about it if it is there.
You will find that your readings will vary with how tight you lock down the tailstock to the ways and how tight you lock down the ram. Try to be consistent in how much torque you apply; it doesn't take a lot.
You will also find that the two gib adjusting screws can be a little finicky to adjust but it is well worth the time it takes to get them right. You want to adjust them so the tailstock slides with little effort but there is zero play when you lift the front or rear of the tailstock by hand. The screw in the center, between these gib adjusters, is only meant to lock the tailstock in position. The better you adjust the gib screws, the less force it takes to lock the tailstock to the ways.
Oh, and just so you know, 0.002" is a LOT of offset. I know this is within Sherlines standards but on long work pieces, this much offset will result in unavoidable tapers. This is why I made a live center myself; to get around this issue. That brings me to my point. You may be able to index the OEM live center so that it minimizes or hopefully eliminates the offset. This is where the true value of that test bar comes in. If you can rotate the live center and find a position where the live center has minimal run out, make index/witness marks on the live center and the tailstock ram so you can align it that way every time you use the live center. This will minimize any tapers that occur and it is my sincere hope that you can find such a position.
Hope this helps.
- Joined
- Jan 28, 2020
- Messages
- 197
Mikey,
You post definitely helps. I have wondered how to make and use a test bar. I have wondered to what goal to adjust the gib adjustment screws.
I have two questions in regard to your instructions for making a test bar:
#1: "Face the end and drill an accurate 60 degree hole in it with a new sharp #1 center drill." When I ordered my lathe, I ordered a #2 cobalt-steel center drill from McMaster-Carr. I didn't know which size to order, and I have not seen any guidelines on which size center drill to use when one is going to turn between centers. Is #1 generally the best size for turning between centers?
#2: "Now mount this rod between dead centers and use your lathe dog to drive it. Machine a short section, maybe 1/2" long on the end closest to the chuck." Do you mean close to the lathe dog? The lathe dog would seem to be in the way of machining at the end.
Karl
You post definitely helps. I have wondered how to make and use a test bar. I have wondered to what goal to adjust the gib adjustment screws.
I have two questions in regard to your instructions for making a test bar:
#1: "Face the end and drill an accurate 60 degree hole in it with a new sharp #1 center drill." When I ordered my lathe, I ordered a #2 cobalt-steel center drill from McMaster-Carr. I didn't know which size to order, and I have not seen any guidelines on which size center drill to use when one is going to turn between centers. Is #1 generally the best size for turning between centers?
#2: "Now mount this rod between dead centers and use your lathe dog to drive it. Machine a short section, maybe 1/2" long on the end closest to the chuck." Do you mean close to the lathe dog? The lathe dog would seem to be in the way of machining at the end.
Karl