Stripped lead screw
- Thread starter SDoxey
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monophoto
Member
Wow!
What does the female thread inside the ram look like. You may need to replace the entire ram assembly.
Just curious - how old is the lathe? Have you been cleaning it regularly? I have the same fundamental question as Ken - how could this much damage occur? And why is the wear more severe in the middle of the screw? This is very strange.
What does the female thread inside the ram look like. You may need to replace the entire ram assembly.
Just curious - how old is the lathe? Have you been cleaning it regularly? I have the same fundamental question as Ken - how could this much damage occur? And why is the wear more severe in the middle of the screw? This is very strange.
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MRDucks2
Member
Looks like there could be enough left to get the measurements to have a local machine shop make it if the rest is in working order.
Hard to tell from the photo of the threads are mostly worn, mostly pulled or a combination. If the carrier portion of the tail stock seems fine, there could have very well been a metallurgy issue with the screw/quill portion.
Hard to tell from the photo of the threads are mostly worn, mostly pulled or a combination. If the carrier portion of the tail stock seems fine, there could have very well been a metallurgy issue with the screw/quill portion.
Woodchipper
Member
Can the screw be found at a hardware store, industrial supply or fastener store as Fastenal? Our Ace hardware has tons of screws. It's my place to go for fasteners. Can you access a parts list to get the spec's on the screw to match it?
MRDucks2
Member
John - this the machine screw (used to be an acme thread I believe) that runs the quill itself in and out of the tailstock assembly.
monophoto
Member
I would expect that normal wear would be greatest at the right-hand end of the screw (as shown in the photo) since that area is always contained within the ram and in contact with the female threads inside that component; conversely, I would expect less wear at the other end of the screw where the threads are exposed when the ram is extended. So its curious that the most severe wear appears to be in the middle of the screw, with what appears in the photo to be slightly less wear toward the right-hand end.
So that leads me to also wonder about a metallurgical flaw - perhaps uneven heat treating that caused the metal in the middle of the screw to be softer than the metal toward the end.
I suggest reaching out to Jet for assistance. They may be able to provide a replacement screw. But they also may be able to help diagnose what has caused this abnormal wear pattern.
rherrell
Member
I can make you one , my Jet 1642 has a 3/4"x 16tpi. left hand lead screw, is yours the same?
WriteON
Member
I was going to suggest to contact you. Does not get any better than what you will come up with
rherrell
Member
Only the first 1" or so of the quill is threaded (left hand). That's an easy fix, I'd bore it out oversize and make a bushing out of bronze to fit, then I would cut the threads in the bushing.
Get a price on new parts and I'll beat it.
Get a price on new parts and I'll beat it.
SDoxey
Member
It's about 5 years old
I haven't cleaned it very often...
And I have no idea why the middles softer.
SDoxey
Member
Wow! Thanks so much!
I'm trying contact jet right now and hopefully they can send me one but if not I'd love to buy one from you.
Here's a link to one I found
That looks like its been over-cranked at the end of the range when pulling the quill back in. You should avoid over-tightening the quill when it is fully retracted, as that could certainly grind down the threads like this. Especially if it was rarely cleaned...never know what kind of grit may get in the threads and help the process along...
MRDucks2
Member
Lol. Yeah, I mentioned a local machine shop and failed to mention my local machine shop is Rick in NC. Maybe not so local.
MRDucks2
Member
It's still a 3/4" screw. Seems like it would need quite a bit of force to actually over crank it. Not sure you would achieve just using the hand wheel. Maybe with a lever or cheater of some sort.
I don't mean it was a single event...but over years of use and wear.
monophoto
Member
Sam described his lathe as being about five years old. That's relatively new.
Having completed my spousally-assigned chores for this week, I was able to get down to the shop today to take my lathe apart to see what the leadscrew looks like. My lathe is about 9 1/2 years old, and while I think there may be some wear toward the end, it looks pretty good, especially compared with Sam's lead screw. Since my lathe is twice as old as Sam's, that only causes more concern about why Sam's is wearing the way it is.
Its interesting that my lathe (a Turncrafter) has standard threads while Sam's Jet has Acme threads - I would thing that Acme threads should be stronger than standard threads, but that's expectation may be based more on a guess than anything else.
I also inspected my ram more closely - the female threads inside the ram only go in about an inch - which means that there is only about an inch of contact between the lead screw and the ram regardless of how far the ram is extended. So my initial expectation that there should be more wear toward then end of the threads might be incorrect.
Even so, I'm still puzzled about how Sam's lead screw experienced so much wear in the middle of the thread. After all, the lead screw and ram only move when advancing the tailstock up to the workpiece, or when drilling. The amount of wear shown in the picture suggests either that the metal in the middle section of the lead screw is extremely soft, or else there has been an abnormal amount of movement between the leadscrew and ram - perhaps vibration due to misalignment between the headstock spindle and the tailstock? I would think that it would be prudent to find out why that wear has occurred before replacing the leadscrew.
Having completed my spousally-assigned chores for this week, I was able to get down to the shop today to take my lathe apart to see what the leadscrew looks like. My lathe is about 9 1/2 years old, and while I think there may be some wear toward the end, it looks pretty good, especially compared with Sam's lead screw. Since my lathe is twice as old as Sam's, that only causes more concern about why Sam's is wearing the way it is.
Its interesting that my lathe (a Turncrafter) has standard threads while Sam's Jet has Acme threads - I would thing that Acme threads should be stronger than standard threads, but that's expectation may be based more on a guess than anything else.
I also inspected my ram more closely - the female threads inside the ram only go in about an inch - which means that there is only about an inch of contact between the lead screw and the ram regardless of how far the ram is extended. So my initial expectation that there should be more wear toward then end of the threads might be incorrect.
Even so, I'm still puzzled about how Sam's lead screw experienced so much wear in the middle of the thread. After all, the lead screw and ram only move when advancing the tailstock up to the workpiece, or when drilling. The amount of wear shown in the picture suggests either that the metal in the middle section of the lead screw is extremely soft, or else there has been an abnormal amount of movement between the leadscrew and ram - perhaps vibration due to misalignment between the headstock spindle and the tailstock? I would think that it would be prudent to find out why that wear has occurred before replacing the leadscrew.
Woodchipper
Member
Acme threads are thicker and shouldn't wear. I'm guessing improper grade or temper in the screw.
monophoto
Member
I took advantage of having taken apart the tailstock of my lathe to inspect the lead screw to clean off all the old lubricant, wood dust and metal debris, file the edges of the alignment groove to eliminate any burrs that might have been created over time, polish the outside of the ram with a scothbrite pad, clean out the Morse taper with a shotgun brush, clean out the bore in the tailstock housing, relube the lead screw, and then reassemble everything.
Altogether, this only took about 15 minutes, and it's amazing how much smoother the tailstock is now.
Note to self - a little periodic maintenance makes the lathe seem like a completely new machine. If you need to hide in the shop, but have nothing in mind to make, just do a little housekeeping.
Altogether, this only took about 15 minutes, and it's amazing how much smoother the tailstock is now.
Note to self - a little periodic maintenance makes the lathe seem like a completely new machine. If you need to hide in the shop, but have nothing in mind to make, just do a little housekeeping.