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- Nov 9, 2018
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Clausing 5428 rebuild
- Thread starter AndySomogyi
- Start date
- Joined
- Nov 9, 2018
- Messages
- 377
Got the headstock all put together, and adjusted the main drive belts.
A big issue I had was the belts I bought were just a little bit too wide for the pulley grooves, so they were rubbing together, and the left most belt was being forced out of it's groove. It would have been a nightmare to pull the spindle out again, and order new belts, so instead, I took a razor blade and shaved just a little bit off the left belt. This cured most of the issues. In order to align it a bit better, I put a bit of a twist into the lower idler pulley, to help twist the left drive belt back straight. Not much, just twisted the idler pulley about maybe 2-3 degrees or so. That fixed the belt issue, and all the belts are staying in place nicely, and seem to be tensioned right.
There still is a bit of a vibrations, coming from the under drive. The only part down there I didn't replace was the upper variable speed drive belt. It looked basically OK, but was a bit dry. So, went ahead and ordered a new upper variable speed drive belt.
I'm not 100% sure how tight the variable speed belts should be, but they seem to work better on the tighter side (with less slop).
Ran it for a while, and the spindle bearings come up to temperature after about 10 minutes or so, get about a 20 degree rise in temperature, and then stabilized around 90 degrees F.
Interesting thing with the back-gear pulley, is when you disengage the locking pin, the breakaway torque for the spindle pulley is a lot higher than I thought it would be, but once spinning, it's very smooth, and spins very freely. Not sure if the oil just has to come up to temperature, or the bearing clearance is on the tight side. But did run it in back-gear for a while, and the spindle pulley stays cool.
Here's a quick video of the status update.
A big issue I had was the belts I bought were just a little bit too wide for the pulley grooves, so they were rubbing together, and the left most belt was being forced out of it's groove. It would have been a nightmare to pull the spindle out again, and order new belts, so instead, I took a razor blade and shaved just a little bit off the left belt. This cured most of the issues. In order to align it a bit better, I put a bit of a twist into the lower idler pulley, to help twist the left drive belt back straight. Not much, just twisted the idler pulley about maybe 2-3 degrees or so. That fixed the belt issue, and all the belts are staying in place nicely, and seem to be tensioned right.
There still is a bit of a vibrations, coming from the under drive. The only part down there I didn't replace was the upper variable speed drive belt. It looked basically OK, but was a bit dry. So, went ahead and ordered a new upper variable speed drive belt.
I'm not 100% sure how tight the variable speed belts should be, but they seem to work better on the tighter side (with less slop).
Ran it for a while, and the spindle bearings come up to temperature after about 10 minutes or so, get about a 20 degree rise in temperature, and then stabilized around 90 degrees F.
Interesting thing with the back-gear pulley, is when you disengage the locking pin, the breakaway torque for the spindle pulley is a lot higher than I thought it would be, but once spinning, it's very smooth, and spins very freely. Not sure if the oil just has to come up to temperature, or the bearing clearance is on the tight side. But did run it in back-gear for a while, and the spindle pulley stays cool.
Here's a quick video of the status update.
- Joined
- Nov 9, 2018
- Messages
- 377
When I first put this thing together, I used these vibration isolation mounts between the motor and base. Problem with them was they were too soft, especially in the shear direction, which allowed too much movement of the motor. I still wanted to add some vibration isolation to the motor, so I worked out some math and calculated resonance frequencies of various materials.
Turns out that a combination of two wood plates with these rubber sheet between them dampens a large range or vibrations. The wood and rubber both have different resonances, and combining them let’s the mount dampen a wide range. This mount design is also fairly rigid in the shear direction, so it lets me tighten the belts well. It’s not the prettiest mount, but it works well, and you almost can’t feel the motor running. That’s saying a lot because this Dayton is a very unbalanced and rough running motor.
Fixing the motor mounts raised an issue with the belts. Turns out the jack shaft pulley was very glazed over from years of belt slippage and general use. The glazed pulley was causing the new belts to slip, because there wasn’t enough friction. I didn’t want to remove it, so I’m sanding the pulley faces in place to give them a consistent finish to grab the belts.
Turns out that a combination of two wood plates with these rubber sheet between them dampens a large range or vibrations. The wood and rubber both have different resonances, and combining them let’s the mount dampen a wide range. This mount design is also fairly rigid in the shear direction, so it lets me tighten the belts well. It’s not the prettiest mount, but it works well, and you almost can’t feel the motor running. That’s saying a lot because this Dayton is a very unbalanced and rough running motor.
Fixing the motor mounts raised an issue with the belts. Turns out the jack shaft pulley was very glazed over from years of belt slippage and general use. The glazed pulley was causing the new belts to slip, because there wasn’t enough friction. I didn’t want to remove it, so I’m sanding the pulley faces in place to give them a consistent finish to grab the belts.
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- Joined
- Nov 9, 2018
- Messages
- 377
The headstock is in basically decent shape, so I’ve been working on making a new cross slide nut. The original nut was so bad that it almost jumps a tooth in certain spots, and made it impossible to make a straight cut.
Not only was the nut worn, but the screw was pretty badly worn. ACME screws don’t wear evenly, they wear Mostly on the sides of the threads. This causes the screw flats to get narrower than the roots. So a regular ACME thread nut won’t fit right, you have to make the nut crests wider than the roots.
The Machinery Handbook has the specs for an ideal ACME thread, this is just a starting point for making what I call a ‘modified ACME’ that’s designed to fit worn screws. But all of this has to be really done by feel — cut a thread, see how it fits and adjust. It’s a massive pain when you’ve only got one lathe, and have to use it to make parts for itself, and always pulling the cross screw to check fit.
After a few tries, got a decent fitting nut, so I lapped the screw to fit, as it was MUCH more worn in the middle than the ends.
I also make a video on cutting an internal ACME thread for a worn screw.
Had a bit of a challenge with the bit, made a jig to cut it at a perfect 14.5° angle.
After I installed the new aluminum ‘practice’ nut, made a few test cuts. OMG what a difference. It actually cuts straight now. Has about 0.0003 wiggle over 10”. Looks like the badly worn nut was a huge part of why it wasn’t cutting right, thinking that the nut would move on the screw, it was so worn.
With the new nut, about 0.003 backlash in the cross screw. But it had a taper with 0.010 backlash, so total of about 0.013, which is MUCH better. Before it was about 0.090 backlash.
Not only was the nut worn, but the screw was pretty badly worn. ACME screws don’t wear evenly, they wear Mostly on the sides of the threads. This causes the screw flats to get narrower than the roots. So a regular ACME thread nut won’t fit right, you have to make the nut crests wider than the roots.
The Machinery Handbook has the specs for an ideal ACME thread, this is just a starting point for making what I call a ‘modified ACME’ that’s designed to fit worn screws. But all of this has to be really done by feel — cut a thread, see how it fits and adjust. It’s a massive pain when you’ve only got one lathe, and have to use it to make parts for itself, and always pulling the cross screw to check fit.
After a few tries, got a decent fitting nut, so I lapped the screw to fit, as it was MUCH more worn in the middle than the ends.
I also make a video on cutting an internal ACME thread for a worn screw.
Had a bit of a challenge with the bit, made a jig to cut it at a perfect 14.5° angle.
After I installed the new aluminum ‘practice’ nut, made a few test cuts. OMG what a difference. It actually cuts straight now. Has about 0.0003 wiggle over 10”. Looks like the badly worn nut was a huge part of why it wasn’t cutting right, thinking that the nut would move on the screw, it was so worn.
With the new nut, about 0.003 backlash in the cross screw. But it had a taper with 0.010 backlash, so total of about 0.013, which is MUCH better. Before it was about 0.090 backlash.
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- Joined
- Nov 9, 2018
- Messages
- 377
I had a very bad and confusing belt tracking issue with my lathe. The first obvious symptom was the belts looked all cocked in the top pulley and wanted to ride out. This was caused by the fact that new belts were slightly wide and pushed each other out. Hence caused it to get slightly cocked.
This is where it gets worse. Because it was slightly cocked, the top it the belt wasn’t riding flat. In the under drive, there is a flat idler pulley that pushes on the top of the belt. The face that touched the idler, this causes a torque in the belt that pushed it further out. As it was pushed further out, this caused it to get even more cocked on the v belt grooves. As it got more cocked, they caused one side to wear heavily, which cussed to to get even more cocked which resulted in an even greater lateral load on the belt. In control theory, we call this is a classic positive feedback system.
In fact, it was so bad that when I first assembled it, the left belt was actually riding up out of its V groove. If I really loosened the tension up, it would still drag A LOT on the idler but would stay in the groove. But best case was that the idler dragged the belt about 3/4” to the left. This was causing a lot of wear on the belt.
To cure it, I came up with the idea of making a new ‘guided’ idler pulley which does not allow the belts to move sideways. In effect, the guided idler gives a positive lock for the belt position. This stopped the runaway feedback loop. I also machined a slight curve at the base of the new idler pulley grooves, and this causes the belts to self-center.
With the new idler, belts track straight and true, and no longer want to ride out of their grooves. Another benefit is it got rid of some more vibration and the lathe is very smooth now. Earlier, I re-engineered the motor mounts to isolate much of the motor vibrations.
The lathe runs pretty smooth and quiet now. There is some wear on the bed, and after leveling it, it does cut about a 0.0004 bulge near the chuck, but not terrible.
View attachment IMG_3859.MOV
This is where it gets worse. Because it was slightly cocked, the top it the belt wasn’t riding flat. In the under drive, there is a flat idler pulley that pushes on the top of the belt. The face that touched the idler, this causes a torque in the belt that pushed it further out. As it was pushed further out, this caused it to get even more cocked on the v belt grooves. As it got more cocked, they caused one side to wear heavily, which cussed to to get even more cocked which resulted in an even greater lateral load on the belt. In control theory, we call this is a classic positive feedback system.
In fact, it was so bad that when I first assembled it, the left belt was actually riding up out of its V groove. If I really loosened the tension up, it would still drag A LOT on the idler but would stay in the groove. But best case was that the idler dragged the belt about 3/4” to the left. This was causing a lot of wear on the belt.
To cure it, I came up with the idea of making a new ‘guided’ idler pulley which does not allow the belts to move sideways. In effect, the guided idler gives a positive lock for the belt position. This stopped the runaway feedback loop. I also machined a slight curve at the base of the new idler pulley grooves, and this causes the belts to self-center.
With the new idler, belts track straight and true, and no longer want to ride out of their grooves. Another benefit is it got rid of some more vibration and the lathe is very smooth now. Earlier, I re-engineered the motor mounts to isolate much of the motor vibrations.
The lathe runs pretty smooth and quiet now. There is some wear on the bed, and after leveling it, it does cut about a 0.0004 bulge near the chuck, but not terrible.
View attachment IMG_3859.MOV
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- Joined
- Nov 9, 2018
- Messages
- 377
The lathe is more or less usable now, I still need to make a bronze cross slide nut, but works OK temporarily with an aluminum one.
Now I can stop being a lathe repairman and get onto to why I bought the thing for in the first place: to make parts for this. It’s a 76 Porsche 912 (that’s a VW bus engine powered Porsche 911), and I’m swapping in a Weber carbed Subaru 2.5. So need to make lots of custom hose bungs, manifolds, flanges, fittings and all sorts of fun stuff.
Now I can stop being a lathe repairman and get onto to why I bought the thing for in the first place: to make parts for this. It’s a 76 Porsche 912 (that’s a VW bus engine powered Porsche 911), and I’m swapping in a Weber carbed Subaru 2.5. So need to make lots of custom hose bungs, manifolds, flanges, fittings and all sorts of fun stuff.
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Good write up Andy. I’m kind of the same way. If I made an aluminum practice nut....I’d probably leave it that way until it both bugged me and I had time to do it right with bronze. So many projects and not enough time.
- Joined
- Dec 13, 2016
- Messages
- 142
Andy - Just finished reading this great thread.
Man that was a lot of work. Hope you did not pay to much for the lathe.
It seems like every thing is a project but you tell yourself while you are in there might go head and do just once.
You inspired me to think about hand scraping my crossfeed and compound dovetails.
I am reconditioning my 1946 Clausing 100 mk3 lathe and upgrading to a quick change gear box and the advance apron.
My thread is under the Clausing section.
To save some time, you should check out this site:
Clausing Lathe Cross Feed Nut - Cross feed Nut for 5900 Series lathes.
3/4″ diameter shank, 5/8″-10 Left Hand ACME Threads
– please measure your screw before ordering to confirm it is correct for your machine.
Made from 360 Brass. $55
I have replace both the crossfeed and compound lead screw nuts from them. The fit was right on.
If you are in Indianapolis, Indiana- they only have one machine shop? Would think with all the manufacturing going there would be more. My wife has family down in Columbus/Hope of Indiana - always looking forward for a trip up there.
Bob G.
Man that was a lot of work. Hope you did not pay to much for the lathe.
It seems like every thing is a project but you tell yourself while you are in there might go head and do just once.
You inspired me to think about hand scraping my crossfeed and compound dovetails.
I am reconditioning my 1946 Clausing 100 mk3 lathe and upgrading to a quick change gear box and the advance apron.
My thread is under the Clausing section.
To save some time, you should check out this site:
Clausing Lathe 5900-37 Cross Slide Nut - BM Parts Tech
To place an order please email: info@bmpartstech.com
bmpartstech.com
Clausing Lathe Cross Feed Nut - Cross feed Nut for 5900 Series lathes.
3/4″ diameter shank, 5/8″-10 Left Hand ACME Threads
– please measure your screw before ordering to confirm it is correct for your machine.
Made from 360 Brass. $55
I have replace both the crossfeed and compound lead screw nuts from them. The fit was right on.
If you are in Indianapolis, Indiana- they only have one machine shop? Would think with all the manufacturing going there would be more. My wife has family down in Columbus/Hope of Indiana - always looking forward for a trip up there.
Bob G.
- Joined
- Nov 9, 2018
- Messages
- 377
Andy - Just finished reading this great thread.
Man that was a lot of work. Hope you did not pay to much for the lathe.
It seems like every thing is a project but you tell yourself while you are in there might go head and do just once.
You inspired me to think about hand scraping my crossfeed and compound dovetails.
I am reconditioning my 1946 Clausing 100 mk3 lathe and upgrading to a quick change gear box and the advance apron.
My thread is under the Clausing section.
To save some time, you should check out this site:
Clausing Lathe 5900-37 Cross Slide Nut - BM Parts Tech
To place an order please email: info@bmpartstech.combmpartstech.com
Clausing Lathe Cross Feed Nut - Cross feed Nut for 5900 Series lathes.
3/4″ diameter shank, 5/8″-10 Left Hand ACME Threads
– please measure your screw before ordering to confirm it is correct for your machine.
Made from 360 Brass. $55
I have replace both the crossfeed and compound lead screw nuts from them. The fit was right on.
If you are in Indianapolis, Indiana- they only have one machine shop? Would think with all the manufacturing going there would be more. My wife has family down in Columbus/Hope of Indiana - always looking forward for a trip up there.
Bob G.
Hi Bob,
I’m in Bloomington (south of Indy). We had a machine shop that did one-off odd machining jobs, but he retired. The other one only does production CNC jobs. And the shops I called up in Indy don’t seem to want any single part business, as the prices they quoted were crazy. One shop wanted like $1500 for literally chucking the spindle in an OD grinder and shaving a few thousands off a bearing Journal.
That’s the main reason why I set up a machine Shop in my garage: I do prototype auto engineering and fab, and everything I do is one-off custom.
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