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Better Gibs for mini lathe

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moditwell

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I have decided to dump the factory gibs and make brass ones for the compound and cross slides. The new gibs are machined accurately to have maximum contact area with only one side of the dovetail. The new gibs performed so well that only very light touch to the set are required. Put a bit more force and it becomes tight. The new gibs have totally transformed the mini lathe, it has become very rigid but still allow silky smooth movement when cranking the handle, it's very smooth! Parting operations are no more nightmares. Here are some pictures
 

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Danuzzo

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Very nice. In the photos, Looks like a significant dimensional difference, at least in one dimension. Pleased that it worked out so well for you.
 

rleete

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Stupid question time: how do you mill at an angle like that? Adjustable vise?
 

SmithDoor

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The gib looks good.
The problem maybe in the dovetail or screw.
1) What is the nightmares.
2) What is the dovetail angle.

Dave

I have decided to dump the factory gibs and make brass ones for the compound and cross slides. The new gibs are machined accurately to have maximum contact area with only one side of the dovetail. The new gibs performed so well that only very light touch to the set are required. Put a bit more force and it becomes tight. The new gibs have totally transformed the mini lathe, it has become very rigid but still allow silky smooth movement when cranking the handle, it's very smooth! Parting operations are no more nightmares. Here are some pictures
 

kop

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I had a conversation with Joel (if that needs an explanation-ask)
The result was new cross and compound gibs for my MK II Atlas.
The lapping of the gibs was a work out.
Remove the lead screws and assemble first the cross and then the compound.
Remove the obvious high spots, damage, abuse, and begin adjustment and lapping.
Apply compound, adjust, stroke, stroke some more, wipe, check, adjust, lap, ~wash , rinse , repeat.
Hours later with a serious case of arm pump, the likes of which I haven't had since an abortive attempt at motocross racing in the '70's.
The improvement is immediate and dramatic. I now have a usable lathe.
The previous maintenance was the spindle bearings.

In all the mods and maintenance were not only effective but necessary.
 

matthew-s

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Parting operation is a nightmare.
Dovetail is 60 degrees
very neat.Can you share your work holding approach for securing gib while machining the dovetail? It’s a small, thin, part to machine.

fettling of the compound is on my to-do list.
 

SmithDoor

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very neat.Can you share your work holding approach for securing gib while machining the dovetail? It’s a small, thin, part to machine.

fettling of the compound is on my to-do list.
I make a jig to cut the angle in flat bar.
Tapper jibs are more fun after cutting the then I bolt the flat bar in cross slide and the use side zero out the slide then cut the taper very slowly. Some time you to true up the other side first.
Some times on old lathes you see holes drill in cross slide on taper jib side this where how made a new taper jib

Dave
 

matthew-s

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I make a jig to cut the angle in flat bar.
Tapper jibs are more fun after cutting the then I bolt the flat bar in cross slide and the use side zero out the slide then cut the taper very slowly. Some time you to true up the other side first.
Some times on old lathes you see holes drill in cross slide on taper jib side this where how made a new taper jib

Dave
Thanks - that makes sense.
I'm guessing you have a tilting vise, and set it up perpendicular to the table?
 

SmithDoor

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Thanks - that makes sense.
I'm guessing you have a tilting vise, and set it up perpendicular to the table?
The last time I had Bridge Port mill and made the vise jaw for jig and till the head.

Dave
 
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Charles Lamont

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The new gibs performed so well that only very light touch to the set are required. Put a bit more force and it becomes tight.
Years ago the revered George Thomas pointed out that relying on setscrews bearing on dimples in the gib is less than ideal, because as soon as you move the slide there is a tendency for the screws to ride up the dimples. He advocated the addition of a dowel with a firm to tight fit. I have so recently done this to the topslide of my lathe that I have not tried it out yet. (The lathe is currently being stripped down to almost the last nut and bolt for its 48-year service).
 

goldstar31

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Charles might I respectfully endorse the comments which are still available in GHT's Model Engineer's Workshop Manual.
Again, respectfully, GHT used a peg through the gib to anchor the gib and there was a further little lock. screw of 2BA which was on the vertical slide. Mine, is on an old Perfecto vertical slide as I could not afford a Myford one.
Idly commenting further Ian Bradley of him as an individual and also as Duplex with Dr Norman Hallows added extra gib screws in his Myford top slide and illustrated in his Book on the Myford.

I'm guessing but the machine was the ML7 as the Super 7 has a different top slide lock.

Thank you for jolting my memory.

Best Wishes
Norman
 

KenC

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The problem with the gibs on my mini lathe is that the edges were sharp and the edges needed to be removed, but more significantly the gibs were slightly bent. Now corrected the mini lathe still has the original gibs.
 

goldstar31

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I see ArcEurotrade in Leicester are still selling brass replacements complete with new gib screws
 
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moditwell

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Years ago the revered George Thomas pointed out that relying on setscrews bearing on dimples in the gib is less than ideal, because as soon as you move the slide there is a tendency for the screws to ride up the dimples. He advocated the addition of a dowel with a firm to tight fit. I have so recently done this to the topslide of my lathe that I have not tried it out yet. (The lathe is currently being stripped down to almost the last nut and bolt for its 48-year service).
Use more set screws to distribute the load across the gibs. This way you will have less problems.
 

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ignator

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I make a jig to cut the angle in flat bar.
Tapper jibs are more fun after cutting the then I bolt the flat bar in cross slide and the use side zero out the slide then cut the taper very slowly. Some time you to true up the other side first.
Some times on old lathes you see holes drill in cross slide on taper jib side this where how made a new taper jib

Dave
Dave, I have to repair the taper gib, with my current compound slide top. It uses a 55 degree dove tail, I just got the cutter in the mail yesterday. There are two issues with the current compound, the top is not flat, even though it has a ground finish. Where the T-slot is, it's raised above the rest of the compond top slide, this raised area was scraped to make it look like a precision flat surface, I have no idea what they were doing with this 2004 manufactured lathe, other then I've determined that every incorrectly manufacture component was not thrown away but made into the lathe I have now. Anyway, where it is ground goes up hill from the T-slot drop down edge, to the crank end. And I recently put a sine bar on the side to attempt to set the angle precisely, but the side is not parallel with the slide dovetail. So I'm going to re-machine the dovetail to be parallel with the side, (or the side to be parallel with the dovetail). The current trapezoidal gib is tapered, so I assume I need to do as I think you indicated, and clamp that in place to machine it parallel to the opposite dovetail, so it will slide without binding. This compound uses a screw on each end of the gib to adjust it for correct fit. This adjustment range was already exceeded as the screw that pushes the gib ran out of its travel, and I made a spacer that fit under this flange head screw to push the gib farther.
 

SmithDoor

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Dave, I have to repair the taper gib, with my current compound slide top. It uses a 55 degree dove tail, I just got the cutter in the mail yesterday. There are two issues with the current compound, the top is not flat, even though it has a ground finish. Where the T-slot is, it's raised above the rest of the compond top slide, this raised area was scraped to make it look like a precision flat surface, I have no idea what they were doing with this 2004 manufactured lathe, other then I've determined that every incorrectly manufacture component was not thrown away but made into the lathe I have now. Anyway, where it is ground goes up hill from the T-slot drop down edge, to the crank end. And I recently put a sine bar on the side to attempt to set the angle precisely, but the side is not parallel with the slide dovetail. So I'm going to re-machine the dovetail to be parallel with the side, (or the side to be parallel with the dovetail). The current trapezoidal gib is tapered, so I assume I need to do as I think you indicated, and clamp that in place to machine it parallel to the opposite dovetail, so it will slide without binding. This compound uses a screw on each end of the gib to adjust it for correct fit. This adjustment range was already exceeded as the screw that pushes the gib ran out of its travel, and I made a spacer that fit under this flange head screw to push the gib farther.
Sound great any photos

Dave
 

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