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rtbcomp
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Got a couple of oilers for the headstock. The ones that were on were difficult to fill. After some deliberation a thread of 2BA was ariived at, although the other lathe has a different thread.
A car tyre valve cap sits nicely on top to keep dirt out. I have heard of people using the flip-tops off toothpaste tubes.
A car tyre valve cap sits nicely on top to keep dirt out. I have heard of people using the flip-tops off toothpaste tubes.
rtbcomp
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^^ Cheers, that's worth knowing.
I've sorted the parting-off problem mentioned earlier. Sharpening the tool and setting up from basic principles from this video got it working OK. I've bought a narrower parting tool to reduces the load, so we'll see if that makes a difference.
I've sorted the parting-off problem mentioned earlier. Sharpening the tool and setting up from basic principles from this video got it working OK. I've bought a narrower parting tool to reduces the load, so we'll see if that makes a difference.
How are you taking to finally having a lathe up & running, (bar the walking after treadling issue
rtbcomp
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Managed to cut a 3/4 BSW male thread:
The first problem was that the belt kept slipping when taking a decent cut, so I removed the belt and turned the pulley by hand, this also had the advantage that I wouldn't crash the tool into the chuck by being a bit slow on the clutch lever.
I was very pleased with the fit of the 3/4 BSW nut, so to remove the chuck and see if it would screw into the backplate. Nope. Too big, the book says the nose thread is 3/4 inch standard Whitworth, so I tried the nut on the spindle. Very slack indeed.
As I want this thread to take a chuck I'll try remounting it and cutting a bit deeper, that should be interesting.
Another problem I had was the cutting tool seemed to be drawn into the workpiece. At a thread depth of say, 15 thou I set the tool to take another 2 thou off and as soon as I started cutting the DTI showed a further movement of about a thou. When I zeroed the top slide to wind the saddle back the clearance between the workpiece and the tool hadn't closed up, so I reckon there's some backlash in the slide. This would also explain the difficulty of taking a good cut, the lathe added a thou or so onto what I'd already set up.
The first problem was that the belt kept slipping when taking a decent cut, so I removed the belt and turned the pulley by hand, this also had the advantage that I wouldn't crash the tool into the chuck by being a bit slow on the clutch lever.
I was very pleased with the fit of the 3/4 BSW nut, so to remove the chuck and see if it would screw into the backplate. Nope. Too big, the book says the nose thread is 3/4 inch standard Whitworth, so I tried the nut on the spindle. Very slack indeed.
As I want this thread to take a chuck I'll try remounting it and cutting a bit deeper, that should be interesting.
Another problem I had was the cutting tool seemed to be drawn into the workpiece. At a thread depth of say, 15 thou I set the tool to take another 2 thou off and as soon as I started cutting the DTI showed a further movement of about a thou. When I zeroed the top slide to wind the saddle back the clearance between the workpiece and the tool hadn't closed up, so I reckon there's some backlash in the slide. This would also explain the difficulty of taking a good cut, the lathe added a thou or so onto what I'd already set up.
rtbcomp
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@rtbcomp That looks too much like hard work- you planning a motor?
I've just fitted a washing machine motor to the lathe (because there was a washing machine in a skip opposite my house).
The J-Section belt works perfectly on the flat surface of the treadle pulley.
I used one of these from China to control the speed:
It just connects in series with the motor. This is the circuit I built:
Basically the ganged switch selects Off-Fwd-Reverse-Fwd, the No Volts Release starts & stops the motor and the speed controller does what it says on the tin. The relay reverses the connections on the field coil to reverse the motor. The fan is set up to cool the motor and provision is made for a worklight.
rtbcomp
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It works reasonably well, certainly better than using the treadle!
With the motor running at 2790 rpm the treadle pulley runs at 120 rpm which in turn means the spindle rotates at 615 rpm using the pulleys shown in the above photo. The max speed of the motor is about 18000 rpm, which means I could add an extra pulley pair with a 1:6 ratio. This would increase the available torque.
The speed does vary with load, taking a deeper cut you have to turn the juice up a bit, and when you move the tool away from the workpiece the revs rise noticeably.
A more sophisticated drive circuit that uses the tacho on the motor would be better, also I could experiment with the tappings on the field coil, maybe I could get more torque?
As mentioned I scrounged the motor and bought the speed controller, everything else was what I had lying around.
It does tend to rock a bit if you go a bit too fast due to the treadle being out of balance, I'll try to balance it up with magnets.
With the motor running at 2790 rpm the treadle pulley runs at 120 rpm which in turn means the spindle rotates at 615 rpm using the pulleys shown in the above photo. The max speed of the motor is about 18000 rpm, which means I could add an extra pulley pair with a 1:6 ratio. This would increase the available torque.
The speed does vary with load, taking a deeper cut you have to turn the juice up a bit, and when you move the tool away from the workpiece the revs rise noticeably.
A more sophisticated drive circuit that uses the tacho on the motor would be better, also I could experiment with the tappings on the field coil, maybe I could get more torque?
As mentioned I scrounged the motor and bought the speed controller, everything else was what I had lying around.
It does tend to rock a bit if you go a bit too fast due to the treadle being out of balance, I'll try to balance it up with magnets.
rtbcomp
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I've had a day to play with it and it's quite good really.
The implication of using a series wound motor is that under no load it spins very fast, even with the speed control turned down but there isn't much torque which means it's slow to accelerate to the set speed due to the 27kg flywheel.
As mentioned in the previous post, due to the speed variation with load you have to develop a technique whereby you adjust the speed knob as you take the cut to keep the speed constant.
I used a magnetic earth clamp to balance the flywheel, that worked well.
I experimented with the field coil tappings, using the brown & pink (0.001R) made the speed very difficult to control and using the red & brown tappings (0.002R) gave slightly more torque so I've settled on that configuration.
After an hour's messing about the motor doesn't even begin to get warm.
Using a countershaft with the appropriate pulleys would improve responsiveness and the control knob would work over a wider range, but as this lathe is very original I'll keep the treadle and fit a 3 phase motor with vfd and move the current set up to the other round bed lathe which is heavily modified anyway. In the meantime I'll fit a larger knob to get finer control of the speed.
The implication of using a series wound motor is that under no load it spins very fast, even with the speed control turned down but there isn't much torque which means it's slow to accelerate to the set speed due to the 27kg flywheel.
As mentioned in the previous post, due to the speed variation with load you have to develop a technique whereby you adjust the speed knob as you take the cut to keep the speed constant.
I used a magnetic earth clamp to balance the flywheel, that worked well.
I experimented with the field coil tappings, using the brown & pink (0.001R) made the speed very difficult to control and using the red & brown tappings (0.002R) gave slightly more torque so I've settled on that configuration.
After an hour's messing about the motor doesn't even begin to get warm.
Using a countershaft with the appropriate pulleys would improve responsiveness and the control knob would work over a wider range, but as this lathe is very original I'll keep the treadle and fit a 3 phase motor with vfd and move the current set up to the other round bed lathe which is heavily modified anyway. In the meantime I'll fit a larger knob to get finer control of the speed.
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You need a stationary engine and a lineshaft set up 
Dieselman 63
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Now that’s just showing off!
rtbcomp
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Made a handle to turn the spindle by hand for thread cutting &c. It's basically a pedal off a kids bike which was in the same skip as the washing machine mentioned in post #29.
The thread on the end of the spindle is 3/8 BSP, so I made an adapter with a thread to screw into a malleable iron coupling on one end and a plain shank which was supposed to be a shrink fit in a hole drilled in the pedal. That bit didn't go well, I got the pedal hot but the shank got stuck so it sticks out more than anticipated, nevertheless it works.
The thread on the end of the spindle is 3/8 BSP, so I made an adapter with a thread to screw into a malleable iron coupling on one end and a plain shank which was supposed to be a shrink fit in a hole drilled in the pedal. That bit didn't go well, I got the pedal hot but the shank got stuck so it sticks out more than anticipated, nevertheless it works.
rtbcomp
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Treated the lathe to a Chinese quick change toolpost (QCTP). I had to make a spacer 11/16ths of an inch thick to stand the QCTP on so the tool lines up with the centre of the workpiece with the height adjustment mid-range. It's made a big difference to getting the tool height correct, no more faffing with spacers.
I also had to find a longer fixing bolt.
I also had to find a longer fixing bolt.
Bill Edwards
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That's a heck of a lot better than messing with spacers, I may just do the same and should have a very long time ago!
