Variable speed for my Atlas 10" Lathe

[dnalot]

I am between projects so I have been cleaning and servicing my machines and making some machine upgrades. This week I turned my attention to my (little lathe) a 10”Atlas built in 1948. Over the past few days I have been working to repower it with a salvaged treadmill motor and (scr) control board. The original motor was a ½ HP 1750 RPM AC motor. The machine had 16 speeds depending on how you arranged the belts & back gear, from 28 RPM to a little over 1400 RPM. The new motor is 2.25 HP 4600 RPM DC-130V. With the new treadmill setup I now have variable speed from 100 RPM to 1400 RPM in straight gear and can reduce that by a factor of 3 when using the back gear. The machine makes far less noise and is much smoother running. I salvaged the motor & control board for nothing and paid $35 for an e-stop switch, potentiometer and a tachometer. To protect the lathe from damage I used a shear pin to mount the pulley to the drive motor. The chuck is a thread on type so I did not provide for a reverse but it would be very simple to add that feature. This was a simple upgrade and very worthwhile.

Mark T

 

[Blogwitch]

Mark,

I don't want to piddle on your parade, but please give a little more thought to your conversion before calling it finished.

I remotored my old pre WW2 10F a few years back, before selling it on later, and retained the original size of motor, a 1/2 HP one. I was going to fit a 1HP one, but thought better of it, and my decision proved I was right.

I am sure the lathe spindle could take such power, but the ancilliaries definitely can't.

I had a few close calls with my lathe, and luckily the motor and drive system stalled before any damage could be done except for one occasion, which luckily I got away with a couple of bolts and one gear, plus the reverse gear case, which I had recast in bronze.

Unless you have got the shear pin correctly calculated then what you have to realise that all gears and many other parts are made from monkey metal (I think you call it Mazak), and if the motor hadn't have stalled, I would have been shelling out lots more pennies replacing more broken items, especially gears.

John

 

[Niels Abildgaard]

Mark
Looks very nice and simple.
My VFD/motor is 1.1 kW/6 pole i.e. aproximately 5 times more torque possibl than the original.I have no shear pin as the belt will slip at same rating as before.
Are these motors with brushes?Are actual power rate displayed somewhere?

 

[dnalot]

I don't want to piddle on your parade, but please give a little more thought to your conversion before calling it finished.

I agree. I have the belt tension set to let the belt slip fairly easy and the shear pin is 3/16 Aluminum. I have the luxury of having another large heavy lathe so I'm not tempted to try and over work the old Atlas. And I'm not calling the project "done". I plan to replace the cheap tach with a tachometer that also reads in feet per minute that I plan to install once I'm sure this setup will workout OK.

Mark

 

[dnalot]

Are these motors with brushes?Are actual power rate displayed somewhere?

The motor has brushes. The label on the motor lists it at 2.25 HP peak with 130 Volt DC power. The controller has a pot for controlling power output. I have set mine to the lowest setting. The motor came with thermal overload protection and I left that in place. In researching this motor I found that many people have removed the thermal overload circuit.

Mark

 

[canadianhorsepower]

I agree. I have the belt tension set to let the belt slip fairly easy and the shear pin is 3/16 Aluminum. I have the luxury of having another large heavy lathe so I'm not tempted to try and over work the old Atlas. And I'm not calling the project "done". I plan to replace the cheap tach with a tachometer that also reads in feet per minute that I plan to install once I'm sure this setup will workout OK.

Mark

This is the same motor set up that I use on mt Taig Lathe for 4 years.
I did go with a serpentine belt pulley set up and a spring load set up with
a "climbing" ability if something goes wrong :hDe:

As for your Tach and FPM you can use the same one with a different input
for the reading

 

[Niels Abildgaard]

The motor has brushes. The label on the motor lists it at 2.25 HP peak with 130 Volt DC power. The controller has a pot for controlling power output. I have set mine to the lowest setting. The motor came with thermal overload protection and I left that in place. In researching this motor I found that many people have removed the thermal overload circuit.

Mark

By power I meant wattage while working.My VFD is the biggest of the manufaturers line without wattage readout regretably and I think this must be a good indicator of tool and lathe wellbeing.It is not trivial to measure three phases and calculate power.

 

[Herbiev]

I must agree that vfd's are great. Especially when arthritis makes it hard to change speeds with pulleys and belts.

 

[dnalot]

Just a follow up, the DC treadmill motor is working out great and I am happy with how it works. The Chinese tachometer never worked so I bought an American made tachometer kit. It reads RPM or SFM (has metric option).

MachTack machine tachometer kit is made by a fellow in California. This was a very nicely done kit with easy to follow instructions on assembly, testing and use. http://www.machtach.com I used the half size unit. Assembly time was about an hour.

I used the Hall Effect sensor that came with the Chinese tachometer. The kit came with a sensor that uses reflective tape, but has instructions for using a number of other sensor systems. Using two magnets I can read down to 16 RPM.

I did not like having the panel so near the chuck so I have relocated the panel to a post off the back of the machine and relocated the E-stop to a more natural location near my left hand. I also installed two outlets into the E-stop housing for the tachometer’s power supply and a LED lamp’s power supply.

 

[dnalot]

Hi

Well it’s been almost one year since I repowered the old Atlas so I thought I would let you all know how it has worked out.

This has been my go-to lathe for small parts because it has smooth jaws on the chuck and the chuck is very accurate an allows parts to be re-chucked with very little change from center (English made chuck). With the variable speed motor it just got even better. Another reason I like this old lathe is it can turn as low as 20 RPM, compared to the 70 RPM of my Chinese 12x36 lathe. The repower did away with most of the clanging noise and the machine runs much smoother resulting in a finer finish on the part. And twisting a knob on the fly is far better than stopping to change belt position.

So after many many hours of use I can safely recommend this type of motor.

Mark T

 

[Blogwitch]

Well done Mark.

As I stated before, I did have misgivings about what you were trying to do, but it looks like you pulled it all off OK, but I still give you the warning about the monkey metal parts.

I really do miss my old 10F, it would do almost anything I could throw at it, but had to get rid of it because I didn't have enough room in my shop for two lathes.

John

 

[10K Pete]

John, you referred a couple of times to monkey metal parts. I see no where
in his posts where Mark says anything about monkey metal parts.....

Are you saying that the Atlas has pot metal parts in it? I did not know that!
I always thought that they were all iron/steel.

/?????????

Pete

 

[dnalot]

Hi

Yes the Atlas has some monkey metal parts. The gears for a starter, and the handles and a lot of the smaller parts. I have the good fortune of having most of two other lathes for spare parts. And none of the parts would be hard to reproduce.

My repower has not presented any problems with breakage and I have had two instances where the belt slipped "as expected" when I took to big of a bite. Crashing the tool into the chuck might be a bit much but I have never crashed a lathe YET. Is repowering risky? Yes but those that never take a risk are destined to never be any better than average. I like to push things as far as I can.

Mark T

 

[10K Pete]

Thanks for the info Mark. I never knew they had parts like that in them. Are the parts Zamac or a true cast aluminum or ?????

Thanks,
Pete

 

[Blogwitch]

Pete,

I think the parts are all what you call Zamak, which does provide a problem the older they get. They are renowned for changing their structure and get weaker as time goes on and can fail without any noticeable reason.
Even the large drive pulley is made of the stuff, and the very thin plate spokes are easily overcome. When I was building mine from a box of parts that I had purchased, there were two of those pulleys in the box that had given way at some time.
Mark is lucky, he has the quick change gearbox, mine didn't but came with a smashed reversing box (rare as hens teeth) and I glued the broken bits together and had one cast in bronze. Slightly smaller but once I got to fiddle with it, it did the job.

John

 

[Barnbikes]

Not to be a pain but do you have a write up on how you did the conversion? I scrapped out a treadmill a couple years ago for my 10F but have not done anything with the parts because I was not sure how to control the motor. I have all the the electrical components that were on the treadmill. The controller is the part that scares me at the moment.

 

[10K Pete]

Thanks John. I'd kinda forgotten how zinc alloys can age badly even though I've seen lots of it over the years. I don't know exactly what other metal is in with the zinc that makes it go bad, but not all castings exhibit the problem.

Pete

 

[dnalot]

Hi

Not to be a pain but do you have a write up on how you did the conversion? I scrapped out a treadmill a couple years ago for my 10F but have not done anything with the parts because I was not sure how to control the motor. I have all the the electrical components that were on the treadmill. The controller is the part that scares me at the moment.

Basicly I just used the motor, transformer and the motor control board from the treadmill. The wire leads are normally well labeled on the control board. The power leads to the motor can be reversed to suit your rotation needs. The tread mill probably had a sliding speed control, it will be labeled as to its resistance. For a few dollars you can replace it with a rotary type.

The flywheel on the motor can be discarded and if the motor has an overheat circuit it can be eliminated. If the motor has 4 wires coming out of it the 2 blue ones are the ones for the overheat protection, cap them off.

I have wired an emergency off switch that powers the lathe's motor, lights and cheapo DRO setup. Note that the speed control must be set to zero when the lathe is powered up. If it is not the motor control board can not calibrate itself and it will not send power to the motor. Install a switch in one of the power leads to the motor for turning the lathe on and off during a work session. Using the switch you can turn the lathe on and off without changing the speed setting during a work session.

Mark T

 

[dnalot]

Thanks John. I'd kinda forgotten how zinc alloys can age badly even though I've seen lots of it over the years. I don't know exactly what other metal is in with the zinc that makes it go bad, but not all castings exhibit the problem.

I have to agree that no all castings exhibit the problem. My parts machines have some pot metal castings that you can plainly see are disintegrating and others that look good. The lathe I am using the castings look like new. My guess if it was build during WWII it was probably an inferior part. Pot metal is made from zinc,lead,tin,copper,cadmium,iron and aluminum. looks like a lot of room to play with the alloy.

Mark T

 

[10K Pete]

I've been keeping an eye out for a tread mill that I could salvage. But I've never been able to find one around here! I'd like to have one for the mill and one
for the lathe and, maybe, one for a drill press.

Mark, where are you in WA? PM me if'n you want.

Pete