# powered lead screw



## firebird (Oct 8, 2011)

Hi

This mod is part of the work I have been doing to my lathe. Its a windscreen wiper motor with 2 gears I have cut using the same method as described in 3000 rpm on a myford.

[ame]http://youtu.be/BoFSz2LGgkM[/ame]

Cheers

Rich


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## bearcar1 (Oct 8, 2011)

That's pretty neat Rich. Have you any thoughts about making up a belt shield? Not so much for keeping stray digits form imposing themselves as much as keeping the swarf meanies from invading the gear teeth and causing undue wear and tear on the belt. would love to see a video of it doing some real work. Where did you source the belt for it?

BC1
Jim


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## HS93 (Oct 8, 2011)

That looks great, I am about to do something similar with my ML10 but with a stepper motor, have you got any pictures info of how you did the gear on the lead screw.

thanks

Peter


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## Blue_Rock (Oct 8, 2011)

Nice, well thought out mod Rich. I'm thinking about making a similar mod to my Chinese 9x20. Did you use PWM to control the motor speed?


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## firebird (Oct 9, 2011)

Hi

Jim, yes a shield will be made. That's very negligent of me not to mention it. As you say not so much as a finger guard but more to keep swarf out of the belt. It turns quite slowly so is not really a danger. If you look at the video you will see that i designed the belt to be quick release so that i can use the lead screw manually. It is the motors own weight that holds it down. anything getting caught in the belt and the motor automatically tips up.

The belts were sourced from e-bay

http://www.ebay.co.uk/sch/i.html?_f..._nkw=t5+timing+belt&_sacat=See-All-Categories

The gears are available as well but I chose to learn how to make them myself as I needed some large ones as well for the head stock mod.

I'll sort out a video of some real work for you.

Peter, I had to do a mod on the end of the lead screw to extend it a bit to provide room for the gear, I'll post some pics later.

I have to admit that the electrics were not my work. My good mate Julian (Barney dog) designed and built the control box for me. I'll give him a nudge and get him to post a few details.

Cheers

Rich


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## firebird (Oct 9, 2011)

hi

Here's a video of the lathe cutting some steel using the power feed. I'm taking a .010 cut. Note there is now a guard over the belt.

[ame]http://youtu.be/3MnsBobAJ1w[/ame]

cheers

Rich


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## firebird (Oct 9, 2011)

Hi Pete

I'm assuming the ML10 is similar to the ML7, a lot of myford stuff is interchangeable.

The lead screw hand wheel is held onto the lead screw with a self locking nut which is used to adjust backlash in the lead screw. I had to make a spacer to move the hand wheel out a bit to give me clearance for the 12mm wide gear. It can just be seen in this picture.







Its steel, drilled through 7/16. A slot milled in one end while the other end has a tang machined onto it.

The hand wheel required a little modification. Mounted on a 7/16 mandrel a flat face was machined onto the back side.






The gear is bored to be a snug fit on the hand wheel boss and drilled and tapped 5mm.






The hand wheel has mating 5mm holes drilled. You can also see in this shot that the hand wheel has been counter bored. The nut is machined to fit in the counter bore. This leaves just enough thread for the nyloc nut to catch.






The gear is fixed to the hand wheel with 2 countersunk cap head screws.






The hand wheel fitted back onto the lathe. The locking nut has not been fully tightened as yet.






Cheers

Rich


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## kf2qd (Oct 9, 2011)

That's not Lucas, is it?


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## firebird (Oct 9, 2011)

Hi Kf2qd

I'm not sure. I work in the motor trade so any cars that are being scrapped I try to get the wiper motor off. They are all pretty much the same.

Cheers

Rich


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## Noitoen (Oct 9, 2011)

Some older wiper motors don't reverse easy. If the motors has magnets, it will go both directions just by changing polarity. If not you have to put a bridge rectifier on the field coils to reverse easy.


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## Julian (Oct 12, 2011)

Hi Guys.

 As Rich mentioned I built the controler for this project. I went to Maplins and got one of their pre-built PWM controlers and a box. I already had the switches in stock but they could have also been bought at Maplins. Power supply was one that Rich bought from Ebay. As the motor is 12v it can be controlled by the cheap pwm controler which is built for a maximum of 15v.

A quick explanation is the power goes into the controler and is modulated according to the position of the speed control knob. This feeds a couple of switches linked together. One controls the polarity fed to the motor to control the direction of the motor. The other controls whether the motor runs continuously or whether it runs via a push button. The latter gives short bursts for positioning or fine control.

There is no need for any other circuitry like rectifiers because we selected a magnet motor. Connections to the motor were selected to use the fastest combination of windings. The system is not built for fine control but to give the capability of fast travel or slow feed speed. This allows use of these motors rather than a stepper motor and all the associated drivers.

Julian.


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## Swede (Oct 21, 2011)

Nice job! I did something similar years ago to an old lathe and it was a HUGE help... I used a DC gear motor and a variable DC supply for "dial-a-feed" much like I have built-in on my old Hardinge lathe, which uses a DC motor for both long and cross feeds. It's hugely helpful to be able to adjust the speed "on the fly" because you can see the finish or cut you are getting. Plus, it's handy and fast.

This is a mod I'd recommend to anybody without power feed.

A good source for small DC gearmotors and pulleys, belts, etc, is (in the USA at least) "Burden's Surplus Center"

http://www.surpluscenter.com/


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## MachineTom (Oct 28, 2011)

Did you not have power feed on the leadscrew? I always wondered if Myford would have made a machine that was only hand powered for the leadscrew. I have the hand wheel on the end of the leadscrew, just figured it was used to position the carriage.


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## Blogwitch (Oct 28, 2011)

Rich,

That would be ideal for cutting large pitch threads.

As you may well know,when you try to cut large threads, or multi start, by using the lathe gearing from the spindle, you are liable to start smashing gearing and banjo's on your machine. I did it on my Atlas, trying to cut 2 TPI using the spindle to drive the leadscrew.

If you drive the whole machine from the leadscrew (main power off), as you are doing for cutting, it eliminates all the pressures on your gear train and drives the spindle at the same time.

Don't try it for cutting normal threads, only large pitches that aren't shown on your lathe tapping charts, otherwise you will again start to get things broken.

John


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## firebird (Oct 29, 2011)

Hi

Thats a good idea john, thanks

Cheers

Rich


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## MachineTom (Oct 29, 2011)

Bogs: I did not read of any connection between the spindle, and the leadscrew wiper motor. Without a stepper/servo type motor, driven in phase with the spindle, there is no way to make threads, single or otherwise. As far as the leadscrew driving the spindle, with a 12V wiper motor for power? quick guess its torque is nowhere near close to what is need to overcome internal friction with any power left to machine metal.


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## Blogwitch (Oct 30, 2011)

Tom,

If Rich can drive the leadscrew and cut metal with it, then there should be more than enough power, through the very low gear ratio required, to drive the spindle.

I have cut large pitch threads using the leadscrew on my old Atlas lathe using handle power to turn the leadscrew, and the effort involved is very little. The actual cutting action of the tool is negligible when doing threading as it is only removing tiny amounts of material. 

It is the only way to cut large pitch threads on these types of machines without doing damage to the gear trains. If you look at much larger lathes, they have the beefed up gearing to take the strain of driving the saddle so fast. In fact, because of the increased gearing, and taking into account the usual very slow speed of the spindle, the speed the leadscrew turns and so the saddle movement requires the reactions of a s**thouse rat to stop it before it hits the chuck. But even very large machines are limited to the large thread pitches they can cut when driving gears from the spindle.

In fact, for anyone with the smaller types of machines, say the mini lathe with their very fragile gears, I would recommend the leadscrew method when cutting the larger thread ranges that the machine manufacturers say that their machines can do. You are taking out the risk of smashing up the gears on your machine. Set up the gear ratio that the manufacturers give, but instead of turning on the spindle, turn the lathe by means of the leadscrew with a handle on the end instead, not only does it take the strain off the gear train, but you also have total control of the speed the saddle travels at.


John


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