Boxford Model A back gear

[jilly5599Participant @jilly5599]

Hello,

 

I have recently got a boxford model A, when I try and put it into back gear with the back gear lever fully to the left and I power on the lathe the chuck doesnt turn and the lever gets thrown back to the right. Can anyone help me on this? If I move the motor by hand it seems to turn the chuck in reverse ok but not forward.

 

Thanks

[Gerard O’TooleParticipant @gerardotoole60348]

I am no expert, but on my model A, in order to engage the back gear TWO separate levers need to be moved, what Boxford call the back gear to the rear left and the ‘sliding gear lever’ on the front of the headstock to the right.

Which lever did you move . The controls also seem to have changed over the years and so more details might help with a more appropriate answer.

Here is a photograph of the plate on my lathe. A/B is the sliding gear lever and C/D is the back gear lever

 

[Clive Brown 1Participant @clivebrown1]

Underdrive machines have back-gear operated by a single lever, of which I have no experience. Is that the OP’s machine?

The handbook says:-

“The back gear on underdrive machines is operated by a single lever mounted on top of the headstock.Two movements of the lever are necessary. The lever is normally locked in position by one or other of the socket-head cap screws fixed in the lever. These screws engage contacts of a microswitch in the headstock casting and prevent the lever being depressed etc etc”

HTH

[BazyleParticipant @bazyle]

Is this an old lathe with the motor behind the headstock and visible which is known as the ‘model A’? If it has the motor in the cabinet underneath it is an AUD.

If you have the lever on the front style then with the other lever in the ‘normal’ running position the pulley is released from the big gear (bullwheel). Then you can freely rotate the chuck as it is completely disconnected from the drive. Useful for setting up. However in old lathes sometimes the brass dog inside the headstock that moves bullwheel is too worn or broken to disengage it. So check this first. Later lathes put this lever on the top.

Then the lever on the left moving towards the front engages the backgears, if they are not damaged. If you move the side lever like this but not the front lever then the spindle is locked. Do not use this feature to hold the spindle to apply force to undo a stuck chuck or you will break teh gears. That is a very common problem.

[jilly5599Participant @jilly5599]

Yes it’s the model A with the motor behind the headstock, same as the one pictured

[Paul LousickParticipant @paullousick59116]

I have a Southbend and I believe that the Boxford is a clone. When engaging backgear, you have to disengage a drive pin on the side of the gear as shown below. The spindle is then driven thru the gears and not directly from the pulleys.

[Clive Brown 1Participant @clivebrown1]

The Boxford isn’t quite the same:- Two pictures showing fast and slow back gear positions, the lever on the front may need the spindle to be jiggled to get it to engage.

[BazyleParticipant @bazyle]

OK so it takes 2 levers. The front one is sort of removing the pin which on the South Bend is linking the pulley to the bullwheel. When disengaged, (lever to left, = pin out) the pulley should rotate freely on the spindle. Look in at the back and you should see the gear moving when you operate the front lever to produce a 1/4 in gap between gear and pulley block. This is where wear or breakage might not move it enough.
Note that there is a small groove looking like a pulley groove at the chuck side of the gear which needs one drip of oil a month and there is a screw at the bottom of one of the pulley block grooves which is an oil hole needing a couple of drips too only when using the backgear. Don’t overdo it to avoid slippy belts but don’t forget or the pully welds to the spindle.

[jilly5599Participant @jilly5599]

Just looking at the pulleys on the spindle then, should they rotate freely on the spindle? There’s a grub screw in middle which on mine isn’t tightened down to the spindle but the pulleys don’t freely rotate on the spindle, could that be my problem?

[Clive Brown 1Participant @clivebrown1]

That screw is an oiling point, to be removed and oiled esp. when using back gear, when the spindle and pully rotate at different speeds.

Sounds as if your pulley might have seized on the spindle. Could be bad news. Try oiling generously and rotating each component by hand in opposite directions. Put the front lever in the disengaged position first.

[BazyleParticipant @bazyle]

The pulley block ONLY rotates freely (plus belts to the motor etc obviously) when the front lever is moved to the left and the side lever is towards the back so the layshaft with two gears on it (big on the left, small on the right) is not engaged and also rotates freely. If the pulley block is not then able to rotate it means you have a problem with the front lever mechanism. The grubscrew you found is the oil hole.

You also mentioned the lever ‘jumps back’. It should have a spring loaded detent. Were you referring to the lever at the side?

[jilly5599]

On jilly5599 Said:

Just looking at the pulleys on the spindle then, should they rotate freely on the spindle? There’s a grub screw in middle which on mine isn’t tightened down to the spindle but the pulleys don’t freely rotate on the spindle, could that be my problem?

Jilly,

To put it another way

The spindle is effectively in two halves, the rear half always rotates at the speed set by the motor belts. The front half with the big gear on it can either run at the same speed as the back half, or at a much reduced speed via the ‘back gear’

One of your levers will connect/disconnect the two halves of the spindle the other lever will bring the back gear shaft into contact with the spindle gears for the reduced speed. Not moving the first lever and operating the second lever means you have two speeds selected at the same time and something has got to give. In your case it’s throwing the lever out

If you are unable to turn the chuck by hand without the belts moving by moving any lever it’s not the end of the world except turning big stuff or thread cutting will be a little challenging.

[jilly5599Participant @jilly5599]

Yes it’s the lever on the back of the headstock positions C or D. When it’s in the D position and the front lever is in A position it instantly gets thrown out back into the C position. I will give it a good oil and see if that helps

[Dave HalfordParticipant @davehalford22513]

I wouldn’t keep making it throw the lever out under power if I were you. It might prove to be a little expensive.

Selecting A & C  should mean you can turn the chuck by hand without the belts moving.

[Clive Brown 1Participant @clivebrown1]

The lever on my lathe moves from C to D with a slight but distinct “over-centre” feel as the gears engage. Possibly the movement on the OP’s machine is slightly restricted, but I don’t know of any means for adjustment.

[jilly5599Participant @jilly5599]

Just checked the pulleys on the spindle and they are free to rotate so that’s not the issue, I have noticed that if I turn the back gear shaft by hand when not engaged it only turns a quater turn before it catches on something to do with the selector lever as I can see this moving when turning that shaft any idea what this could be? Haven’t had chance to take the selector lever off to see if I can see anything yet

[BazyleParticipant @bazyle]

I may sound rather laborious but check each and every tooth on all four gears both for the peak of the tooth actually being present and the gap between each tooth being full depth. It sounds like a tooth is broken and the remains are still in the gap.

[jilly5599Participant @jilly5599]

It’s all working now, I loosened the retaining bolt holding the back gear shaft and slightly removed the shaft until the back gears could move without catching whatever it was catching on not sure what it was but put it back together and it’s working fine, thanks for everyone’s advice.

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