GH600 feeds have died.(Not)

[IRTParticipant @irt]

The feeds on my Warco GH600 have stopped working on my lathe tonight.

I did hear a noise. Nothing too dramatic – it like a piece of plastic snapping.

I could not see anything wrong and wasn't even sure if it had come from the lathe.

A few minutes later, I noticed that I had lost feeds in both directions.

The lead screw is turning, but there is no movement if I engage feed, nether the cross slide or carriage move.

Similarly, if i engage threading, nothing moves.

There are no nasty noises, the levers feel as normal, and when engaged, the hand wheels are locked, indicating that the selection is working as normal.

The lathe is still under warranty, so I will speak to Warco before I strip anything, but I am trying to get an idea of what may be wrong. Has anyone else had a similar problem?

[IRTParticipant @irt]

Loss off feeds.

[Clive FosterParticipant @clivefoster55965]

Sounds like the overload shear pin has broken.

Pretty much all lathes with a threading / feeds gearbox above basic benchtop size have a shear pin or two in the feed shaft and leadscrew drives to protect things if you run hard into something. Some just have one somewhere on the input side to protect both drives, some have one for each one on the output side.

Usually a slender brass or steel pin but I'd not be surprised by plastic on a modern machine.

Clive

[IRTParticipant @irt]

I did not realise there was a shear pin in the saddle.

I will go and have another look at the drawing.

I hope it is that simple. As there are no nasty noises this indicates that nothing major is broken (I hope).

[Martin ConnellyParticipant @martinconnelly55370]

The Smart and Brown model M has a 1/16" x 1" silver steel shear pin in the drive flange/leadscrew flange interface and the flanges have hardened bushes. It's a pain to access and replace if it shears.

Martin C

[Jed MartensParticipant @jedmartens56976]

Here's a piccy of the back of the apron of my GH600…

You can clearly see the half-nut, which raises when you engage the threading lever. I can't think how the lead-screw could still be turning, and the threading lever engaged, yet the saddle doesn't move.

Are you positive that the lead screw is turning when the threading lever is engaged? Perhaps the lead screw sheer pin has snapped, but a bit of friction is causing the lead screw to turn. Until you place a load on it…

[Dave HalfordParticipant @davehalford22513]

Most shear pins are in the gearbox to leadscrew joint.

The half nuts engage directly apron to screw.

power feed goes through gears.

Both not working ought to be the shear pin though off load the leadscrew might still turn due to friction

[BC ProfParticipant @bcprof]

A quick test to identify whether it is a drive to the lead screw or a drive from the lead screw to the saddle. fault.

With no drive to the lead screw selected ( easy with power off !) engage the half nut . If you can not now move the saddle using the hand wheel then the lead screw / saddle drive is working as it should. ,Leave the half nut engaged and turn on the power with a lead screw drive selected Is a shear pin had failed then the saddle will not move .

Brian

[IRTParticipant @irt]

Problem solved – pure operator error!

Very embarrassing to admit, but at east it does not cost anything.

I had knocked the lathe speed to the slowest. At this speed, it takes the lathe a significant number of seconds to take up the backlash.

I panicked because of the earlier unexplained noise, and rushing to get ready for tea too, I thought the worse.

After walking the dog and calming down a bit, I went to check Jed's suggestion, and all was obvious.

I still can't explain the noise I heard. Probably something fell off the table.

Sorry.

… Right, how do I delete posts???

[not done it yetParticipant @notdoneityet]

You can’t – unless the mods smile and give you a second chance.🙂 Otherwise here in perpetuity – perhaps to remind you not to jump to hasty conclusions before posting? Most things like this are easily solved by the operator, given a little thought, careful consideration of the signs and symptoms followed by simple diagnosis.

Even obvious mishaps can be useful threads for new starters or the inexperienced.

[Howard LewisParticipant @howardlewis46836]

Experience allows you to spot the mistake the next time that you make it

Like, twice, my lathe stopping completely.

TWICE wasted an afternoon circuit checking before spotting that I had locked down the Emergency Stop button!

Howard

Edited By Howard Lewis on 20/06/2020 12:17:50

[Martin ConnellyParticipant @martinconnelly55370]

My band saw stopped latching on. I had to hold the on button down to keep it running. First thing I checked was that the microswitch that detects when the bow is all the way down was clicking and not stuck in, that was ok. Next open the motor to gearbox cover to do the same on the microswitch in there. That was clicking nicely and not stuck as well. Opened up the box with the start stop switches, no broken or detached wires. Resort to the multi-meter and check the microswitch circuit is working which it was. After a bit of head scratching and chin stroking I closed the cover over the motor belts and the microswitch clicked again. I then had to raise the cover slightly to put the screw back in and there was a click. The adjustment (which there isn't any of) of the switch was out. It had been finely set when made and over the years of use the top of the plastic plunger had abraded enough to act like the lid was open. The adjustment was bent the thin plate top of the cover slightly to make the switch close again. So about an hour spent trying to find a fault where all that was needed was a calibrated thump with a mallet in the right place. It's like the joke about the guy with a hammer getting paid for knowing where to hit a ship's engine to fix it.

Martin C

[Jon GoughParticipant @jongough33651]

IRT firstly thank you for not deleting this post, (I'm a newby) So,on returning to my lathe I changed the speed setting…

same lathe (2 days old) GH600

same fault – no drive of cross feed (testing the lathe while still on delivery pallet)

same result – lathe set at 40 RPM

backlash taken up… problem resolved.

thanks for sharing your experience, it saved me an embarrassing call to Warco

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