Mine leaks so much i assumed it was supposed to… what size does it take?

Make a soft alu or annealed copper washer either should stop it.

There is a dropdown box on the link to select the size required.

Mike

Mark, are you sure it is leaking from the drain plug? I had a leak on my gearbox which came from the hidden captive screw which is inside the box, this hidden screw has a rubber washer between the box and the lathe bed and that was where my leak came from, looking at the front of the g/box at the bottom left hand side there is a screw plug which  has to be removed to let you get to the hidden screw, but sadly the g/box has to be removed to replace the rubber washer, on Myfords drawing of the g/box the drawing numbers of the parts are 136, 137 and 138 (hope this is of some help)

Peter

Edited By Flywheel on 09/11/2018 08:57:17

Mark,

It is a lot of work to take the gearbox off to fit a pesky new 'o' ring in such an awkward position.

From the Myford gearbox drawing, screw # 136 is said to be captive and looks to be waisted down the length below the head to the thread. It also has a 1/4 inch spring washer to help lock it in place

Two possibilities occur to me

• The bolt is loose enough for oil to escape
• You can unscrew it, remove the spring washer and fit a plain washer below the head with a rubber seal cut from a thick tap washer below it as a good fit on the bolt shank and close the leak off from the inside

You might save a lot of time and refitting nausea by trying those suggestions.

Regards

Brian

Hello Mark,

I suggested a thick neoprene washer in particular as that will have better resilience and gap filling properties than an 'o' ring in a open situation between a washer and the gearbox housing inner surface. It may not even be machined at that point as the sealing is intended to be done by the 'o' ring sandwiched between the outer of the gearbox and what was once the mounting face for the leadscrew bracket.

The spring washer locking the bolt on the inside may also have left a rough surface to seal against, another challenge for an 'o' ring to try and overcome and a further good reason for something more rugged

This is just the approach I would try in your situation

Regards

Brian

Did you find a suitable washer?

Hello Mark,

I had a similar problem with the QCGB of my Myford S7. The sealing washers on the QCGB drain plug and the cover for the lower mounting screw on my lathe were neoprene. I noticed the part number and description in the Myford manual called out Dowty washers. After finding out what they were and sourcing them from the UK (I am in the USA) I replaced them. However, it still leaked. I put a pan under the gear box and was fairly confident the leak was coming from there because I had to constantly top it off. Kind of hard to isolate an oil leak on the Myford because of the total loss oil system. Also was second guessing myself on wether I installed the o-rings properly between the QCGB and the bed on assembly when I originally moved the lathe.

​​This is the pan I used.

When the Dowty washers arrived, I drained the QCGB and by chance looked at the sealing surface of the drain plug with a mirror and flashlight. Found a low spot that appeared to be galling from the spot facing when it was machined.

I removed the QCGB, cleaned it with mineral spirits to remove all traces of oil, especially in the threads for the drain plug. Packed the threads with cotton balls and carefully draw filed the spotface flat. Carefully removed the packing in the threads and cleaned everything again.

Reassembled everything again with new Dowty washers. After several months of monitoring, am pleased to report that the QCGB is no longer leaking.

Hope this may help someone else who is frustrated by their Myford QCGB leaking.

Kind regards,

Mike