Member postings for David Couling

Thanks John and all who have offered help with this issue. Yes, it does have a capacitor connected.

I'm now toying with the idea of replacing the motor with a 3 phase unit and a variable frequency inverter as a few others have done and also an NVR switch.

The existing motor is not in great shape, although 100 times better than it was after being removed and stripped and oil and swarf cleaned out.

Whatever, I think the idea of fitting the Dewhurst switch also is not great, and a 16A DPDT switch would be a better option.

Cheers

David

Hi Guys,

Thanks for your inputs.

Yes I will fit a TRS Gland to the motor Emgee and thanks for the interesting link.

My opinion now is that it will not be possible to connect this motor to the Dewhurst switch, since it only has three terminals. In all other examples where this is done there are four terminals...I guess for the start and run windings.

I have a detailed diagram of an 8 contact Dewhurst switch which requires the input of two wires from each winding and the mains supply.

As I mentioned previously, I've identified the start winding so I could reverse the direction of drive but that alone doesn't help.

I don't think all of the wires from the run winding have been brought out of the motor (cost cutting perhaps?) so without them I can't connect to the Dewhurst.

I am aware of the danger of the chuck unscrewing when driving the lathe in reverse but it is only intended for slow speed metric threading purposes.

Perhaps its possible to dig into the motor windings and find the ends of the windings and bring them out to another terminal. I think start windings are made from a finer gauge of copper wire than the run windings...so it may be possible to identify them.

Had anyone tried that before?

Cheers

David

Hi Guys,

Thanks for your inputs. I think I will fit an NVR in addition to the Dewhurst switch but I need a way to easily reverse the lathe for metric threading.

Emgee from your response would I be correct to say you don't see any difficulties in wiring up the Dewhurst switch with these available motor connections?

I identified the start winding but I'm not sure of the run winding and the Dewhurst switch wiring requires a connection to the start and run windings.

Any thoughts?

Cheers

David

Hi Guys,

I've added a few pictures of my Myford Lathe motor in my album.

I want to connect this motor which is a single phase motor to a Dewhurst switch but I'm not sure if it is possible the way this motor is wired., since there are only three terminals..

Mains power comes in on the AZ and A terminals.

Resistance between black and red is 3.9 ohms

Yellow and blue when switch is closed is 14.6 ohms

Could some kind person point me in the right direction how to do this if it is indeed possible.

Kind regards,

David

Edited By David Couling on 16/06/2021 17:53:38

Hi Steve, thank you for the info and the drawing; its the first I've heard that I needed to make/fit this drop arm, although I have the gears I haven't so far tried to fit them to the lathe, but I did have a quick look and saw the diameter of the T33 and T34 gears is somewhat larger than the existing 24T gear currently on the mandrel, and 'assumed' (shouldn't have done that) that the difference in diameter could be adjusted for on the quadrant clamp stud.

Looks like a drop arm is my next project....

Cheers

David

Thank you guys for all of you helpful inputs....things are becoming more clear. I'm looking to cut mainly metric threads to start with (although the lathe is imperial and fitted with a gearbox) but I have the T33 and T34 gears for the mandrel to convert.

I have downloaded some metric course and fine thread tables which I think will help. I need to study them and to make some practice cuts, and I've ordered a Zeus book.

I appreciate all of you help....thanks....David

Hi Guys,

I'm a lathe and threading newbie with a Myford ML S7 an am trying to learn how to better use it, but I have a question.....

I wonder if someone can kindly explain to me how to to calculate the diameter of the internal female thread when you have male and female components that screw together. For example if making a small round box, 30mm in diameter. A thread is cut on the male part, what would be the dimensions of the lid of the box that fits this thread? Is there an easy method of calculating the size of the clearance hole in the top and the depth of thread?

Thanks in anticipation....

Cheers David

Wow....thanks for all of your replies guys. I have searched the various sellers of gears on ebay and not surprisingly these two gears are the ones which are not available.

Pete....I would very much like to take you up on your offer...is it possible for you to PM me please.

Many thanks for all of your inputs...

Cheers

David

Hi Guys,

I know this question has been posted previously but with the passage of time, my hope is the situation may have changed and maybe someone can suggest where I can purchase a pair of T33 & T34 change gears for a Myford MLSuper 7?

Many thanks....David