Motor Shaft Question

[Chip Hacket]

Just retired. Yay! My lathe motor broke. Boo!
My HF 8 x 12 lathe had an IEC 71 frame, single phase 120V, 3/4 hp motor which I can't find anywhere, so I'm substituting. IEC 80 frame @ 3/4hp seems like a good idea but mounting is a problem. I have settled on an IEC 71 frame, 3 phase 230V, 1/2 hp.

My question is: Can I extend the shaft? The standard for IEC 71 seems to be 14mm diameter with 30mm length. My old motor which had to have been an oddball has a 16mm diameter with 50mm length shaft.
Can I make a sleeve to go over the new shaft kinda like shown? Not much meat there.

 

[Alexander McGilton]

The motor on my 1440 lathe caught fire a few years a go. I then replaced it with a NEMA 56c motor of the same hp and speed. The only modification to the mechanics was to enlarge the base mounting holes and enlarge the pulley bore. and make a step pyramid shaped key. All mill work with endmills and boring head, worked out well as the lathe was not functional at the time.

How are you going to make that with out the lathe?

Does the motor pulley have some meet to be bored out? Doubling the thickness of the red colored web will do a lot to reduce vibration and fatigue. perhaps go as far to add independent keys and set crews on the extension.

 

[markba633csi]

That's 1mm on each side- about 40 thousandths. Plenty of meat if made from steel. Possibly you could find a piece of steel tubing and slit it-
that's the easiest way if you can find some with the right wall thickness or close to- I'm thinking electrical conduit or some cheap steel
import tubing like for a gazebo or maybe tent poles?
Then fill the open end with a short slug of 14mm rod and epoxy it in

-Mark

 

[Alexander McGilton]

How far cantilever is the drive belt? How far in does the pulley encase red colored component? These factors could greatly influence matter.

 

[Chip Hacket]

The motor on my 1440 lathe caught fire a few years a go. I then replaced it with a NEMA 56c motor of the same hp and speed. The only modification to the mechanics was to enlarge the base mounting holes and enlarge the pulley bore. and make a step pyramid shaped key. All mill work with endmills and boring head, worked out well as the lathe was not functional at the time.

How are you going to make that with out the lathe?

Does the motor pulley have some meet to be bored out? Doubling the thickness of the red colored web will do a lot to reduce vibration and fatigue. perhaps go as far to add independent keys and set crews on the extension.

`

The motor on my 1440 lathe caught fire a few years a go. I then replaced it with a NEMA 56c motor of the same hp and speed. The only modification to the mechanics was to enlarge the base mounting holes and enlarge the pulley bore. and make a step pyramid shaped key. All mill work with endmills and boring head, worked out well as the lathe was not functional at the time.

How are you going to make that with out the lathe?

Does the motor pulley have some meet to be bored out? Doubling the thickness of the red colored web will do a lot to reduce vibration and fatigue. perhaps go as far to add independent keys and set crews on the extension.

Hi and thanks. There are two pulleys that go on the shaft. One is a timing belt pulley (with not much meat to cut) the other is a v-belt pulley. Probably could bore that if I had to. I should have shown the lathe in the beginning. At low speeds both belts are in use. So the distance between the shafts make sort of a triangle and the distance is dictated by the belt lengths. I knew the IEC 71 would satisfy those dimensions. I did consider a C-face 56c but it was way to big. Also, the lathe I'll be using to make parts needed is my little Taig Lathe. Yea, I think independent set screws is a good idea.

 

[Chip Hacket]

How far cantilever is the drive belt? How far in does the pulley encase red colored component? These factors could greatly influence matter.

So the V-belt pulley is 38mm, the timing belt pulley is 18mm. Yes. That is longer than the old motor shaft. In other words the old motor shaft did not encase all of the V-belt pulley (which was at the shaft end). Although it was captured with an end cap. The end of the shaft was threaded.

 

[Alexander McGilton]

Yeah I see, that is a predicament. short of isolating the commutator, welding an extension prior to machining to a more desirable shaft diameter and length. There is the issue of how to slip the bearings on and off.
I did notice there is a taped hole on the end of the motor shaft with a cap screw. you could go with the initial modeling design, give it small through whole, and order a long metric cap screw to hold the red piece in and keep it under compression. Not perfect but it will reduce the chance of tensile failure.

 

[Chip Hacket]

Yeah I see, that is a predicament. short of isolating the commutator, welding an extension prior to machining to a more desirable shaft diameter and length. There is the issue of how to slip the bearings on and off.
I did notice there is a taped hole on the end of the motor shaft with a cap screw. you could go with the initial modeling design, give it small through whole, and order a long metric cap screw to hold the red piece in and keep it under compression. Not perfect but it will reduce the chance of tensile failure.

That's a good idea Alexander, I think I will do that. I hope I can make it work, I've already invested a fair amount into it. I was checking that very hole and a 10-32 fits right in. A little sloppy but fits. I did a search here and found an M5 course is almost identical. Think I'll get an M5 though. Do you think that 1mm will be enough?

 

[Alexander McGilton]

The motor shaft is very likely a M5x0.8mm. slightly larger than .190" and 1/32" pitch is close of .79mm. for a few revolutions they will mate but will eventual bind, expect compromised strength as well. Indecently this is how for low pressure fittings there are universe thread fittings for both British and American threads.

 

[Chip Hacket]

The motor shaft is very likely a M5x0.8mm. slightly larger than .190" and 1/32" pitch is close of .79mm. for a few revolutions they will mate but will eventual bind, expect compromised strength as well. Indecently this is how for low pressure fittings there are universe thread fittings for both British and American threads.

View attachment 412393

Shades of grey.