Mini Lathe

[bill-e-boy]

I am not sure if this is the correct Topic to put this post under but it is the closest I can see where it would fit

In a nutshell I scored a used Emco Unimat 3 mini lathe via the local (NZ) online auction site

The lathe was complete with all the usual fittings and had the milling attachment as a bonus. Also had lots of extras like tooling and other little doodads that often come with second gear. It was a little tatty though. The milling attachment is at the top of the photo

I cleaned it up and freed up some stiff handle knobs. I did not take a chance so I replaced the main shaft bearings following the instruction manual for setting the required bearing pre-load

At this point I had used the lathe a few times but I was not happy with having to change pulleys al the time to change speed. The motor is two speed but the way this is configured there is quite a drop in power when using the slower speed.

I work as an industrial electrician in the real world. I had to hand a suitable single phase to 3 phase variable speed drive unit but no small motor. I then went about looking for a small 230V 3phase motor. I ended up buying the smallest 2 pole motor that the local motor importer had. It may be small in 3 phase terms but is quite large next to a mini lathe

As I intended to keep the original drive unit to be dedicated to the mill head I needed to machine up some new pulleys for the motor and lathe. I did this in my big lathe as the Unimat just would not have the power to drive a form tool

 

More to come

 

 

 

[Brudda]

10 hours ago, bill-e-boy said:

I am not sure if this is the correct Topic to put this post under but it is the closest I can see where it would fit

In a nutshell I scored a used Emco Unimat 3 mini lathe via the local (NZ) online auction site

The lathe was complete with all the usual fittings and had the milling attachment as a bonus. Also had lots of extras like tooling and other little doodads that often come with second gear. It was a little tatty though. The milling attachment is at the top of the photo

I cleaned it up and freed up some stiff handle knobs. I did not take a chance so I replaced the main shaft bearings following the instruction manual for setting the required bearing pre-load

At this point I had used the lathe a few times but I was not happy with having to change pulleys al the time to change speed. The motor is two speed but the way this is configured there is quite a drop in power when using the slower speed.

I work as an industrial electrician in the real world. I had to hand a suitable single phase to 3 phase variable speed drive unit but no small motor. I then went about looking for a small 230V 3phase motor. I ended up buying the smallest 2 pole motor that the local motor importer had. It may be small in 3 phase terms but is quite large next to a mini lathe

As I intended to keep the original drive unit to be dedicated to the mill head I needed to machine up some new pulleys for the motor and lathe. I did this in my big lathe as the Unimat just would not have the power to drive a form tool

 

More to come

 

 

 

I’m interested. 

[peteski]

Yes, this is an interesting topic, but the title stinks!  It is too nebulous.  It looks to me more like you have a generic question about mini lathes (those questions show up here from time to time).  If you titled it "Unimat 3 mini lathe upgrade", or "Unimat 3 mini lathe modification" that would be much more informative.

 

Owning a Sheline lathe, I think that a 3-phase motor is a bit of an overkill, but heck, if it works for you then all is good.

[Ace-Garageguy]

Very interesting.

A few years back I bought an as-new first generation Unimat (1960s vintage), and have been happy with its capability to do fine work...especially after several upgrades.

There's a sizable Unimat users community, and lotsa parts and accessories still available as NOS.

My other lathe is a 12 inch gap-bed unit I bought back in '96.

Sometimes I think I'd like another unit sized between the two, but so far they've managed to handle everything I've asked.

Edited May 3, 2021 by Ace-Garageguy
TYPO

[bill-e-boy]

Thanks for replies

Bruda - I take note of comment re title - but not sure on how to change

Peteski - 3ph motor may be overkill as far as size - its just the smallest motor I could get hold of. The main focus of the exercise was to have variable speed but without the drop off in torque as happens with the original motor. I could have sourced a smaller DC motor and drive but as I already had an AC drive available I decided to go down this route

Ace-Garageguy - my big lathe is about half way between yours and a Unimat 3 or SL

[peteski]

Actually it was me suggesting title change. To edit your own post click on the 3-dots on the upper right of the post. There will be 2 or 3 options available (the 3rd choice would be "edit"). But they only give a limited time to edit your posts (like a day or two), so it is probably too late now.

[bill-e-boy]

Ok -on with the modifications

The original motor was mounted via a plate to the rear of the head stock

As this would not be the case with the new motor I mounted the motor and the lathe on a piece 3mm ally plate. The motor mount holes were slotted to allow belt tensioning. 

The plate has rubber feet to stop the whole lot moving around the bench when it was running

The motor and the lathe were dully mounted onto the plate

The motor wired to the VSD and a control box mounted on top of the motor with the run/off switch and speed dial pot

The VSD is set up to run at a maximum frequency of 80hz as above this motor power tends to fall off. With the speed up ratio of the pulleys the top speed is the same a the original motor of 8000rpm at 80hz

I rarely run it above 40hz and can run it right to 10hz without any issues

The mods have been well worth the effort and having the ability to change speed at the touch of a button is magic

The lathe as it is today

 

And with the milling head attached

The only job I have left to do is make up a cover for the belt drive - must get around to it - one day

Thanks for looking

 

 

 

 

 

 

[peteski]

I had to chuckle at the size of the motor compared to the entire lathe - looks like you have more than ample torque there!  The modification looks good.  You seem to be quite a machinist (is that your vocation)?

[Brudda]

On 5/4/2021 at 2:33 AM, bill-e-boy said:

Ok -on with the modifications

The original motor was mounted via a plate to the rear of the head stock

As this would not be the case with the new motor I mounted the motor and the lathe on a piece 3mm ally plate. The motor mount holes were slotted to allow belt tensioning. 

The plate has rubber feet to stop the whole lot moving around the bench when it was running

The motor and the lathe were dully mounted onto the plate

The motor wired to the VSD and a control box mounted on top of the motor with the run/off switch and speed dial pot

The VSD is set up to run at a maximum frequency of 80hz as above this motor power tends to fall off. With the speed up ratio of the pulleys the top speed is the same a the original motor of 8000rpm at 80hz

I rarely run it above 40hz and can run it right to 10hz without any issues

The mods have been well worth the effort and having the ability to change speed at the touch of a button is magic

The lathe as it is today

 

And with the milling head attached

The only job I have left to do is make up a cover for the belt drive - must get around to it - one day

Thanks for looking

 

 

 

 

 

 

Nice!

[Bainford]

Agreed! Nice set up. 

[Deuces ll]

This is the one I bought a dozen years ago... I still haven't plugged it in yet....?

Back then I only paid 369.00 bucks for it... Now Arbor Freight is asking 699.00 for the same lathe....?

 

Edited May 14, 2021 by Deuces ll

[bill-e-boy]

A modeler friend who had a Unimat 3 replaced his with something similar a while back. Said it is a lot better as it has a lot more features like the ability to screw cut and has a proper chuck. He does serious modelling like scratch building a 1/32 of a Caterpillar D8 dozer and lots of steam stuff.