For the initial aim of providing a power feed I would just use a small battery screwdriver, or something a bit more sophisticated, depending on what I have in the junk cupboard. Coupling it to the leadscrew in such a way that the handwheel still turned freely when needed is the problem. However, I was also thinking about a rapid feed, following discussion about fitting a split nut to the carriage and adding a rack and pinion to the saddle (on a U3). On the bigger machines I sometimes use, this is done with a motor/gearbox having an adjustable feed rate, plus a "rapid" speed in both directions, all controlled from a single lever. When the lever is in the mid position the handwheel is free, giving a switch which could be described as (? )< 0 > (?). To get the free handwheel needs a clutch in the drive scheme. Apart from the five position switch, which is more engineering than electronics, the rest is simple enough. The fine feed positions latch, the rapid positions don't. On the U3, which already has provision for driving the leadscrew at the headstock end, it would not require much modification of the lathe. On the DB/SL it's not so simple. So I think a toothed/dog clutch would be suitable, maybe mechanically operated or electrically. I'm sure it would be simpler than the rack and pinion mechanism discussed before - that looked to me to be more of an exercise in design and machining techniques than a convenient solution to an occasional problem.

I needed to reduce a piece of thick wall steel DOM tube by 0.5 mm to about 38 mm. It's 153 mm long. In order to fit it on the lathe I retracted head spindle past the stop screw. Then I made a hollowed plug fitted into the end of the tube to accommodate/recess live center of the tail stock. The part barely clears the cross slide.?

Finish leaves a lot to be desired, but it did the job.

Michael,? I would be very interested to see what you could come up with I am just at the point trying to decide which way to go with a power feed for my U3.

?

Regards

Phill

Do you think this type of setup could be made accurate enough to single=point thread?

I've been thinking about a stepper motor based power feed for the Unimat for a while.

I'm also thinking about a second stage of the project to make a full electronic gearbox

by putting a rotary encoder on the headstock to track rotation.

?

Are the group as a whole interested in me working on this and releasing the

electronic and physical designs?
I'm not sure I can justify the effort just for me, but it might be worth it if enough

of you are interested.

?

Basically, a standard NEMA 17 stepper should be able to drive the leadscrew,

and I can print a coupler out of flexible filament for minimum backlash, together

with a mount mount design to go on the baseboard.

There are a few options for rotary encoders, and a modern microcontroller

like a Raspberry Pi Pico should be good for speeds up to say 600 rpm.

?

For those who don't have access to 3D printers and the like, I may be able

to make partial kits.

?

Thoughts, comments?

?

Mike

Yes, I’ve seen the youtube video of that guy cutting the keyway / slot also. Heavy duty machining compared with the Unimat.

?

(It’s going to be one of those instances where someone says ‘I just stuck it on the 72-inch Northcurve’ - ha ha, only joking !)

Interesting that the v-groove is asymmetric.

?

Fascinating - 'show and tell' please Dick!

Hello:

?

On Wed, Nov 27, 2024 at 06:10 AM, Julius Henry Marx wrote:

I have always been in awe of that design.

Recalled having once come across a post making reference to a *.pdf posted at Model-Engineer and found it again.

Can be downloaded .

?

It is a very interesting and comprehensive article on W.D. Urwick's Metal Master Machine with a great many detailed drawings, including a cross section of the column / triangular key arrangement on p. 16/52 and the ingenious method for actually milling the key on p. 22/52

?

Bear in mind that the column is 3.50" in diameter with the key being 5" long with with 0.75" adjacent sides.

See the attached photohgraph*.

*Image courtesy model-engineer.co.uk

?

Could this be implemented on the Unimat 3?

?

Best,

?

JHM

Hello:

?

I have always been in awe of that design.

It is the lathe I would have wanted to purchase.

?

See for an article with a full description and designer comments at lathes.co.uk.

Indeed it was and still is.

Curiously, I have not seen it implemented or made reference to anywhere else.

?

From the lathes.co.uk article:

Attached is a sketch* copied from of the original patent.

* Image courtesy of lathes.co.uk?

?

In my opinion, the lack of any sort of guide in the U3's mounting column (all the Unimats actually) is one its most annoying 'features'.

?

?

Undertaking such a modification, be it the triangular gib or the one in the video requires an accurate and robust milling machine plus the knowledge to do it right lest you screw up a perfectly good column or get very little in return for your efforts.

?

In my case, unless I can find a machine shop willing to undertake the task (for a reasonable amount of $) it is bucket list material.

?

That said, I'd also be interested in photos / discussion about what and how you've done this.

As I do not have a milling machine, it would be of great help for when and if I can get someone to do this job.

?

Best,

?

JHM

Yep, I’ve looked at the MetalMaster too, the triangular gib is a neat idea.

?

I’d be interested to see what you’ve done (and how you’ve done it) also…

Hello Dick, a hashtag provides a way to categorise messages or posts (aka ‘topics’). ?I don’t do ‘social media’ but I believe it originated there.

?

It’s called a hashtag because it starts with a hash symbol (#), then has a word or small phrase (no spaces though).

You add the hashtag when you create the message / post.

?

On the groups.io web interface you can filter and search for posts (that have a hashtag added to them) by hashtag, and this really the extent of their usefulness and functionality.

?

I tried some tests to see the functionality of hashtags on the forum - as (I think) you use email you will have received them with the subject ‘Hashtag test’ - the URL for the web interface version of the same thing is /g/Unimat/topic/hashtag_test/109791066

?

For use in the groups.io forum the hashtags have to be created first, and it looks as though this has to be done through the web interface. Currently there are only a few hashtags defined.

?

Hashtags could be created for each (distinct) variety of Unimat, it would then be up to users to remember to use them. It wouldn’t prevent users replying to posts with details on a totally different machine, or going off on any kind of tangent, but it would at least give a clue as to what machine the post is about. Or of course you could just explicitly state the variety of machine in the text of the opening post.

?

If you are only posting by email (not using the groups.io web interface) then you would put the hashtag at the end of the subject line. As I said the hashtag has to exist in the system first though if it is going to be any use.

?

Hope that helps a bit?

A few years ago I became interested in David Urwick’s triangular gib key for use on my Unimat vertical column to maintain rotational position when raising or lowering the head.

It has bean a great help to me as rotational position can now be fixed while raising or lowering the head. An example of its use is when a long slot must be cut in a vertical column. I have had this requirement on several occasions and now I have a means of doing just that.

Maybe others can benefit from this also.

Dick

--

http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

Can you explain what a hashtag is. I don’t think I have ever heard of it. I might be able to learn something.

Thanks

Dick

?

--

http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

Hello:

On Tue, Nov 26, 2024 at 10:32 PM, Mike Gidley wrote:

... my way of having a power feed ...

Nice job.

The OEM power feed attachment has a 40:1 ratio and the carriage screw feed advances 0.02mm / turn.

I still have to see what specs I can get from the motor I have to see if it will do.

ie: check the nominal voltage RPM / torque, do the math and see how variable the spec can be.

?

No idea what voltage it runs at but it is probably 12v or less.

?

One thing I have not mentioned but can be seen in the photographs is that for this modification to be viable, the U3 has to be put 'on stilts'.

Otherwise you cannot hang the motor under the PF pulley.

?

No big deal as mountimg it higher makes it much easier to clean under it, otherwise it is a 30/45 minute chore with a rag and a toothbrush.

My U3 sits on hardwood blocks to give it a 65mm clearance under the ways.

It ended up being just enough, should have gone for a minimum of 80mm.

?

Best,

?

JHM

I have been a member of all three groups way back when they were yahoo groups and I believe the moderators of both U3 groups disapeared. So members decided to migrate to just the Unimat Group. I know that some of us have Sherlines as well as Unimat 3/4, SeigC0, Combi 218, As well as the DB/SL variants. We can all learn something even if it is the other type of lathe. Believe me when say this group is well mannered, informed and respectful unlike some others I'm on. As someone said it ain't broken.

This is my way of having a power feed on my Uni3.

I found a small 24v motor with a 600:1 gearbox ratio. I made a variable powersupply "1.25v to 30v" and i can get the speed down to 19 revs per minute. It is reversable with an on off on switch. It connects directly with the lead screw with a simple slot in an aluminum adaptor. I simply slide it to the left when not in use. P.S. I have no idea where the 24v motor comes from.