Unimat milling table - post modification

Hello:

In the process of finishing up work on my Unimat 3 milling table, I now have to address a major oversight in its original design.

The column where the milling head runs up/down does not have a key and as a result, loosening the bolt to take the head up or down will always move the register it had, no matter how careful you are.

I've seen a video of a chap who put the post on a mill, ground a 1/4" slot and maintained the register via a screw that threads into the head to fit in the slot, but it ended up having some play.

It is a good idea, simple and straightforward but I think that a square bottom slot is not the right choice.

I'm inclined to have a cone shaped slot ground into the side of the post and keep the register in place with a screw albeit with a shape to match the cone and just long enough so that it does not bottom out.

Something like this *:

I think that the cone shaped slot with the cone shaped bolt will do away with any possible play: the head will always be put back in the same position.

To move the head up or down will then need two operations: first loosen the register bolt, the loosen the milling head bolt and then reversing the operation once the desired height is found.

Not a problem and a solution to the head losing its position which is very annoying in a milling machine.

Any suggestions?

Thanks in advance.

Best

JHM

* sorry for the sloppy sketch.

Edited By Julius Henry Marx on 13/11/2022 19:19:15

The sloppy sketch is absolutely fine, JHM … it shows your thinking, concisely

My only concern would be that, every time you clamp the assembly you will put a pair of grooves in the walls of the vee groove

I suggest you think about some way of incorporating a shim, to avoid such damage.

MichaelG.

Or a wedge shaped piece of metal about 30mm long with a hole in the wide side to take a parallel end turned onto the end of the screw

Edited By JasonB on 13/11/2022 19:36:11

Not sure whether this works on your machine, but a trick used by other owners of round column machines is to fasten a laser pointer to the head and mark a vertical line on the opposite wall. I've not tried it but I know a chap who did. The vertical line needs to be at right angles to the milling machine table.

.

Using your current design, with a reverse shouldered bolt type screw, the shoulder being at the point end, and the screw being at the screwdriver end, then it fits in a reamed hole which has a larger diameter tapped part on the outside edge, does that make sense?

Might be a bit better than relying on the screw thread for positioning.

Hello:

@MichaelG

> The sloppy sketch is absolutely fine ...

Thanks. 8^)

> ... will put a pair of grooves in the walls ...

Indeed, that would most probably happen. Maybe not all the time but surely often enough.

I was rather relying on the physical properties of the steel used to manufacture the post vis-a-vis a brass screw (?) plus the fact that it would not really have to be tightened, just screwed in enough to touch the groove and register.

Like adjusting gibs on a lathe saddle.

@JasonB

> ... wedge shaped piece of metal about 30mm long with a hole ...

Great idea!

Thanks a lot for the drawing. 8^)

That's the solution, no doubt about it.

@duncan webster

> ... trick used by other owners of round column ...

Yes, that could work.

I have one of those small/cheap laser pointers and have attempted to use it for similar endeavours.

But will only work if the thingy is well/firmly mounted and the machine can be kept exactly in place at all times.

Thanks to all for your fast reply.

Best,

JHM

Pete. touches on it above: both the ideas shown so far use a screw thread as part of the locating mechanism. That is not good engineering.

Any play between male and female threads with the tapered end to it will hamper repeatability. Even with the elongated piece of metal, side to side play in the threads will mean it will not repeat well.

There is also the issue of ensuring the tapered part or dog point is concentric with the male threads (or the male threads are concentric with the other feature - easier to achieve with a dog point than a tapered end as you can make the dog very long, grip that to cut the threads and then shorten it).

Could I throw the triangular gib (see lathes.co.uk Metalmaster) into the mix?

Cutting the groove for the triangular gib in the clamp block may be harder for some depending on what tooling they have.

The wedge could have a dowel rather than a screw that could have pressure applied in a number of ways. Or if cutting into the clamp block than just cut a standard keyway and shape a deeper wedge with parallel sides at the thick end to fit into the keyway and you can still use a screw

What about the modifications/additions to the Unimat 3 column made by Maurice Rhodes?

Some of his modifications were discussed recently on this forum.

Look e.g. for the topic “Maurice Rhode’s Unimat 3”.

Regards,

Jouke

Edited By Jouke van der Veen on 13/11/2022 21:12:47

The taper angle would need to be rather steep to prevent the wedge becoming stuck in the taper slot and I don't think the unimat column could take that comfortably. Unless sound machining capabilities are available, small variations in slot width or taper will cause the wedge to bind as you wind the head up and down. Average machining will do as long as the slot is truly inline with the column, then a brass tapered tip lock-screw will do just fine - it's a small machine.

How about making it as a sprung plunger as on the Coronet Ruby lathe? You already have a clamp.

Dave8

You'll have to excuse my poor image, hopefully this helps you understand what I was trying to explain.

The blue part is the thread, the green part is an accurately turned diameter that would locate in a reamed hole, as long as the red taper and green location diameter are turned in the same set up it should give pretty repeatable location.

I'm sure there are better solutions but this is almost identical to your original Idea and a pretty simple solution.

Edited By Pete. on 13/11/2022 22:46:20

One of the most elegant solutions was Mr Urwicks triangular key used on the metalmaster universal machine. Read about it Here on the lathes page.

Mike

Just noticed DC31k mentioned the Urwick Metalmaster key earlier. I must read more carefully.

Edited By Mike Poole on 14/11/2022 08:44:59

urwick

What a fantastic little machine tool, a great solution to the problem of the op.

Did scaled down castings ever get produced by anyone?

Hello:

@Pete:

> ... excuse my poor image ...

Nah!

> Thanks for taking the time to draw it up.

> ... helps you understand ...

Yes, now I get what you meant.

> ... a pretty simple solution.

Indeed it is and very doable, so to speak.

@Joseph Noci 1:

> ... don't think the unimat column could take that ...

The column is barely Ø 28mm and I only have ~ 5.5mm aluminium casting to thread something in.

> ... sound machining capabilities ...

That is available but what may not be available is the time/interest for the shop to do it or do it for a reasonable price.

I have to keep the job as straightforward and simple as possible.

> ... as long as the slot is truly inline ...

No doubt about that, there's a huge late 1940's Bridgeport mill and an exprerienced chap to do the job.

> ... it's a small machine.

Yes it is.

The whole mill with the new (lighter) motor weighs in at ~ 7.50 kg.

I have to go to the machine shop early next week and will take the parts and the sketches.

The diameter of the column, the small amount of material to thread into and the simplicity of the solution has me thinking that Pete and Joseph have made a point so I think I'll go with that.

The cone shaped slot to be made on the column is common to all the solutions which may boil down to how the spindle head gets its register rather than how it gets gripped, which is a function of the screw on the other side.

I was thinking that I will probably need to pressure fit a short external brass tube to accomodate the threads and the reamed hole and have the aluminium casting take that part and nothing else.

Eventually (if needed) the part could be modified/replaced with little effort.

We'll see how this plays out.

Once again, thanks to all who replied.

Best,

JHM

I've often thought about putting an Urwick style triangular gibb on my Unimat column, but since I now have a larger mill drill with a dove tail column it is not so likely to happen.

John

I also ran into this on the ME site

plus the original patent

Edited By Ady1 on 14/11/2022 10:09:55

A question.

Is the Unimat 3 clamp on the milling column different from that on the Emco Compact 5? The latter is from a thin walled casting and has hollow spacings. So, you can not machine it everywhere to ad new features.

Of course, You could make your own solid clamp and modify that.

Regards,

Jouke