Unimat milling table – post modification

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

@Gray:

> … single cone point screw …

> … over time form conical indentations …

Yes, I'm afraid so.

> … Jason's suggestion of a separate mating Key …

It is a good idea but it will probably be expensive to get done properly.

> … an attachment some while back in MEW …

Thanks for taking the time to find the photos.

Nice system, never seen it before.

After having a look, I stepped back a bit and had another look at the problem at hand.

My first thought was that this is a rather simple no-big-deal milling table which these days commands funny money prices on ebay and such, but NASA/watchmaker's equipment it is not. 8^°

As it has been pointed out, there are drawbacks to milling the slot, machining the mill head, tightening the screw, etc. all of which are genuine and would like to avoid.

As I looked a bit more at the head I thought that I may be able to work out a solution using a system similar to the one used to tilt the head at an angle without much compromise or expense.

The photo shows the markings used to tilt and fix the head at an angle, each marking representing a 5° variatuion and separated by ~ 2.0mm.

Obviously, finer/more accurate angles need a different method, but this one seems to work for 5° increments in a repeatable and consistent manner.

In the end, as all I want is to be able to repeatedly and consistently be able to put the milling axis on the same spot every time (and overcome Emco designer's lapse) I thought I may be able to use what the head already provides me with.

ie: an always vertical 2.0mm slot at the back of the milling head.

Once tightened, the screw fixing the head in place leaves an open ~2.0mm slot traversed by the tightening bolt.

Because of how this part was machined and save severe damage, it will always travel along an axis parallel to the milling column's own axis with the accuracy imposed by the tightening of the part to the column.

This makes it a reliable reference and very useful toward finding a solution.

A 2.0mm x 4.0mm slot could be easily machined on the column and a 2.0mm strip of hard brass measuring 40.0mm x 15.0 mm could be held in place by the bolt , not tight but not loose either.

The brass strip would always slide inside the slot when the bolt is loose and prevent the head from swinging sideways more than just a bit, bringing it back into register as the bolt is tightened.

This is what it would look like:

Two additional two slots could be machined at 30° to either side, making this arrangement a bit more versatile.

If this can get done, the only thing I have not been able to avoid is the milling of the slot/s which seems like a reasonable compromise.

If the brass strip is properly machined/lubricated, it should not get stuck.

Any and all comments welcome.

Thanks in advance,

JHM

Edited By Julius Henry Marx on 14/11/2022 14:59:31

[Graham MeekParticipant @grahammeek88282]

There is a problem with your clamping arrangement in that you cannot clamp the column and the piece of brass. The slot in the Emco column bracket will distort under clamping. Being wider nearest the column and narrower out by the pinch bolt.

To effectively clamp both is asking a lot and any play in the system will defeat the object of the exercise.

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … cannot clamp the column and the piece of brass.

> Being wider nearest the column and narrower out by the pinch bolt.

Yes, I see what you mean.

> To effectively clamp both …

The thing is that the brass strip does not need clamping.

It only needs to help register the position of the milling head with respect to the column as the bolt is being tightened.

Would making the brass strip and the slot as wide (or a wee bit less) as the spot where the pinch bolt tightens make a difference?

In than way, the far border of the strip would just *fit* there and not be subject to force when tightening the bolt but would register the position with reasonable accuracy as it is being tightened.

Thanks in advance,

JHM

[Michael GilliganParticipant @michaelgilligan61133]

A possibly outrageous ‘evolution’ of Gray’s guide-bar arrangement …

Would it be worth adding a linear slide-rail instead ?

Over the last few years, these have come down a lot in price.

No point putting an ebay link here, but there are many to choose from.

MichaelG

[Graham MeekParticipant @grahammeek88282]

Any play, no matter how slight will be magnified due to the distance the spindle is away from the column.

Back in the late 1970's and early 80's I went through a whole host of trials to improve the Emco alignment. The best solution that worked is the one I have shown above.

Michael,

A good suggestion as it would remove the need to machine the column. These linear bearings were not so readily available back in the 1970's, well not cheaply that is. Although we did use plenty of them in my Toolmaking days for pick and place units on robotic tooling.

Regards

Gray,

[JasonBModerator @jasonb]

Best bet would be to do away with the round column and replace with a piece of square sillver steel which would mount on teh diagonal using teh cast "vee" mount on the back of the lathe bed.

Then make a new rear half of the "head clamp" with a vee in the back and a separate cap also with a vee in it. That would easily clamp up true each time.

The problem with any flat strip in a keyway is that you need some clearance for the head to move up and down and as the spindle is about 100mm from the round column and clearance will be magnified about 5 times.

[Brian GParticipant @briang]

I let my subscription lapse when I moved, so cannot check it in the online issues, but I remember reading an article on this subject. IIRC it used a second round bar to locate the column and added a leadscrew and graduated handwheel. Looking at the index I think it will be Rhodes. M. "Milling Head Alignment Guide for the Unimat 3" MEW 124 (April 2007).

Brian G

Edit:  This is the article I remembered, and I found some of the text and a couple of photos published here as a news article

Edited By Brian G on 14/11/2022 18:30:50

[JasonBModerator @jasonb]

That article is on the forum here

Edited By JasonB on 14/11/2022 18:24:30

[Jouke van der VeenParticipant @joukevanderveen72935]

Yes, that is what I meant with the proposals bij Maurice Rhodes.

The modification to the Emco Compact 5 column from Jamie Wood, shown by Graham Meek, is a bit of the same.

Both are nice solutions with (almost) no modifications to the original Emco parts.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

@Gray:

> Any play, no matter how slight will be magnified …

Quite so.

> … host of trials to improve the Emco alignment.

> … best solution that worked …

I'll keep that option in mind if I cannot find something simpler and less costly.

ie: the ~ Ø 12mm / 300mm long vertical bar

@JasonB:

> … any flat strip in a keyway is that you need some clearance for the head …

> … clearance will be magnified about 5 times.

Yes, that is a problem but not as severe as not having a way to register the position back where it was before moving it.

Maybe I could use an arrangement such as the one used to set the angle when the milling head is tilted.

ie: an arrow pointing to a line.

A line maybe 0.5 mm wide could be scribed 1.0mm deep into the column and painted with a suitable colour.

A pointer of sorts would then have to be added to the milling head.

I'd say that this method (pointer meeting line) is just as repeatable as the one used to set the angle when the head is tilted.

After the head is lifted/lowered the bolt would be tightened just enough to keep it from dropping but not enough that it would keep the head from moving if softly knocked to the position indicated by the pointer meeting the line scribed into the column.

Granted, I'd have to look at the back of the milling head but this milling table is very small so it can't be too much trouble.

And even then, I can always scribe the line on the opposite side and avoid the hassle.

If it does not work, I can still try other solutions.

Think it would do?

Thanks in advance,

Best,

JHM

Edited By Julius Henry Marx on 14/11/2022 19:10:09

[Robert ButlerParticipant @robertbutler92161]

Posted by Julius Henry Marx on 14/11/2022 19:06:31:

Think it would do?

Thanks in advance,

Best,

No! not in terms of any meaningful repeatable accuracy. Respectfully suggest you read the postings above.

Robert Butler

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Graham Meek on 14/11/2022 17:07:25:

[…]

Michael,

A good suggestion as it would remove the need to machine the column. These linear bearings were not so readily available back in the 1970's, well not cheaply that is. Although we did use plenty of them in my Toolmaking days for pick and place units on robotic tooling.

Regards

Gray,

.

Thanks for the comment, Gray

Here, borrowed from an ebay listing, is the sort of thing that might suit the Unimat nicely:

.

.

MichaelG.

[JasonBModerator @jasonb]

Posted by Julius Henry Marx on 14/11/2022 19:06:31:

 

A pointer of sorts would then have to be added to the milling head.

I'd say that this method (pointer meeting line) is just as repeatable as the one used to set the angle when the head is tilted.

The markings for setting the head at an angle are really only a rough guide, I certainly never used that to set mine vertical always used a square on the bed against something long in the chuck. So similar on the column would not be very accurate.

If you are just going for markings then the laser and line on the wall will be better as any small error on the wall say 2m away will be many times less at the mill.

Edited By JasonB on 15/11/2022 06:57:48

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

@ChrisLH:

> … had the same problem on my Dore-Westbury …

> … mill a rectangular keyway in the collumn and to provide a captive rectangular key …

Is this the type of key you are referring to?

Thanks in advance.

Best,

JHM

Edited By Julius Henry Marx on 15/11/2022 09:48:43

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … markings … … are really only a rough guide

> … always used a square on the bed against something long …

Yes, I can see that.

I'll look over all the posts again and see what I can do about this.

Thanks for your input.

Best,

JHM

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ady1 on 14/11/2022 09:40:06:

[…]

I also ran into this on the ME site

plus the original patent

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

.

You’re welcome, Ady

MichaelG.

[ChrisLHParticipant @chrislh]

Posted by Julius Henry Marx on 15/11/2022 09:38:55:

Hello:

@ChrisLH:

> … had the same problem on my Dore-Westbury …

> … mill a rectangular keyway in the collumn and to provide a captive rectangular key …

Is this the type of key you are referring to?

Thanks in advance.

Best,

JHM

Edited By Julius Henry Marx on 15/11/2022 09:48:43

Yes, that's it

Chris

[Graham MeekParticipant @grahammeek88282]

Hi Jason,

The square column would be a good fix as regards repeatability but you would loose out on the infinite locations that you get with a round column. In being able to rotate the head about the column axis that is. Of course you would have two easily achievable positions at 90 degrees, and one at 180. There would of course be the loss of being able to mount the milling table to the column using the Emco adapter bracket. Unless of course you make a new bracket as well.

Generally,

Any solution that moves the location point away from the outside diameter of the column, (28 mm or 14 mm R), is going to improve the accuracy. There is a lever ratio of approximately 5:1 present with respect of the vertical spindle centreline to the centreline of the column. Only 0.01 mm of play in any keyway will equate to 0.05 mm movement at the spindle. The less clearance or play present will make the head harder to move up and down.

The slot will without doubt fill with debris, which will soon put paid to any fine tolerances.

If I was looking to repeat my VAD, (Vertical Alignment Device), today I would go down the linear bearing route. Probably a sealed ball bushing and plain hardened shaft, but using the two VAD brackets. This will never wear out and once fitted not give any further trouble.

Regards

Gray,

Edited By Graham Meek on 15/11/2022 12:05:25

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

@Chris:

> Yes, that's it

Right.

I found an exploded diagramme of the tailstock to see the rest of the parts, I cleaned it up a bit for clarity.

Am I correct in assuming that the key is *first* put in place inside the tailstock and then the rest of the barrel assembly is set in place?

Edit: I just now saw your PM, had not received a notification.

I'd appreciate if you could make some time to post a photo/sketch of how you implemented this in the column of your Dore-Westbury mill.

Also, I don't quite understand this:

"Clearance is not a problem if you remember to always push the head to the right (or left) on tightening …"

Thanks in advance.

Best,

JHM

Edited By Julius Henry Marx on 15/11/2022 12:10:24

[ChrisLHParticipant @chrislh]

Posted by Julius Henry Marx on 15/11/2022 12:04:53:

Hello:

@Chris:

> Yes, that's it

Right.

I found an exploded diagramme of the tailstock to see the rest of the parts, I cleaned it up a bit for clarity.

Am I correct in assuming that the key is *first* put in place inside the tailstock and then the rest of the barrel assembly is set in place?

Edit: I just now saw your PM, had not received a notification.

I'd appreciate if you could make some time to post a photo/sketch of how you implemented this in the column of your Dore-Westbury mill.

Also, I don't quite understand this:

"Clearance is not a problem if you remember to always push the head to the right (or left) on tightening …"

Thanks in advance.

Best,

JHM

Edited By Julius Henry Marx on 15/11/2022 12:10:24

Answering the sketch etc. will take a little time but, looking at the D-W machine, it's a bit more complicated than I suggested because, due to the need to lift the considerable weight of the head, there is a coarse screw thread machined in the collumn and a "nut" to engage it.

Regarding "Clearance …..", I was assuming that there is no requirement to raise or lower the machine head whilst cutting drilling, etc. i.e. the head is clamped whenever cutting is taking place. So, although there may be considerable slop between keyway and key, as long as the key is engaging the same side of the keyway every time the clamp is activated, alignment will be maintained. This assumes,of course, that the keyway is machined parallel to the axis of the collumn, etc.

[Julius Henry MarxParticipant @juliushenrymarx92355]

 

Hello:

> … the sketch etc. will take a little time …

Don't worry.

I can probably manage as it is just a column and the clamp. (see photos in posts)

> … assuming that there is no requirement to raise or lower the machine head whilst …

Quite right, no such requirement.

Actually, the head cannot be moved while milling, at least in its original OEM configuration.

The quill does have a lever-type arrangement with ~ 25mm travel which enables it to be used as a drill press.

To move the quill downwards while milling, a fine-feed attachment with a dial and a worm gear is used.

It works in conjunction with the lever action gear, allowing a bit over 0.10mm (four thousands) downward travel per each turn of the dial, with the same ~25mm travel.

> … as long as the key is engaging the same side of the keyway …

> … alignment will be maintained.

Right, I see it now.

Thank you very much for your input.

Best,

JHM

Edited By Julius Henry Marx on 15/11/2022 16:19:32

[ChrisLHParticipant @chrislh]

Hello Julius,

I've just mugged up on posting photos so just for fun I'll complete the exercise. Top picture shows the raising arrangement in its normal state. The top disc with tommy bar holes is the "nut" The thinner disc below it is the "key". In the bottom photo the "nut" has been wound up the collum to give an end view of the Myford type key which engages the coarse screwthread. The "key" which engages the vertical keyway (which is just visible on the RH Side) is just a thick plate profiled with a tab projecting inwards from the bore. The "key" is normally prevented from rotating by a short dowel into the casting below. The dowel can be removed should the need arise to rotate the collumn.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … so just for fun I'll complete the exercise.

Yes, it took me a while to figure out how to post photos.

So thank you for taking the time to do this. 8^)

I expect that it will be much simpler to get this done on my Unimat's column.

The real trick will be to make the key (a smallish thing), almost exactly like the one used on the Myford and fortunately not as small.

Once again, thank you for your input.

Best,

JHM

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