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Triangular Gib Key For Unimat Vertical Column

 

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
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I've been interested in his MetalMaster for years, but wasn't (probably still am not) machinist enough to make it work. I'd be interested in photos and discussion about what and how you've done this.?

Bill in OKC?

William R. Meyers, MSgt, USAF(Ret.)

Aphorisms to live by:
Good judgement comes from experience. Experience comes from bad judgement.?
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On Tuesday, November 26, 2024 at 09:06:50 PM CST, OldToolmaker via groups.io <old_toolmaker@...> wrote:


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
 

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:
?
?... looked at the MetalMaster too ...
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.
... the triangular gib is a neat idea.
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:
The key was at the heart of the design's success for, when moved up or down the main column (by a jacking screw) and re-clamped, the far end of the bed did not deviate by more than .001" to .002" in radial alignment - a remarkable achievement for the key was operating (at that radius) at a 'disadvantage' of about 20 to 1. Not only was the clamp highly effective but, when released, the two components were able to slide with perfect smoothness.
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'.
?
While looking for a solution to this problem, I once found a video of a chap in the UK taking on a similar modification by making a rectangular slot where a snub nosed machine screw would run the length of the milling column.
?
In my estimate, it will put you in the ballpark, but I do not think it provides the accuracy the triangular gib design can provide.
If interested, look for a YouTube video from a place called "Many lathes" or something such.
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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.
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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

triangular_gib.jpg

 

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 .
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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

column_section.jpg

 

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!
 

On Wed, Nov 27, 2024 at 02:42 PM, Peter Brooks wrote:
Interesting that the v-groove is asymmetric.
?
That's the way it works - tightening the adjusting screws takes up all the clearances between the column, the key and the machine head (of whatever kind), ensuring accurate alignment every time. When I look at the smallish mill I could try this on I realise the column is a tube, not a solid bar, and cutting a decent size groove would go most of the way through the tube wall. Similarly the milling head casting doesn't have enough meat in it, especially for a lump of cast iron. Modern machines aren't made with the generous castings and columns that used to be common.
 

I have an Emco FB-2 mill.? I could try to machine a triangular gib.? It is very possible that I might not succeed.
I would like to remind members of my previous message:
Feb 22???
See the attached photo.? So far, this is the best that I have managed.? Building something like this with common parts, I save myself from my own mistakes and can redo things if incorrect.
Now if you really want a column and can spend $181, buy this.?
https://www.sherline.com/product/30503053-vertical-milling-column/#description
I have one mounted on a Sherline base, and I think that the column exceeds whatever you can do with Unimat parts.? Now you will have to figure out how to mount it on a plain surface and how adapt it for a Unimat head.? If you position it alongside the middle of the Uni bed, you have the possibility of longer travel.

Unimat mill.jpg

 

Hello:
?
On Wed, Nov 27, 2024 at 11:42 AM, Peter Brooks wrote:
... seen the youtube video ...
Heavy duty machining ...
Indeed ...
?
It is the closest I have seen to solving the problem with the Unimat milling columns.
But if after all the trouble of getting it done you still have to tram the head after moving it, the problem is not solved.
Just ameliorated.
?
I have the Unimat mill all set up with a new motor+PWM control, a new set of bushings and a piece of thick felt pad soaked in light oil which I lodged in the void between the upper and lower bushings to keep things going smoothly as time goes by.
(see attached photos)
?
But as I am still in the middle of acquiring the ER stuff, I have only used it as a drillpress.
And losing the head position as you raise or lower the head it is a nuisance.
?
What Urwick's fantastic triangular gib invention clearly shows is that the problem at hand lies in the key itself.
But I think that getting the same thing done on the Unimat columns is not feasible.
The diameter of the U3 column is just 28mm and the headstock adapter (where the quill holder is articulated) could not have been made with less material, it looks skimpy when compared to the one made for the older Unimats.
?
Like with some other parts of the U3, Emco really made an effort there.? 8^¡ã
?
Maybe the solution to the problem (like for Urwick) lies in the design of the key?
eg: instead of a snubbed bolt (a ? 8mm cylinder) use a long triangular key where two same length sides center the part.
(see attached photo)
?
Best,
?
JHM

u3_milling_1.jpg
felt_void.jpg
u3_hsa.jpg
tailstock_key.jpg

 

¿ªÔÆÌåÓý

Hi Gang:

A key on the 28mm column is still very close to the center of the shaft. A 1?m error would be a 10?m error at the spindle. Also the fit of the triangular key is critical.

What if you added a stiff arm to the head and a fixed point on the bench to keep the head from rotating? The arm could be twice the spindle distance from the column, so the error would be divided in half.

Carl.
 

A simpler solution could be a symmetrical v-groove in the column and a matching pointy-ended bolt (there¡¯s probably a better name for that!) to fit it.
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Would it have the holding power? Maybe it could be for location purposes only, with the clamping bolt(s) then being nipped up in the usual way.
?
Would it damage the column? I guess the pointy-ended bolt should be softer than the column.
?
Maybe I¡¯m missing something here but I find that I nearly always have to alter the position of the U3 milling head, rotating it before starting to suit the work, so ideally I would have a selection of v-grooves to provide different options of angle to the bed. That could be asking too much of the column.
?
(My drill press suffers from the same issue - it doesn¡¯t have anything to keep the table aligned as you raise or lower it - so this is a subject that interests me from several angles!)
 

Hello:
?
On Thu, Nov 28, 2024 at 04:18 PM, Peter Brooks wrote:
... a symmetrical v-groove in the column...
That's what I was referring to when I suggested "... a long triangular key where two same length sides center the part."
The thing that looks like a 'T', attached photo in my last post.
The pix is not too clear.
... pointy-ended bolt ...
I don't think a bolt with a pointed end will do enough to center the head consistently.
... have the holding power?
A longish steel/cast iron key probably would, but I'd leave the holding to the clamp.
... damage the column?
No, don't think so. Because of softer metal? Wider surface of contact?
... a selection of v-grooves to provide different options ...
Yes, I think that three grooves (0¡ã, 90¡ã and 270¡ã) would be optimal.
?
Best,
?
JHM
 

Hello:
?
On Thu, Nov 28, 2024 at 05:41 PM, Julius Henry Marx quotes himself:
... three grooves (0¡ã, 90¡ã and 270¡ã) would be optimal.
I neglected to mention that while it would indeed be optimal, it is a lot more work at the time to grind the grrove in the column.
?
One groove only has to be right with respect to the bolted-on position of the column to define the centre position of the head.
The other two also have to be and hopefully end up being correct with respect to each other.
?
Best,
?
JHM
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Hello:
?
On Thu, Nov 28, 2024 at 10:55 AM, Carl wrote:

?

... key on the 28mm column is still very close ...

... 1?m error would be a 10?m error at the spindle.

Indeed ...
Had not thought of that, my lack of experience clearly showing.

... a stiff arm to the head and a fixed point on the bench ...

I have seen some milling heads which seem to be like what you describe.
A long rod which served as a guide to keep the head from moving when it was raised or lowered.
?
There is an article from MEW for something like that.
Only a very small photo and the author's description which seems rather complex to me.
?
But I found a properly sized image elsewhere which reveals a really interesting design.
See attached photograph*.
* courtesy of model-engineer.co.uk
?
Then there's one with a feed screw, apparently well built and with a ~US$200+ tag, shipping not included.
?
Thanks for your insight.
?
Best,
?
JHM

m_head_guide.jpg

 

Peter, I think you bring up a good point. I especially like your idea of having a column with vertical v grooves and mating ¡° V ¡° set screw or point of some kind.
Dick
--
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
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¿ªÔÆÌåÓý

Hi Gang:

What about the run-out of the cone on the clamping screw?

Carl.

On 11/28/2024 9:51 PM, OldToolmaker via groups.io wrote:

Peter, I think you bring up a good point. I especially like your idea of having a column with vertical v grooves and mating ¡° V ¡° set screw or point of some kind.
Dick
--
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
 

The important feature of the triangular key is that, when clamped, the wider flat face (the hypotenuse of the triangle) is wedged against the corresponding faces of both the column and head giving repeatable alignment. The design is very rigid compared to a bar set parallel to the column, where, apart from the flexibility of the rod, the bush on the rod would have to have some clearance to slide - although a pinch clamp would eliminate that source of error.
?
As for needing to set the head at different positions at times, that is another matter, but not easy to solve as a modification to an existing machine. For example the whole column could rotate on its base, or a collar could be fitted for the alignment device, and the head clamped around that, free to rotate when needed.
?
The option of multiple grooves in the column, or in the head, would call for a removable key, but that is no big problem. By having grooves in both, but different numbers, would allow a good range positions in a Vernier fashion, so a combination of five and six grooves would give 30 positions equally spaced around the column, but this is starting to get complicated.
 

Peter,
Isn't it the action of the key on the shaft to keep the head position central to the axis of the lathe, then you have the crossslide table able to position to any other angles?
?
Phill
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Personally, I find (on the U3) that the mill at 90 degrees to the bed isn't a good place, I generally prefer to get the mill spindle somewhere around central between the rails of the bed - which requires a degree of rotation.
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Horses for courses though, no hard and fast rule!? IMHO I think a range of grooves would be handy.
 

On Fri, Nov 29, 2024 at 03:26 AM, Carl wrote:
What about the run-out of the cone on the clamping screw?
Wouldn't the same screw in the same threaded hole mate at an identical place every time? ( I honestly don't know!? :-)
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The accuracy of the run of the groove might be a more critical factor if we are talking about very small deviations.
?
Anyway...
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On Fri, Nov 29, 2024 at 05:24 AM, Keith S. Angus wrote:
For example the whole column could rotate on its base...
A new base collar opens up a whole load more possibilities... if the bench was freestanding (or at least had a void underneath it) then the column could descend through the bench. It might much be easier to build a system with the triangular gib key into a new base collar, rather than into an existing milling head. The milling head could then be rotated to wherever you wanted it, but the key in the base collar would ensure accurate up/down alignment (and only one groove required).
?
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