Member postings for Graham Meek

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Regards

Gray,

Hi Jason,

I can re-iterate the flexibility of the Hobby machine. My Emco FB2 would always read out in the Y-Axis direction across the table. This is something other users have noticed. We are only talking a total 0.03 mm over 150 mm which meant the Column was leaning to the rear of the machine.

However when extending the head to the top of the Z-Axis travel the reading then became zero-zero in the same direction. My reasoning behind this was that as the Head moved up the Column. The overhanging weight of the Head was inducing a bending moment in the Column.

As an exercise in futility I shimmed the Head to to get it correct, down close to the table. Putting the Head at its extreme Z position. This showed the same 0.03 mm error but in the opposite direction, (Column leaning towards the front). Which was what I would expect.

Clearly Emco had worked this out in the design stage and compensated for it in manufacture. The bottom line is that for the money we are not going to get Jig-borer precision and a compromise needs to be made. Given the work I had completed on this machine both privately and commercially this inaccuracy never once let me down. It is after all only 0.01 mm over the width of a 50 mm shell mill, which is probably being deflected by this amount due to the cutting forces.

Regards

Gray,

Having the quill extended moves the clocking point radius further away from the point of rotation of the Milling head. With a constant swing radius of the clock you end up with a pair of triangles. The "Opposite" sides (clocking radius), are common. The "Adjacent" is longer with the Quill extended as well as the "Hypotenuse" Thus when compared to the Quill "fully in" the angle between the Adjacent and Hypotenuse will be greater in this instance. Than when compared to fully, or extended.

Experience tells me the fully extended position is going to be more finicky to set because of the smaller angle.

The other thing is, and it again boils down to triangles. The top of the Quill touching the Quill housing bore top right while the bottom of the Quill touches bottom left due to the Quill Lock.

The clearance between the quill and the housing will have less effect when the Quill is fully home than when the Quill is extended. If 0.025 mm is spread over 150 mm the angular difference is going to be less than 0.025 mm spread over 50 mm. (please note this is an example and not a particular case).

It is however less than I would expect on something "like repeat like" a Bridgeport quill. The "Limits and Fits" for a "Precision Location" H7/g6 gives a total clearance for an 80 mm diameter quill to be 0.059 mm. One "fit" better at H7/h6 will only reduce this total clearance to 0.049 mm. Transition fits would reduce the clearance still further, but the spring required to return the quill would need to be stronger, making the machine less sensitive. Plus as the accuracy of "fits" gets better, so the costs go out of the window. No doubt this is why Jig borers have exceptionally long Quills.

Regards

Gray,

Whilst the theory may be good, introducing the tapered component also introduces other errors. If the taper is not dead square to the face in contact with the table. This will be a source of error as an elliptical path will be shown straight away. Adjusting the Head to suit this condition will give an error on a true vertical.

I am also not keen on the amount of extension being shown on the Quill. The Quill might well show two different conditions as regards vertical due to the amount of Quill engagement in the Head casting.

I don't think you can beat the clock on the table, or a known parallel, but again with the minimum of Quill extension.

Regards

Gray,

Thank you all for your kind endorsements of my work. This project has been a test for man and machines. While the machines handled the work with no trouble. I have found this project has taken me a long time to achieve.

I was fortunate enough to call GHT my friend and visited him many times at Milton Grange. I owe a lot of my skills to his writings and his meticulous approach to planning his projects. He was a fount of knowledge when it came to engineering, and his woodworking skills with mortice and tenon joints would put many a toolmaker to shame.

As regards a volume II I regret to say that this is out of my control. Chris Deith was the instigator of the first volume, which came totally out of the blue when he rang me one day at work with the suggestion of a book. That was well over 13 years ago now and approximately 50 articles ago. I suspect with his passing that will be the end of any future volumes.

Regards

Gray,

Edited By Graham Meek on 30/09/2023 16:39:17

As is usual lately I have forgotten to add a photograph of the component parts of the feed attachment.

Regards

Gray,

I have just completed this revised table feed attachment. It was designed with a view to the FF 230 mill requiring no modifications in order to fit the unit. It simly bolts on where the original feedscrew bearing plate fitted.

I had some help from John Slater in the form of a small PWM board. The control and "ON-OFF" for the PWM can be seen below the motor housing.

The two knobs on the top of the unit control the direction of travel, (nearest the handwheel), and the clutch to engage the drive to the table.

Not only is there a variable drive through the PWM, but the Proxxon NG 2e Power supply can also provide additional variations. The table is really going some when the both controls are on maximum. As yet I have not had time to calculate the exact top feed rate.

Regards

Gray,

Hi Jason,

The mill above is used mainly for milling while the one below is intended for co-ordinate work and it is this machine that I was intending to fit the DRO to.

I was going to add this picture today on the Proxxon post, as I have just finished the new table feed attachment.

Regards

Gray,

Hi Pete,

Thanks for taking time out to post your reply. I was un-aware that the systems now use a fairly common number of signal types.

Unfortunately there is no room inside the slides for the reader even at 10 x 12 m section. Space is that tight that it needs the backlash adjusting screw on the Y-Axis feedscrew to be backed off, in order to remove the cross slide assembly. The feednut of which completely fills the cast in cavity.

Thus any DRO will have to be mounted externally and the smaller it is the better. The only other alternative is to fit two waterproof Digital Scales. Although this will not be small by comparison. This was done by the original designers of the Proxxon Mill, the Sakai Special Camera company. I have seen a picture of this set-up some years ago, but have been unable to locate that on the web recently. It was at the time sold as a kit.

Thus at the moment I am undecided as to which way to go.

Once again thanks for your input, it is much appreciated.

Regards

Gray,

Thanks Ian P & Jason,

I recall seeing this post some time back. Unfortunately it is beyond me as regards the electronics. Plus the read head will still be too large. I have found an M-DRO Mini Head. which has a 10 x 12 mm section, but the cost of these will make the project impossible.

Thanks for taking the time out to look,

Regards

Gray,

Hi Jason,

I have been pursuing this avenue but have struggled to find a small reading head. I have seen one in a YouTube video which is about 10 mm square. I have had no luck with a reply from the poster of the video.

I would be grateful for information, if you know of any such reader. Also the readout to go with such a system.

Regards

Gray,

All my equipment and designs have been made without DRO's. I have worked for nearly 40+ years as a toolmaker using countless types of DRO. They are not a panacea to more accurate work. One Boss thought fitting a DRO to a clapped out Mill was a means of giving that machine a new life. Unfortunately the geometry of the slideways were not up to the accuracy that the DRO could obtain on a more serviceable machine.

I am not anti-DRO, but I do find it easier and quicker to obtain a position using a dial rather than a DRO, which flickers between one digit and another. Resolution of the DRO is a big factor to accuracy. The better the resolution the dearer will be the DRO package.

While it would be handy having one on my current mill due to the 1.5 mm pitch feedscrews. The diminuitive size of the Proxxon mill makes it hard to find a system which does not look like the mill is the add-on, and not the DRO.

Regards

Gray,

Hi Dave,

Taking us a little of post, the word "breakdown" was never used in the Radiotherapy Centre. When the machines went wrong they were reported as "Fallen Over". When I first heard the expression I had visions of the Radio Therapy machine in the bunker lay on its side.

A far cry from my days with Xerox.

Regards

Gray,

Hi Dave,

The ABC button showed "Enable SCYAT", which would leave one to assume it was disabled. However I enabled it and then disabled it, then hey presto it now works properly.

Thanks for that, but I expect the reduction in stress levels will be short lived.

Regards

Gray,

Hi Michael,

As usual with this site one learns something new every day, and I do love plums.

The word gage sits in my brain from the days working at Rank-Xerox. The build sheets from the USA had to be re-written in UK English to suit the assembly staff. Gage and Color were frequent alterations and it was this job that put me off office work.

Regards

Gray,

Hi Dave,

Thanks for the info, but thus far I have been unable to dis-arm the spell checker. I will just have to wait until the changeover.

Regards

Gray,

While we are on the subject of spelling, grammar and the origins of words.

This site accepts catalog but not catalogue.

It likes center but not centre.

While I know I make mistakes with my spelling, all the right letters but not necessarily in the right order. This does little to ease my frustration at getting the words wrong. Especially when the computer does not recognise / recognize, (there's another), the right spelling.

Funnily enough it will accept color and colour, gage it won't, but gauge it will.

I had thought we are on American spelling and not English, but the last example above blows that out of the water. Yet with all the in depth discussions above, I have not seen anyone else point this out during the post.

Moderators please, for my sanity can you sort this one out.

Regards

Gray,

Hi Pete,

You make a valid point and one which led me to choose ABS for my collet rack. This plastic being one of the lowest for absorbing moisture, and commonly available. The old RS catalogues here in UK used to have a very good page entitled the "Properties of Engineering Plastics". This told you almost everything you need to know about plastics. I have not looked to see if this page is available in their on-line catalogue. If it is then maybe someone could provide a link?

Regards

Gray,

+1

The boxed Emco ESX 25 collet set I had suffered from this problem. The Plywood rack was replaced with an ABS one and the problem went away.

As regards Wooden Engineers tool cabinets. While I used my cabinet in industry for the best part of 40 years. corrosion was never a problem. When I retired and used it in my home workshop, corrosion started to appear on certain items.

Despite having a dehumidifier in the workshop it persisted. The cause I put down to the temperature swings in the workshop. Which did not occur in the old industrial setting. While the air in the home workshop heats up quite readily the items in an insulated cabinet do not.

Any moisture present in the atmosphere of the workshop, (breath is a big source), will find its way into the cabinet and condense out on the much colder items.

Changing to a steel version of the Engineers cabinet has solved the problem. The old tool cabinet was snapped up at an Antiques fare, and the price paid more than covered the cost of the new tool cabinet.

Regards

Gray,

And there I was thinking the plural of radius was rads, as distinct from RADS.

Regards

Gray,

I knew I had a shot somewhere.

Gray,