Member postings for John McNamara

Hi Raymond Anderson

My VDF was made by Heidenreich and Harbeck

In the 60's a group of German machine builders teamed up, they shared common parts and technology while maintaining their identity as separate companies. ​VDF Bohringer was also part of the group.

As you might guess the machine did not look like the picture when I got it. Many happy hours months! have been spent refurbishing it. It is powerful and accurate. The finish is 2 pack epoxy machinery paint from Dulux closely matched to the original colour.

Regards
John

Hi Rainbows

My lathe a German VDF RO 80 uses an NN type double row cylindrical roller bearing with a tapered inner ring for adjustment next to the chuck. They are very expensive, the cost of a small lathe for one bearing. The system works very well Recently I was able to find a new one in an auction job lot (It was a bearing supplier) I am still too scared to strip the head down to fit it! The lathe is from the 70's.

Plain tapered roller bearings are a fraction of the cost of an NN type. many high quality lathes use them.

One thing to consider when selecting bearings is the maximum speed for a given size, Tapered roller bearings size for size have lower maximum speed ratings than angular contact ball bearing sets, the reason they are used in CNC machining centre spindles. on the other hand tapered rollers will carry higher loads. Lubrication plays an important role keeping bearings cool. grease is fine at lower speeds however churning it causes heat build up, oil lubrication allows for higher speeds, after that oil mist lubrication ceramic balls and other exotic systems are used.

Given a choice I would go for oil lubrication.

The one thing I miss with my lathe is higher speeds, I would really like a small lathe that could do at least 3000 rpm ideal for turning small parts. Oh and I need more room to house it.

Smaller diameter bearings in most cases have higher speed ratings and cost less.

The major bearing manufacturers all have excellent downloadable application manuals; worth reading.

Regards
John

Edited By John McNamara on 06/05/2016 14:59:55

Hi Rainbows

The problem with a separate shaft collar is getting it sit perfectly on the shaft, even with a press fit there is a chance it will be slightly canted, if it is there will be a cam action forcing the spindle to move in and out as it rotates. It behaves like a micro version of a swash plate, often used in car aircon compressors.

The advantage of turning the spindle and its flange in one setting is the greater accuracy obtained. Unless of course the lathe it is turned on has the same problem, in that case that lathes error would be replicated.

The same laws apply to the nut and lock nut used to set the preload on the bearings against the shoulder, for better quality machines sometimes these nuts are turned or more likely ground while mounted on the spindle as a set.

Maybe you can find a local model engineer with a larger lathe to make the spindle.

Regards
John

Hi Rainbows

Some variations on your theme here.....
**LINK**

You really do need to keep the swarf out there are dozens of inexpensive mechanical seals available.

It appears your main shaft is not stepped? Usually there is a step that provides positive location and provides an opposing face to preload the tapered roller bearings.

Regards
John

Overuse?

Hi Rainbows

Yes this has been done in an attempt to improve the accuracy of the spindle reducing any radial forces on it.
The ball bearing and its inner driving collar that supports the drive pulley is supported by the head stock frame, the spindle is driven by that via splines or a key. in a way a spindle within a spindle.

The real spindle is supported in its own separate bearings, the only touching point is the drive key.

I am sure there are other members that may remember other companies that did this.

From Memory the German company VDF did this with one of their lathes? They also offered plain bearings for some of their lathes the objective being a finer surface finish. Even super precision bearings create some bearing noise that may affect the work finish. The Diamond turning lathes used to turn computer disks do not use ball bearings, Air or magnetic levitation bearings are used for mirror finish required.

Regards
John

Hi Sam My memory needed jogging too.

If you Google the following 3 searches....

steel stress strain graph images
steel creep graph images
steel deflection graph images

You will see various representations of the stress strain graph for Steel. While strain hardening does occur it is past the point of no return, there is a permanent change in the dimension of the steel part.

Up to the yield strength knee in the graph the material under load will return to its original size, obeying Hooks law.

Long term there is also creep, particularly if the load is near the yield point. Normally in a design a safety factor is applied depending on the use. Creep will be less with lighter loading factors. Where human life is involved a factor of 2 even 3 or more is common.

A steel part may pass the tests for a specific load and still not be satisfactory if it bends (Deflects) more than a particular design can tolerate. For high accuracy machinery Deflection is the main concern of the designer. A lathe bed is a good example, clearly there is no risk of it failing due to the load applied by the cutting tool and saddle. The designer made it massive to reduce deflection.

Regards
John

My solution is two pieces of 25 x 12 x 130mm steel bar with threaded hole set in the centre of one end forming a lever nut, round of the sharp edges to protect your hands.

Half inch bolts and a washers set from underneath the table completes the vice clamps. No more looking for a clamp. For an application like this a Whitworth thread is stronger than M12. due to the coarser thread

I just loosen the clamp levers and vice and all drag the vice into position.

Much stronger than a G clamp and no spanner needed.

Only a few minutes to make. cost from the scrap bin....nil.

Regards
John

Edited By John McNamara on 01/04/2016 08:02:19

Great Idea!

There is a bit of a risk that it might leave a mark in the bed way over time? Maybe a solution would be to machine a flat on the round dowels to spread the load. They would self align. I would use epoxy or Loctite to make the aligned angle permanent.

Regards
John

When contemplating how to process a job accuracy beyond what is needed can be a great time waster. does the job really need to position the hole with pinpoint accuracy or will within maybe .0015" to .002" do? achievable on a good day if my glasses are clean.

I can set a drill in key less chuck on the pillar drill in a few seconds, Maybe a spotting drill first if needed, Position the work in vice and set the centre pop on the work under the drill in less time than it takes to write this. If needed In goes a chamfer cutter to remove the sharp edges around the hole flip the work do the same on the other side and the job is done.

Alternatively do it in the vertical mill this will require centre finding the punch mark locating x and y, the big table is heavy and there will be a fair amount of winding. then Fitting a drill chuck in quill and tightening up the the draw bar.... as we all know the wrong tool is always in the draw bar... then finally drilling the hole.

Yes with care I can get better accuracy maybe one or two thousandths of an inch better, The purists will claim they can do .0001" (In their dreams) unless they have a jig borer in temperature controlled room! yeah.

Time waits for no one.

Regards
John

Hi Daniel

The Drill press looks a little like my Rexon a Taiwanese made drill I have had for maybe 20 years, It has given good service within its capabilities. Yes I have scraped the swivel bearing face to make the table a true right angle. With smaller drills I like it for the light and sensitive touch. For heavier work I use the milling machine but the quill is a lot heavier and less sensitive.

There will be some deflection of your drill table with heavier drills say over 10mm particularly if you bear down on them trying to push them into a piece of tough steel or grabby Brass. The drilling pressure can be significantly eased by drilling a smaller pilot hole first, to drill through 25mm steel you will need to peck drill to clear the chips or you may get a jam. It is important that drills are kept sharp. The smaller drill will also find the centre of your centre punch marks more easily, the web of a 12mm drill may miss unless you punch heavily. So the smaller drill is acting as a spotting drill as well, it should result in more accurate work.

Regards
John

From Steve Withnell "Sky Broadband connection with a 2GB usage limit"

Maybe time to switch your service provider?

I agree with Paul Lousick, A hot bend is far less likely to cause stress fracturing that is often created when cold bending steel to a sharp corner.

Dollar for Dollar or Pound Pound in the UK a pallet truck is to me one of the most useful ways to move things around, It will not work on soft surfaces so you will also need a few sheets of strong plywood and a number of chocks to create a level surface if moving over say grass. Needless to say if there is more than a mild slope, it is better to use a professional machinery mover.

The fact that it can lift maybe 150mm is a great advantage. However when moving a pallet you should only lift it the minimum needed to clear the floor. This assures the there is little risk of tipping.

They are available fairly cheaply.

Make sure you have a place to park it maybe under the end of a bench if available is a good place the lifting feet are the problem, you have to slide them under something.

I have a storeroom that abuts a driveway that is packed so tight I can only just close the roller door! there is no passage way inside, It is stacked to the roof. with all the goods stored on pallets and shelves made to fit on pallets. It only takes a couple of minutes to drag out a few pallets to access the ones at the back the pallet truck makes it so easy. it is left parked under one of the pallets with just enough room to shut the door. as long as the floor is flat you can move a ton quiet easily.

Regards
John

An alternative.....

Cut a step in the shaft making it a couple of mm oversize, a light press fit will do, it will be tightened up by peening.

Then bore the plate to fit and put a 1.5mm 45 deg chamfer on one side of the bored hole.

Press on the plate then carefully ball peen the edge of the shaft into the chamfer, with a small hammer and light taps to maintain control. It projects 2mm, giving you metal to work with.

I would do this in the lathe with the plate resting against the face of the chuck jaws, the main thing is to keep it from canting. Tidy up face of the rest of the projection in the lathe. if looks are important.

If you peened it well you will only see a fine line.
It will be a very strong joint

Regards
John

Dry Ice?

It sublimes at -78.5 deg C

**LINK**

You should be able to get it.

Regards
John

Hi A while back I made up a spreadsheet to calculate the required angles for dividing. using a Vertex type Rotary Table.

Its an excel spreadsheet. Enter a number to divide and It will only show the needed settings for that number.
Handy if you dont have dividing plates

Best to print it out and mark the rows off as you do them.

(Always turn the handle one way, if you overshoot reverse well back then try stopping on the exact mark again to avoid backlash)

Link

**LINK**

Regards
John

Hi Alan

There is something very satisfying about heavy Iron,
You may be a bit limited with top speed for the vertical head using small cutters. but you will never run out of power with bigger cutters judging by the paint it has had an easy life.

I googled          victoria U2 Milling machine

https://www.google.com.au/search?q=victoria+U2+Milling+machine&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjgmLK619HLAhVCqqYKHV75D_wQ_AUICCgC&biw=852&bih=489

Worth a browse

A good find.

Regards
John

Edited By John McNamara on 21/03/2016 11:35:00

Many computer power supplies have leads wrapped around ferrite rings, they are used for reducing electrical noise

If you can get hold of an old one try pulling it apart You may find a ring that will work

Regards
John

Gee.....

The Magazine cannot be expected to meet the needs and wishes of all the readers all the time. Sometimes it will miss the mark for you while others will be very pleased. I for one have almost every MEW (I am missing the first 4), since I found it at WH Smiths while visiting England for work. And yes they are fun to review back in time, quite enjoyable in fact. To me it is the whole that matters, not individual copies. On balance I think the Magazine represents very good value over the year. I will continue to subscribe.

I should also chide myself for not contributing an article or two! My excuse is time as I am still working. Not that great an excuse. I will seek to change that. It is such a great platform to share Ideas on. The soul of the magazine is in the gifted hands of the readers and their work, (They even get paid for the articles). The publisher reward is paid advertising my guess is the budget is tight, It appears to be a fair deal to me.

Regards
John

Edited By John McNamara on 15/03/2016 06:07:00