Member postings for Bob Mc

Hi Neil...

you beat me to it...!

Oh well...here goes...!

Yes an accelerating object such as a rocket has thrust from its engines, the occupants are thrust back in their seats which is opposite the acceleration direction... similarly an object on the earths surface is pushed down by gravity and the reaction force of the ground keeps it in place.

For those who may not know of the argument of dispelling centrifugal force, it seems to have arisen as far as I am aware because of the famous (late) Eric Laithwaite lecture in which he stated that the academics will not even say the word 'centrifugal' because they say 'it doesn't exist'...the televised lecture was 'expunged'....

My argument is that there must be two forces in place in order to keep an orbiting object at its distance from the centre of rotation just as the Earth's (centrifugal/centripetal) force due to rotation is kept in orbit because of the Suns gravitational pull.

In fact 'Centripetal' actually means the force directed towards the centre of rotation, so if we have the Earth with the Suns pull + this 'Centripetal' pull we will soon be toast.. and if you look up Centripetal in Wikipedia as far as I can make out this is exactly stated in Wikipedia.. ie that there are two pulls in the same direction....correct me if I am wrong.

So I stand by my original post, that there must be two forces equal and opposite on an object in orbit, whether it be a gravitational force or the force of mechanical restraint...this force must be towards the centre of rotation, whereas a 'Centrifugal' force would be away from the centre and is the reaction to the centripetal force.

....Now my brain hurts...!

Hi Tim...

It seems that the topic changed from 'How does solder stick' to the physics of gravitational and rotational forces with Dave's (SOD) and others with myself included musings, you are right to bring the thread back to its original theme and I think you are correct in what you say about the 'wetting' idea.

Perhaps my last post should have started another thread but it was in answer to pgk pgk's post...for those who may not know of the argument that only centripetal forces exist I should point out that this is the accepted formal view of physics which I believe was challenged originally by the late Eric Laithwaite who's theories were later discounted by the academics and his televised lecture was 'expunged'.. I think the word was.

I am not going to elaborate on this further as it starts to get quite involved and is not what the topic intended.

rgds...Bob...

pgk pgk says...

One can then illogically extrapolate that the failure to find a subatomic particle to call the graviton (one of the hopes for the higgs boson/field) is that there is no such thing - there is no gravity any more than there is a centrifugal force (it's centripedal).

I'm only a simple engineer and will stand corrected, but it seems to me that in order for an object to stay in the same place on a rotating plane there must be two forces at work, centripetal and a restraining force , as Mr Newton said that for every force there is an equal and opposite force... What do we call this restraining force..?

Bob...

I use one of those diamond grinding wheels on my cutter grinder (pic below) but don't use it for sharpening hss cutters .. they are only intended for carbide.

it clogs up and the wheel can't be dressed again...unless someone knows differently..!

...Bob...

Hi Peter...

I have been thinking about making a wire draw DRO for the y axis on my lathe, as you say commercial units are available but are rather expensive... the rotary encoders on ebay would be suitable if a wire draw mechanism was available with it .

Using the Arduino for the control and readout is the easy part..and after much deliberation as to how to fit some sort of wire draw retractable mechanism it occurred to me that something like a tape measure or retractable dog lead might be the answer but they are not exactly what is required.

I came across a possible solution when I saw for sale a retractable key ring, this is fairly small and has a reasonably good retracting pull, the torque needed for the rotary encoder is very light and the only consideration would be to fit the mechanism to the encoder and to the machine...and it is very cheap.

I haven't got round to doing the job yet...but pictures below show the parts; for my lathe I only need a readout for the cross slide I have bought a normal dro from Chester Machine tools for this which sits in line with the bed and is just where the line of sight with the work is.... anyway see pics below...hope this might be of use...

rgds...Bob...

The x axis readout below.

Rotary encoder.

Retractable keyring .

Oh...

should have added .... Welcome to forum Kevin..

rgds..Bob.

Hope this fits in with this thread...

John McNamara says... Greetings from Melbourne OZ

An old mill to a tool grinder. That would be interesting.

I made this tool/cutter grinder using an old flatbed lathe and some other bits I had, the spindle head is from a discarded contact lens making machine and can be moved vertically with the very coarse threaded pillar...similar to the Quorn setup.

The toolpost can be swiveled in x & y axis and rotated about a vertical axis, the whole toolpost assembly is carried on the bed topslide. There is a DTI on the bed to set the amount of grinding so that equal amounts are taken taken off the cutter or drill.

The cutter holder is based on Harold Halls design in his Cutter grinding book and is easily set up for four facet grinding.

Rgds...Bob.

Been messing about with Mogens Kildes Double diagonal engine...

Have made most of it in perspex as I hope to use it as a template for cutting the steel frames & cylinders, also trying my idea of wedge shaped cross head guides which saves quite an amount of metal and fixing and the cylinders are fed compressed air through the frames instead of external pipes...hopefully.

Thanks Neil...

You are making me think now...!

..Bob..

During a tidy up session I found the jars of brass turnings I had saved over a number of years...and I have quite a lot of brass bits & bobs & offcuts ... was hoping to melt them down and cast something but it seems to me quite a dangerous and involved process... do the scrappers take brass turnings...?

Thanks Emgee...Thanks Neil..

How do I get to the 'Introducing the Arduino' article as mentioned in MEW 273 ?

Thanks ...Bob.

When stuffing a chicken...you don't say ' I am pulling me Giblets out ' with a hard G .

Hi Stew..

yes I saw that at Macc Models...was very tempted, I might be stating the obvious now but have you tried the Stockport Modellers... Dave Wagget email [email protected]

Bob.

Hi Ron, thanks for your message..

I have looked at the suppliers website but they don't actually give any information about the blade or holder other than give its overall dimensions, I suppose I should contact them and ask but I have now made a fitting for my toolpost which puts it in the right orientation and I don't hold much hope out for getting a meaningful response from the supplier as I contacted them previously about another purchase and received an unhelpful reply.

I have to say that with the setup I have now, I am pleased with the way it produces a nice shiny face on both sides of the work rather than the previous flat face setup which produced rough faces and has no chatter with the metal coming off in nice curls...and it just sounds right, and I have ground the blade in the normal way with a flat edge and with the tool fitted to the topslide, no need for rear toolpost or any fancy grinding ....anyway thanks again for your reply to my post.

..Bob..

Ha...! this is uncanny....!

Re: my post 20.09.2018

in the latest issue (ME 4596) Graham Sadlers article series on "Lathes and more for beginners" actually says that some of the cheaper toolholders do not hold the blade properly giving no clearance either side and are best avoided..

As a famous person once or twice said... "I don't believe it ! " the makers of these bladeholders must surely know that they are making something destined to cause problems...for the sake of setting over the milling machine a degree or two when cutting the blade holder profile... it might work ...but its not right... and I noticed I got a better finish on the sides of the work when the blade was set correctly and is a delight to work with.

Manufacturers in the Eastern countries making many of these tools very rarely puts its name on its products, I may be old fashioned but I do remember reading many years ago not to buy anything where the manufacturer was not confident in putting his name on what he has produced, I am minded to send it back to the supplier.

Bob.

I'm glad someone mentioned parting problems again, I have had many problems with this myself and although I can part with reasonable results I can't say I have had an easy time, in the end I purchased a new smaller width hss blade with holder from a well known supplier, this is a 1/16 inch blade which I thought would make the cuts easier.

I was disappointed again, the problem in the end is the blade holder supplied,..I looked at the one I had previously as well and I assumed they would both have been made so that fitting it in a normal toolpost set squarely would give the correct clearance angles at the sides of the blade, to my amazement I found that the holders are not made with an angled side face but are just at 90 deg so that there is no clearance at one side of the blade and double the clearance at the other; this causes the tool to move over and dig in to one side.

I made a new toolholder so that there would be clearance either side of the blade...the results were very satisfying.. has anyone come across this before...? or is this obvious to the more experienced.. I am only too willing to learn..

Bob.

I purchased a bench drill from a well known company and was very much disappointed .. the quill had 1/2 inch of play in it and the table could not be locked in position, it moved as you drilled..! I also noticed quite a lot of 'nod' when I trammed the table.

I should have sent it back but would a replacement have similar problems, I decided to make it a project and sort the mess out.

I made an eccentric bearing for the quill and now has no play.

The table did not lock due to the locking nut surface not being parallel with the machined side of the table support arm bearing and consequently there was only one point of contact between nut and surface.

see below..

The support arm.

The relative angle of the un-machined side.

The 'nod' was a more difficult situation, so I made a new adjustable 'nod' support arm .. below.

The table now trams up perfectly...

Moral of the story... should have bought a vintage drill and renovated it..

Hi All..

I have had this bench drill for a year or so and have had problems with table movement,; if I tried to drill off the exact centre the table would start to tilt in the pressure direction..

Also, when I trammed for the 'nod' ie the tilt in the y axis, it was out by about 1mm over the diameter of the table, and I wondered if this was the reason I couldn't seem to drill a through hole through round stock with any accuracy.

After dismantling the table support arm it was apparent that the table movement problem was caused by the surface that the locking nut had to bear on, it had not been machined from the cast state and was severely angled from horizontal see pic below.

Below shows how much an angle there is.

Consequently the locking nut has only a small area of contact with the surface and therefore not much of a hold on the arm.

It can be very disconcerting when drilling a hole to see too late that the table is moving and if you have a similar machine I think it wise to have a look at this part.

I could have machined this surface and left it at that but the 'nod' tilt bothered me as well so I ditched the original support arm and stitched up an adjustable 'not tilt' support arm.

The table can now be adjusted and trammed up nicely referenced to the quill axis,...below..

...Bob..

Beautiful Steve....!

Its Art...better than any Picasso.