Member postings for John McNamara

I did not watch the entire set this time but did catch one idea that I will try... He wrapped a boring bar in sheet lead to stop it singing. That I am going to try. Many is the time I have hung various bits of material on a bar to try and stop it vibrating. but always out of the work the sheet lead slides in right near the tool.

You learn something every day. Keith's videos are great, not only for the current topic but the little secrets that pop up along the way.

Anyway it sure beats Television!

Regards
John

Hi Graeme

I did not watch the video, When brainstorming a design It is best to start with a clean sheet of paper.

I just watched it and noted how the work was attached to the mounting plate/chuck using Angle brackets and screws.

In industry when large squat pieces have to be machined the vertical lathe is often used. Have you considered this arrangement? there is a lot less counter levered weight, the work is sitting on the table.

You could make a table from plasma cut say 20mm plate 1000 diameter, Under that you could place a spacer say 8mm plate 850 diameter Then a sprocket made from 12mm plate 900mm diameter. All liberally Bolted together.

The 900mm sprocket has a circumference of about 2827mm If you used a 75mm sprocket you would get about 12:1 reduction that will be well on the way to providing you with a decent reduction drive.

The accuracy will be fine for this type of work laser cutting is accurate to about (point) .1 mm Drawing a large sprocket in cad is not difficult.

The table could have a centre ball bearing pair for location axially with support around the periphery to take the load on radially disposed ball bearings. Ideally crowned for the same reason a car back axle needs a differential, the inner and outer edge are traveling on two different diameters therefore at a different speeds. the crown having a narrow contact area greatly reduces the drag and friction. In the past I have used the inserts used in plumber blocks as a cheap source of crowned bearings. A means of preloading the table against the outer support bearings via the centre axle would be needed. Tot that hard. In the end you would have a very stiff work support. Something the arrangement in the video appears to be lacking made evident by the irregular tooling marks on the work.

The drive power will be much reduced. If the spindle is truly vertical the drive will not have to lift an off centre load as it rotates. several tons of wood.

Because the tool mounted on its arm is describing an arc vertically in this case it will need to be counterbalanced, not a big issue but it will need to be done. In the video the operator appears to be directly controlling the tool. Maybe a geared arrangement with automatic feed would be better?

Regards
John

Edited By John McNamara on 27/06/2015 06:33:39

Hi Graeme

I think I would be inclined to go a different route

Consider moving a high speed rotating tool head say a heavy duty industrial quality router through an arc as you very slowly rotate the work piece. That does away with the rather serious safety issues of a large mass rotating at 100rpm. or even 25rpm. Also bits of tree trunk are hard to mount securely.

There are several ways to describe an arc mechanically the easy way is a cranked arm and pivot. You will need an accurate pivot not that hard to do using self centring bearings like this one you will need two spaced apart **LINK**

The arm can have both bearings at one end (harder to make stiff and accurate enough) however easier to position on large work
or
form a semicircle with a bearing at each end Many lathe ball turning attachments do this. I can imagine it may be difficult to position.

For finishing off replace the router with a custom made 3 pulley belt sander using the slack side to conform with the radius of the work not the pulley ends the centre pulley is the driver. This is the way many tube polishing machines work. obviously you will need light tension and the right abrasive or it will dig in.

There are some rather nasty looking "Hogging" cutters available for angle grinders. Maybe for the initial cuts one of these might be a bit faster if speed Is an issue, it would be another attachment for the arm in place of the router

Oh and if you really want a good finish look through this video You will see a method that will work for you if you make a polishing cup, The video unfortunately has a lot of chatter Hmm But the meaty bits are there. and they use the rotating arm I am talking about. They do make a rather special ball.

**LINK**

Using this setup the power and drive requirements are somewhat less demanding.

For off grid use you would need a portable generator sufficient to drive the router and the slow feed. easy to find.

Oh yes you will need a custom trailer kitted out with a jib crane.

Regards
John

Edited By John McNamara on 26/06/2015 09:33:44

Yes it was sometimes used on the back of old radios to attach a battery or an Arial wire.

Gee have not seen one since I was a kid.

Mr Google likes plain English

This was my search:

vintage radio battery brass clip

**LINK**

Regards
John

A while back I had to make one, I used a nice high tensile bolt. I turned down the head leaving a step and silver soldered it into a square. After a good clean up with the wire wheel it looked fine and the hardened bolt thread did not wear as was the case with the old Mild steel one. It got a lot of use.

Regards
John

Hi All

A little further reading on offer to treat revealed, as I expected it would.

That once a consideration has been made for a good completing a sale the pendulum swings in favour of the transaction becoming a contract for the supply of a good.

A good so supplied must be being fit for purpose. supported by the common law. What a great body of work.
Would a reasonable man deem the article to be fit for purpose over the typical life of other similar goods?
Obviously items of higher value are expected to be more durable over a longer period.

A thought..... Engineering tools and machinery often have graduated dials suggesting that the tool can work accurately at the marked tolerances. Can they? If not why are the markings there? Does this fail the reasonableness test?

Before we ever marketed anything it was tested, if we did not like the way it performed it never hit the shelves. we did not inconvenience and alienate our customers by forcing them to be product testers.

I must admit upon reflection all this should be unnecessary maybe it is old fashioned. having been in business over 40 years we always abide by, the customer is always right if there is a problem we fix it. I can count on the fingers of one hand the number of times we ever turned a customer away. customers are what keeps us going.

Regards
John

Edited By John McNamara on 24/06/2015 13:50:18

Hi

The power of the Pen......

When making a purchase In an industrial situation there is often a written specification of performance, quality standards and tolerances of a particular good or service This is given to various suppliers asking for a written tender to supply in return.

Even after the initial tender is received from suppliers there may be further written correspondence until agreement to the terms is reached.

At this point both parties know their responsibilities and a deal is done.

Ok it would be a bit hard to use this process when purchasing a small tool. Or would it be?
A written order that specifies the standards to be met and your particular use is a powerful tool making it much harder for the supplier to claim they were not aware of the use.

in a dispute the consumer is usually not regarded as an "expert" the supplier almost always is; this gives a consumer the advantage. However talk is of not much use if there is a dispute. it must be clearly put in writing.

The consumer makes an offer. The supplier offers an acceptance

**LINK**

OK this process is a lot more difficult to enforce across international boundaries, not impossible but difficult.
what it will do is reduce the number of disputes if both parties have a proper understanding is of the contract in the first place.

So next time put it (clearly described) in writing!

Regards
John

Edited By John McNamara on 24/06/2015 09:47:15

Hi Neil

I think they visit for information provided by the members...
The link below shows free files that have been downloaded from my cloud server by visitors and members.Not to mention the many that just read the pages.

**LINK**

It might be a commercial site but the interest is generated by the thousands of posters. mine is but a tiny contribution to a greater whole.

A bit of a chicken and egg situation.... ?

Regards
John

Hi Izack

I would knock the pin flush in the almost closed jaws of my vice making sure I did not peen the end of the pin too much, maybe a brass drift would help, then put a piece of metal with a hole in it (an old normal hack saw blade would do nicely) under the junior blade, then put them back in the vice and tighten the jaws on the downward projecting pin.

Then inserting two levers (Screwdrivers) under the full size hack saw blade against the vice lever the blade up exerting pressure evenly from each side. By using two levers the blade is lifted straight up, there is less chance of it digging into the pin.

Regards
John.

Its a dumb pop up, I found out the hard way... when you get an email advising you of a post and click on the link it takes you to the site. If you do as I did and immediately scroll down to the bottom of the post to see the latest comment before the pop up has time to act you do not see it but the screen greys out and makes the screen inoperable, as the pop up is modal. I thought I had a virus and logged out immediately. as I said dumb.... The better ones would have followed me down the page.

I wonder how many visitors reacted the same way as me.

As far as logging in is concerned my machine will not remember me. I have to log in every time I visit so I got the pop up every time. I run Windows 7 and IE.

Regards
John

When I was a kid it was called Duralium

Wiki to the rescue!

**LINK**

Regards
John

Hi Alan Rawlins

In the past if I have made counter bores from old drills by grinding the tip away on an old drill leaving a centre parallel pilot section the same size as the hole, in your case to fit an M8 clearance hole. once this is done I just grind in to cutting edges at 90 degrees to cut the bottom of the counter bore hole. Maybe you have one. The shorter the drill is the better as the web will be thicker and you will get a more complete pilot. I guess 14mm is an odd size but worth a try if you have one. I keep a box of broken cutters and worn out or broken drills "Just in case" for this sort of job. Do tests on a piece of scrap until you get it cutting nicely.

Regards
John

Thanks Ian

Agree re the small parallel section, also countersink screws are not as well controlled in manufacture, they vary in thickness from box to box, even within a single box you can get some that sit proud while other will be nice and flush. fortunately the job does not require a perfect height. "Life was not meant to be easy"

Regards
John

Thank you for you thoughts everyone, always appreciated.

I guess I will have to buy a couple and see how they go, consensus being a 3 flute type. Ady1 and John Carruthers suggested a masonry drill I will try that first, If the finish is ok that will be the most economical method and I have a few in stock. I will report back with the result.

Regards
John

Edited By John McNamara on 15/06/2015 08:18:55

Edited By John McNamara on 15/06/2015 08:20:24

Hi All

I have a job coming up that requires countersinking 6mm stainless steel plate for an M6 countersink high tensile machine screw.

The specifications for the screw detail a maximum head diameter of 12mm with a 45 degree countersink chamfer around the 6mm hole. because of the variation in heads the finished width may need to be about 13mm The material is Asian as supplied by the laser cutter. 304 grade... he is not sure of the hardness, well one thing I know is it is tough to work on! ....

I do know that the cross drilled type of countersink cannot cope with the material. a good quality Weldon tool lost its edge after a few holes. The trouble is I need to countersink around 800 holes. Clearly the right tool will need to be sourced. Some of the holes are in plate that is too big for my mill, so I will have to use an electric drill, maybe in a movable drill press jig that is sitting on the may come in handy shelf.

Does anyone have a favoured tool for this type of job. Carbide will last longer but may chip when being hand driven? or HSS easier to sharpen?

Regards
John

Hi Pgk Pgk

Are the cylinders themselves in good enough order to continue using them as is; if you rejigged the knife blades that sit under them. Maybe you could lengthen the slots or pack the blade so it engaged the cylinder more?

Are all four cylinders in need of a refurbishment? I would have thought that some of them would be OK, the same way as the tyres on a car wear at different rates. One or two are normally better than the rest depending on how they were rotated if at all.

Regards
John

Hi Carl

Interlocking plastic tiles look great and are nice to walk on. however how will they stand up to metal swarf? I have yet to find a pair of shoes that are immune to it, the stuff always imbeds itself into the soles.... leather rubber or plastic it does not matter. Unless the tiles are rated by the manufacturer to resist penetration by swarf I would stay clear. I am not sure how it would stand up to heavy machinery also? Or do you have to cut around the heavy stuff.

My floor is painted with 2 pack and it has stood up well except in front of the lathe and mill, the chips have cut through the finish now but it has stood up for almost a decade.

When I do refinish it I will be using a heavy coat of epoxy. There are many brands and types available.

Regards
John

On way of minimising the deflection of the 50mm tube would be to solidly fix both ends of the tube instead of a cantilevered beam (post) as is the norm with a drill press. The support would have to be well clear of the table to allow it to rotate around the shaft without hitting a support structure.

Using the same 500 mm length of 50mm diameter 5mm wall steel tube the deflection with a 35kg load applied in the centre 250mm from the ends would only be about .01mm.

However the design of the drill press has evolved over many years with thousands of design iterations to reach the present almost universal form. An interesting project to better it.

Regards John

Hi Ady1

Some back of the envelope thoughts and musings re your drill press or machine......

I ran A computer program to test for deflection with a load of 35kg applied laterally at the unsupported end of a 500mm hollow steel tube, over a few different sizes and got:

1.28mm with a 35mm 5mm wall tube.
.97mm with a 35mm 12.5mm wall tube. (Note wall thickness 10mm hole in centre)
.39mm deflection with a 50mm x 5mm wall tube
.11mm deflection with a 75mm x 5mm wall tube
.04mm deflection with a 100mm x 5mm wall tube

To completely "fix" a tube (beam) to an unyielding support structure is difficult, there will most likely be some flexure at the fixed end connection, this would increase the deflections mentioned.

As the numbers show, Increasing the diameter has a much greater effect on the stiffness then making the walls thicker. When a beam is subjected to a load the stresses on the load side of the beam are in tension while the opposite side is in compression. The centre of a beam is sometimes called the neutral axis, the closer to the centre you get the less tension or compression forces are applied to the material, in the centre there is equilibrium = no stress. this partly explains why making a beam solid has less effect on stiffness than making it larger, thus moving the tension compression faces further away from each other. Adding material to the centre where the stresses are low is not an efficient use of material.

Filling with Concrete or Epoxy composite materials will increase the vibration damping but not materially increase the stiffness compared to steel they are both less stiff. Using them requires greatly increasing the thickness of the beam or structure as done by the big CNC machine builders.

You also have to consider the strength of a material as opposed to its deflection. Will the beam resist permanent bending damage or creep? will it resist fracture caused by a fluctuating load? (Just like when you bend a piece of wire back and forth to break it). When working with machinery that requires low deflection for accuracy strength normally looks after itself. It should however always be checked and considered.

Regards
John

Edited By John McNamara on 06/06/2015 17:37:00

Just My few Amps worth.

Electronics is not my thing, Although I have built many projects over the years from published art.

Reading through this post has been enlightening it is clear there is a rich source of expertise within the membership.

How about debating and publishing a circuit right here that embodies the group consensus. It may take a few iterations before the dust settles but the result should be rather good, Professionally designed in fact.

I have enjoyed the debate so far.

Regards
John