Thursday, 23 October 2008

Milling in the lathe

As mentioned in previous article about compound tables and cross vices, I'm interesting in milling to get better results than manual filing for my T-nuts.

I realised that because of the small side of these nuts it would be possible to mount them in the tool holder. So I added an extra screw in the tool holder, something I'd been planning to do anyway as I have some shorter lathe tools and it gives me more rigidity when when using those.

I'd bought a small end mill at the Ascot model engineer show and did some test cuts with that. Trying to machine more than about 0.2mm caused the mill to slip in the lathe jaws. Solutions for that problem would be to get a proper collet system to hold the milling cutter but I chose the option of simply trying to cut less metal. I raised the height of the tool post slightly with some circular shims as there was not sufficient adjustment if I only shimmed the item in the tool post. The result as you can see from the picture below is a simple yet sturdy setup.

Milling in the Mini-Lathe

The T-Nut was roughtly sawn to size and then milled. The results are a lot better than my filing attempt but I do need the practice of making a few more...

T-Nuts Filed vs Milled

It is also possible to attach a angle plate to your crossslide and then a vertical slide and a vice. Care needs to be taken not to produce an off balance solution as it won't be sturdy and will put additional strain on the dovetails. Here's an example milling attachment from Varmit Al where he's pushing it to the absolute limits.

References:



http://www.armurerieduroi.com/pages/lathe/lathe_milling.html
http://www.astronomiainumbria.org/advanced_internet_files/meccanica/easyweb.easynet.co.uk/_chrish/tmilling.htm
http://www.vintageprojects.com/machine-shop/lathe-milling-attachment.html
http://www.saunalahti.fi/~animato/transferseu/milling.html from machinist and animator Jan-Eric Nyström, Helsinki, Finland

Wednesday, 22 October 2008

A couple of Machine Shops

Shed builder and workshopshed reader, Rex pointed me at a couple of interesting sites.

http://littlemachineshop.com

Little Machine shop pretty much provides everything you need to get going apart from the metal. They have spare parts, tools, digital readouts, kits for lathe upgrades, fasteners, plans, videos and books. I agree with Rex, the upgrade kits look very interesting, with bed extensions, change gear sets (for screw cutting), speed controllers, and a Tailstock Cam Lock Kit. Their website even calculates international postage based on the weight of the item selected. Unfortunately the US dollar exchange rate is not as favourable as it was but I'll personally keep it bookmarked for both ideas and when the exchange rate (or postage) gets more favourable.

http://www.emachineshop.com

EMachineShop is a completely different type of shop. They provide parts to your design over the Internet.
  1. Download their software
  2. Design your part
  3. Order the part online

Parts can be formed by a wide number of processes and in a extensive range of materials from rubber to stainless steel. The initial setup price is quite high for a hobbiest (currently $150) but if you are going to make more than a few parts then it soon becomes quite economical. The price per part could end up being less than $1. Their customers include home machinists, clubs and schools. For example if you wanted to build some tank tracks then this could be an ideal way to do it, send of the design for a single link and get them to make 200 of them for you! It may for example be possible to have a part machined from solid for less than the price of a custom made casting.

The site also has an interesting design for a rotary stirling engine.

Friday, 17 October 2008

Water Clock

In Shorts Gardens WC2 there is a water clock above a shop, a large tube of water shows the minutes and a single handed dial shows the hours. There is a series of figures below the clock who presumably used to move to celebrate the hour. The clock was made by Tim Hunkin and Andy Plant who made the clock back in 1981.

It would be nice if this clock was operational as the other mechanical clock in London was disassembled when the Swiss Centre was taken down earlier in the year.




If you know of other mechanical clocks in London, I'd be interested to visit them.

Thursday, 16 October 2008

Finishing the Bezel

The bezel I started a few days back was finished off on Monday night and delivered to a happy recipient. The surface was given a very light skim to remove the paint and the ends were rounded off freehand with a round nosed profiling tool and by a bit of fancy handwheel manipulation. This did not result in a perfect finish but a bit of emery cloth smoothed out any imperfections and wirewool and brasso finished it off.



The main reason for mentioning this seemingly simple operation is to tell you a problem that occurs when a piece like this is clamped from it's internal diameter. As the piece is machined it heats up and expands, this causes it to come loose on the chuck. There are probably more sophisticated techniques for dealing with this but I simply kept tightening the chuck between operations and when it started making noise. I expect that flooding the work with coolant would also have worked. I'd be interested to know if anyone has any other solutions to this issue.

Wednesday, 15 October 2008

Blog Action Day - Poverty

October 15th is Blog Action Day 2008 and the topic is poverty. Given the current situation in the UK it's easy to forget that other people are still worse off than ourselves. As a skilled engineer there's several ways you can help.

Organisations such as VSO are looking for a few good people to volunteer their skills. Even if you don't have time or funds to spare you might have a few tools that you can donate to Tools for Self Reliance. Did you buy and extra screw driver, saw or hammer only to discover you already had one in the tool kit? Do you have old tools you can refurbish? It's worth having a look at the site as there's some tips on how to refurbish hammers and saws, perhaps they also need help with writing more instructions? Please bear in mind they are only looking for good quality tools so don't think you can use them to get rid of your junk or scrap metal!

To find poverty you don't have to travel too far from home, there are people who have no homes and people who can't afford clothes or heating. Help the aged is looking for people to recycle their old printer cartriges and mobile phones so you can help the environment as well as help other people. Oxfam GB are also looking for old phones and electronics. Shelter and Centre Point help people who are homeless and have shops and gift catalogues you can buy from. Thinking longer term, perhaps you could donate something in your will to a charity of your choice. If you are a member of a club, perhaps you could donate the proceeds of an engine running day to a charity?

Many of these charities and other good causes can be sponsored when you make ebay sales. Why not donate a percentage of the sale to help someone less fortunate.

Overseas
VSO - http://www.vso.org.uk
Tools for Self Reliance - http://www.tfsr.org

UK
Shelter - http://www.shelter.org.uk
Oxfam GB - http://www.oxfam.org.uk/resources/ukpoverty/
Centre Point - http://www.centrepoint.org.uk
Help the Aged - http://www.helptheaged.org.uk
Ebay for Charity - http://www.ebay.co.uk/ebayforcharity over 3000 charities

Blog Action Day - http://blogactionday.org

Monday, 13 October 2008

New Workshop Practice Series Books





I just spotted that there are three new books in the Workshop Practice Series.

The first No. 41 expands and complements the existing books bringing in a new topic of grinding, honing and polishing.

No. 42 is a data book by Harold Hall, however it is not just full of dull tables with over 100 sketches and technical drawings. Harold Hall has contributed to many of this series and is regular writer for magazines such as Model Engineers' Workshop. It will be available on 1st November.

No. 43 will also be available on 1st Nov and covers the topic of the Mini-lathe. Like myself many model makers and model engineers have a smaller sized lathe and this book covers topics such as setting up, various operations, improving rigidity and other enhancements, and making accessories such a dividing head or part off tool.

You can preorder these from places like Amazon, Foyles or Camden Steam books.

Grinding, Honing and Polishing (Workshop Practice)

Metalworker's Data Book (Workshop Practice)

The Mini-lathe (Workshop Practice)

Sunday, 12 October 2008

Melt 12th Oct

For the latest aluminium melt, I build a new two part flask and tried casting a couple of letters. After a trial run putting the sand in there was an issue with the sand falling out of the cope (the top half) so additional battons were put on the sides (see below).




This was my first attempt at casting with a two part flask and the problems with the sand lead to the closing up of the gates. The gates are tunnels that join the sprue (filling hole) to the hole left by the pattern. The end results were one half of the pattern did not fill at all. This could also have been that the metal had cooled too quickly but that seems unlikely given that the other half formed correctly.



All was not lost though as my wife took a shine to the droplet formed and has asked for it to be turned into a pendant. The sprue also should have a use once I've machined it into a small rod. I also formed a small ingot with the excess which with either be machined into a block as previously or it may just be used for the next melt.



Here's some closeups of the resulting Beta.


Saturday, 11 October 2008

Inventors Exhibition with Wallace and Gromit

Baroness Delyth Morgan, Minister for Intellectual Property has announced that Wallace and Gromit will be at the Science Museum, London in a new exhibition designed to inspire and assist British Inventors.

This £2m exhibition is scheduled to open in spring 2009. The exhibits will be themed around Wallace and Gromit's home and will consist of interactive exhibits, creative activities and animated displays. A section of the exhibition will cover intellectual property, how to protect it, how to maximise it and to encourage respect for others IP.

Nick Park, creator of Wallace and Gromit said:
"Inventiveness has always been central to Wallace's character and I have sketch books full of Wallace's eccentric inventions that have never made it to the screen. It is fantastic that Wallace & Gromit can excite young kids about innovation in this way."

To find out more about patents and other intellectual property issues you can also visit the British Library's Business and IP Centre.

Friday, 10 October 2008

Miniature Steampunk Keyboard

Lizabeta a Steam Punk engineer has been venturing into miniature engineering with her latest projects. Inspired by the shape of some parts from ebay she built the Mini Steampunk Keyboard



Using tiny watch parts, aluminum scrapbook material and copper wire the 30mm (approx) keyboard was created. The keyboard was a photograph of Mr. Von Slatt’s full size steampunk keyboard and glued to the aluminum sheet.

Following on from the success and popularity of this project, Lizabeta has moved on to create other miniature steampunk items.

Wednesday, 8 October 2008

Grease Steam and Rust Association (USA)


The Grease Steam and Rust Association aims to "preserve agricultural history for future generations"

They do this by restoring old machines, displaying agricultural equipment, putting enthusiasts in contact with each other and running an annual fair each October. The show will have historic farm equipment, tractor pulls, Massey Harris tractors and a toy farm show.

http://www.gsandr.com






Tuesday, 7 October 2008

Model Workshop Gifts

The Model Workshop shop has been updated with a gifts for machinists, sheddies, engineers and general bodgers. You can now buy a fun range of kits, models, DVDs and books The Model Workshop shop also stocks a more serious range of technical books.

gifts for machinists, sheddies, engineers and general bodgers

One of my favourites is this model of a man working at a lathe made in stainless steel and the sterling engines are always popular.

Model of lathe worker

Saturday, 4 October 2008

Bezel making

The latest mini project is the making of a doughnut shaped ring in 3mm sheet aluminium. The inner diameter is 54mm and the outer diameter is 70mm. The outer edge needs to be rounded off. The part is to act as a cover for a hole in some tiles around a shower attachment. Not quite sure what to call this, but have settled on bezel even though that's not quite right.

When I heard the dimensions, I immediately knew it was going to be a problem. The lathe's small chuck would never be able to hold such an item on it's outer rim. Hence the order of construction needed to be to first to bore the middle then to hold the ring from it's internal diameter to finish the outer rim.

Raw Materials

The starting point was a rough square of aluminium slightly bigger than the end size of 70mm. This was a cast off from an older project, I believe it's the part of a panel for a rack mounted computer. A bar for work holding was also required, this was a simple piece of mild steel bar from a builders merchants.

Drilling in the corner of the square

A 4mm hole was drilled in each end of the bar. A line was scribed along the diagonal of the square, the bar was placed along that line and the holes in the bar were drilled through into the sheet. The work was held using the one T-Nut and clamp I've made so far.

Drilling through the steel bar

The bar was then remounted using some 4mm bolts with extra nuts to form spacers. These nuts needed to be tightened at least one during the boring operation. You will notice that I had to remove the corners of the work so that it would rotate in the lathe.

Mounting the work

The bar was clamped in a 3 jaw chuck with a second piece about the same size, this moves the centre of rotation to be approximately the same as the centre of the work piece. If I'd had a 4 jaw independent chuck, I could have used that to centre the work.

Centre Drilling

The work was centre drilled then drilled out in steps to the largest drill that fits in the lathe. In this case I have an ideal drill which fits into the MT2 tail stock directly. This is sufficiently large to allow the boring tool to enter the work. Adjust the boring tool so that there is sufficient space between the work and the cross slide. When you move the tool into the work that is being bored you don't want the cross slide to crash into the work.



The work was then roughly bored out to about 52mm.



And then more carefully out to 54mm as required. You can see in this photo how the extra packing moves the bar back into the centre of the spindle.



The work piece is then removed from it's support bar and remounted in the lathe using it's inner diameter. I decided to try the trepanning technique again as I was using a softer material and it was less likely to cause problems compared to the stainless steel washer that I first tried this technique on.



Trepanning needs a knife shaped tool similar to a cut off tool. To you might need to grind a tool that is appropriate. Once I was about half way through the work, I flipped over the disk and remounted on the other side. When the work was nearly through I took the work off and broke it out of it's surroundings. Theses two steps stops the tool jamming and reduce the risk of the surrounding metal flying off the lathe. For more details on trepanning see Model Engineers Work shop 136, article by John Slater called "Making Solid Swarf".



The final steps are to machine the outside to size, remove the black paint/annodising and machine a curved profile onto the outer edge. I don't expect any trouble with those.

Given that this work is to be mounted in a bath room, consideration is needed to galvanic corrosion. If this metal was placed next to steel then it would corrode quickly around the area of contact. For this reason I suggested the bezel was lacquered before installation.

Happy Birthday SMEE!

Happy 110th Birthday to The Society of Model and Experimental Engineers. Why not go and visit them at the Kew Bridge Steam Museum Festival of Models and give your congratulations in person?

Friday, 3 October 2008

Cross Vice vs Compound Table

Since starting on the T-Nuts, I've been thinking of better ways to make these. My main issues are the time it takes to do the filing and that it's difficult to get the nut exactly square and to the right size. Hacksawing to the exact size is difficult and when filing it's difficult to avoid it becoming slightly rounded.

A possible solution to this is setup some form of milling operation in the workshop. I've got a few options. The first is to invest in a mill, this is very unlikely as I expect I'll find a small mill disappointing and a large mill could be too large/heavy to fit in the workshop. I expect that the both will be expensive too. Given the amounts of milling, I'd expect to do, it does not seem like a good investment. The alternatives are milling in the lathe (more on this in a later article) or using the pillar drill for milling (upgrade pillar drill for milling). There are some issues with using the pillar drill, the first is that the bearings are not designed for the sideways thrust that occurs when milling. This could have one of two side effects, firstly the bearings could wear down very quickly and secondly some people have suggested that the chuck could come loose which could be a hazard. Keeping loads low and some modifications to the bearing have been suggested as solutions to this problem. The pillar drill also requires some modifications / additions to allow you to control the movement of the 3 axis. The Z axis needs the ability to be locked in place, it should be fairly straight forward to modify most drills to do this. The X-Y motion can be provided with the addition of a cross vice or a compound table. Beware that there are some some other vices with similar names that don't have the X-Y motion required.


Cross vice and Compound Table

I've been looking at the cheaper priced range of these products and there are are a few differences:

The cheapest compound table is about £80 with the cheapest cross vice being £20.
The compound table is typically made from aluminium with the vice being made from cast iron. This should mean that the vice is more robust than the table and possibly more rigid when milling meaning more accuracy and less vibration.
The mountings on the compound table are T-Slots, this gives a wide range of flexibility in mounting work pieces. These slots may be vulnerable to wear or tearing because the table is made from aluminium.
The compound tables appear to come with simple rule based scales, the vice comes with none. In both cases the motion in one axis can be more accurately found using a simple dial gauge.
The screw threads and hand wheels appear to be comparable between the two.
There is flexibility in the mounting points for each item seem reasonable but you should check them against your setup.
The additional weight of the vice may cause problems if your drill table is too weak.

Suggestions on enhancing a small compound table

Workshop Practice Series