DTI Magnetic Base Stand

Bought one of these from Amazon for £14.99. Not really expecting too much as the real thing from Noga is usually in excess of £100.00. First thing I did was to stand it on a surface plate to check if the base was flat – it wasn’t! Quite a noticable wobble so I unbolted the arm, removed the magnet and trued up the base. The base seem to be made from two steel parts which sandwich a thick central section made from some soft alloy which I suspect is a lead / zinc or similar mix. Looks like the soft alloy is poured in hot to fix the two outer bits together. A large round magnet sits in the central hole and is rotated by the front lever so that sides are magnetised or not. It has quite a reasonable hold when switched on.

DTI Stand With Magnetic Base
DTI Stand With Magnetic Base

Put the base in the mill and machined it flat, it now sits nicely on the surface plate without rocking. Quite how you can surface grind something with a wobble I don’t know but looking at the original finish it may well have been done by hand on a belt sander. The general finish is pretty well down to the same standard. Looking at the photo you may well think the arms are anodised aluminium. Wrong, they are aluminium but are varnished with a semi-transparent lacquer. The finish on the arms is very soft and easily scratched. The black paint on the base is also fairly soft and covers a deal of filler. The clamping action isn’t very smooth so I took the whole thing to pieces and cleaned it up a bit. The arms are assembled with circlips, well bits of bent wire, there are four of them each one a different diameter and different length.

Once apart the action becomes evident, as you tighten the centre screw two wedges engage with the tapered ends of the rods that run up the middle of the arms. The rods push against the steel balls that make up the pivots. I could tell they were steel because they were rusty! The ball joints were also very rough with a good selection of dents. Polished them up on the lathe to improve the action somewhat. The ends of the push rods were also fairly rough so I polished up the wedge end using a fine diamond lap. I also polished up the wedge faces in the same way. All the originals looked as though they had been done either on a belt sander or an off-hand grinder. Also cleaned up the dimple end of the rods on the lathe using the ball to push a bit of wet and dry paper into the depression in the rod end.

Reassembled everything with some lubrication where needed and it seems a little smoother. I still have to turn the clamp knob quite hard to lock all three joints really solid but it is plenty stiff enough to support a DTI. Was it worth the money? Only just, if I hadn’t had the means to adjust it it would have been no use at all.

Arduino Starter Kit

I recently added a stepper motor to my rotary table based on an article I had seen in Model Engineers Workshop. Everything worked OK but I realised I that I knew very little about the Arduino micro-controller used to power the project. As I can see other uses for stepper motors in the workshop I thought I had better find out a bit about programming the Arduino. To that end I bought a kit from Amazon to play with.

The kit I found was by Elegoo who seem to specialise in this sort of kit and parts for the Arduino and Raspberry Pi. They have some interesting looking car kits for another day. The kit is made in China and manages to get a lot into a a small box. Once you have taken a few bits out it is difficult to get it all back in! I borrowed some images from Elegoo’s website as their pictures are better than mine, I am sure they won’t mind. Click On Image For Larger View

The kit contains an Arduino Uno R3 together with a host of things to plug into it. My particular interest was to find out a bit more about stepper motor control and the kit includes a small stepper motor and driver. It also has a DC motor and a servo to experiment with. There is a CD in the kit that contains the manual, 122 pages in pdf format, which has the lesson notes for 24 lessons. The CD also has the sketches (programs) that go with the lessons. The lessons and sketches are available in a number of languages. I have only just started but the lessons seem to be quite well written and the translation is good so no struggling with “Sino-English”. It may be worth printing out the pdf file as you may need to read that at the same time as inputting program data.

The first part of the manual gives an inventory of the kit contents with pictures so that you can check everything is there. The first lesson explains how to set up the Arduino IDE (Integrated Development Environment) there is a copy of this on the CD but it is not up to date so safer to download from the Arduino site for the latest version. The pdf manual also contains information about driver installation with help if you run into trouble. The lessons start nice and simply with flashing the on-board LED and each lesson introduces a new bit of hardware to experiment with. The manual has plenty of diagrams and clear explanations. The programming examples are clear which is good because I know nothing about C++ which is the Arduino programming language. There is a bit of a glitch at lesson 8 where it refers to an earlier lesson that isn’t there. Also the breadboard power supply is introduced without explanation. Having flipped through the manual, code examples become less as things progress, relying instead on the code supplied with the sketches. The code in the sketches supplied is commented but not overly so.

I think the kit will provide a good introduction to the Arduino particularly the link between computer and machine. I wasn’t aware before I got the kit just how many things can be computer controlled. All I have to do now is set to and work my way through the lessons. Whether I remember anything is another matter but I am quite looking forward to playing. I think I will still need a book on c++ though. Oh I did notice that the name is a bit of a play on words eLEGOo but I am sure that was unintentional (possibly). I note that since I purchased my kit (a week ago) the price has gone up quite a bit.

CNC & CSS

Well, this is the first post of 2016 so you may well think that I have been rather idle. You would probably be right but I have been doing a lot of reading about the benefits and mechanics of CNC. I was using the mill and winding the handle for what seemed like hours and thought it would be easier if this was motorised. So I read up on power feeds and that let on to full automation. Whilst there would be a serious learning curve, CNC would without doubt be useful and in the long run quicker.

Router
Router Using Aluminium Profile Frame

There are several routes to take: Buy a new CNC mill, Tormach or similar; Convert my existing mill; Get a new mill and convert that or go down the self build router avenue. I quickly decided that a new CNC mill was way out of budget and was initially keen on the router idea and spent some time designing something that coud be built within the limits of my current equipment. Most of the time was taken with remembering how Geomagic Design worked as I don’t use it that often. Converting the current mill I ruled out as it is I think too small and besides I would probably need a mill to modify the mill. Thoughts at present are focussed on buying a new larger mill and converting that. This of course is a decision that might take years!

I have also been tweaking the website a bit. Mainly removing redundant CSS from the stylesheet and altering the menu somewhat. Hopefully I havn’t broken anything. I have also added more links and fixed or removed a few broken ones.

Chain Whip

Not put anything here for a bit so I thought I would just show what I was doing this morning. Apart from the workshop hobbies I also cycle a bit, nothing too strenuous you understand but I try to get in 20 or 30 miles a week. This is mainly in an effort to keep the weight down and keep semi-fit. A bit of a losing battle to be honest.

However the last few rides the chain was jumping occasionally. Checking the chain is easy just measure from one pin against a rule and the pin at the 12″ mark should line up. If the pin is more than 1/16″ away the chain needs replacing soon. Mine was a good 1/8″ longer so should have been replaced some time ago. (Although most fixings on modern bikes are metric a good few parts still use imperial measurements chains being and example with ½″ links.) Chains don′t really stretch but the rollers and pins wear and introduce slack. I should have checked more often as I ride mainly off-road and the chain is always covered in dust and grit which with water and oil make a nice grinding paste.

cassette
Cassette & removal tool

I fitted a new chain and found that the chain was jumping and skipping all the time, further checking revealed that the rear cassette appeared to be worn, at least that′s what it looks like to me. The teeth on the gears looked to have worn on one side. So I ordered a replacement Shimano 8-speed cassette. Bike repairs are quite easy but you need a few specialist tools, I bought a splined cassette lockring removal tool with the cassette for £4.99 but I forgot to get a chain whip (that′s what the cycling fraternity call them I would probably call it a chain wrench!). You can buy them from about £5 upto a ridiculous £40 if you want the real Shimano one! The tool stops the cassette turning while you undo the lockring. I could probably come up with an alternative but the right tool makes the job a little easier.

chain whip
My Version of a Chain Whip

I looked at the picture in my favoured on-line bike store and thought it would be an easy thing to make. So I found a suitable bit of flat bar and set to. I used the old chain and simply drilled holes just big enough to take the chain rivets, these are a press fit in the chain plates so once pressed back in hold the chain in place. All the shaping I did on the new belt sander, only took a few minutes. Now waiting for the new cassette to arrive in the post to see whether the tool works.

I must remember to keep a closer watch on the chain and make sure that it is clean. I have one of those on-bike chain cleaners, rotating brushes in a plastic tank, that works quite well but the new chain has a removable link so I could take it off and dunk it in the ultrasonic cleaner. I am hoping that the other end of the drive, the chainring, is OK. It looks alright to me and I hope it is because that is a bit pricey to replace as it comes with the pedal cranks as far as I can make out. The joys of cycling!!

Update: the parts turned up the day after I posted. Nice smooth job replacing the cassette, took about 10 minutes, so much easier when you have the right tools! Pleased to report that everything works smoothly, no skipping or jumping, just need to fine tune the gear changes.

LED Mill Light

I have seen a number of articles where enterprising mill owners have fitted LED lighting to improve workspace visibility. Often these utilise LED ring lights that are intended for automotive use and a smaller number using flat panels also used as replacements inside vehicles. I couldn′t find a suitable ring light but came across some very cheap LED flat panel lights on Amazon. I ordered a few to play with and at £1.25 each including postage from Hong Kong it wouldn′t be much of a loss even if I couldn′t make something useful.

I used bits and pieces that I had in the workshop to make a suitable cover and frame to protect the panel but you could probably just cover it in clear tape to provide a bit of protection. The panels come with a foam sticky pad on the back so they can be fixed to any flat surface. Unfortunately there is no such surface on the mill where I wanted to put the light, just a large recess on the underside of the head. I made the panel to be a tight fit into this recess. A small piece of 6mm clear polycarbonate sheet made the front cover with a similarly sized bit of styrene sheet for the back. The frame was from some left over plastic soffit trim but any U shaped plastic moulding would do

The panels come with a selection of “ends” to suit various vehicle lamp styles, these were not needed as I soldered the power lead directly to the board. Just to really confuse me the original red wire was the negative and the black positive, fortunately the boards seem to have a degree of protection built in! The parts are simply the black styrene back the clear polycarbonate front (it still has the protective paper on in the photo) some spacers also from polycarbonate and the frame. I cut the frame just using a tenon saw and a mitre box so they don′t join up too well. Basically just stick the spacers round the edge of the back sheet leaving a gap for the wire, stick the LED panel in the middle. The frame just clips on and holds everything together. Drill a hole in the edge of one of the frame pieces and thread the power lead through it before soldering the supply to the board.

With a bit of adjustment to the width of the light it was a tight fit in the recess under the mill head and at the moment it is just wedged in. It may need some better fixing method if the vibration works it loose. The power is from a 12v plug in supply (Wall Wart) it needs to be DC so I couldn′t use the existing 12v light supply. As can be seen it gives quite a bright light, it is supposed to be warm white but it′s definitely on the blue side.

Surface Plate On A Budget

I was recently marking out a part to be machined using my version of a surface plate namely an old piece of plate glass. I have had this for ages and it normally sits unused in a dusty corner of the workshop (actually all the corners are probably dusty and some with added cobwebs). I was having particular difficulty seeing the the surface due to reflected light and the transparency and once I had finished decided to look at buying a new surface plate. I was surprised to find that small granite surface plates can be obtained at quite reasonable prices. For example Axminster provide a 300mm x 200mm granite plate for about £40.00. If however you want a real precision job a Mitutoyo plate the same size can be had for £234.00.

However as this would probably end up sitting in the same corner of the workshop and only be used on rare occasions I decided to investigate alternatives. I have read in a few places that bits of granite kitchen worktop can be used to good effect and also that Tesco, Argos and the like, sell small granite worktop savers at reasonable prices.

Surface Plate from Argos
Granite Surface Plate

As I happened to be passing Argos I went in and found a 400mm x 300mm granite worktop saver for £8.00. At that price it had to be worth a go and if nothing else would be big enough to tape a sheet of abrasive paper to for flatening plane irons and similar jobs. Once home and unpacked I cleaned it up and checked it with a couple of straight edges. There appear to be no obvious highs or lows and the surface appears evenly ground and polished. I think with my limited ability to test for flatness it will suit my skill level and sufice until I need something more accurate. The only minor downside is that it is very shiny, I think a matt finish is normal on surface plate. I may be able to cut the glare with some abrasive cleaner but that could make it less flat.