Sure enough the next day I split the mill into two pieces and carried it to the garage workshop and put the two halves on the workbench.
I then got a little carried away and started dismantling it ready for cleaning and ended up with this pile of bits :o)
Now that it is all apart I can make some decisions about how much of it I want to put back together and also have a better look at how various parts can be modified for CNC.
For starters I will be ditching the spring mechanism on the Z axis in favour of a gas spring.
Ideally I would also like to swap the spindle from MT3 to R8, Arceurotrade list them at £29.36, however they are out of stock and don’t seem to know when they will be back in. Axminster claim that Sieg won’t sell one and advise not to change it. Importing one from LittleMachineShop while possible would end up costing me double what Arceurotrade charge.
The MT3 spindle and bearings would not go to waste, I would use them as parts for a 4th axis and machine the end of the spindle to have a 1 1/4-8 TPI BSF thread so I can use the chucks from my Mellor Lathe, thereby saving me the expense of more chucks.
I have also acquired a couple of 36V 500W brushless DC motors from Ebay for £40.00 each, one of which will provide the motion for the 4th axis.
In the short term, I want a DRO for this mill, as I really don’t care for counting how many times I turned a given handle in order to achieve any kind of repeatability. I aim to make all of the brackets, etc for the CNC conversion on the mill and whilst I appreciate that many better machinists than I will ever be have achieved far greater precision work without any of these “newfangled” gadgets, I don’t have a lifetime available for learning all that they knew – yes, I still need to learn about feed rates and such like, but if I can take the odd shortcut to make my life easier, so much the better.
For quite a while I was contemplating the Shumatec DRO 350, I could buy just the board (£14.40) and possibly the enclosure (£9.00 un-machined or £21.00 machined) plus £8.50 shipping, then acquire all the parts myself which I worked out would come to about £18.00 (a few of which I would still need to acquire), this was rapidly becoming expensive even without the scales and unfortunately it does not actually work with Igaging scales (they are supported on the DRO550 with a few modifications), just glass scales, or the “Chinese” scales.
It would also seem that people have issues with “glitching” on the “Chinese” scales and the Shumatec DRO 350, and even on the DRO 550, not all of these issues have gone away (see blog posting by Wildhorse Innovations on the subject), plus the DRO 550 is basically a throw away board, should you have any issues with it, as it is all surface mount and only available via a group buy, if enough people ever sign up for the next batch.
Trying to locate a cheap source for linear scales in the UK is not easy (there are loads of suppliers in the US, but most will not ship to the UK, or charge silly shipping rates. One of the cheapest sources is probably Machine DRO UK, at £34.27 for a 12″ scale and £28.55 for a 6″ scale, plus postage of £5.75, making a total cost of £102.84. These scales would then need connecting to an external display or I would be forever bending around the mill to read the values.
I ended up buying a couple of Igaging linear scales with remote displays from Taylor Toolworks (ebay shop) he did me a price of $101..89 for 2 x 300mm (12″) for the X and Y axes, and 1 x 150mm (6″) for the Z axis and a combined shipping cost of $32.75 for a total price of $134.64 (£81.29) and put up a listing specifically for my requirements.
I was intending to simply use the remote displays on their own on a little arm out to the side of the mill, as has been done by several others, but I then came across the DIY DRO project by Yuriy Krushelnytskiy, and saw that he had a couple of solutions, one using an Arduino and one using the Ti Launchpad, both of which then communicate via bluetooth to an app “Touch DRO” on an Android 4.x tablet or phone. Both versions are compatible with the Igaging scales, the Ti Launchpad version also supporting glass or “Chinese” scales.
This solution as proposed on Yuriy’s site makes use of an Arduino or Launchpad board and then adds pieces to that – fine if you are not too bothered about the cost of the boards and associated shields, but could potentially be done much cheaper with a perf board and just the required components, most of which cost less than 1p, done this way the most expensive item is the bluetooth module.
Yuriy also suggests a 7″ Android tablet ideally with a WXVGA display (1024×600) and suggests either a Google Nexus 7 or a Samsung Galaxy Tab 2. Now both of these, even second hand are around the £100.00 mark and as such cost way more than I am willing to drop on a tablet that is going to sit in the workshop and potentially get scratched up and or messy.
He states that the only real requirements are Android 4.x, Bluetooth and touchscreen, with WiFi, WXVGA and an SD card slot being nice to have items, CPU, memory and storage not really being high on the list of requirements as the app is not really going to stress any of them.
As such I started looking for a “cheap as chips” 7″, WXVGA Android 4.x tablet that I would not mind too much if it were damaged as I would simply replace it, I came across the Samsung S7502 tablet on “special” at aHappyDeal for £30.74 inc P&P, it has a 1GHz CPU, 512Mb of RAM, 4GB ROM, runs Android 4.1 along with all of the “nice to have” options including a USB connection and thought that would fit the bill perfectly.
