Building the Minimag

Gallery, Projects and General > Project Logs

<< < (4/19) > >>

madjackghengis:
Hi John, that was very nicely laid out, and well explained, beginning to end. I really appreciated the innovative idea of the V-blocks, they were exactly what was needed, and far more accurate with no time lost, than trying to rotate the vise. I'm keeping that idea for my next pass at a similar situation. :beer: cheers, mad jack

Bogstandard:
I'm doing well today, no unexpected visitors calling to stop me getting to my machinery.

Today is mainly about holes, both little and large. I just hope it doesn't end up being a boring post :D

As I have been tapping and tinkering around the mill vice for a few days, on start up, I double checked that my 0,0 datum hadn't moved. No worries, it was still exactly where I left it.

On the very detailed build instructions, it says that you can either spot thru the lamstacks to mark their mounting positions, or use co-ordinated drilling. It is difficult for me to hold and hit at the same time and still keep it accurate, so I have opted for the electronic DRO route. I did a bit of measuring of one of the lams and got my first datum point, then I could just use all the drawing dimensions. This is my working out.

Using my figures, I spot drilled all the points, plus one in the middle, I will tell you about that in a couple of minutes.
You might notice that I said spot drill rather than centre drill. Ever since these drills have dropped in price dramatically, I haven't used centre drills since, they are just too inaccurate and very prone to breakage. For those in the UK, this is where I get them from. About the cheapest you will find anywhere.

http://www.engineeringsupplies.co.uk/drilling-c-160.html?9=172&10=&11=192&12=&13=

After spotting, I followed them up with a 2.5mm drill to a depth of 8mm, all except the odd one out.

Time for a bit of an assembly job.
You will find throughout this block machining exercise, you will add a bit more to allow you to machine a bit more.

So the holes were hand tapped out to 3mm and the bits were got ready to fit.
I would make a suggestion to do what I did, that is to clean down the lamstack holes, very gently, with a 3mm drill. Some of the glue had wicked it's way down to the hole area, and when I came to screw the screws back in, they were so tight, the lamstack started to split apart. So I stuck them up again, let 'em dry a bit, did the drill thingy and screwed them onto the block.

I had to add an extra lam to each side so that the brass lam sat flush with the surface. Spare lams are supplied for doing this very thing.

It looks like my drilling was OK.

At this stage the instructions suggest you mount the block into a 4 jaw on the lathe to do the boring. Unfortunately, that is very difficult for me to set up, and I find it much easier doing it on my mill. So you will have to imagine that what I am doing is on the lathe.

The spot drill point was refound by following the coordinates in the 'structions, and using a series of drills, I opened the hole up to the recommended 3/4". If you don't have drills of this sort of size, I would suggest you use the biggest you have, and bore the extra out.

Using my imperial boring head, the block was opened out to two distinct sizes, all very precise info is given in the build book, one all the way through, then the other to form a recess.

This is what it looks like.

The one all the way thru is to take the pair of bearings, and the recessed one for the rotor. You will notice that the boring operation has cleaned up the inside faces of the lamstacks.

So yet again, the block was put back to it's datum place.

This next stage takes you part way to fitting another bit, and also, why I wasn't worried when I overan the stack slot on the initial machining.

I am using a 5mm el cheapo Chinese end mill here, if it will do the job, why pay megabucks when you can get them for pennies.

Using the same technique as I used on the first large slot, a beginning slot was cut down to just shy of full depth, somewhere near the middle of where the slot needs to be.
I will be creeping towards the top area of the lams, and when I get there, put the cut to full depth and take a skimming cut across the top of the lams, just to clean them up.

Like this.

Now I needed to concentrate on getting the slot to a very snug fit around the lams in the coil. Measuring both sides up, they were the same size, but very slightly tapered back to front, larger at the front, perfect.

Get close, then using 1 thou cuts, gently open up the slot.

This is what I ended up with, the coil lams pushed fairly easily into the slot for the first 3/4 of the depth. When the holes are drilled and tapped, the screws will pull it in and form a perfect friction joint between coil and the two side lamstacks.

If they are too tight, a quickie swipe with a file will put it right, but that will be a bit later.

The coil bit has to be left now, while the cutouts in the block for the coil to fit into are done.

That is the next job.

Bogs

Dean W:
Quite an interesting thread, John. It takes shape fairly quick after a certain point.

ozzie46:

Nice. Very well documented as usual John.

Ron

Bogstandard:
Thanks Dean & Ron.

On first post of this topic I showed a line drawing of the part I am now making, which to a novice looked rather daunting. But as I have progressed, it is showing that with a few basic machining techniques, the complicated looking part is starting to emerge, one bit at a time, and that is how you should view all overwhealming looking parts. Just a series of easy machining bits put together, to make the whole.

John

Navigation

 Message Index

Go to full version