Gallery, Projects and General > Project Logs
Project Halo
bogstandard:
Kirk,
When working with these small sizes, it is well worth building youself a tapping stand, as a few of the lads have done.
It does honestly cut down the breakage problems because you feel with your fingertips rather than your whole hand.
I bought 4 taps for making six engines, but that is looking on the very pessimistic side. If all goes to plan, I should end up with 4 unbroken ones left. The only reason I bought that many was in case I felt one going dull, then it would be thrown away. On the first squeak, it is out of there.
Bogs
zeusrekning:
Looking forward to following this build closely John. The tray for keeping up with all ready made parts is a must for sure. I seem to spend more time hunting than making when it comes to small parts. Good luck with the build man.
Zeusrekning
bogstandard:
This is going to be about one of the most boring posts you have ever seen, all because it is just shots of metal being either hacked down to size, or having a hole stuck in it.
But I suppose it needs to be shown because it is all part of the build.
Whenever I come to machine a fairly complicated piece, I study the drawing and work out a machining procedure.
This needs to be done, because you can easily get yourself into a position where you can't hold a part to finish it off.
This isn't written in stone, as I fairly regularly make a machining procedure, then when I get half way thru, I find I can change it to maybe cut out a couple of the steps by doing something slightly different.
If you can get into the habit of making notes and procedures like this, you will find that things go a lot smoother and less mistakes are made.
The part was mounted into the 3 jaw and about 1/2" was turned down to finished size for making the square flange. It just so happened that this was the largest size that I could hold in the 5C collet chuck, and as I have said, because I am treating it as a production run, I will use whatever I have to get the job done. So if you do it, you will most probably carry on using your normal chuck.
So now the finished size end could be held in a collet.
The first job was to face the end, this will be the datum end that all other measurements go from.
The next op was to centre drill to get ready for putting the bore in.
Because I am using a collet chuck, I can remove the part between operations, but if using a normal chuck, you would leave it in there and finish the whole operation until the bore was complete.
My next step was to drill 1/64" undersize of the finished size required.
A 3/8" parallel machine reamer was then used to finish off the bore. I find that a reamer is perfectly satisfactory for a job like this, but for other types of engines, I would bore the hole.
If you don't have a reamer you have two choices. The first is to carefully drill with the correct sized drill, and hope the bore cleans up nicely enough. Nine times out of ten, it will do. If it didn't, then a little lapping should sort it. The second option would be to bore the hole, a much longer process and your bore should finish up with a perfect finish.
It was at this point I decided to deviate from my proposed schedule. Instead of turning to an oversize, I decided to turn down to finished size, purely because this is where the finning on the cylinder is, and so I decided that it didn't need to be perfectly sized, so I turned down as long an area as I could in one hit down to the nominal size of 3/4". As it turned out, once I had set and locked the cross slide, they all turned to exactly the right size.
These are all the bits with the finning area to size. The top face, as I said before, is the datum face for the overall length.
The 3/4" collet was fitted with an internal backstop. The datum end was put against the backstop, and the machine set up so that after facing across, the cylinder would end up at the required length. Each cylinder in turn was faced off at the same setting.
Unfortunatley, the 5C backstop system is not as accurate as everyone thinks. Because it is mounted into the back of the collet and not into the lathe spindle, just by over or under tightening the collet can make the part slightly longer or shorter. Mine all came out within 0.002" of optimum length, so as far as I am concerned, they are within acceptable tolerances.
If you are using a normal chuck without a spindle backstop, then you will have to do it the hard way, measure, remove a bit, measure and so on until you reach the correct length.
I then decided just to rough size the flange area, rather than finishing it to correct dimensions.
I have got a design in my head for an all in one drilling and flange machining jig that will save me hours of RT work. By leaving the flange until later, the extra thickness will allow more accurate use of the jig.
The bits are now ready for drill and mill work, and me getting the jigs made.
If I get chance tomorrow, I will try to put my idea into metal, to see if this project can be taken a stage further.
Bogs
Darren:
I could see my turret lathe coming into it's own here..... :ddb:
Looking nice John, watching closely as always. A bit more under me belt and maybe, just maybe........ :nrocks:
bogstandard:
That is very true Darren, a turret would have speeded things up no end.
I do in fact have one of those tailstock turrets, a good idea purchase at the time. But for me to set it up to do everything I would want of it, even for this little job would have cost me rather a few quid for good quality chucks. I suppose one day I will get it set up for how I would need to use it.
Mind you, twenty odd bits all the same cause me personally no problems. Once you get into a routine of swapping bits while the machine runs up and down, I suppose it could be nearly as fast as using the tailstock turret because you are having to move the tailstock anyway because of tooling lengths. It is totally different when you have a capstan saddle, you can get in and out much faster.
John
NB.
I have just read my last post, and it is lucky I didn't complete the maching routine that I had written down. Towards the end, it said 'form a 0.110" collar', it should in fact have read 'form a 0.100" collar".
So this is a massive reminder, not only check the drawings, double check your routines as well, to make sure they conform to the drawings.
I don't think it would have caused major problems, but a problem none the less.
A VERY lucky escape, and was caused by rushing things.
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