A little boring and threading for the weekend.
I am making a plate to hold the flywheels for a HD Sportster. I am using a weight for an exercise machine. Here it is, with me locating center. The boring went well, after consulting with Harold a bit.
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So for the new guys like me, the questions were:
a) how do I get the boring bar set up for the hole?
Answer: Once the mill spindle is located over the center of the hole, with the bar, in the hole, turn the adjusting dial on the head until the tip of the bit is close to the edge of the hole, raise the bit above the edge of the hole, adjust the bit out so as to be able to take a small cut. Take the cut. Measure the hole to determine how much further you need to get to the final dimension. Then just like on a lathe, take the roughing cuts, leave .010 or so for a few of finish cuts. On the finish cuts, try to keep them all about the same. Cut, measure, cut, measure and hopefully a final cut will leave you on dimension. The problem I am having is my measuring equipment is not worthy of the work.
b) Once the bar had gone through the hole, how do I get it back on top with out messing with the bore?
Answer: There are a couple of methods, depending on how critical the finish of the bore is. For what I am doing (press fit of a rod in the hole) finish was not critical. So I just stopped the machine and raised the bit up through the hole. It will leave a mark. If the finish is critical then one must move the bar or table, to allow the raising of the tool without marring the bore. This method has the problem of getting back on center of the hole, once moved off. It can be done, but one must take care to get it right.
I hope I explained that well enough. There may be other methods, this worked for me.
You can see the two holes, just left and right of the center hole, in the picture above. Those were the first holes I had bored. The problem with those holes is that neither are in the right place, they are to close to each other, and one is to large for a press fit, of the 1/2" shafts. My greatest problem has been measuring the holes accurately. The telescoping gauges I have are VERY cheap and do not move smoothly. The smallest of the set won't expand enough to measure the hole and the next largest size it to large to fit in the hole without interference. I ended up using my digital calipers, not the best of methods for sure.
So it was on to making a second set of holes, because practice makes perfect, and who am I do deprive myself of some practice.
The problem was that I needed the center hole for the shaft of the flywheels to go through. I could setup the swivel plate for the vise, but I did not want to go through all that. My DRO has a bolt hole feature and it occurred to me I could use that with an offset of the starting hole, with out moving the vise. So a little reading later, and everything is set up with a 20 degree offset and with the proper dimensions of the hole spacing.
Not a very good picture, but you can see the locations of the new holes.
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I spent some extra time using my caliper, measuring the rods and the hole, as best I could. I did end up removing the bar from the vise, and test fitting the rods. They were to tight, so back in the mill it went, relocate center, using bolt hole circle function of DRO to relocate the holes and a bit more boring to get to a finished size.
It all worked out well in the end.
The finished product.
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My nephew came by to day, needing to replace some wheel lugs in the hubs of a 4 wheeler. I got out my old vise and set the hub on the jaws with enough room for the lug to fall out the bottom. Then using a hammer I pounded them out and the new ones in. On the final lug, one of the jaws fell off my vice. Looking at it I notice the screws where badly worn and needed replacing. I thought they looked like a finer thread than a 1/4X20, which would make them a 1/4X28. Off to the hardware store for some 1/4X28 stove bolt head screws. Hmmm, no one carried them, oh well, I will make some. Back home, fire up the lathe, use some SS, make a screw, it don't fit. After some measuing and test fitting of other screws, I learned they are 1/4X20! Oh well, make some 1/4X20 screws. Turn the screw on the lathe till a nut will fit on it, part it off and test. It did not fit! I am back to the point of I do not have the proper tools for measuring, that which I am making. I need some thread measuring wires! A thin slitting saw for cutting the slot would be nice too. The one in the picture was done on the mill with a 1/8" end mill.
To some this would all seem like a waste of time. Not me, I learned a bunch this weekend.
One of the things I am trying to get better at, is cutting threads to a shoulder. I started by learing to cut them to a gap. Then I learned to do it with no gap and no shoulder.
The threads I cut this weekend, were, SS, to a tapered shoulder, and no gap. Next time I will try to a vertical shoulder, no gap. That should get the heart rate up a bit.
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Time to go pawn shop hunting for a 1 5/16" socket, to take the flywheels apart to align them.
I keep thinking I need to write something, of my observations, for the really new guys, from a new guys point of view. Like my answer to "How close is close enough when machining?". The answer everyone gave me when I asked was, "That depends on what tolerances you need to machine to".The answer from my point of view is: As close as you can measure! You will figure out what the important dimensions are, as you go along, but practicing to get as close as you can, all the time, will allow you to do so, when necessary.
What tools should I buy? The ones that you need for the work you are doing! One can spend thousands upon thousands of dollars on tooling, and some will be used all the time, others very seldom.
I would also recommend a belt drive lathe for totally new guys. You may grow out of it in time, but it will save you a lot of machine parts and tooling when you crash, while leaning, and you will crash.
This is some of the wisdom I have gained from all of you guys, here on this board. You may never fully understand how much that means to me. I do know that I could have not gained the knowledge I have in the short amount of time I have been at this, with out all of you guys taking the time to answer all the questions asked.
So thanks to all of you. As I learn, I will try to contribute to the board by trying to answer some of the easy questions, that many of you have answer MANY times, as each new guy comes to the board.
I hope you find all this interesting.
More to come later.