Machining a 1/2round groove in edge of a plate of aluminum

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drmayf

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Long title, but descriptive of what I need to do. First, I have an ancient Clausing 4804 lathe that is just functional. I also have a very small harbor freight bench lathe for dinky stuff. What I need to learn how to do: cut grooves in aluminum or steel plate that are to become full circle tube bending dies for an automatic coil winding machine. These are similar in nature to rope pulleys. Given my near non existent skills, I need some advice on how to go about the cutting of the semi circular groove to match specific tube diameters. My first thought was to obtain my blank, center drill it to a size that can be held in my chuck internally and then machine the edge. Followed by the groove making. The groove needs to match the tube size. I need to be able to do this with tube sizes from 1/4 inch through 3/4 inch diameters. All different blanks of course. It is the tool and method I seek information and guidance on. I see tool bits for indexible holders (i.e. RCMM 43 for instance), but I need to know if this is the correct type of tool and then the technique. I am not making a production run of these things so finding a way to do it cheaply is tantamount. Is there a video that I can watch that anyone knows about? Any assistance is deeply appreciated!!!

Pm as well as posting a reply?

Larry
 
Can you post a sketch of what you want to try to make?


You can use carbide router bits in your mill to make contoured cuts. If you are attempting what I think you are attempting, you'll probably have to use your lathe as a horizontal mill.

Our favorite import machinery supplier (HF) also makes a tubing roller that you should check out.
 
I would try to rough it out with a single point tool, get it close, and then try to use the round inserts to finish the form. Even then, it is going to take a pretty rigid set-up to keep from getting chatter. I would think you could tolerate some part of the form missing, as long as the majority of the groove will support the tube for the bending process. This would reduce the amount of power required to cut the groove.
 
Ok so bear with my explanations. I have some methods that might work; some are harder that others.
-The best method in my opinion for larger radii is to use a radius turning tool that you can build yourself or buy. Now look it up for instructions if you have one or build one.
-If you don't have one don't want one or can't get one I've heard of people loosening their compound and spinning it to effectively cut a radius. If you choose this method ill elaborate and maybe a video at that point.
- this method is simple if you can grind an accurate form tool but is only good for smaller radii and depending on your lathe it could be pretty small. On my lathe I maybe feel like I could pull a 3/4" radius and maybe if I take it real slow a 1" radius maybe never tried prob never will. But that's my lathe not your I have a very (very) stout lathe.

If you need any further explanations just ask.
 
I'm not sure if this will meet your needs but when I needed to bend stainless brake line for a custom application I used Delrin and ground some form tools from HSS. Worked extremely well and I didn't need to buy the dies for my old bender. Delrin is cheap and cuts well with form tools. I turned a simple washer/flange to fit on either side of the Delrin blank, bolted it onto a mandrel and chucked it in the lathe. If you go this way, use low speeds and some WD-40 for lube and it goes quickly.
 
If what you are describing could be likened to a pulley, then I would just grind a form tool to the desired shape and plunge it into the edge of the rotating disc. On the larger sizes you may need to make a special tool or do it in LH & RH versions and cut each side of the groove separately.

Cheers Phil
 
What diameter do you need the final circle to be? I'm not 100% sure that I understand your project. First take your plate and turn it round on the lathe. Make a form tool to plunge into the edge of your plate. Using HSS lathe bit, ground it to produce your 1/2 inch half circle shape.

Is this anything close to what you need???

12bolts types faster than I do
 
The project is for me to be able to make dies to ben tubing of selected sizes. It will, in what I am doing, require three dies per tube size. Dies are flat plate and I will use same thickness of materials for all of them so that they are interchangeable as a set on the machine I am fabricating. The machine has to bend tubing in a spiral. The bend radius will be constantly variable with a specific advance rate of the tube. I have this all figured out although no metal has yet been cut. This is for the first set of tubing dies. I am making pancake spiral from the tube for a steam boiler project I want to run on my DIY dyno. Yes, there are large (read expensive) tube and pipe benders that can roll the pipe into circles. I just have to start at a small diameter and work my way outward. There could be as many as 13 spiral windings for each layer.

Several of you have suggested that I simply grind the tool bit to shape and go for it. I think I have most of the answer now. If I used my standard carbide tools and cut a V groove then followed up with a semicircular ground tool, this might be easily doable. I think I will try this first with my dinky lathe and a thinner piece of material. I might even have some right and left had bits already!!!



Good job, guys!

I appreciate the info and the suggestions and will try them out.

larry
Flammable_Solid said:
Can you post a sketch of what you want to try to make?


You can use carbide router bits in your mill to make contoured cuts. If you are attempting what I think you are attempting, you'll probably have to use your lathe as a horizontal mill.

Our favorite import machinery supplier (HF) also makes a tubing roller that you should check out.
Click to expand...
 
I would try it on the larger lathe, no sense putting too much strain on the mini.

What you can do is with a parting tool cut into the area of the semi circle with a series of steps. Shallow at each end and full depth in the exact center. If you have a 1/2" HSS bit and the capabilities to use it then make a single form tool. If you have 1/4 or 3/8" HSS bits make two, a right and a left so that you can then smooth out the steps. Lacking either one then it falls to "field expedient machining" for example you can step the cut then round out and smooth out the semi circle using a rat tail file or a dowel rod with emery paper (cover your bed ways to keep the grit out of the lathe)

I think I have a link to a spring making setup for the lathe; it may be modified to do what you need. I'll look.

Mike
 
Would me suggesting that you simply turn " Vee " pulley's to the desired size with short parallel sides above the diameter point ?
I don't think the unsupported part would collapse if you annealed the pipe .


Tip to stop pipes collapsing.

Plug one end of the pipe or solder a cap on it and fill it with fine dry sand ,solder a cap that's threaded on the other end and use a long bolt to screw the sand down to compact it before bending the pipe . Once formed either unsolder or cut the pipe ends off so do make the ends long enough .

Or

Fill the pipe with melted canuba wax let it set hard .

Or

Drill / turn out a hole in a block of metal to a 1.5 mm bigger than the pipe diameter , cut it vertically so you have two halves say four inches long with a gully in them , that will act act as the top former , fit one of them on a long arm to" wipe" over/ round a an annealed & packed pipe laid in a fixed groved pully .
 
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