cutting a shallow concave

[bearcar1]

I have been going over in my head the past week or so, the various methods to cut a shallow concave into the surface of an engine base. The depth of said cut would be about .125" and the width would be approximately 1.00". Now, I have considered mounting the piece to an angle plate that is secured to the lathe carriage and then using a boring bar of sorts mounted between the centers to achieve the final result, but, my question is, what if I used a fly cutter in the mill and set the angle of the head over so that the cutter could sweep a given arc to create the depression. Have any of you gentlemen performed this type of procedure? I don't know if I have made myself too clear here. The ultimate goal is to cut a dished trough if you would, the length of a flat base made from 6061 Aluminum. I'm just machining in my head at this time and am open for suggestions. Thanks.

BC1
Jim

 

[cobra428]

Hey BC1
Tony to the rescue. I made this tool to dome the heads for my radial. You adjust how far the bit sticks out to ge the radius. I hade the pivot point .250 from the end. So if you want a 1.00R you set the bit out .75.

Hope this helps

Tony

 

[Ken Bartlett]

I have done a similar operation at work using a inserted dovetail cuter with the head of the bridgeport tilted at an angle. I have a formula chart at work that gives you, based on the diameter of your cuter and the angle you tilt it at, how big a radius you will make. You then can plunge down a desired amount and mill your trough as long as needed. I will copy it and post it tomorrow if it will help you.

 

[MikeR C]

If you have a boring head, set it for a 2.125" hole, clamp base vertical and when the bit has cut .125" deep the trough will be 1" wide.

 

[Cedge]

Bear
If you are looking to make a "trough" cut, where it runs for some distance along the surface, then tilting the head of the mill makes the most sense. A circular "Dome" cut would be best accomplished on the lathe..... and I must admit Jim's solution is really quite elegant. Looks like another tool for my "to make" list.

Steve

 

[doc1955]

You could set up a knee on the mill or lathe set a boring bar to 2.125 dia. to be exact to achieve 1.00 chord length with a chordal height of .125 and do it that way.





Mike you beat me on the post see Mike above and dito.

 

[cobra428]

best accomplished on the lathe..... and I must admit Jim's solution is really quite elegant. Looks like another tool for my "to make" list.
Steve

That's Tony's solution, Jim was asking the question Cedge. Geezz "I can't get no respect" Rof} Glad you like it!

Tony

 

[Cedge]

Tony....
Aren't you used to that yet?....LOL. Sorry bout that.... just knock the dust off the compliment and it's as good as new....(grin)

Steve

 

[cobra428]

No Problem Steve,
Stuff happens, as long as it can be a help to somebody, that's my satisfaction

Tony

 

[bearcar1]

Gentlemen ???, I thank you all for the suggestions. I just wasn't real certain about the fly cutter arrangement scratch.gif but I may try the boring bar idea. And Tony, that concave tool is way cool. Thm: Perhaps you could put up some dimensions etc. so others could steal copy the design. : Now I just have to get up enough motivation to start collecting the lumps I need for this next endeavor. Stay tuned.

BC1
Jim

 

[mklotz]

Tilting the head of the milling machine to make a "trough" with a radius greater than the tool radius is an old machining trick. Be aware, for precision purposes, the trough is actually a section of an ellipse and is not truly circular.

The math for establishing the head tilt angle as a function of the tool and trough dimensions is a bit tricky. The RADIUS program on my page is set up to do all the dirty work.

 

[bearcar1]

Thanks Marv, I currently am using a MAC but you know, I may just have to search out and acquire a Big Blue laptop and load it up with your software applications. I've looked at them in the past and they all sound like they would solve a great deal of problems for math-stunted screwballs like me. And not to mention the myriad of CAD freeware that is cropping up. But then too, I'm not the sharpest knife in the drawer when it comes to computers either What's a guy gonna do? The more I think about cutting this trough, the more I believe that tilting the mill head over and using either a dovetail cutter as previously mentioned or a fly cutter in backgear. Decisions, decisions. :-\

BC1
Jim

 

[mklotz]

Mike?

 

[cobra428]

Marv,
You know how those old people get....can't remember peoples names :big:

Tony

 

[bearcar1]

My bad. :-[ :-[ :-[ :-[ :-[ :-[ :-[ :hDe:

I'm lucky to remember my own name most of the time, sorry MikeMarv. Rof}

BC1
Jim (at least that is what is printed on the waistband of my underwear) (No, don't go there) :big:

 

[mklotz]

You're forgiven.

I know nothing of Macs (the computers, not the hamburgers) but I would expect that, by now, someone has written something that would allow one to run DOS programs on a Mac. Perhaps some of our computer gurus here can help you.

I can't tell you how many people have written me and promised that they were going to undertake the task to rewrite my software for system X and language Y. I encourage them but, in the back of my mind, I know it will never happen. To date, my pessimism has been thoroughly justified.

My enjoyment is in solving the problems and constructing the algorithms to implement that solution. While I do this in the form of a (C) program, I have absolutely no interest in making the programs run on every contorted computer system out there. A bit harsh, perhaps, but I don't charge for the programs and the source code is included with every program I've written.

 

[bearcar1]

Oh no Marv (I got it right this time ) It was not my intention to ridicule your work or insinuate that I wanted the applications to run on a MAC, I completely understand your stance on the matter. There are patches that are available (I think) that will do the conversion but I would just as soon not put a band aid on a heart attack and simply use a machine with the proper platform already installed. As far as someone doing the translation of all of your hard work, yeah right. It'll never happen. Hey thanks again and take care.

BC1
Jim

 

[bob ward]

Don't know if this provides any useful ideas. This is a cutter I made recently to make a radiused trough 300mm long in aluminium. The trough was 65mm radius x 10mm deep and ended up from memory being about 70mm wide.