Machining a flat recess?

[mikemechanic]

Hi all, looking for ideas on machining a flat recess in a piece of round stock. I am making a rim and it neds a few flat recesses on the face and one in the back to drop in a resin center. The back one doesn't have to be pretty but the front one does. I seem to get a little bit of chatter the way I am doing it, any ideas?

Here is a picture to illustrate kind of what I want.


Thanks,

Mike

[2.2 Straight six]

lathe with a boring bar.

[freakray]

Let's start with telling us how you're doing it that you're getting chatter?

For that to be happening, the tool must not be clamped correctly that it's allowing vibration to occur.
What kind of cutting tool are you using?

[mikemechanic]

Originally Posted by freakray

Let's start with telling us how you're doing it that you're getting chatter?

For that to be happening, the tool must not be clamped correctly that it's allowing vibration to occur.
What kind of cutting tool are you using?

I am trying to do it using the Taig boring bar (see pic 2nd tool from the right) and as you can see the tip is angled so I was trying a few different ways to get the flat recess, I tried angling the tip so it would create the flat surface I want. The more I think about it though I guess I could keep it straight and then run it into the inside and create the flat recess like that.



I think one of the downfalls of the Taig is the tool posts. I am going to buy the quickchange tool post from A2Z CNC as they are much beefier and therefore I think less chatter.

I was for some reason thinking that all boring bars were created equal too

Thanks.

Mike

[Murray Kish]

I think you would set the boring bar so that just the tip is cutting (not the entire edge), and then just proceed to keep taking cuts on the inside of the rim as deep as you need to, up to the recess? So, cut it from the inside-out, rather than the front lip back (if that's what you were doing?)

I have no real idea, since I'm obviously a total newb, but that's what i'd try first.

Looking forward to whatever this is gonna be!!!


Murray

[bobss396]

If you're going to drop in a resin center and the center of the hole will be covered, why not drill a deeper or thru hole in the part? Then all you need to do is a simpler counterbore.

Bob

[mikemechanic]

Originally Posted by bobss396

If you're going to drop in a resin center and the center of the hole will be covered, why not drill a deeper or thru hole in the part? Then all you need to do is a simpler counterbore.

Bob

Thanks Bob, this is exactly what I was trying to do. What is the easiest way to do a counterbore, I searched after reading this and found out about stepped drill bits and counterboring bits, is this what you had in mind?

Mike

[bobss396]

In general, what you originally discuss is a "trepan" tool. These have a flat front and clearance on the sides. You can make them from almost anything. The parting tool on the right can be modified easily. They do tend to chatter, so keep the speed down and hold it as short as possible. You can face with them, taking shallow passes, they are a pain to get to cut on center. But if you can drill a pilot hole through, a counterbore is the way to go.

You can bore and face with the tool 2nd from right provided that the existing bore is big enough to accommodate the tool, and the material under the cutting edge is relieved so it doesn't rub on the bore you're trying to open up. For shallow work, these work good and can still be used for other work.

All of my tools are for Hardinge lathes with indexable turrets or Aloris tool post drop in tools. If there was anything special that I need, I make it myself. I've made smaller boring bars out of drill blanks, drill shanks that were cut off regular drills. These are high speed steel and can be modified on a bench grinder with a fine enough wheel (with a good sharp corner). The holders for these are totally homegrown. I made a set that is reamed for standard .125, .187, .250 boring bars.

Basically, I start with a piece of aluminum bar stock about 1.0" x .50" x 2" long, cut a ledge in it so it fits in my tool post holder. It gets held in to the tool post with the allen screws. I hold it in the tool post, put a center drill in a collet, do my center. Take that out, put in an undersized drill, drill that through, follow up with a reamer so the hole is true to size and the boring bar always cuts on center. This is kind of hard to visualize, but in reality the spindle is holding the tool and the tool post is holding the work piece. The boring tool is held into the new holder with either set screws or regular allen screws, usually a 4-40 or a 6-32 works well.

There are a lot of mini-lathe groups on Yahoo and other forums, you would be best off joining one of those. Micro Mark has a lot of goodies for the smaller lathes. If you're serious about it, make the one time investment in an indexable tool post, be able to grind your own tools.

Good luck, hope this helps, Bob

[nobuddie]

many things that chatter, you may go to a small die grinder. Or even the small electric variable speed ones with all the tips. We made a holder for one. And it takes off less and want dchatter if you have it mounted solid. Like a pencil sized one. Probbably take a piece of 1/2" pipe nipple. Split it. Tack it to a small plate and a screw or clamp to lock the halves together. Then go ahead with the part in your lathe but with the grinder instead of a cutting tool. nobuddie cdmiller@netride.net

[mikemechanic]

Originally Posted by bobss396

In general, what you originally discuss is a "trepan" tool. These have a flat front and clearance on the sides. You can make them from almost anything. The parting tool on the right can be modified easily. They do tend to chatter, so keep the speed down and hold it as short as possible. You can face with them, taking shallow passes, they are a pain to get to cut on center. But if you can drill a pilot hole through, a counterbore is the way to go.

You can bore and face with the tool 2nd from right provided that the existing bore is big enough to accommodate the tool, and the material under the cutting edge is relieved so it doesn't rub on the bore you're trying to open up. For shallow work, these work good and can still be used for other work.

All of my tools are for Hardinge lathes with indexable turrets or Aloris tool post drop in tools. If there was anything special that I need, I make it myself. I've made smaller boring bars out of drill blanks, drill shanks that were cut off regular drills. These are high speed steel and can be modified on a bench grinder with a fine enough wheel (with a good sharp corner). The holders for these are totally homegrown. I made a set that is reamed for standard .125, .187, .250 boring bars.

Basically, I start with a piece of aluminum bar stock about 1.0" x .50" x 2" long, cut a ledge in it so it fits in my tool post holder. It gets held in to the tool post with the allen screws. I hold it in the tool post, put a center drill in a collet, do my center. Take that out, put in an undersized drill, drill that through, follow up with a reamer so the hole is true to size and the boring bar always cuts on center. This is kind of hard to visualize, but in reality the spindle is holding the tool and the tool post is holding the work piece. The boring tool is held into the new holder with either set screws or regular allen screws, usually a 4-40 or a 6-32 works well.

There are a lot of mini-lathe groups on Yahoo and other forums, you would be best off joining one of those. Micro Mark has a lot of goodies for the smaller lathes. If you're serious about it, make the one time investment in an indexable tool post, be able to grind your own tools.

Good luck, hope this helps, Bob

Thanks Bob, was there supposed to be pictures with your post? Sounds like you got some great ideas, hope to see some of your stuff, I am learning that without ingenuity machining would not be possible.

Mike