fly cutter

[Bourne Bill]

hello,  can someone tell me the correct configuration to grind a fly cutter bit? ant pics etc.?

[Darren]

A good question 

[Darren]

Some insight here http://www.thewarfields.com/cnccookbook/MTMillSurfaceFinish.htm

[bogstandard]

Hi Bill,

I can't remember how long ago this shape was shown to me, and I have passed it on over the years, with very good feedback from the users.

With me having a fairly powerful mill, I can easily take a 0.100" cut with it on non ferrous, half that for mild steel, and end up with an accurate and reasonable finish. Put a 5 or 10 thou cut on and it comes out like a mirror.



The cut to the left is the rough cut, on the right, the finishing. This is on ali bronze.

It is ground up to a full quarter rad as on a left hand lathe tool, with lots of top and back rake (say 10 to 15 degs). The tool is resharpened by running a dressing stone (I use Arkansas) over the face you can see in the pic. It needs to be razor sharp.

Hope this helps.

John


This is a shot from Darren's lathe project, and was done to show the shape of tooling I use and the surface finishes that are produced. So if you see machining shots of mine, look at the type of tooling I am using, it just might give you a clue, otherwise just ask.

[Bourne Bill]

thank you mr. Boggs

[J. Tranter]

Bogstandard can you please show a couple of diffrent views of the way you grind that tool I am trying to duplicate.
Thank you
John T.

[bogstandard]

No problems John.

Here is a quick C-o-C to show you the tool in graphical format (getting technical words now as well).

The first one is showing the 1/4 round, second is the back rake and the third would be classed as bottom rake.
You actually grind 1 & 3 at the same time, then put 2 on last.
Number 4 is how you finally put a razor edge on the tool. I use an Arkansas stone with oil, but you could use a diamond lap with water to stop it clogging, or just a fine emery stone with a touch of oil. This is also how you touch it up during use.
If you ever have a go at some real tough stuff, you will most probably end up with a flat on your main radius. In that situation you have to do the 1 - 3 regrind to get the curve back.

The angles are non critical, but I put a fairly large one on so that it can easily cope with a range of materials. In fact, if you were cutting brass all the time, you could do away with #2 (back rake) completely.




What I have done this morning is go into the shop and ground one up to show you a close up of the finished article.
It was a little dangerous trying to grind with my left hand, keeping one eye on the tool, and take a piccy using my other hand and eyeball. I know I am adaptable, but not that much. So what I have done is ground it up, and flatted out non essential bits with a black marker.
These pics are as they came off the wheel without final sharpening.

The radiused tip.




What I called the bottom rake.




The bottom rake viewed from the other (untouched) side.




And finally, the back rake viewed from the end.



Actually the bit marked top is really the forwards facing part of the cutter, I just marked it up that way to help with the grinding sequence. I just hope I haven't confused you all.

This is the way I grind for getting a good material removal plus nice surface finish. Just remember, start wacking this thru a bit of tough stuff, (I didn't really want to call it Darren's stuff), don't expect miracles.

Of course, flycutters have a myriad of other uses, and in those situations, they have different shaped tooling ground up.

John

[J. Tranter]

Thank you for showing how to grind that bit. I tried it this morning and it was great, never had a better finish.
Thank you again.


John T.

[bogstandard]

You are welcome John, thank you for the feedback.


Bogs

[DICKEYBIRD]

I realize this is an old thread but I know much I like to hear feedback about the things I post so I thought I should let John know how much I appreciate his efforts.

I downloaded & saved John's excellent drawings & pics a couple months ago to try out when I got my R-8 flycutter.  I finally got around to it this past weekend and followed his grinding instructions to the letter.  Man, I was just plain amazed at how well it cuts and the mirror finish I got.  I took a freshly cut chunk of 2024 into the house to show it to the wife and she (who always says "Gee honey, that's nice" turns away and I'm sure rolls her eyes) was fascinated by how shiny & nice it was as well.

Anyhoo, thanks a bunch John!   

[bogstandard]

Milton,

It is appreciated when people give feedback, especially when you have success with what I have shown.

It's also very nice to know that people save or go thru all the old posts, not just mine, but everyones. There is such a lot of information just waiting to be rediscovered.


John

[bramley51]

This is a very interesting tool shape,John.I have always used a right handed turning tool shape.
I'll definitely have to give this a try.Can I assume it will work on cast iron as well?
Thank you for the lesson,kind sir.
Btw.,you should teach bandit to operate the camera,then you can use both hands to do the grinding
Regards.Hans.

[CrewCab]

Nice to have the feedback guys  ........ I'm sure John appreciates, and it is well deserved  but to be fair we like it, so thanks 

CC

[bogstandard]

Hans,

I wouldn't use it to remove the tough outer skin, that is a job for a normal cutter, but yes, it works just fine on cast iron.


John

[wongster]

Hi John,

Sorry to bring out an old thread.  I was doing some flycutting on my Sherline mill and I get quite a bit of scratches using the Sherline Inserted Carbide Tip Flycutter.  Changed back to the one that holds a left hand tool and the finishes seems better.





I would like to try out the shape you shown here.  Will this work on a small mill like what I have?  How do you grind the radius?  Looks so smooth and rounded.

Regards,
Wong

[cidrontmg]

Hi Wongster,
I grind my fly cutter bits freehand. They´re rather short pieces of 6x6 mm HSS, so I usually fix them to a lathe quick change tool holder first, to keep my fingers from burning instantly. And also to guide them better  
The fly cutter body is self made, from 25 mm steel bar, it´s 42 mm long. The shank is <16 mm, to go to a 16 mm ER25 collet. The "business end" I´ve ground according to Bogstandard´s sketches. I´ve tried other forms in the past, but this gives by far the smoothest surfaces.


When grinding the tool form, keep a water cup near, and cool the bit often, if you use something similar to a tool holder to manipulate it. It´s easy to burn the tip, when you´re not holding the bit directly in your fingers.


Of course, in a pinch, you can hold the bit in the cutter itself when grinding. Mine is just rather small to hold, and a QC tool holder also has the advantage of flat surfaces to keep against the grinder table.
 

[sportandmiah]

Bogstandard,

Great pics and description, but I am confused as to what the top is. Is the top where the screws secure the tool?

[cidrontmg]

Top is the surface that cuts. In Wongster´s fly cutter picture, yes, that´s where the securing screws are. In my cutter, the securing screws are on the other side, which is NOT a good construction, I know...
(I´ll make another one of these days, but this thingy has worked quite ok also).

[wongster]

Hi cidrontmg,

Appreciate your reply.

You folks seem to be able to grind the curves so smoothly freehand.  I'll give it a go on my 1/4" (6.35mm) tool.

I bought a Taiwanese grinder over the weekend.  Still figuring out what mod should I do to allow setting the angle of the tool rest.  May need to cut off the stud, leaving the bolt to hold the tool rest.  With the stud in one of the slots of the tool rest and the bolt in another, I'm only able to move the tool rest closer or farther away from the wheel.  

The stud is the little red thing on the bottom slot right at the back:



Don't know if the bolt alone will be strong enough to hold the tool rest if I cut off the stud.

Regards,
Wong

[Davo J]

Bogstandard is no longer with us here on the forum, he left a while back.
Most guys including myself take the tool rest off the grinder all together.
It gives you more room and makes it easier to grind all types of angles free hand.

Dave

[wongster]

Hi Dave,

Thanks for the info.

Sad to hear that he left the forum. I enjoy reading his posts amongst others.

It will be difficult for me a beginner to go without the tool rest. I don't know how to hold the angles required.

Regards,
Wong.

[Stilldrillin]

Wong,

Don't remove the toolrest......       It is there to support the tool, while grinding! 

Hold the tool on the rest, but tilted at an angle to it. (About 5 degrees), to give cutting clearance. 

David D

[cidrontmg]

Wong,
Leave the stud alone, but file the slot in the toolrest a bit wider (not much is needed! Only from the downside), so it will be possible to tilt it. 5 degrees like Stilldrillin says will be just fine for most things. No need for a protractor here, it´s more like a ballpark figure.

[wongster]

Thank you both for sharing.

I learned about not needing a protractor just yesterday when I touched up the chipped edge of the right hand tool.  The test cut on a piece of steel looks ok so far.

Using the tool rest gives me the confidence when grinding.  Maybe I'll attempt to make the adjustable tool rest I saw on Mr Rudy Kouhoupt's DVD.

Regards,
Wong

[Stilldrillin]

Wong,

If you are missing Boggy's words of wisdom. Try on here....... 

http://start-model-engineering.co.uk/

He writes the, BEGIN WITH BOGS section, and we're all still learning from him!

David D