Author Topic: fly cutter (Read 91272 times)

Bourne Bill · « **on:** March 06, 2009, 06:12:36 AM »

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

Darren · « **Reply #1 on:** March 06, 2009, 06:39:45 AM »

A good question

Darren · « **Reply #2 on:** March 06, 2009, 06:53:27 AM »

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

bogstandard · « **Reply #3 on:** March 06, 2009, 09:57:55 AM »

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 · « **Reply #4 on:** March 06, 2009, 10:52:54 AM »

thank you mr. Boggs

J. Tranter · « **Reply #5 on:** March 20, 2009, 01:30:23 AM »

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 · « **Reply #6 on:** March 20, 2009, 07:38:27 AM »

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 · « **Reply #7 on:** March 20, 2009, 04:21:17 PM »

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 · « **Reply #8 on:** March 20, 2009, 05:54:01 PM »

You are welcome John, thank you for the feedback.

Bogs

DICKEYBIRD · « **Reply #9 on:** October 14, 2009, 01:27:40 PM »

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 · « **Reply #10 on:** October 14, 2009, 01:44:36 PM »

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 · « **Reply #11 on:** October 14, 2009, 06:50:32 PM »

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 · « **Reply #12 on:** October 14, 2009, 07:58:37 PM »

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 · « **Reply #13 on:** October 14, 2009, 11:44:48 PM »

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 · « **Reply #14 on:** August 15, 2010, 08:13:43 PM »

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 · « **Reply #15 on:** August 16, 2010, 07:17:27 PM »

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 · « **Reply #16 on:** August 16, 2010, 07:40:13 PM »

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 · « **Reply #17 on:** August 16, 2010, 07:51:15 PM »

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 · « **Reply #18 on:** August 16, 2010, 09:05:33 PM »

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 · « **Reply #19 on:** August 17, 2010, 01:48:30 AM »

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 · « **Reply #20 on:** August 17, 2010, 03:16:16 AM »

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 · « **Reply #21 on:** August 17, 2010, 03:27:23 AM »

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 · « **Reply #22 on:** August 17, 2010, 09:05:47 AM »

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 · « **Reply #23 on:** August 17, 2010, 11:04:33 AM »

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 · « **Reply #24 on:** August 17, 2010, 12:39:54 PM »

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

wongster · « **Reply #25 on:** August 17, 2010, 01:20:32 PM »

David,

Appreciate that.

Regards,
Wong

wongster · « **Reply #26 on:** August 21, 2010, 01:30:22 PM »

Bill, hope you don't mind if I use your thread to ask my question on the tool I grind.

Spent quite some time in my shop today to attempt to grind the tool with the big radius on 1/4" square HSS for flycutting. This is what I get:

View from top.

From the end.

From the radius.

The result is rather crude and doesn't seem to work well as the part of the radius that came in contact with the work piece was very near the shank of the tool. I'll study the photos again to see what went wrong with my grinding. Don't know if its because of the angle of the flycutter body holding the tool being too shallow.

One thing I did learn today which I'm rather happy about; I got a good feel for free hand grinding. Took the opportunity to "repair" those damaged HSS bit I kept and did some test cut. Not too bad.

Anyone have pics of this type of tool touching the stock? Want to see which part of the radius should be doing the cutting.

Regards,
Wong

fatal-exception · « **Reply #27 on:** August 23, 2010, 06:51:06 PM »

Front the front of the tool, try to make the radius as smooth as possible for the best surface finish. You will want to do the final honing with a diamond or some other stone. Only the leading edge of the tool cuts, so it doesn't matter about the part of the edge closest to the shank, unless your tram is that far out.... What you have ground there looks fine to me. If your not happy with it, keep trying till you get it right. Remember, it doesn't matter what it looks like, it matters how it cuts. As long as you have adequate relief on the front and bottom, it should cut fine.

(sorry iPhone in dark shop...)

wongster · « **Reply #28 on:** August 23, 2010, 06:56:28 PM »

Thanks for the tip.

Wow, yours seem to be a rather deep cut. I'm only doing max of 0.25mm per pass, as recommended by Sherline. But I'm usually on around 0.15mm to 0.2mm.

Regards,
Wong

Bernd · « **Reply #29 on:** August 23, 2010, 07:22:10 PM »

Quote from: wongster on August 23, 2010, 06:56:28 PM

Wow, yours seem to be a rather deep cut. I'm only doing max of 0.25mm per pass, as recommended by Sherline. But I'm usually on around 0.15mm to 0.2mm.

That all depends on the size of your machine and rigidity of the spindle. If you have a Sherline then go by their recomendation until you get used to how deep a cut it will acutally do.

Bernd

wongster · « **Reply #30 on:** August 23, 2010, 08:07:05 PM »

Thanks Bernd. I'm quite comfortable with up to the recommended 0.25mm. For the sherline flycutter with a left hand tool mounted, the recommended spindle speed is 1/2 of the usual for any given material. Found that the surface finish wasn't really nice. It gave a nicer finish with full spindle speed of 2800rpm on aluminium.

So far this flycutter has been giving me better result as compared to the one with insert (also by sherline). The one with insert gave circular scratch marks on the surface.

I'll try grinding the rounded tool again to see if I can get that right.

Next task for the QTCP holder is to mill the slot before doing the dovetail. Have a couple of questions on that. I'll put them in the thread I started on this little project.

Regards,
Wong

sportandmiah · « **Reply #31 on:** August 23, 2010, 11:08:05 PM »

Bogstandard's pictures make no sense. The "Top" doesn't appear on the top, but on the side. And the cutting edge is on the top also? What does "top" mean?

wongster · « **Reply #32 on:** August 23, 2010, 11:40:22 PM »

This is my take on your question:
We're using left hand tool for this. When placed in the slot of the fly cutter, the top of the tool faces the side. So the top is now the side in this orientation.

Regards,
Wong

No1_sonuk · « **Reply #33 on:** August 24, 2010, 09:24:40 AM »

Quote from: wongster on August 23, 2010, 06:56:28 PM

Wow, yours seem to be a rather deep cut. I'm only doing max of 0.25mm per pass, as recommended by Sherline. But I'm usually on around 0.15mm to 0.2mm.

I might be wrong, but it looks like a block of Delrin (plastic). That could explain the deep cuts.

Quote from: wongster on August 23, 2010, 11:40:22 PM

This is my take on your question:
We're using left hand tool for this. When placed in the slot of the fly cutter, the top of the tool faces to the side. So the top is now the side in this orientation.

I believe that is the case.
Think of it as a lathe tool. If you used a lathe tool as a fly cutter, you'd need to turn it on its side.

fatal-exception · « **Reply #34 on:** August 24, 2010, 04:55:18 PM »

I'm not using that cutter on a Sherline, and yes it's a block of HDPE plastic. 1/8" in that stuff is a light cut.

I agree that the pictures are confusing. Even if your turning a lathe tool on it's side, it should be labeled as it would be held in the tool holder.

Just my 2 cents.

Paul

wongster · « **Reply #35 on:** August 24, 2010, 06:57:57 PM »

Paul: I meant to say that I can only do max of 0.25mm per pass. It always wow me when I see videos or photos of machines being able to do such a deep one (non Sherline), especially those turning videos. Didn't know its not metal

All: can I grind those brazed on carbid tool? I've 2 pieces of left hand that were chipped sometime back. Couldn't bear to throw them away.

Regards,
Wong

No1_sonuk · « **Reply #36 on:** August 24, 2010, 08:04:53 PM »

Yes, you can grind carbide, BUT you need a special wheel for it.

If you try to grind carbide with an ordinary wheel that's meant for HSS, you'll just grind away the wheel and not the tool.

wongster · « **Reply #37 on:** August 24, 2010, 08:23:12 PM »

You have the name of the wheel?

cidrontmg · « **Reply #38 on:** August 24, 2010, 09:53:42 PM »

Ask for a silicone carbide grinding wheel, they´re usually green. See this
http://www.rdgtools.co.uk/acatalog/Grinding_Wheels__silicone_.html
I grind mine with a diamond cup wheel, bought it from RDG Tools several years ago, and it´s still like new.
http://www.rdgtools.co.uk/acatalog/100mm_Diameter_Diamond_Grinding_Wheels.html
Mine is the 2nd from top. Diamonds may be the girls´best friend, but they are nice in the shop as well

P.S. I use the diamond wheel ONLY for sharpening carbide tools. They will cut anything, of course, but HSS tends to clog the wheel, so it will appear blunt, which it really isn´t, but can be difficult to clean.

fatal-exception · « **Reply #39 on:** August 24, 2010, 10:37:06 PM »

Here's the only 2 pictures that are needed in my opinion:

The black line near the tip is some built up HDPE plastic that I didn't notice when I took the picture.

This tool is held in the cheapest, worst finished piece of Chinese cra..er..steel that I've ever had in my shop...but it works.

It made all these blocks the same size within .002" in either direction. Not bad for a hand ground tool and horrible tool holder!

again

wongster · « **Reply #40 on:** August 25, 2010, 01:43:03 AM »

Hi cidrontmg,

Any idea is those cup type got to use with different type of grinder?

Regards,
Wong

Stilldrillin · « **Reply #41 on:** August 25, 2010, 02:20:05 AM »

Wong,

I use a 50mm dremel type, diamond disc........

Works well, for me!

David D

cidrontmg · « **Reply #42 on:** August 25, 2010, 09:11:28 AM »

Quote from: wongster on August 25, 2010, 01:43:03 AM

Hi cidrontmg,

Any idea is those cup type got to use with different type of grinder?

Regards,
Wong

Hi Wong, I use my cup wheel in a 20€ Chinese grinder, for the time being at least. I´ve been thinking of making a more elaborate tool grinder, but not yet done much about it. Collected some parts. Another project for the future...
I obviously needed to take off the wheel protection. That´s not any danger, the diamond cup is aluminium, so it won´t shatter (don´t take the protection off with any "stone" wheel, though!). Also, I needed to turn a spacer and a washer for the cup wheel, it has a bigger hole than the grinder axle. Just some aluminium bar stock, nothing fancy. But reasonably accurate, so the cup wheel runs as true as you can get it.
There´s also a small table to hold the tool piece. The wheel cuts with its "outward" side, so the table is towards that end.
Tried uploading pictures to Photobucket, got this
"Photobucket Site Maintenance
Images and videos may continue to serve during this short maintenance."
So some pics and notes here.
The grinder tables rust in an instant when they get wet from the water-cooled tool bit... Just surface rust, but they don´t look nice. The diamond wheel table is rather flimsy, but has served its purpose. I should have built something looking more like the other end table, but contemplating about a far more elaborate tool grinder has put that table on hold... Function comes before good looks, and I like ball handles...

wongster · « **Reply #43 on:** August 25, 2010, 10:38:45 AM »

Quote from: fatal-exception on August 24, 2010, 10:37:06 PM

The black line near the tip is some built up HDPE plastic that I didn't notice when I took the picture.

Can I say that the black line is the edge that was doing the cutting? Mine was further up to the left (the straight part) of the cutter in your pic. Could be the angle of my holder.

wongster · « **Reply #44 on:** August 25, 2010, 10:42:11 AM »

Quote from: Stilldrillin on August 25, 2010, 02:20:05 AM

Wong,

I use a 50mm dremel type, diamond disc........

Hi David,

The block behind - wood?

Regards,
Wong

No1_sonuk · « **Reply #45 on:** August 25, 2010, 11:15:36 AM »

Quote from: wongster on August 25, 2010, 10:38:45 AM

Can I say that the black line is the edge that was doing the cutting? Mine was further up to the left (the straight part) of the cutter in your pic. Could be the angle of my holder.

Yup. The curved part is what's supposed to be cutting.

Stilldrillin · « **Reply #46 on:** August 25, 2010, 04:19:52 PM »

Quote from: wongster on August 25, 2010, 10:42:11 AM

Quote from: Stilldrillin on August 25, 2010, 02:20:05 AM
Wong,

I use a 50mm dremel type, diamond disc........

Hi David,

The block behind - wood?

Regards,
Wong

Just a disc of 12mm plywood.......

David D

No1_sonuk · « **Reply #47 on:** September 11, 2010, 05:06:09 PM »

Quote from: No1_sonuk on August 24, 2010, 09:24:40 AM

Quote from: wongster on August 23, 2010, 11:40:22 PM
This is my take on your question:
We're using left hand tool for this. When placed in the slot of the fly cutter, the top of the tool faces to the side. So the top is now the side in this orientation.
I believe that is the case.
Think of it as a lathe tool. If you used a lathe tool as a fly cutter, you'd need to turn it on its side.

I took this statement of mine, and a bit of

struck me. See the attached images.

That's a 5mm dia. profiling tool on an 8mm holder.

j45on · « **Reply #48 on:** September 11, 2010, 05:28:07 PM »

great idea is that the finish under the tool ?

No1_sonuk · « **Reply #49 on:** September 11, 2010, 05:38:37 PM »

Yup.
It looks rough, but it feels smooth - I'm assuming my lack of flycutting experience contributed to the look of it.

BTW, that block is aluminium.

AdeV · « **Reply #50 on:** September 11, 2010, 05:42:26 PM »

Quote from: No1_sonuk on September 11, 2010, 05:38:37 PM

Yup.
It looks rough, but it feels smooth - I'm assuming my lack of flycutting experience contributed to the look of it.

BTW, that block is aluminium.

Whaddayamean "rough"? That surface looks almost glassy. You'll be there for hours with the ultra-fine wet&dry, polishing compounds and other paraphernalia trying to get a better surface than that...

Seriously, that looks really good. And great idea to use the button insert tool, that should be good for steel and even this lousy ali-bronze stuff I'm using just now.

wongster · « **Reply #51 on:** September 11, 2010, 06:04:05 PM »

That's a good idea!!! No need to rely on my grinding skill, or the lack of it...

Are you able to give me the angle of that holder of yours? The part that is slanted to the horizontal.

Regards,
Wong

No1_sonuk · « **Reply #52 on:** September 11, 2010, 06:13:03 PM »

I'm not sure of the exact angle - it looks like about 20 degrees off horizontal. It's a body I bought that came with an unground HSS tool. I just took that out and put the lathe tool in instead.

I should think just about any angle would do, though, as the cutter is circular.

j45on · « **Reply #53 on:** September 11, 2010, 06:20:55 PM »

Quote from: No1_sonuk on September 11, 2010, 05:38:37 PM

Yup.
It looks rough, but it feels smooth - I'm assuming my lack of flycutting experience contributed to the look of it.

BTW, that block is aluminium.

I was not criticising the finish it looks great

I dont have a fly cutter yet and grinding a tool has put me off but you post made me buy a glanze profile tool to complete my lathe set
And now i'm shopping for a fly cutter to fit it

No1_sonuk · « **Reply #54 on:** September 11, 2010, 06:57:13 PM »

As I said - lack of experience. That's the largest area I've ever fly cut.
My comment about it being rough was because of Bogs' photo and comment about a "mirror" finish on the first page of this thread.
Mine's kind of a very scratched or smeary mirror.

wongster · « **Reply #55 on:** September 11, 2010, 07:31:12 PM »

I found that I get nice finishes when the cutter is cutting at the trailing end of the circle. In my case, from right to left.

Wong

cidrontmg · « **Reply #56 on:** September 11, 2010, 08:35:47 PM »

No1_sonuk,
I´ve also tried a similar round- tipped tool, an exact copy of yours. It works rather well with steel, ali, cast iron (chips fly even straight from the cast surface), less well with brass/bronze. The surface finish is rather scratchy, though. An HSS tool bit gives a better surface, but it must be really razor sharp. The classic test for a keen edge is to check if it will cut hair from the back of your hand. With a carbide tip, no chance. A sharp HSS bit, no problem.

And in general, the ready-made fly cutter shanks have usually far too little an angle for a Bogs- style ground tool bit. The angle should be at least 20^o, but it won´t hurt any if it´s 40-50^o. Obviously the sweep will get less with a steeper angle, and there´s less "air" above the workpiece.

No1_sonuk · « **Reply #57 on:** September 15, 2010, 04:21:00 AM »

Last night I discovered a flaw in my cunning plan...

Be careful if you try fly cutting up to a shoulder using an insert lathe tool. Depnding on the design of the tool, the support behind the insert might not have enough clearance to get round.

Mine didn't

On the tool I showed above, the support goes straight down/back with no angle. It was designed as a lathe tool, which doesn't need a relief angle. Of course, one could always make or modify an insert holder specifically for the job with sufficient undercut.

Bogstandard · « **Reply #58 on:** September 15, 2010, 07:15:02 AM »

Having read this post all the way thru, it seems I caused some confusion with regards to 'TOP'. If you actually go to the first page, and find where I put up the grind pics with the pretty red lettering on, directly under the last pic, I explain what is meant.

Another couple of points that do need to be brought up. The radius of the cutter should be the width of the cutter blank, so for a 6mm blank, the radius should be 6mm, not elongated as some of you have done.

The other point is the direction the faces need to be ground. The direction should be with the grind marks at right angles to the cutting face. Do the radius grind first, then the front of the cutting face. Doing it that way, you are doing just two grinds. You sharpen by rubbing your stone against the vertically ground angled face, not around the radius grind.

I have done a C-o-C to try to explain what I mean.

Bogs

wongster · « **Reply #59 on:** September 15, 2010, 08:00:17 AM »

Hi Bogs,

Glad to "see" you in here. Hope you're better.

I did the radius about the size of the tool width but it seemed that the cutting action was at (or almost) the shank. So I "lengthened" the cutting edge but grinding it longer. It could be the angle of my holder being too shallow.

Regards,
Wong

Bogstandard · « **Reply #60 on:** September 15, 2010, 10:02:33 AM »

It just might be that Wong. You are not getting the correct edge shape presented to the work.

I do in fact use the back cutting face as well. If I see my tram is slightly out, I use that to my advantage, as the return cut (without putting any further cut on) can just take 'wisps' of material off, and that is what gives you the mirror finish. I will run my fly cutter fairly fast, well above 500 RPM most times, but at a very slow feed.

Plus lubrication always works well, especially with ali, as that is liable to pick up on the cutter and swipe it across your nice mirror finish, I use WD40 for lube on ali, brass or phos bronze and cast iron doesn't need it, and for normal steels (I wouldn't recommend a fly cutter on really tough stuff) I just use normal water based coolant/oil mixture from a squeezy bottle. Basically, to obtain a very nice finish, you have to attempt to keep the removed material from being carried around to the next cut, so by using a lube, the fine swarf is thrown away by the liquid being thrown around by the cutter, the ones that require no lube, automatically eject from the surface by themselves.

Bogs

wongster · « **Reply #61 on:** September 15, 2010, 07:08:22 PM »

Thanks Bogs. I'll redo the grinding.

Regards,
Wong

Xldevil · « **Reply #62 on:** October 10, 2010, 12:31:46 PM »

Hello.
I did my first free hand fly cutter grinding today.Btw.,my first tool grinding ever.
I followed the "Bogs way" and after "only" 3 hours of intensive grinding, I succeeded

Then I tried the cutter on a piece of aluminum.The surface looks smooth and shiny.
Thank you, Bogs.
Ralph

luke_duke · « **Reply #63 on:** May 02, 2012, 09:32:36 AM »

Sorry for picking up the old thread.
I tried to grind one myself and tested it out. The result is really awful. I guess I missed something with the angles. In the drawing No.3 there is a angle of 10-15 degrees. But when i look at the last picture I can't see any angle. Could someone explain to me how the second angle is grinded? I spent a few hours figuring out how to do so.

Thanks in advance!

Luke

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