Flycutters: help to understand 3 different types

[JasonBModerator @jasonb]

You don't need to stop at dovetails, any profile can be done as the flycutter is really just a single point tool, I have also done dovetails though single sides.

[John BaronParticipant @johnbaron31275]

I agree ! All sorts of things can be cut with a flycutter.

This is a couple of pictures of a dovetail slide that I made that way. The really hard part was making sure that both the male and female parts fitted together properly.

I admit that I did cheat a little. After making the male half, I took a slice off the end and used it as a template when making the female half. They are a nice fit and slide together well.

The brass screw on the left of the top picture is for locking the slide.

The screw on the bottom picture drives the two parts.

 

Edited By John Baron on 07/12/2018 12:10:44

[not done it yetParticipant @notdoneityet]

Posted by John Baron on 07/12/2018 12:09:38:

… The really hard part was making sure that both the male and female parts fitted together properly. ….

Well done, but isn’t that what Gib keys were invented for? One side could be made as a straight edge if the key was retained in the other plane. An infinite number of attempts could then be made to make the key at just the right shape.

[Mick B1Participant @mickb1]

Posted by BW on 07/12/2018 03:40:29:

Thanks a lot for all of the tips and especially the photos – really helpful to see what others have done. Especially that one by Mick, thats amazing – would never have dreamed of trying that.

….

Bill

Edited By BW on 07/12/2018 03:40:59

Well, thanks for the nice words there. I videoed the second-to-last pass with that overextended flycutter. The component fitted after one more cut of 2 thou.

https://youtu.be/vUaw62Vlo1c

 

One of the joys of engineering to me is managing to do summat close enough to what I want, with whatever I happen to have.

 

Of course, I reserve the right to be less forthcoming about demonstrating my failures…

Edited By Mick B1 on 07/12/2018 15:02:20

[John BaronParticipant @johnbaron31275]

Posted by not done it yet on 07/12/2018 12:57:13:

Posted by John Baron on 07/12/2018 12:09:38:

… The really hard part was making sure that both the male and female parts fitted together properly. ….

Well done, but isn’t that what Gib keys were invented for? One side could be made as a straight edge if the key was retained in the other plane. An infinite number of attempts could then be made to make the key at just the right shape.

I agree ! But at the time I had only recently got the mill, so it was very much an exercise to see if I could make one. I've had a Myford S7 for a long time, so making a suitable fly cutter was the easy part.

[BWParticipant @bw]

Posted by John Baron on 06/12/2018 19:17:23:

Hi BW,

This is one of mine. 3" inches in diameter, 20 mm thick, 20 mm spindle. A heavy rigid body and spindle. Well balanced, and a good flywheel effect. Particularly important if making interrupted cuts. I can take a 1 mm DOC in mild steel at a 150-200 rpm. The tool bit in this one is 5/16" square HSS.

Edited By John Baron on 06/12/2018 19:19:27

Hello Again,

Tried to copy what John Baron did. Didnt get any mirror finishes – more like a dirty smeary streaky mirror.

Think I am feeding too fast (2.5mm in 8 seconds ? ) and not enough rake on tool, tried 2 different tool grinds but didnt seem to make any difference. Slight difference when I slowed the feed right down _ am using manual feed is that ok ? Finish on Al (short squat lump in photo) seems better than finish on hot rolled steel (long thin lump in photo)

Tried varying rpm from 125 to 300 but not much effect – cut diameter is 2.5"

Will have another go tomorrow – reminds me of my initial attempts at getting a nice finish on the lathe – took me a couple of years to get a good finish with a round nose tool – shear tool and turning a knife tool around to rub worked fine but round nose tool was always awful for me. Maybe I gotta go back and learn how to grind tools properly.

[John BaronParticipant @johnbaron31275]

Hi BW,

Very good effort !

First thing I noticed from your first picture, you have far too much tool stick out. Rigidity is the thing here. I also notice that you have the spindle secured with two nuts. Whilst its hard to see on the picture of mine there is no spindle below the bottom of the disc. The spindle on mine was pressed into a bored hole, and I also used superglue to make sure that it did not move. Whilst not absolutely required, I also faced off the underside whilst holding the spindle in the lathe chuck.

I did a lot of playing about with tool bit shapes. The rounded edge seen protruding through the disc is the one that I use for alloys. There is only about five or six degrees of rake and the front face is virtually flat.

The toolbit for cutting steel is quite hooked. I basically copied my lathe tools.

Last thing ! Check your mill tram. Under ideal conditions you don't want the cutter taking more off on one side, this is most noticeable on a long cut when cutting in one direction and the cutter is taking a shave off at the other side.

[BazyleParticipant @bazyle]

Don't forget the direction of cut is sideways. With a round tool it is easy to end up setting it to negative rake.
Your speed is 125rpm and for a finishing cut you want 1-2 thou per cut. so 125×2= 250 ie 1/14 inch per minute.You have been traversing a bit fast.

[JasonBModerator @jasonb]

125 is a bit slow, I'd be 5-700rpm on the ali and the skin of the hot rolled may have taken the edge off the tool.

Feed wise at my speed roughly 1 turn of the handwheel per second which equates to 150mm /min

Splash of paraffin or WD40 will help too

 

Edited By JasonB on 09/12/2018 13:51:13

[Ron LadenParticipant @ronladen17547]

The flycutter I finished this morning, 40mm diameter, 16mm shank, 20 degree angle tool mount, fitted with an ARC HSS tool bit.

Gave it a test run and it cuts really nice, tried it on some 6082 and I couldnt want for a better finish, very pleased with it. Ran it at 650rpm and feed wise I couldnt tell you but it was steady, I tend to go with what feels and sounds right.

[Ron LadenParticipant @ronladen17547]

Seeing Jasons figures I roughed out the feed rate I used timing the turns of the handwheel as I used on the test piece. I was running a bit slower at approx one turn per one and a half seconds so somewhere in the region of 100mm per minute.

[Bob YouldonParticipant @bobyouldon45599]

Good afternoon,

One of the most useful tools in my workshop is a little fly cutter made to a design that appeared in the Live Steam magazine many years ago, it's probably no more than 3/4" diameter and give about a 7/8" diameter sweep with a 3/16" square HSS tool bit. I use it for finishing cuts taking off no more than .001" at about 1600 rpm with a dead slow feed results in a finish like a surface grinder! Wonderful.

Regards

Bob

[JasonBModerator @jasonb]

Popped one of ARC's new flycutter bits into a 2.5" head so swinging a similar 3" radius, 800rpm 0.1mm DOC and about 100mm/min feed finishing cut. Not too bad, maybe the mirror is a bit steamed up but could not be bothered to play about with it any more.

BW, I would say you have too big a curve on that tool which can cause it to start chattering, if you look at John's one I would say the cut is being made by that small angle on the corner of his toolbit rather than the bottom. I'd grind yours more like a lathe tool say 10 degrees across the botton and the edge 90degrees to that then just lightly stone where they meet for finishing cuts, heavy metal removal just leave as ground.

 

Edited By JasonB on 09/12/2018 16:56:25

[Ron LadenParticipant @ronladen17547]

A good cutter and the right combination of speed and feed certainly can produce a good finish, pleased with what I got.

A question: how will a HSS bit cope with flycutting silver steel, thought I would ask before I try.

[JasonBModerator @jasonb]

Should be OK, just a little harder going than a low carbon steel.

[not done it yetParticipant @notdoneityet]

It might, or will, depend on the hardness. Is your steel in the annealed state or hardened?

[JasonBModerator @jasonb]

Well I was assuming Ron would be machining it in the supplied annealed condition which it is usually sold in.

[BWParticipant @bw]

Hello Again,

Yeeha ! I got a reflection in Aluminium ! Chuffed !!!

Rong Fu 30 Round Column Mill 2HP Motor

Aluminium Block Unknown type of Aluminium, Plenty of WD40 whilst cutting.

400 rpm approx 2.5"diameter cut 8 seconds per 2.5mm so = 80 seconds/inch = 0.75" per minute approx 0.001" doc – thats extremely slow feeds/speeds comparted to Jason's . WIll do some variations to better understand things.

Shortened the stickout to approx 0.5" (and yes I was getting chatter on the long stickout and shorter radius curve on tool – some interesting patterns & could hear it squeal). Need to do something about those 2 nuts before shortening stickout further.

Re-ground the tool to a much flatter curve as suggested by Jason.

Wasn't able to get as nice a finish on black bar – although it looks horribly corrugated it is actually quite smooth to the touch – cannot feel the corrugations with fingertips – do the corrugations indicate I am feeding too quickly ? Haven't quite got a reflection on the black bar.

Nevertheless, this is the best finish I have ever achieved on my mill with both black bar and aluminium. Think I just need to play around a bit and better understand speeds feeds and grinds.

Will try the "conventional" flycutter next.

Many thanks for all of the help/tips/photos in this thread.

Hey Ron Laden,

I cannot figure out which part of your cutter contacts the work and cuts it, your bottom edge looks almost horizontal to me.

Thanks Again,

Bill

[Mick B1Participant @mickb1]

Posted by BW on 10/12/2018 10:18:56:

…

I cannot figure out which part of your cutter contacts the work and cuts it, your bottom edge looks almost horizontal to me.

…

I thought the same on looking at the pic. I'd want to back off the bottom edge to give it a bit of trail clearance angle and prevent the trapping of bits of swarf against previously-cut surface. But then the flycutters I use in the lathe are very much less rigid.

[JasonBModerator @jasonb]

When fitted to an ARC flycutter body their toolbits give about 5deg clearance. And that is what I used for that photo posted yesterday.

[Ron LadenParticipant @ronladen17547]

Posted by Mick B1 on 10/12/2018 10:55:36:

Posted by BW on 10/12/2018 10:18:56:

…

I cannot figure out which part of your cutter contacts the work and cuts it, your bottom edge looks almost horizontal to me.

…

I thought the same on looking at the pic. I'd want to back off the bottom edge to give it a bit of trail clearance angle and prevent the trapping of bits of swarf against previously-cut surface. But then the flycutters I use in the lathe are very much less rigid.

It does look like that in the previous picture but the picture below shows the angle with the tip touching the surface of the work piece. It is shallow and this is the standard ARC tool (unmodified) fitted to the seat which I put in at 20 degrees. I could mod the cutter or it would be simple to add another 5 degrees to the seat but I,m not inclined too as it flycuts just fine, I had no issues with swarf.

[Mick B1Participant @mickb1]

Posted by Ron Laden on 10/12/2018 12:57:31:

Posted by Mick B1 on 10/12/2018 10:55:36:

Posted by BW on 10/12/2018 10:18:56:

…

I cannot figure out which part of your cutter contacts the work and cuts it, your bottom edge looks almost horizontal to me.

…

I thought the same on looking at the pic. I'd want to back off the bottom edge to give it a bit of trail clearance angle and prevent the trapping of bits of swarf against previously-cut surface. But then the flycutters I use in the lathe are very much less rigid.

It does look like that in the previous picture but the picture below shows the angle with the tip touching the surface of the work piece.

…

Ah, yes, thanks – that's what I'd do. I smooth the point rad with a medium India oilstone and usually get a shiny finish, like on the fishes in my album or the valve face here:-

**LINK**

[Ron LadenParticipant @ronladen17547]

I had a go at cutting the silver steel with the HSS bit, it cut it ok and didnt struggle but I didnt manage a decent finish, it was not that bad but not as I would want. I tried various speeds and feeds and was only taking light cuts but I gave up and changed over to a carbide tip, wound the speed up and it transformed it as you would expect.

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