Tormach Flycutter with SEHT Insert

[Paul FallertParticipant @paulfallert28101]

Flycutting in steel

[Paul FallertParticipant @paulfallert28101]

I stumbled on to this flycutting demo ( I have nothing to do with this company). While the first part of the demo in aluminium was impressive (at least to me), the demo also performed well in 1045 steel, which is something I have tried to accomplish without hammering the spindle of my machine. I have followed the usual recommendations of restricting depth of cut to .25mm or thereabouts.

I could not see anything in the design of the flycutter that could not be replicated in a home shop. The SEHT insert (45&deg has been around for quite a while and it has been recommended for face milling on small and lower horsepower machines like many of us have.

The demo: https://www.youtube.com/watch?v=tCrJVYF95aE

Can anyone spot what is unique here, including speeds and feeds, that is making this flycutter perform so well?

Paul

[Paul FallertParticipant @paulfallert28101]

Sorry, wrong demo.

Here, hopefully is the correct demo:

**LINK**

[Bob RodgersonParticipant @bobrodgerson97362]

I have one of these fly cutters and it does perform well, especially on Aluminium. It produces a finish such that it is almost impossible to see any machine marks.

[Paul FallertParticipant @paulfallert28101]

Bob:

When you use the SuperFly on steel, is there hammering? Also, what type or class of milling machine are you using?

Paul

[Neil WyattModerator @neilwyatt]

Only that they will have experimented to find th best settings for the tool before using it.

And they have Super Fly Guy

Neil

[MuzzerParticipant @muzzer]

Haha, his eyes and nose look like "meat and two veg"! Perhaps a different kind of fly….

[egaParticipant @ega]

There is another video here:

The presenter suggests that the Superfly "could even be used on a Bridgeport" but how many amateur shops have one of those?

Edited By JasonB on 20/04/2017 13:30:48

[Paul FallertParticipant @paulfallert28101]

ega:

Thank you for that link.

At the very beginning of the video, it shows the insert is mounted with positive rake in both directions on the bar.

According to their literature, they use a different insert for steel (obvious, but a need to know, because there are reports that some model engineers are discovering that some highly positive inserts designed for aluminium are working very well on steel, too).

I am mainly interested in learning what if any is the secret to face milling steel with a fly cutter without hammering the spindle.

Paul

[Neil WyattModerator @neilwyatt]

Posted by Paul Fallert on 19/04/2017 13:04:04:

I am mainly interested in learning what if any is the secret to face milling steel with a fly cutter without hammering the spindle.

Getting the speed right. Most people run flycutters too fast.

Neil

[JasonBModerator @jasonb]

And keeping it sharp

[Paul FallertParticipant @paulfallert28101]

Neil:

Thank you for pointing that out, since I think this is one of the clues in their success. Their stated speed and feed for 1045 steel are 1,000 RPM, .025" DOC roughing and .005" for finishing and the feed is 10 ipm. The chips are light straw. They also used an air blast and NO coolant.

I don't have or know anyone who has a Tormach, so I don't know how to classify the Tormach compared to, say a BridgePort [which we had at adult VoTech classes. BTW, I purchased and used a 2", 3-flute TCMT facemill on a Bridgeport to cut carbon steel. Settings:1,000 rpm, .015" DOC, powered table feed set at maximum cutting carbon steel. The VoTech instructor took a dim view of that experiment because the smoking chips flew across the shop, but he admitted that he was impressed with TCMT running on a worn out BridgePort. My home millling machine does not have 3 hp and the negative TCMT hammers the spindle.]

On a job-shop machinist website I found several suggestions to use the SEHT insert for facing, whether in a multi-insert face mill or in a fly cutter. The reasons for using SEHT were stated as follows:

1) Competitive pricing (aka lower) and availability (aka old tech).

2) A #43 SEHT is thicker and can take a pounding (aka interrupted cut)

3) Positive insert design with chip grooves helps with the chip problems.

4) In machines with horsepower meters, the SEHT used a lot less horsepower than other inserts.

5) Flat-out statement that 45° (or round) inserts present a more efficient cutting face to the work and would be a first choice on low power light-weight machines.

I like to convert all cutter shapes to right-hand lathe tooling images. I compare the SEHT 45° cutting face angle to the recommended cutting face of an efficient lathe tool as recommended by MEW authors such as Harold Hall.

Many of us prefer not to use coolant in a domestic environment, but an air blast (even from an airbrush compressor) is worth consideration because it keeps the chips from being re-cut. Avoiding re-cutting does two things, increase cutter life and avoid fouling of the finish.

Any other clues?

Paul

[JasonBModerator @jasonb]

There are a few Tormech owners on her, Bob who replied earlier is one, I have added Tormech to the title and then Andrew J may well spot it and comment. I know he is not too keen on flycutters but does like his chips blue, he also has a Bridgeport so could give comments about the two machines..

[VicParticipant @vic]

I've got a standard fly cutter that takes 3/8" HSS bits but I made a holder so I can use 12mm round carbide inserts with it. It works ok for both steel and aluminium alloy but I normally just use HSS for the latter.

[Anonymous]

Posted by JasonB on 19/04/2017 16:09:04:

…………… I have added Tormech to the title and then Andrew J may well spot it and comment. I know he is not too keen on flycutters but does like his chips blue, he also has a Bridgeport so could give comments about the two machines..

I nearly missed this thread entirely; title should be Tormach.

It is correct that I am not a fan of flycutters, for several reasons. I almost never seem to get a good finish, they're slow, and flatter to deceive in that the finish might look nice, but isn't going to be as flat as using an endmill. Finally I'm nervous of the cutter, you can't really see it when rotating, so it would be all to easy to get caught up in it – which would be a bad day all round.

The comparison between the Bridgeport and Tormach is an interesting one, on several levels. They both use an R8 taper and are the same nominal spindle power, 1.5hp. The Tormach is about half the weight of the Bridgeport at 500kg.

The drives are different. My Bridgeport has two ranges ( one backgeared) and within each range uses a varispeed pulley system. So ignoring losses full power is available across the speed range. The Tormach has two belt driven ranges and within each range the motor is driven by a VFD. So below base speed (equal to 60Hz) the available power is reduced. The Tormach speed range is 100-5100rpm, while the Bridgeport is 50-3750rpm. I rarely run the Bridgeport above 3000rpm as the head is pretty noisy, whereas the Tormach is dominated by cutting noise, even at maximum rpm. While the Bridgeport is happy running large (>1&quot cutters and drills at a few hundred rpm the Tormach isn't. But of course with CNC you don't need to run large drills, you just interpolate the hole to any size you want. Although the Tormach requires a little more thought about available power in practical terms there is little difference.

In terms of axes, the Tormach has about half the travel in X, two thirds in Y and is slightly bigger in Z.

With regards to rigidity the jury is out. Compared to many industrial milling machines the Bridgeport isn't particularly rigid, although it is flexible (in at least two senses). I'd say that the Tormach rigidity is on a par with respect to the table movements. The spindle on the Tormach might be a little more rigid as there is no tilt function, although the column is smaller than the Bridgeport.

I tend to use slightly different techniques on each mill. For CNC it's very much run at high rpm and high feedrates with small (<10mm) cutters. Whereas the Bridgeport has the capability to run larger cutters at slow speeds. The Tormach has a sort of quick change capability, and I use the same system on the Bridgeport a lot of the time. So the experience of using the Tormach has modified, to some extent, the way I use the Bridgeport.

When I was purchasing the Tormach my hope was that it would be roughly equal capability to the Bridgeport in terms of metal removal. I think that this has proved to be roughly correct.

Which mill I use depends mostly on ease of setup, time to program and the complexity of the operation rather than basic machine capabilities.

Ramble over.

Andrew

[Ian PParticipant @ianp]

Andrew called his post a ramble, I disagree.

Its a pleasure to read a well written, sensible, and reasoned discussion about machine types. My mill does not have the metal moving features of the two mentioned but the points Andrew compared are relevant in principle to machines of all sizes.

So thanks

IanP

[Paul FallertParticipant @paulfallert28101]

Andrew:

I want to thank you for your significant comparison of the Tormach and the Bridgeport. My goal is to track down the clues of how the Tormach fly cutter.performs so well in steel.

The majority of us on this Forum who use a light weight milling machine have been told we should not use an endmill or facemill larger than 1". But, reports from the "field" suggest that there are ways to face steel with a larger tool on these lesser machines.

My quest is to learn the method (secret / trick?) so we may all benefit without destroying our machines. Many of us would love to have the finish on medium carbon steel being produced in that demo.

Would you be willing to view and comment on the Tormach demo with emphasis on the cutting of medium carbon steel 1045 (Iso C45), especially given your comment regarding the quiet running of the Tormach at higher speed? **LINK**

Are there any "tricks" being employed in the demo? Neil pointed to feeds/speeds ideal for the steel. 10ipm, 1,000rpm, .025" depth of rough cut and .005" finish cut, 2.5" diameter and usual stepover producing light straw color chips using a steel-specific SEHT carbide insert mounted double-positive on a square rod. No unusual characteristics of their fly cutter head (other than their TTS tool-to-spindle mount system).

Paul

Edited By JasonB on 20/04/2017 13:35:41

[JasonBModerator @jasonb]

Posted by Paul Fallert on 20/04/2017 13:22:46:

 

Are there any "tricks" being employed in the demo?

Looking at the link that Ega posted the cutter can be seen to be cutting on the back edge of the cut as well as the leading edge much like you would with an out of tram head. This means the backcut is putting a very fine finishing cut onto the metal probably less than 0.001" l think it was about 5.45 in when I was watching it yesterday.

Also looks to be doing the same on your video. Interesting that Andrew says the heads can't be angled so are they out of tram or is there some flex in the tool that is pushing it off on the leading cut and the trailing cut is removing whats left. It is far more appparent on Ega's link as you can still see large chips comming off after the leading edge is clear of the work.

On a well trammed machine I would expect to see an even pattern left by both cuts of the tool as it passes over the work

Edited By JasonB on 20/04/2017 13:35:22

Edited By JasonB on 20/04/2017 13:39:15

[VicParticipant @vic]

On small pieces of work it's possible, with a large enough fly cutter to get a nicer finish (I think) by only traversing the cutter half way over the work. This stops the "double hatching" effect seen in Jasons picture. I've also deliberately fed the workpiece under the cutter at a fairly high speed to give a "textured" surface finish on some occasions. The only downside for me of fly cutters is that they throw chips all over the place!

[Bob RodgersonParticipant @bobrodgerson97362]

Paul, I should have answered your question ages ago but I've been a bit busy lately. I am using a Tormach mill and kept the speeds high and feed moderate with a shallow depth of cut about .020" for roughing and .002 for finish cuts. I used coolant too.

I used the tool on some EN24T and found that it cut OK but there was some slight Hammering and it was slower than using a face mill so I reverted to using that for steel.

[Paul FallertParticipant @paulfallert28101]

I want to thank each of you for your valuable contributions to this thread.

Is it the machine, the fixture, the insert, the feed/speed or all of the above?

Tormach did not use coolant (maybe because a fly cutter would flood the operator and not only with chips)?

Focus on the insert:

Anyone have experience with the SEHT insert on steel?

Paul

[Anonymous]

I had a look at the Tormach video this afternoon. I don't think they're doing anything particularly special. However, I think that the key factor may be spindle speed.

As far as I can tell 1045 steel is roughly equivalent to EN8, except that it contains some silicon. In my turning trials a while back I found that the finish on EN8 was very dependent on cutting surface speed. See towards the end of this page:

**LINK**

A tool tip running at 1000rpm on a 2.5" diameter circle has a surface speed of around 654fpm. In my turning trials the finish improved out of all recognition at 511fpm compared to 340fpm. Makes yer think!

Andrew

[Paul FallertParticipant @paulfallert28101]

Andrew:

That disclosure supports Neil's hypothesis that the demo was built around special characteristics of the material that was selected.

Paul

ps: I found these comments on the cnccookbook.com website which relate to 2/or 3 of the comments above:

Flycutters Can Give Better Finish than Face Mills, But Why? Answer: Runout.

… fly cutters can give the best possible finishes (albeit at slower speeds), but why? I found the answer in some Ingersoll literature where they suggest removing all but one cutter from a face mill if finish is paramount because this converts the facemill to a flycutter which has no runout.

Like most mill cutters, your fly cutter will perform better with positive rake on the cutting tool. SEHT = a positive rake insert and the Tormach tool (stick) in the demo has the insert mounted double positive in the pocket.

From <**LINK**>

[Paul FallertParticipant @paulfallert28101]

I have located two videos that may provide some additional clues / or ideas.

#1 Author: Tintek33 (uses subtitles) makes his entire flycutter and tool bar and he tests the results.

Insert: CCMT lathe insert, but using the two unused 45 degree tips.

Material cut: Aluminium and “iron” [may be a translation problem]. The “iron” looks like steel.

Results: Excellent.

Warning: Tintek’s methods are “artistic”, but you can’t knock the results. Example: He mounts his shop-made fly cutter in a drill chuck and runs his mill at the max of 2,900 rpm.

Steel fly cutting clue: 2,900 rpm and positive rake insert mounted in a double-positive rake pocket (very difficult to even guess at the angles he used).

**LINK**

———————

#2 Author ScPatent – makes a dovetail “fly” cutter, and first attempt is a failure, but he then achieves success by “sanding” [may be a translation problem] relief/clearance? from side of insert. 2900 rpm and 13 ipm. Nice result in steel! So you may ask, why did he not rework the pocket with more rake, and I think the answer has to do with his attempt at making this a fly cutter to mill a dovetail. If you increase the rake angle of the insert, you change the milled angle away from his 60 deg. dovetail. For those of us, seeking to make a fly cutter for facing steel, this would not be a problem. He does use a readily available insert and achieves excellent results on steel.

Insert: TCMT – 60° triangle with 7° [side] relief angle". [The “C” in TCMT means only 7 deg side relief, whereas a “P” as in TPxx would have 11 deg relief.]

Workpiece: STEEL 42CrMo4

Results: Excellent

Clue: Another 2,900 rpm adherent.

**LINK**

Comment from a viewer: “no support for the inside margin of the insert other than the cutting edge touching the insert pocket.

From ScPatent: That is cold rolled steel I am machining… I have toxicated my self with aluminium, so I don't want to work with aluminium any more…[he works in a health related occupation].

Off topic: WHAT DOES HE MEAN BY “TOXICATED MYSELF WITH ALUMINIUM” ?

[MuzzerParticipant @muzzer]

I think it means he hasn't bothered doing any research to see what real ones look like. Call it copying or benchmarking but there's a lot to be gained from analysing and understanding what's already out there before cutting metal or designing your own take on it. The quote seems a bit unfair on aluminium though.

Murray

[Author]

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