I want chips

[GavlarParticipant @gavlar]

I've had my lathe several years now, I am untrained, reletively inexperienced and have no real idea about sharpening HSS. As such, I've been using indexable tooling with varying results.

A recent thread here prompted me to order the Eccentric Engineering 'Diamond' tangential tool, which appealed to me because of the apparent ease of sharpening.

Having set the tool up, and turning a test piece of free cutting steel at various speeds, feeds and depths of cut I'm getting excellent results. I'm pleasently surprised by how much metal I can remove in one pass and the excellent quality of the finish.

Problem is, I'm getting ribbons instead of chips regardless of what I change, Clearly not ideal as I'm having to frequently stop and clear the birdsnest that's formed.

I do use cutting fluid but flow cooling, whilst possible, is not really practicle.

The cutting tool is ground flat as shown in EE's video so is it a matter of changing the profile of the tool or do I need to do something else?

Thanks, Gavin.

[GavlarParticipant @gavlar]

[Thor 🇳🇴Participant @thor]

Hi Gavin,

My experience with a tangential tool is much like yours but I don't get a "birds nest" of long ribbons while turning mild steel. May be because I tend to use carbide tipped tools for roughing and switch to HSS for the finishing cuts.

Thor

[egaParticipant @ega]

Gary at EE ground a chip breaker on the tool used in one of his videos. Try asking him for details or just experiment.

[Robert ButlerParticipant @robertbutler92161]

Ribbons take less clean up time than chips.

Robert Butler

[Neil WyattModerator @neilwyatt]

You could use a cut off wheel in a dremel type tool to grind a groove a couple of mm back from the cutting edge, or perhaps make some form of chip breaker from a bit of bent steel.

Neil

[Howard LewisParticipant @howardlewis46836]

If you are roughing, a momentary break in the feed will mean that the spirals are short.

Spirals indicate a steady feed rate.

You don't want "clock springs" whirling round with the chuck!

Likewise, I tend to use a carbide tip for roughing and save the |tangential for the shallow finishing cut, with a fine feed. In this way the swarf, if spiral is fine. Sometime almost fuzz rather than spirals,

(A sharp, T T at centre height can take a finishing cut of less than 0.001" which doesn't produce much swarf

Howard!

[GavlarParticipant @gavlar]

I could carry on using the carbide for rough cuts, it's just that the TT seemed to move more material with less effort and a better finish than anything else I've tried.

I'll experiment with grooves in the tool over the next couple of days.

Thanks all.

[Paul LousickParticipant @paullousick59116]

As above, I use a carbide tool for roughing and the TT for the final cuts and don't have any problem.

[Clive FosterParticipant @clivefoster55965]

Tangential tools are inherently prone to continuous ribbon swarf because the cut material flows away relatively freely. The flip side of lower turning forces and good finish from the clean cut.

Chip breakers work by imposing a sharp bend on the ribbon swarf as it flows across the tool causing it to fracture. Cooling of the hot chip adds to the stress making fracture more likely.

The geometry of a tangentila tool makes it harder to generate a really sharp bend to promote fracture. On conventional flat tools a semi-circular (ish) groove immediately behind the cutting edge is a common way to a mke a chip breaker. Wasteful of tool steel as the whole groove has to be periodically ground away after a few sharpenings otherwise the tool has to be thinned down to the base of the groove.

An alternative, but not quite as effective is to put a sharp step close behind the cutting edge. Less wasteful of tool steel as the top remains at the full tool steel depth and the step can simply be moved back on resharpening. Especially if you don't use back rake along the length of the tool. For the depths of cut normal with smaller hobby lathes I'm skeptical of the value of such rake anyway.

A step is pretty easy to add to a tangential tool and is not wasteful of material.

Clamping an extra piece of thinnish steel above a conventional flat tool gives much the same chip breaker effect as a ground in step. Most economical on tool steel but you cannot use back rake and there is a risk the the chips could get under the separate piece, particularly so if the tool projection is significant. Although simple and pretty effective it's not a very common method, mostly due to the perceived risk of things going awry. Generally not suitable for common tangential type holders. Often old style top clamp carbide holders were arranged so the clamp acted like a chip breaker of this form. Easily done with the simple flat, usually triangular inserts that were common many years ago.

Clive

[MikeKParticipant @mikek40713]

Posted by Clive Foster on 24/02/2022 21:40:40:

Clamping an extra piece of thinnish steel above a conventional flat tool gives much the same chip breaker effect as a ground in step.

Clive

This is a good idea. I'll have to try it.  And it sounds just like the chip breaker of a hand (wood) plane.

Edited By MikeK on 24/02/2022 22:47:02

[Paul LousickParticipant @paullousick59116]

A bit difficult to add a chip breaker plate to the top of an Eccentric Engineering  tangential cutter. Grinding a groove behind the cutting edge could work but would have to be done each time after re-sharpening. (easy, quick sharpening with the supplied jig is an advantage with these cutters)

Carbide inserts for the lathe are available with and without a chip breaker. Those without can use a bolt-on chip breaker as shown in this Youtube video. **LINK**

Also a lot of different QCTP holders, demonstrated by Joe Pieczynski

Paul

Edited By Paul Lousick on 25/02/2022 06:38:03

[HopperParticipant @hopper]

A couple more things to try with your standard Tangenital Tool first.

Often if you really up the feed rate considerably, even if it means taking lighter cuts, the thicker swarf will break up into chips.

And it may help to vary the angle of approach between the cutting edge of the tool and the job. If you have the tool pointing straight in, so the cutting edge is at 45 degrees to the direction of feed, you are more likely to get coils than if you rotate the tool shank so the cutting edge is at right angles to the axis of the lathe.

The grade of steel you use can have an influence too. As can the diameter and the rpm. For HSS tool with mild steel job, aim at 100 surface feet per minute. That is 400rpm for 1" diameter job. 800 rpm for a half inch diameter job. 200 rpm for a 2" diameter job.

Coolant is unlikely to make any difference to chip form vs coils.

[Clive FosterParticipant @clivefoster55965]

As Hopper says chip breakers are primarily for breaking up thicker swarf. On industrial size lathes taking industrial size cuts the thick birds-nest effect can be very dangerous. Thick, stiff razor sharp random coils take a deal of unwinding.

If you do put a simple chip breaker on a tangential tool it just goes straight down as you re-grind so its not wateful. Needs a steady hand to keep it in the same place tho'. I imagine one of the thin angle grinder cut off wheels would do the deed nicely but I'd want a jig.

Adding a step needs a proper jig to put the narrow faces in front of it on.

I suspect that you still won't get nice chips. Snail shell roll seems more likely. Something I often get with a parting tool. Such rolls periodically break off when they become too large. I suspect that on most of our size jobs the roll will break at the end of the chip rather than becoming large enough to break mid cut.

Clive

[Anthony KnightsParticipant @anthonyknights16741]

Curley swarf can be a problem. I tend to use an interrupted manual feed to break the curls up into smaller pieces. About time to clean the machine I think.

Edited By Anthony Knights on 25/02/2022 09:12:33

[SillyOldDufferModerator @sillyoldduffer]

Although tidying up long ribbons is a pain I'd rather not have chips! Run hard and fast with carbide insets my lathe produces them in an unpleasant smoking hot spray. Whilst the metal removal rate is impressive and chips don't cause tangles, ribbons are more civilised.

At my work rates a commercial HSS cutter with a built-in chip-breaker rarely produces chips. I'm sure it would work if I cut more aggressively but doing so calls for flood cooling which I avoid because of the mess.

Dave

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