Slitting Saws?

[Bo’sunParticipant @bosun58570]

Good afternoon All,

A question for you knowledgeable folk.  I have a 2mm x 100mm x 130T slitting saw, purchased from an established supplier.

How much peripheral runout is considered acceptable?

I’ve checked it using a dial indicator with an “elephants foot” stylus and measured 0.55mm (TIR) runout.  This was replaced by another, (that I asked to be checked before despatch).  Using the same method, the replacement saw measured 0.35mm (TIR).

The slitting saw was mounted on a stub arbor with 0.03mm runout at the slitting saw position.

I welcome comments on my method of measurement.  I wasn’t sure how else to do it.

[JAParticipant @ja]

This subject has been discussed at great length twice this year.

Simply, eccentric running of slitting saws is the norm.

It would be nice if someone would gather the postings together, write something and send it to the ME. You may even get some money!

JA (being a bit of a killjoy)

[BazyleParticipant @bazyle]

That sounds terrible, 20 thou on a 4 in cutter. I would be looking for a thou or less on a new one. Must mearsure some of mine. When I hear it obviously not true I assume it is my arbor, collet, spindle.

[JasonBModerator @jasonb]

Although your arbor is 0.03 what is the fit of the saw like on the arbor? any slack

[Bo’sunParticipant @bosun58570]

Hello Jason,

The saws appear (to me) to fit the arbor just fine.  No discernible slack, and quite close to slide on.

[BazParticipant @baz89810]

If it were mine I would be sending it back and asking for a refund.

 

[Clive Brown 1Participant @clivebrown1]

With the radial runouts mentioned by the OP, only a few teeth will ever do any cutting.

[Bo’sunParticipant @bosun58570]

That’s correct Clive.  Initially looking at it by eye, it did appear to be running out somewhat.  So I tried a cut, and yes, it was by the sound of it, only cutting on a few teeth per revolution.

Why on earth did I pay for the other hundred or so teeth?

[JasonBModerator @jasonb]

Thay may come in useful once you have worn the first few down😉

[Michael GilliganParticipant @michaelgilligan61133]

To save overloading the poor little site search facility …

This should be a reasonable place to dive-in:

https://www.model-engineer.co.uk/forums/topic/sharpening-fine-tooth-slitting-saws/#post-472610

MichaelG.

.

Edit: __ Should was obviously the most relevant word … the hyperlink in that post doesn’t work !!

[bernard towersParticipant @bernardtowers37738]

Sorry but runout is down to your arbor, I have several and the only ones which are right are taper fit and cost decent money.

[JasonBModerator @jasonb]

Bernard, can you explain how an arbour that clocks at 0.03mm will give a run out of 0.55mm at the saw’s edge if it is a good fit on the arbour?

[Roderick JenkinsParticipant @roderickjenkins93242]

I have a large-ish selection of slitting saws made by various old school Sheffield manufacturers and they all, without exception, exhibit the pulsing sound when cutting which seems to suggest run-out even when running on my home made taper fitted arbors with imperceptible run-out.  I would have thought any half decent grinding machine would result in an undetectable difference in tooth grind.  Bandsaw blades are available with all sorts of tooth variations – skip tooth and variable tooth pitch to improve their cutting ability so it occurs to me that slitting saws may be designed to have a variable cutting action…

Rod

[bernard towersParticipant @bernardtowers37738]

Crap saw

[Mark RandParticipant @markrand96270]

A couple of thoughts.

While one could make an adjustable arbor a-la Bernerd Griptru chucks, it wouldn’t be practicable on a horizontal milling arbor.

Could one sacrifice the relief on the ‘high’ teeth by running the blade backwards against an abrasive to true up the teeth? Would there still be acceptable cutting performance after such an ‘adjustment’?

If the length of cut isn’t excessive, then one can bury the cutter far enough into the work to get all of the teeth working, so long as the gullets don’t fill up.

I must admit that I either take the last option, of possible, or just live with it.

[bernard towers]

On bernard towers Said:

Crap saw

Lots of mine are the same. Just put up with it

[JasonBModerator @jasonb]

Thinking about Mark’s Grip True comment you could identify the high teeth using the existing arbor. Then make a 1/2″ shank arbor to mount in a boringhead, set the high teeth along the axis of adjustment and then you could dial it in using the boring head.

Write on the saw what setting was needed on the BH and next time it can be mounted and used at that setting.

I think we all get the ching-ching-ching noise but the RDG ones the OP has seem particularly bad, not measured any of mine but expect they are something like 0.1mm run out.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I have a good number of slitting saw, from bog standard ones to good brand names, and I’ve never found one that actually runs dead true, even brand new cold saw blades I’ve used in my day jobs, seem to to have a little run out. However, run out or not, during my observation, all the teeth cut.

Regards Nick.

[JasonBModerator @jasonb]

I would expect a cold saw blade to use all the teeth as the spindle can ride up and down as you apply pressure. But if the feed rate is lower than the run out of a saw in the mill then the “low” teeth are unlikely to make contact.

[Neil LickfoldParticipant @neillickfold44316]

I just measured some that I have just with a caliper from the inside of the hole to the teeth in a few places. Looks like they are about 0.05mm or so different. That could make essentially a 0.1mm run out. I have never been bothered by the radial run out, only the swash runout or the sideways movement is my main concern. Being careful not to overload the teeth is the main thing about using a slitting saw. I am sure mine are not 0.5mm out though. That does seem to be alot of offset.

You could make an undersized arbour, and using an Oring to give it some grip onto the saw blade. Then tighten it so it can be moved, and running a dti with a protecting piece of brass or plastic shim, dial the saw to true, then tighten in place. Is another option to look at.

When I used to set up a set of blades and used as a gang saw, never took a lot of notice about the runout. We normally feed it fairly slow to get the bottom surface looking nice on the back pass.

Have you measured from the centre to the teeth in a few places to see what you are getting?

 

[Neil Lickfold]

On Neil Lickfold Said:

Have you measured from the centre to the teeth in a few places to see what you are getting?

Good morning Neil,

No I haven’t tried measuring like that.  I’m not sure how consistent I will be, but should be able detect some variation, considering the degree of runout.  I’ll give it a shot later today.

 

[John HinkleyParticipant @johnhinkley26699]

It seems to me that most, if not all, the slitting saws readily available to the amateur are going to have a little eccentricity.  So, instead of fruitlessly casting around for the “perfect” saw, why don’t we attack the problem from a different perspective?  By that, I mean devise some sort of floating head drive mechanism to provide some sideways movement of the saw blade as it turns, under the controlled restriction of a spring arrangement.  It would not need to accommodate very much radial movement, if the run-out figures quoted in the above posts are anything to go by.  I believe that a similar arrangement, albeit without the spring, is used in tapping heads to account for minor deviations in spindle and hole alignment.

Better get my “thinking head” on, methinks!

Maybe someone in possession of such a tapping head could make up a mini arbor to fit in it, to test my theory?

John

 

[Bo’sun]

On 2 August 2024 at 15:05 Bo’sun Said:

…  I have a 2mm x 100mm x 130T slitting saw, purchased from an established supplier.

How much peripheral runout is considered acceptable?

I’ve checked it using a dial indicator with an “elephants foot” stylus and measured 0.55mm (TIR) runout.

…

I welcome comments on my method of measurement.  I wasn’t sure how else to do it.

Accurate measurement is vital in manufacturing, and they go to considerable trouble to get it right.  Not, repeat not, simple and very easy to get wrong, especially when amateurs have a go!   Two major problems:

• Poor technique and equipment.
• Misunderstanding the results.

Accurate measurement is far less useful in a hobby workshop because we fit parts together by comparing one against the other rather than making them accurately and precisely within toleranced dimensions.

As inexperienced measuring is a rich source of confusion, I recommend keeping it in reserve.

Bosuns first test should be:  “does this slitting blade cut metal satisfactorily?  (Even if some teeth go clunk-clunk.)”

This is a real-world test that doesn’t rely on making an accurate measurement or understanding what the measurement means in practice.   After confirming that the arbour and saw are installed properly a blade that doesn’t cut can be sent back without further ado.

If the blade doesn’t cut properly, then careful measurement will eventually identify the cause.   But I recommend this as a second stage only used if absolutely necessary,  with the operator wide-awake to the possibility he’s doing it wrong!

I don’t know why, but slitting saws are often imperfect.  I suspect it’s because some teeth are ground slightly over-size, rather than the mounting hole being off-centre.   Hard to prove without a lot of very careful measuring.   If the cause is a few slightly protruding teeth, may not matter much.   Although they do more work than the others, all the teeth get a chance to cut as the saw is pushed into the job.  I see slitting saws as good for making slow precision cuts, not for quick hacking.

RPM and feed-rate are important too, and there’s a relationship between the number of teeth, the material, and the feed-rate.    Anyone got any advice on choosing the number of teeth needed?

Dave

[JasonBModerator @jasonb]

Yes unless the part is very thin or the cut shallow don’t go for lots of teeth. The 130T in question would really only be good for cutting thin sheet or slotting the tops of small eg M1.6 screws.

If you try and cut something that is too thick with a fine saw the gullet will fill with swarf, saw gets hot and goes pringle shaped and/or wanders.

 

[Bo’sunParticipant @bosun58570]

I take your point Dave.  And yes, accept that some degree of runout is to be be expected, or the reject rate from the manufacturer would be very high.  It’s the degree of runout that concerns me.  I don’t know what to expect as acceptable, and assuming my method of measurement is not wildly imperfect, 0.55mm, or even 0.35mm seems  excessive.

The slitting saw cuts a slot OK (in brass), but that doesn’t alter the initial question.  Assuming there’s an answer of course.

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