Slitting Saws?

[Michael GilliganParticipant @michaelgilligan61133]

Good analysis, Jason

Personally, however, I remain much more interested in how some of these cheap saws come to be so badly made … at the moment this is a purely intellectual exercise for me [because I have no facility to use the ones I already own]

If we can get to understand that … it might help us identify what features typify the bad-uns.

MichaelG

[JasonB]

On JasonB Said:

The problem of “not buying cheap” is not easy for many.

If I understand it correctly the OP bought a cheap slitting saw that didn’t actually work properly. In essence he wasted his money so I don’t see how that helped save money by buying cheap.

It is, of course, not possible to quote a number that defines cheap. It’s a matter of judgement on price/performance. But that line is not linear. At the bottom end there comes a point where the tooling doesn’t function properly, so the fact that it is cheap is irrelevant,it didn’t do the job so the money is wasted. Just as important time is wasted which also has a cost.

Andrew

[JasonBModerator @jasonb]

Unground parts of the teeth/gullet may be one feature to avoid but unlikely to show on any online site particularly the fine toothed one like the OP bought, so hard to avoid if web shopping. Though I can’t find them on their website today!

[JasonB]

On JasonB Said:

They are about all Ihave used for the last few years as my imperial ones don’t get much of a look in these days.

2mm saw cutting 1/4″ brass. Two different power feed rates than a one handed hand feed. Not easy to turn the spindle one handed and I just did random teeth but I would say it runs to 0.0002″ or 0.005mm and that is on the end of a fairly long arbor.

Hello Jason,

That’s very good, much better than I would have expected for the price.  Hats off to Ketan.  It’s a shame ARC didn’t have a 2mm saw to fit my 1″ arbor.

[JasonBModerator @jasonb]

It was a rare occasion but I did make an adaptor so I can mount the metric ones on the MT3 arbor that I use on the X3, video was with the ARC arbor in the SX2.7.

A bit less rushed this morning and I would say it could be a bit more eccentric about 0.01mm but that is still a big improvement over what you have.

Interesting to work out the cutting speeds and chip loads. For that second power feed cut that was the faster of the two I make that about 150mm/min feed @350rpm.

It’s a 24T blade so that works out at a chip load of 0.018mm (0.0007″) which is more than the eccentricity of the blade so all will be cutting to some extent and it did sound better as did the first when I wound up the power feed a bit more part way through the cut.

For something like your clevis it would not be that easy to feed in at such a rate and then stop at the right depth. A better option would have been to set the depth of the slot by touching off against the end of the work, feeding in as required and then making the cut in the Y direction where you can wind away at speed and not worry about when to stop as you are just passing right through the metal.e

[KEITH BEAUMONTParticipant @keithbeaumont45476]

I have long since thought that this is not a quality problem and that there is a reason other than sloppy manufacture for the concentricity with slitting saws. In spite of all the traffic, no one has appeared to say, I buy from “x” and they are allways perfect.  This morning I phoned the Company in Michael’s link,of a few days ago and asked to speak to a technician regarding concentricity. He was very helpful, but assured me that they work to the British Standard of +/- 0.001″ on concentricity,across their whole range. He said that when they get complaints on this subject,it is always down to the machine or arbor having run-out.

So it would seem to be a quality thing and we know where to buy them if we want perfection!

Keith.

[Andrew Johnston]

On Andrew Johnston Said:

On JasonB Said:

The problem of “not buying cheap” is not easy for many.

If I understand it correctly the OP bought a cheap slitting saw that didn’t actually work properly. …

Andrew

Not so.   I specifically asked Bosun if the saw cut, and he replied ‘Both slitting saws seem to cut OK (to me anyway), apart from the ching, ching, ching…‘

Bosun’s opening post said he has two saws, with 0.55mm and 0.35mm run-out.   Though that seems a lot to me, it doesn’t appear to matter much!  Low run-out may be highly desirable in drills and milling cutters, but this is a saw.   Do slitting saws need to be perfectly round?

Dave

 

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Keith … Your telephone call was evidently the right approach, as I have not yet received any reply to the eMail that I sent to them on Sunday evening.

MichaelG.

[Andrew Johnston]

On Andrew Johnston Said:

On JasonB Said:

The problem of “not buying cheap” is not easy for many.

If I understand it correctly the OP bought a cheap slitting saw that didn’t actually work properly. In essence he wasted his money so I don’t see how that helped save money by buying cheap.

It is, of course, not possible to quote a number that defines cheap. It’s a matter of judgement on price/performance. But that line is not linear. At the bottom end there comes a point where the tooling doesn’t function properly, so the fact that it is cheap is irrelevant,it didn’t do the job so the money is wasted. Just as important time is wasted which also has a cost.

Andrew

That is one reason I said it is not easy, the ARC ones at almost the same price would also seem Cheap, yet they or at least the ones I have are several magnitudes better. Infact if you compare the cost of 80mm dia ones between the two suppliers the ARc ones are less expensive.

They may also have difficulty in justifying spending £50 or more on a saw blade that may only get used once every few years in a hobby enviroment. But they could keep the RDG one, buy an ARC or other reasonable one and still have a lot of money left so buying cheap and buying twice would have still been a better financial option.

[SillyOldDuffer]

On SillyOldDuffer Said:

[…] Do slitting saws need to be perfectly round?

 

Nothing made by mankind is perfectly round, Dave

What matters is whether they are good enough to do the job sufficiently well.

… did you watch the video that I linked this morning ?

That final cut, with what’s effectively a home-made blade, is impressive.

MichaelG.

[Neil LickfoldParticipant @neillickfold44316]

Cutter grinders are not cheap, like what was in the video link. They do allow for custom tools though that can sometimes be an advantage. Slitting saws and side face cutters are almost a forgotten tool. Sometimes you can get bargains from auctions etc where often the saws and side face cutters are almost not bid on.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, well out of curiosity, I checked my arbore for runout, and it has in one spot, 0.00025″/ 0.00635mm high, which I’m not going to worried about. I mounted an Arc 42 x 1/16″ x 34T slitting saw, which has never been out of the thin poly bag, let alone never been used, and has no shake at all on the arbore, and I then checked the teeth in the same way as JasonB has shown, after getting my dial gauge to 0 onto one of the teeth, and then turning the spindle slowly by hand, I got a variation  of some of the teeth not quite making the needle reaching back to the 0 position, while others moved it to almost 0.0015″ / 0.0381mm past the 0 position, some of these readings were in-between each other, while some came in pairs, but at least two teeth, not even close to each other. only just moved the the needle, I rotated it at least three full turns, and the readings were very much the same each time. I have no problem with these results either, and I’m very confident that it will cut okay when it gets used.

Regards Nick.

[Michael Gilligan]

On Michael Gilligan Said:

On SillyOldDuffer Said:

[…] Do slitting saws need to be perfectly round?

 

Nothing made by mankind is perfectly round, Dave

…

True, but my point was ‘how round does a slitting saw need to be?’   I think the answer is ‘not very’, and that seems to be the forum  consensus.  Most of us are using eccentric slitting saws successfully.

I suspect expensive saws have longer lives when heavily used because being rounder means the teeth wear evenly.  But that means paying extra for them is unlikely to deliver value in a home-workshop unless they really are used a lot.

Those who only do occasional light slitting should buy cheap and spend the money saved on something else!   Otherwise one is liable to spend hundreds on a saw where the only benefit is it doesn’t go ‘ching ching’.

Haven’t watched the video yet!

Dave

 

 

 

[JasonBModerator @jasonb]

I’m not sure that slitting saws are a forgotten tool, I seen several videos of 5 axis machines making small parts and all are held in the compact self-centering CNC vices and the last op is to “part off” with a pass or two of a slitting saw to leave a wafer-thin piece of metal allowing the part to simply be broken off.

I have linked to this one before, the saw blade is about £500 plus whatever the arbor costs.

 

 

[Bo’sunParticipant @bosun58570]

Jason,

Referring to you post earlier.  I did cut the clevis slot on the Y axis, but it was somewhat painful with around half a millimeter of runout.

While it did the job, it’s still disappointing.  Especially when other suppliers (or at least one) can clearly do considerably better for around the same price.

[SillyOldDuffer]

On SillyOldDuffer Said:

I specifically asked Bosun if the saw cut, and he replied ‘Both slitting saws seem to cut OK

All I can say is that Bo’sun and I must have very different expectations!

The results from Nicholas Farr are what I would expect from a reasonable slitting saw in terms of eccentricity. A slitting saw is a milling cutter and there is no reason why it should be made to a lower standard than other similar cutters such as S&F.

The chip loads mentioned by JasonB seem very low to me. For reasonable width cutters (1mm upwards) I’d be nearer 3 or 4 thou per tooth.

On the Bridgeport, with an unsupported arbor, slitting saws tend to wander off. On the horizontal mill, with an arbor supported on both sides, a slitting saw will cut a groove that does not wander, less than 0.02mm over a 450mm length. So the issue of wandering is more to do with how the arbor is supported than the saw itself.

Andrew

[Bo’sunParticipant @bosun58570]

Andrew,

Yes, they “seem to cut OK” in as much as I ended up with a slot in a relatively small piece of 1/4″ dia brass.  How they’d fare in something larger and somewhat tougher is anybody’s guess.  You’re quite correct in relating slitting saw standards to S&F milling cutters, but that’s where in this case, cost clearly enters the discussion.  However, around half a millimetre of runout, even in an inexpensive cutter, seems excessive.  Even if I’m being generous, I still have over 100 teeth not doing anything.

[Bo’sun]

On Bo’sun Said:

…around half a millimetre of runout, even in an inexpensive cutter, seems excessive.

No question about that, it is totally unacceptable. The accuracy/price line is non-linear. It shouldn’t be too difficult to hit, say, less than 0.1mm eccentricity. I’d be upset if I couldn’t do better than that at home. Hitting 0.01mm eccentricity should be possible without too much expense in a commercial operation. Of course if 0.001mm eccentricity is needed then it is going to cost!

One thing that hasn’t been mentioned is that sometimes a slitting saw needs to cut to specific depth, which will obviously be messed up if there is significant eccentricity.

I assume that you know that fine pitch slitting saws are designed for shallow grooves, such as screwdriver slots on screwheads? For deeper cuts a coarse pitch slitting saw is needed so that the gullet doesn’t get choked.

Andrew

[JasonBModerator @jasonb]

I deal with the depth issue by touching off the rotating saw on the edge of the job and feeding in from that point. Doing it static could cause a problem if things are too far off.

[SillyOldDuffer]

On SillyOldDuffer Said: […] my point was ‘how round does a slitting saw need to be?’   I think the answer is ‘not very’, and that seems to be the forum  consensus.  Most of us are using eccentric slitting saws successfully.[…]

 

We have tabled two questions, Dave [one each]

I can answer yours very simply
Will you please then try to answer mine ?

_____

Dave’s Question: how round does a slitting saw need to be?

Answer: it can be as un-round as you can imagine! … in extremis there will be one tooth available, and that is sufficient to do the job so long as you can find the appropriate speeds and feeds.

____

Michael’s Question: how do they contrive to make slitting-saws that are eccentric ?

Answer:

Note:  I have already stated my unproven hypothesis, which was rejected without any alternative suggestion.

MichaelG.

[Nicholas Farr]

On Nicholas Farr Said:

Hi, well out of curiosity, I checked my arbore for runout, and it has in one spot, 0.00025″/ 0.00635mm high, which I’m not going to worried about. I mounted an Arc 42 x 1/16″ x 34T slitting saw, which has never been out of the thin poly bag, let alone never been used, and has no shake at all on the arbore, and I then checked the teeth in the same way as JasonB has shown, after getting my dial gauge to 0 onto one of the teeth, and then turning the spindle slowly by hand, I got a variation  of some of the teeth not quite making the needle reaching back to the 0 position, while others moved it to almost 0.0015″ / 0.0381mm past the 0 position, some of these readings were in-between each other, while some came in pairs, but at least two teeth, not even close to each other. only just moved the the needle, I rotated it at least three full turns, and the readings were very much the same each time. I have no problem with these results either, and I’m very confident that it will cut okay when it gets used.

Regards Nick.

Good evening Nick,

I was intrigued by your findings, and those of Jason, considering the cost of the ARC slitting saws.  This prompted me to look at a couple of unused ARC ones that I have (not the size I wanted unfortunately).  While they appear to have milled teeth, they also have what I will call a small “top rake” ground onto them, which I assume also has the effect of correcting any runout from the previous machining operation with minimal wear to the grinding wheel.  Clearly, buying low cost tooling can work.  I guess I was just  unlucky with the RDG offerings.  With all due respect to them, I have had a refund, and still have the two dodgy slitting saws.

 

[Author]

Posts