Slitting Saws

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Slitting Saws

This topic has 16 replies, 8 voices, and was last updated 30 September 2010 at 11:21 by Bogstandard.

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29 September 2010 at 05:00 #5202
Graeme Barton
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@graemebarton49345
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29 September 2010 at 05:00 #56235
Graeme Barton
Participant
@graemebarton49345
Hi ,

thanks for the replys for my previous question about fly cutting.

Next up slitting saws?

How should these actually work? like a grinding disc or a milling cutter? i’ve tried every speed from about 60-300rpm on a 4″ cutter and don’t seem to achieve very much excpet creating a lot of heat. Is squirting cutting fluid enough or do i need to use a proper flowing coolant system. The blades teeth still appear sharp so doesn’t appear to have done it much damage (ok i gave up pretty quick!)

As before any hints/tips much appreciated

Graeme
29 September 2010 at 09:27 #56237
Anonymous
The slitting saw is a milling cutter. Calculate rpm, feeds and chip loads just like any other milling cutter. There are just more teeth to count! If things are getting hot that implies a lot of friction. Might be a feedrate problem. Feedrates for slitting saws are proportionally quite high, as there are a lot of teeth.

Don’t bother with fine pitch slitting saws, unless you are doing a lot of shallow depth cuts such as slotting screw heads. The gullets clog up too easily.

Rules for coolant follow those for milling other materials, nothing special about slitting saws.

If the mounting arbor has a slot for a drive key, don’t use one. If it all goes pear-shaped you want the cutter to slip on the arbor, not shatter.

My experience has been that on a stub mandrel on a vertical mill, there is a tendency for the slitting saw to wander off on cuts deeper than the few millimetres. On a big horizontal with outboard arbor support, no such problems.

Last but not least, whatever you do, and no matter how perfect everything is, the slitting saw will not cut evenly on all teeth. Don’t worry about it.

Regards,

Andrew
29 September 2010 at 09:40 #56239
KWIL
Participant
@kwil
If your saw in a stub mandrel on a vertical mill wanders off, there are two possible reasons, 1 the saw is worn one sided 2 the mill spindle is not truely vertical.

Graeme, is or perhaps it is , was your saw a new one or was it a reliable old make. There are a lot of useless products on our market from the far east, they may feel sharp but the teeth are all over the place angle wise and are often eccentric.
29 September 2010 at 10:24 #56241
Ian S C
Participant
@iansc
Graeme, could be worth looking to the thread on page 13(beginners), some useful tips there. I’v got two or three saws but don’t often find a use for them, so I can’t help much with expiriance. Ian S C
29 September 2010 at 11:25 #56243
Anonymous
Actually there’s a third reason a slitting saw might wander off on a vertical mill. It might be due to slight deflection of the arbor. My vertical mill has a weedy R8 taper, while the horizontal mill is a rather chunkier INT40 taper. In practise I suspect that the wandering I’ve seen is a combination of all three factors. My saws are not new, although not of far eastern origin, and one can never get the mill trammed perfectly. As far as I recall the wandering was about 0.25 mm in a 25mm deep cut.

Regards,

Andrew
29 September 2010 at 12:11 #56246
chris stephens
Participant
@chrisstephens63393
Hi Graeme,

This might sound silly but are you sure you are running the saw blade in the right direction?

chriStephens
29 September 2010 at 12:21 #56247
KWIL
Participant
@kwil
What do you mean by a “weedy” R8 taper, there is no way a slitting saw could deflect a R8?
29 September 2010 at 17:27 #56257
Tony Pratt 1
Participant
@tonypratt1
I agree with Kwil, from practical experience there is no way a slitting saw will deflect the bearings on an R8 taper. You don’t state the thickness of the saw, depth of slot or work material but make sure the cutter is sharp, small cuts, slow feed and coolant is the order of the day.

If there is a lot of heat being generated you are running too fast, off the top of my head try 200rpm and don’t force it through, take it gently!

Tony
29 September 2010 at 17:35 #56258
Tony Pratt 1
Participant
@tonypratt1
Hi Graeme, bit hasty with my rpm suggestion, please ignore it until we know the material being cut.

Tony
29 September 2010 at 18:01 #56261
Graeme Barton
Participant
@graemebarton49345
Hi there,

The metal is some 50×50 square black bar

The cutter is being held in an R8 arbour

The saw is about 2mm thick (can’t remember the actual size, it’s imperial) and was bought from Chronos

Turning in the correct direction, maybe i’m not feeding it enough.

Not sure what Andrew Johnston is talking about? didn’t know that the number of teeth made a difference. I was doing my very rough calculations on the diameter of the saw but if there’s something else i should know…………

Ta

Graeme
29 September 2010 at 20:35 #56267
Tony Pratt 1
Participant
@tonypratt1
Graeme,

4″ diameter cutter cutting mild steel at 100 ft/min cutting speed would need to run at about 100rpm. Give it another go and report back.

Tony
29 September 2010 at 20:57 #56270
Anonymous
It’s not a case of deflecting the spindle bearings. It’s a case of the arbor deflecting. Unless you have an infinitely stiff arbor and/or zero cutting forces the arbor will deflect. Now I will admit that the deflection is very small, in order of a tenth or two of a thou according to my calculations. I expect in this case that it is negligible compared to the other effects. It was a slightly tongue in cheek comment.

Graeme,

Sorry I didn’t explain myself clearly. As Tony says the cutter rpm is determined by the diameter of the cutter and the recommended surface cutting speed of the material. I agree with his figures. The feedrate is determined by the rpm AND the number of teeth. To take Tony’s example of a cutter doing 100rpm. Suppose we want each tooth to cut about 2 thou of material. If the cutter has 4 teeth then the cutter will need to advance 8 thou per revolution. This gives a feed per minute of 0.008″ times 100, ie, about 0.8″/minute. However, suppose our slitting saw has 40 teeth. Then the feed per revolution will need to be 80 thou for the same cut per tooth. This gives a feedrate of 0.08″ times 100, about 8″ per minute. The number of teeth doesn’t affect the rpm of the cutter, but it does affect the feedrate.

I’ve added a picture of a slitting saw in action in my Odds ‘n’ Sods album.

Regards,

Andrew
29 September 2010 at 21:54 #56274
Jeff Dayman
Participant
@jeffdayman43397
Hi Graeme

In my experience if the saws are not good quality high speed steel they will have trouble with the hard scale on hot rolled (black) steel stock. You might try cutting some brass or leaded free cutting steel as a first trial of sawing. If these cut well, then your feed/speed settings and your kit are OK, you just got a bit of rough scaly black rolled steel.

I use my saws quite a lot, with good results, and they are worth the effort to figure out how to best use them.

JD
30 September 2010 at 03:28 #56280
Bogstandard
Participant
@bogstandard
Just to add a litle to the discussion

Rage slitting saw

Bogs
30 September 2010 at 09:51 #56281
KWIL
Participant
@kwil
So it has depth control bumps like a chain saw.
30 September 2010 at 11:21 #56285
Bogstandard
Participant
@bogstandard
Quite right Kwil, if you look at the last pic, you can see them.

That is why you have to make sure you don’t feed too fast when used on something like a mill.

I’m not talking about super slow feeds, it did that cut in about 15 to 20 seconds, plenty fast enough for most people.

Bogs
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