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Slitting saw

This topic has 7 replies, 5 voices, and was last updated 16 February 2010 at 21:22 by Nigel McBurney 1.

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15 February 2010 at 21:20 #4964
Chris
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@chris16039
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15 February 2010 at 21:20 #48704
Chris
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@chris16039
Does anyone know of a video on the net showing the use of a slitting saw. Speed of saw, feed etc and work holding methods.

When I bought my wobblers they came with a web site address showing a short demo video and I just wondered if there was something similar for the saw. I don’t seem to be getting far with my own ideas (as usual) so some help required.

Chris.
15 February 2010 at 22:12 #48706
Ramon Wilson
Participant
@ramonwilson3
Chris

The speed and feed will relate directly to the diameter of your saw, and the material you plan to cut – I assume your saws are HSS.

Work holding comes down very much to the job in hand. Some metals ‘close’ particularly if you are doing something like splitting a tubular section or ring and you should be ready for this as it can sometimes grab or nip the saw blade quite strongly as the saw breaks through.

Make absolutely sure you are not ‘climb milling’ ie the direction of travel of the work should be into the direction of travel of the teeth.

The normal cutting speeds for HSS tooling are usually well reduced but keep the saw cutting – don’t let it rub – particularly if it’s phosphor bronze or stainless but don’t force it either.

Another thing to be aware of is that despite an accurate tool holder they don’t always run true (on diameter) and you will hear the cut is intermittent. Don’t worry too much about this unless it is excessive – just concentrate on a nice steady feed making allowance for the run out.

It might help a bit more if you can say what the saw diameter and thickness is and the material and depth of cut you want to apply.

Hope this helps to start with –

Regards – Ramon
15 February 2010 at 23:17 #48709
mgj
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@mgj
The revs is the same as anything else. Translate revs/dia into feet fer minute. I’ve always used the standard cutting speeds, but if you want to go a bit slower I don’t suppose it matters.

Feed is also quite simple if you are hand winding because it will sound right and you’ll produce a steady stream of swarf and a reasonably continuous cut, without the sound of the machine straining or loading. You’ll know if you go really too fast because the saw will slip if your arbour has no driving dog/peg! Varies a bit depending on the coarseness of the teeth and how well they clear. Might be worth doing it by hand first and getting the feel of it before engaging power feed!

I’d suggest you take special care to ensure that the saw is genuinely square to the line of cut. Less important if you are traversing along the job, but vital if you are “plunging across” the job, because then, if the job is wide enough you will be bending the saw.

And I always use lots of coolant – which spins off everywhere – to clear the teeth and keep the saw moving freely because it’s parallel sided and has no back clearance. Nor do you want to let it get hot and expand and jam in a fixed width slot (if deep)

Its not that difficult – if you get a nice steady ting ting noise its fine. If it starts to sing a bit, you’re revving too fast.

Work holding – like all things you have to hold it firmly and have it braced in the line of the cut. Mostly a machine vice or any other work holding doohickey is fine. Like all things, there’s no sense in cutting along something, but be holding it across ways.

Confidence Chris – hold it positively, start with care and increase speeds and feeds steadily till you hit a happy medium. It doesn’t matter if you are not working optimally, so there is nothing to fear.
16 February 2010 at 09:35 #48712
Tony Martyr
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@tonymartyr14488
Chris

Meyrick is absolutely right – the sound of the saw is very useful when you are feeding by hand and if you over cook it then it jams. The real danger is poor alignment and clamping; then you can seriously damage things.

I used the same slitting saw during my loco build on stainless steel and brass tube – there is a photo on my album on this site of it being used on the smoke-box tube.

On stainless steel I used Roco; RTD compound as a lubricant but the speed and feed were set by ‘feel’ rather than from any table and I always cut through the full depth of the material in such a way as to give a long cutting surface and to clear the swarf.

Tony
16 February 2010 at 11:58 #48715
Ramon Wilson
Participant
@ramonwilson3
All good advice so far Chris,

Merrick is quite correct of course in that the cutting speeds should be the same for the given work material and the specific cutter material – however when slitting several other factors come into play that reducing the speed and feed when first carrying out the operation makes it a much less fraught situation especially for the beginner.

That said of course one of the problems most machines have is the inability to go slow enough for the size of saw and material to be cut particularly if the saw is largish and on the harder materials. eg stainless, carbon steel or cast – The only saw available when I slotted the some Quorn castings was 6″ diameter so had to make a very small drive pulley to get the speed down.

Saws come with lots of different tooth patterns too – some quite fine and others very coarse. Fine ones obviously make quite a lot of fine swarf and are prone to clogging if not cleared with lots of coolant and again as Merick confirms this can prove quite a messy operation – speed reduction helps here too!

I’m very much with Tony here though on using a cutting fluid brushed on, clearing any chips from the teeth at the same time as well as agreeing that the cut should be made in one pass if at all possible.

If the saw blade is clamped securely between two flat discs then slippage should not be a problem, if it does occur however it can normally be cured effectively by interspersing a paper shim. It should be said though that, when using hand feed, it’s much better to slip than having a ‘fixed’ drive which could shatter the saw if it does jam.

Ergo feeding by hand is also good advice – as said it is much easier to feel/sense what is going on as the cut continues – power feed, if you have it, is okay once the op has been established but but if the saw jams – which sods law guarantees will happen only after the hand is taken off the feed engagement lever – a ‘crab up’ will occur in amazingly short order!

Merricks last paragraph sums it up perfectly – enjoy yourself

Regards – Ramon
16 February 2010 at 20:56 #48729
Chris
Participant
@chris16039
Thank you gentlemen. Just come out of the shed having made the inside rocker arms for Northumbrian, slots and all. My biggest suprise was being able to do them in one cut (courtasy of your advice) as I had antisipated it being more like a milling process. Small repeat cuts.

The picture was very helpful Tony and I now realise that I need a machine block to raise the height of the cross slide to make the best of my Clarke combo mill head. More packages in plain brown paper to get past ‘she who steals the duvet ‘. Anyone know a good source for these, (machine blocks that is). The Clarke one seem a bit steep at £65, or am I displaying my proximity to the Scotish border again!

Cheers, Chris.
16 February 2010 at 21:22 #48730
Nigel McBurney 1
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@nigelmcburney1
Hi slitting saws do have clearance,they are slightly hollow ground,do not use driving keys or pegs better a slip than a shattered saw, coarse tooth saws cut better and tend to cut straighter,when I was an instrument maker usual practice on slitting brass tubes was to apply tallow as a lubricant,watch out on thick tubes,internal stress can cause the tube to spring shut and pinch the saw at end of cut,when doing one offs always hand feed ,power feeds should be left to production jobs.
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