Slitting saw sanity check, please?

[woodchucker]

But running it this way hurts my perfectionism. Does anyone have any idea what I might be doing wrong? Or are those screw slotting saws basically a useless piece of junk not even able to cut a shallow slot (like in a screw?).

Lose the perfectionism. It works to some extent, but you wind up overthinking everything when you can be getting things done.... I know, I used to have that issue.. I was not getting things done, but was thinking a lot. Learning sometimes needs to be a hands on experience, lots of opinions, and you know what they say.

 

[Flynth]

Lose the perfectionism. It works to some extent, but you wind up overthinking everything when you can be getting things done.... I know, I used to have that issue.. I was not getting things done, but was thinking a lot. Learning sometimes needs to be a hands on experience, lots of opinions, and you know what they say.

Nah, I'll keep it, thank you very much

I'd rather keep the remaining 98 teeth in that saw... This thickness is quite rare at the usual NOS shops (they seem to be fully stocked on 0.5mm and 2mm, nothing in between) and if I wanted to buy a replacement from normal tool supplier I'd have to pay 5x the price.

Coming back to the subject. I ended up lowering the feed per tooth way down to those 7 microns (3 tenths in inches). That resulted in a feed of 60mm/min (2.5in per min). That was sooooo slow..... If I had more of those, saws I'd love to slowly increase the feed to figure out the real maximum. I think it should be possible to do 150mm/min (6in/min), but I decided to continue at the slow speed and add another saw on the arbor to cut in ganged configuration. I've managed to finish my parts like this with no more teeth lost (and my perfectionism satisfied somewhat - faster would be better)

Here is my gang slitting setup. You can see my DIY misting nozzle too. Initially I worried one nozzle isn't going to clean chips from two side aws separated by, 10mm (almost half in), but I found an angle that worked. Sort of from the side. I'm using a cheap mag base on my overhead support to hold the nozzle.
Here is how I was running with just one saw. With the nozzle blasting right at the saw.

You can see my mist setup on the right. I use an off the shelf needle valve to regulate air and a diy needle valve for oil (much more precise regulation was required if I wanted to try MQL).

 

[Justin.P]

What kind of coolant is best for them? Water based emulsion or straight oil? Also flood, mist, or simple brushing/spray bottle?


I could rig this up. I've got a DIY mist setup I can run with just air.

"Best" is not usually what happens in a hobby shop, not mine at least.

I use WD-40 on aluminum, and pipe thread cutting oil on steel, or occasionally just dry with an air blast. Same coolant schedule I use for any machining operation................

Not best or even optimal, but reasonable and functional for a home shop.

 

[Flynth]

"Best" is not usually what happens in a hobby shop, not mine at least.

I use WD-40 on aluminum, and pipe thread cutting oil on steel, or occasionally just dry with an air blast. Same coolant schedule I use for any machining operation................

Not best or even optimal, but reasonable and functional for a home shop.

Well, mine too. I meant best from those I mentioned (that I have available). I doubt anyone can do "best in general sense". I wonder what that would be out of curiosity. Perhaps sulphurised cutting oil? There is this recipe I saw in a machining book for a "difficult machining cutting oil" that is made by dissolving pure sulphur in hot turbine oil, then adding that concoction to normal cutting oil so there is 1.5% of sulphur content and using it immediately after it cooled. People that used it claim it is the best thing ever, but it has to be made before use as it deteriorates very quickly.

If I ever manage to get my hands on some of that turbine oil (or a substitute) I might try making it. Who knows, perhaps it'll allow me to run the slitting saws at their prescribed chip load per tooth?

 

[projectnut]

There are currently 27 listings for .064" slitting saws on eBay. They range in price from $4.00 for a single HSS saw to over $100.00 for a carbide version. There are several listings for multiple saws (5) for $99,99, and another for (6) for $109.99. The majority of them have 72 teeth with a few at 60 teeth. It appears that many vendors ship worldwide.

 

[Huub Buis]

I have never broken a tooth from my HSS slitting saws (not even the cheap Lidl one), use lubrication (oil on the part, not the saw), 2 mm cutting depth and feed by hand. I run at 30 m/min. Once a year, the slitting saws are sharpened , together with my drills, mills, etc. They all last a few years.
Aluminum is the most challenging to cut because of the chip welding.
The 63 mm slitting saw has 80 teeth, the 80 mm (Lidl) has 100 teeth. They where about € 5,-- each. I made the arbors my self and they have a tight fit.
The mill has to be square to keep the saw cutting at a straight line. Once the first cut is done OK, the saw will hardly come off track so do the first cut at a cutting depth of 1 mm.

 

[Flynth]

There are currently 27 listings for .064" slitting saws on eBay. They range in price from $4.00 for a single HSS saw to over $100.00 for a carbide version. There are several listings for multiple saws (5) for $99,99, and another for (6) for $109.99. The majority of them have 72 teeth with a few at 60 teeth. It appears that many vendors ship worldwide.

BTW, I need them to fit a 22mm arbor (that's 0.866inch). Other than that I have 16mm and 27mm arbors I could use. I'd like to have at least 2 (preferably more) of each size to use in ganged configuration.

I don't know what masterful ebay searching skills are required to find the above. I found just one. In UK so the postage makes it pointless especially that the seller has only one of them(I'm in Poland so I'm mostly looking for EU sellers + Ukraine, UK only if I buy more expensive items). This one: https://www.ebay.pl/itm/36367086648...shTsSBMQSm&var=&widget_ver=artemis&media=COPY

64 thou is not really 1.6mm,but that doesn't matter for most people...

Can you post some links to the cheapest of the saws you mentioned?

I have never broken a tooth from my HSS slitting saws (not even the cheap Lidl one), use lubrication (oil on the part, not the saw), 2 mm cutting depth and feed by hand. I run at 30 m/min. Once a year, the slitting saws are sharpened , together with my drills, mills, etc. They all last a few years.
Aluminum is the most challenging to cut because of the chip welding.
The 63 mm slitting saw has 80 teeth, the 80 mm (Lidl) has 100 teeth. They where about € 5,-- each. I made the arbors my self and they have a tight fit.
The mill has to be square to keep the saw cutting at a straight line. Once the first cut is done OK, the saw will hardly come off track so do the first cut at a cutting depth of 1 mm.

(emphasis added)
Well, that explains it
30mm/min at 100 rpm for a 100 tooth saw is 3 microns per tooth!
I was running 10 times that feed per tooth at the beginning, then I settled on double your feed (6 microns) and I completed all remaining cuts with no more teeth loss.

I now understand why people are having problems with these. It has very little to do with lubrication, but all to do with incorrect info bei g given on various sites and even in books.

According to all the feeds and speeds I found these should run 1~3 thou per tooth, half a thou when "very small". When I run it 10x the speed of @Huub Buis that was slightly over a thou per tooth. My cut depth was 1.7mm (43 thou). Also as a reminder I had a compressed air blast pointing right at the saw as it exited the cut, the part has generous amount of oil on it and there was oil mist blown with the air at it. Perhaps if I had 20 bar flood coolant blasting into the cut that might have helped to achieve those "prescribed" speeds and feeds ;-)

Running them like this results in loosing teeth. They cut beautifully until they don't...

For anyone that came here looking for speeds and feeds for these saws run them 25m/min and 7 microns feed per tooth if you have compressed air, 3 microns per tooth if you just have brushed on oil. Also my literature says these saws are good for 12x their width in depth. I'd like to see that!

 

[Huub Buis]

Well, that explains it
30mm/min at 100 rpm for a 100 tooth saw is 3 microns per tooth!

I do not feed at 30 mm/min. I feed manually and try to make (small) chips not dust without putting to much force on the tool.

I run at 30 m/min. (sorry, calculated the wrong speed

I run the 63 mm slitting saw at 400 RPM, Vc = 79 m/min. That is much faster than the 30 m/min cutting speed for HSS tools I normally use in steel.
I use conventional milling (not climb milling) and lock all the axis that shouldn't move.
The tool path on the part is lubricated using a brush and some oil.

 

[woodchucker]

For anyone that came here looking for speeds and feeds for these saws run them 25m/min and 7 microns feed per tooth if you have compressed air, 3 microns per tooth if you just have brushed on oil. Also my literature says these saws are good for 12x their width in depth. I'd like to see that!

Absolutely not.. 25m/min is close to 80ft/min

 

[Flynth]

I do not feed at 30 mm/min. I feed manually and try to make (small) chips not dust without putting to much force on the tool.

I run the 63 mm slitting saw at 400 RPM, Vc = 79 m/min. That is much faster than the 30 m/min cutting speed for HSS tools I normally use in steel.
I use conventional milling (not climb milling) and lock all the axis that shouldn't move.
The tool path on the part is lubricated using a brush and some oil.

OK, thank you for clarification.

However, that unfortunately doesn't say much about what I'm most curious about,and what will help anyone else looking for numbers, the feed per tooth.

When I feed manually I still keep track of my speed (by for example making sure I turn the crank once per second which is 5mm on my mill or 300mm/min or about 12ipm). Perhaps that's because when I was learning machining I was thought to calculate my feeds and speeds then run with these and adjust them further. So there is always some specific numeric feed speed I'm shooting for when feeding by hand.

As for making chips not dust, it's a bit relative. When I first saw the "chips" it made at 300mm/min they were only barely bigger than dust. At 60mm/min they were quite close to dust, but still one could take them between the thumb and index finger and feel/see individual chips. Have a look at this photo:

Those chips are made at 60mm/min,they don't appear that much different from these that were made at 5x the feed speed:



As for the surface speed you mentioned. It is significantly faster than recommended for hss in steel.(even free machining steel) I'm interested in how much of slitting do you do at that sfpm? Are we talking about an odd screw head once per year, slitting one part a couple of inches long from time to time, or running meters of cuts? Probably, not meters of cuts... Everyone that uses hss at a home shop knows what happens when you run hss too fast. It cuts, it throws beautiful blue chips, for a short while, then the cutting edge dissapears and you have to resharpen it. It is perfectly possible to run it fast for short amounts of time. If it has no opportunity to overheat (due to a short cut for example) it may be fine.

The usual recommendation is 20m/min up to 40m/min in Surface speed is quite flexible as long as your feed per tooth (in case of it being low) and cooling (in case if it being rather high) are adequate.

Absolutely not.. 25m/min is close to 80ft/min

Are you perhaps confusing the surface speed with the feed speed?

Three of my parts with a total of 3m (9ft) of slitting saw cuts say 25m/min is absolutely a correct surface speed to run them. It is exactly 75ft/min. However you're going to be perfectly fine running it from 0m/min up to ~40m/min.

You may run them slower or faster within reason as any hss tool, but this is my recommendation based on my recent experience of using it.