Cutting Speed and Feed for Cast Iron
- #1
I am making large lapping plates made of cast Iron. The plates are 12in in diameter and have face groves every 12 deg. The grooves are 5/64" in width and 1/2" in depth and I am using a 6" dia 42 tooth high speed slitting saw. The machine I am using is large rigid maho and I am set up with a horizontal arbor. So rigidity of machine and cutter are not a real concern. I am planning on running about 40 rpm and 1.6" to 2" a min feeds. I am making 12 in long cuts with out any cooling or evacuation of chips. So cutting dry should I run the full 1/2" depth of cut ? Tolerance on the depth is generous +/- .015. So my only concern is overloading the saw blade and it self destruct on me. So what is your recomendation? Thanks in advance for your time.
- #2
Not looking up your feeds and speeds for you, but I was given the advice long ago to firs take a shallow cut with a slitting saw, then the saw will tend to follow the established "kerf" and make a straighter line. It was, and is, good advice.
henrya
Stainless
- Joined
- Jun 25, 2008
- Location
- TN
- #3
I think this is correct.
Its really easy to make this go bad and every little thing helps.
- #4
The other thing is that most of the cast lapping plates I've seen don't have such deep and sometimes such narrow grooves. The depth might be both unnecessary and more inclined to make the cast plate move and require more resurfacing. The narrow width may be harder to clean the crud from.
If that's what the customer wants, well that's the answer. But if these are for your own use you might try one before cutting the lot.
Either way you might consider a rigging up a vac to suck up the tiny chips. It will ease both the cutting, the air you breath, and the clean up.
- #5
I didnt realy need the speeds and feeds I just wanted make sure the thread title was descriptive enough as to satisfy the moderator. My concern was the depth of cut because multiple passes will realy add up with the amount cuts I need to do. The plates are 1.75 thick so I am not so concernd about the plates warping. The depth and the size of the grooves are the customers choice. Thanks for the insights.
- #6
6'' dia x 5/64 is a pretty bendy saw, ....if you can ''choke'' the blade with a flange (thick washer) either side, ..though you might have to relieve the inside of the flanges to get a bearing on the periphery of the flanges as s/saws are normally hollow ground.
+ 1 on the shop vac for chip evac, ..........recutting chips cause saws to run off and kills them in short order.
**WARNING** depending on the quality of the iron, 40 rpm - 64ft/ min might be a little on the high side for an HSS saw in CI.
FWIW Cutters rubbing in CI = more or less instant death, .....keeping it cutting will improve tool life and quality of the cut.
- #7
Like Limy said: Flanges that leave just a half inch or even less showing will make a huge difference in how this saw blade behaves. Do relieve them 30 thou or so except for the outer 1/4" so that it is definitely the periphery of the flanges sandwiching the blade. Make the flanges out of anything convenient. Even 6061 aluminum 3/8" thick would work well for an occasional use, though something like 4041 PH might be ideal.
I don't mean to take anything away from the good suggestion to make a shallow initial guide cut followed by a "real" cut. But the flanges will convert a situation in which you are trying to coax the blade to track into a solid cutting setup where the blade does what you want.
Denis
- #8
The reqson I am going 40 is that is as slow as the machine will go. As to feeds I was figuring .001 a tooth chip load because of the depth of cut. I guess the dilemma is you realy dont know if you pushed your blade to hard until it goes. That is why I was looking for some insight. I will take your advice and try a bigger chip load as well flanges and shop vac. Thanks again .
- #9
Are you using a gang saw (several on one arbor)? Good luck adding on a bunch of stabilizing flanges and getting that arbor to run anywhere close to true. I have trouble getting one saw to run dead true 
That is typically the real reason that people back down on the feed, because the eccentric saw is loading heavy for only a small part of a turn. To really 'shut up' this eccentricity, you have to fuss around with getting the flanges perfectly parallel faced. Absolutely perfect. All of them. Then feed quite aggressively helps too. I'm not certain why you are using a 6" saw instead of a 4", perhaps because it is difficult to get the arbor support to clear the work?
The best experience I ever had with a slitting saw was to get an insert saw. That thing was hella expensive to me at the time, but it ran way truer than any stupid HSS saw I have ever used. I could feed it heavy, and get something done in a day with it. But the insert width was 1/8" so that wouldn't help you here. Your saws are not going to stay sharp for very long, and then things go bad shortly after that. I'd try to persuade the customer to open up the width of these grooves. I can't fathom why they are so narrow, unless they are being used on very narrow parts.
- #10
.
.
you ever have large saw break apart into many sharp dangerous pieces ?
.
better to take many shallow cuts
AlexO
Banned
- Joined
- Sep 12, 2004
- Location
- RSA
- #11
Saw won't last long and that's if you manage to get it perfectly concentric with the spindle.
AlexO
Banned
- Joined
- Sep 12, 2004
- Location
- RSA
- #12
He's cutting around 2 thou/tooth....
- #13
Singular saw, the part is like slicing a pizza if tjat helps visualize it. Our machine has a nice univeral that I can index the plates on. The purpose of the plates is for lapping geological samples so the machine is quite speacialized. We used the 6" blades because yes we have to clear the arbor. I had to jugle a few variables to make my set up work without having to move my clamps every cut and have everything clear. Going well so far will see how much I can push it, the blade is not getting to hot and I am doing it in two cuts. 3/16 for my first then to the full 1/2". Boss didnt want me to bother with flanges. Thanks again.
- #14
formulas and saws usually do not make much sense. thinner saws break apart all too easy.
- #15
That's only 60sfpm at a 6" dia, so you're fine with the 40rpms.
As for feed, .001/tooth is a good start but you'll have to use your experience to adjust it from there.
Is it a stagger-tooth blade? If so then chip evac shouldn't be a big issue. Can you use any kind of air blast?
I do like the above suggestion of taking a shallow cut first as a guide cut before going to full depth.
- #16
So I had one blade spin on me, cut right through the key but didn't break, so I had to remove the arbor and do careful surgery to remove blade and spacers. Having said that I started with a used blade that had a fair amount of wear on it. I have replaced it with a new one and reduced it to three cuts. As mentioned about blade run out you can see where the blade cuts more on certain teeth. These are straight cut teeth so no stagger.
- #17
Yup, I've had saws cut through the key as well. It's not very desirable, and does not act as any sort of a safety clutch IMO (continued table feed will still break the saw) so I fashioned a HSS key to use with thin saws. The saw could still shatter and break, though. But really, you should make a key driven set of flanges , say 4" diameter, to distribute the load on the key.
henrya
Stainless
- Joined
- Jun 25, 2008
- Location
- TN
- #18
Good accurate flanges are not hard to make. Each side is identical and needs only the proper size hole for the arbor and then a slight "cup" cut so that the outer edges clamp the saw blade. Drill arbor hole, bore arbor hole, face off and then put the cup in with the same boring tool. Done.
Source: https://www.practicalmachinist.com/vb/general/speeds-feeds-depth-cut-slitting-saw-into-cast-iron-341458/
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