View Full Version : How to cut short piece of huge stock

01-04-2009, 07:31 PM
I have a piece of cast iron I got for christmas. It is slightly over 4 inches diameter, and 2 inches long, and I need to cut it into a pair of 1 inch thick disks with non-horrible accuracy. I do not have a bandsaw. I do have access to a chopsaw with nowhere near the capacity needed, a small angle grinder, the lathe.

I grooved it deeply in the lathe with the parting blade but even with the short extension it chattered badly. I have a hacksaw, of course, but it seems like this would take a very long time to do, and I seem to be very bad at using the hacksaw effectively.
Any ideas other than finding somebody who has a bandsaw or hacksawing the thing?

Also: My dad was freaked out about me having something that big in the 4 inch 4-jaw chuck in the lathe. It was spinning 100 rpm. He ordered me to have a rod in the tailstock chuck near the end so that if it came out of the jaws it would not hit me in the face or something even though it was only 100 rpm. Is this reasonable?

John Stevenson
01-04-2009, 07:47 PM
Cast iron should cut nice but you are probably limited by machine rigidity.
Do you have a revolving centre and can you stand a hole in the end of one piece? If so centre it and support it on the revolving centre.
If you can't stand a hole in it take a bearing and put that over the centre and push it onto the face of the work.
This is a poor mans revolving centre.

Any support you give the work will pay back 10 fold.

Then try parting off as deep as you can go, you probably won't be able to get too deep because of tool limitations but remember you are removing more metal at the circumference than anywhere else.
This will give you a groove that you can follow with your hacksaw in the vise.
Don't be tempted to try sawing in the lathe unless you want a new forum moniker of "split nose"
keep turning the metal following the parting off groove, cast iron cuts readily into dust, you don't need any lubrication as the graphite in the cast does it for you.


01-04-2009, 07:54 PM

The piece is half as wide as long

I did not think I would be able to center it but maybe if i overexend the tailstock...

I was using cutting oil mainly to make the dust less messy and blob it up.

01-04-2009, 08:02 PM
This is one of those occasions where networking is very useful. You really need to borrow some time on a band saw. If that doesn't work out then a hacksaw is the next good idea and yep, it will take a while. In a pinch you can also use a reciprocating saw which are available for rental - a variable speed version is most suitable. An automotive machine shop may be able to cut it off for you at a very reasonable rate.

John Stevenson
01-04-2009, 08:09 PM

The piece is half as wide as long

I did not think I would be able to center it but maybe if i overexend the tailstock...


No it's twice as wide as long or at least 4" diameter by 2" long was when I went to school but that was a long while ago :D

If you have already had it in the chuck and had a rod in the tailstock chuck why can't you centre drill it ?


01-04-2009, 09:21 PM
OOps sorry..

Actually there is enough clearance. I did not think there was. Tailstock out pretty far though

NO luck. The chatter is extreme. Lathe not rigid enough> The groove is barely 3/8 deep if that. '

Reciprocating saw? you mean like a saber saw or a sawzall? My dad has a sawzall but I never though of that. I wonder if he has a long enough metal cutting blade.

01-04-2009, 09:25 PM
100 rpm on a lathe the size you have will be a chatter box, that said... I have done what your trying to do on my 9 inch. Run as slow as possible, if you need to, see if you can snag a smaller drive pully for the motor. I kept several on hand with my setup just for the ability to do stuff like this. Some support on the TS side sure won't hurt and will provide a margin of safety as well as more stability.

Tool geometry matters greatly here, the cutting edge really needs to be dead on parallel to the axis of rotation as well as having the tool itself at a dead 90. Any variation will cause the tool to pull to one side or the other. Center height and tool sharpness also count big time, your better off being slightly above center height than below.

This job is a definite "Take your time" thing. Very very slow on the feed in, back out and clear chips/dust often. don't have to back out all the way. I ran 1/16" or 1/32" parting blades on my 9", never larger, as wider tended to be a bit much for the machine, especially with larger diameters.

Partially cutting through with a parting blade then switching to a hacksaw or Recip saw would be a smart move. Yes it's a slow process, but the goal is to do what needs to be done, decently. Not to get er done fast. There really is no reason why one cannot get through that diameter of cast with a hacksaw, not only in a moderately timely fashion, but also with little problem in deviation beyond what one will lose from a parting blade. Patience and proper setup are the key. As others have said, do NOT try to saw in the lathe.

01-04-2009, 09:30 PM
I have a piece of cast iron I got for christmas. It is slightly over 4 inches diameter, and 2 inches long, and I need to cut it into a pair of 1 inch thick disks with non-horrible accuracy. I do not have a bandsaw. I do have access to a chopsaw with nowhere near the capacity needed, a small angle grinder, the lathe.

If it is 2 inches long and you want two 1" pieces you have a problem. The cut is going to use up materials.

Can you chuck it and use a hack saw? Don't leave one spot in contact but drag the blade across as it revolves in your chuck?


01-04-2009, 09:37 PM
I included kerf in my calcs.

01-04-2009, 09:40 PM
I'd hacksaw it. You'll go through more trouble and use up more time trying to find a better way to do it. You've got a hacksaw, you've got a vice ... I say have at it! I've cut my fair share of BIG stuff with a hacksaw. It isn't fun, but it teaches patience, if nothing else :)

Oil is not a good idea on CI, in general. Coolant is acceptable, but the oil tends to "glob up" as you say, and then you end up with an abrasive slurry that will dull your tool quickly.

Alternatively, find a friend who can do it for you. I'd be happy to cut it for you, but I don't think you'll want to pay postage all the way to Illinois, just to cut a piece of CI.

edit: you say "not horrible accuracy" - what is the final dimension needed on the discs? You'll probably need to shave a fair amount off after hacksawing to get a clean, square face

01-04-2009, 09:40 PM
-Metal blades for recip saw are cheap, so you could go that route since you have a groove to help guide the blade. The blade will have to be longer than the diameter you're cutting by at least the stroke of the saw (an inch or more). On a virgin cut, though, you might have problems getting a straight cut...

-Oil on CI (cast iron) causes all sorts of grief. It's messy to cut dry but that's how it's generally done.

-Sometimes you can help the chatter on a cutoff blade by putting a good support under the cutoff tool holder. I use a small homemade machinist's jack (basically a bolt with a turned-smooth top on the head, with two jam nuts) for this. But you have a deep cut so you may be out of luck trying a cutoff blade

-A hacksaw with the part NOT turning is probably your best bet. Note that hacksaw blades come in different teeth per inch, and you probably want the coarsest you can find for this. A real hardware store (maybe Ace or TruValue) may have some options here. Probably not Lowes and their ilk...

-Your dad has the right idea. A four-pound chunk of iron can put a real hurt on you even if it is only going 20 MPH. Also, you should be wearing at least eye protection and preferably a full face shield, since you are learning what works and what doesn't. Bad stuff can happen, though it usually doesn't, but you won't have time to put these on if something does go wrong (like a cutoff blade shattering and flinging a piece into you). This is one of those issues where you'll hear a lot of "don't worry, that's never happened that I've heard of" but if you're blinded you won't get to do much machining. It's a small probability but high penalty situation; better to be in the habit of being at least somewhat over protected than underprotected.

01-04-2009, 09:45 PM
Don't tell anybody but the guys on here that you got a 4" lump of cast iron for Christmas. Nobody else would understand. Me, I don't understand why Santa didn't bring me one.

I think the hacksaw might be safest. If you've already cut a groove with the parting tool then this will be a good guide. If you are game for parting it then facing it after the hacksaw should be no problem.

Safety first. Trust your Dad. I've lost more than one tip off a parting blade. They departed with a big bang and I never did find the tip.

Good Luck

Your Old Dog
01-04-2009, 10:01 PM
If you got access to a Sawzall you got the world by the tail !! I have one next to my lathe and use it frequently to do cut offs on the lathe. Get an aggressive bi-metalic and it should cut the cast iron like butter, albiet frozen butter :D If there is one tool I'd put on a pedestal it would be the Milwaukee Heavy Duty Diamond Anniversary Model Sawzall I got a few years back. Don't know why and the hell I waited so long to get one.

01-04-2009, 10:22 PM
I might get flamed for this but why not run the lathe in reverse, take your hacksaw, reverse the cutting direction on the blade, and try cutting it with the lathe running in reverse? If it grabs the blade, the hacksaw will fly away from you, not towards your nose... You should remove your splash guard unless you want a nice big dent in it.

Mike Burdick
01-04-2009, 11:08 PM
I cut and use small pieces like that all the time. I mostly cut them using a Milwaukee portable band saw but a hacksaw will work just as well. Here's how I do it...

Let's say I have a 4-inch round that is 1-inch in thickness and I want to cut it in half. First I scribe a cutting line around the circumference. Then I place it in an ordinary work vise clamping it on the cut ends just a little above centerline. Using the portable band saw, or hacksaw, I cut it until I get about 3/8-inch from center. I rotate the material and continue to saw until I get a cut all around the bar. This will leave about 3/4 - inch diameter of material in the center. To complete the cut, I put in a piece of broken saw blade on one side of the cut and put the material back in the vise clamping it at the old saw blade. Cutting it this way results in the material being held very rigid and therefore no binding of the blade will occur.

01-04-2009, 11:10 PM
The main problem is what happens to the cut off piece? It's at least gonna ding the ways, maybe ding someone's face. Although, it should at least be rotating so that it goes away from the operator :-) But with the CI chips and all, I don't think it will be much faster than cutting with the lathe off (although I've never tried the experiment myself)

01-04-2009, 11:16 PM
although I expect to be admonished for it ...
I cut stuff off with a hack saw (and now with a portable bandsaw)
in the lathe fairly often it is a great way to get decent (flat) cuts.
part as far as I dare then start sawing with the peice rotating at low
speed. what I am careful of is not to nick the bed when I cut through.

tony ennis
01-04-2009, 11:44 PM
If it grabs the blade, the hacksaw will fly away from you

...and maybe pull his hand into the chuck.

Wear safety glasses always.

I've also had drill bits and parting tools break. We never did find all the drill bit.

01-05-2009, 01:15 AM
Bring it over & I will cut it 4u 4 free. I live in LV if that is a problem put it in a flat rate box send it w/ return postage the total will be about $19.00 for that price almost any shop will cut it 4u 4less.

01-05-2009, 01:59 AM
You've got it scored already along the cut line, or should I say grooved- another vote for finishing it with a hacksaw. Get a few new blades first, don't even bother with a used blade. And forget about the bargain bin garbage. Go easy on the blades for the first minute or so, and alternate the blades so you don't have to put a new blade into a cut left by the old blade. It shouldn't be as time consuming as you might think. Try not to drag the blades backwards under pressure, and cut it dry. It probably will be quicker than figuring out another way to do it. I'm guessing that it would be done by now if you were willing to pay a shop to do it, so it seems definite that it's going to be done in your shop. Saw for a bit, take a break, repeat.

01-05-2009, 02:32 AM
That is why you need to put your location in your profile. I would bet that there is at least one member of this board who is close to you and would be willing to lend a hand - if they knew where you lived. I cut some slices off of some 1"x12" hot rolled for a member on Saturday because is was a little bit bigger than what his bandsaw would hold. Ran it with a batch of stuff that I was doing for myself and it added ten minutes to the job, and I am sure that he would have done the same for me if the situation was reversed. I don't think that anyone on this board has every tool that there is (though some of are trying) so there is nothing wrong with "machinery" networking and remembering what friend has what piece of oddball equipment.

01-05-2009, 04:55 AM
Use a hacksaw, I'm serious, it's good practice. Saw and file work are the backbone of a good machinist.

01-05-2009, 06:00 AM
Use a hacksaw thats fitted with a top quality blade,or take it to a machine shop that has a decent band or power hacksaw. I definatly wouldn't try cutting it in a lathe.

01-05-2009, 11:46 AM
Didn't see if this was mentioned above regarding parting, however if yoiu have a parting tool blade which slides out of the holder, have the minimum extended, say 1/2", groove just under stop and extend the blade a little more to give maximum rigidity to the blade.

Make sure your cross slide gibs are snug, lock the saddle and compound. Support with the tailstock , you can extend the reach with some ingenuity!

Hope it all works out, next time ask Santa for 2 x 1" discs :D

01-05-2009, 01:39 PM
-Your dad has the right idea. A four-pound chunk of iron can put a real hurt on you even if it is only going 20 MPH.

Now comes the fun math part, at 100rpms, the fastest part of the material, the outer edge is only moving at a little over 100 SFM(surface feet per minute), which equates to a whopping 1.2 mph, probably enough to throw it onto your toe, make a big racket, trash a part off tool and scare the crap out of you.

Also, you should be wearing at least eye protection

Definitely a good habit, I had the hardest time when I had young, college age employees, they did not like to wear their safety glasses, they didn't think they were "cool". In time though, they felt naked/unsafe without them, and would instinctively put them on, even on cleaning days with no machines running.

They can always chop off your big toe and use it as a thumb, but you can't replace an eye.

01-05-2009, 02:55 PM
Always using eye protection

Interesting about greasy cast iron dust making abrasive that dulls tools. thought that dry dust would be messier and perhaps more abrasive than glop that can easily be picked up. Must reconsider.

LOL! Dad said that the UPS man was very intrigued by the weight of my presents. (I got a surface plate, a live center (finally), a green wheel and a wheel dresser, a good endmill, and a bunch of metal) Many of these things being heavy.)
I am in the North SF Bay area. More specific than that I cannot give without talking to my parents, who are typically and perhaps realistically worried about preadators. However, I plan to go the hacksaw/recip saw route.

01-05-2009, 03:22 PM
Good plan on the hacksaw/recip saw. And your parents are very wise - lathe operators have been known to turn on you in a blink. :p

There are safe ways to meet peers and potential mentors at hobbyist functions such as model making fairs. Find out what is in your area, talk to your shop instructor, what ever, bring your parents.

tony ennis
01-05-2009, 03:23 PM
Your parents seem very caring :)

Liger Zero
01-05-2009, 05:25 PM
MY parents never brought me machining stuff. All I ever got out of them were violent video games and a really nice car that I wish I had taken better care of. :D

Cutting information noted and logged. I have some odd-sizes of material I rescued from the garbage. Company was trashing various sizes and shapes of plastic stock that had been sitting for quite awhile. Filled Delrin and nylons and stuff like that. Grabbed all the round stock, and called my friend to take the rest. :)

01-05-2009, 06:20 PM
FWIW, if you go with the sawzall, don't go with a dedicated metal cutting blade, which will have very fine teeth. Any good bimetal blade will cut even ferrous metals, and for something that thick you'll want something with a much courser tooth pitch. As long as you have more than 3 teeth engaged at a time, there isn't really much risk of stripping teeth off the blade and having problems with it grabbing excessively. I think I used a 4-6tpi "wrecking" blade the last time I did something like that.

Oh, also, don't think that it's going to be that much easier with a sawzall than a hacksaw. Yea, the hacksaw will be slow, but it will be easy going also. The faster cutting blade you work out for the sawzall the faster it will cut, but also the angrier it will be and the harder you'll have to work holding onto it. I remember at one point cutting some 1/2" steel in a workmate with one and I had to have someone sit on the workmate to keep it under control, and I was doing enough work that I remember actually having to take 2 breaks durring the job.

01-05-2009, 06:38 PM
i think this young fellow is much smarter than we have given him credit for. . .:D :D

you could just put san francisco in your title. its big enuf that no one will harrasss you. . . . honest. . . .

i''d bet you have it cut off by now. . . with a hack saw.:D

i use my milwaukee portaband saw like it was a parting tool after parting a decent area to start the cut. put a 1 by ? board under where your going to have the part fall, makes it much easier to find the part. :eek:

01-05-2009, 07:04 PM
I keep a plank of pine behind the lathe to put on the ways for any occasion that requires grinding or sawing chucked work. That stuff is messy and gets into everything. It also keeps the saw off the ways. I also place it on the ways when I remove the chuck as those can get away from you.

Liger Zero
01-05-2009, 07:31 PM
i use my milwaukee portaband saw like it was a parting tool after parting a decent area to start the cut. put a 1 by ? board under where your going to have the part fall, makes it much easier to find the part. :eek:

I made this nifty looking smallish part out of Delrin for a friend. Took me an hour to lay everything out and plan the sequence of cuts and get everything just so with the lathe... Went to cut it off with the parting tool, sucker took flight and I had to make another one... damned if I know where it landed.