JHCC

Turning an old chop saw into a cold-cut saw?

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Over the weekend, I picked up an old Acco-Campbell Sever-All chop saw for very cheap from the industrial surplus place. It's missing the motor and switch, but is otherwise complete.

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(Shown here with the handle and the back guard removed.)

This is currently set up to use abrasive discs, but it occurred to me that I could possibly set it up to be a cold-cut saw. Haven't made up my mind yet, but I thought it would be worthwhile to solicit some opinions from those with more experience.

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Some data: The saw has a 1-1/4" arbor and takes a 14" blade (if memory serves; I'm currently typing this up in the airport, so please forgive any inaccuracies). I believe it originally had a 3 hp / 3450 rpm / 220v / 3 ph motor.

I have a nice 1-1/2 hp / 1725 rpm / 115v / 1 ph motor currently not doing anything (the original motor from The Pressciouss) that I could mount on this saw.

It seems to me that if I mount my motor on the saw with 1:1 pulleys, that will put the rpm of the arbor about the same as needed for a carbide-tipped cold-cut saw, although I don't know if they're available in that arbor size. I could also set up the pulleys to give a greater arbor speed, but that would reduce the torque at the blade, possibly below the necessary minimum for effective sawing. I could also set it up to reduce the arbor speed as with a more conventional cold-cut, which would also boost the torque in the arbor.

I could, of course, also get a more powerful motor, but this is what I have on hand.

Any thoughts?

 

 

 

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First you need to define "cold cut" a little better.  Those high speed carbide tipped versions are actually a hot cut saw and rely on the heat generated in the chip to do things like keep the chips flowing and peeling away.  The heat actually makes the chips brittle so they break into small pieces instead of a stringy mess--Imagine this as drilling where you get those curls coming off vs "chips" being expelled from the hole and you might get the drift of what the heating of the chip is actually doing as it cuts.  In CNC lathe operations, you often increase speeds and feeds for the same purpose so the chips break into manageable pieces rather than form stringy rats nests.  A true cold cut saw usually runs about 60-90 RPM in that diameter, most commonly with flood coolant, and is more like a standard machining process to get high quality cuts vs fast cuts.

For nearly burrless cutting of aluminum tubing for refrigeration coils, we do similar but at 7000 rpm.  Ya gotta watch those blade RPM limits carefully in our shop when buying replacements.

That being said, I think you could convert this machine to a carbide hot cut (and again, that term will vary because it's ill defined for these saws).  Be sure and plan for expelling "chips" as I assume this was originally for an abrasive blade and the swarf coming off that is different. Actual "chips" may tend to pile up in places where they can cause issues.   Also, it'll be noisy as heck--ear protection will be a MUST.  Tune everything up so you are 100% sure the blade is accurate and has zero wobble.  That might mean machining new plate washers for each side of the blade (originals for abrasive blades are not always the best precision, especially after years of wear).  The blades also might not be common in sizes which match that spindle style and diameter so you might have a battle with that and need to have a new spindle made--match whatever is standard in blades rather than simply trying to find a blade that matches your spindle and you'll be better off in the end.

And be sure to get blades from a top quality supplier who specializes in this type of cutting.  Going with a low end blade does NOT pay off on these.  

Please give feedback if you get this running.   I've been in the "planning" stages for ages to do a similar conversion on an old industrial cast iron woodworking "jump saw" because in my operation, I cut thousands of pieces of 7/16" round bar (T304 SS).  I'd sure like to hear of your successes and challenges as you get this running.

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Thanks for the input, Kozzy; that all makes lots of sense. As always, I'm aiming for low cost and would probably end up sticking with abrasives rather than getting a new arbor. I'm also thinking that for hobbyist use, something that can cut through possibly heat-treated stock (e.g., jackhammer bits) would be good to have, especially since the horizontal bandsaw can probably accommodate most mild or unhardened pieces I need to cut up. More to think about....

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Kozzy: While I'd like to sit down over coffee and talk about how much the term Hot applies in this case it isn't important to the subject under discussion and this is too serious for fun talk.

While I've used carbide tooth saws sometimes frequently over the years I don't really know that much about them as a machine. Heck, I've probably had you gnashing your teeth more than once and thank you for your reserve in not slapping me down. I can use a good slapping now and then.

I've been using power tools since I was way young and Dad drummed into us how to listen to and interpret the song machines sing in operation. Every . . . What should we call these saws ? I've always judged operation by sound and performance, saws have the: "free" song, the "contact or rubbing" song, the "working" song and the "lugging down" song.  And all the grays in between it takes a couple few cuts to learn. 

However what are the book speeds, in general I'm not expecting you to start looking things up for me I'm interested in principles of how the blades cut and how the machines that use them operate properly. 

Sorry, that's a lot of back story for a few questions, darn windy old coots.

Do carbide toothed saws work better with high speed or do they require torque to bite chips? Do you look for a sweet feed or hog it. The one at the heavy duty shop was powered by a 3450 RPM. x 4HP 3ph. motor and you couldn't feed that 20" beast of a blade too fast. It would no fooling go through 8" wide flange with a loud BANG as fast as you could feed the lever.

Smaller ones have behaved more as I expect of a circle saw, songs the same songs but with a different voice. Still, feeding faster is usually better.

EXCEPT cutting bundles, can't hog through bundles without chipping carbides.

Thoughts please.

Frosty The Lucky.

 

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On 9/17/2019 at 6:42 AM, JHCC said:

This is currently set up to use abrasive discs,

JHCC, please post a photo of where the Opertor places his hand on the machine to make the cut.  I have extensive experience with dry abrasive cutting of large (2" dia) high speed and high speed cobalt twist drills, as well as tool steels. This unit is ideal (if the spidle assembly is in top condition) for this class of work.

I wager, sight unseen, mind you, that your spindle assembly is not suited for toothed saw operation. Once I see a shot of the Operator Interface, I can be more helpful.

Oh, and that BROWN and SHARP stock vise is no good. I will send you my shipping address:ph34r:.

Robert Taylor

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The chop saw we have at work has a diamond blade in it. The little I have used it so far it seems to cut cooler than a regular abrasive wheel. Personally I hate abrasive saws, but realize that they do have their place.

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BGD - is that blade used on ferrous materials? I just purchased a 4-1/2" Lenox   diamond cut off wheel - Big Box stores are selling the Freud Diablo version. Have not tried it yet.

If they make this in Industrial size, I would be ALL OVER IT!

Robert Taylor

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OK, could not stand it, had to try it.

Mild steel tube: Yes. Wear hearing protection. Copper tube: Yes. Do-All Industrial bimetal: Yes. 440C Rc 60: Not Recommended, but will cut. Nitraloy Rc 40:  Not Recommended, but will cut.

20190920_121624.jpg

Edited by Anachronist58
had to try it!

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After seeing the diamond option I ordered the Lenox for my 14" abrasive cut-off just to see how it compared.  It actually wasn't that expensive so worth the try on a lark.  I'll report back as to results after it comes in and I run some tests.  As much as I hate the abrasive cut-off wheels, I can't see this being much worse...and maybe much better.

Reviews were mixed but mostly positive.  However on that behemoth website they mixed all blade diameters together in the reviews.

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Looking at these options, I often see maximum RPM listed, but is there such a thing as minimum RPM? For example, if I put my existing 1725 RPM motor on the chop saw with a 1:1 pulley ratio, would that be too slow for an abrasive saw with a maximum RPM rating of 4,300? Or would that just lower the feed rate?

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There is definitely a minimum rpm, or more specifically. Surface Speed. 5,000 feet per minute is a rule of thumb for abrasive cut-off operations. I am just throwing out  ROT numbers here, so all comers are welcome to tweak the data.

Surfsce speed is critical. We are not grinding the metal, we are BURNING it. You need horsepower and 3,450 rpm MINIMUM at the wheel spindle at a specified diameter.

All this is blah blah blah, you need 5,000 surface feet per minute and you "might" get away with one horsepower.

 

Robert Taylor

7 hours ago, Kozzy said:

I ordered the Lenox for my 14" abrasive cut-off

Kozzy, I wait with baited breath! (what ever THAT means)

Edited by Anachronist58
addendum

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Hmm. If I use my 1725 rpm motor and a 14” disc, that’s about 6,320 sfpm (=(14” x pi x 1725)/12). I think this might be worth a try. 

12 hours ago, Anachronist58 said:

I wait with baited breath! (what ever THAT means)

It’s not “baited”; it’s “bated”, which means to lessen or minimize (from the same root as “abatement”). Thus, “I’m waiting with bated breath” is basically the same as “I’m holding my breath while I wait.”

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This is what I love about IFI. I learn something new every day. Now if I could recall what I learn when needed, that would be something.:)

1 hour ago, JHCC said:

It’s not “baited”; it’s “bated”,

 

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2 hours ago, JHCC said:

(14” x pi x 1725)/12

By the same token, the smallest diameter that would produce 5,000 sfpm at 1725 rpm would be an 11” blade. 

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I used it on stainless steel and it did good on that. I haven't tried anything else. And our saw is I believe a 14" possibly DeWalt-it is yellow,

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6 hours ago, JHCC said:

It’s not “baited”; it’s “bated”, which means to lessen or minimize (from the same root as “abatement”). Thus, “I’m waiting with bated breath” is basically the same as “I’m holding my breath while I wait.”

Darn it John, you're a spoiler! Talking about baited breath is one of my long running fun with words games. On rare, sadly rare, occasions when someone explains I meant bated I respond with, But I had sardines for lunch. Another time I'll respond with, Nope, he has bait breath. On and on.

Now what am I going to do if we meet up? You fun ruiner guy you.

Frosty The Lucky.

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If you've had sardines for lunch, your breath definitely needs a bait mint.

Getting back to the subject at hand, I took out the blade that was still in the saw. The spindle is 1" with a bushing to bring it up to 1-1/4". The threads are super clean and crisp, but I suspect that mounting an abrasive disc directly on the threads will not keep them that way.

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The plate washers are recessed in the middle to clear the bushing, so the gap between them is quite small when there's no blade in place: maybe 1/32" or 3/64" at most.

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On 9/20/2019 at 12:01 PM, Anachronist58 said:

JHCC, please post a photo of where the Oper[a]tor places his hand on the machine to make the cut. [...]  Once I see a shot of the Operator Interface, I can be more helpful.

Here you go. This is after I reinstalled the handle and the cover for the slot in the blade cover that allows the arbor to swing up and down. The operator raises and lowers the saw with the rubberized grip on the end of the long, straight handle.

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On 9/20/2019 at 12:01 PM, Anachronist58 said:

Oh, and that BROWN and SHARP stock vise is no good. I will send you my shipping address:ph34r:.

Nice try. That vise has got to be worth at least the $14.40 (plus tax) that I paid for the whole setup.

 

 

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21 hours ago, Frosty said:

Darn it John, you're a spoiler!

Yeah Frosty, John is your spoiler, and you have blocked my escape from the Grammar Ham(mer)!

JHCC, you might use a wheel with with a one inch arbor hole, but ONLY if the hole has a steel grommet to isolate the abrasive from that pristine arbor. Use precision bushings to adapt to various sizes of arbor holes.

It is important that the counterbalance of  the motor is sufficient to cause wheel to rise from the cut on its own (assuming that there is no spring type return assist). If the motor that you use is underweight, then deploy additional counterweight(s).

The reason for the double-sheave spindle pulley is to transfer more  torque from the drive, without having to over-tension the belts. Over-tensioned belts can cause premature spindle wear, but worse, destructive harmonics in the machine frame.

JHCC, let none of the above stop you from slapping a motor on, putting the wheel back on, and making sparks (for safety, the spindle must by default, rise from the cut on its own). THAT is what I would do!

Anyone able to find a reference for minimum effective surface speed? So far the WWW has failed me..... 

Robert Taylor

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I haven't found a reference for minimum blade speed either. The closest have been pretty subjective opinion rather than numbers. Use fast for aluminum, slow for steel, kind of unhelpfulness.

I think you're as right on the money in your advice as anybody so far and nobody has offered bad advice. It's like you've done this before. I'd , print your advice out and take it to the shop with me were this my project.;)

Frosty The Lucky.

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Yep, that is the same reference that I found. Best so far, but not completely satisfying, as it can be presumed that the optimal 12,000 SFM is derived from a 14" dia wheel at 3,450 RPM, Approximately. Thus, this number may be altruistic.

If I use my 4" cut off disk down to diameter 2" @ 10,000 RPM, I still get appropriate stock ignition @ 5,000 SFM. (in most cases).

Stainless steels appear to require higher surface speeds and or specialized wheel composition, but now we are getting into the weeds of my incomplete knowledge.

Again, I draw my working experience from cutting high-speed steels and tool steels.

On 9/21/2019 at 9:43 AM, JHCC said:

Hmm. If I use my 1725 rpm motor and a 14” disc, that’s about 6,320 sfpm (=(14” x pi x 1725)/12). I think this might be worth a try. 

So JHCC, when you gonna abate my anchovy breathlessness, and mount that motor? It has the speed, just maybe not the horsepower. At worst, you will know better your next step. At best, you will be cutting!

Robert Taylor

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2 hours ago, rockstar.esq said:

I found this article

Thank you; very interesting. 

34 minutes ago, Anachronist58 said:

So JHCC, when you gonna abate my anchovy breathlessness, and mount that motor?

Have to get a drive pulley that fits the motor’s shaft first. 

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Not even about RPMs though that is critical as well...the big issue is lack of rigidity.

Cold saws are massive castings not pressed sheet metal. Cold saws blades cannot bend while cutting, they break. 

NOTHING wrong with a large abrasive saw. Use it for what it is designed for; hardened tool steels and thin walled material which should never go in a band saw. 

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Excellent points, arftist. Thanks for the input, and good confirmation that I should be well served by the combination of this saw for the uses you describe, my bandsaw for unhardened and unhardenable steels up to 4" x 6", and an angle grinder for everything else.

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