Metal Cutting Saw

[BukitCase]

Willie, check the rated rpms on your saw (probably 3600 or so) vs. the rated max rpm of the blade you're looking at - I've seen a few that are rated at high enough speed for a normal chop or radial saw, but haven't tried 'em to see how long they last.

What I DID do, and it was a success (until it wasn't :=( was to buy a "closeout" blade from Hazard Fraught, it was a 14" carbide tipped "metal cutting" blade - it listed max rpms at around 2400 IIRC, and my abrasive chop saw is 3650 or so - I got stupid, put on my heaviest welding leathers/gloves and face shield, clamped a piece of square tube down, stood with ALL body parts AWAY from the plane the blade runs in, and gave it a shot -

The cut was perfect, no burrs, looked like it had been polished after cutting. Same with the second cut, up thru about the 15th or so (IIRC, it was 2" .095 wall tube) -

Then, it got harder/slower to make each successive cut.

By about #25, it was done. Blade was clearanced out @ $50, so each cut cost me $2.

Typical "cold cut" chop saws like DeWalt, Milwaukee, etc, run at around 1750 rpm and the blades are typically rated at maybe 2000-2500 -

Like I said, I've seen a couple 8-10" blades that are rated at high enough rpm, but they're anywhere from $60 to $100, and I'm not sure I want one bad enough to take the chance it will last.

I am, however, planning on keeping the blade option open on the "radial plaz" when I get to it, but it'll mainly be a "mini-track saw" for a plasma cutter, that will crosscut, miter, bevel, and cut radiuses for things like hoe and loader buckets, maybe "heavy duty hose hangers" for all my welding carts, etc. - I'm gathering notes and such, and will start a new thread in the Welding forum on the subject - of course, anyone who beats me to it will be encouraged to post pics, plans, results, etc, so that thread can be sort of a "one stop shopping" thing for converting a RAS to a "RAP" :=) Steve

 

[JKR]

If you want to cut metal get a metal saw. Milwaukee 8" saw will cut though 1 1/2" plate. I also use a 3/4" metal band saw, twin blade saw for pipe and rods that just need to be cut.
Using a wood saw on metal is just asking for trouble. It runs to fast an will take the teeth of the blade.
Be safe in your work and do it right. Or pay some one to do it for you.

 

[downsizingnow48]

I explained in Post #1 and Post #23 that the DeWalt turns at 3425 rpm which is compatible with the Makita 5 3/8" metal blade rated at 4600 rpm. Pls look at those notes and let me know if there is still something that concerns you about blade speed.

 

[muddstopper]

A milwaukee 8 saw is rated at 3700rpms, the RAS is rated at 3450rpms, a 8" Irwin metal cutting blade is rated at 5000rpms. Speed shouldnt be a problem as long as the blade you choose is rated for or above the speed of the saw. My problem with the RAS metal cutting conversion is climb out when cutting. The Milwaukee metal saw, as well as other skill type saws, all have a plate that keeps the saw flat on the material. Table saws work the same way except upside down and you push the material instead of the saw. The RAS is hanging in the air, free floating on a rail, with nothing except the operator to keep the blade from taking to big of a bite and hooking a tooth and climbing out of the metal.

 

[Willie B]

Is that perhaps something that sets the new to the market power hand saws for metal apart from conventional wood saws; speed? No, I hadn't studied up on rpm ratings yet. This thread planted a seed for thought, it hadn't yet germinated. A young fabricator friend swears by the metallic blades for abrasive saws. I guess I hadn't realized how slow they turn. I have a Milwaukee, quite an expensive saw, it seems painfully underpowered, especially with aluminum.

 

[BukitCase]

Blades - as long as your blade's rated speed is somewhat higher than the saw's rpm, it would be a non-issue. If you ignore this, the LEAST of your problems will be short blade life.

Saws - all the 14" cold cut saws I've seen have a speed in the 1400-1600 rpm range. All the 14" abrasive chop saws tend to run in the 3400-3700 rpm range. The one test I did showed that too fast a saw WILL dull these blades rapidly, and may also cause flying parts, which I did NOT experience.

One thing that will shorten the life of ANY blade is impatience - if you try to "power" through cuts on any material, you'll get crappy results and shorter blade life (in my experience)

Climb cuts on radial saws - with WOOD, using the saw on pull cuts is fine IF YOU'RE CAREFUL and don't let the saw get ahead of you - this takes technique and practice, and isn't for everybody.

On METAL, I would stick to PUSH cuts and a FAIRLY GENTLE approach with dual HOLD-DOWNS.

With adapting a RAS to metal, once you've found a rpm compatible blade there are also SAFETY issues -

1 - guarding. Flying metal, regardless of WHERE it enters the body, is arguably more dangerous than wood. And trust me, there are a LOT of small metal chips flying around that need to be controlled.

2 - Hold downs - chop saws have 'em, so should a RAS. I've not dug into options on this yet since MY main plan is converting to Plasma. Maybe something like a SLOTTED table with a couple of drill press hold-downs that can adapt to material size.

3 - Table - personally, I would NOT keep ANY wooden parts, either for blade or plasma use. I know the blades are called "cold cut", but still...

JKR, your concerns are noted and agreed with - but sometimes people wanna push the envelope and/or don't have the extra money available for the "real" deal - plus, this IS the "build it yourself" forum So some of us who can identify with some or all of these reasons will do our best to advise on the SAFEST way to do these (possibly un-safe) mods.

Unique operations - For metal cutting, I have two horizontal band saws, an abrasive 14" chopsaw I almost never use, thin cutoff blades for side grinders, two recip saws, hand hack saws, O/A cutting torch, plasma cutter, a Porta-Band, and they all have their uses/strengths/weaknesses, BUT

One thing NONE of them can do to my satisfaction, is to cut out ONLY THREE SIDES of a piece of square tube with left and right ACCURATE 45 deg. cuts, so the REMAINING side can be bent closed and welded, leaving a square corner with a perfectly smooth outer corner -

The only thing I'm aware of that CAN do that is one of the HIGH DOLLAR band saws that does NOT hinge at the rear, but instead the ENTIRE SAW floats up and down on linear ball bushings so the BLADE IS ALWAYS PARALLEL to the table - if you can find one USED, it'll still cost you anywhere from $1500-$3000. A bit much for a home shop

I think there's a way to accomplish that with a modified RAS, but to do it SAFELY isn't gonna come easy. Eventually I'm gonna try, but it isn't my MAIN goal - as stated earlier, it's a "poor man's plasma table" since the 4x4 CNC plaz I'd REALLY like to have is in the $10k range.

Man, this is getting long even for me :laughing: I probably forgot what I originally intended to say... Steve

 

[Willie B]

I think the radial arm saw will continue to serve the same purpose it has since new; a place to pile objects I have no other place to pile. Oh well.

 

[muddstopper]

I think the radial arm saw will continue to serve the same purpose it has since new; a place to pile objects I have no other place to pile. Oh well.

Thats exactly where mine has been for the last several years. I had to climb over a bunch of junk just to take the picture I posted

 

[sandman2234]

My step-father took me out to the garage one day, and told me that his radial arm saw was to be mine, when he was gone. Mom asked me what he wanted when I got back into the house, and was surprised when I told her. When he passed away, Mom said my brother wanted the saw to stay there so he could use it to "fix" stuff. I told her that wasn't what he wanted, but if she decided she needed it there, I would leave it there. Ten years later it is still there...lol!
David from jax

 

[ultrarunner]

^^^ Hear things like this a lot..

My Grandfather had given me an old clock that had been on the wall at his place of business when he opened in the twenties and it was old then... he also gave me an old 8" table top lathe.

When he passed, I was 13 and my Uncle claimed it and that was the end of it...

My neighbor wants to sell his Craftsmand circa 1980 Radial Saw... he brings it up every couple of months... never needed one yet and don't know where I would store it...

 

[downsizingnow48]

Nobody is more interested in keeping all my original parts intact than me. So I appreciate various safety comments. Bukit and Stopper have made specific suggestions on clamping. Will revisit the clamping arrangement (currently one milling machine clamp) and make use of two sturdy holddowns. I believe other important questions raised about blade speed and push/pull have been resolved. Have installed a full shroud for additional safety.

To clarify one point. I am not using the RAS to save money, or for convenience. True, I am a believer in build it yourself rather than buy it yourself. But in this case I didn't find anything that would do the job so buy wasn't an option. I read every thread on metal cutting on TBN (there are lots of excellent posts). Have also checked out a couple other forums. Did not see a tool identified (up to light commercial scale) that would leave a perfectly square finished edge on mild 1/2" steel up to 12-16" wide with easy setup, no-measurement repetitive cuts, and no cleanup grinding. The modified RAS does that. I could have missed something though.

I will get some square tubing and try the bevel cuts described by Bukit, and the compound cuts described by Stopper, to see if it will meet those requirements too.

The issue on bevel and compound cuts of course is controlling the feed. Hand held RAS, as several have pointed out - and my own experience is the same - is difficult enough on wood.

I believe I can install a lead screw/handwheel arrangement in the cast iron arm, similar to a lathe or milling machine. Have ordered the parts. That will allow precise slow movement of motor head and blade into the work and address the grab/jump/kickback questions that have been raised. I will provide an update on that after installation.

In the meantime my wife and I are headed to the coast for a week of vacation after all the holiday family visits. So if I am incommunicado for a while it is definitely not for lack of interest. Many thanks.

 

[muddstopper]

Thats not fair!! You cant start a build and a thread like this one and just take off on Vacation. I cry foul!

Seriously have a nice vacation and enjoy yourself. I think, maybe, I can force myself to wait until you get back and finish the project.

 

[ultrarunner]

Enjoy the coast... it's been pushing 70 degrees here in the Bay Area with blue sky and calm... and plenty of all the ice skaters at Union Square in shorts and swim suits...

My city got 3.5" of rain for all of 2013... about 1/5th of normal...

 

[downsizingnow48]

It took longer than I thought to fabricate the lead screw arrangement for the DeWalt metal cutting radial arm saw. There is not much room to work in. So it took a lot of measuring and whittling to get everything in place. The pictures below show what it looks like. It uses a standard 3/8" acme thread lead screw. The hand wheel and lead screw assembly works like a charm - extremely smooth, in fact cutting 1/2 steel feels just like taking a light cut on a milling machine. No jerkiness, grabbing, etc. And your hands are up on top of the saw where the hand wheel is, rather than down on the motor head. No more pushing and pulling within inches of the blade.

To explain the assembly from right to left:
1. jam nut.
2. handwheel with set screw.
3. jam nut.
4. oilite thrust washer.
5. thrust plate (this screws to the front of the cast iron arm in place of the original cover plate).
6. oilite thrust washer.
7. jam nut.
8. jam nut.
9. front guide (this is located by 1 pin and 1 stud using existing holes in the motor yoke).
Also, the front guide carries the 3/8" acme thread lead nut. The front guide and lead nut are pinned together with four #7 tapered pins that are hammered in from the thick end and then peened over on the thin end.
10. rear guide (also located by 1 pin and 1 stud using existing holes).
11. finally, front guide and rear guide are clamped together by four lengths of 10-24 threaded rod with vibration resistant nuts.

When I got started on this I did not foresee making the lead screw assembly, but now see it as an essential part of the modified saw. It provides increased control, quality of cut, and safety.

I need to trim the thrust plate for cosmetic reasons, and make a few other adjustments. Also need to install the upgraded clamping arrangement as previously commented on. The saw already exceeds my expectations with respect to flat cut 1/2 steel which is what I wanted to do. Sometime in the next few days I will go get some square tubing and see how it works on the more complicated cuts suggested by others.

As always I appreciate all comments. In fact it was the safety-oriented comments that got me thinking about making the lead screw assembly.

 

[RAECOREP]

Having a counter weight pulling back on saw really helps on the grab & jump issue.

 

[downsizingnow48]

Thx for suggestion hadn't thought of that --

 

[J_J]

How are you cutting, pulling into the metal or pushing into the metal.

 

[k0ua]

Well I am late to the party.. I have owned a Radial Arm Saw for about 30 years and have made thousands of cuts on it. Will it climb and push the saw head towards you? Yes, and it is caused by going to fast and or hitting a knot in the wood. You must be prepared for it to happen. I have had it happen many times, and still have all of my fingers. It has a stop at the end of the track, it isn't going to come back and cut your heart out. What happens is you pull too fast and it climbs and usually the motor stalls or nearly stalls. Common sense and technique go a long way here to prevent this.

I have never once tried to push a radial arm saw into the wood. For one thing this is not what the users manual tells you to do, and for another it would reduce your capacity considerably. I use the radial arm now for crosscuts only. It is convenient for throwing long stock up on the table and cutting.

Now as for ripping, my advice is forget it if you can. I have ripped several boards on the RAS, and that was the prime reason to buy a good table saw. RAS by design is a really poor design for putting sideways stress on a saw head hanging out there on an arm.. It is just not really good for this.

It will make compound cuts of course, but is not nearly as easy to set up and reset as a good compound miter saw. Beside that is also makes cut marks in your table. That is why I have a compound miter saw. My RAS manual says it will do it all.. unh huh. Like most things that will do it all, it may do it , but there are a whole bunch of other things that will do the job a bunch better and safer.

So bottom line I still use my old RAS a lot, but I sure use the other saws when they are much better for a particular purpose.

 

[BukitCase]

Kinda what I posted earlier in the thread James - or (unlike my NORMAL methods ) to put it more succinctly -

The safest AND most dangerous tool in your shop is YOU... Steve

 

[downsizingnow48]

On JJ's question, I have done it both ways now. With the two milling machine clamps (see picture) to stabilize the work, and the 3/8x12tpi lead screw to stabilize the saw, I don't see a difference in ease of control. That being so, going forward, I will use it the traditional way (pull into work). I agree that is generally accepted RAS practice and also closer to the motion of the metal cutting chop saws.

By the way JJ, while I have you on the phone, so to speak, I have been researching my next task which is a thumb for the backhoe. In doing so I have been reading back through many TBN threads. THANKS for your longstanding support on hydraulic questions which I am now benefiting from.

On use of the radial arm saw more generally, I agree with pretty much everything James has said. What I would add is that the radial arm saw is likely at its best in a cabinet shop environment where it doesn't get moved around, and generally is not used on wood with knots, crooked grain, warp, or twist. Or wood that looks nice but has hidden stresses just waiting for the blade to release. There are a lot of things that can make the saw want to jump, perhaps encountered more frequently in a worksite environment. I used mine a lot - for several years - when I was just getting started, and I don't think my technique was any worse than others. I pulled when I could, pushed when necessary. But I quickly learned it could not be safely used for ripping, no matter what you did, so I got a table saw for that. Then, as soon as they were generally available, I got one of those Rockwell motorized miter boxes with the particle board table for small trim. And then a few years after that, one of the first Bosch sliding miter saws for just about everything else. Somewhere along there I gave away my first DeWalt, and didn't think of it for 20 years. That is because no matter how good a technique you might use with it, for almost all purposes there are easier, safer alternatives.

The heart of the matter is what Bukit says about safe and dangerous tools. Much of this thread as it turns out is about safety. I am extremely appreciative of these comments, which are based on many years of collective experience and a spirit of helpfulness.