Metal-cutting circular blades

I saw these at lowes, they come in 5 3/8", 7 1/4", and 10". They're not cheap blades, but they indicate they are for cutting metal and run at 5000rpm. Anybody use these? How much life do you think you'd get out of a blade? The package indicates the blade can be resharpened.....Cost to resharpen? How about the merits of mounting one of these on an old beater miter saw dedicated to cutting metal?

I have not used this brand but there are similar ones on the market for less money - Google is your friend. Yes they do work well if you just let the blade do the work and not force it. I cut all the steel tubing for my english wheel 4" x 10" x 1/4" wall with one and it took less than a minute per side. I also cut out the corners of the 3/4" top of my fabrication table so I could mount some receiver tubing to hold tools, all with the same blade and it still cuts like new.

You do have to cover up and wear eye and ear protection because there are little blue chips that go everywhere. It is the fastest way I have found to make these kind of cuts.

I have used them and yes, they are expensive, but compared to a friction grinding wheel on a chop saw, they are SO SO much better, faster, and cleaner. Cuts are also much cleaner in general. Make sure cutting tips are carbide.

I have used them at the plant when we can't get a hot work permit, they are limited in the type of metal and thickness that they can cut, but seem to work well

I have a 14" carbide chopsaw (milwaukee) and their little hand held saw. It's damn near faster than my power max 45 on 1/4" plate.. and my plasma will do 1"/s mirror smooth.

Like everyone said. Wear a full face shield, ear protection, a scarf, make a sacrifice to the tool gods, hide your children, tie your dog up, make sure the wife is at work..

You'll be finding little 1/8"x.030 chips EVERYWHERE.. usually when they're still 500F+.. but it leaves a nice clean edge! I prefer my chopsaw with it's shields, but sometimes you just gotta use the circular saw. Works amazing on expanded metal if you don't rush it too. I used mine to (very slowly) square up a 1" table before it went to the blanchard grinders.

I've used them in a circular saw to cut plate. Worked way better that I thought it would and leaves a nice edge. The guys above aren't lying about using a face shield, hearing protection, and covering up. Those little chips hurt like hell!

jrlp said:

I used mine to (very slowly) square up a 1" table before it went to the blanchard grinders.

Click to expand...

I'm working on a design for a table right now, and I'd love to do exactly what you did with the top.

What size is your table, how big was the blade you used to trim the edges, and how much is the blanchard grinding gonna cost?

Thanks!

-Chris

Hi Chris,

I made a small setup table for TIG. I used the Milwaukee 9" (I think, it's been a while since I've used it, I use my plasma for 99% of stuff now) dry circular saw. I made it small, as I stuffed a small toolbox in the frame underneath it. I copied the design from a member on WeldingWeb, but his name escapes me at the moment. I had it blanchard ground at a place about 350 miles away for, if I remember correctly, around ~$200. It's a small table, around 20"x48 because I got a great deal on that piece that was a drop. I was really hoping for 2'x4' but.. I just couldn't pass up the other one. It ended up working out well, as it's very easy to setup and reach across. I really don't miss those 4" (Never thought I'd say that!). I drilled/tapped/countersunk on 4" centers. I went with 1/2-13 because Bridgeport step-block sets are usually 50% the price of any other type(size). I believe I have 2 sets of the cheapie Imported sets from Use-Enco.com when they went on sale for about ~$15 dollars per 30-40pc set. A few 1-2-3 blocks, 90 degree plates, etc.. and you can jig pretty much anything.

I use short countersunk pan head screws to plug the holes flush with the top. I keep a few long ones threaded through the outside 2 rows on the perimeter because those aren't kept out of the elements by the toolbox / frame. I douse each one with copper anti-sieze to keep the holes coated, so the bolts don't seize in the holes with grinding dust / slag / heat. It took a while, but I set the stop on my magdrill for each step, then did each hole step by step.

I don't know if it would be faster to pilot drill all the holes, then go back and full-size drill them all, then go back and powertap each one, then go back and countersink them all. I did each hole at a time. 1/8" pilot, 3/16", then 27/64", powertapped, then countersinked. I used a caliper to set the cs depth each time.

It took a long time to do, but not nearly as long as if I did it by hand. I used lots of lube and went slow. My 1/8", 3/16", and 27/64" drills made it through unscathed without resharpening, as did the cs bit. If I were to do it again, I would have bought a 1-size under annular cutter, then reamed the hole to size to tap. I think I would have been done in half the time if I did it that way. In all, I think I'm ~500 into it. Most of that was the top box stuffed inside of it, and the fasteners / jig clamps. Truthfully, though.. my 2'x4' roll around with a 1/4" top gets used more, as I don't jig that often. But when I do, the table is indispensable! Doing header modification, or building turbo manifolds from scratch, it's real easy to keep everything on the same plane or perpendicular. It's also used for valve cover modifications, cast aluminum repair or anything with a flange that needs to be kept straight and flat. I've written a novel, I'm sorry. I have insomnia and it's 4:50am my time. My SO just gave me another dirty look, it's time to go back to bed, HA. 'Night

Hi jrlp,

Many thanks for the detailed reply -- it's extremely helpful. Sorry about your insomnia, but I really appreciate your taking the time to provide such good info!

I know what you mean about the size. I usually make tables in the range of 36" x 48", just to be sure I have enough room, but most of the time, something quite a bit smaller would work just fine.

As far as drilling and tapping the holes goes, you seem to have done it the way I would have. I think keeping the drill locked in place for all the steps on a given hole is the way to go. I like your idea about the annular cutter, though, so I'll look into that.

When you had the top ground, did you have them clean-up both sides or only one? It seems like having the underside flat would help keep the top flat.

Thanks again,

-Chris

Well, kind of. I measured it quite a few times from every direction, and it was only around 1/8" off diagonally in the center. I spent some time trying to flame straighten everything, and from what I could tell (using a straight edge and caliper) it was pretty straight, at least with the heavily rusted surface. I only had one side done, but I cleaned off any burrs / dents / chamfered the edges on the backside with a 7" grinder before I sent it off. I think the lowest side was around .970". I don't think I'd go back and change it if I could, it worked well enough for me. But, I am not holding real tight tolerances on what I do. Realistically, 30-50thou is fine.. I'm sure I could get it down with better jigging and taking more time on it, but I haven't had the need. I've only once set up something I tried to keep within from warping and that was an axle housing, welding the tubes in. It worked well, but I did borrow an alignment bar setup down the middle + table and it worked VERY well.

Have a good one!
John

Whatever the carbide they use, carbide goes past its mechanical limits and breaks down anywhere from 500SFM, to 900SFM (surface feet / minute)
The cobalt that is the glue that holds the tugnsten carbide, melts atound those speeds; the reason there is a delta in the speeds, is the fact that different carbide grades will have less or more cobalt.

All that being said, for a 7" blade, max speed should be (RPM = (SFM X 3.82) / diameter) (500X3.82) / 7 = 272 RPM...

Not saying it won't work, because of the small radial engagement of the teeth ,with the workpiece, but as soon as you have more that 8 teeth in contact or so, you are looking at breakage / very fast tool wear.

I am in carbide tooling, this product is OK but too much of a compromise, IMHO if you are doing work with quality tools.

my 0.02$

I believe that the only reason this product survives at the high SFM is because it is cutting thin materials and each tooth is engaged with the work for a short time, followed by a much longer "cooling period" where it is rotating in air.

Not having a string of fancy letters behind my name, I can't tell you how this interacts with the impact load of the intermittent cut, but I do know that a slow feed/lighter cut will lessen the impact load and also the heat factor from the high SFM. Thus a light cut is critical to blade life.

If you could slow down the RPM, it would make the blade last much longer, but I suspect that the feed rate could not be increased enough to keep the same production without some sort of controlled feed and very rigid setup, in other words, a Rage saw.

So can the metal cutting blades be sharpened? I have some wood cutting blades from regular steel to carbide tipped and some 4"? diamond blades for concrete (I don't need). I have a Foley 387 Filer.

Regarding whether these blades are limited to cutting thin metals, I'd suggest taking a look at Jim Shaper's 2008 thread on building a welding table in the PM Fabrication forum here:

http://www.practicalmachinist.com/v...jet-plasma-welding-fab/welding-tables-163865/

He uses a Milwaukee hand-held circular saw to cut 1/4 x 6 channel.

So it would seem that, regardless of what the theoretical limitations are, this kind of blade can successfully be used for this kind of work.

Here are a couple of his photos:

Correction, the saw he is using is specialy designed for carbide saws. They turn a much lower speed vs. wood saws.

Milwaukee Metal Cutting Saw:
http://www.milwaukeetool.com/tools/...ing-saws/8-inch-metal-cutting-saw-kit/6370-21
No Load Speed: 3700rpm

Milwaukee Wood Cutting Saws.. anything from 7.25" to 10.25" go from 5,200rpm to 4,400rpm.

That's the difference. If you have a saw designed for metal cutting, it's going to spin slower than even the slowest wood saw. The Milwaukee saw has a chip box that works very well for catching most of the chips before they find exposed skin. The saws the OP posted are 'retrofit' blades for wood saws.

Jastech, yes, they can be resharpened / retipped. I will link you the company I use when I find a receipt. I think it's about 50 to retip/sharpen my 72t to 90t 14" blades.

Cegreen, That's the purpose-built metal cutting saw. It's hard to compare those blades at much higher rpm than the saw designed around metal cutting to begin with. I'll tell you this, the Milwaukee will slide through a 4"x.25" piece of bar stock in under 3 seconds, only reason it takes that long is because I try to engage the teeth gently and not feed too fast.

Thanks for the clarification, jrlp — I stand corrected. I've heard nothing but good things about that Milwaukee saw, and it is now at the top of my wish list.

I noticed on the Milwaukee website that the factory-supplied blade is not tungsten-carbide tipped, but rather cermet-tipped, and therefore I suspect it is not really comparable to the carbide blades mentioned earlier in this thread.

Is this an accurate assessment?

-Chris

Hi Guys! some really informative posts and cleared up a lot of the questions that i was going to ask! haha, one of the other things i was wondering was what type of blade to use? as some people are saying different materials and i am no expert believe me! i am considering maybe diamond material? what's everyone's thought's?i was thinking maybe these <a href="http://www.ftisupplies.co.uk/" style="text-decoration:none;" "color:black;">diamond blades</a> from fti supplies. any help would be great! thanks