Table Mounted Jigsaw
18 replies to this topic
Posted 26 June 2011 - 09:46 AM
I have started a new thread for this, As the original thread was not about home made tables, but about a specific product, the Rockwell BladeRunner.
Reviews of the original product had two main criticisms, straight line cutting and vibration:
Straight line – the wandering blade is typical on hand held jigsaws and the problem carries over to the ‘blade runner table saw’. This occurs because the blades are flexible and try to take the easiest path. On thicker, stronger materials, this tends to be off to one side.
By moving the guide wheel to the end of the blade, I have restricted the movement of the entire blade and even cutting 40mm (1.5”) meranti wood, I was able to hold a straight line (cross cutting).
Vibration – the first time I fired up the jigsaw table, I smiled, as vibration was minimal. The smile was reduced to a frown when I started cutting some wood though. The vibration is strong enough to be considered a nuisance.
The vibration is not caused by the reciprocating action of the machine, but by the non-cutting stroke of the blade. This tends to lift the work piece and then slams it down on the cutting stroke. This vibration is not that evident on a hand held jigsaw, as you are counteracting the non-stroke by pressing down. If you release the down pressure on the hand held, you will rapidly lose control of the machine.
The vibration is minimized by pushing down firmly on the work piece. If I was cutting more than a few blocks, this would soon become tiresome. This problem cannot be solved with the jigsaw table, rather it is a problem that needs to be addressed with the design of the cutting stroke, which needs to be elliptical, pulling back on the non-cutting stroke.
Efficiency – Not mentioned in the reviews, but I see this as a problem. The cutting speed is slower than the band saw, I would guess half the feed rate. This would make sense as the blade is only cutting 50% of the time. I would imagine that this would also be evident on the blade runner machine.
I wanted to demonstrate the straight cutting qualities, by cutting the length of a meranti block. The cutter just would not entertain cutting along the grain. Even when I turned the block on its side of 25mm (1”), the blade would just not cut, only resulting in violent vibration, which I was not able to counteract with down pressure. I moved over to the bandsaw and the same cut was effortless.
Application – I built this machine mainly to cut those items that cause breakages on my bandsaw, namely metals. With a metal cutting blade, I have to go very gingerly, even when cutting 5mm brass plate. 6mm diameter steel rod always breaks the blade. Recently I have been doing a lot of work with 12mm diameter steel threaded rod and 12mm diameter SS rod. I would not even think about attempting these on the bandsaw, but was hoping that the jigsaw table might do the job, especially as I have a job coming up requiring the cutting of 16mm diameter threaded rod. I need to buy some metal cutting blades, but I won’t be holding my breath.
Conclusions – I will continue to test the jigsaw table with different blades and materials, but I cannot hide my disappointment. After I complete the tests and if I cannot find a use for the jigsaw table, I will probably convert it into a mini router table. I won't be retiring my bandsaw any day soon.
On the strength of this experience, I would be very wary of investing in a Rockwell BladeRunner, unless I had the opportunity to test one out first hand. Here are photograph of what I made:
Posted 26 June 2011 - 10:22 AM
You never cease to amaze me Dave. Pretty slick build. It's a shame it didn't work as well as you'd hoped.
Have you thought about using abrasive blades on your chop saw to cut the metal rods? It may require a slow feed, but should be doable.
Posted 26 June 2011 - 10:31 AM
I keep forgetting about abrasive wheels. I have no budget available for new tools, but I have just finished my slot cutting jig, which is basically a chop saw. It carries a hand held circular saw, as that is what I had available, but I am thinking of making another beam to mount an angle grinder. This would solve the problem. Thanks.
I will have to shoot some video, now that I have solved all the problems on the slot cutting jig. I guess it is allowed to hijack your own thread
Posted 26 June 2011 - 10:40 AM
Very nice Vodkaman, your work never ceases to amaze me. One thing you might be able to do is move the bearing back under the table top so that you can rig an adjustable hold down piece across the top, beside the blade to control the up movement of the wood. It would need to be a close fit so that the wood could move freely. One thing that causes the difficulty in cutting thick material is that the length of stroke is shorter than the material thickness and the blade can't clear the saw dust from the cut. Fewer teeth with more set might help. I wouldn't give it much hope, especially if you have a band saw. Musky Glenn
Posted 26 June 2011 - 10:53 AM
Not sure if they're available to you locally, but abrasive blades that will fit a 7" circular saw are available. Same arbor diameter as well. Might keep you from having to build a whole new setup for a grinder mount.
Posted 26 June 2011 - 11:04 AM
I think the 1.5" depth cut was a little unfair of me, seeing as this is not a cut that I would normally undertake. Such cuts would normally be taken to the table saw.
I really want to keep the guide at the top, as it solves the main problem of the wandering blade. But I will consider this in the future. I have not given up on this project yet.
The 'hold down' idea is good and I am already working on an idea using strong springs, a release lever and a bearing to apply the down force. This should allow the part to slide freely and maintain the downforce. I may be able to redesign the beam to make room. The first design was all about stability for the guide wheel. Now that I see it in operation, I am thinking that I could probably get away with a less rigid beam.
This machine looks far too simple for a Vman creation. Time to complicate it up a tad.
Thanks for the input Glenn.
Posted 26 June 2011 - 11:09 AM
"This machine looks far too simple for a Vman creation. Time to complicate it up a tad."
I didn't see any CAD drawings on your latest creation either. You might be slipping just a little Dave.
Posted 26 June 2011 - 11:25 AM
Posted 26 June 2011 - 12:06 PM
While aluminum is pretty forgiving many other metals when cut with a toothed blade like a much lower blade speed.
I cut aluminum plate upto 1.25 inch thick on my table saw with standard carbide wood blades at wood speed, but its right at the top end of speed for cutting aluminum. For the thicker stuff (more than 1/2") I spray cutting oil on the blade every inch or so of cut. I think brass might be just a tad too much to hope for decent results and decent blade life. Some other aluminum alloys too probably.
The thing to think about though is as you slow down and add coolant you can cut even steel very reliabley and very cleanly with a toothed blade. I'm talking about saw blades here. The local steel vendor uses a hude circular slow cut steel blade (alloy unknown, probably from Tounrey) to cut stock pieces of both hot rolled and cold rolled steel to length for customers.
Abrasive blades work, and I use them quite a bit myself because they work on the much faster "wood" saws commonly available at a reasonable price, but they have two major flaws. One should be obvious. They throw red hot sparks everywhere. Forget to put away some cleaner or solvent and you could have a problem in a big hurry. Even woods and plastics will be eroded away by the embers showering on them. Your quite inventive wood framed machines would certainly take some damage. Some metals will be worse than others with steel and alloys with magnesium being right up there. Just please keep a fire extiguisher handy. I have five of them placed around my shop for when I am working.
Getting back to your sabre saw. There are models that have an orbital motion. The blade moves forward and back when the stroke reverses. I honeslly think it cuts a little slower than a conventional reciprocating sabre saw, but the arm and shoulder fatigue after using it for an extended period is definitely less.
An alternate idea for your specific application might be to place spring loaded feed rollers on your table to reduce the amount of downward force you have to exhert by hand to reduce vibration. Perhaps even make them driven so that you will get better consistency of feed rate and better cuts. One of the problems I have found with almost everybody (myself included) is after a while they start to rush a bit more than the equipment can handle and things go bad. Once they realize it they are beginning to get tired and their judgment will be off. They will often slow down too much and in materials like wood will result in burn marks.
Edited by Bob La Londe, 26 June 2011 - 12:09 PM.
Posted 26 June 2011 - 12:22 PM
I just realized I forgot the other major flaw of abrasive blades. The one most people never notice.
They throw abrasive grit everywhere. Most people only notice when they sweep up their work area, but that abrasive grit gets into everything. Equipment in the vicinity will take damage and wear out bearings faster over time. Machinists who have to use an abrasive blade for something on their lathe or mill will cover every possible place they can with foil or paper to keep the grit off their precision surfaces and out of their bearings.
Posted 26 June 2011 - 05:02 PM
Hey Vodkaman - don't give up on the jig saw table just yet. I had a brain phart just now a thought 'what about using the jig saw tool but instead of a table just to hold the saw and blade convert the table to a 'scroll saw' type table. Use the motor as the drive for a homemade scross saw blade holder and pivot arm. That way any type of scroll saw blade could be used. Could use jewelery saw blades, blades for wood or even hacksaw blades for rods and thicker metal materials.
I'm not as creative as you but I bet you could come up with something. Don't have to buy a whole scroll saw but just come up with some hardwood frames and some bolts, screws and brass bushing for a pivot point. The trick is coming up the with connection between the jig saw stem and the saw blade holder/rocker arm. Like I said an idea or concept. If you decide to try it I would like to see pictures. I already have a bandsaw, table saw and scroll saw for doing woodwork so I would not undertake this adventure myself.
Edited by EdL, 26 June 2011 - 05:04 PM.
Posted 26 June 2011 - 06:23 PM
EDL - I think I am following, you are suggesting using the motor and build a scroll saw. It is a good idea and although I have never heard of anyone actually building a scroll saw, I think it is doable. However, I have little use for a scroll saw. I was shooting for a replacement for my bandsaw function and heavier work. If I had the funds, I would just buy a better bandsaw.
Bob - thanks for the information. I realize that I am probably backing a loser here, but the experience will serve me in the future. I feel like I have taken a hit for the team, saving anyone else from wandering down this path. I will know more when I buy a selection of blades. I cut some lexan with it and it did that well, even with the wrong type of blade. So this machine will be kept for lexan, saving me the chore of switching the bandsaw blade for such small jobs.
Thankyou both for your input.
Posted 02 July 2011 - 04:25 AM
Matthias Wandel's Woodgears.ca is my most admired wookworking thinkerer I have found on the web. I'm sure you will find lots of inspiration in his site.
One that could immediately fulfill ur bandsaw dream:
Posted 02 July 2011 - 06:16 AM
LP - That was so impressive. Makes me want to go hide somewhere with my meagre skills.
Thanks for posting.
Posted 02 July 2011 - 01:14 PM
Your are welcome, take a good look at how his bandsaw guide is constructed, would work well with ur jigsaw table setup too and get it to be exactly like that Rockwell Bladerunner. A well supported jigsaw blade will go a long way in assuring a clean cut plus act as a hold-down for your workpiece too.
Posted 03 July 2011 - 07:15 AM
The video has started the cogs inside my head turning. The blade support beam on my table, although it does its job, is quite a hinderance. So I am considering a double plate with spacers, single beam, reaching from the rear of the box, similar in design to the frame of the bandsaw in the vid. The stiffness the he attained with his construction was quite amazing.
I am actually using the table quite a lot, mostly for polycarbonate, for which it works quite well. I am also going to keep my eyes open for an eliptical cutting action jigsaw. I have owned one in the past, but didn't appreciate it at the time. I think the eliptical cutting action would solve a lot of the problems. It is all down to how much I have to pay. Modifications to the box will be easy to adapt to the new jigsaw, as it is screwed together. I will probably have to make a new brass mounting plate and do a bit more routering.
Thanks for your input.
Posted 17 May 2012 - 09:37 AM
You EVIL man!!! Why did you have to lead to this thing that I now MUST have!!!