Riping and Crosscutting - Cuts are not straight - ideas? (1 Viewer)

[Jeff Elliott]

Hi All - I've got a reasonably nice cabinet saw (jet 3hp) with a good Oldham combonation blade. The table and fence have been aligned and are all within spec. Also, runout has been checked and is also acceptable. I use a vibration dampener with the above mentioned blade.

When cutting mdf, I can see the blade "wiggle" left and right. It's sort of like the blade has bogged down with sawdust and binds. If the feed rate is varried at all, the wiggle is worse. I can lay the ripped material on the tabletop and visible see indentions where the blade has moved and therefore not cut straight.

Is this operator error or something else? Any and all suggestions are welcome!

Thanks
Jeff

 

[Darren_T]

My guess, a bit of operator error... possibly a dull blade, are you an experienced woodworker? I don't want to insult you

If you are fairly new then explain where your hands are and where you are looking as you cut and I'll try and critique your method. If you are experienced I'll try and help you figure out what's up. My cuts with MDF are like glass on my 3hp cabinet saw using a Freud combination blade. The blade cuts like it's going through butter.

It really sounds like you aren't feeding well or the blade is really dull. Do you get any burn or smoke? Any resistance as you cut?

One thing to consider is MDF will really reveal any problems with technique because a carbide blade will eat away at the sides if you vary your pressure on the piece at all where hardwoods will be a bit more forgiving. You really have to keep the piece flat against the fence.

 

[Chris Keen]

And how sure is sure? Double checking that your setup is spec is important, but what you're talking about with wobble has me concerned. If there's no runout on the arbor, then it makes me think of the blade. Is the blade a thin kerf or normal thickness kerk? Also, are you quite sure the blade isn't warped? If you are using a normal blade, a damper/stabilizer should NOT be necessary, and in some cases has been shown to create worse performance. The first two things I'd ask you to try is to shitcan that dampner, and if that doesn't change some things, shitcan that blade and try a different one. If both of these things don't change it, I'd have to agree with Darren in that it starts to look like an operator error. Also, how large is the piece that you're working with, and how much cut. In other words, if you're trying to wrestle a 4'x8' sheet good of 3/4" MDF (which is heavy as heck) and make a precision cut, you're likely going to be paddlin' upstream unless you have extension and outfeed tables, and a good sliding table to control the sheet well. In short, help us help you by giving some specifics. I'd bet dollars to donuts that someone here will tip you off to what is the culprit, and you'll be in cutting bliss before you know it!

 

[Jeff Elliott]

First, thanks for the suggestions so far! I'm going to try them and will report back with the results. I did think of a better way to articulate what's happening:

Essentially, When I start the work through the blade, I can watch the cut and the blade is perfectly focused. When the problem occurs, I cannot focus on the blade because it's blurred from moving left and right instead of staying straight up and down. It's like it is choking on sawdust and therefore wiggles to make room for the waste to exit?

Now, here's some answers to questions you've asked:


- The issue occurs regardless of the size of the workpiece. I can try to rip a 10x36 piece out of a 20x36 piece and it will happen. I do have an extension table which I agree helps tremendously.

Thanks again and keep those ideas coming!
Jeff

 

[Chris Keen]

Well, I would suggest that you get a dial guage and a magnetic stand to help with dialing in your setup (if you don't already have one). I hate to reference Harbor Freight, as a lot of their stuff is basically just cheap $#!+ ... but at the same time I hate to have you purchase what is essentially the same quality item at far too expensive of a price. If you check HF, you'll find that they run both the magnetic base and the dial guage on special from time to time, and you can pick up the two for a total of around $20.

I would make sure that your blade is parallel to your mitre slots; your fence when locked down is parallel to your mitre slots; your arbor has no run-out; your blade has no run-out; your mitre gage is 90 degrees to your blade/miter slots - you can get a lazer cut plastic 90 degree triangle for about $5 at office depot or the likes in the drafting sections.

You can check to see if the arbor for run-out with the dial mentioned above. You can also check the blade (when mounted on the arbor) by turning the arbor using the belts and watching the dial.

You might also want to see if you have a carbide tooth missing. I can see where this might cause some harmonic distortions when spinning and under some frictional load of cutting material.

I still wanna put a fifty cent bet on the blade or the vibration dampner being the source of the problem. If you have another blade, try it and see what happens. Maybe you could even borrow one from a friend who has one.

Oldham blades aren't generally regarded as very top-notch. They make a slew of cheapy blades, but truthfully they do have some pretty good ones in the mix too. I hope we're talkinga bout one of Oldham's better blades here, and not some cheapy. Also, FYI, if you didn't already know, there are plenty of good source blade manufacturers out there -- CMT, Freud, Amana, Systematic, just to name a few.

I certainly hope you get this worked out. I hate to think that you've got a nice piece of equipment there that isn't doing right by you.

Oh, one other thing that comes to mind. Is this a new saw, or used? I'm wondering if there could be any possibility of some cracks or broken mounts in the arbor that is causing some slop that isn't apparent until it's under cutting load.

Also, the cut rate speed with MDF shouldn't be too slow. You should be able to cut through it pretty darned fast. Doing it too slow will cause burns and poorer cuts from my experience. YMMV.

 

[Darren_T]

The first things I'd check would be the following as per Chris' suggestions:

1. Check to see that the blade is parallel to the miter slots

2. After step 1 check to see that the fence is parallel to the blade, you can also parallel the fence to the miter slot and then adjust slightly if necessary to the blade.

It really sounds like the blade is binding somehow.