Need help with ripping MDF

[roybfr]

I started making my control panel (UA) today and noticed that I may have a problem with my table saw. The long cuts were a little wavey, noticable when I would set the side on a flat surface. I am not sure if it is a problem with the rip fence slightly moving or the blade that is on the saw, or just the nature of the beast. I have had the saw for several years but mostly use it for repetative short cuts when making frames. I am using the general blade that came with the saw, so maybe that is part of the problem. I am concerend that when I got to rip the MDF for the cabinet that it will be a real problem. I do have a 6" and 10" circular saw that I could use instead with a guide to keep is straight, but would rather figure out what is wrong with the table saw.

Any help would be appreciated.

[NoOne=NBA=]

It is really hard to push a full sheet of wood through a table saw, and get a GOOD edge on it--even using rollers for infeed and takeoff.
I used a sawguide/circular saw combo for all my long cuts.

I even used it to do the straight parts of the areas where I have inside curves on my cab.
Once I had the cut most of the way to where it needed to be, I would switch to my jigsaw, and finish it up.

[DrewKaree]

I am not sure if it is a problem with the rip fence slightly moving or the blade that is on the saw, or just the nature of the beast. I have had the saw for several years but mostly use it for repetative short cuts when making frames. I am using the general blade that came with the saw, so maybe that is part of the problem. I am concerend that when I got to rip the MDF for the cabinet that it will be a real problem.

You need to describe your saw a bit more, but from the sounds of it, I'm betting you have one of the ~$100 "table" saws, as that's a common problem with those and larger sheets of wood without setting up an auxiliary table around it to support the wood AND the fence usually isn't as stable as those found on larger, more expensive saws.  Changing the blade won't make your cuts straighter, but it probably will make your cuts smoother if you pay for a decent 80T carbide toothed blade.

If you're worried about using your circ saw, fuggedaboudit.  The 4 foot clamp I use won't work (probably) for your MDF, since it's width will be more than 4' and you need something for the longer stretch too...go get yourself an 8' lenght of angle iron, mebbe two if you want to cut the second one up for shorter saw guides.  Clamp them to your workpiece (taking into account the space from the edge of the shoe and your blade) and just push the shoe up against it and saw away.  When you're done cutting your pieces, mebbe you use your "saw guides" for added support in certain areas in your cab!

OH, and if you haven't already, change the sucky (usually) blade THAT came with.  You'll probably LOVE a plywood or laminate blade, although you'll have to go slower than you would with the blade that you're used to.

If I'm wrong about your saw, and you paid a lot of money for it and it's a biggun, please forgive me, I'm guessing because there wasn't enough info on the saw.  If it's a saw in the $200-400 range, you should have a Biesemeyer fence for that saw (or VERY similar copy) so go out and buy one...NOW!    Go prepared - get all those "it costs HOW MUCH for THAT THING?!?" thoughts outta yer mind, cuz their fences are well worth the money.

I'm intrigued, as I've never heard of a 10" circ saw.  Is this an old thing, and where did you pick it up?  That's gotta weigh a TON!  

Good luck, you'll do just fine with your circ saw, patience, and your "saw guides".

[roybfr]

I have a Delta ShopMaster TS300, IIRC was about $350, so it was not the cheapy cheapy, but still not the "pro" model. I just looked up the Biesemeyer, man I have been looking for something like that for ever, thing will cost as much as the saw, but I could really use it on some other stuff that I do. I will try the angle iron, have some pretty long pieces down at work so I will have to get a few lengths of it home. I was using some extra wood as guides for some short cuts but I don't have any pieces long enough to do the cab back.

Not sure what I was thinking about the circ saw, it is just a regular 7 1/4in one, nothing special. The 6" is cordless so I have been using it more, plus the blade is a little better.

Thanks

[Apollo]

Much easier way is to tack a straight pioece of timber to your MDF and use it as a guide for your circular saw.

[DrewKaree]

Delta ShopMaster TS300, IIRC was about $350, so it was not the cheapy cheapy, but still not the "pro" model.

The other thing I'd check is if the bolts on the trunnions (the things the saw motor bolts to for adjustments) and tighten 'em up if they're loose.  

I just looked up the Biesemeyer, man I have been looking for something like that for ever, thing will cost as much as the saw, but I could really use it on some other stuff that I do.

They DO make copies, but they all are pretty expensive, but once you have one on your machine, you'll wonder how you ever got along without it.  Check Rockler to see how much their version is, it should be a bit cheaper.

I was using some extra wood as guides for some short cuts but I don't have any pieces long enough to do the cab back.

only problem I always seem to have is that the wood isn't straight in one or more directions.

[akira]

another good tip is make sure you cut OUTSIDE your markings to allow for any discrpances and use a hand plane or sander to correct. Remember to allow for the thickness of your saw blade too

[Xiaou2]

 Funny this thread pops up now... as Im in the process of building an extention table for my cheapie table saw.

 The thing has a measurment guide for less than 2ft : (    The extention will add 6 ft to that... so almost 8ft of measurable and guide lockable accuracy : )    I just hope my saw dosnt go bad soon,  as this is super custom to fitting the special lockdown bar.

 Ill post pics when its completed.

 Although maybe not a good idea... (Im very carefull tho - and havnt had any probs...)  Ive removed my rip fence.  I hated not being able to see under it... as well as having issues with how it moved arrround sometimes.  

 A lot of problems with cuts are due to not being able to feed the work in perfectly straight - as you have to make sure its at the guide  edge perfectly at all times... as well as making sure the work is flat to the table... and also making sure to feed it steadily so that it dosnt fly out at you or worse - gobble your body parts up.   So much to concentrate on... that you lose focus on the pressure you should be putting on the  edge as you feed it.

  However... it is possible that your motor shaft or blade is bent : (   Remove the gaurd, lower the blade to under table level,  and power up - watching if the blade wobbles or not.  You may be able to see better by hand spinning the blade.

 The blade may be seated improperly as well.  Undo it, then pop it back on again making sure its tightened and resting properly.

[akira]

 

you could also use a normal power saw and using g-clamps attach a rail or guide to the material you are cutting to ensure a nice straightline  

[ras2a]

Much easier way is to tack a straight pioece of timber to your MDF and use it as a guide for your circular saw.

couldn't agree more!  We have a table saw at work but Im certain it's 'out' slightly.  As has been said..simply use a circular saw (can pick these up dirt cheap) and clamp a length of wood the correct distance from your cutting line for your saw to guide against...it takes seconds to make cuts this way!

[MonitorGuru]

The most common cause of wavy rip cuts on a table saw are due to a cheap blade.

Particle board is the absolute worst, MDF is better to cut, but both can cause problems if you use cheap blades.

And cheap meaning wrong type not necessarily inexpensive.

As much as it is nice to have a nice edge, do NOT use a large count alternating angle kerf finishing blade such as a 60 to 186 count blade.  These blades heat up VERY fast and bend VERY easily, and the alternate angle that each tooth bends out are QUICKLY flattened by the material (especially with particle board)

ONLY use low count (18, 24) carbide tipped blades with heat expansion channels to cut this type of material.

Also run the board through twice.. once at about 1/4" depth, again at full (1"+ depth).  This serves two purposes. The first is that it will create a clean groove without breaking out the edges, even on a low tooth count blade.  Second it will remove 1/3 of the material to help the second cut go easier.

Yes, it's a bit more work, but you will be happier with the results.

I've built many a storage cabinet out of melamine coated particle board, and couldn't figure out why I kept getting wavy cuts (from a handheld circular saw besides) and the table saw did the same thing.   I had much better luck with cutting oak laminated MDF for bookcases the year before.  Anyway, my cuts got much straighter when I switched to a carbide tipped low count blade and made 2 passes through the wood.  Afterwards I looked at the 186 tooth count blade and the kerf got flattened from 1/8" to about 1/16"  as it bent all the teeth inward to almost flat with the thickness of the blade itself!

[Tailgunner]

I typically use a 8' level for a straightedge when ripping full sheets of material.

[rdagger]

Much easier way is to tack a straight pioece of timber to your MDF and use it as a guide for your circular saw.

This is an easy wasy.  MDF works well for the straight piece as it is hard to get anything straight at Home Depot.  I used a small handheld jigsaw for the majority of my cuts and ripping.