Another quick question

[PartTimeHack]

As I mentioned, I am relatively new to woodworking so I plan on asking a lot of questions.

I find that I (or the saw) am struggling to rip 3/4" mdf on a 45 degree bevel without burning it.

Is this normally from the scrap not being able to pull away and getting somewhat wedged beneath the blade or do I just need a sharper blade?

Thanks.

[Bill in Buena Park]

A dull (or dirty) blade could cause this, or other factors to check including alignment of your rip fence to the blade, type of wood and feed rate.

[JSUPreston]

I can think of several things that may be coming into play.

1. How sharp is the blade? Carbide teeth or plain steel?
2. What table saw are you using? Horsepower rating of the motor? 120 or 240V?
3. Is the fence absolutely parallel to the blade? Some prefer the back of the fence to be about 1/64th off of parallel to help keep offcuts from getting trapped.
4. How far above the material do you have the blade?
5. Is the blade a regular or thin kerf blade?

Just some quick things that may help us narrow down the problem.

[PartTimeHack]

1) It is a carbide blade, but old. Probably the original stock blade.
2) BT3000
3) I'll have to check for parallel. I thought it was pretty good.
4) The blade is only slightly (1/16th or so) maybe above the blade
5) I don't remember.

Thanks.

[Black wallnut]

If you set your fence slightly away at the back of the blade and then move the fence so that the offcut falls away, IOW to the right of the blade so the blade tilts away from the fence then you will be somewhat pinching the back of your cut however this may just raise the workpiece. For bevel cuts the fence should be exactly parallel with the blade. A clean blade of the proper tooth count also helps. IIRC MDF is hard on blades.

[phrog]

Are you using a rip blade?

If so, is it sharp?

With a sharp rip blade you should be able to feed the wood at a fairly good rate without burning. The bottom of the gullets, I've been told, should barely be visible coming out of the top of the wood being cut. That is the proper height adjustment of the blade. (That allows the dust to be disposed without being trapped between the teeth and causing heat build-up.)

What Mark said about MDF being hard on blades.

EDIT: A rip blade normally has about 24 or so teeth on a 10" blade.

[PartTimeHack]

The blade is carbide-tipped, 36T.

I just bought an Oldham 60T, carbide finishing blade online at HD. Maybe it will have better results. I need to go back and check alignment anyway.

The best thing I ever did for my DeWalt miter saw is outfit it with a Freud Diablo blade. That sucker cuts great.

[sailor55330]

I wouldn't use a 60t blade for ripping. As mentioned earlier, usually less TPI (teeth per inch) is better for ripping. The 60T is more for fine cuts--such as cross cuts. Tryingt to rip with it is going to stress the saw more and possibly frustrate you more as well. Plus, as mentioned, MDF is a blade killer. If you are having the scrap edge get caught under the blade, something doesn't sound right. Maybe the riving knife is out of adjustment? It's been a long time since I've used a BTxxx, so I can't remember if the riving knife even tilts or if you have to remove it. I'd be nervous about kick-back based on what you are describing.

Good Luck.

[atgcpaul]

I find I can get burn marks if I slow down/stop to reposition my hands when I'm pushing the stock through for a rip cut. Keeping a consistent feed rate can help eliminate that.

[PartTimeHack]

I removed the splitter from the anti-kickback hood, leaving just the splitter installed. It does move with the blade tilt.

(In hindsight, I should have gone with the SharkGuard.)

The reason I got the finishing blade was due to some reviews. Perhaps those reviews were by DIY'ers like myself, and not real woodworkers. ;(


UPDATE:

I tried ripping a half dozen pieces of 3/4" MDF with the blade at zero tilt, and it cuts just fine. Not quite like butter, but not too far away. I'm guessing that neither the blade nor the parallel alignment is at fault.

Do you think the difference is just that the fence is on the alternate side of the blade that I'm used to (I'm right handed) and that either clumsiness or fear is the main problem?

[Black wallnut]

FWIW my saw nearly always has a 60 or 80 tooth finish blade installed. I only change out for a rip blade when I am going to be ripping more than one 8' board. For MDF a high tooth count finish blade is the one to use.

[PartTimeHack]

Ok, I just tried it again without a hold-down on top or the side and just used my hands. I also raised the blade such that the top gullet was above the workpiece.

Interestingly, although there were a few minor burn marks due to switching position or stopping to use the push stick, it was a lot better this time around.

The saw still appears to have more trouble (probably due to a deeper relative cut) than when it was at zero degrees, but all in all it wasn't bad.

Thanks for the advice.

[LCHIEN]

I wouldn't use a 60t blade for ripping. As mentioned earlier, usually less TPI (teeth per inch) is better for ripping. The 60T is more for fine cuts--such as cross cuts. Tryingt to rip with it is going to stress the saw more and possibly frustrate you more as well. Plus, as mentioned, MDF is a blade killer. If you are having the scrap edge get caught under the blade, something doesn't sound right. Maybe the riving knife is out of adjustment? It's been a long time since I've used a BTxxx, so I can't remember if the riving knife even tilts or if you have to remove it. I'd be nervous about kick-back based on what you are describing.

Good Luck.

When cutting MDF which is grainless, there's no such thing as ripping or crosscutting.

while you may consider cutting the short distance using the miter sled as crosscutting and the long distance using the rip fence as ripping, it really has nothing to do with the blade configuration.

Probably a 40 tooth blade or thereabouts is optimal, 36 is good.
A sharp blade makes a huge difference. If the saw is an old BT3 variant the 36T blade was the original and probbaly quite old as well.

Have a quarter or half inch or more of the blade above the workpiece.

For cutting on a table saw the ideal woulld be to feed quickly as the wood burns if feed slowly.

However, the feed rate must be within the ability of the saw to cut and that involves:
removal of material (tooth count matters, large gullet low tooth counts)
sharpness - dull blade won't feed quickly
Thickness - thicker wood you have to feed slower as its harder to cut remove twice the material. A 45 degree bevel cut makes the wood appear 40% thicker.
power a more powerful saw will be able to feed as quick as you want, the BT3 should easily be able to cut 3/4 MDF quickly with its power.
If the saw power is low, or the wood thick, or both, then the saw will audibly labor and slwo down and then it won't cut right either and burn.
Have to have good electricity feed - 14 Ga extension cords or noe, 15-20A outlets. or the motor will starve for power.

Usually the cuplrits for burning are too slow a feed, can't go faster because dull blade, wood too thick, power too low and motor laboring from same.

[LCHIEN]

As I mentioned, I am relatively new to woodworking so I plan on asking a lot of questions.

I find that I (or the saw) am struggling to rip 3/4" mdf on a 45 degree bevel without burning it.

Is this normally from the scrap not being able to pull away and getting somewhat wedged beneath the blade or do I just need a sharper blade?

Thanks.

Hey I hope these aren't MDF cleats you were talking about in the other post.

MDF has no strength for this kind of thing, It will break or crumble under load!

Don't make MDF cleats, please!

[Knottscott]

At the very least clean your blade. It's probably well past time to have it sharpened too. Or you could replace it with something like a Freud Diablo or Irwin Marples 40T or 50T general purpose combo blade....that start at @ $30....it's always nice to have a spare.

FWIW, MDF is abrasive and is rough on blades....if you'll be cutting a lot of MDF, it might be worth picking up a blade with a triple chip grind (TCG), which tend to have better edge life than other grinds.

Tips for Picking Saw Blades

Bargain Saw Blades