Novice needs help with cause of tear out on the underside of cut

[Julie]

I am using a TS55 on a home made MFT top.
I have a good splinter guard on my rail and I am using the green splinter guard on the saw to protect the cut off side.
The top looks great but I get some tear out on the bottom of the cut. I am cutting Baltic birch plywood.
Some of the possible causes that I can think of are:
1. wrong blade depth - sadly I have the imperial scale on my saw, so I am going one mark past the thickness of the plywood.
2. the cut line in the MFT top is wider than the blade and deeper than my depth setting. (I had some issues when I first started getting everything set up correctly.
3. blade is dirty or needs sharpening. I have had it sharpened, although it has been awhile. I did just clean it.

I really hope you experts can help me fix this issue.
Thanks in advance.

 

[twistsol1]

I have a TS-75 and have the same issue when cutting on my MFT. I think when when the blade is only a mm or two below the bottom surface of the cut the blade is basically traveling horizontally causing the tear out. The groove on my MFT is also pretty wide and deep after all these years and the top probably needs replacing as well.

When I need a super clean cut, I cut on a piece of 1" foam board with the blade set about 15mm (5/8) deeper than I need to cut through the material and I get a much cleaner cut.

Hopefully some else can provide a better solution because it irritates me every time I have to do it.

 

[PaulMarcel]

It's very likely what you are thinking: incorrect blade depth. As twistsol1 said, the blade being at the same depth as the thickness means the teeth travel horizontally. Even a good kerf in the table won't fully mitigate that. So go a little deeper. I usually use the metric thickness of the stock (my TS-75 has a metric scale), add 5mm for the rail, and add 2mm for depth.

As for the wide imperfect kerf in your table... if you now have the rail position dialed in, fill the kerf with Bondo and cut it anew. I did that long ago to mine when the kerf wasn't very good. Then I got my setup perfected and repeatable so the kerf has since been unchanged.

 

[usernumber1]

foam board on the bottom and I go 2.5-3 clicks past the material thickness. no issues

clean blade is a must. i definitely notice when it's not clean on something like melamine

 

[Alanbach]

How about the clear splinter guard strip on the rail, how does it look?  Have you changed anything such that it has created a gap between the blade and the clear strip?

 

[twistsol1]

The strip gets damaged over time. I've replaced them on my rails periodically, probably two or three times in the 14 years I've had my TS75. Most of the damage comes from me tossing the rails into my truck or onto the lawn after a cut when I'm working at the kids houses or onto the lumber pile in my shop. Fortunately they are cheap and easy to replace when necessary.

Ron Paulk had a track saw video where he would make a 1mm scoring cut on top of melamine running the saw backwards on the rail before he cut the full depth. I've tried it and it doesn't make a bit of difference if the clear splinter guard is in good shape, but does waste a lot of time.

 

[DeejayK]

Hi,
As others have said, a properly sharpened blade, correct support UNDER your workpiece (you did said tear out was below) is vital to stand any chance of a clean cut. Have you tried putting a strip of painters tape or similar along the cut line on both sides of your ply so that the saw cuts it in 2? This often further helps with tear out.

 

[Rutabagared]

If you don't want mind extra kerfs in your top, try cutting on an unspoiled area.  I usually only get tear out when cutting in my well-worn groove used for squaring cuts.

 

[Birdhunter]

I've had my 2 MFTs for a long time. Mine develop a sag after, say, 6 months. If there is a gap under the workpiece, underside tearout can happen. I really like cutting on 1" foam. I get uniformly clean cuts that way.

Oh, I just flip the MFT tops when they get really saggy.

 

[sancho57]

yer getting a lot of good advice so I hesitate to respond, but have you checked the saws Toe-in?

 

[Julie]

Thanks for all the replies.
To summarize:
Yes, I have checked the saw toe in.
I get a good edge on the top with the plastic edge on the rail and the green guard on the saw.
I do not have any problem with tear out when exiting the cut at the far side.
I think my problem is just the kerf groove in the MFT is too wide from using various dogs for the rail over the years. Now that I have a dedicated set of Quad Dogs just for the rail I might route out the kerf area and put in an insert so it will only have one perfect cut.