MFT + track saw bevel cut problem

[anwalt]

Hello,

Would massively appreciate help with this issue: I'm trying to cut oak at a 45-degree bevel, using a Mafell track saw on my MFT -- see picture here:

?dl=0 (Sorry about the dropbox links, attachments are not working right now.)

It needs to be precise because I want to mitre join two pieces together for a frame.

My problem: Every time the cut ends up square on the "top" side of the workpiece (where the blade enters next to the track), but on the bottom side (sitting on the table top) the cut veers off towards the end of the cut. See pictures here:

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With the exact SAME setup, a 90-degree/non-bevelled cut comes out perfectly square on all sides.

Obviously there is some technique involved here because the saw wants to fall over in the 45 position and I have to hold it down with my left hand while cutting. However I've tried doing this with more pressure, less pressure, I always get the same (bad) result. Have also tried on a piece of softwood, same issue.

What am I doing wrong??

Many thanks in advance, everybody!

 

[woodferret]

Put stock of the same thickness before and aft of the piece (ideally).  At least do so at the closer end if you're using the fence.  If not using the fence, then try and support both ends of the rail so that it doesn't bow/tip.

 

[Michael Kellough]

What woodferret said.

Add stock to both ends of the cut, such that the blade is fully engaged with wood before and after the keeper stock.
You want nothing to change with the saw or how you handle it during the keeper cut.

 

[anwalt]

Thanks both! I'll try that tomorrow morning! Also noticed that the guide rail may not have been 100% level, i.e. fractionally higher at the near side of the table, which could presumably cause some of this.

Trying to work out if this is the time to buy a mitre saw Most things are possible with the MFT setup but some just take a lot longer to get right...

 

[Packard]

You don’t have a chop saw? A table saw? 

A track saw would be a distant 2nd choice for either of them.

Or cut the miter on 8” wide stock and rip to the narrow widths. 

 

[Michael Kellough]

I assumed it was a long cut, hence the guide rail.

I agree with Packard, you should have a miter saw.

 

[Svar]

I agree with the previous comments about supporting the track to keep it from sagging.
However, I'm curious what happens is you do another pass over the same skewed bevel? Will cleanup cut fix it? Need to make sure it's not blade misalignment that causes deflection.

 

[anwalt]

Thanks -- yes it would be good to get a chop saw for this. I chucked out a cheap, broken one last year and wanted to buy a Kapex but haven't brought myself to spend the money yet. I feel like I should be able to get there with the track saw but it's weird having to find workarounds for something so simple.

Svar: interestingly, I tried a cleanup cut and it didn't fix the problem. I did a straight plunge without the bevel to check blade alignment and it seems OK, but don't know if that's enough. I do need to check carefully that the rail is properly level and supported, will report back...

 

[waho6o9]

You're not that far off. Maybe a shooting board can tidy things up a bit. 
All the Best
View attachment 1
From David Barrons blog ^

 

[Michael Kellough]

Thanks -- yes it would be good to get a chop saw for this. I chucked out a cheap, broken one last year and wanted to buy a Kapex but haven't brought myself to spend the money yet. I feel like I should be able to get there with the track saw but it's weird having to find workarounds for something so simple.

Svar: interestingly, I tried a cleanup cut and it didn't fix the problem. I did a straight plunge without the bevel to check blade alignment and it seems OK, but don't know if that's enough. I do need to check carefully that the rail is properly level and supported, will report back...

I often get a little bit of deviation at the end of the run (a lot of stuff happens/changes at the end of the run) on the MFT but it seldom matters. In your case, cross-cutting narrow stock, just place put some sacrificial stock against the fence and run the saw to the end of the rail so the deviation only occurs in the sacrificial stock. If you want he best results add some sacrificial stock before the good stuff too.