Cutting down for flush trimming?

[sawdust-samurai]

I'm about to glue a second 3/4 MDF sheet to a sheet that I have already cut down to my desired tabletop size.  I am going to need to flush trim this second piece to the first with my new MFK 700.  My question is, does it matter how much excess material overhangs the sheet I've already sized?  I've flush cut things in the past, but I never gave it any thought as to if the amount of overhang effects dust collection (never had it before) or how clean the cut is?

 

[bobtskutter]

I assume you're using an OF1400 with the clip in dust shroud and a bearing guided bit?

If you set up the router with the bit and dust shroud, then put the bearing against a board edge you will notice the dust shroud can rotate a little bit.

If I have a 19mm bit I can get about 5mm "clearance" to get a flush cut using the dust shroud (I think it's about 5mm, set up the router and offer it up to a straight edge, you'll see what I mean).

I do find if I have a large amount to flush trim away the dust shroud gets caught at the corners.  May give yourself 2 to 3mm of material to trim away.  Might be a good time to get the jigsaw out.

Bob

 

[jeffinsgf]

More important than the issue of dust collection is bit engagement. Try to keep it in the 25% range if you can. That would mean 1/8" trim with a 1/2" bit. That will maximize tool life, minimize motor work and optimize dust collection all at once.

 

[Vondawg]

If I read it right and you’re using the mfk700 (trim router)  and it’s all you have I wouldn’t leave much over hanging

 

[bobtskutter]

If I read it right and you’re using the mfk700 (trim router)  and it’s all you have I wouldn’t leave much over hanging

Ooopps!  I should read the post properly before I launch into a keyboard outburst

Bob

 

[Hawkeye0001]

I'm about to glue a second 3/4 MDF sheet to a sheet that I have already cut down to my desired tabletop size.  I am going to need to flush trim this second piece to the first with my new MFK 700.  My question is, does it matter how much excess material overhangs the sheet I've already sized?  I've flush cut things in the past, but I never gave it any thought as to if the amount of overhang effects dust collection (never had it before) or how clean the cut is?

Try to take as much off as possible with e.g. a jigsaw and only do the last few millimeters of overhang, then you'll be good even with the MFK. Just make sure that the overhang is less than half the cutter diameter.

If you fully engage into a material (e.g. when cutting dados) the rule of thumb is not to plunge deeper than half the diameter, which you'll bust easily with 3/4" MDF if it fully surrounds your flush trim bit.

 

[sawdust-samurai]

More important than the issue of dust collection is bit engagement. Try to keep it in the 25% range if you can. That would mean 1/8" trim with a 1/2" bit. That will maximize tool life, minimize motor work and optimize dust collection all at once.

I want to make sure I'm understanding you here.  I will be trimming 3/4" of MDF away, my bit has a 1" cutting length.  In this scenario, you are saying that I should set my router so that I'm only removing 1/4" of the MDF thickness per pass?  How can I do that if the bearing is on the bottom of the bit?  Or do I have to get a bit with the bearing on the top?

If I read it right and you’re using the mfk700 (trim router)  and it’s all you have I wouldn’t leave much over hanging

I do have a hulking Craftsman router from like the 80s that my father-in-law gave me, but I hate using that thing!  Everything about it sucks.  lol

If I read it right and you’re using the mfk700 (trim router)  and it’s all you have I wouldn’t leave much over hanging

Ooopps!  I should read the post properly before I launch into a keyboard outburst

Bob

No worries Bob, your reply was still helpful for general knowledge... which I still need plenty of!

 

[sawdust-samurai]

I'm about to glue a second 3/4 MDF sheet to a sheet that I have already cut down to my desired tabletop size.  I am going to need to flush trim this second piece to the first with my new MFK 700.  My question is, does it matter how much excess material overhangs the sheet I've already sized?  I've flush cut things in the past, but I never gave it any thought as to if the amount of overhang effects dust collection (never had it before) or how clean the cut is?

Try to take as much off as possible with e.g. a jigsaw and only do the last few millimeters of overhang, then you'll be good even with the MFK. Just make sure that the overhang is less than half the cutter diameter.

If you fully engage into a material (e.g. when cutting dados) the rule of thumb is not to plunge deeper than half the diameter, which you'll bust easily with 3/4" MDF if it fully surrounds your flush trim bit.

Thanks Hawkeye.  I believe that clears up what Jeff was trying to tell me earlier in this thread.

 

[sawdust-samurai]

So, with my 1/2" diameter bit, I should try to leave no more than 1/8" to 1/4" of overhang to be removed.  Correct?

 

[Crazyraceguy]

To simplify the whole ordeal, don't worry too much about the overhang. Glue your parts together and use that Makita track saw to cut it closer. As [member=7266]jeffinsgf[/member] said, you really don't want to take off very much with the router. I would aim for less than half the diameter of your bit. It puts far less strain on the bit and the motor, along with turning far less MDF into dust. If you do this with any regularity, I would look into an 8mm shank cutter.

That is not to say that you can't take more, but that is better left to 1/2" shank cutters and way more powerful routers.

 

[Cheese]

I like to keep the amount of overhang down to .060" to .125" (1/16" to 1/8"). More than that and there'll be a tendency to burn the material along with it being harder on the router bit and it will turn the job into a lot slower trimming process which takes the fun away.

Using Jeff's rule of thumb (which is a good one), if you're using an 8 mm straight shank bit, the material overhang should be 2 mm (.080")  and if you're using a 1/4" diameter straight shank bit, the material overhang should be 1/16" (.060"). 

The .125" material overhang works for me because I usually use a 1/2" diameter cutter with a bottom bearing.

 

[sawdust-samurai]

I will be using the Freud 42-104 bit for this. It has a 1/2" diameter with bottom bearing, 1" carbide height and a 1/4" shank. 

To simplify the whole ordeal, don't worry too much about the overhang. Glue your parts together and use that Makita track saw to cut it closer. As [member=7266]jeffinsgf[/member] said, you really don't want to take off very much with the router. I would aim for less than half the diameter of your bit. It puts far less strain on the bit and the motor, along with turning far less MDF into dust. If you do this with any regularity, I would look into an 8mm shank cutter.

That is not to say that you can't take more, but that is better left to 1/2" shank cutters and way more powerful routers.

I was planning on using the track saw to trim this one down to fit that non-square top I made before trimming it flush  [tongue] .  I'll shoot for making this one 1/8" larger than that one.  I'll probably do this on 5 or so other benches, but after that I don't foresee doing it that often.  Maybe I'll keep an eye on the Recon site to see if a 1400 pops up or hold out until Black Friday... do Festool products go on sale for Black Friday?

 

[jeffinsgf]

More important than the issue of dust collection is bit engagement. Try to keep it in the 25% range if you can. That would mean 1/8" trim with a 1/2" bit. That will maximize tool life, minimize motor work and optimize dust collection all at once.

I want to make sure I'm understanding you here.  I will be trimming 3/4" of MDF away, my bit has a 1" cutting length.  In this scenario, you are saying that I should set my router so that I'm only removing 1/4" of the MDF thickness per pass?  How can I do that if the bearing is on the bottom of the bit?  Or do I have to get a bit with the bearing on the top?

Seems like others have explained, but I'll reply anyway. I'm not talking about depth of cut down from the base of the router. You're right, if your flushing with a bearing, you have to take the full depth at once.

I'm talking about the amount of overhang your new piece has over your already sized piece. Keep that to a minimum as best you can. Keeping it to 1/16" on all 4 sides would be ideal, however, that can be tricky.

 

[sawdust-samurai]

More important than the issue of dust collection is bit engagement. Try to keep it in the 25% range if you can. That would mean 1/8" trim with a 1/2" bit. That will maximize tool life, minimize motor work and optimize dust collection all at once.

I want to make sure I'm understanding you here.  I will be trimming 3/4" of MDF away, my bit has a 1" cutting length.  In this scenario, you are saying that I should set my router so that I'm only removing 1/4" of the MDF thickness per pass?  How can I do that if the bearing is on the bottom of the bit?  Or do I have to get a bit with the bearing on the top?

Seems like others have explained, but I'll reply anyway. I'm not talking about depth of cut down from the base of the router. You're right, if your flushing with a bearing, you have to take the full depth at once.

I'm talking about the amount of overhang your new piece has over your already sized piece. Keep that to a minimum as best you can. Keeping it to 1/16" on all 4 sides would be ideal, however, that can be tricky.

Thanks for the further clarification Jeff.  All of you have been great with helping out on this and other questions I've had.

 

[Michael Kellough]

Following on from CRG, you don’t even need a router.

Just laminate the sheets and when the glue is dry cut it with the tracksaw.

Use geometry to make it a square rectangle this time.
Sure it’ll be a little smaller than the first time but you adding edge banding right?

 

[sawdust-samurai]

Following on from CRG, you don’t even need a router.

Just laminate the sheets and when the glue is dry cut it with the tracksaw.

Use geometry to make it a square rectangle this time.
Sure it’ll be a little smaller than the first time but you adding edge banding right?

That's a good thought Michael, assuming I can cut it square!  lol  I will be adding edge banding and my top is already a little oversized for my needs, so this is a viable option.  Again, assuming I can cut it square!

 

[Crazyraceguy]

With as much difficulty as has been involved so far, I wouldn't double the thickness, before getting it square.

My reference to gluing one oversized piece was "well over", like an inch, then trimming that off with the track saw after it's dry.

 

[sawdust-samurai]

With as much difficulty as has been involved so far, I wouldn't double the thickness, before getting it square.

My reference to gluing one oversized piece was "well over", like an inch, then trimming that off with the track saw after it's dry.

So are you suggesting I cut the oversized sheet down to a 1" overhang with the track saw and glue that to the already sized sheet.  Once it is dry, take the track saw and trim that 1" overhang to be flush?  No use of the router or any attempt to try and square everything up?

 

[makpacman]

Hmm. This might be a good time to practice getting a nice square cut. After all the edgebanding can be any thickness you want and trimmed off or added  onto as well.

I'm a tailgater, which is just a fancy name for a finish carpenter, and from time to time I forget my framing square and need to make a square cut on incredibly expensive materials. An 8' Dutch entryway door last week being the most recent occurrence.

Instead of driving back to the shop I found a few 2x3 pieces of drywall and using the matching line technique, checked them for squareness. Once I found one that passed the test, I used that to square my rail, and verified it's absolutely square by doing the same on the far side of the door. Came out beautiful.

It's really not that difficult once you realize the marketing for guide rail squares is, well, marketing. There are plenty of nice large square objects around that can arguably do a "better" job determining 90 degrees but they don't fit in a systainer and their marketing team is non existent.

And another thought, try to make sure you have solid material on both sides of the tracksaw blade, especially with the battery operated saws, because the ultra thin blades can deflect if you try to barely trim up a piece. This also helps dust collection.

 

[sawdust-samurai]

And another thought, try to make sure you have solid material on both sides of the tracksaw blade, especially with the battery operated saws, because the ultra thin blades can deflect if you try to barely trim up a piece. This also helps dust collection.

I always try and leave at least 1/4" of material to waste side of my track saw cuts for these reasons.