Micro-Adjusting Dovetail Router Bit Depth

[bgm1911]

I'm using the OF-1400, but I'm sure this applies to any plunge router:

How is it possible to make micro adjustments to depth of cut with a dovetail bit?

In order to keep the router from springing back up and damaging the bit against the bushing, the large knob must always be locked, and this prevents any micro adjust to the cut height.

Am I forced to make a test cut on a board, and then measure that cut depth to see if it matches the board thickness?

 

[Mario Turcot]

If I understand, to affix the bit you need to plunge the router and than you cannot release the plunge mechanism otherwise the but cutters will hit the guide bushing?

I never cut dove tail before but it looks to me that the bushing is not the right one. Are you using 1/2" dovetail bit?

 

[RDMuller]

I do not use plunge routers for dovetailing jigs.  I got sick and tired of having those brass guide bushings getting torn up by the dovetail bit if the plunge springs  get in control of things and all of the time killed trying to dial them in.  This is a very "micro" precise adjustment.

I found that many standard base routers aren't so great either if their lift mechanism has any slop in it -- my Bosch's at the time were awful.  I did my homework and  purchased a 1 3/4 horsepower Dewalt standard base that has the "ring around the motor mechanism" to gently lift or lower that motor in micro adjustments.  I have dedicated that router to dovetail only use so I just put it away for extended periods after I got the thing dialed.  Very economical move when you consider all of the time it takes to really get it done precisely and the materials that can be ruined.

I have never tried my 1400 for this use and will not. 

I just did  a search in Google - OF1400 fine depth adjustment.  Low and behold the first thing that came up was a YouTube I had done a few years back which talks about the 1400's and it's turret.  I really didn't have much to refer to so hopefully I didn't say anything wrong on the video and hopefully covered what I should have.  A couple other videos showed up from Festool and from Greg Paolini who pitches in as a trainer at Festool.  He may have some things there that are better said than what I did!  I would not be surprised. 

For the life of me I can't figure out why issues are not addressed in Festool documentation.

Muller Video

Festool Video

Paolini Video

 

[bgm1911]

I do not use plunge routers for dovetailing jigs.  I got sick and tired of having those brass guide bushings getting torn up by the dovetail bit if the plunge springs  get in control of things and all of the time killed trying to dial them in.  This is a very "micro" precise adjustment.

I've watched those videos, but they don't address what I'm trying to do, but your comment echoes what I've seen.  It's impossible to use the fine adjustment when the large knob is locked tight, and it must be when using a dovetail bit and bushing.

 

[Roseland]

I'm fortunate to have a choice of several routers.  For dovetails I use a small Bosch router where I've moved the spring so that when the locking knob is released the head springs down, not up.  That way I can use the fine depth adjuster directly without any risk of the cutter ripping up the guide bush.

Andrew

 

[Corwin]

I've watched those videos, but they don't address what I'm trying to do, but your comment echoes what I've seen.  It's impossible to use the fine adjustment when the large knob is locked tight, and it must be when using a dovetail bit and bushing.

Yes, the large black knob must be released before you are able to adjust the plunge depth. But, maybe if you apply enough downward force to prevent the router from springing back up while you loosen the large black knob just enough to allow for movement, you might be able to make the adjustment that you need.  Assuming that you have your router plunged and the depth stop is engaged with the turret stop, here’s what you’ll need to do:

If your bit is too deep and you want a shallower plunge, you will first have to loosen the big black knob slightly while pushing down on the router so it doesn’t spring back up. Then allow the router to move up slightly and retighten the knob. You can now turn the green dial (to a lower number) as needed. Finally you again loosen the large black knob while preventing the router from springing back up, and proceed to plunge down to the stop and retighten the big black knob.

If your bit is too shallow and you want a deeper plunge, you first turn the green dial (to a higher number) as needed. Then, while applying downward pressure on the router to prevent it from springing back up, loosen the black knob slightly and plunge down to the new full depth and retighten the big black knob.

 

[android]

I've been making a lot of dovetails with my Porter Cable jig lately for my kitchen project.

I think I would go crazy if I tried to use a plunge router for this.

I have a Dewalt that I use with standard base and I use an iGaging height gauge to get the bit depth set just right.

I flip it over and use the large ring to get the height exactly where I want it. The gauge sits on the base plate.
All adjusters have some slop in them because they're threaded. You want to adjust against the working side of the threads, so that means light pressure on the router base plate.

https://www.amazon.com/iGaging-Digital-Electronic-Height-Magnetic/dp/B0026MTCG8

 

[eeeesh]

I have the Bosch MRC23EVSK router which has an 'after lock' adjustment.  So once your initial plunge depth is setup and locked in, you can make further 'micro' type adjustments by simple turning a knob
https://www.boschtools.com/us/en/boschtools-ocs/combo-pack-routers-mrc23evsk-34685-p/

[attachimg=1]

 

[bulubuluplopplop]

I had the same problem (but with another router).
I used a simple trick: after plunging the router, I attached a small string between the base and router (the string beeing quite loose). So If I unlock the router, it will go up of around 1mm (retained then by the spring), and I could fine adjust the knob, then plunge again.

 

[nclemmons]

Here's one method you can use...

For raising the bit a small increment, use a feeler gauge to set the amount you want to raise the bit.  Release the router plunge knob and insert the feeler gauge between the turret and the drop-down pin.  Release the depth control knob being careful not to let the router spring up and insert the feeler gauge to raise the bit a controlled amount and press down tightly on the router.  Tighten the depth lock knob.  That will give you controlled depth up.

For lowering the bit a small amount, Start with the pin against the turret and loosen the drop down pin control knob.  Insert the feeler gauge and tighten the drop down pin release knob with it tight against the turret.  Then remove the feeler gauge and loosen the router knob to lower the bit a controlled amount

This is the one way I have found for 'controlled' depth changes with a dovetail bit on a plunge router.  Definitely not as easy as a fixed base router, but it does give you micro adjustment with a controlled change in depth.

Here's an inexpensive feeler gauge if you don't have one - https://www.amazon.com/Hotop-Blades-Feeler-Imperial-Measuring/dp/B06XHXJG31/ref=sr_1_4?ie=UTF8&qid=1518048640&sr=8-4&keywords=feeler+gauge

 

[fshanno]

I've used my 1400 on my Leigh Super 18 a lot.  I have to be careful and it's a bit of a pain but it's not too bad.  One rule of thumb is that I only unlock the plunge with my router upside down and one hand on the base applying enough pressure so the collar on the guide bush won't hit the bit.

You're probably already doing what I do but anyway here's what I do.

I set it up initially a little shallower than I need.  Then zero the stop to the turret post.  Then I check to see where I am relative to the line I've drawn on the board.  Raise the stop a little bit using the mirco adjust.  Then, making sure I have plenty of pressure on the base, I unlock the plunge and it pushes down till the stop hits the post on the turret.  Then check and do it again.  So I'm always pushing down.  I never have to let the base rise, I'm always adjusting lower.  And I won't go too low because the micro adjust really is micro.  I hit the mark with two or three tries.

You see the thing is, it's easy to get the bit lower.  You can use the micro adjust while the plunge is locked.  But you can't use the micro adjust to raise the bit with the plunge locked.  The stop is against the turret post and the micro adjust won't turn.

Hope that makes sense.  It works fine for me.

 

[bgm1911]

Yes, the large black knob must be released before you are able to adjust the plunge depth. But, maybe if you apply enough downward force to prevent the router from springing back up while you loosen the large black knob just enough to allow for movement, you might be able to make the adjustment that you need.  Assuming that you have your router plunged and the depth stop is engaged with the turret stop, here’s what you’ll need to do:

This works, but it is far from what I would call "user friendly".

LOL, my $50 (non-plunge) router works better than the Festool, in this regard.

 

[Corwin]

Yes, the large black knob must be released before you are able to adjust the plunge depth. But, maybe if you apply enough downward force to prevent the router from springing back up while you loosen the large black knob just enough to allow for movement, you might be able to make the adjustment that you need.  Assuming that you have your router plunged and the depth stop is engaged with the turret stop, here’s what you’ll need to do:

This works, but it is far from what I would call "user friendly".

LOL, my $50 (non-plunge) router works better than the Festool, in this regard.

Lots of people have multiple routers, and leave a dovetail bit in one of their fixed-base routers just for this particular task. So, your $50 non-plunge router can now become a "one trick pony."  [big grin]