router plunging repeatability

[John Piwaron]

I hope this is a simple question - is there any plunge router currently for sale that's capable of plunging down in exactly the same location every time?

I ask this because I've noticed that this is not so with the two I currently have. Each time it's slightly different. You know, plunge to a depth, cut, raise, adjust stop rod to go for a deeper cut, plunge. but the next plunge (or any after) isn't exactly the same. I understand this difference is the result of any play between the rods and the guide holes, but even so, I'd like it to be better if possible.

[pat warner]

There are many variables that determine just where a cutter cuts whence plunging, besides the slop and precision of the plunge rods and bearings.
So I would not necessarily condemn the router at this stage.
Some of the best at straight down plunging: Festool and DW 621's and 625's.

[John Piwaron]

Isn't the mechanism on the DW621 the same as the plunge base that Porter Cable puts in that kit with an 890 series router? If so, wouldn't that be the same?

Yes, I understand that other factors influence the straight up 'n down performance. Bit length, diameter (flex) type. But plunge rods and bearings are #1

[pat warner]

I don't know what parts are interchangeable.
But bottomline: You don't want to get into in the detail of why your router may not hit straight down the head.
For example, are you cutting under power? How much of a plunge? Condition of the cutter, Material properties, deflection etc.
If you indicate off of a precision ground dowel in the collet, say every .250" or so, you'll probably find that it tracks to better that .001"
The dynamics of the cutter and cutting can fool you into thinking the plunge slop and mechanisms are the problem.

As a rule, single cutter width cuttings are as insulting as they come. If you can use a smaller cutter and create your fixturing so the cutter can swim a little you'll get better results.
That will take the stress off the cutter and as you shave the walls of the excavation there will be very little, if any, stepping.
Skinny cutters, aggressive depth changes and handling? Then all bets are off.

[Rick Fisher]

I used my OF 1400 to cut the 3/4" Dog holes in my bench .. I would say it plunges to the exact same place every plunge .. Probably off by a millionth or something but I cant tell ..

[Jamie Buxton]

I hope this is a simple question - is there any plunge router currently for sale that's capable of plunging down in exactly the same location every time?

I ask this because I've noticed that this is not so with the two I currently have. Each time it's slightly different. You know, plunge to a depth, cut, raise, adjust stop rod to go for a deeper cut, plunge. but the next plunge (or any after) isn't exactly the same. I understand this difference is the result of any play between the rods and the guide holes, but even so, I'd like it to be better if possible.

When you say "exactly", what do you mean? .001"? .01"? How far off is your present solution? What would you like instead?

[Phil Thien]

My Dewalt DW618PK plunge base is very accurate, my DW621 was accurate, too. The little DW611PK plunge base may have a bit more play in it than either of its bigger siblings, but is still outstanding.

On the other hand, I had one of those little Trend 1-HP or whatever plungers, and the plunge was a joke. It was all over the place.

[John Piwaron]

How big? Not much. But I can see them. I'd prefer that everything look as good from the inside as the outside. :) I'm going to try Pat's advise - work on technique before blowing money trying different equipment. And it's cheaper :) :)

[John Piwaron]

One other thing, FWIW, the plunger I'm using is a PC 7539. Though I do have that kit for my 890 series router to plunge too. I don't use that one very often. The 7539 seems to have enough muscle to rout granite. . . .

[glenn bradley]

Kind of echoing others here:
- What is "exactly"? Material reaction will be greater than my opinion of "exactly" in many of the woods I work with.
- Are these stationary plunges like shelf pin holes or are they runs? Again, material, effort and cutter condition can cause reasonable variations under stress.
- Have you assured your stop/turret is seating well? Several brands (yellow, blue and green) have gone down the highway as their mechanisms require more 'after-market' fettling than I enjoyed in order to get their turrets and rods reliably usable.

[John Piwaron]

A deep mortise requiring more than one pass. No way am I going to go deep in one pass. OTOH, maybe that's a flawed idea someone will enlighten me on. I'm o.k. with that, I don't know everything. In this case, the cutter is a 1/2" dia HSS end mill.

As I said, the router is a Porter Cable 7539 - a brute that I've owned for very many years. I don't see anything obviously wrong with any part of it.

One other thing - I'm a hobby guy, not a pro. But I don't see any reason why I shouldn't make everything the best it can be inside and out.

Do these "steps" really matter? Maybe not. Probably not. But if there's a problem, I'll fix it. Technique, whatever.