Router shaft extensions - safe/accurate?

[ian maybury]

I've an 'Extreme' extension for a DeWalt 625 I want to mount in a table, and it strikes me that by cantilevering the cutter out further it may bring the risk of vibration, whirl/imbalance and maybe other issues.

I guess I'm wondering what the experience has been with router shaft extensions around here? Are there issues to watch out for with them?

They are widely sold and used and I've seen nothing negative, so chances are they work pretty well. But JIC...

Thanks

ian

[pat warner]

Safe & accurate? No & no.

[Gene Howe]

I'm certainly not going to argue with Mr. Warner.
I can only provide my experience with an extension and bowl bit using a pattern.
I hog out most of the wood with a Forstner, leaving an average of about 1/4" to be routed to depth.
The first few (4) passes are made without the extension.
The remaining depth (in my case, 1 1/4") is achieved in about 15 passes.
After each pass, the recess is vacuumed clean as I don't have a vac attachment on the router.
It's a slow process, not scary but, time consuming.
I'm happy with the results. Only finish sanding required.
Thanks to Mr. Warner's excellent books and articles, I have been using my routers heavily and, in ways I never envisioned possible. Consequently, my ears and hands have become attuned to each router's feel and whine. I have never experienced any vibration or odd sounds while using the extension. BTW, I use 2 Freud FT3000VCE routers. I'm sure the 13 lb weight dampens any vibration fairly well. I have not used the extension on any of the smaller routers.
The secret may be to take it slow, don't take too big of bites and relax.

[Ryan Hellmer]

Not all extensions are created equal. Read reviews on them. Accurate machining is key.

[Gene Howe]

I'm sure that's true, Ryan. Mine came from MLCS.
http://www.mlcswoodworking.com/orderstatus/html/smarthtml/pages/router_collet.html

[ian maybury]

Thanks guys. Mine is the X X version. I've had another dig around tonight, and basically it gets almost universally good reviews. Which may or may not mean a lot.

I did a fair amount of digging on the topic last year before buying, and figured much the same - but got the heebie jeebies recently as I'm about to use it.

Realistically I guess an extension has (a) by introducing another set of tolerances got to increase run-out at least a whisker, (b) by being longer got to exacerbate any throw or whirl issue, and (c) suggest care to avoid over feeding or heavy/less than top quality cutters. That much is a given. The question I suppose is to what degree these effects kick in - it wouldn't take much of an inaccuracy to to cause problems.

That said I seem to recall reading a piece last year that suggested that some routers can be scarily inaccurate in terms of the sort of cutter run out they create. Which if true maybe suggests that a very moderate increase in wobble isn't perhaps life threatening as such....

ian

[Derrell W Sloan]

I have the exact same setup, XX extension with a DW625 in my router table for several years. It is fantastic! I don't notice any additional vibration and I can easily change bits above the table so fast it is almost criminal. If you decide you don't want yours let me know, I'd love to have another one.

[Mike Wilkins]

I was in a woodworking store several years ago, intending to purchase one of those. I asked the store employee about these extensions; after he explained all the things you have to go through to get the run-out eliminated, balancing the unit, etc., I decided it was going to stay in the store. I did not feel good about introducing problems to what was otherwise a good router set-up.

[Myk Rian]

The only reason you might need an extension on a router table is because you don't use an insert.
In the case, you're better of cutting the hole and mounting the router to one.
I don't trust extensions. The slightest imbalance, bit grab, etc. can bend the shank, and you wind up with a 20,000 rpm weed whacker in front of you.

[Jim Summers]

No problems with mine. It is an "Extreme" something. To be honest I bought to use on an as needed only basis. But it works well and actually stays in until the situation won't allow it's use. Which is only with one of my 1/2" straight bits that is really long.

[jonathan eagle]

Mine works great. Highly recommended. It's best to listen to the folks that actually have used one.

[glenn bradley]

Mine is similar to the MLCS; pretty crude. The eXtreme extension is certainly a more refined unit. I only use mine for running a bowl bit in a hand held plunge router. I take extremely small depth increases as I work to my final dimension. I would not feel safe using it as a "regular" way of operating my router. If the machine were designed for that much extension, they would have given it to you IMHO.

[Sam Babbage]

I've always avoided them because they place a greater lateral load on the router's spindle than it is designed for (leverage). That said I have no personal experience and I'm curious as to how they (and their attached routers) stand up to heavy, and I mean commercial or serious hobby, use.

[Lee Passmoor]

I have the same set up too, an XX in a table mounted DW625 and it is excellent. No set up needed, just plug and play and it works like a charm!

[Gene Howe]

Sam, I just finished 8 large chip and dip dishes in Oak and Walnut and had no problems. Router didn't whimper and still works fine.
I know the centrifugal forces are not quite the same, but a large, heavy panel raising bit puts a heckuva load on a router with seemingly no ill effects.
Small bites and numerous depth adjustments to reach final depth, is the key. That's my method of panel raising, too.

[Ole Anderson]

Off topic, but related. Years ago I was building barefoot waterski ski booms and I had taken in a bunch to the machine shop to turn down the end diameter of a six foot piece of solid 1.75" aluminum round stock (hardened 6061-T6) and to knurl the turned down portion. The operator stuck the bar in the CNC lathe, with at least 3 feet out the back of the machine, unsupported. If you know CNC, they always do things fast. Not sure of the RPM, but one bar must have had a small bend in it. Well, it went out of balance and it did turn into a string trimmer as it bent the boom nearly 90 degrees. The machine started moving across the floor and the boom started pulling through the chuck. It finally stopped when the boom pulled enough through the chuck so it hit the floor. After that they changed their shorts...and added a steady rest.

No, I wouldn't put an extention on my router turning over 20,000 rpm. I bet it would void any router warranty.