I purchased a RB420+4th Axis. 4th Axis installed as option 2 (fixed angle/full length). Mounted a Dewalt 625 on the router plate with a 4” long bit. The bit isn’t able to reach far enough to turn a piece to 1.5” diameter. Did I install something incorrectly? If not, does anyone have a recommendation for a bit?
Installation/router bit recommendation
- Thread starter HI-Dad
- Start date
larry.thomson
Moderator
i would suggest the CMT collet extender from AMZ -- https://www.amazon.com/gp/product/B000P4NQCK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 -- or wherever you like to get your stuff -- it allows you to get the bit far enough down -- spins perfectly -- i have the same router -- have turned down to 3/4" dowels/pins using it
larry.thomson
Moderator
i have not had any issues with the CMT -- it chucks down like a 'normal' collet so everything is centered -- there isn't any difference in the sound of the router spin with it on or off -- i have tried quick exchange collets in the past and had not found one that didn't unnerve me when it spins -- but i believe the last one i got from chipsfly worked well -- i don't use it because i don't have a problem changing out bits wit the OEM collet so it didn't seem necessary -- think you will be happy with the CMT --
Last edited:
Geoff Peters
New member
I too am leary of extending my bit beyond what the OEM chuck/collet provides.I purchased a quick change chuck from Chips Fly and even though it increased the reach of my bits, I found that just by nature of its extension it magnifies whatever runout the Dewalt has. Trying to make 1 1/2” mortises was touch and go for me as the deeper I went with the bit in the wood, the more the runout at the end of the 2” bit would bind on the side wall of the mortise. If your router has,say, a .0001 runout up at the chuck, by the time you get to the end of a 2 “ bit, the runout is magnified significantly. I finally went back to the OEM collet an get more precise routing without the vibration associated with the extension of the quick change chuck. Also, I only ran the bit at the 2.5 speed setting. Larry, have you ever done a runout test on the CMT collet extender? I’d be interested in trying one if it spins as smoothly as you say.
larry.thomson
Moderator
i do not have the tools to do a definitive run out test -- i went by sound at first because of my experience with the quick change collets -- i have not noticed that any activity i did with the CMT in place was ever compromised -- and i use it all the time -- especially with the 4th axis -- i made the drawer inserts for an armoire for my wife and i am pretty sure i would have used the CMT because of the distance to the mortise table and a 1/8" straight bit and they fit perfectly -- also, did some interior slots for plexiglas dividers in a brochure box -- again, the distance to the mortise table would have dictated using the CMT -- they fit great -- the slots for the inside dividers were 3/32" [0.094] the plexiglas was 0.080 -- so if the slots were mis-aligned by more than 1/128th -- the plexiglas wouldn't go all the way down -- i think i would see any run out in these sort of applications --
Geoff Peters
New member
Thanks Larry. I’ll give the CMT extender a try.
larry.thomson
Moderator
i used it today to cut some dados in a board that was 3 1/2" below the base plate -- 1/2" spiral bit, 3/4" dados -- for reasons that i will go into if forced -- i used the x axis DRO to position the bit at center, left side, rt side of dado -- i think if i had any walk in the CMT extender -- the resulting dado would have been > 3/4" -- they came out good --
One of the problems using large bits and long bits is runout causedmade even more dangerous at high speed. Routers typically run at about 20,000 RPM, and a long bit or large diameter bit shouldn't be run that fast. Some router have integrated speed control, but I find that the best speed control comes from a dedicated device which can be used on a multitude of tools. You can find loads of them on Amazon priced from about $15 to $30 dollars. If you reduce3 the speed to say 7,000 RPM and feed slowly it should alleviate your concerns.
Geoff Peters
New member
I agree. On the Dewalt 625 on the Router Boss, I generally run my 1/2” diameter bit at somewhere between 2 & 3 on the variable speed dial. I believe that equates to 12,000-16,000 RPM. I just slow my feed rate down.
Geoff Peters
New member
I just checked my last setting. I set it at 2 or 12,000. I try even slower as you suggest.
Larry, runout can occur in the router itself, a collet, the chuck, a chuck extender, and/or the cutter, More than a few thousanths cab be dangerous, particularly at high speeds. Some times slightly moving the cutter position, or changibg the tightness of the collet, can correct (or worsen) runout. Unless Im running large bits, especially at high speeds, I don't usually bother checking. A thousanth or 2 doesn't usually make much difference, but it can with collet extensions. A thousanth of an inch at the collet can be 10 thousandths (or more) at the tip of the cutter on a deep cut.
You can easily spend over $500 on a hgh end Dial Indicator, I inherited my Starrett from my father over 40 years ago, That said, even a cheap one is more than adequate to test runout of about .00025 which should be nore than .accurate enough. Here are 2 cheap ones from Amazon that read out in thousanths (.0001) and the graduations are far enough apart to read a quarter of that.
$15 - https://www.amazon.com/Professional...eywords=Dia;+indicator&qid=1591635078&sr=8-49
$16 - https://www.amazon.com/HFS-0-001-IN...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
And, of course, you can tell if runout exists without an indicator. Just mount a stick so it barely brushes a cutter and hand spin the router to see of the next cutter edge brushes.
larry.thomson
Moderator
many thanks for the information -- i guess i evaluate any run out by how well the pieces of a cut i am doing fit together -- so i could have 0.010 error and be blissfully unaware -- i hope i would recognize 1/64" -- i use a collet extender all the time -- and mostly 3/8 or 1/2" spiral straight bits -- and the dewalt 625 router -- certainly something to be aware of --