Need Advise To Make A Router Collet

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martik777

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The 1/2" collet for my router is no longer available so I'd like to make one. It has a 1/4" collet (photo attached) that fits into a .560 ID hole in the motor shaft. The collet nut is the same for both 1/4 and 1/2 collets.

What concerns me is that the 1/2" collet will be very thin (.030") inside the motor shaft. At 25k RPM will it be safe? I plan to use 4140, not hardened.


974252-003 collet.jpg colletinfo.jpg 974252-003 collet.jpg
 
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I would use 4130 heat treated to around RC30. If the original collet was large enough to leave that small of a wall then there should be no problem as long as the fit is close. The Nut also helps add some mass to the shaft.
 
I would say it will be safe since everything is contained by the nut.

David
 
If the 1/4" collet is still available I'd just buy it & modify to 1/2". I've not seen 1/2 shanks for a router. But maybe that's because I only use 1/4" & 1/8" in mine so I never looked for them. Actually I don't think I've ever seen 1/8" shanks ether but mine came with a collet for them.
 
I would first make sure that I made it as concentric as possible. You do not want an out of balance condition. Secondly, I would use 1144 as the material…Dave.
 
Perty' much like you and everybody or some are saying here (saying for an easy "no heat treat part") just turn it up out of prehard 4140...

...I'm assuming that's .030 wall thickness in back when your done? ...should be ok but even 030 wall might "dent", (even at rc 30) if you drop it (LOL)...also it still should be ok if not a prehard 41 hundred series but sure not as good and OD's and ID will wear more so you would have to be more "tender" with it over it's life

...or yeah, and as above said: Modify a new 1/4" (bore if it's not too hard?, (or if toolpost or ID grinder is available ifn' its really hard?) Or if EDM with a rotary head is available with about a .496 carbon "trode' (Smiley Face here)
 
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Make from scratch, turning and poring in one setup for best concentricity. drill termination holes before slitting to stop the part from cracking at the thin walled section.
 
collet12.jpg


Finished the part tonight (used 4140), old part on the right. The diameter of the bore tightened up after I slitted the part but it runs with no visible runout.

Now I just need to make the LH retaining screw, although it seems tight enough with the collet nut tightened down.

The retaining screw has a very thin washer beneath the collet which allows the collet to rotate when it is not tightened down. I'm not sure what purpose it serves, maybe a safety if the collet slips it will spin on the washer?
 
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That washer is probably a retainer to keep the collet in the spindle while pulling on a cutter out.
 
I don't know routers myself ...I'm only used to ID threads in the back of collet's to be used with a stop assembly if needed.
 
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