TIR Measurements on a Bosch Colt Palm Router (TIR exceeds specifications)
Note: Because of design changes by the manufacturers, we no longer support:
Rigid Palm Router (R2400)
Porter-Cable 2.25 HP routers (890, 892, 893, 895)
We will continue to offer Bosch-Colt / Rigid 2400 collets and spanners to customers who have previously purchased PreciseBits collet kits.
Porter-Cable 890 series routers manufactured before the collet chucks were changed are still compatible with our Porter-Cable 7500 family collet kits, collets and nuts
Up until the beginning of 2011, the Bosch Colt Variable-Speed Palm Router (PR20EVS) was, in our humble opinion, one of the best trim router on
the market. The bearings were exceptional, the motor noise relatively low, and TIR (Total Indicated Runout) low enough to consider this tool a suitable spindle for light-duty CNC machining. To be honest, the OEM nut and collets could have used some work and the
absence of a 1/8" collet from the manufacturer, substantially reduced its utility in digital woodworking and printed circuit fabrication. Nonetheless, it was a good fit for light-duty applications.
An added irritation was the fact that the front spindle bearing is mounted in a plastic (meltable) ring, instead of a heat-sinking metal seat.
Unfortunately, as with any consumer grade appliance, manufacturing tolerances can vary enough to make some members of this family of tools unsuitable for precision work. Such is the case of the Colt graciously sent to us by Chin-Kai Chang of iLabs at USC (University of Southern California). During his evaluation of our BOPG-COLT nut and collet set, he found that no amount of cleaning, tightening, or adjusting would bring the TIR into specification. His series of videos which can be seen on YouTube) clearly show that his evaluation technique was quite good and that he was very capable of performing precision measurements.
When our testing lab received his Colt (complete with both the OEM and BOPG-COLT nuts and collets) we wanted to see if we could figure out just what was going on. The test procedure is best revealed through the following series of videos.
Bosch OEM nut and 1/4" collet in the TIR Test Stand
First we wanted to see how the OEM nut and collet measured when mounted in our TIR Calibration Test Stand. Since we wanted to determine the type of runout, we took measurements using a 1/4" shank tool with a measured TIR = 0.000050" with the test probe adjacent to the face of the collet (picture at left) which yielded TIR = 0.0046"
We then moved the probe to a point 1.25" down the shank from the collet (picture at right) showing a TIR = 0.0083".
Bosch OEM nut and 1/4" collet in the Bosch Colt Palm Router
Next we mounted the OEM nut and collet into the Bosch Colt and measured the TIR at the face of the collet. (see picture at left). At TIR = 0.0023", it was actually better than the results using our test stand.
I cannot find the video of the measurement at 1.25" from the collet face, but the test records indicate a TIR = 0.0056". Again, the results were better than on the test stand. Since I do not have a video of the test, here is a picture of my lab.
BOPG-COLT nut and 1/4" collet in the Bosch Colt Palm Router
Prior to sending us the Bosch Colt to test, Chin-Kai had shown that our BOPG-COLT collets, when mounted in his router not only failed to meet our published specifications, but were substantially worse than the OEM collet.
Naturally we had to see for ourselves. As above, the video on the left shows the results of measuring the runout adjacent to the collet face (TIR=0.0051"), and the video on the right with the probe about 1.25" down the shank (TIR=0.0131").
Zut Alors! Truly abysmal!
BOPG-COLT nut and 1/4" collet in the TIR Test Stand
Our first thought was that, even though our BOPG collets are 100% inspected to insure compliance with the published TIR specification of < 0.0004", the collets shipped to Chin-Kai were defective and should not have passed. When mounted in the test stand, that did not prove to be the case. As above, the right picture is the TIR measured 1.25" down the shank (TIR=0.0008").
Measurements at the face of the collet yielded TIR = 0.0003".
BOPG-COLT nut and 1/8" collet in the Bosch Colt Palm Router
But what about using the 1/8" collet in the Colt? As the video shows, the results were not much better than the 1/4" collet. The TIR measured at the collet face = 0.0043" (left) and about 1.00" down the shank the TIR = 0.0083". Ten times greater than the specifications and totally unusable for working with tools less than 0.0938" dia.
Actually, runout that severe makes the collet useless for any kind of precision work.
BOPG-COLT nut and 1/8" collet in the TIR Test Stand
Again the question arose. Was this collet simply a defective part that fell through a crack in our inspection protocols, or was something else going on? Only one way to find out. We mounted it in the TIR Test Stand and repeated our standard QC measurements.
At the collet face TIR = 0.0003" and 1.00" down the shank TIR = 0.0003". Well within specifications.
After a fair amount of discussion and measurements inside the taper of the Bosch Colt, a rather disturbing fact emerged. The angle of the taper was larger than that of any other Colt we had measured and the wall did not form a linear cone. Rather, it bulged slightly inward in the center which prevented our hardened (HRC 52 min.) spring collets from accurately seating in the spindle. Removing the nut from the collet we noticed that when we pushed the collet into the taper it could be wiggled back and forth and could not find a secure seat (a sure sign of a mismatch between the collet and taper geometries). It was not clear why the OEM collet worked so much better than our BOPG collet. During discussions on this curious behaviour, it was suggested that, since the OEM collet is not very well hardened, perhaps it was forced to comply with the deformation in the taper and was able to achieve a more concentric seat. Unfortunately, we do not have the tools to accurately determine if this is true.
What does all this mean to the user? Not all Bosch Colts are created equal. The best test we have been able to come up with to see if a Bosch Colt (or Rigid 2400) will work with our collets is:
- take a BOPG-COLT-1/8 (or BOSG-COLT-1/8) collet, a 1/8" calibration blank, a few Q-tips and a fine-tip permanent marker to the store with you
- remove the OEM nut/collet from a store model (
probably good idea to ask the store clerk for permission first)
- clean out the router's tapered bore with a Q-tip
- use the permanent marker to draw 2 broad, heavy lines, 180° apart, from the inside of the tapered bore to the mouth (widest part)
- let the ink dry (
we do NOT want to smear it during this test, we want sharp, easily seen scratches)
- insert the calbration blank all the way into the collet with about 1/8" hanging out the back
- using your thumb and index finger, press the collet FIRLMY into the bore
- grip the end of the calibration blank with your other hand and see if you can wigggle the collet back and forth
- leaving the blank in place and holding the router shaft to keep it from turning, rotate the collet in the bore 2 full turns with moderate pressure
If the collet seats snugly (no perceptible movement), it is probably a good match. If there is any apparent movement between the collet and the router shaft, remove the collet and look at the 2 black lines that you drew inside the bore
- If the ink is only rubbed away deep in the bore, about where the end of the collet would hit, the collet is bottoming out against the narrow part of the taper. This indicates that the bore taper-angle is larger than the collet taper and, unfortunately, incompatible with our collets.
- If the ink is rubbed away near the mouth of the taper, or evenly along the length of the line, the collet taper and the bore taper have a relatively good match. The collet will probably work quite well with this router, in spite of the slight movement you might have felt above.
As with all of our tools, the collets, nuts, and spanners come with our standard no-fault guarantee. If you cannot find a COLT that will work with the collets, return the nuts and collets to us for a refund. Cold comfort to be sure, but the best we can do at the present time.
The Bosch 1617/1618 and Hitachi M12 routers are the same diameter as the Porter-Cable 890 series (3.5 in.) and are drop-in replacements.
The Dewalt DWP611 is 2mm (0.080 in) smaller in diamter than the Bosch-Colt and Rigid 2400 but is compatible with most mounts with the use of shims.