[Aryantes]

I just recently got my CNC set up. It is a FineLineAutomation / CNCRouterParts inspired design and I used their carriages, rack and pinion set up, Z axis bearing blocks, motor mounts, and a few more items I'm sure. The router is up and running minus homing/limit switches which will go in soon.

I use a Hitachi M12VC router with the K2CNC mount.

After a few test cuts I realized that the precision was not quite there.

Plunged holes were 0.27" in diameter with a 0.25" bit.

All squares were coming out too small and always by the same amount, each side roughly 0.025" - 0.030" short. All circles were coming out too small as well.

I checked for backlash and couldn't find any. I used my Harbor freight Dial Indicator (0.001" accuracy) and if I told Mach3 to move my gantry 1", it moved exactly 1", within 0.001".

Next thing I did was checked runout on the spindle. I took an extra piece of cold rolled steel I had from a previous gantry setup to attach my dial indicator's magnetic base.

First I took the collet off and checked the runout of the spindle itself and found none.

Then, I put a 1/4" bit and the stock Hitachi collet on, put the dial indicator against the flat part of the shank and rotated the collet by hand to check the runout.

To my surprise, 0.012" of runout! This was at a point very close to the collet, which means at the end of this long bit, the runout would be even worse!

I tried a few different times, to see if the runout would be different if I varied how deep I put the bit in the collet or how much I tightened the nut.

The runout would vary between 0.006" and 0.012".

I took some video here for you guys (in glorious 1080p! :cheers. Read on to learn more about PreciseBits!

DISCLAIMER: I am not affiliated with PreciseBits or Think & Tinker in any way and they aren't paying me to do this. I am just an excited enthusiast like you all who happened to solve one of my problems and hopes that this can help solve yours.




Here are some pictures of my results and an overview of the PreciseBits package. Click on picture for High-Resolution version.

Stock Runout:




I ordered the Deluxe Bosch 1618 Collet Kit (contains 1/8in. , 1/4in. & 1/2in. PG collets, collet nut, spanner wrench and 118 ml of ColletCare) - BOPG-1618-842KIT These Bosch collets work for the Hitachi and are advertised as such on their website.

It also comes with a Calibration Blank, 1/8" diameter, that you can use to check runout. However, I didn't have a 1/8" collet for my Hitachi so I stuck to using my 1/4" bit and collet for my comparisons.

It came packaged very nicely, with no damage in shipping.

Collet and nut came slightly oiled. I assume this is to prevent corrosion during storage.

Original Packaging:


Opened:


Precision Collet and Collet Nut:


There are instructions included on how to clean out the bore of your spindle.

I would imagine this is pretty important. You turn the router on. BE CAREFUL. In this case, I set my Hitachi to run at it's lowest RPM which is 8000. You put a few drops of the ColletCare cleaning liquid on the tip of the cotton swab and carefully swab the dirt out. I ended up using a bunch of cotton swabs before the inside seemed clean enough.





PreciseBits website has instructions on how to properly insert the collets into the nut. It will take a bit of practice to get used to removing them as well.

I mounted the 1/4" collet and put my router bit back in.

I repeated my test for runout and found that it had been decreased to 0.001" !!

PreciseBits Runout:




There was a bit of trial and error here and I found that my router has a sweetspot for how far inside the collet the bit likes to be. Somewhere between 1/4" and 1/2" for mine. Try it a few times and measure your runout each time.

No, I am not cheating hehe. All pictures are taking at the extremes.

I decided to verify my results. I mentioned earlier that my plunged holes were 0.27" in diameter on a .25" bit. I plunged another hole with my new setup.

Success! 0.25" bit yields a 0.25" hole. At least, to within my ability to measure it.

Stock Collet:


PreciseBits Collet:


I highly suggest picking up a set if your router has any significant runout.

Maybe my Hitachi is kind of defective or something, but these collets seem to fix the issue and I look forward to some awesome CNC'ing soon.

The difference for me will be huge especially since I plan on machining aluminum and want pieces to fit together nicely.

Hope this was informative!

Aryantes

[JD68]

Very informative. Nice job!

Thanks, JD

[ger21]

Did you check the runout with the stock collets after cleaning the taper? You had a lot of dirt in there, which may have contributed to the runout.

[Aryantes]

Did you check the runout with the stock collets after cleaning the taper? You had a lot of dirt in there, which may have contributed to the runout.

Indeed!

The first pictures with the dial indicator are before the cleaning.

Then I realized a dirt to no-dirt comparison is not quite fair. So I took some new measurements, a few of them and had similar results. 0.009-0.010 max TIR on stock. Sometimes around 0.006". So the dirt definitely had an impact, but didn't quite solve the problem.

In the video, both stock and precisebits measurements are taken after cleaning.

[ger21]

Thanks.

[BackyardWorkshop]

I too have the Hitachi M12VC and Precise Bits Collet set and I second the review - totally worth getting

[Dynamech]

Very nice review!

I'm planning on using Precise Bits with a Bosch Colt and I'm happy to see that their craftsmanship translates to other routers as well.

[cnctoolman]

I have the kit for the colt and love it. You wont go wrong with it.

[marzetti]

I have the same Hitachi router and experienced similar results. I bought the Precise Bits collet set specifically for using very small endmills (0.02") for inlay work but found they made a noticeable difference using normal size bits also. Even the noise level while cutting was improved! I would highly reccomend these collets as well.