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cbsjoez1935 · 07-25-2007, 11:07 AM

Hi guys & gals,

Well here I am with another bit (no pun intended) of confusion. I had ordered a 1/4" flush trim bit with bearing attached. I decided, for some unknown reason, to put my micrometer on the bit. Here is what I found. The shaft measured .250 (14"), so far so good. The shaft that the cutters are on measured .236 (no big deal). The distance across the cutters measured .270 (should that not be .250?). No comes the kicker, the dearing diameter measured .275 (17/64"). Am I being rediculously concerned that with a bearing diameter larger than the cutter diameter I am not going to get a true flush trim following a pattern. I know, I know, wood is wood and not metal.

JoeZ

**bobj3** · 07-25-2007, 01:21 PM

Hi Joe

Because it's not a slotting bit that can be true, the bearing on the bit is the key....
You may want to check it one more time,, a quick way is chuck up the bit and make a pass or two...and if it does the job your good to go.... .005 is the standard for many router bits/bearings.....the .005 will change as the bit spins so to speak...point A to point B....thing...

Bj

Charles M · 07-26-2007, 06:31 AM

JoeZ,

It is sometimes difficult to get an accurate reading of the cutter diameter but as long as the cutter and bearing are concentric the 0.005" difference (which would only be 0.0025" on each side) shouldn't be a problem. If the bearing was smaller than the cutter you would have an issue. Also, just to note that the bit must actually be 7mm instead of 1/4" (6.35mm). What is the brand?

cbsjoez1935 · 07-26-2007, 12:02 PM

BobJ and Charles,

Thank you guys for getting back with that information. I may just be nit-picking where it is not necessary. Charles, my mic measures thousands, not mm, but coverting the measurement I made, .270 comes out around 6.9mm (close to the 7mm you recommended) so I should be OK. I have no idea of the brand since it was purchased from MLCS and those are usually Asian imports. These are my starter bits and I have had no problem with any of them. I was just curious about the measurements. Thanks again for you responses.

JoeZ

**bobj3** · 07-27-2007, 10:07 AM

You'er Welcome JoeZ for my small part

Bj

awh · 07-28-2007, 11:35 AM

Quote:

Originally Posted by cbsjoez1935

Hi guys & gals,
The distance across the cutters measured .270 (should that not be .250?). No comes the kicker, the dearing diameter measured .275 (17/64").

The actual diameter of a flush trim bit has no affect on its usage. The difference between the cutter and bearing is only 0.005" - that seems like it would be well within any manufactures tolerances.

07-25-2007, 11:07 AM	#1
cbsjoez1935 Registered User Forum Fanatic Join Date: Mar 2007 Location: Long Island, NY Posts: 113 View cbsjoez1935's Gallery	Report This Post! Flush Trim Bit? Hi guys & gals, Well here I am with another bit (no pun intended) of confusion. I had ordered a 1/4" flush trim bit with bearing attached. I decided, for some unknown reason, to put my micrometer on the bit. Here is what I found. The shaft measured .250 (14"), so far so good. The shaft that the cutters are on measured .236 (no big deal). The distance across the cutters measured .270 (should that not be .250?). No comes the kicker, the dearing diameter measured .275 (17/64"). Am I being rediculously concerned that with a bearing diameter larger than the cutter diameter I am not going to get a true flush trim following a pattern. I know, I know, wood is wood and not metal. JoeZ __________________ JoeZ If you never made a mistake, you never tried anything
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07-25-2007, 01:21 PM	#2
bobj3 Forum Contributer Supreme Forum King Join Date: Jan 2006 Location: Littleton,Colorado U.S.A. Posts: 7,535 View bobj3's Gallery	Report This Post! Hi Joe Because it's not a slotting bit that can be true, the bearing on the bit is the key.... You may want to check it one more time,, a quick way is chuck up the bit and make a pass or two...and if it does the job your good to go.... .005 is the standard for many router bits/bearings.....the .005 will change as the bit spins so to speak...point A to point B....thing... Bj __________________ Bj
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07-26-2007, 06:31 AM	#3
Charles M Registered User Forum Fanatic Join Date: Apr 2006 Location: High Point, NC Posts: 174 View Charles M's Gallery	Report This Post! JoeZ, It is sometimes difficult to get an accurate reading of the cutter diameter but as long as the cutter and bearing are concentric the 0.005" difference (which would only be 0.0025" on each side) shouldn't be a problem. If the bearing was smaller than the cutter you would have an issue. Also, just to note that the bit must actually be 7mm instead of 1/4" (6.35mm). What is the brand? __________________ Charles M Freud America, Inc.
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07-26-2007, 12:02 PM	#4
cbsjoez1935 Registered User Forum Fanatic Join Date: Mar 2007 Location: Long Island, NY Posts: 113 View cbsjoez1935's Gallery	Report This Post! BobJ and Charles, Thank you guys for getting back with that information. I may just be nit-picking where it is not necessary. Charles, my mic measures thousands, not mm, but coverting the measurement I made, .270 comes out around 6.9mm (close to the 7mm you recommended) so I should be OK. I have no idea of the brand since it was purchased from MLCS and those are usually Asian imports. These are my starter bits and I have had no problem with any of them. I was just curious about the measurements. Thanks again for you responses. JoeZ __________________ JoeZ If you never made a mistake, you never tried anything
	Top - Reply with Quote

07-27-2007, 10:07 AM	#5
bobj3 Forum Contributer Supreme Forum King Join Date: Jan 2006 Location: Littleton,Colorado U.S.A. Posts: 7,535 View bobj3's Gallery	Report This Post! You'er Welcome JoeZ for my small part Bj __________________ Bj
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