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Author Topic: Router Bit SNAFU  (Read 991 times)

Offline little john

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Router Bit SNAFU
« on: April 30, 2018, 07:39:32 am »
The wonderful world of Imperial vs Metric ...

In Britain, although router bits come in both flavours - that is, in both Metric and Imperial sizes, their shanks are always either 1/4" or 1/2".  However, I received from China this morning a couple of bits which were advertised as being 1/4" ... only they aren't.  Their shanks are 6mm, not 1/4", and apparently the Chinese think that these two measurements are the same thing. 

Now although the collet of the router these were intended for will grip 6mm at the working end ok, the other (non-gripping) end of the collet with have nearly 14 thou of 'clearance' present, and the prospect of a router bit spinning around at 10,000+ rpm perhaps being as much as 14 thou out of true, doesn't really appeal very much.

What's needed now is some kind of circular (tube-like) shim to take up the difference at the non-gripping end of the collet.  Any bright ideas ?
LJ
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Online Acebird

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Re: Router Bit SNAFU
« Reply #1 on: April 30, 2018, 08:12:43 am »
You are buying directly from China?  You got two options, send it back or through it away.  You have the potential of getting hurt or destroying your router.  The odds are it has messed up your collet already.
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Offline Dabbler

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Re: Router Bit SNAFU
« Reply #2 on: April 30, 2018, 08:15:28 am »
LJ  Will your router accept a 1/2" collet? If so one of these bushing adapters might help.

http://www.leevalley.com/US/wood/page.aspx?p=30126&cat=1,46168,46180,30126

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Offline little john

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Re: Router Bit SNAFU
« Reply #3 on: April 30, 2018, 09:15:28 am »
Hi guys - yes, a 1/2" to 6mm adapter would be the perfect answer - if only that router was 1/2" !   But the router in question is a cheap and nasty 1/4" job which is permanently bolted to a sledge used only for the levelling of box edges.

Another solution would have been to buy a purpose-made collet, but I haven't been able to source one in the right size (10mm OD, 6mm ID, length 20mm.) - seems these things have never been standardised.

What I've done for now - although I haven't yet tested it - is to cut a length of shim steel from an old unwanted set of feeler gauges, which I've formed into something approaching a split tube (which was difficult with springy steel - should have removed the temper first, I guess), which I've then pressed into a spare collet - the one I've already tested.  With the 6mm shank in place it appears to be a very snug interference fit - but I'll still check for run-out and then fire-up the router remotely (from several yards away) when I come to run it for the first time.  Providing this proves to be an adequate 'fix', I'll then dedicate that particular collet to 6mm use only as yes, I'm sure it has become distorted.

Memo to self:  take more care when buying stuff from China in future ...
LJ
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Offline cao

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Re: Router Bit SNAFU
« Reply #4 on: April 30, 2018, 11:49:29 am »
As a machinist by trade(woodworking by hobby), I have had similar circumstances with metric/standard(imperical) size issues.  With me it usually is with drill bits and end mills.  I have solved it as you have except I have used a piece of brass shim stock and tighten extra tight.  In the case of 6mm-1/4", a piece of .005" shim wrapped around the shaft is what I have done.  The brass is easier to form and conforms to any imperfections in the bits.  There may be some slippage with heavy cuts so be aware. 

Their shanks are 6mm, not 1/4", and apparently the Chinese think that these two measurements are the same thing. 
It's found in more places than you think.  Around here you have to check because sometimes(more often than not) 1/4" plywood is 6mm.

Offline Hops Brewster

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Re: Router Bit SNAFU
« Reply #5 on: April 30, 2018, 11:55:33 am »
We run into a similar problem with SAE tools.  You grab your 1/2" wrench but turning a tight bolt you realize that the goofy manufacturer has simply stamped "1/2" on the "metric equivalent" 13mm ,  allowing .3 mm slop, destroying the bolt head.
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Online Acebird

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Re: Router Bit SNAFU
« Reply #6 on: April 30, 2018, 12:30:10 pm »
I would just get another bit with a 1/4 in shank.  I am not a machinist but I have run many mills.  When someone who does not have the experience starts cobbing things up they are asking for trouble.
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Offline little john

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Re: Router Bit SNAFU
« Reply #7 on: April 30, 2018, 12:41:36 pm »
There may be some slippage with heavy cuts so be aware. 

Thanks for that wise advice - as it happens I only ever take-off small cuts as with this 1/4" router I've been using 22mm diameter parallel bits (which have an end cutting surface of just a few mm.) to do the woodworking equivalent of surface-grinding.  I'm sure that a really deep cut would flex a 1/4" shaft to destruction.
What I've just sourced ex China are 'bottoming bits' which have a full 22mm end cutting surface, which I'm hoping will therefore last a lot longer - but I'm going to be even more cautious with depth of cut in view of that much larger contact area.

While I was looking for shim material, possible adapters and so forth - I came across 1" Chinese micrometers for 5 GB pounds - that would be around $7(?) in your money.  Ok - so I'm sure that as a pro machinist you wouldn't be over-impressed by such quality - but for the occasional user like myself, at first sight they appear to be ideal ... that is, unless you know a different story, of course ?
LJ
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Online Acebird

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Re: Router Bit SNAFU
« Reply #8 on: April 30, 2018, 02:07:57 pm »
to do the woodworking equivalent of surface-grinding.  I'm sure that a really deep cut would flex a 1/4" shaft to destruction.
It doesn't have to be deep.  Only the tip cuts.  On a 22mm cutter the tip is quite a distance from the shank.
I did as you are doing on an old butcher block made of hard rock maple.  It was warn to a depth of 3/4 inch.  I used a 1/4 bit and finished up with a belt sander.  I think you will find it is faster and it won't burn up your router.
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Offline cao

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Re: Router Bit SNAFU
« Reply #9 on: April 30, 2018, 08:36:12 pm »
While I was looking for shim material, possible adapters and so forth - I came across 1" Chinese micrometers for 5 GB pounds - that would be around $7(?) in your money.  Ok - so I'm sure that as a pro machinist you wouldn't be over-impressed by such quality - but for the occasional user like myself, at first sight they appear to be ideal ... that is, unless you know a different story, of course ?
I have some of the name brand tools and some of the chinese knockoffs.  They all have their place.  In general these knockoffs are less durable.  So if you need something that you use everyday, year after year then spend the money on a good quality tool.  If you occasionally use it then the cheaper version will probably be good enough. 

Online Acebird

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Re: Router Bit SNAFU
« Reply #10 on: April 30, 2018, 08:55:52 pm »
If you occasionally use it then the cheaper version will probably be good enough.
Certainly.  I would do the same.  But if you are cobbing it up because you can't admit you got screwed then you are not using your educated brain.  And that makes you stupid.
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Offline Bamboo

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Re: Router Bit SNAFU
« Reply #11 on: May 01, 2018, 04:01:02 am »
At the risk of stating the obvious why not bite the bullet and get the correct 1/4" shank router bit. Yes you are paying twice but get a quality one and it will last. Messing around trying to make something fit that won't, on something like a router that tends to spin at a great rate of knots just creates too much risk of damaging a) your router and b) you.
When it bites you it won't say sorry!
You seem to be a smart guy, don't do a dumb thing for the sake of a few pounds.