Tool Tip #22: Yonico Router bits

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Blog entry by robscastle posted 04-12-2016 12:37 PM 1072 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 21: Drilling Dimples or more correctly Pips in wood Part 22 of Tool Tip series Part 23: Yonico router Bits Technical information »

This blog although factual is technically incorrect see Yonico Router bits Technical information

Somebody really goofed with these, apart from the sucker who bought them.

I saw these on ebay

I have some Yonico bits so I was not too concerned, but I should have been starting from the heading.
5x Rail & stile half round, I am not sure how you would use them for Rail & Stile work however the are certainly half round.
Somebody has corrected the heading later in the body of the advertisment to:-
Half round bull nose Set.

The “Set” comes in five individual containers, as shown in the supporting photos
All the containers have no markings whatsoever displayed on them so I set about measuring them so I could mark the containers.
I should never have done that!
I made a total of six measurements, A the shank. B the bearing. C the top edge of the cutter. D1 and D2 the distance of each half round sections, and E the bottom edge of the cutter.
This is what I found,

Apart from the advert stating diameter sizes in two places the sizes are actually the radius measurements.
Secondly there is a variation in the measurements of at least 3mm in Dimension C and dimension E considering they, (in my mind) should be parallel not having a difference of about 3mm its very poor workmanship.

Now looking at the second picture

The shank is shown to be 1.1cm or 7/16 not half an inch thankfully its wrong also.

In my measurements on the left is their reported dimensions (2cm to 3.5cm) on top of each bit Of which I an not really concered as to their width but again would assume both should be at least parallel to each other.
See the refelected actual measurenets in Columns C and E.

The D1 D2 measurements should be 19.05,15.8, 12.7. 9.5. and 6.35
the 2.2cm or 3/8 should be 9.5225mm not 8mm otherwise its a ring in!

I am sure somebody has made some real klinkers here or am I just too fussy?

Some return correspondance

An up date, I would have thought the 1.1 would be explained away as a typo too,

received a email back saying 1.1cm is 1/2”
from memory 1.1cm is

0.437 expressed as a decimal or
7/16 expressed as afraction or
11.112 if expressed as mm

I also checked one of the other Yonico Bullnose bits I have

Measurement 1

Measurement 2

So confirming the two surfaces are in fact parallel I checked some other non Yonico bulllnose bits still the same parallel surfaces C and E.

So I sent off another email asking about the 8mm as opposed to 9.5mm?

I dont hold too higher expectations as to getting some factual replies but will keep you posted.

-- Regards Rob

3 comments so far

View johnstoneb's profile


3131 posts in 2780 days

#1 posted 04-12-2016 01:17 PM

The important dimensions are what they should be. A will fit a 1/2” chuck D1 & D2 are the same. E and C would only matter if material thickness is at or slightly over D and if so should go up in size anyway.

Yes you may be too fussy.

-- Bruce, Boise, ID

View Boxguy's profile


2864 posts in 2875 days

#2 posted 04-12-2016 05:14 PM

Rob, no you are not too fussy. There is nothing wrong with expecting tools to be sized as promised. Sloppy machining is just that…sloppy.

-- Big Al in IN

View MadMark's profile


979 posts in 2060 days

#3 posted 04-12-2016 05:36 PM

You get what you pay for. Sometimes bargains aren’t.
The 1.1 cm is obviously a typo in the ad, not a hard spec. Typical poorly translated Mandarin.
The bullnose radius is what you care about. As long as there is 1-2mm on either side the minimum spec is met and any more is uncontrolled. The critical dims all seem to be right.
Sometimes on cheap bits the carbide braze is off, but as long as the balance and final grind is right, who cares?


-- Madmark - [email protected]

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