# 3/8 tongue & groove assembly bit



## johannmendelsohn (Mar 17, 2014)

I have bought a 3/8 tongue & groove assembly bit but find that the tongue fits too loose into the groove or otherwise. Also with it assembled as bought, when cutting the tongue, a thin piece on both outsides stays uncut when using 22mm stock, which is standard here in South Africa. 
I took the assembly apart and am not so sure of the sequence of fitting the washers, copper, and thin and thicker steel? If one has to use one of the cutters to cut the groove, surely the bearing between the cutters should be of the same thickness as either cutter to cut the tongue?
Please help!
Thank you
Johann


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## Cherryville Chuck (Sep 28, 2010)

Johann standard thickness in North America is 19mm so that is probably what it was designed for. You can often feel the difference in spacer thickness or you can similar ones up and multiply the differences. You have to make sure that any spacer only touches just the inner race. If it touches both the bearing won't turn. Depending on how the cutters are made you may have to have at least one spacer or it may work without any.


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## denis lock (Oct 26, 2007)

Hi Johan. You state that it is a 3/8" cutter. Are you referring to thickness of the tongue and groove or the depth? I suspect the latter and that you have a 1/4" T&G cutter which will work in boards up to 3/4" (19 mm) as stated by Charles. What is the brand of the cutter and the part number?
Denis Lock +27-11-616-6576


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## MAFoElffen (Jun 8, 2012)

As explained by Charles... If you look at the Groove bit in the set, you should find that it is adjustable via shims... (most sets).


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## old55 (Aug 11, 2013)

Welcome to the forum Denis.


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## Stick486 (Jan 4, 2013)

johannmendelsohn said:


> I have bought a 3/8 tongue & groove assembly bit but find that the tongue fits too loose into the groove or otherwise. Also with it assembled as bought, when cutting the tongue, a thin piece on both outsides stays uncut when using 22mm stock, which is standard here in South Africa.
> I took the assembly apart and am not so sure of the sequence of fitting the washers, copper, and thin and thicker steel? If one has to use one of the cutters to cut the groove, surely the bearing between the cutters should be of the same thickness as either cutter to cut the tongue?
> Please help!
> Thank you
> Johann


what brand of bit do you have???


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## johannmendelsohn (Mar 17, 2014)

Hallo Denis. It is a PRO-TECH KP609011, 1/4" shank.
label says: Bit Tongue & Groove assem 3/8 x 1/4.


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## johannmendelsohn (Mar 17, 2014)

If I shim it out to 22mm, it seems a bit much, but then the single cutter's cut will be too narrow for the tongue, or am I wrong?


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## denis lock (Oct 26, 2007)

Hi Johann. KP609011 is designed to to cut T&G joints in stock from 12mm to 19mm thick.The shims are there for fine tuning of the joint fit.The cut could be fractionally different in a dense wood when compared to a cut in soft pine. The shims are also for use after the cutters have been sharpened. Sharpening reduces the size of the groove fractionally.

If I had to cut T&G in 22mm material I would use the T&G cutter to cut a 1/4" groove in the one board and then use a rebate cutter (KP3503 plus a KP3803/2 bearing) to cut two 8mm (approx) rebate cuts on the second board to form a 1/4" tongue. This is messy and requires additional accurate router table setup.

You could cut the two 8mm rebates by playing with the bit height and making multiple passes with one of the cutters from the T&G set. Even messier.

The question I must ask is why do you want to cut a T&G joint in 22mm material? To create wider boards by edge-to-edge jointing? If yes then read my article in the August 2014 issue of The Home Handyman (SA) magazine. I maintain that T&G joints are unnecessary.

Denis Lock +27 11 616-6576


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## Cherryville Chuck (Sep 28, 2010)

To add to what Denis said, I would set it for 19mm and set the rebate cutter on the bottom flush with the table and machine the good side face down. Then you just have to trim the remaing wood off with a second machine operation or on the table saw. 

I also agree with what Denis said about needing to join 2 boards together. In most cases a tongue isn't necessary. If you think it is I would go with a spline joint instead. Tongue and groove joints and glue joints loses some of the width of each board whereas a spline joint doesn't lose any and it's just as strong and much easier to machine.


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## Stick486 (Jan 4, 2013)

Cherryville Chuck said:


> If you think it is I would go with a spline joint instead. Tongue and groove joints and glue joints loses some of the width of each board whereas a spline joint doesn't lose any and it's just as strong and much easier to machine.


another note for the spline...


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