# What Is A Mortiseing Bit?



## Jerry Bowen (Jun 25, 2011)

O.K., here I go again with a new question. This one is in regard to a mortiseing bit. I have been reading about them but still am not clear as to how they work so here I am asking again.

What I have been envisioning is a bit, much like a straight bit that can be usined on my router table. I would like for it to work in a way that may not be possible, it's only a hope on my part. But, I would like to plunge it into the workpiece on the router table cut the length of the mortise and end up with square corners on both ends of the mortise. I would not need to use chisles to square the corners up, but all of this is probable just wishful thinking, but I just had to ask. 

Now, if my hopes are dismissed I have been thinking of using the straight bit and then sanding the area of the tendon into a rounded shape to fit the radiuses left by the straight bit. Where am I going wrong in this endeavor?

Jerry
Colorado City, TX


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## boogalee (Nov 24, 2010)

Jerry

Your thinking is correct. If you use a round router bit to cut the mortise then you will have round corners. Sanding will take a lot of time. You could use a corner chisel to square the mortise.

Corner chisel

3/8 corner chisel

Al


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## richtink (Dec 5, 2012)

I don't think I have ever squared a mortise or rounder a tenon.


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## Jerry Bowen (Jun 25, 2011)

richtink said:


> I don't think I have ever squared a mortise or rounder a tenon.


Richard,
You have touched on an issue that I had meant to ask about, why worry about the radiuses at the ends of the cuts. They will be hidden anyway and the joint should still be pretty strong. Is that what you are alluding to?

Jerry


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## JCJCJC (May 15, 2012)

No-one has yet figured out how to make a rotating tool cut square internal corners. A CNC router could probably cut square external corners satisfactorily. Modern woodwork has gravitated towards round tenons in round-ended mortices, as well as floating tenons in round-ended mortices, probably due to the explosion in popularity of routers. Strictly speaking, a morticing bit is like this, from what Norm calls a dedicated morticer, where the square chisel cuts the mortice and the bit, which runs inside it, removes the waste upwards simultaneously. Leverage by the operator advances the chisel assembly into the work. I know of no other technology to produce a square-cornered mortice, so this is the only bit as such that does what you're asking.








.


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## Jerry Bowen (Jun 25, 2011)

JCJCJC said:


> No-one has yet figured out how to make a rotating tool cut square internal corners. A CNC router could probably cut square external corners satisfactorily. Modern woodwork has gravitated towards round tenons in round-ended mortices, as well as floating tenons in round-ended mortices, probably due to the explosion in popularity of routers. Strictly speaking, a morticing bit is like this, from what Norm calls a dedicated morticer, where the square chisel cuts the mortice and the bit, which runs inside it, removes the waste upwards simultaneously. Leverage by the operator advances the chisel assembly into the work. I know of no other technology to produce a square-cornered mortice, so this is the only bit as such that does what you're asking.
> 
> 
> 
> ...


John,
What you are saying about not being able to cut a square hold with a rotating bit is exactly why I have begun asking my question. It seems to be that a straight bit would cut mortise just fine, and the corners of course would be rounded. I am not certain how flat the bottoms of the cuts would be or how important being flat really is. In a post above yours, Richsrd has implied thst he just leaves the rounded corners alone. Also, cutting mortises in the manner that I am decribing would only be appliable to relatively small work pieces that could be handlled on a router table. Do you have any opinion as to leaving the corners rounded as Richard has implied that he does. I do appreceicate your taking time to address this matter for me.

Jerry


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## bobj3 (Jan 17, 2006)

Hi

They do make and sale a router bit that will cut a true square hole ..it looks like a triangle router bit...

===


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## JCJCJC (May 15, 2012)

Jerry Bowen said:


> John,
> What you are saying about not being able to cut a square hold with a rotating bit is exactly why I have begun asking my question. It seems to be that a straight bit would cut mortise just fine, and the corners of course would be rounded. I am not certain how flat the bottoms of the cuts would be or how important being flat really is. In a post above yours, Richsrd has implied thst he just leaves the rounded corners alone. Also, cutting mortises in the manner that I am decribing would only be appliable to relatively small work pieces that could be handlled on a router table. Do you have any opinion as to leaving the corners rounded as Richard has implied that he does. I do appreceicate your taking time to address this matter for me.
> 
> Jerry


Thanks Jerry. Nothing at all wrong with rounded corners. It's a combination of the cross-sectional area and glueing surface area that will give strength to the joint, so round or square makes no appreciable difference. It's really just a matter of moving with the times. If you're making through-mortices where the endgrain of the tenon will show, and if it's a replica or period piece, it just won't look right with round tenons, that's about the only time it'll matter to any extent. If you wedge the mortice, it'll add about the same amount of strength and resistance to pull-out. My father (RIP) used to always do what he called 'secret fox-tail wedges' in blind mortice and tenon joints to resist pull-out. He fitted the wedges in the usual manner to the tenon with a good dash of glue, and they seated themselves as it was driven into the mortice, once and for all time usually.


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## richtink (Dec 5, 2012)

Jerry Bowen said:


> Richard,
> You have touched on an issue that I had meant to ask about, why worry about the radiuses at the ends of the cuts. They will be hidden anyway and the joint should still be pretty strong. Is that what you are alluding to?
> 
> Jerry


Yes Jerry, since he was talking about the bottom of the mortise, I figured I would not address through tenons, which should be asthetically pleasing to the eye. Those are usually in thicker applications and a drill press and table saw would be the tools of choice for that.


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## mgmine (Jan 16, 2012)

If you don't round off the corners then the tenon won't fit. You can't put a square object into a round hole which is what the corners are. When I use a mortise and tenon joint I cut the tenon on the band saw to fit the mortise size. Also you can't cut the mortise with a straight bit, a straight bit will only cut edges and can't be plunged. You will need to use a spiral bit. IF using it on a table then a downward one, if using it with a plunge router then an upward one.


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## Jofuss 55 (Oct 17, 2011)

Jerry,
No router bit made leaves square shoulders.
A mortising bit has carbide on the bottom of the bit that cuts a flat bottom, as well as sides


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## MAFoElffen (Jun 8, 2012)

Okay you guys... I know how to do this joining technique and darn it, you are confusing me with those descriptions. I'm sure if you are confusing me, then I feel sorry for those that don't know. So let's see if I can chip through some of this confusion.

There is a router bit named a "mortising" bit. This is for creating a shallow mortise (a hole or recess cut into a part) for mortising in hinges and such, not for creating a deep mortise for a mortise and tenon joint. This bit is too shallow to create that deep of a hole. Another problem with trying to use that bit for a deep hole is that is doesn't clear the hole of chips fast enough or well..

Yes, you could use a straight bit, but IMHO, the best router bit for this kind of mortise hole is a spiral up bit, which does clear chips out of that hole efficiently and fast. Yes you end up with a rounded hole, not square corners... But if you clean to hole out with a wood chisel, you can square out the corners of the recess. 

If you don't want to take the time to square out the corners, you can use a loose tenon made on your router table... Or you can create a rounded tenon with a tenon jig and a bushing. The length of your tenon is limited to the spiral bit you are using. What this does is mounts to the end of the stock, with the end facing up. You cut down onto the stock with a handheld router, with the tip cutting/creating the shoulder and the edge of the bit cutting/creating the shape of the tenon. 

Next is the classic mortising bit, used on a mortiser, like those found as an attachment to jointer/planers. The motirtiser bit its like a long spiral cutter bit and creates a slot with rounded corners. The table of the mortiser holds the stock, moves it onto the bit and slides the stock back and forth to create a slot. Again, you can square out the hole with chisels or create a loose tenon joint with a rounded tenon.

Then there is a mortiser that looks like a small drill press. This uses a mortising chisel bit, that was pictured a few posts back. This "bit" can also be used with a drill press, if you have a mortising bit attachment for your drill press. This mortising chisel bit will not work without one of these two things. An explanation will clear that up. The bit is two part. The inside spins and clears the chips as the chisel drops down and trims a squared hole. The outside collar that is part of the square chisel is held in place and therefore should not spin. The collar of the mortiser or the drill press mortising attachment is what holds the collar of the chisel from spinning and presses it down the hole as it gets drilled. Rectangular holes are made by drilling holes next to each other. 

Some people think that since they have a drill press, they go out and buy a mortising attachment instead of buying a mortiser... By the time you get all the parts, you end up paying "about" as much as an inexpensive mortiser. Unless, you buy the bargain brand drill press mortiser attachment ($49). I read a good reputable review of a test from a mainstream woodworking editor who tested 3 drill press mortising attachments, then went back and tested those two named brand and the one bargain brand drill press mortiser attachments against each other... The results where so close between the three, that he picked the bargain brand as the winner. What he did say as a tip for mortisers or drill press mortiser attachments is to go back and buy a quality mortising chisel bit for the size(s) you use most often. 

Drill press- drill holes next to each other and clean out with a chisel. Can do same with an auger and brace.

Does that clear things up now? I hope so.


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## bobj3 (Jan 17, 2006)

hi

You don't need to round over the tenon once they are in the pocket hole they are in and you will not see the square ends anyway plus you have some room for the glue..you could say a wedge fit joint.. 

You don't need a drill press to use the mortising attachment it can be used with a soft face hammer and drill motor..if you want square end pocket holes.just drill some holes and use the SQUARE chisel to clean it out...they come 1/4" TO 1" in size.. you can make some hardwood handles if you want to hold the tool.

You can use the LONG drill bits made by JessEm in your router for the deep holes,they are HSS and will hold up for what you want to get done,I have not use drill bits but I don't see why you can't use them also, the JessEm is a flat bottom drill and will remove the stock just like the spiral up router bit..but they are long from 6" to 10" long.
http://www.amazon.com/JessEm-Replac...=1355514476&sr=1-1&keywords=jessem+drill+bits

Does that clear things up now? I hope 

==


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## Jerry Bowen (Jun 25, 2011)

Jofuss 55 said:


> Jerry,
> No router bit made leaves square shoulders.
> A mortising bit has carbide on the bottom of the bit that cuts a flat bottom, as well as sides


Joe,
You have just answered the question that I wanted an answer to when I started this thread. Thank you very much, I'll be contacting Whiteside and ordering a mortising bit after I send this post off to you. Thanks again Joe.

Jerry


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## MAFoElffen (Jun 8, 2012)

Bob- 

Is this what you were talking about? The reuleaux? That is neat...


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## bobj3 (Jan 17, 2006)

Hi

Almost but they have a bit that will cut a true square inside corners, someone did post a youtube of it but I don't recall it off the top of my head..

===



MAFoElffen said:


> Bob-
> 
> Is this what you were talking about? The reuleaux? That is neat...


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## MAFoElffen (Jun 8, 2012)

bobj3 said:


> Hi
> 
> Almost but they have a bit that will cut a true square inside corners, someone did post a youtube of it but I don't recall it off the top of my head..
> 
> ===


Watched that right after I read your previous post:
Drilling Square Holes - YouTube

Watts Brothers Tool Works manufactures and sells those square drill bits based on the reuleaux triangle- Harry Watt square drill bit.


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## OPG3 (Jan 9, 2011)

Jerry, You have a myriad of answers herein. Basically, you can use a mortising bit for use with a router and cut a round hole - with a bottom flute, the bottom can be quite flat. A mortising bit for a dedicated mortiser or a drill press attachment uses four chisels intersecting at 90 degree angles with a clearing bit centrally positioned and very close to tangent with those four chisels - this is called a hollow chisel mortising bit. Another member posted excellent photos of this above.
There is, however; another type of "mortising method" - which your description makes me think you may be referencing: The type of mortises often seen in mission-style furniture. It uses a continuous slot (yes - cut on a router table or using a dado blade on a table saw) and never stops - it simply goes from one end to the other. Tenons the same width as this slot are inserted and filler pieces (flush with the slotted workpiece) are inserted between these "tenons". This method uses rectangular mortises with rectangular tenons and requires nothing other than a slot. This type of mortise and tenon joint is rarely considered "structural", but you quite likely have seen this in a magazine or book or on a do-it-yourself (DIY) TV program. Good Luck, Otis Guillebeau


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## Phil P (Jul 25, 2010)

MAFoElffen said:


> Watched that right after I read your previous post:
> Drilling Square Holes - YouTube
> 
> Watts Brothers Tool Works manufactures and sells those square drill bits based on the reuleaux triangle- Harry Watt square drill bit.


Fascinating stuff, but exactly how applicable this technology is to woodworking I'm less certain. Somehow I can't see it replacing low cost, more generalised and flexible woodworking techniques in a hurry. With a router, for very shallow mortises, the cutter described by Jerry does the job. 

Go deeper and you start to need a more specialised bit like these bits from Amana (shown below, Trend bit):










The staggered tip design allows for good chip removel and a fast rate of plunge/traverse, although they do require a plunge router and the 1/2in and above sizes require 1500 watts or more to get the best from them. Depth of cut is limited to about 70mm (2-3/4in). The big plus to my mind is that they are a lot cheaper than spirals and can be resparpened much more cheaply

If you need to go deeper with a plunge router then you need to start looking at deep pocket cutters line these from Wealden:










They allow mortises up to about 110mm deep (4-1/4in) to be worked and are designed to be used as finishing cutters on jobs such as door lock mortises. They are only ever used in conjunction with a jig such as the Trend Mortise Lock Jig










I use all the above type of kit regularly - although the deep pocket cutters take some planning and need care in use because they are running at the limit of what you can expect a hand router to handle. In this way a hand held router can emulate a horizontal slot mortiser

When tenoning to work with a round-ended mortise, Jerry, it takes just a minute to add a couple of basic (i.e. "crude") chamfers to either end of the tenon so that it will fit the mortise. An alternative is to use loose tenons with a round-end nortise in each piece. Those can be made up by planing stock to fit the mortise and then rounding over the edges so that they look like a Festool Domino using a bull nose cutter (or bead and edge radius) to match the mortise bit:










As to the depth of mortise - no matter what the cutting technique mortises are invariably deeper than the tenon they house (the exception being through mortises) and generally you'll have a shoulder to hide ant less than perfect handiwork, although the M&T fit should be a good sliding fit (not too tight). This means that the bottom of the mortise needn't be absolutely perfect. It's only where mortise bits are being used to sink hardware, such a butt hinges or door hardware that an absolutely flat bottom is required. But in those cases I find an ordinary reasonably large (i.e. 16 to 20mm, or 5/8 to 3/4in) _plunge_ router bit more than suffices

If you really want production quantity mortises at production speeds then you need to get yourself a compressor and one of these - and get yourself some deep pockete because those cutters are hdeously expensive. Makes anything you can do with a router, square chisel mortiser or even a chain mortiser, although the chain mortiser will cut a lot deeper

Regards

Phil


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## bobj3 (Jan 17, 2006)

Hi Phil

I like the
Chain Mortiser it's to bad it's 3000,oo just to put in some holes..

Timberwolf Tools of Freeport, Maine - Mafell LS 103 Chain Mortiser

$2,946.00 +
120 volt motor, without mortise stand, chain, bar or sprocket. 


Phil P said:


> Fascinating stuff, but exactly how applicable this technology is to woodworking I'm less certain. Somehow I can't see it replacing low cost, more generalised and flexible woodworking techniques in a hurry. With a router, for very shallow mortises, the cutter described by Jerry does the job.
> 
> ==
> 
> ...


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## Phil P (Jul 25, 2010)

bobj3 said:


> I like the Chain Mortiser it's to bad it's 3000,oo just to put in some holes..


Well, Bob, Mafell stuff is kind of expensive........ Although there are cheaper alternatives, for example a pal of mine has a Makita chain mortiser for making and repairing field gates, doing oak roof framing and the like. At £880 (circa US $1300) before taxes they are a lot more affordable if a little slower to use

Another nice bit of kit for workshop use is the Alternax mortiser (skip to 1:03 to see the mportiser in action) which unlike the (now defunct) Maka cuts a near perfect shaped mortise using three chisels, two straight and one I-shaped

Regards

Phil


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## Jerry Bowen (Jun 25, 2011)

MAFoElffen said:


> Okay you guys... I know how to do this joining technique and darn it, you are confusing me with those descriptions. I'm sure if you are confusing me, then I feel sorry for those that don't know. So let's see if I can chip through some of this confusion.
> 
> There is a router bit named a "mortising" bit. This is for creating a shallow mortise (a hole or recess cut into a part) for mortising in hinges and such, not for creating a deep mortise for a mortise and tenon joint. This bit is too shallow to create that deep of a hole. Another problem with trying to use that bit for a deep hole is that is doesn't clear the hole of chips fast enough or well..
> 
> ...



Sorry, but I'm more confused than ever.

Jerry


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## Jerry Bowen (Jun 25, 2011)

So far I think that we are talking about two types of morises, first would be a shallow mortise for recessing hinges for example, the second would be deeper mortises for mortise and tendon joints. I want to cut relative small mortises, say ones that are from a half to three quarters deep and a quarter inch wide or so and an inch or so long. I looked at the sqare hold drilling bit but while the hole is square, or sort of square, the corners are still radiused, not square. So, I am still trying to learn what I will have to do to make the mortise and tendon joint the way I envision it.

Jerry


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## jschaben (Jun 21, 2009)

Jerry Bowen said:


> So far I think that we are talking about two types of morises, first would be a shallow mortise for recessing hinges for example, the second would be deeper mortises for mortise and tendon joints. I want to cut relative small mortises, say ones that are from a half to three quarters deep and a quarter inch wide or so and an inch or so long. I looked at the sqare hold drilling bit but while the hole is square, or sort of square, the corners are still radiused, not square. So, I am still trying to learn what I will have to do to make the mortise and tendon joint the way I envision it.
> 
> Jerry


Hi Jerry - you're right, need to figure out what kind of mortise we are talking about. For your particular job, I would just use a 1/4" plunging straight bit or a spiral bit. Round the tenons off with a quick hit of sandapaper. For the 1/8" radius you are dealing with one would be hard pressed to see if its sanded or machined before its assembled.

Usually when you see mortise bits advertised, they will be relatively short cutting lengths and have a fair amount of relief in the center of the bottom. Thats for chip relief on the shallow hinge mortises. They also don't do a very good job of straight plunging nor leave a flat bottom until you move them around a bit.


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## Phil P (Jul 25, 2010)

Jerry Bowen said:


> So far I think that we are talking about two types of morises, first would be a shallow mortise for recessing hinges for example


Hi Jerry

That's probably better referred to as a "recess" rather than a mortise. After all it isn't being used to hold a tenon. Because it's a speed issue with working chippies we often opt for cutters like this one for shallow recesses:










and is sold by Amana although most manufacturers have a few in their line-up. The hollow centre ensures that they clear waste quickly but don't scorch. They aren't suitable for cutting great depths, though. The rounded corners are cleaned out using a sharp chisel, although a square corner chisel speeds the process:










They don't, however, work on deep mortises, especially very small ones



jschaben said:


> They also don't do a very good job of straight plunging nor leave a flat bottom until you move them around a bit.


Agreed



Jerry Bowen said:


> the second would be deeper mortises for mortise and tendon joints. I want to cut relative small mortises, say ones that are from a half to three quarters deep and a quarter inch wide or so and an inch or so long.


In that case you _could_ go down the route of using a spiral bit, preferably an upcut if you don't want scorching (but watch out for "pull-up" on the fibres around the opening), but frankly they are expensive and can be quite fragile if abused in any way. They produce a great surface finish - but who in the world will see it? I tend to stick with ordinary plunge cutters and for speed I have a few single flute cutters:










which were developed for production work on static pin routers before WWII. They plunge very quickly, cut quickly and are very strong - meaning that a 3/4in deep x 1/4in across mortise could be achieved in 2 passes, rather than the 3- to 4- passes of a conventional 2-flute cutter. Downside is that they don't produce the smoothest of surfaces, but it's inside a mortise so it doesn't really matter unless you are going for bare-faced tenons - otherwise the shoulders will hide it. Fauiling those I'd go for a straight 2-flute, buty in the smaller sizes care ins needed to avoid clogging through "over-machining" (where too great a cut is taken for the flutes to clear the waste). For deeper/wider cuts I tend to go for the biggest staggered cut bit I can find (as described earlier) for the same reasons - fast plunge, easy cutting and strength of cutter. Oh, BTW it's a mortise and TE*N*ON, not mortise and ten*d*on. 



Jerry Bowen said:


> I am still trying to learn what I will have to do to make the mortise and tendon joint the way I envision it.


Am I correct to assume that you require a square end to the mortise? If so you'll need to stop the router about 3 to 4mm shy of the marked end of the mortise at each end and finish the cut with an appropriately sized mortise chisel and mallet:










Maybe not an L-N like those above, but possibly something like a Marples Sash Mortise Chisel (*not* a registered mortise chisel which are for coarse work) because mortise chisels have deeper blades and are less likely to twist when being driven with the mallet

Regards

Phil


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## richtink (Dec 5, 2012)

Now, if my hopes are dismissed I have been thinking of using the straight bit and then sanding the area of the tendon into a rounded shape to fit the radiuses left by the straight bit. Where am I going wrong in this endeavor?

Jerry
Colorado City, TX[/QUOTE]
Jerry, just curious why you must have rounded corners on the tenon? You can cut the tenon to go from the radius of one round corner in the mortise to the radius of the other corner. you will not lose any strength of the joint. If you insist on having square corners, then a hollow mortising chisel, of the proper size, in a drill press will probably be your cheapest, quickest, easy way to accomplish that.

Keep in mind, if you use square corners, the location of the tenon will have to be exact. .02" off and it will be evident in the glue up.

Personally, I use the router table for the mortise, then cut the tenon on the table saw, or the router table. The router table is quicker.


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## Drew Eckhardt (Aug 2, 2008)

mgmine said:


> If you don't round off the corners then the tenon won't fit. You can't put a square object into a round hole which is what the corners are. When I use a mortise and tenon joint I cut the tenon on the band saw to fit the mortise size. Also you can't cut the mortise with a straight bit, a straight bit will only cut edges and can't be plunged. You will need to use a spiral bit. IF using it on a table then a downward one, if using it with a plunge router then an upward one.


While standard straight bits won't plunge vertically the web ends before the cutting edges do so you can plunge while moving and cut mortises or any other blind cut you have a template or jig for.

Amana and others also make special straight plunge bits that have edges on the web so they will cut vertically although they don't extract waste like up-shear spirals and don't work as well when not moving.


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## jw2170 (Jan 24, 2008)

Hi Phil, I don,t mean to digress, but I note on the bit you showed that it had a "K" stamped on it.

I remember Ron Fox said that "this was a new bit as it has the "K" mark on it".

What is the significance of the "K" mark.


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## Phil P (Jul 25, 2010)

jw2170 said:


> I note on the bit you showed that it had a "K" stamped on it.
> 
> I remember Ron Fox said that "this was a new bit as it has the "K" mark on it".
> 
> What is the significance of the "K" mark.


Hi James

For a few years now manufacturers in Europe have been putting that "K" mark on to indicate the correct depth to insert the cutter into the collet to ensure safe operation. I find it also helps get you somewhere near if trying to repeat a set-up at a later date. Quite a few of my cutters have them

Regards

Phil


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## mgmine (Jan 16, 2012)

Jerry you want to make a simple 1/4" wide mortise correct? Get this bit from MLCS #5157 1/4" 3/4" 2-1/2" 1/4" $15.95 and make your mortise. Now cut your tenon. If you have a bandsaw then use that if not use your table saw and just make a few cuts with the stock laying flat on the table and nibble the wood away. Now cut a little away from each end about 1/4" to leave a shoulder on the tenon. Now try to put the tenon in, it probably won't fit and you will see why. Now take a rasp and knock down the corners. Put some glue on it and assemble it. Done


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## Jerry Bowen (Jun 25, 2011)

mgmine said:


> Jerry you want to make a simple 1/4" wide mortise correct? Get this bit from MLCS #5157 1/4" 3/4" 2-1/2" 1/4" $15.95 and make your mortise. Now cut your tenon. If you have a bandsaw then use that if not use your table saw and just make a few cuts with the stock laying flat on the table and nibble the wood away. Now cut a little away from each end about 1/4" to leave a shoulder on the tenon. Now try to put the tenon in, it probably won't fit and you will see why. Now take a rasp and knock down the corners. Put some glue on it and assemble it. Done


Art,
Your post makes a lot sense to me that I can and do understand, by the way, I do have a band saw and will cut the tenon on it. Thanks for the post and thanks to everybody else that has attempted to help me with this matter.
I ordered the bit.

Jerry


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