Best hole cutter/trepanning tool?

[ian maybury]

Would appreciate your advice on some good choices for an adjustable tool or method for cutting holes in the size range between a large Forstner and using the circle jig on the router - mostly in ply, but possibly also in thinnish (maybe up to 3/4in or so) solid wood.

I've seen tools on the web for use in a drill press with an adjustable arm with a cutter at the tip mounted in a shank which has a centering drill, but never handled or used one and suspect the quality of some isn't great.

Whatever the solution it should (at least when properly sharpened and used carefully) be capable of cutting a clean hole, staying in adjustment, not blunting in a moment etc etc.

Hole saws are far too rough, large Forstners may be an option but they are fixed size.

Thoughts?

Thanks

ian

[Van Huskey]

The most reasonable for what you plan to do is a circle cutter like what you describe in the second paragraph. One that has been well reviewed is the one Lee Valley sales. I have never used one since I have never had need for a hole between the router jig and my largest forstner which is 4".

[pat warner]

Adjustables always cut with compromise. However, if one is a master sharpener one can cut precisely and with max cleanliness.
Notwithstanding, the best holes in wood or ply (fixed D) are done with 3 wing carbide.
Top left (http://patwarner.com/images/drilling_tools.jpg), example. Not cheap but the Chinese are getting better and you might luck out with an inexpensive import.
Typical max D in 3 wing = 3".

[ian maybury]

Thanks guys. I've ordered the Lee Valley item as it looks rather more solid than those I've seen locally. Thank you both.

ian

[johnny means]

I have the non Lee Valley branded version of the Lee Valley tool. It does what it was designed to do, but in a very crude manner. I had to totally reshape and sharpen the cutter in order to prevent burning. Set up can be tedious and test cuts are absolutely necessary if precision is important. Though it can be very precise.

Be very careful where your hands are when using it. When it is used it becomes a miniature mace, seeking to destroy any unsuspecting knuckle which might wander into its territory.

I use mine to cut holes for a specific LED light that comes in a very odd size. I wouldn't use it for a hole that needed to look nice.

[Larry Edgerton]

A fly cutter is what you are looking for and I disagree with whoever said that they do not make a good cut.

Just like any other tool there are good and bad. I first bought a cheap one and was not happy, but then bought one from a machine supply house and it does an awesome job. I use mine occasionally and it is heavy enough that I can use it without the center guide when need be in a heavy drill press when I need a quick plug of a large size. This is something a forstner bit can not do. It has a scale on the beam that is accurate which helps with setup although the scale is for the outside radius, so 1/4" needs to be added for a plug.

As Johnny said, BE AWARE! You have a hard time seeing exactly where it is when it is spinning and you need to have the piece clamped to the table. NO HAND HOLDING OF STOCK! This tool will mess up your day if you do not do things correctly.

Overall a seldom used but handy tool to add to your collection for not much money.

BUT BE CAREFUL!

Larry

[Joe Kieve]

+1 on Larry's comments. He's spot on about clamping the workpiece down. Don't even think about holding with your hand. Talk about a "knuckle buster".....DAMHIK.

Joe

[Bill White]

A well sharpened fly cutter run at the correct speed will do a good job. I cut until the center drill breaks thru the bottom side, then flip the workpiece over to finish the cut from the other side using the center hole as a guide.
Bill

[ian maybury]

Thanks for the steer on grinding guys, and the care warning. I've some background as a machinist, and know about the need for clearance angles and so on on cutting tools. You can see that this format of cutter would need plenty on the outside face, and probably right along the length of the cutter to prevent burning.

Just so I've got it right - when you say 'fly cutter' do you mean the Lee Valley type tool? http://www.leevalley.com/US/wood/page.aspx?p=32275&cat=1,180,42316&ap=1 There's another variety like this used a bit for facing metal surfaces (see right at the bottom of the page): http://www.micro-machine-shop.com/end_mills_cutters.htm

ps I went for the LV item Pat as adjustability is more important to me in this case (boring holes for duct entries in birch ply) than ultimate precision. Agree 100% that a solid cutter has to be a lot more predictable. Hopefully it'll with care do the job.

ian

[Van Huskey]

I often hear the circle cutter we are all, I think, talking about called a fly cutter, in fact I typed it initially but changed the wording as not to confuse you with the metal working cutter which is more universally known as a fly cutter. Just keep it sharp and you will be fine, there are a LOT of junky ones out there but based on feedback and reputation the one Lee Valley sales is probably very good as they go.


Thanks for the steer on grinding guys, and the care warning. I've some background as a machinist, and know about the need for clearance angles and so on on cutting tools. You can see that this format of cutter would need plenty on the outside face, and probably right along the length of the cutter to prevent burning.

Just so I've got it right - when you say 'fly cutter' do you mean the Lee Valley type tool? http://www.leevalley.com/US/wood/page.aspx?p=32275&cat=1,180,42316&ap=1 There's another variety like this used a bit for facing metal surfaces (see right at the bottom of the page): http://www.micro-machine-shop.com/end_mills_cutters.htm

ps I went for the LV item Pat as adjustability is more important to me in this case (boring holes for duct entries in birch ply) than ultimate precision. Agree 100% that a solid cutter has to be a lot more predictable. Hopefully it'll with care do the job.

ian

[glenn bradley]

I use the Lee Valley version which is like (or is) the General unit you can get at most BORGs. I the jig pictured (idea taken from some mag and rendered out of a chunk of 2x4 that was lying nearby) and can setup first time more often than not. I run at about 250RPM and take my time. No burning issues unless I get impatient and overrun the cutter (note black residue on cutter :o). I imagine the cutter geometry could be improved to increase speed but then one would have to maintain that geometry; its a trade off and only you can decide the amount of that you want to do. I have been using the same cutter for years with only a mild touch up with diamond stick. I also cleaned up the grub screw marks and shaped the tip of the grub screw so as not to dig in. You may want o address the tip of your screw before use and save yourself the clean up later.

[Eric DeSilva]

Wait. I thought trepanning was drilling a hole in someone's skull?

[ian maybury]

It sure is Eric, but for some reason this type of hole cutter is occasionally referred to by that name too.

Thanks Van, Glenn - sounds like we're under way.

On which subject. Nothing to do with LV I'm sure (who in my experience are a great company to deal with), but what in heaven is going on with the US international postal service?

*Surface Mail 8-12 Weeks $8.95
*Air Mail 2-4 Weeks $17.06
*Xpresspost 8-10 Business Days $56.63
*UPS Express 5-6 Days to Major Centers $28.91

How can mail cost more than a courier delivery? More to the point, if the Air mail service is taking 2- 4wks then they must have one pretty ginormous warehouse full of in transit stuff somewhere. Even Xpress seems slow, never mind how it can cost more than a courier service????

Sounds like one our Irish ex state monopolies - a sort of an unholy combination of free enterprise 'screw the punter for what you think you might get away with' pricing combined with the normal public waste, excessive salaries, out of control costs, lousy management and mind boggling inefficiency. The sort of thing the politicians look the other way from because it involves taking on a powerful vested interest and can't be fixed with a sound bite.....

ian

[ian maybury]

Just to say guys that I have received and tested the Lee valley circle/fly cutter.

It's not a bad tool at all, and with a bit of tuning and sensitive use cuts a very nice hole in birch ply of quality comparable to what you would get with a good Forstner bit. It's probably not the sort of thing you would buy if you needed a lot of holes the same size, but is probably a decent 'get you out of a hole' (or into...) fix for one offs in odd sizes.

Probably not intentional as it looks like it's meant to, but as delivered the tool is ground so that it's not quite capable of making it through 3/4in - the rake/clearance angles need extending up the cutter a little further. The tip of the cutter needed a bit of a clean up to get rid of a burr, but it's decent piece of what's probably a hardened carbon steel.

There's a few improvements that are possible e.g. a hex shank to make life easier for a drill chuck, but nothing that's a show stopper.

ian