How well-fixtured do I need to be for this router bit cut?

[Gene Davis]

Not yet arrived is one MCLS bit, 1/2" shank, countersink screw slot. See the pic below.

I have cherry tops to cut with this bit. My router of choice is a plunger, a Porter Cable 690, and I have the PC edge guide for it.

There is a YouTube video in which a guy shows it in use, he's cutting freehand, making one through plunge in 3/4" stock, looks like pine, and he's doing the little 1/4" long cut, which is what I want to do. My cherry will move with the seasons, but not much.

So I am wondering, in advance of getting the bit, whether my 1.75 HP plunger with its edge guide is all I need to have to make these cuts, or do I need to fixture up for more control?

Anybody out there with experience with this kind of bit in hardwood?

[Greg Hines, MD]

If you are worried about it wandering, make a jig, to use with a guide template, as long as the slot you want, then clamp it down over the area. I would think your router has plenty of power for it.

Doc

[Keith Weber]

Gene,

You'll be fine with the 1.75 hp router. If you go in free-hand with an edge guide, though, you'll need to pay attention to the direction you feed in. If you go in the wrong way, the cutting action of the bit can pull the edge guide away from the edge and you'll get a curved cut. I learned that lesson the hard way about 15 years ago. Feed direction is depicted in the following diagram (the lower one) by WoodMagazine. Edge guide on the right, or straight-edge clamped to the work piece on the left:

333499

Interesting photo in your post. It shows the grain in the wrong direction. The expansion will be across the grain (not along it), so you should orient your slot so that the expansion will allow the screw to move in the slot with changes in humidity.

[John Donhowe]

It's hard for me to tell from the picture, but it looks like the long thin part of the bit- that cuts the screw shank opening- is pure carbide (no steel backing). If so, it could be brittle and prone to snapping off, especially with lateral (sideways) force. It might be wise to make several cuts, increasing the depth with each pass.

[Tom M King]

I'd use the plunge router, and a guide. That bit breaks pretty easily. I bought one because I had just one use for it, and it was cheap. It was the only bit I've ever bought from that company. It's been long enough ago that I don't even remember what I needed it for, but I broke it fairly quickly, and I'm not exactly an inexperienced user.

[Gene Davis]

Here is the YouTube video showing the use of a bit like this. Note that he is using a softwood for the demo, and that he plunges through in one dive.

https://www.youtube.com/watch?v=RRiEX3r3VdE

[Gene Davis]

Thanks for the detail about cut direction when using an edge guide.

Alternatively, I am thinking of making a template to use with a brass guide. See the pic attached. My idea is to cut down the length of a template guide so it will work with some 6mm baltic birch I have. With a plywood template, I can cut without the bit wandering, and can plunge in steps.

[John TenEyck]

I think the photo is correct. That part is likely a stretcher that sits below and cross grain to the top.

John

[Keith Outten]

If your worried about the bit breaking you can cut the slot with a straight bit first then use the screw slot cutter. I do this all the time with keyhole bits if the wood is extremely hard.
.

[Keith Weber]

I think the photo is correct. That part is likely a stretcher that sits below and cross grain to the top.

In the photo, the wood that the screw threads would be the "top". Its grain is running parallel to the slot -- the wrong direction for expansion, so I'll have to respectfully disagree with you on the photo being correct. The slot is accomplishing nothing in the photo.

[Gene Davis]

Here is a pic of what I want to do. The top of a 6'-3" tall etagere will be screwed to the frame on which it sits. I did not show the front row of screw holes, which are not elongated.

[Prashun Patel]

I tried using that very same bit from MLCS. It snapped on me during the first operation.

Lesson learned:

Cut in shallow passes
or
Buy a better bit.

As for guiding the bit, your slots don't have to be that long or that neat. An edge guide will be fine.

(edit):
I made a mistake: the bit I had was a KEYHOLE bit - not a screw slot bit. I could NOT cut in a single pass.
I would still cut yours in shallow passes. The skinny bits I've used from MLCS have tended to break. This has happened with my Keyhole bit, and a 3/8" dovetail bit. You just can't push them hard.

[Charles Taylor]

Not yet arrived is one MCLS bit, 1/2" shank, countersink screw slot. See the pic below.

I have cherry tops to cut with this bit. My router of choice is a plunger, a Porter Cable 690, and I have the PC edge guide for it.

There is a YouTube video in which a guy shows it in use, he's cutting freehand, making one through plunge in 3/4" stock, looks like pine, and he's doing the little 1/4" long cut, which is what I want to do. My cherry will move with the seasons, but not much.

So I am wondering, in advance of getting the bit, whether my 1.75 HP plunger with its edge guide is all I need to have to make these cuts, or do I need to fixture up for more control?

Anybody out there with experience with this kind of bit in hardwood?


I've used Infinity's version of that bit in SYP, so not exactly hardwood. Used a 2HP plunge router and edge guide, if memory serves, with no problems. I'd use Prashun's experience as a warning to go slow and not push the bit too hard.

[Tom M King]

I remembered what I bought that bit for. I was going to put some reinforcement strips of very old, air dried White Oak under some of the wide treads in winding stairs in an early 19th Century house that had split, and were on too wide a span anyway. The bit lasted about as long as Prashun's did. I had been used to Whiteside bits for a few decades. I ended up doing the job with some bits I already had, and as soon as those catalogs come, they get tossed in the trash.

[Gene Davis]

Well, the bit arrived and I tried it out on scrap pieces. Used both aids, a template I made and an edge guide. The template won.

My travel for the slots was only 1/4" so I found it best to place the router at one end of the template hole and plunge straight through, then pull up and out, vacuum the chips and dust, then plunge through with the router at the far end, then push the 1/4" to join the two holes. All turned out well.

The pull up and out then vac operation is needed because the chips and dust have nowhere to go but up, and if not cleaned out, the template guide does not have a clean ride to the other end of the slot. It jams up against a wall of chips without going the full 1/4" of travel.

Things were different with the simple edge guide thing, but I could not get placement as precise as with the template.

The bit was $17 and change, delivered, and was used to cut 35 holes. Not too bad a deal, and since the bit did not break, it can be used again in future.

[paul cottingham]

I used mine with a router table. Worked fine, but I don't miss it. Now I use a drill and drill bit for that kind of stuff.

[Jim Dwight]

I'm glad it worked out well for you. MLCS is where I often buy router bits. I have several sets of cope and stick and panel raising bits from them and many others. I don't buy bits like this from them, however, because of negative experience with other inexpensive suppliers. Maybe I should give them a try. On bits with a significant neck down like this, I think the less expensive suppliers have a problem with the heat treatment making the bits brittle. But MLCS may be an exception. The last somewhat similar bit I bought, a dovetail bit for half blind dovetails, was a CMT. I snapped a cheaper one without accomplishing anything (not even one joint). But it wasn't a MLCS. The CMT has done many drawers and still working well. I would expect the same of a Whiteside.