screw slot bit

[LCHIEN]

I got one of these the other day from MLCS.

http://www.mlcswoodworking.com/shops...screw_slot.htm



I thought they would be good for jigs and stuff that needs to be adjustable.

Anyone else use them, got any ideas or suggestions for use?

seems to work OK - here's my first (actually second) attempt:

I guess my one complaint is that the bit cutting height is only barely 3/4" - it's hard to cut a through slot on 1-by material. I had to flip it over and use the tip to clean up the bottom of the hole. I could have routed the slot deeper, but I felt the countersink part was already plenty deep.

[fredg50]

I have that set. I bought it to attach a glued up panel to the top of a pie safe I was making. The first time I used the one for pan head screws the tip broke off. I was using it in poplar. There were no instructions so I called MLCS and they said you should be able to make the cut in one pass which is what I tried to do. Were you able to make the cut in one pass and did you use it in the table or hand held router? I used it in the router table. I dropped the work piece on the bit which plunged in fine but I had a hard time moving the piece to cut the slot. After about a inch of travel the tip broke off and went flying across the table. MLCS replaced the bit no problem. I still don't know if I did something wrong or the bit was defective.

[RodKirby]

Just ordered them - I'll let you know...

FWIW - I would always use 2-3 passes with this kind of bit - no matter what the supplier says.

[LCHIEN]

I took at least three passes, four would have been better...
1st pass about .25" to 3/8" of the tip only.
2nd pass the contersink just engaging a bit.
3rd pass the whole countersink in
4th pass the countersink to desired depth (in my case the tip just peeking out the other side)
5th pass, lower the bit so the tip is just out 1/4" and flip the workpiece over to clean up the exit side.

I would not take 1 pass, that tip is pretty small and in profile from one direction very thin, much thinner than the dia.

And i did it in a table. I really had to use a good bit of force to hold the fence, the sideways action of the bit crosswise to the direction of feed wanted to drive the fence off and screwed up my first attempt.

[poolhound]

Looks like an interesting bit but am I missing something, couldnt you do the same thing with two bits? Admitedly that needs a bit change but given the discussion on multiple passes I am not sure I see the benefit.

[LarryG]

couldnt you do the same thing with two bits?

You can, and I have; but it's fussy. Or perhaps I should say, it can be fussy.

I typically make cuts like this on the router table. My router is in a lift; all bit changes are done (and must be done) above the table. A narrow workpiece such as Loring pictures requires the router table fence to be positioned atop the removable insert in the lift's plate, which means you can't remove the insert to change bits without moving the fence ... so you make the cut with the first bit, carefully mark the position of the fence before you move it out of the way, remove the insert, crank the lift up so you can get to the collet, make the bit change, crank the lift back down, replace the insert, put the fence back where it was (at least in theory), reset the bit height ... urgh. It doesn't take long before the price of a special-purpose bit such as this starts looking really cheap, even if you only use it a couple times a year.

[LCHIEN]

Larry's points are right - you'd have to change bits, and make multiple passes with each bit - more passes total. With the purpose made bit registration of countersink to center is perfect, changing bits would almost require moving the fence so registration could be a problem (both width and end stop points would move when the fence was removed and replaced). Also if using the flat head countersink, finding a proper bit for that might be hard, I don't know of one offhand that will make a slotted beveled slot of the correct width required.

[poolhound]

Good points about having to move the fence, that was something I hadnt considered. Although for most non-critcal screw slot positioning if the two slots are a hair off in terms of center alignment it wont matter much.

I do agree with you Larry, that if you have to do a bunch of these types of cuts on a regular basis a special bit like this has distinct benefits.

[cgallery]

require moving the fence so registration could be a problem (both width and end stop points would move when the fence was removed and replaced).

I use my BT3K fence for my router extension and have made a little stop for the front rail (clamps with a machine screw into a t-nut). It registers off the front block of the fence and allows repeatable registration at the mid-point of the fence of better than .002". And the front block provides perfect registration for any stop blocks attached to the fence itself.

Of course, this doesn't help anyone that uses a purpose-built fence for their router.

[poolhound]

I use my BT3K fence for my router extension and have made a little stop for the front rail (clamps with a machine screw into a t-nut). It registers off the front block of the fence and allows repeatable registration at the mid-point of the fence of better than .002". And the front block provides perfect registration for any stop blocks attached to the fence itself.

Of course, this doesn't help anyone that uses a purpose-built fence for their router.

IIRC Rod Kirby (it may have been someopdy else as I cant find it) had a post about a jig that could be used for any router fence to do this exact thing.

[Tom Miller]

Seems like I'm frequently making such profiles, but usually for 1/4" or 5/16" bolts.

Re: router fence registration. My current homemade router fence rides the rails of my BT3, and registers parallel to them much like the BT3 fence does. I didn't exactly do this with 100% forethought, but it gives me the same benefit cgallery mentioned, in addition to microadjustment with same adjuster that I use for my BT3 fence.

Regards,
Tom
Added: Hmmm, wonder if you could make a 1/2" shank cutter with a 1/4" bore, then slip a 1/4" shank cutter through that with a set screw to hold it. Then, you could combine a 1/4" or smaller cutter with the shoulder cut made by the 1/2" cutter.

[LCHIEN]

I would guess partly for the same reasons you have collets and not a set screw holding the 1/4" shank router bits... namely concentricity and holding power. These 2 HP routers spinning bits at 23,000 RPM are fussy. they won't like the few mils of slop required to admit a fixed shank bit and then tighten a small set screw to hold it against 2 HP and spin smoothly and securely.