I have a hand-held (not table) router and it came with a parallel guide. Dumb question, but how is it best to use this?
Material to the left, cutter to the right of that, side fence ("parallel guide" - side fence is what most people call them outside of manufacturers manuals)
to the right of that - work by pushing the router
away from you, never pulling towards you. The router is pushed forwards and slightly to the left (easy as the cut will naturally assist) Do NOT use the fence on the left-hand side of the material
as this traps the material and can lead to a climb cut. Going round the outside of a piece you always go anti-clockwise - going round the inside (e.g a mirror or picture frame, using a bearing-guided cutter) you work clockwise - this is so the
"material to the left/cutter to the right and push the tool away from you" rule is always followed
Let's say I am routing the edge off a plank. If I butt the parallel guide against the
opposite edge, then I need to be very sure that I keep it pressed hard against there. If it deviates, I'll be routing into the 'wanted' piece, ruining it. Also, do I have to be particularly careful to avoid climb-cutting in this configuration, as the piece might get dangerously pinched between the cutting bit and the guide?
So I could butt it against the side I'm cutting, then any accidental deviation will cause the router blade to wander away and off onto the 'scrap' piece, which can be corrected by doing another pass. However this destabilises the parallel guide because the trailing side of it is pressing against nothing....it's following a path of an edge that isn't there any more because I just cut it off
The thing about fences is that they invariably have a gap in the middle - but it can be better to take off the bits of plastic on your fence (if it has any) and replace it with a single piece of hardwood or plywood. This needs to be deeper than the cutter so that it forms a single piece sub-fence, and can be much longer than the length of the metal fence if needs be. You may need to position the plywood sub-fence and plunge the cutter into it to form a clearance pocket. Using a long fence like this helps avoid the "jinking" you can experience as the cutter reaches the end of the material
If I'm routing a groove then the same applies - the guide can only fully protect against deviation on one side. The only thing stopping it wandering in the other direction is keeping a good constant pressure on it. Am I missing something?
No, you aren't (missing something). You need to follow the rule I stated above - material to the left, cutter to the right, fence (if any) to the right of the cutter and push the router away from you (NOT towards you). This avoids a climb cut.
The other thing which avoids climb cutting is not making too wide a pass - if you want to cut a 20mm wide rebate, but you only have a 12mm diameter straight cutter, you need to make something like 4 passes, eac h 5mm further in from the edge than the previous. This is so that on an edge cut you never have more than 1/2 of the diameter of the cutter working in the material (i.e. 1/2 of 12mm - 6mm). If you tried to do this cut in two, say, 10mm passes you'd not only potentially overload a smaller router. but you risk a kickback caused by the climb cutting action of the cutter as it exits the material. Incidentally, this is another job a side fence does better than any other technique, and which bearing guided cutters either cannot do at all or are have very limited capability in
It is possible to set-up grooving in some circumstances (on narrower material) with two fences and longer fence rods, but I've rarely ever needed to do this. One example, though, used to be cutting 15 or 20mm intumescent strip grooves in the edges of 44mm thick fire doors where two fences, longer fence rods and a single deep plywood sub fence made for a faster and less error-prone job out on site in the days before a specialised intumescent strip groove cutter became available.
I still use the same sort of technique when I have to groove-out the bottom edges of doors to accept drop seals, in which case the door is rested on a pair of trestles and a large plywood sub fence is needed on the upper parallel guide (the 1/2in router is used on its' side and the plywood sub-fence is needed to help support the weight
I don't use routers that often but when I did I had the same problems you are having. Ruined 2 worktop jigs in the process
You were using a worktop jig with a side fence?
People sometimes ruin them by pulling the router out of the jig without first unplunging the cutter (and locking the plunge mechanism), switching off and letting the cutter stop first. I don't do this most of the time (I just unplunge), but if a piece is critical or I don't have much material to spare I do become ultra cautious. I also stopped loaning jigs to people a very long time back because of the way they get abused
The other common mistake is to do with direction of cut. You always need to cut into the laminate, so this means right hand end male/right hand end vfemale cuts are done with the jig on the top face, left hand end male/left hand end female cuts are done from the bottom face, and the cut depth is increased over 3 or 4 passes
with the router alwsys being pushed away from your body. The other thing people are iften unaware of is that on many jigs the groove that the 30mm guide bush runs in is actually deliberately oversize - this is partly so that you can make your 3 or 4 stepped depth cuts
with the guide bush deliberately pulled over to run against the right hsnd side of the groove and the final, full depth pass of a fraction of a millimetre being made with the guide bush run against the left side of the groove. Gives a cleaner edge and a better joint fit
Sorry for the long post, but there were a lot of points
