router newbie, question about router bit wanting to wander
i was routing 3 five inch slots in HDPE. the slots are 3/4″ wide, and i was using a 1/2″ straight cutting router bit. i was using a clamped guide, and running the router against the guide surface. the slots required 2 passes, and i had to move guide for second cut. first and second slot cuts went fine. on 3rd, the first cut went fine, but when i went back to finish the 2nd cut which only was taking about 1/4″, the router jumped ahead, and away from the guide.
Any ideas why this was happening?
it started to do this again, on 2nd try, so i stopped and put another guide in, to hold the router in place from both sides. this worked.
this is the first time i have worked with HDPE. the first router cuts went very well, just like wood. i was wondering if maybe i needed to increase speed of router for the hdpe ?
thx in advance
greg
Replies
Routing is the weakest part of my game by far (relative newbie), so wait for the experienced folk to reply, but it sounds like you’re climbing (routing in “wrong” direction).
I was just watching this series, check it out. He mentions climbing on grooves requiring a reset fence in episode 2 or 3:
https://www.finewoodworking.com/videoworkshop/2018/09/router-table-fundamentals-bob-van-dyke
Was the cut made with the rotation of the cutter against the direction of the router or was it pulling ? When routing ''downhill'' the cutting action will pull the router in the direction of the cut and it will be hard to control, its easier to cut ''uphill'' .
Plastic can soften and get grippy as you get deeper and "chips" become mush inside the slot. An upcut spiral bit instead of a straight bit might help.
thx guys,
i moved the router in the direction of the bit spin. the router has an arrow which shows this. this might be 'downhill' as gulfstar mentions. so, it is ok to push router in the opposite direction??
the plastic chips did not seem to be hot, or soft. and the material did not heat up.
i didnt have enough extra material to do trial cuts, but i may no have encountered problems as the first few cuts worked great.
i am real careful with the router. just purchased the smaller makita, for smaller projects, like what i was doing. would prefer a table, but these slots were in a big sheet, and not good candidates for table mtd router.
You were performing what is know as climb cutting. In climb cutting the router bit tends to want to pull itself into the stock and can be hard to control as you found out. Climb cutting is used at times because it reduces tearout leaving a smoother cut, but I'd recommend you getting more experience with a router before attempting it. Also when cutting against a fence or guide it is preferable to cut against the rotation since this has the effect of pulling the router into the guide instead of pushing it away as you discovered.
thx 59
your explanation makes sense to my newbie brain, and experience level.
i really appreciate the feedback from this forum, which i have used a couple times. unfortunately, i cant help most people, as my skilz are.... limited. :)
thanks very much
goinoregon, greg
Your day will come when you can pay it forward, just keep building and learning. Always try to incorporate at least one new technique and or joint on every project this will help you build your skills faster. Also remember most things in Woodworking can be done multiple ways; there must be a dozen different ways to cut a mortise and tenon joint so don't be afraid to try different things until you find one that works best for you.
This brings back to original post. A better way to have cut the slots would have been to have made a simple template to begin with. Two boards wide enough to support your router separated by ¾" spacers and a top bearing pattern bit is how I would have approached it. The advantages are many.
Repeatability - every slot would be exactly the same since the same template would be used
Accuracy - your method had you measure twice introducing twice the opportunity for error, alway try to reduce measuring as much as possible.
Speed- if you only need to set up once you can complete the process in half the time
Remove the element of luck-if you had used a double edge template to begin your issue would have been of no concern the router would simply have hit the other wall of the template no harm done.
thx for your very informative reply. i figured, since i was only doing 3 slots, a guide on one side would suffice.... and i was not overly concerned about the exact size of the slot, as this was not going to be furniture quality. that said, i have enough trim material to make a template, and will go that route in the future.
i am putting the hdpe on a 1930's basement table, that has a site built cabinet on top of it. replacing antique linoleum, or whatever it was. this will adjoin a new sink framing that i will build with 80/20, with hdpe on top. cleaning up this part of basement/shop. no more routing for awhile as i move into cutting alum. extrusion with miter saw with new blade.
thx again. go
I think the answer has already been given correctly, however I will share one other problem that a newer router user will perhaps value -
Bits that are long in relation to the shank diameter are prone to wobble, even if they are perfectly balanced.
This caused me endless strife until I realised the problem. Buying a 2 inch bit because you can't cut a deep hole with a shallow bit was not a good economy, even though I have of course since found a use for it...
Longer bits are less tolerant of deeper cuts than a shorter bit and will tend to vibrate, causing uneven cutting or in extreme cases causing similar problems to those described.
The 'rule of thumb' not to make a cut deeper than the diameter of the bit or shank can be misleading. That is the absolute maximum safe cutting depth, not the ideal.
This means that it is better to use a shorter bit for shallow cuts.
Rob,
What you say is right but there are times when a long bit needs to be used with it's whole vertical edge cutting. The obvious examples are profile bits, some of which can be 2 inches long (perhaps even longer) in their "knives". The same is the case when a long straight bit is used to cut the cheeks of a long tenon, for example.
In such cases, the quality of both the router and the bit used are important, as both can produce the sort of run-out or wobble you describe, if their quality is poor, leading to vibration and ragged or even dangerous cuts.
It helps to mitigate against less-than-perfect routers and bits if they can be used strapped to something that prevents the router jumping about, such as a router table or a woodrat. With appropriate hold-downs, fences and other workpiece controllers that join with the router-controller (table, woodrat etc,) climb-cutting also becomes much safer and therefore possible.
It's still unwise to take great big bites of any sort, mind. With the 3 hp routers typically used in a table or similar big jig, that amount of power can wrench at even the most firmly clasped router or workpiece if an unwise operation is performed. But such jigging does allow far more cutting operation types than is possible with a hand-held router.
Still, high quality routers and bits can also widen the envelope of possible cutting operations when the router is used hand-held or guided by simpler jigs such as that used by the OP. This is especially true of lower-powered routers, which are often a better choice than a great, heavy and powerful beast, no matter how high quality it is.
Lataxe
:-) My issue occurred with a 2 inch whiteside spiral upcut and a triton router - I think it was user error!
What surprised me was how small a cut was needed to avoid the wobble.
Climb cutting. If you are making multiple passes to widen the slot, the first pass will be fine. But subsequent passes would either need to switch the guide to the other side of the slot, or change direction of the router -- away instead of towards, or left instead of right, etc.
Taking a really light pass with the router going in the wrong direction should be avoided, but isn't too big a deal. Trying to take a heavy cut will really cause the bit to grab and jump, and is very dangerous.
I think the main issue was the material. Sometimes a guide collet works better than a bearing bit - planet of down pressure!
IME it’s better/safer to use a slotted (two sided) guide rather than a straight edge as esch mentioned.
Climb cutting is normally a bad thing, but can actually be used to clean up a cut - but only very shallow passes and very controlled situations.
A more powerful router can do a better job but there can be a temptation to take too big a bite.
Totally agree - the jig will also prevent the bit from wandering outside the desired area.
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