Plunge routing for the first time - How deep? How fast?

[Dave Friedlund]

Hi,
I'm making a walnut cabinet for a vintage stereo receiver. The cabinet will have 6 ventilation slots. Each one will be 3/16" wide by about 4 inches long. I've made a template and plan to use a 3/4" bushing and a 3/16" down cut spiral carbide bit. This will be my first time doing plunge routing. I plan to practice several times on scrap. Here are my questions:

1. The cabinet is 1/2" thick. Show I plunge the entire 1/2" and make one pass or make multiple shallower passes?
2. My router is variable speed. Should I go full speed or dial it down?

Thanks!

Here's a sample of what I need to reproduce.

473972

[Michael Schuch]

I would probably go full speed and maybe break it up into 2 passes for safety sake unless your test cuts show you otherwise. One pass should not be a problem though.

A router can be very intimidating the first time you use it. It won't take you too long to get comfortable with it. I would highly recommend hearing protection!

What are you building the cabinet for?... what type of stereo gear?

[Curt Harms]

I wouldn't do it in one pass unless you like buying carbide spiral router bits. The back of my brain - the part with the cobwebs - says don't route deeper in one pass than the diameter of the bit. So 3/16" bit = 3/16" depth of cut which seems reasonable. If I were using a 3/4" bit I don't think I'd cut 3/4" deep in one pass though so I would not regard that rule of thumb as absolute.

[Ron Selzer]

Full speed due to how small the bit is
2 or 3 passes, maybe but probably not 4 passes, depending on how the trial passes go.
Test passes will really set you up with what is needed

[glenn bradley]

I pretty much apply the rules of thumb for any router operation. Speed to match bit profile or diameter, take no more than 3/8" by 3/8" area at a pass, and use a very light last-pass for complex profiles or burn-prone material. I do this on fixed, plunge or table routing.

[Dave Friedlund]

Thanks for the replies. What style of router bit would you use. I want the cleanest cut on the top of the cabinet but don't care too much about the bottom. Would you use a downcut spiral bit on the top. OR use an upcut spiral bit but start at the bottom. (is there a difference?) Or just a standard 2 flute bit.

[Myles Moran]

I think the downcut would be a good choice. You might need to blow out chips between passes with a compressor though. I'd also do at least the first pass at 1/8" deep. Maybe deeper for subsequent passes depending how the bit likes it, but less deep cuts will give you a better cut quality since your forces on the bit will be lower (and a bit that size will sure want to vibrate and/or chatter if you try and push it too hard)

[Zachary Hoyt]

I rout a 1/4" x 3/8" deep slot or a 7/32" x 7/16" deep slot in a single pass when installing truss rods in banjo necks made from walnut, curly red maple, African mahogany, cherry, ash, etc. I leave the router at full speed and it seems to do fine. I've done this hundreds of times and the only problem I have had was once when the bit walked up out of the collet as I was routing, because I didn't have it tight enough. I rout with a fence and have found that it's important which way I feed the router into the cut, as it will pull the router to the fence one way, and push it away from the fence the other way. Pulling into the fence is much better, the other way leaves a very wavy ugly cut. With the fence between me and the router I always feed from right to left.

[Prashun Patel]

Use a spiral bit. Downcut will be marginally better here.

I would do multiple passes. Most plunge routers have a spinning depth stop for this reason. Going shallow (1/8-1/4) passes will help with control and burning if you do not have a fully captured jig.

One caveat with multiple passes: There has to be no slop in your jig. Or else you may get a slight shoulder.

Because you have multiple flutes to do, I would certainly make a test piece and practice your regimen. Try it with one pass and with multiple passes.

[Ken Kortge]

A rule of thumb that I've seen: Set the depth of cut for each pass to no greater than the diameter (width) of the router bit. Some suggest setting the depth at increments of 1/2 the diameter.

[Robert Engel]

For an absolute perfect line score I score with a knife first. Understand cutting with the length usually one side of the bit is cutting against the grain.

Personally I avoid bushings. I much prefer a flush cutting pattern bit. That way I can line up the edge of the jig with the exact knife line I've made and it greatly reduces error, which I'm very prone to!!

[Alan Schwabacher]

There are several things to consider.
Speed: This depends on the bit diameter because at the same rpm the cutting edge is going further and faster with a larger but. Up to 1/2" use full speed.

Power: Pat Warner, who is now gone but once answered questions here as Router man (and authored several books on the subject) said that the maximum amount of wood you should remove in a single pass is the equivalent of 3/8" x 3/8". That would mean a 3/4" wide pass would be 3/16" deep. A shaper with more power can take a bigger bite, and a big router may be able to as well, but you can get good results and keep control of a hand-held router best if you stick to this rule.

Force: If you push too hard sideways on the bit it can break, and while spinning at 25,000 rpm, that can be dangerous. That's the reason it's not advised to cut deeper than the bit thickness. But this is an upper limit, not a recommendation, particularly with big bits.

[Warren Lake]

Never paid attention to any rules. You have feel and ears, run taking a light cut maybe 1/16" and increase it. Cutting in one shot forget it. There are choices on bits depending on the dimensions, two flute straight plunge bits single flute plunge bits and spirals., Up cuts are better for you depending on your template as you would be better off pulling some chips out as you go. Did lots of that and used compressed air to blow stuff out as I went along. It will go all over, I never cared just get the work done.

[Jim Becker]

Downcut is going to give you the greatest chance of a clean entry from the "Money Side" of the workpiece. But you definitely want multiple passes, both to reduce the chance of breaking something as well as because a down-spiral tool is going to push the chips into the slot(s) rather than eject them. You'll want to clean the slot(s) out between passes to keep things clean and not generate excess heat.

[Dennis Jarchow]

One small point, if that wood is veneered, I would not use an upcut spiral. A down shear bit is a cheaper alternative to a downcut spiral when the surface is veneered.

[Richard Coers]

I hate down cut spirals when the bit doesn't go all the way through. I've read about people starting fires in MDF while packing in the sawdust at the bottom of the cut. Unless you throw the router around the work, or use a dead dull bit, uncut has done well for me since they invented them. That's right, I started woodworking before spiral solid carbide bits were invented. What did everyone do before downcut was invented, if that is the only bit to use?

[Warren Lake]

we used straight flutes before spirals and they are fine for this single or double., I was in a furniture factory one afternoon and all hell broke loose. I had just walked outside standing beside a massive dust collector and inside a CNC machine had stuck and started a fire and made it to the dust collector safety. Lady lost her job. I have tons of router bits but not sure if I have even one down cut.

[Jim Braun]

That's right, I started woodworking before spiral solid carbide bits were invented. What did everyone do before downcut was invented, if that is the only bit to use?

:rolleyes:

474058

[Warren Lake]

what is that thing, did they find it in an Egyptian Tomb? Likely never start a fire with it though unless you had been drinking a lot of coffee.

[Dave Friedlund]

Thanks everyone for the great advise. I used a down sprial bit and made about 4 passes with my plunge router. I'm very happy with the results.

https://www.dropbox.com/s/5mq3jdw2nr21irf/P1090962.jpg?raw=1

[Mike Henderson]

Looks great. Congratulations!

Mike

[Warren Lake]

What does your jig look like?