Router Forums banner

Router Bit Recommendation

1612 Views 15 Replies 13 Participants Last post by  bob vaughan
I'm looking to cut lots of 3/4" holes through 1/2" plywood, and want the holes to be as smooth and clean as possible. I think I need a spiral bit, correct? Should it be up spiral, down spiral, or compression spiral? My router can handle 1/4" and 1/2" bits. Can someone recommend a brand? Having a hard time finding any that'll do the job at Home Depot, Lowes, and Lee Valley tools.
1 - 16 of 16 Posts
Welcome to the forum, Pete! I'd use a 3/4" Forstner bit. How many holes are you cutting?
  • Like
Reactions: 2
Welcome to the forum @Pete Campbell
Welcome to the forum. If you do find a 3/4" router cutter, I would make it a spiral downcut for the cleanest surface finish.

Otherwise, use a forstner cutter as suggested by David.
  • Like
Reactions: 1
Welcome, Pete.
What size is the project? what are you making? how far apart are the holes? If it is possible, clamping a "backer board" behind the hole would help elimate tear-out splinters. More info, sketch, drawing, or sample photo would help.
  • Like
Reactions: 4
Maybe a 1/2 solid carbide spiral bit, a guide, and a template to position the holes. Plunge the 1/2 bit into the plywood then cut the sides to get the clean cut on the plywood at 3/4 inch.
  • Like
Reactions: 1
2
Forstner bit would be my choice, with these things in mind. They are best used in a drill press at slow speeds. If you are freehand drilling, it is hard to get the holes straight down, in which case, you can drill a hole in some ply at the drill press using that bit, then clamp the pre-drilled piece on your project and use it as a drill guide. You should use a variable speed drill at low speed. You want to hold it as steady as possible. Here is a sample:
Font Rectangle Metal Fashion accessory Eyewear

You can use a regular drill bit, but it may not be as smooth a bore, and there could be tearout below, for this approach, consider using a brad point. The "wings" at the end will help make a good cut. But again, I'd make a drill guide to make sure the hole is vertical. Here's a sample:
Aircraft Aerospace manufacturer Twig Fighter aircraft Rectangle
See less See more
  • Like
Reactions: 4
Which episode is that one, Rick?
1304 with the old fashion hardware that demands precision drilling to match the left and right sides of the cabinet. From the problem presented I see the router as a great way to drill the 1/2-inch hole and then clean the 1/8-inch sides of the larger hole in the plywood. The plunge router will make sure the holes a true and drilled straight every time. The 1/4-inch plywood template can be measured and drilled with the drill bits but if you want a clean cut on both sides of the 1/2-inch plywood the router is the only way in my opinion.
  • Like
Reactions: 1
I'm looking to cut lots of 3/4" holes through 1/2" plywood, and want the holes to be as smooth and clean as possible. I think I need a spiral bit, correct? Should it be up spiral, down spiral, or compression spiral? My router can handle 1/4" and 1/2" bits. Can someone recommend a brand? Having a hard time finding any that'll do the job at Home Depot, Lowes, and Lee Valley tools.
take a look at the cncrouterstore.ca and contact [email protected] and ask for spiral compression bit.
Welcome to the forum @mcmulticam
Drill presses have limited reach. I'd also recommend a Forstner bit. There are a few versions of PortAlign jigs out their to use with a hand drill and as stated above you'll want to run the bit no faster than 300rpm or so. To avoid blowout set the depth stop so only the tip of the bit pokes through the back side. Then flip the board over and using the centerholes drill from that side to finish the holes.

If you were doing this on a CNC with a pocket toolpath I'd use a downcut spiral bit for the first pass and a spiral upcut bit for the rest. . A handheld router with a template bushing and a template would work but of course you need the template.
4D
Spiral compression bit if you insist on routing the holes
Lots of ways to approach the job and all of the suggestions above would work with some limitations. Things to be considered include;
Are the ply faces very thin presentation veneers, or are the layers in the ply of equal thickness.
How are you going to establish and fix the hole positions?
How are you establishing the hole size, do you want a 3/4 bit and a direct plunge, or are you going to use a template and guide with a smaller bit, or a pattern bit and bearing, or are you content to drill with a forstener bit?

I believe that the simplest, least painful approach would be a decent 2 speed geared portable drill mounted in a drill stand and a 3/4 forstener bit, with a waste board underneath to drill into. This ticks pretty well all the boxes, the forstener should give a neat entry into the holes, and in combination with the backer board a neat exit on the other side, while the drill stand should ensure that the holes are perpendicular to the surface. You should also be able to align the point on the forstener to your positioning marks if you are simply measuring and marking positions.

You could use a 1/4 compression bit, guide bushing with a template, and a backer board. The opening in the template is larger than the guide bushing, you sit the router on the template, plunge through the ply and into the backer, then circulate the router around with the guide bushing making contact with the template to control the hole size. This would probably give you the best overall finish. Don't use a compression bit without a backer board, there is a possibility that the emerging tip will chip the back side unless it is supported. Also don't use a compression bit and try to work through in stages, the tip is an up spiral and will try and chip the face of the ply. If you plunge through the ply first close to the centre of the hole this can still happen, but as the fully engaged bit expands the hole to finished size, the chipped part is removed anyway.

For a direct plunge with a 3/4 bit, the bit needs to be a plunging bit, i.e. able to remove all of the diameter at once by having cutting faces on the entry end as well the sides. These are fairly rare, most bits in this size range are for profiling and only cut along the side, though some offer very shallow depth penetration as well. These bits can cut through the depth of a piece of material, but need to plunge down creating a ramp, not ideal for a small round hole.
See less See more
I'm looking to cut lots of 3/4" holes through 1/2" plywood, and want the holes to be as smooth and clean as possible. I think I need a spiral bit, correct? Should it be up spiral, down spiral, or compression spiral? My router can handle 1/4" and 1/2" bits. Can someone recommend a brand? Having a hard time finding any that'll do the job at Home Depot, Lowes, and Lee Valley tools.
Forstner bit I suggest Freud.it has a wavy edge and you get a very clean entrance edge. Use a backing material to get a clean exit.
  • Like
Reactions: 1
A 3/4 drill bit is going to give blowout on the back side to some degree or another. A backing board on the press table will help reduce but not eliminate blowout. So cheat. Drill the holes with a 3/4" bit the best you can and then get a 1/16" radius roundover bit and bevel the edges of the holes. This cleans up a lot of blowout. If the holes are for air flow, this will look OK and eliminate a lot of sanding.

You didn't say exactly why the holes are needed in the plywood. That may help.
  • Like
Reactions: 1
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top