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Ok. as mentioned in an earlier post I bought a 6mm piece of aluminum plate to make an insert plate with. All went to plan and it is now installed in the table top.

Before drilling the centre hole I thought it a good idea to measure my largest bit that I currently have and I need to drill a 35mm hole to accommodate it.

I know that ready made insert plates come with rings so you can select one to suit the bit size etc.

On my aluminum plate I can't do this (At least I wouldn't know how)

Would it be ok to insert say a 1/4" or 1/2" bit into the 35mm hole and would it be safe to use it this way?

Thanks
 

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@Badger120 - I presume when you say a 1/4" or 1/2" that you're referring to the diameter of the cutter and not the shank. Since 35mm is about 1 1/2" inches, that would be fine. What you would be concerned with is the length of your workpiece - if it straddles the hole, then no issues. Using a small bit in a large hole is an issue if your workpiece has a chance of diving into the hole. The reason they make larger center rings is to avoid a large gap between the cutter and the ring when using larger diameter bits.
 

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I made a plate that takes insert rings but I have a milling machine that I made it with. You might be able to do it with a drill press if you can find a hole saw with the right diameter to make the rebate the ring has to sit in. I was very careful with mine and it is a press fit but it's possible to use screws to hold them in too. At 35 mm opening it's what Vince said. A lot of smaller routers come with an opening slightly smaller than that to accommodate the Porter Cable styled guide bushings which require a hole 1 3/16" I think it is.
 
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What Vince said. I often use a larger insert hole with smaller bits to give better dust/chip collection. You do restrict the size of pieces you cut,because like Vince said small/short pieces will tend to be drawn into the space around the bit and cause a safety hazard.
Since that is an aluminum insert you might consider routing a lip around the hole by using a rabbet bit with a bearing guide that will follow the hole and give you a 1/8" rabbet for the insert to set into. You can buy or make blank inserts and drill your own hole in them. You can make the hole to fit standard inserts that way.
Herb
 

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What Vince and others said...I would add that since it is aluminum (unless it is coated) wax the heck out of it so it doesn't leave black marks on your project piece. Do this often or you will have a tough time with your finish.

Good luck...
 
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I made a plate that takes insert rings but I have a milling machine that I made it with. You might be able to do it with a drill press if you can find a hole saw with the right diameter to make the rebate the ring has to sit in. I was very careful with mine and it is a press fit but it's possible to use screws to hold them in too. At 35 mm opening it's what Vince said. A lot of smaller routers come with an opening slightly smaller than that to accommodate the Porter Cable styled guide bushings which require a hole 1 3/16" I think it is.
I made mine basically like Chuck did. I milled a hole in the plate with a step. I think you could do it in a drill press with a fly cutter at slow speed. I made a large stepped round insert out of phenolic that is held in with 2 screws. I cut the big stepped hole so it would fit my largest panel raising bit. I bored the phenolic insert with a forstner bit with a stepped hole to accept Porter cable style guide bushings https://www.amazon.com/POWERTEC-710...=2025&creative=165953&creativeASIN=B01IMORJHM I cut the tubes off the larger guide bushings just leaving a hole that the bit will go through.It reduces the hole down to a safe size. That way you can also use guide bushings in the router table if you want to.
 

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You could probably find a mahine shop that could mill the rebate for you with great accurace, but you'll need to bring them a set of inserts you intend to use. Many are made of plastic, others aluminum. If you want to use screws, you will need to drill and thread into the rebate. So look for a small set of inserts that are pre drilled for the retainer bolts. Make sure you buy lots of extra retaining bolts, they are small and they disappear in an instant.
 

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If you make different inserts make sure the hole is centered. you can make one to be able to use router bushings.
 
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The problem with those tiny screws is that you can loose them down the hole and into the router, then if you can't find the screw, and start the router , it will proceed to spit out cooling fins before the sparks start coming out the top of the router, VOE. Makes an awful noise too.

If you are determined to use screws,have a good magnetic screw driver or put a rare earth magnet on the screwdriver shank to keep the screws from getting away.

I liked Nicks comment that Aluminum likes to turn some wood black, and it is hard to remove the stains. The commercial aluminum inserts are anodized to protect from that.
Herb
 

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Ok. as mentioned in an earlier post I bought a 6mm piece of aluminum plate to make an insert plate with. All went to plan and it is now installed in the table top.

Before drilling the centre hole I thought it a good idea to measure my largest bit that I currently have and I need to drill a 35mm hole to accommodate it.

I know that ready made insert plates come with rings so you can select one to suit the bit size etc.

On my aluminum plate I can't do this (At least I wouldn't know how)

Would it be ok to insert say a 1/4" or 1/2" bit into the 35mm hole and would it be safe to use it this way?

Thanks

@Badger120
Will you ever need a larger diameter bit? If not, please read on.

I am going to express a somewhat contrarian view. First I note that you list your place os residence as one of the last bastions of Imperial measuring units yet you use metric units for some things and Imperial for others. 35 mm is 0.003 larger than 1 3/8 inch.

Unfortunately the porterCable (PC) size template guide, referenced by @roxanne562001 have taken over the world. These template guides and insert plates require a 1 3/8 inch counter bore 1 3/16 through bore.

A larger set. 1 3/4 inch counter bore 1 1/2 inch through bore would seem to work better for you. Such a set can be obtained from only one source I know of, Lee Valley. 1-3/4" Router Plate Inserts - Lee Valley Tools

Steel has a greater hardness than aluminum so you could use HSS steel Forstner bits such as these sold by Lee Valley: HSS Forstner & Saw Tooth Bits - Lee Valley Tools You should use a cutting fluid such as https://www.amazon.com/gp/product/B003X3ZKXI/ref=oh_aui_search_asin_title?ie=UTF8&psc=1 if you choose this route,
 

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Discussion Starter · #12 ·
Thanks for all the replies guys, much appreciated. Can't see me using a bit larger than about 32 - 35mm so I'll just drill a hole and keep it simple for now.

Should I need to use larger bits in the future then I'll probably buy an insert plate complete with rings.

Thanks
 
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