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placing screws (or threaded inserts) into Rockler pro phenolic router table

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Forum topic by Chameleon posted 05-25-2020 11:50 PM 433 views 0 times favorited 7 replies Add to Favorites Watch
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Chameleon

29 posts in 851 days


05-25-2020 11:50 PM

Topic tags/keywords: phenolic how do i attached something to phenolic threaded inserts

Hope this is the correct forum for this question. Trying to attach Dust Right “Dust Bucket” (from Rockler) to bottom of Rockler Pro Phenolic router table (Rockler says it’s “solid phenolic”). Instructions say to use #10 or #12 screws, but I broke 1 of each size, and cracked the phenolic (not too deeply, I hope), using 1/8” pilot hole. The table is 3/4” thick. I was using a driver, but subsequently was told that you have to drill very slowly into this material. Also had a thought that using threaded inserts might be better if I want to remove and reinstall the Dust Bucket. Several Q’s (sorry, these will reflect my lack of experience): If using screws, what type, size, length, and what size pilot hole (Dust Bucket being attached has “very thin”—not sure of thickness—metal)? Same questions for threaded inserts (links appreciated!). Fortunately, the attachment points on the Dust Bucket can be placed on either the sides or front and back; since I messed up the sides, I can move them to the front and back. Finally: Any particular type of epoxy to repair the damage I’ve done? Thanks, Howard


7 replies so far

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PurpLev

8574 posts in 4425 days


#1 posted 05-26-2020 12:11 AM

Phenolic is a hard and slippery material. It should be pre drilled. Drill or punch a pilot hole first to help keep your drill bit centered and not wandering. Make sure your drill bits are sharp and go slow and steady. I’ve worked with phenolic often and it’s a good material just need pilot holes to keep bits centered.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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CaptainKlutz

3189 posts in 2271 days


#2 posted 05-26-2020 01:27 AM

Fasteners is composites can be PIA. The Rockler Phenolic is mislabeled IMHO, which makes using it more difficult. It behaves more like a reinforced molded plastic (which it is), than phenolic plate normally used in industry.

The key is drilling right size pilot hole.
Installing screws into composite materials should be treated just like putting machine screws into a block of metal, not like drilling into wood.
So even when using sheet metal screw, Drill OD should be same as root diameter of screw. Couple thousands larger or smaller is acceptable, but pilot hole needs to be larger enough the screw body has minimal interference. Drill depth also needs to be screw length +/- 1/8”.

For hidden locations another trick is to use hex head sheet metal fasteners. It is harder to twist off the hex head. (but not impossible – DAMHIK)

Fixing a crack in the phenolic top can be done with any epoxy. Would be best to use slow cure (30-60min) version. Slow cure epoxy gets thinner as it heats up and completes the cure. If there is any chance it can leak out the bottom, or edge; use some clear plastic packing tape to seal the area before applying the epoxy.

My preferred thread insert is steel tapping insert. They can be found at most any fastener supplier (MSC, McMaster, Fastenal, Grainger, etc).

Woodcraft and some of the other wood working stores sell a brass version that installs with wide blade screw driver, and they work OK for softer woods.

But for hardest woods or composite, I prefer the steel version with hex shank drive for installation.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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mtnwalton

78 posts in 1802 days


#3 posted 05-26-2020 03:53 AM

I have the referenced table and dust bucket from Rockler ; my first phenolic table and I experienced some of the same problems when installing it. I had chip out as well and had to relocate one screw. I would avoid the threaded inserts unless carefully countersinking to allow for the sharp threads as it enters the phenolic.

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Chameleon

29 posts in 851 days


#4 posted 05-26-2020 04:16 AM

Thanks for the replies. Captain K, since I’ve never thought about the root diameter of a screw, please tell me if I’m interpreting your links correctly. From your second link, it seems to me that the pilot hole for a 10-24 or 10-32 screw should be 11/64 (closest I could come to the fractions of an inch given in decimals in the chart). For a 12-24 screw, it would be 3/16 – 13/64. Would a 1/2” screw length be appropriate? Noting the caveat from mtnwalton about threaded inserts (BTW, it’s nice to know that I’m not the only one who’s had problems with chipout), the McMaster-Carr site says that for 10-24 thread size, the drill bit size for the insert is 19/64. The installed length is “0.25-0.499”—does that mean that only part of the .472” long insert might be installed? Along with this, I’d use a 1/2” long 10-24 bolt, correct? Thanks again, Howard

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CaptainKlutz

3189 posts in 2271 days


#5 posted 05-26-2020 05:09 AM

Chameleon
Sorry for assuming you knew anatomy of the lowly Screw and/or Screw threads.
A screw is much more complex than it looks!
The root diameter is also called the minimum diameter, as shown in this image borrowed from WWW:

When drilling a pilot hole for any hard material, the pilot hole should allow the minimum diameter of screw thread to just fit into hole. The PDf linked eariler was for MACHINE screws, and was to show you a couple things:
1) pilot hole size is just slight larger than minimum thread diameter
2) there is an acceptable range for pilot hole that allows threads to still work.
But that is for Machine screw, not sheet metal screws. So the actual numbers are not usable for other screw thread types.

Now that some more education has been shared, my suggestion:

Measure the minimum diameter on the screw you want to use (using calipers) and use the next larger drill bit size. If you don’t have a letter/number index of drill bits, then things get a little tougher as sometimes you can not use the next larger fractional size drill bit without losing holding power. In that case, use the next smaller size.

As suggested earlier, drive screws slowly and consistently. If using a drill driver, be sure to use one with torque limit to avoid breaking screws off. Can also use wax (beeswax/paraffin) as lubricant on sheet metal screws into composites, just like recommended for screws into hardwood.
BTW – By using proper size hole, wax as lubricant, and not applying to much torque when installing sheet metal screws; they can be removed and reinstalled several times. Should be able to eliminate the need for inserts?

Proper screw length of 1/2in should work. Just make sure you not using cheapanse measuring method that includes the length of head.

For your question on steel threaded inserts I mentioned:
Yes, some designs will not have full insert inside the material. You will notice there is portion without external threads. This extra is often used as stand off in thru bolt uses to keep the bolted item elevated from surface. Find it most common in Marine applications with SS inserts. Your use is into a blind hole, and you will want the full insert buried into plate or the dust bucket might leak around the edges without a thick gasket. :-0)

Hope this clarifies any confusion.
Cheers!

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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HokieKen

14074 posts in 1915 days


#6 posted 05-26-2020 02:50 PM

In my experience best way to go with phenolic is to drill and tap it just like you would metal. You can buy a cheap tap for the soft material so it wouldn’t be expensive even if you don’t already have a tap. If driving in screws, Captain gives good info and advice. I would use a larger pilot bit than I would normally use on wood. The phenolic won’t compress really it’ll just displace with the threads. So the more you displace the more likely you are to distort it. For that same reason, I think threaded inserts are a terrible idea with soft materials. If the screws will be close to the edge of the table, another option would be barrel nuts.

-- Kenny, SW VA, Go Hokies!!!

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mtnwalton

78 posts in 1802 days


#7 posted 05-26-2020 06:25 PM

As a retired machinist, i usually use tap drill sizes ; but in materials like this, you can learn a lot by drilling a slightly larger tap drill size, then try the screw in the material. If it’s fighting you, go slightly larger until you get the fit you want.

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