# Need Help 8" PVC Question



## tred1956 (May 28, 2014)

Hi,
I am building a wet tumbler and using PVC for the tumbling drums. I have 6" & 8" PVC pipe. The 6" pipe is schedule 40 and I bought Cherne mechanical plugs for them. They fit and work perfectly. Now my problem. My 8" is schedule 80 and the mechanical plugs I bought are too big for the schedule 80. They are designed for schedule 40.

Schedule 80 and schedule 40 have the same outside diameter. The schedule 80 is thicker pipe (made to be pressurized). I have a router but no router table. 

What I need to do is increase the inside diameter of the last two inches of the pipe to the same as schedule 40. I am guessing I will only need to remove 1/4 inch or less.

ANY suggestions as to how to accomplish this? This pipe is about $74.00 a foot so I have to be sure I don't mess it up.

Thanks in advance for any and all input
Doug


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## Dodis (Feb 25, 2013)

Tred,

Sounds like a two-step job for the router. 

Main concern would be router speed melting the PVC, so hopefully you have a variable speed router. I have cut PVC with a circular saw without melting, but that is still 5x slower than typical router speeds.

First, use a rabbeting bit (with multiple bearings) set to cut a 1/8" deep rabbet, may take a couple of cuts going deeper each time to not take too big of a bite.

Once at the max depth you can go with the rabbet bit, then switch to a long 2"+ pattern bit (bearing on top closer to the router) to continue the cut till you have your 2" depth. Possibly may need two, one shorter 1" or so then the longer to get full depth.

Probably end up spending as much as a foot of pipe for 2-3 bits if you don't already have them, but they'll last a long time after...

Mike "Dodis"


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## Dodis (Feb 25, 2013)

Tred,

Sounds like a two-step job for the router.

Main concern would be router speed melting the PVC, so hopefully you have a variable speed router. I have cut PVC with a circular saw without melting, but that is still 5x slower than typical router speeds. Second concern is if you can balance the router on the edge of the 8” pipe. If it feels uncomfortable, you could use a flat piece of 3/8”-1/2” ply to make a base for the router that will completely span the end of the pipe. Being a single use base for bearing guided bits, doesn’t ‘have’ to be transparent.

First, use a rabbeting bit (with multiple bearings) set to cut a 1/8" deep rabbet, may take a couple of cuts going deeper each time to not take too big of a bite.

Once at the max depth you can go with the rabbet bit, then switch to a long 2"+ pattern bit (bearing on top closer to the router) to continue the cut till you have your 2" depth. Possibly may need two, one shorter 1" or so then the longer to get full depth.

Probably end up spending as much as a foot of pipe for 2-3 bits if you don't already have them, but they'll last a long time after...

Mike "Dodis"


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## PhilBa (Jun 30, 2014)

I'd go with a jig that can allow you to keep the router perfectly aligned. Here's one approach. Obviously this omits some details and spacing needs to be worked out but you just slide it in and rotate the assembly 360 deg. Use a straight bit and align the router to take of just enough to fit the plug. Multiple passes at increasing depth will probably be needed.

edit: for some reason my picture doesn't show up. It does when I edit it but not when I look at my posting in the thread. Not sure why that is.


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## woodnthings (Jan 24, 2009)

*I think I get Phil's idea*

Unlress I'm adding to it, here's what I see.

Make a 3/4" diamter plug for the inside that slides freely around the inside, but doesn' wiggle. make a spacer of 3/4" less than the diamter to space the plug down. Make a round "coiver plate" to mount you router on top of that is about 3" larger, say 12" in diameter.

Locate the outer edge of the cutter at the diameter you want the inside to be and mount the router, maybe a slotted hole arrangement for fine tuning. When you turn the assembly in the pipe it should create a new, and reduced inside diameter ... in theory. To increase accuracy make an additional 12" diameter piece with a hole for the OD of the pipe so it will spin smoothly around. 

The "theory" is you are spinning the assembly/plug on the inside of the pipe while the router cuts a specific amount from the inside diameter.

:blink:

Another idea is to use a 1/2 circle the pipe's OD with enough support for your router base and work strictly from the outside. You will be "trapping" the wall between the cutter and the guide so it must be held in constant registration by pressing inward as you circle the pipe.


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## PhilBa (Jun 30, 2014)

Trying again to post the picture.

edit: ugh, NOW it shows. sheesh.


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## Dodis (Feb 25, 2013)

As bad as my double post! :1eye:


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## FrankC (Aug 24, 2012)

Do a search to cut a groove in a round cutting board, lots of different methods. I would make the first cut maybe 1/2" deep, then deepen it with a pattern bit following your first cut.


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## Dan3103 (Mar 24, 2015)

Can't you get the correct Schedule 80 plugs for the Schedule 80 pipe?


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## tred1956 (May 28, 2014)

Hi,
Thanks for all the input fellows. Some great ideas for sure. Found a friend on a accurate shooter forum who lived close and owns a metal lathe. He called yesterday and said they are ready to go.
Again thanks for all the input
Doug


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## Al B Thayer (Dec 10, 2011)

BTW
Both Schedule 80 and 40 are used in pressure applications. Schedule 40 DWV fittings are not. 

Al


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