Reducer tolerence

I need to cut a reducer fitting for my dust collection system. What are good tolerances that will allow my piece to slide over the fitting without being too tight or too sloppy. I don’t really have much experience with cutting within tolerances. Most of the things I’ve cut have been artsy sorts of things where it’s only appearance that matters.

Any comments on best materials to use would be appreciated. I will be using 3" PVC sewer pipe to 4" intake on dust collector.

Hi Ward,
Many of the fittings on the dust collector systems are tapered, so unless you are cutting tapered. Are you cutting a fitting that goes over the outside or into the inside of the tube? If on the outside, measure the end of the fitting and the “top” of the fitting to figure out the change in diameter, and then choose a dimension that is halfway between.

If the walls of the fitting are straight - then I would choose to go .001 or .002 oversized.

Thanks for that. Nothing is tapered, just straight stuff. Wasn’t sure how many thousandths was advisable. Appreciate the input

A trick i learned when i did mine was buy some 2" black electrical tape and wrap it around the smaller fitting until it fits snug into the larger one. I have a half dozen fitting sized up like that and none of them have ever come apart. Just an idea.

I’ve done that in the past and it works great, but this time I have an inch diameter difference and several fittings. That’s a lot 'o tape. Plus, and even more important, I want to practice something slightly more technical, but so critical that I can’t make up a little slop with tape if I need to.

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Don’t limit yourself with thinking that the machine is your only solution. Carve a spacing ring (to fill the gap) then run it through a router with a camphor bit to allow it to fit easier.