Looking for a tool and/or process to modify a plastic elbow fitting.

Erich · Feb 18, 2021

Okay I have a need to modify qty 1 of a 4 inch PVC Elbow fitting.
Fittings are all designed to work with Schedule 40 wall thickness pipe.
For this application I am using thin walled pipe and I need the ID of the fitting to be opened up about .18 inches. What tool will work around the inside of the elbow?
Accuracy is not high +- 1/16 inch would be plenty good. I just need to open it up to create clearance for the end fitting on the stinky slinky in my RV.

I am envisioning something like the old flex hone with the spring mounted abrasive balls. But that is not right for plastic and I have a lot to take off.

Extrude honing would probably work. Any other suggestions?

J_R_Thiele · Feb 18, 2021

Boring it out on a lathe or mill would be easiest and fastest.

If you are modifying fittings and pipe, you need to learn how to use heat to form and bend it.
This would allow you to increase the diameter and change the angle if needed.

Here is a link to a site that will be helpful.
Bending & Forming PVC – THE PLASTIC SPORK BLOG

Plastics can be welded.

crossthread · Feb 18, 2021

I wanted to make some PVC rod holders. I found that if you heat up the pipe with a heat gun you can easily form the pipe and when it cools it stays put. I was trying to bell the end of the pipe to make it easy to insert the butt of a rod. It worked great. I think if you can heat the pipe with a heat gun (doesn't take much) you could find some way to expand the fitting easily. Some kind of expanding mandrel even made out of wood could be used. Cut a disk with a jigsaw or whatever of wood to fit the inside of the fitting, drill a hole in the middle of the disk. Cut the disk halfway across from the edge to the hole. Put the mandrel in the pipe, heat the pipe, and drive a cone shaped wedge into the hole.

DDoug · Feb 18, 2021

crossthread said:
I wanted to make some PVC rod holders. I found that if you heat up the pipe with a heat gun you can easily form the pipe and when it cools it stays put. I was trying to bell the end of the pipe to make it easy to insert the butt of a rod. It worked great. I think if you can heat the pipe with a heat gun (doesn't take much) you could find some way to expand the fitting easily. Some kind of expanding mandrel even made out of wood could be used. Cut a disk with a jigsaw or whatever of wood to fit the inside of the fitting, drill a hole in the middle of the disk. Cut the disk halfway across from the edge to the hole. Put the mandrel in the pipe, heat the pipe, and drive a cone shaped wedge into the hole.

Like this ?
2" scd 40 PVC, heated and then pushed down over a mandrel.

crossthread · Feb 18, 2021

Yup. Very much like that. I also used the same principle to make a piss tube for my sailboat. Much easier then trying to build up enough pressure to make it over the side.

TeachMePlease · Feb 18, 2021

crossthread said:
Yup. Very much like that. I also used the same principle to make a piss tube for my sailboat. Much easier then trying to build up enough pressure to make it over the side.

Musta used a Swiss machine to make the mandrel.

Scottl · Feb 18, 2021

For a one-off I'd grind it with the largest diameter drum sander I had after scribing the desired ID on the end. I'd use my old Starrett hermaphrodite caliper to scribe it.

Probably best with the drum sander mounted in a wood lathe or even a drill press but I have done something similar (only smaller) with one mounted in a portable drill in one of those clamp stands. I have an inexpensive HF corded drill mounted in one and I call it my "short lathe" which I use for nasty work like sanding and buffing. In good weather I can clamp it to a sawhorse outside, keeping grit etc. out of the shop.

Erich · Feb 18, 2021

Here is a picture of the type of part I would like to open up.

DDoug · Feb 18, 2021

Erich said:
View attachment 314204

Here is a picture of the type of part I would like to open up.

Yup, I think most of us already new what we were looking at by your first post.

Erich · Feb 18, 2021

The comments to just bore it out on the lathe or mill or open up with a drum sander made me wonder If people were thinking straight fitting. Just clarifying.

DDoug · Feb 18, 2021

Erich said:
The comments to just bore it out on the lathe or mill or open up with a drum sander made me wonder If people were thinking straight fitting. Just clarifying.

I figured you could creatively mount it on the lathe, or milling with boring head would be
much easier, to set up in the vise.

David_M · Feb 18, 2021

Look at a 110mm DIN 90 degree PVC fitting.

This is just for reference (find one stateside): 110mm Plain 90 Degree PVC Elbow for PVC Pressure Pipe System (plasticpipeshop.co.uk)

You will probably need to shim it to your size.

paul39 · Feb 18, 2021

I would make a slug from wood 1/8 inch bigger than the piece that will go into the elbow 1/2 inch longer than the inside of the connecting part of the elbow. Taper 1/2 inch down to 1/8 inch smaller than the connecting part of the elbow. Sand smooth and wax with paraffin. Screw that, tapered side up to a chunk of plywood a foot or so square. Gently heat the rim of the elbow with heat gun and force over the slug. Repeat until you have what you want. If the taper is not wanted turn off most of it on the slug, then put a small chamfer on it, heat & force as before.

Paul

true temper · Feb 18, 2021

Working in the field many miles from town, I have made couplers, bent special angles and made sweeps on PVC pipe. Using the hot exhaust from my diesel ditching machine. Keep it moving and it heats it up real nice.

72bwhite · Feb 18, 2021

Heat it and pull a ball mandrill,
Silly question why not just use a bell reducer or a bushing

LKeithR · Feb 19, 2021

If you're actually talking about opening up the inside of the entire elbow you may be using the wrong
material for the job. Why is that extra 1/16" important for the performance of the part?

You might want to consider using thin wall steel or aluminum tubing with pre-formed elbows. That will
give you a smooth, uniform inside diameter right around the elbow...

tomjelly · Feb 19, 2021

heating it up is definitely the easiest fastest way to do what you want. wear gloves

Bill D · Feb 19, 2021

I belive the trick is to find a liquid that boils just above the pvc softening point but below melting. Get it boiling and soak the fitting until it gets soft enough. Various oils would probably be about right. How hot does a turkey fryer get? Boiling water is not quite hot enough.
I have done it with a torch but it is easy to rush things and char the pvc. Have a damp rag to freeze the work when it is correct.
PVC conducts heat slowly and it has to all be heated up inside to bend.
Bil lD.

PVC melting 185 F. Forming 155F. Says water is plenty hot enough. Never worked enough for me. Probably have to leave it to boil for 30 minutes or more.

Tony Quiring · Feb 19, 2021

Fit is usually not critical as solvent glue fills and bonds

Just get a drum sander bit that will fit in a drill motor and carefully remove some material.

Once the end is opened enough to go into the mating part the glue will allow slipping to slide it on fully.

Simple task.

Sent from my SAMSUNG-SM-G930A using Tapatalk

DDoug · Feb 19, 2021

LKeithR said:
If you're actually talking about opening up the inside of the entire elbow you may be using the wrong
material for the job. Why is that extra 1/16" important for the performance of the part?

You might want to consider using thin wall steel or aluminum tubing with pre-formed elbows. That will
give you a smooth, uniform inside diameter right around the elbow...

Yup, failure of the OP to accurately describe the problem at hand.....

Looking for a tool and/or process to modify a plastic elbow fitting.

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