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Turning Rubber on a Lathe?

CalgaryPT

CalgaryPT

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Is it possible to turn rubber on a lathe with standard tools? I need to make some custom rubber grommets for a couple of holes I drilled through my truck wheel wells just behind the rocker panel. I had forgotten that the panels (AL in my F250 SuperDuty) would be double panels, so the grommets I used to use for previous trucks that were steel won't fit as the holes are too thick after step drilling. Realistically, I've de-burred them so well with a Dremel you can run your finger across them, so I could always use stainless cable wrap. But I want to do it right.

I've heard of products like Versimold https://www.amazon.ca/dp/B00NQ11AQI/ref=cm_sw_em_r_mt_dp_HIyZFb44J1YQS for grommet making, but also of people turning rubber with standard tools, sometimes with the aid of circuit chiller. Lots of YouTube vids for both. Another method apparently is to make a holder for your Dremel and turn them this way.

The rubber would have to be soft enough to get squeezed into the hole like a grommet, but hard enough to turn. If worse comes to worse I can always make it from acetal, then glue it into place (hey, that's not a bad idea :) ).

Has anyone tried this?

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Maybe not the “best” option but get a short piece of heater hose. Slice it lengthwise, slip it over the wires, slide it into the hole in the aluminum. Put a zip tie on the hose to snug things up, if really paranoid put a zip tie on either side of the hose on both sides of the panel
 
Yes, I have turned rubber. It was the stuff PA sells for the boat trailers. It may be too hard for your application though. I made rubber feet for a lathe. Worked great for that application.
 
Chicken lights said:
Maybe not the “best” option but get a short piece of heater hose. Slice it lengthwise, slip it over the wires, slide it into the hole in the aluminum. Put a zip tie on the hose to snug things up, if really paranoid put a zip tie on either side of the hose on both sides of the panel
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Yeah, that's s good option and I've done that before with commercial split loom. Works like a charm. I think I have Covid fever or something; I'm looking for more things to do than necessary.
 
I wonder what type of surface protection Ford uses on the aluminum panels? Once you disturb that protective layer you may be setting yourself up for corrosion issues.

In aircraft work the surface is usually alodined (and sometimes primed after alodine treatment with zinc chromate primer ) after working it.
 
You definitely could. I have run production jobs on cnc machines that turned and parted off parts made from rubber.
 
I remember as a kid shaping a rubber stopper on a grinding wheel. A course wheel cuts it pretty easily.
 
This from the Atlas MOLO, doesn’t specify what constitutes ‘hard’ but it’s a start. Machinery’s Handbook may reference it as well and may have a durometer specification.

-frank

A80A3B04-5FF9-474E-AA37-8DACFF19B010.jpeg
 
Perry said:
I wonder what type of surface protection Ford uses on the aluminum panels? Once you disturb that protective layer you may be setting yourself up for corrosion issues.

In aircraft work the surface is usually alodined (and sometimes primed after alodine treatment with zinc chromate primer ) after working it.
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Good points. My understanding is that can indeed be an issue, even with galvanic protection. However, it is really only a large problem when you mix two dissimilar metals such as AL and steel fasteners (which I won't be doing), or over larger surface areas. For the amount of surface area I've exposed (the inner ring of the hole), it's likely more AL that has been exposed under the box from large rock chips over the years than I have opened up. Also, mine is protected from the elements by another AL panel with a factory hole behind my panel that I will fish through. Some guys on the Ford forum use construction adhesive to cover patches. I once (15+ yrs. ago) repaired a farm trailer for a friend's Kobota tractor. I made him a new box from some scrap AL he had around. Lots of steel rivets, steel bolts and other fixtures that weren't AL. Last time I saw it there was more corrosion on the steel parts than the AL.

Based on some experience with waterproof rivets on boats, you're talking about a long period of time before this affects structural integrity even around the localized zone. I get that in aircraft work there needs to be minimal risk and any corrosion is a red light. I think Ford uses a AL/LI alloy that is treated, and I suspect by the time I have corrosion issues with an AL body, I'll likely have bigger mechanical issues that will force me to sell the truck.

Having said that, I've watched a lot of aircraft sheet metal videos, especially about riveting, and am always impressed by the rigid standards and procedures technicians use when working with AL. It makes me feels better about airplane safety.
 
Very easily made wood molds & liquid latex is an easy solution to any one-off rubber item. latex used to be purchasable at any hardware or farm supply store by the quart or gallon jug...if you do use it and end up with a half full jug, don't just leave it that way. The air space in the jug will provide enough air to slowly cure the remainder. using this stuff is where I learned (from my old man) to add enough small stones or nuts to the jar to bring back level full. I use the same trick to preserve 1/2 used bottles of gunstock wood finish's.
 
I've turned rubber using knife edge tools and it cut just fine. Even very soft (spongy) eurothane can be cut, it just takes a very sharp tool (knife sharp).
 
I turned rubber bushings on a lathe - long time ago - few inches long by over an inch wide or so - use HSS tooling that is sharp. It makes a black mess. Make sure it does not get too hot. You can smooth the surface, if needed with sand paper.
 
I'm sure I've seen those plugs in variety of sizes but just cant recall where or what they are called. Autobody supply? Electronics supply? They were for sure blanked off but actually had a small recess like for sheet metal.
 
PeterT said:
How many do you need & are they same size? I've made some simple molds & bought some casting urethane which can be had in many different durometers. (Silicone is quite expensive by comparison). The shelf life isn't super long.
https://www.sculpturesupply.com/det...tegory&vl=ReoFlex+40&cat=Rubber+Polyurethanes

Possible off the shelf solutions?
https://www.amazon.ca/s?k=rubber+plugs&ref=nb_sb_noss_1
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Thanks. I looked at the off the shelf solutions and it's tough to find grommets for thick metal. For now I only need one or two. I guess the other reason I'm looking to experiment here is I have to do some restoration work on an older car in the spring. All the grommets are shot, and I thought I would like to learn this need skill. Tapered firewall plugs are another commercial option.
 
Tom Kitta said:
I turned rubber bushings on a lathe - long time ago - few inches long by over an inch wide or so - use HSS tooling that is sharp. It makes a black mess. Make sure it does not get too hot. You can smooth the surface, if needed with sand paper.
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Yup I've turned the boat rubber bumpers successfully a few times...really sharp hss tooling makes a mess, and don't get too aggressive. I can't say exactly what "too aggresive" means but I know I've taken too big of a cut many times because it was pealling off nicely so I gave it more and then it grabs and rips it out the chuck and scares the hell out of a fellow.
 
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