Drilling Rubber

Quickstep192

Anarchist
841
160
Chesapeake
I got this gizmo to allow me to attach something to my pulpit while still being able to remove it. It’s perfect except for one thing - it doesn’t fit 1” tubing.

The rubber insert in the center makes it fit a 3/4” tube; without the rubber insert it fits a 1-1/4” tube.

Any ideas on how to enlarge the center of the rubber insert so it can fit a 1” tube?

I just realized I forgot the picture.

AC7FEB1A-9515-4A82-987A-ECA5FA19E305.jpeg
 
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Orion Jim

Member
292
154
New England
It would be far easier to increase the diameter of your rail than to ream the rubber insert to the correct diameter. Several wraps of Rubbaweld rigging tape (or your alternative of choice) would suffice without being a permanent alteration.
 

hdra

Anarchist
653
145
Drilling Rubber is a bugger, and especially with that kind of thing that has an OD & ID so close together. I agree with Orion Jim - just wrap tape around the rail to beef it up, or if you want to get real fancy see if McMaster sells a rubber insert that is the right size.
 

cyclone

Super Anarchist
1,441
676
Maine
A hole saw can be used on some dense foams and rubber. It’s not always tidy and it may be tricky to hold down your insert to keep it centered and prevent the saw from grabbing. You can sharpen the edge of some 1” metal tubing to form a punch. You can try to buy a rubber grommet with the desired OD/ID.
 

Son of Hans

Member
165
86
San Diego
I've had good luck with bits of hose as bushings. Wall thicknesses vary, but you might find some radiator hose with 1" ID and 1-1/4" OD. I don't think you have any realistic chance of opening up what you have.
 

Quickstep192

Anarchist
841
160
Chesapeake
OK, I'm an idiot!!!

I carefully clamped the entire thing a a drill press vise and started drilling with a Forstner bit. It was gong very well, but about half way through, the rubber sleeve began to push through the piece I was drilling.

Turns out there was a 1" ID sleeve outside the 3/4" ID sleeve.
Somebody was thinking, but it wasn't me.
 
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DDW

Super Anarchist
6,575
1,148
Doh!

Those things typically come with three inserts, or concentric ones like you found. For odd sizes it is possible to 3D print one the size you need, using TPU.
 

Steve

Anarchist
563
77
duluth, mn
You got to be kidding me!
I kid you not, years ago i built a snowboard base sander and had 2 large aluminum drums made, each with different durometers of rubber vulcanized on them and then had a spiral groove pattern machined on one and a diamond pattern machined on the softer one which was the power feed wheel. The vulcanizing was done in Michigan and the machining was done in Minnesota by a company that made large conveyors. Freezing was how they did this, how else could you machine a soft durometer rubber?
 

ryley

Super Anarchist
5,519
667
Boston, MA
as an fyi, blue sea recommends keeping the rubber wet while it's being drilled - this is for their through-deck cable clams but seems like it would work with this. glad you found the insert though - these things usually expect tubing to be one of 3 sizes.
 

Quickstep192

Anarchist
841
160
Chesapeake
Having heard about this freezing thing, it seems to me the piece I was wanting to drill could have been filled with water, frozen and drilled. The ice would have provided a center for a drill bit and would have cooled and lubricated the cut.

I’m almost disappointed that I don’t need to drill it now!
 

slug zitski

Super Anarchist
6,291
1,246
worldwide
Having heard about this freezing thing, it seems to me the piece I was wanting to drill could have been filled with water, frozen and drilled. The ice would have provided a center for a drill bit and would have cooled and lubricated the cut.

I’m almost disappointed that I don’t need to drill it now!
To freeze stuff use a spray can of compressed air from the hardware store….turn it upside down when you spray and the propellant will spray out and super cool your component
be careful with your fingers

this is the same technique you use when dropping a metal stock rudder that is stuck because the bearing has swollen , gripping the rudder stock

obviously you only chill the stock

 




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