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Converting non-round hole to round?

Goodwill_HiFi

Goodwill_HiFi

Super Member
I'm going to replace a cord, and my plan is to switch from the stupid squeeze together cord retainer to a industrial/electrical strain relief that requires a 1/2" round hole. The holes for the black squeeze together retainers normally have flats on them. Am I going to be able to cut a nice round hole with a step bit, or it it going to jump around and look like I tried using an axe to make the hole bigger? I guess I could try filing the hole out before using the step bit, but I'd rather not. I've never used a step bit before.
 
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Mask the top of the hole. Back up the hole with a piece of wood, and clamp to your drill press table. Slow feed, light pressure, start cutting the wood, and ease into the metal. this all presupposed that you have removed the plate from the chassis.
 
luvvinvinyl said:
Mask the top of the hole. Back up the hole with a piece of wood, and clamp to your drill press table. Slow feed, light pressure, start cutting the wood, and ease into the metal. this all presupposed that you have removed the plate from the chassis.
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Nope it is the chassis. It can't be removed. I also don't have a drill press. I was hoping it would be something I could do with the amp assembled with a vacuum backing the hole up..... there is quite a bit of room in that area.

Of course, I can't even find the step bit right now. It's been sitting in the same spot, in the package for years, and now it's not.
 
Just fer sh!tzengiggles ... what's wrong with the squeeze type cord retainers? Those work perfectly fine if installed properly. I just squeeze em together with a pair of pliers while inserting them into the hole ...
 
sKiZo said:
Just fer sh!tzengiggles ... what's wrong with the squeeze type cord retainers? Those work perfectly fine if installed properly. I just squeeze em together with a pair of pliers while inserting them into the hole ...
Click to expand...

I've always hated them. The can fit sloppy, or they can fit supper tight. If tight, they're a pain to remove and a pain to install, and get marred up with pliers. Sometimes they can be removed and installed without marking them up, but that seems to be the exception in my experience, not the rule.
 
They are nasty little things. Very effective, but very nasty. I've lost count of the number of times I've nipped my fingers with flat jaw pliers trying to get them out without marking them. Little blood blisters that sting like hell. Evil little f$#kers.

My current solution is to heat them up with a heatgun so they are soft (and the wire inside is too) and turn them 90 degrees and they just pull out or push in. Then twist them 90 degrees back and all is well. I realized they were probably installed that way in the first place.(due to the slot shape- doh) It makes sense. :)
 
I realized a few minutes ago, that I actually need a hole larger than 1/2". The strain relief I have is for a hole for 1/2" conduit, which is an inside diameter, so much like NPT, 1/2" pipe thread is more like 3/4" in diameter. So unfortunately, the reamers that I can purchase cheaply aren't big enough. I guess I'll just use a file.
 
Goodwill_HiFi said:
....actually need a hole larger than 1/2". The strain relief I have is for a hole for 1/2" conduit....
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I was an electrician for many years and used various sized Greenlee knockout die/punches for making standard conduit holes in steel electrical enclosures. Like the one linked below (no affiliation). Probably the ideal method (assuming an adequate starter hole is already there) as there is no vibration and no metal shavings, both of which would be present if drilling or filing. But the die/punch and its bolt does require a lot of space on both sides of the panel, which could easily be a deal-breaker for your application
 
roger2 said:
I was an electrician for many years and used various sized Greenlee knockout die/punches for making standard conduit holes in steel electrical enclosures. Like the one linked below (no affiliation). Probably the ideal method (assuming an adequate starter hole is already there) as there is no vibration and no metal shavings, both of which would be present if drilling or filing. But the die/punch and its bolt does require a lot of space on both sides of the panel, which could easily be a deal-breaker for your application

https://www.ebay.com/itm/Greenlee-P...370166&hash=item2131732b1f:g:~iYAAOSw~HBaKMmL
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Note that the link is for a 7/8 in. hole...
 
Goodwill_HiFi said:
...The strain relief I have is for a hole for 1/2" conduit, ...
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UncleBingo said:
Note that the link is for a 7/8 in. hole...
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The punch linked is for a standard knockout hole for 1/2" conduit, which is 7/8".

FWIW, NPT 1/2" nominal pipe outside diameter is 0.84", as the OP did mention NPT threads. The more common EMT is smaller, but the thread diameter of the actual connectors used with it is likely closer to the size of rigid pipe.

What is your point?
 
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Goodwill_HiFi said:
I've always hated them. The can fit sloppy, or they can fit supper tight. If tight, they're a pain to remove and a pain to install, and get marred up with pliers. Sometimes they can be removed and installed without marking them up, but that seems to be the exception in my experience, not the rule.
Click to expand...

They work extremely well,and are available in many models to accomodate any type of wire/cable you'd care to imagine.The only time there are ''issues'' is when using the incorrect strain relief/wire combination. And they aren't intended to be installed with ordinary pliers.




sKiZo said:
Just fer sh!tzengiggles ... what's wrong with the squeeze type cord retainers? Those work perfectly fine if installed properly. I just squeeze em together with a pair of pliers while inserting them into the hole ...
Click to expand...

You can invest in a pair of Heyco pliers if you do a lot of this type of work,or just buy a generic ''strain relief bushing assembly tool'' from some cheapie tool store:

51~v~strain-relief-bushing-assembly-tool.jpg


Installation video,compete with nice soundtrack:

 
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arts said:
They work extremely well,and are available in many models to accomodate any type of wire/cable you'd care to imagine.The only time there are ''issues'' is when using the incorrect strain relief/wire combination. And they aren't intended to be installed with ordinary pliers.
Click to expand...

My knowledge of them begins and ends at the things I've worked on over the years. I don't think I've ever seen anyone talk about them or discuss variations for different applications. They appear to be so generic that they're all equal, from my perspective.

You can invest in a pair of Heyco pliers if you do a lot of this type of work,or just buy a generic ''strain relief bushing assembly tool'' from some cheapie tool store:
Click to expand...

That would certainly help. I didn't know such a thing existed. I never thought pliers were the intended tool to use, it's simply the best I could do. I didn't know there was something that could be purchased outside of what a manufacture might use when they assemble thousands.

The video made it look pretty easy.... with one caveat. The removal appears to require access from the inside, which will be a clearance problem in my situations.
 
Goodwill_HiFi said:
I've always hated them. The can fit sloppy, or they can fit supper tight. If tight, they're a pain to remove and a pain to install, and get marred up with pliers. Sometimes they can be removed and installed without marking them up, but that seems to be the exception in my experience, not the rule.
Click to expand...

I used to hate them. Until I finally bought a Heyco #29. Makes strain relief R&R a breeze.
Otherwise, a spiral tapered millwright's reamer works wonders.
 
As just reminded by the OP, let's just stay on original topic and keep a cool head - it is easy to misinterpret comments from others when online so please give some latitude for understanding.
 
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