Open rubber grommets for machine refurb

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Claire L

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Hi guys,

I'm currently working on an old fobco bench drill. I have the thing stripped and ready for filling the castings (which arent too bad actually, but thats by the by) anyhoo, I would like to source a few replacement cable grommets for the side of the casting as the originals are in pretty poor shape. A quick measure would suggest they are 1/2" chassis hole diameter and 5/16" panel thickness. No end of searching the internet has proved fruitless with most suppliers only going up to 5.5mm panel thickness. I dont suppose someone may know of somewhere to source said grommets or their metric counterparts would they?
 
try googling ht lead grommet

Claire, if you PM me I can send you some pics of some grommets that I have just found in the shed that might fit(depends how many you need though, i dont have a lot)
 
Lidl sell mixed cases of them every now and then
 
If this is a "back to 100% original" refurb, this will be no help, but if it is solving a practical problem, I have three suggestions:

0. Use a cable gland instead: These are probably still easily available in imperial sizes, and will accommodate the thickness you need. If you don't want it visible, put it in with the strain relief part inside the box.

1. you can get various forms of grommet strip. This is U-section strip, either of rubber or nylon (mine is the latter), and sometimes with a serrated edge (to the panel side), to grip holes better. Use is pretty obvious - you work out the circumference of the hole, and subtract a tiny amount, then cut to length and push-fit. It comes in various sizes for different panel thicknesses.

2. Heatshrink and Hellermann sleeves: both of these do the same thing: thicken the insulation round the cable, both to add protection and some strain relief where it terminates.

Hellermann sleeves are rubber and extremely good, and go to pretty large diameters as they are used industrially, but you do need the fitting tongs. They have the huge advantage that you can often get them over connectors, so they can sometimes be retro-fitted to cables that are already terminated. They are reasonably heat-proof (they come from the days of valve electronic equipment, I think), but can perish, and being a natural material (I think), can be affected by chemicals. They come in a range of colours too, which is very handy.

Heatshrink, most people know. Bright colours are available, including white you can write on, and clear, and a range of sizes. There is a variant with a sealant inside, which oozes when heated so it really bonds to the cable, but it does make it very rigid.

In both cases you can stack them over themselves on the cable, making a thicker cable or tapering where it goes into a connector or through a grommet.

I think heatshrink is easier to use, but not as effective in providing strain relief as it's not anything like as flexible as Hellermann sleeves. But combining one or the other with grommet strip might get you what you need.

Finally, consider applying a countersink tool, gently, to the edges of the hole, to reduce the metal thickness slightly and take off any arris round the rim. This will help prevent chafing, and might even let you use a grommet intended for slightly thinner material.

By the way, use of cast metal boxes for industrial electrics and telecomms electronics is still common, as the metal can form a waterproof heatsink, and it's an aluminium alloy, doesn't corrode as easily as steel. As a consequence, glands and grommets are also available, although I'll admit 5/16" is thicker than usual.

HTH,

E.
 
Thanks all for the advice,

Eric I'll look into the options you suggest and if all else fails then a cable gland is a good suggestion thank you and I've never used (or heard of) hellerman sleeves so will definitely look into those more.

Flying haggis, I'm terribly sorry but I can't pm yet as it appears as I've only just registered it's restricted until I post more.
 
Possibly stating the obvious, but a well known source of bits like these is RS Components.
 
I would choose a cable gland over a grommet, but if you can't find anything long enough to suit the thickness of your casting, google "brass male bush" these are cheap and common in 20mm diameter and would "soften" the edges of a hole as an alternative to a grommet.
There are slim nuts to match so you only need a plain hole, not a tapped hole.
Heatshrink around the cable for extra protection against rubbing where the cable passes through.
Pop a couple of larger cable ties around the cable inside the casting to resist pulls on the cable straining the connections inside.
Being brass and having been around a long time, this method would look pretty traditional too.
 
Thanks all really appreciate the advice. I managed to get the main castings primed at the weekend so once I've picked a main colour I can sort the cable gland.
Thanks again

Claire
 
Sorry to jump in with a bit off topic drift. I agree about the Hellermann sleeves (and the 3 prong sleeve expanding tool) because I used them years ago in the RAF. I've never seen/used them since, but can well imagine they'd be very expensive today - and don't forget you really need the "Hellerine" fluid too (a clear slimy liquid in a bottle to lubricate the sleeve as you slide it over the cable with the 3 prong tool) - but I guess a softened soap would do, which is what I use to persuade tight heat shrink sleeves on.

But sorry, a synthetic wine cork instead of the 3 prong sleeve expanding tool?? I'm probably daft (delete the "probably" if you like) but how would that work? I just can't picture it right now. How to modify the cork, how to use it? Any help please?

TIA
 
AES":1utjj4p5 said:
Sorry to jump in with a bit off topic drift. I agree about the Hellermann sleeves (and the 3 prong sleeve expanding tool) because I used them years ago in the RAF. I've never seen/used them since, but can well imagine they'd be very expensive today - and don't forget you really need the "Hellerine" fluid too (a clear slimy liquid in a bottle to lubricate the sleeve as you slide it over the cable with the 3 prong tool) - but I guess a softened soap would do, which is what I use to persuade tight heat shrink sleeves on.

But sorry, a synthetic wine cork instead of the 3 prong sleeve expanding tool?? I'm probably daft (delete the "probably" if you like) but how would that work? I just can't picture it right now. How to modify the cork, how to use it? Any help please?

TIA
I think the intention is to make the grommet out of the cork, not to use the cork to expand the sleeves
 
Claire, there's a UK company called Banbury Plastic Fittings who do all sorts of such stuff (and a lot of other useful "small plastic stuff" too). I found them through this Forum and have found them to be excellent - usual disclaimers.

Try Googling something like bpfonline.co.uk or something similar (I can't find the exact link right now, sorry).

HTH
 

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