Broken off grease fitting questions?

[johninct]

I need to replace some broken off grease fittings on my excavator. I have to drill and tap some holes. Is a grease fitting size 1/4"-28 NF? If so, what is the correct drill size? I may have to drill some stripped out holes to a bigger size. Are some grease fittings 1/4"-27 NPT? What is the correct drill size?

 

[alfadan]

Make and model may help. I don't know what it could be, but there is a chance it could be a BSP thread (British Straight Pipe ?) or something weird.

 

[kbs2244]

they come in many threads
you get to pick one

 

[alfadan]

Take an unstuck one to the auto parts store.

 

[dfiler2]

I used to carry one of these in every tractor tool box, along with extra fittings so they could be fixed as soon as you had a problem. If I remember right I think most were 1/8" pipe thread, I remember extending a few to make them easier to get to and the parts were available at every hardware store around here.

https://www.amazon.com/dp/B0779JDQ18/?tag=atomicindus08-20

 

[charbar]

SAE sizes you usually see are 1/4"x28TPI STRAIGHT thread or 1/8" NPT.

I have no idea if they make a 1/4" NPT grease zerk. That is huge when you are talking about grease zerks. 1/4" NPT is the same size as the fittings you commonly use on air hoses/tools for reference.

1/4"x28 takes a number 2 or 3 drill bit (.221" or .213"), 1/8" NPT uses a 21/64ths or 11/32nd drill bit and a 1/4" NPT uses a 7/16" drill bit.

 

[snyder]

1/8 npt and 10/28 seem to be the most popular . An ez out will usually twist the remnants out easily.

 

[lilredex]

1/8 npt and 10/28 seem to be the most popular . An ez out will usually twist the remnants out easily.

Or, a LH drill bit.

 

[Snapped-off]

Could be metric too. M6, M8, M10. What brand equipment?

 

[NUTTSGT]

Could be metric too. M6, M8, M10. What brand equipment?

Yep, all sorts of sizes now it seems like.

Enough so that I started a zero assortment in a small clear Plano style box.

 

[dutchgray]

You can buy a thread checker specifically for all the different grease ****** threads, there are quite a lot of options for them.

 

[crewchief888]

SAE sizes you usually see are 1/4"x28TPI STRAIGHT thread or 1/8" NPT.

I have no idea if they make a 1/4" NPT grease zerk. That is huge when you are talking about grease zerks. 1/4" NPT is the same size as the fittings you commonly use on air hoses/tools for reference.

1/4"x28 takes a number 2 or 3 drill bit (.221" or .213"), 1/8" NPT uses a 21/64ths or 11/32nd drill bit and a 1/4" NPT uses a 7/16" drill bit.

ive seen a few 1/4" pipe thread zerks over the years, but they are few and far between

 

[johninct]

I used a 11/32" drill bit for a 1/4"-27 NPT grease fitting and it seemed to work out good. It is on a Cat 215 with an aftermarket thumb. I got the fittings from Cat but they didn't know the size.

 

[Hank11]

Glad you it figured out.
If they are broken off and at least flush with or above the surface, try cutting a screw slot across the end with a dremel cut off wheel. Then try a close fitting screwdriver to remove. Second attempt will involved a hammer impact driver with a good fitting bit.

 

[csp]

You can find drill bit size charts for every possible thread size/pitch on the web. Google is your friend.

 

[finn]

I had good success with a plain old ezout.

My Korean built tractor has some sort of British straight thread fittings. Frustrating when you have a stock on metric and various SAE zerks on hand.