Author Topic: rethread broken brake nipple?  (Read 883 times)

Offline redrider90

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rethread broken brake nipple?
« on: June 27, 2022, 11:17:14 AM »
I have an F09 caliper on the front right on my Mille. I love the stopping power of it over the stock F08.
It came with 2 6mm bleeder nipples: one on each side of the caliper. Many many years ago my wrenched slipped and I broke one nipple off. I carefully tried an ez out extractor only to break it. After a long period of illness unable to ride my bike. Although I started it every few months and began working on smaller issues I am now improving well enough to try and ride again. I wanted to raise the handlebars as my days of leaning over hard are gone. I had not attended to keeping the other nipple rust free all these years and hence I was faced with a rusted 6 mm nipple. Why did they use a puny 6 mm? Anyhow after much soaking with Kroil oil I very carefully attempted to slowly loosen it. I thought I was seeing progress when as it was moving ever so slowly back and forth using a small wrench.  But Murphy bit me and I was work hardening the nipple as it broke off. No more ez out for me.
I now have a clear channel that I can drill down carefully too open for rethreading a new nipple.
Any thoughts on should I drill out with the proper drill size ad try to rethread it for a new 6 mm nipple. Obviously careful to not damage the seat. Or should I drill out to a larger size nipple and thread it for say an 8mm nipple.  I have never had an 8mm nipple seize on me.
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Offline Kiwi_Roy

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Re: rethread broken brake nipple?
« Reply #1 on: June 27, 2022, 11:37:02 AM »
you told us several times you have never had an 8mm nipple seize so I guess there is only one way forward.
Good luck.
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Offline redrider90

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Re: rethread broken brake nipple?
« Reply #2 on: June 27, 2022, 11:51:23 AM »
you told us several times you have never had an 8mm nipple seize so I guess there is only one way forward.
Good luck.

maybe I should not say I have never had an 8mm nipple seize on me.  :clock: Maybe that is just a matter of time.  :grin:
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Offline Frenchfrog

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Re: rethread broken brake nipple?
« Reply #3 on: June 27, 2022, 11:55:01 AM »
At this stage of the game I'd go to a reputable workshop and see if they do spark erosion.

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Re: rethread broken brake nipple?
« Reply #3 on: June 27, 2022, 11:55:01 AM »

Offline fotoguzzi

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Re: rethread broken brake nipple?
« Reply #4 on: June 27, 2022, 11:58:18 AM »
Left hand drill bit?
Or new caliper from MGcycle go for about $150.
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Offline Stevex

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Re: rethread broken brake nipple?
« Reply #5 on: June 27, 2022, 12:26:37 PM »
If it was me I'd drill the bleed nipple down the centre with a drill the same size as the nipples inner thread diameter. Maybe then it'll be possible to use a scriber to get the thread remains out. Won't help with the ez out though, only a spark eroder will get rid of that.

Offline lucian

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Re: rethread broken brake nipple?
« Reply #6 on: June 27, 2022, 05:02:46 PM »
I love these little bleeder repair kits , come in various sizes and have a brass NPT seat so no worries about destroying the seat when drilling,  You could probably find a core bit that would drill right around that hardened mess in the center.


Offline Canuck750

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Re: rethread broken brake nipple?
« Reply #7 on: June 27, 2022, 06:54:44 PM »
In my experience its very hard to get a broken nipple out of a cast aluminum caliper body. The steel nipple is usually so corroded that most measures fail to remove it.

Next time you have a stuck nipple in a brake caliper put the caliper in a vice, place a box end wrench of the correct size over the nipple, take a brass hammer and slowly and without too much force tap down on the top of the nipple, over and over while applying slight pressure to the wrench, eventually the nipple will come out but the nipple will be junk by the time you are done.

I have tried clamping the nipple to a mill table and drill down the center then tap the aluminum caliper, you have to be dead center in the drilling and tap. Results were not satisfactory.

Spark erosion, if you can find a local shop that is reasonable, is probably the best bet but will probably cost more than buying a new caliper.
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Offline redrider90

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Re: rethread broken brake nipple?
« Reply #8 on: June 27, 2022, 09:26:19 PM »
Left hand drill bit?
Or new caliper from MGcycle go for about $150.

The 2 versions of F09 that MC Cycle carries will not fit the right side behind the axle caliper on my Mille. At least that is how they advertise it.
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Offline redrider90

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Re: rethread broken brake nipple?
« Reply #9 on: June 27, 2022, 09:38:41 PM »


Next time you have a stuck nipple in a brake caliper put the caliper in a vice, place a box end wrench of the correct size over the nipple, take a brass hammer and slowly and without too much force tap down on the top of the nipple, over and over while applying slight pressure to the wrench, eventually the nipple will come out but the nipple will be junk by the time you are done.


This sounds like I wish I had thought about that when I had the caliper in the vise slowly working it with a box small wrench but I still ended up breaking it off. I have tapped on stuck bolts while applying torque to bolts that are tight but didn't think of trying it on a nipple.  I would gladly have trashed the nipple and bought a new one if I had this idea at that time. I did manage to reinstall the caliper and bleed the air out of the caliper and brake line by slowly taping the caliper with a rubber mallet while I slowly repeatedly  pulling on the brake handle. It took a bit to slowly get the air out but it worked. But I really need to fix it.
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Offline redrider90

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Re: rethread broken brake nipple?
« Reply #10 on: June 27, 2022, 10:16:48 PM »
I love these little bleeder repair kits , come in various sizes and have a brass NPT seat so no worries about destroying the seat when drilling,  You could probably find a core bit that would drill right around that hardened mess in the center.



The one photo you posted is not for a 6mm nipple. It's a great design.  I will look and see if I can find one smaller. I am not sure there is enough room to drill out for even a smaller diameter NPT. Even as I think of going to an 8mm I am concerned about how much material I have available without weakening the caliper in that area. That is maybe why they used a 6mm:
Red 90 Mille GT

Offline Frenchfrog

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Re: rethread broken brake nipple?
« Reply #11 on: June 28, 2022, 03:05:02 AM »
Pretty certain that those inserts will be too big for the caliper.If they do go in then there will be scant material left to hold them IMO. As I said earlier better to try spark erosion even if it's expensive .Or maybe do a pilgrimage to the sacred site of your choice prior to further attempts...

Offline jamesb

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Re: rethread broken brake nipple?
« Reply #12 on: June 28, 2022, 03:15:07 AM »
i dont know what size easy-out is broken but saw a siilar problem on another site and the chap resolved it by drilling with one of these https://www.ebay.co.uk/itm/134101140059?hash=item1f390d025b:g:C-UAAOSwfwphHjiZ lubricated with water and kept taking small bites at it.may be worth a try?

Offline huub

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Re: rethread broken brake nipple?
« Reply #13 on: June 28, 2022, 04:59:12 AM »
if you slightly damage the seat not everything is lost,
 drop in a small ball from a ball bearing and shorten the nipple.
the ball will close the hole.
some grimeca calipers came like that from new.

Online cliffrod

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Re: rethread broken brake nipple?
« Reply #14 on: June 28, 2022, 06:23:01 AM »
i dont know what size easy-out is broken but saw a siilar problem on another site and the chap resolved it by drilling with one of these https://www.ebay.co.uk/itm/134101140059?hash=item1f390d025b:g:C-UAAOSwfwphHjiZ lubricated with water and kept taking small bites at it.may be worth a try?

I use diamond saws and core bits regularly for both intended and other uses...  The eBay link shows a tool (with diamonds bonded onto surface of tool) designed to cut soft material.  It takes very little hard material to wipe the diamonds off the tool.  If you go this route, you will be more likely to succeed by using a diamond tool engineered for hard stone and concrete that can have anything in it, with diamonds embedded within the bond & requiring the bond to be worn away to expose fresh diamond.    The bond supports the diamonds as they abrade.  You still need to water cool the cut because heating the diamonds will ruin them, but the diamonds won’t be wiped away the instant they hit hard material.

For a project like this one, this is the type of diamond core bit I would use-  https://www.ediamondtools.com/products/extended-masonry-core-bits-for-granite-marble-and-concrete?variant=7906374615070&gclid=EAIaIQobChMInr6zy4HQ-AIV4GxvBB1GsgnDEAQYAyABEgKoZvD_BwE
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Offline Chuck in Indiana

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Re: rethread broken brake nipple?
« Reply #15 on: June 28, 2022, 07:19:35 AM »
A guy brought me an airplane engine that he'd broken off an eze out in the case. I made up a steel fixture with a hole the same diameter as a carbide end mill, and plunge milled that sucker out with a hand drill..
And.. it is easy enough  :smiley: to remove a brake nipple with an eze out. The bleed hole centers the drill bit. The trick is to drill it a few thousandths smaller than the minor diameter of the thread. If you are experienced enough to know how much torque you can put on a same sized tap.. you won't break an eze out, BTW.
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Offline Mike Tashjian

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Re: rethread broken brake nipple?
« Reply #16 on: June 28, 2022, 07:39:15 AM »
If you remove your brake pads and extend the pucks you will fill the caliper with brake fluid.  Change your hose and then add fluid to mostly fill the hose as you reattach it.  Retract the caliper pistons pushing the fluid back to the master.  That should get the most of the air out. Not a repair but a way to at least ride the bike. 

Offline larrys

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Re: rethread broken brake nipple?
« Reply #17 on: June 28, 2022, 08:16:13 AM »
At this stage of the game I'd go to a reputable workshop and see if they do spark erosion.

+1. A sinker EDM machine would get that out in a jiffy, with zero damage to the caliper.
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Offline redrider90

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Re: rethread broken brake nipple?
« Reply #18 on: July 02, 2022, 04:24:06 PM »
Left hand drill bit?
Or new caliper from MGcycle go for about $150.

Looks like MG had 2 versions of F09 at MG. What they didn't know is the F09 advertised for left side front of the fork will also work if you flip it over to fit the Mille on the right side back of the fork model.  I believe this version was originally used on the front of fork T3s and maybe on the rear of early model SPs?  But the more I looked closer at MG's photos and took photos of mine I saw it matched perfectly. MG didn't believe me until I sent them my photos. So I can experiment on the old one I have and see how good I am at putting an 8mm nipple on it.  I saw a real grunge F09 on eBay for way too much money that someone had successfully tapped and installed one 8mm nipple in it. But otherwise F09s are real hard to find.
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