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Broken Mazzer body thread fix advice

Postby claypriley on Sat Jul 09, 2011 4:18 pm

Hi, I got hold of an old '97 Mazzer Major (Rio badged) for $250. I am sure it is an old SB grinder 'cause there was a sticker on it that said so........ Anyway, it has a bit of a buggered up thread in the body casing threads where the burr carrier threads the top burr. It got shipped poorly and part of one of the threads about 1 1/3 turns in, is a bit broken(i.e., the peak of the thread snapped off for about 1"....... the groove or valley of the thread is still there). Unfortunately this is right where the gap for the spring is, and so when I tighten the burr carrier(counterclockwise), it feels like it gets tight right at the bad thread and doesn't want to cross the spring gap into the continuing same thread path. I don't want to force it, and bugger up any more of the threads...... I am wondering if anyone else has had to clean up some threads that were broken or crossed...?? and what they found out worked. The threads on my machine are not crossed, and I want to avoid that by not forcing the carrier when it gets tight.

I have marked where the threads begin on both the carrier and the body, and that is how I came up with 1 1/3 turns in. I have used a small triangular file to delicately "clean-up" what is left of the thread where the peak has broken off.
Anyone have any experience in a thread fix like this? I know it is fixable, it is only a small part of the thread circumference.

thanks in advance, Clay
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Postby JohnB. on Sat Jul 09, 2011 6:40 pm

An internal thread file would be your best bet for cleaning up the damage without making it worse.
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Postby DJR on Sat Jul 09, 2011 11:46 pm

If you can get a lathe tool bit shaped for threading (60 degree angle), and if it is very sharp, you can gently follow the threads and clean them up. I don't think that (as far as I know) there is an internal thread file with very fine threads, which I think I recall the Major has, and they're probably metric at that.

Here's a link to some cheap tools for the job, though I would just use a carbide 60 degree tool, sharp, or a high speed steel one and gently go over them.

http://www.jtsmach.com/jtswebshop/Taps_Dies/T224.asp

If you get a thread file and it's the wrong TPI, you'll ruin the part.
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Postby JohnB. on Sun Jul 10, 2011 8:06 am

DJR wrote: I don't think that (as far as I know) there is an internal thread file with very fine threads, which I think I recall the Major has, and they're probably metric at that.


A quick Google search turned up a number of Metric internal thread files/restorers with a variety of thread pitches.

The external thread file in your link would be useless for the internal threads on the body casting. The combination thread file in the link below with the internal files on the end would allow the user to work side to side & properly seat the file in the threads.

http://www.thepartsbin.com/cartools/spe...nal-d.html
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Postby claypriley on Sun Jul 10, 2011 9:31 am

Thanks you guys for the advice. I will check out those websites and tools and see what I am able to do. I will let you know how it goes. The broken part of the thread is so little, I am sure if I can just clean it up a bit, the burr carrier adjustment threads (brass) will be able to do the rest of the alignment. Again thanks for the advice and information. I am wondering if the little triangular file I was using is 60 degrees since the file looks like an equilateral triangle.....?
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Postby ANeat on Sun Jul 10, 2011 9:33 am

Just get a thread file like this, it needs to have the ends like pictured, not all thread files will have this feature.

The lengthwise grooves are for external threads and the ends are for internal.

The ideal solution would be a tap really....

Image

Image
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Postby claypriley on Sun Jul 10, 2011 9:54 am

Wow! Nice pictures of the thread restoring file!! Do I still need to know the tpi for ordering the right file? or it looks like the file covers a variety of fineness/coarseness of threads. I will go measure the threads per inch on the body, there is a half an inch or more to measure from.
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Postby erics on Sun Jul 10, 2011 10:05 am

The pitch on those threads in the Mazzer is 1.00 1.50 mm. Pics of your "problem area" would be helpful and a google search as suggested by John B. would work wonders.

Do a HB site search for author = jpboyt . I do believe he has "in-his-house" capabilities to fix your thread situation.

edit - 7/13/11 - As I was corrected later on in this thread, the pitch of the threads for the Mazzer Major is 1.50 mm AND NOT 1.00 mm.
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Postby claypriley on Sun Jul 10, 2011 10:27 am

I just counted 8 peaks in 1/2". This is about all the threading that there is, either on the adjustment ring or in the body itself. So would I be right in thinking it is 16tpi??
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Postby claypriley on Sun Jul 10, 2011 10:29 am

Yes, I will take and post a picture today of the thread that is broken.
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