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weirdbeard 02-02-2009 04:07 PM

Piston ring file?
I just would like to know what most of you use for filing your piston rings to achieve the proper end gap. I am finding very little info on the subject, which is weird because it seems very important now that I understand it.

I have searched all the local parts stores and cannot find a piston ring file/grinder.
I could order one of the small hand crack grinders, but it is pricey and looks like it would be easy to build if I knew what grit to use. Also I only need to file 4 rings!

I also bought a small hand file that is for cleaning points type ignitions. I may try that, but I wanted some input from you guys first.. These are wisco rings for a V twin and a not cheap. I want to get it right the first time..

Thanks. ;)

SSedan64 02-02-2009 04:20 PM,2915.html

CNC-Dude 02-02-2009 05:43 PM

The Speedway ring filer may seem expensive to you, but it will keep the filed edge square, which is important. Doing it by hand with a hand file,if you have never done it before, you can trash a set of rings in a hurry by the gap not being square. Also, file away from the outer edge toward the inside of the ring. You can chip a moly coated ring easily if you file from the inside out :nono: Also you will likely raise a burr on the top edge(flat) of the ring and bottom side, so with your hand file,gently knock the burr down before installing it onto the piston :thumbup:

weirdbeard 02-08-2009 02:47 PM

Ok thanks for the replys guys..

If I could buy that lil hand crank grinder locally I would have bought it already.
I was just wondering if thats what everybody uses.

It is really amazing to me how little info I can find on piston ring end gap filing. Anyone that has built up an engine has done it right?
Nobody uses hand files? :confused:

CNC-Dude 02-08-2009 03:14 PM

Unless you build more than several engines a month, many people might no invest in a crank style filer. Doing it with a hand file is very time consuming. And if you need to file a set of stainless rings, its very tough to do it by hand. I have a motorized ring file, and it can still take upwards of 45 minutes to do a set,depending on how much material you have to remove. That of course is a set of "file to fit" rings, not a set of .030 over rings for a .030 over bore, where very little might need to be ground off if any.

weirdbeard 02-08-2009 03:26 PM

Thanks CNC dude.
If I was building a V8 I would not want to hand file all those rings, but with my Harley we are just talking 4 rings to file. I don't mind if it takes a while. I could still do it faster than it would take to get the hand crank grinder shipped to me.

I am looking all over for the proper technique for hand filing piston rings, but I can't find anything at all. I know to file toward the inside of the ring and that's about it. I can't even find the proper hand file for this job! :eek:

CNC-Dude 02-08-2009 03:31 PM

Just get a smooth pattern file, not a course one. Go to a hardware store and look at them, and lighty run your finger across the surface on them. Something that feels about the same as maybe 320 grit sandpaper, not 60 grit.

richard stewart 3rd 02-08-2009 07:32 PM

Hi weirdbeard,
Looking around I found that Mancini's ring filer uses a 120 grit wheel. I also found conflicting statements,
one said if you need to take like twenty thousands off, you take ten off each end, the other said never file both ends?


weirdbeard 02-08-2009 07:48 PM

Really.. 120 seems course to me.. :confused: Maybe not.. I have never filed a ring. ;)
About rather or not to file both ends.. That was another question have.. I just can't find good info on the subject. The grinders look like you pinch the ring on the grinding disc and it takes material off both ends, but I don't know that. It might just be abrasive on one side. :rolleyes:

CNC-Dude 02-08-2009 08:48 PM

You will just grind off of one side of the ring! Doing it off both sides doubles your chances for getting the gap crooked. Also, make sure the ring sets square in the cylinder when you are checking the gap. I usually make a ring squaring tool for the bore size I need to do this so you can stay consistent each time you insert it into the cylinder....

bentwings 02-09-2009 12:27 AM

Get a nice new 'smooth' or 'mill' file. Teeth on both sides but not double teeth or diamond cut. Chuck the file in a vise and grasp the ring by both ends and gently stroke against the grain on the file. It will cut both sides evenly and parallel.

johnsongrass1 02-09-2009 01:07 PM

Done it that way a few times, Works good too.

weirdbeard 02-09-2009 03:48 PM

I think I will try it that way.. I like the idea of locking the file in a vice and working the ring on it that way. ;)

jimfulco 02-11-2009 04:07 AM

I did a few sets of VW rings with a 8" mill bastard file in one hand and the ring in the other, leather-gloved, hand. Deburred with a small sharpening stone.

Intense RT 03-24-2010 11:03 AM

I know it's an old thread but feel I can put this out there to help those who haven't done this. I don't have access to a shop and the "right" tools so I proceeded to look for any ideas on ring filing by hand and maintaining a square edge.

To add to the thread: I don't see how clamping the file in a vise and cutting both ends at the same time would keep the ends squared to each other. The thickness of the file would prevent this. May be "acceptable" if the file was only ~.020 thick. When you put the ring in the bore the end at the cyl wall will be tighter than towards the piston. ....Unless you're running a gap the thickness of the file. which I doubt.

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