REVERSE ACTION 14mm spark plug thtread chaser

Hi all,   Merry Christmas to all,   am needing a REVERSE ACTION 14 mm spark plug thread chaser, the rotavator  that has just been given to me has a damaged spark plug thread,  the engine is a small 2 stroke that is headless so a usual heli-coil type would mean risking swarf possibly dropping into cylinder,   has anyone used this type in the past and do they work ok, the thread at base of the hole looks ok it seems to be the top 2 or 3 that are damaged.   I have found them on that auction site and Amazon but as said do they work before I purchase one.  Or has anyone local to me,  [near Durham City ], got one that  I could  bring rotavator to you to get job done, as it fits into car boot easily.  

Regards, Don

Smother your tap with grease, your not going to remove much so it should come out with the grease.

Maryalice

maryalice wrote:Smother your tap with grease, your not going to remove much so it should come out with the grease.

Maryalice

As a Reverse Action thread chaser starts from the bottom of the thread not the top and with it being Anti Clockwise to turn it out of threads swarf will come out at spark plug fitting point, but I intend to do as you say in fitting grease, as per video on u tube.

I've never used or seen this type of top and don't understand how you screw it in without deforming the thread so that it can cut on the way out
Maryalice

Maybe I've misunderstood (or I'm being thick - always a possibility!) but if you have the barrel off, can you not just use a normal tap and check for swarf afterwards?

maryalice wrote:I've never used or seen this type of top and don't understand how you screw it in without deforming the thread so that it can cut on the way out
Maryalice

https://www.toolstoday.co.uk/sealey-reverse-action-spark-plug-thread-chaser-14mm?msclkid=b3016f768dd91c5535540afc4b5d7cb1

Woodsman,   Paul, yes I could take the cylinder barrel with head off but this would mean removing the engine unit as a whole from the machine to be able to do as you say, but as this rotavator is getting along a bit in age so if any parts are needed am not sure if they could be obtained so thought sorting the damaged thread was the easiest way to have it in usable order, the person that I had it from tried to fit a new  spark plug damaging the top few threads while fitting it, other that this problem it was in good running order,  so shall be visiting Toolstoday site after holiday period,                Mattblack,   thanks for the heads up did not think of looking there for one.

Maryalice, every day is a learning day.

Ah - understand.
Nice one Matt - I'll make a note of that.

Having read this post a couple of times now and looking at those thread chasers,
I have an option, how big is the rotovator, can you turn the engine on it side so its near upside down and tap the first few threads, along with the grease you plan to put on, nothing will fall in the cylinder then.

chrismac wrote:Having read this post a couple of times now and looking at those thread chasers,
I have an option, how big is the rotovator, can you turn the engine on it side so its near upside down and tap the first few threads, along with the grease you plan to put on, nothing will fall in the cylinder then.

Chrismac, thank you for the suggestion, I have one of these reverse action thread chasers on its way to me, but it will always be a handy item to have in my tools chest even if it will not do the job, as at the moment I do not know how much of the tool will be inside the cylinder to start the process of re-threading as the plughole is not in centre of cyl. head top it is approx 45 degrees to top, so with piston at stroke bottom it is just a guess as to how much room I have to get the tool inside to start process especially if it a deflector type piston.

The rotovator is a Mantis on its ID plate is manufactured 2003, spares are still available from China but having searched for its model number as on the plate none of parts for the model number are showing, I have advertised local to see if anyone could do a Heli-coil repair but up to now no replies by doing as you suggest, so if all fails your idea looks like it will be my next move once I get a Heli-coil tool set.

Wishing everyone a healthy and happy 2024.

There are a few points that worry me about this tool.
How do you know that you have expanded the tool to the correct dimension of the thread, how do you know if the tool is parallel with the original thread and finally how do you know you haven't started a crossed thread.

Maryalice

Hi all, just an update about this small garden tiller that was donated to me short while ago, it was complete but had not been used for a good while plus the spark plug thread in the cylinder was damaged due to plug being fitted cross threaded.
Well a Reverse Action thread chaser was bought to give it a try to reclaim the thread, with the alloy engine being headless, I.E. like some Villiers Midget 2 stroke engines, this tool works as title says in reverse to normal, and it did, after purchasing a new carburettor for the immense amount of £13 inc. delivery the engine fired after a squirt of carb. cleaner in air filter housing only ran a few seconds but it ran, after fitting a new diaphragm that came with new carb. old carb. still insitu,  and half ltr.  of 2 stroke fuel in the petrol tank it runs ok but will have a bit tuning to do to carb. as it is well varnished with standing.  So veg. plot will be getting its first attack when it is not so wet.

Don