B7100 HST Hydraulic filter thread specs?

[998cc]

As per the thread below, I ordered new filters, oil and O-rings from Messick's and began cleaning/replacement today. When reinstalling the smaller filter/strainer, the thread jammed about three threads in. After removal and inspection, I think some metal bits from normal system wear and tear were laying in the threads and caused binding. Further cleaning these out have not helped, so I fear the internal thread is is lightly damaged. I assume (spell that "hope") chasing it with a tap will cure it, but I need the thread specs. Does anyone have this info or know where I can get it?

B7100 HST Low power. Cause?

A little history. My dad loved gardening and used a TroyBilt roto-tiller until he just couldn't manage it anymore. He then bought a B7100HST package from a rental yard; it included a front loader, box scraper, FL850 rotary tiller and RCR48 mower attachment. The B7100HST had been...

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Thanks.
998cc

The filter/strainer of issue:

 

[arto98607]

I think WIX filter cross reference site will have the thread spes if you know the correct filter model.


WIX Filters - Products Catalog Home

 

[998cc]

Apologies. I should have been more clear. These are the internal filter/strainers.

I now have thread gauges. It is closest to 1.75 metric pitch but not a match. Interestingly, an American 14 TPI gauge fits very well. The size is very close to 3/4 inch NPT thread.

 

[JWR]

"Three threads in and jam" is VERY typical of a near same size metric bolt in an SAE hole or vice versa. It is ALSO typical of Metric fine threads into a std Metric hole and vice versa. I'm guessing you have one of the two circumstances. Consult with Messicks.

IN FACT for goodness sake do not use the tap and dye set until you confirm the situation !! You are almost certain cause filings with the tap. Well equipped bolt sources will have a "test threads" panel where you can try the threaded item to make sure what threads it has.

 

[998cc]

"Three threads in and jam" is VERY typical of a near same size metric bolt in an SAE hole or vice versa. It is ALSO typical of Metric fine threads into a std Metric hole and vice versa. I'm guessing you have one of the two circumstances. Consult with Messicks.

IN FACT for goodness sake do not use the tap and dye set until you confirm the situation !! You are almost certain cause filings with the tap. Well equipped bolt sources will have a "test threads" panel where you can try the threaded item to make sure what threads it has.

Thanks JWR. I'm certain the threads are the same; the original strainer will not thread back in either. It was easily removed. What apparently happened was metal shavings that had collected in the strainer dropped off in the threaded hole in the transmission case. My plan today is to use a pointed hand tool to clean the individual internal threads and try again. The use of a tap is a last resort; however, the intent is to merely chase the thread and not to re-thread. I'd still like to know what this thread really is--just in case.
998cc

 

[arto98607]

It's probably a metric pipe thread, which should be the same as equivalent US pipe thread, but is not tapered.

 

[998cc]

arto.
Thank you for the response and information. That sounds reasonable.
In any case, I was able to straighten up the internal threads and re-install the original strainer. It was a little snug initially but went in smoothly. The other strainer on the left side of the tractor went in without a problem. I carefully cleaned all of the metallic sludge out of those threads prior to threading the strainer in--sludge was the cause of the problem on the right side.

Thanks to all for the responses.
998cc

 

[arto98607]

It is probably not a metric pipe thread. There is a metric spec taperered pipe thread but almost nobody in the world uses it.
Yours will be a a British Standard Tapered Pipe thread. BSPT. That is the tapered pipe spec used almost universally in Japanese engine and machine manufacture. It is very close to american NPT for turns per inch and they will thread into one another - until they jam because the the thread shape is slightly different. (55 degrees included vs 60 degree american).


Many after market manufacturers are making their parts with NPT (instead of BSPT now) because the US made NPT taps and dies are so much less expensive. If you cannot find BSPT, use NPT knowing that it will ruin the threads for any OEM part.....and the galling from forcing will cause somethread interference and poor seal. Use a small amount of either thread tape, Permatex thread sealer or Silicon gasket sealer and a flat washer to fit under the end. Remember that this joint doesn't have to seal against pressure or much heat. It just shouldn't leak. If it doesn't leak that is good enough. .

If you want to try matching the thread or just for curiosity about the actual thread shape, you can buy thread adapters from BSPT to NPT and vice versa in almost any diameter from NAPA or even ACE hardware. Or order online.

BUT WHY NOT SIMPLY USE THE OLD ONE CLEANABLE FILTER? THAT IS SIMPLY A 200 MESH SS SCREEN. JUST CLEAN AND REPAIR IT.
rScotty

I don't recall the hydraulic oil strainer thread being tapered at least in my Kubota

 

[ptsg]

The thread on the strainer can't be tapered at all. After all, it's a banjo bolt/fitting with a big screen on the end.

 

[rScotty]

The thread on the strainer can't be tapered at all. After all, it's a banjo bolt/fitting with a big screen on the end.

That's right. Thank you for the correction. I must have suffered a brain lapse. In Japanese machines, most interally threaded holes into an iron casting use BSPT, which is British Standard Pipe Tapered. But this one shouldn't be tapered at all. My mistake.

Since the 3/4" NPT fit so well, I suspect it is BSPP - British Standard Pipe Parallel. That is also used by Japanese equipment for threading cast iron.

There may be a close metric. I'm not sure. Not knowledgeable on course metric threads.

Sorry for the confusion; I erased my previous post.
rScotty