Well its probably a m22.5 x1.0

big threads like that are made to suit the purpose so no standard form was used

A long time ago one of the many students in company where I worked was advised to come and see me as he had a problem identifying a thread on a Honda motor cycle and I was into bikes. the thread was around 12 mm and the pitch was really odd ,not in any engineering thread tables,so I contacted a tap and die supplier, to be informed that it was quite common to find odd threads on Hondas and other far eastern products.Around the same time a friend had a gearbox bearing fail in a Dihatsu 4 wd ,similar reply from local bearing supplier ,thats off a Dihatsu only available from a dealer and will cost an arm and a leg. I wonder are the manufacturers being devious,and they can supply spares at high prices, or has a designer come up with the correct specification for the part in hand and the parts are made in such high volume that variation from standard does not increase manufacturing cost.

On topic, I hope.

I have recently unearthed a 'Rotozip' drill/sander/polisher W.H.Y. kit and the collet closing 'nut' is missing. Difficult to measure, but the thread appears to be 28 tpi and diameter 1/2". Zeus doesn't list anything matching. Does anybody know what it would be ?

rgds

Bill

When Mitsubishi took over the Chrysler factory in Australia and set about instituting Just In Time JIT supply lines it became known as NQIT — Not Quite. In Time.

Hi all, when I was a young apprentice I campaigned a150cc BSA Bantam & when it became time to dismantle the engine I was struggling to remove the flywheel of the Wipac flywheel magneto having a boss with a large fine thread on the outboard end to accomodate an extractor, I consulted with the foreman of the toolroom where I was working as he used a 175 Bantam as a ride to work bike, he took me to the place where they made large steel hydraulic pipework & picked up a couple of large conical nuts, one then placed a 5/16 plain washer on the last diameter of the crankshaft screw the nut onto the large thread snugged up to the washer then 1 clout with a brass hammer & the flywheel was off! , so if a thread exists you can usually find something ready made for a one off job like the one described above. PS later I learned that you could make all sorts of interesting things for yourself in a large machine shop with an attached toolroom, who knew?

BobH

The use of 'specials' is not uncommon on machine tools either. For example the thrust bearing on the rear of the spindle on a South Bend 4 1/2" is of 'odd size' but by grinding out a standard ball thrust race by (IIRC) 0.010" it will fit the spindle. Came across the same in an Atlas pillar drill. The Atlas bearing was a really odd size but I found a Peugeot wheel bearing that would fit with an inner bush to accommodate the inside diameter.

The SB was my first lathe! A 14th birthday present to me from my father. It was from a Tank Regiment LDU mobile workshop – he found it in a scrap yard and paid 25/- for it including the motor. I've still got it along with a couple of other lathes as I'm really attached to it. It is currently under refurbishment – having just had the bedways reground – next job is to mill the saddle ways and tailstock to correct the wear on them.

A word of caution – early Japanese metric screw threads may be of a Japanese 'fine' form which is not compatible with ISO or SI metric form. I believe the use of this Japan standard was in use up until the 1980's on very limited areas in the motorcycle and automotive trade.

editted for spelling mishtaks

Edited By Oily Rag on 30/06/2020 20:32:34

Thank you, Jason – looks to be what's needed. Don't understand why I didn't pick that up in the Zeus.

rgds

Bill

I was never bothered by those screws. The local Honda emporium used an impact screwdriver but I found (for most screws) a tap, with a flat punch, on the side of the screw head allowed easy removal. Some countersunk screws (on the contact points and oil ‘filter’ covers?) remained a problem, for first removal, as I recall, but not when once removed.

Some of my screws did show that treatment after several removals but the surface treatment was good and the only evidence of removal was a small flat on the side of the screw head at most.

Likely a proper tool – a shaped brass drift – would have been better and would likely not have left any marks at all, but my solution was improvised by a teenaged non-engineer back in the 1960s. Steel hammer and punch were the tools available.

Edited By JasonB on 01/07/2020 06:57:48

For a long time, French cars, certainly Renaults, used a TACL screw head, a sort of enclosed diametral slot, with a small central female spigot. At least a narrowed thick conventional screwdriver would deal with those.

Then the continental motor industry started using Torx heads on cylinder head bolts..

To retain aftermarket exclusivity some manufacturers used really odd fixings. The governor shaft on the Bosch EPVE was retained by three sided fixings (Guess what was the only place you could buy a socket to fit? )

I came out of a meeting with a potential fastener supplier, having just said "Nothing special, we don't want five sided heads" to find a Japanese cartridge type injection pump with five sided heads!

Presumably all in the name of tamperproofing; or exclusivity?

Howard

The threads on japanese motorcycles are metric.

M4 x 0.7

M5 x 0.8

M6 x 1

M8 x 1.25

Anything above m8 will have either a 1mm or 1.25mm pitch.

The diameters of all threads will be a nominal size, so allowing for clearance/wear/damage etc a thread od not measuring a whole number will probably be the next highest whole number.

If you want to measure the pitch measure across the tops of 5 or more threads then divide the measurement by the number of threads.