Locating a particular threaded die

[peweuk]

I am trying to locate a die to cut a thread the same as that used on my cars (a Lexus) towing hook.
Apparently all car manufacturers use different threads and not even the Lexus dealers can tell me what thread is used on mine.

Using a caliper I have measured the thread diameter and pitch and conclude it is probably an M18 thread with a 3mm pitch.

The problem is that I cannot find a die of that spec anywhere and wonder if any of the engineers visiting this forum might be able to assist.

Any suggestions welcome.

 

[Burnerman]

Just thinking about the various tow bar bolts that are readily available ......could that sort things?
John

 

[peweuk]

Just thinking about the various tow bar bolts that are readily available ......could that sort things?
John

Not really John.
I cannot get a towbar for my car (only ever made in the US), so to add a Tricycle rack I need to use two long bars which are inserted into the tow bolt holes and then on to which I place a (homemade) tricycle carrier.
Unfortunately the standard bolts aren't long enough.

Here's and example of what I am trying to achieve - albeit this is on a Smart car -

 

[Burnerman]

Ok, that's a bit clearer. Could you buy a couple of genuine towing eyes from Lexus and modify them by welding, perhaps?
John

 

[Tigercubrider]

If you can find a decent machinist they could turn a couple of longer bolts from hex bar rather than using a die that's made from unobtanium.

 

[CBW]

Not sure if this is any good? Haven’t watched the vidoe https://www.machinemart.co.uk/p/cht...MIgtW-uuaf6AIVmpntCh2HdQYzEAQYBSABEgLW2vD_BwE

 

[Lower]

Most Japanese manufacturers use metric threads and towing eye bolts are normally standard items. The towing eye is unlikely to anything other than a standard m18 coarse thread which has a 2.5mm pitch

 

[peweuk]

Ok, that's a bit clearer. Could you buy a couple of genuine towing eyes from Lexus and modify them by welding, perhaps?
John

- At £50 a pop they are very expensive, at a push if I find no other solution I could try and get a couple o second hand ones - but they are still going for £15 + plus postage.

If you can find a decent machinist they could turn a couple of longer bolts from hex bar rather than using a die that's made from unobtanium.

- We are in West Somerset and there are no machine shops within the area

Not sure if this is any good? Haven’t watched the vidoe https://www.machinemart.co.uk/p/cht...MIgtW-uuaf6AIVmpntCh2HdQYzEAQYBSABEgLW2vD_BwE

- Those in the link only go to 12mm - !8mm are close to £200 and it does not specify the pitch.

Most Japanese manufacturers use metric threads and towing eye bolts are normally standard items. The towing eye is unlikely to anything other than a standard m18 coarse thread which has a 2.5mm pitch

- When I measured the pitch on the Lexus ones it is definitely over 2.5mm but I will try and find someone with a Japanese car and see what they have.

I am thinking that I may have to go with 'Burnermans's' option and find a couple of second hand eyes then cut them and drill a hole drill and tap it, then have a bar threaded and inserted and welded - but I will still have to try and find a machine shop to do it.

Wouldn't have thought something so simple would be such a problem to achieve

 

[Burnerman]

As Lower has said, the pitch of an 18mm thread will be either 2.5mm (metric coarse) or 1.5mm (metric fine).
Being able to find a die stock to turn such a beast would be difficult, I think but 18mm threaded bar is readily available.
All towing eyes I've seen have had coarse threads and often quite slack when connected - maybe that's to allow for a little corrosion!
John

 

[cdbe]

If the holes go straight through just use a smaller diameter bolt eg M12 with a nut on the back.

 

[Burnerman]

Just thinking - if the thread was 3/4" diameter UNC, the thread pitch would be quite a bit closer at 10 tpi.
A Lexus website forum mentions 18 x 3mm pitch - don't know anything about that one!
I go to a branch of Thomas Potter so sort out oddball things like this.
John

 

[peweuk]

I hear what you say - BUT

Yesterday I found a forum where a guy wanted to use his tow hook bracket for a support to take the extended length for a Kayak on his roof rack, and he says he found the thread was 18 x 3.
Also - have a look at the two attached photos showing callipers set to 3 threads

- at 2.5mm (7.5)



-and 3.mm (9)



I am now trying to find some 18 x 2.5 bar locally to check it out just to try and confirm one way or the other.

Coincidentally, I had an e-mail from Lexus in response to a query I sent their head office a while back - they said they would get back to me shortly with the information (I won't hold my breath though).

 

[Stivino]

What about getting your hands on a thread gauge or going to a machine shop that is likely to have an appropriate thread gauge?

 

[Tigercubrider]

I would have thought that any agricultural engineer would have a set of metric taps and dies in large sizes?
I googled "Somerset machine shop" and loads came up.

BE AWARE a couple of sites that have come up indicate that it may be a LH Thread

 

[peweuk]

Most of the machine shops in somerset are over an hour from us, but closer to home I did find a small car mechanics workshop with machining facilities who may be able to help - but they are closed for a couple of weeks.

I also found a chinese seller of Lexus tow hooks on ebay. I e-mailed them to ask if they would confirm the size of thread they used as I had been told it is M18 x 3.

This was their reply -
"We have lots of different threads. Specifically this one - 8G clockwise.
Thread 8G means 8 coils to 1 inch. It is very close like 3 mm to 1 cm
It is not a metric measurement! All measurements of this hook are in Inch. Thread approx 18mm x approx 3 mm."

Which is even more confusing as I cannot find a reference to .7" thread with 8tpi anywhere.

So it looks like my best (and most certain) option is to get a second hook from somewhere and have that and my original cut and welded.