Bolt will accept nut, but die jams from beginning

[spikelovesmetal]

Hello!
Bit of background if it helps - scroll down to the problem if you don't want to be bored!
I'm fitting engine bars to my motorbike, which involves removing two of the three original engine mounting bolts and replacing them with supplied lengths of M10 threaded rod, each of which has a nyloc fixed on to make it a 'bolt'. The rods go through one bar, through the engine mount and out of the other bar (upper fixed with a washer/nut, lower goes into a threaded section of engine bar).
The shorter 227mm (upper) rod fits fine, but the longer 327mm (lower) rod was too short by about 7mm. I contacted the manufacturer who sent out a longer 335mm rod that fits, but with no fixed nut. Tried a nyloc with cured loctite 243 but it started to turn as soon as it bit the thread on the engine bar. The torque spec on engine bolts is 44Nm and I didn't get close. I'd prefer actual bolts as these bars will need to be taken on and off for engine access.

The problem:
I ordered a DIN931 (part threaded) M10 x 400mm hex cap bolt in A2 stainless, 1.5 metric pitch thread, with the hope of cutting a longer thread on it and trimming the excess to length. The bolt looks great - neatly cut threads, straight as an arrow, and an M10 nut spun on easily. Grabbed my M10 1.5 metric die and it would not engage. It settled fine on the starting threads, but jammed completely by the second tooth in. The rod was spinning in the vice even lengthways, so with a 17mm spanner on one end and the die on the other I tried again and this time 'peeled' what looked like a portion of thread (which I then cut my finger open on).
The die should be able to spin on as easily as the nut did at this point. It's just recut some contaminated thread on the threaded rod (paint from the engine bar) with ease. It's even the right way up. If you hold the threaded rod and bolt thread side by side, they look identical. I don't know what is wrong!
Can anyone please help? Any answers appreciated!

[Dave54]

Sounds to me as if you've got a bolt that's been threaded at the tight end of the tolerance for that size, and a die that's at the loose end.
Nuts, especially these days tend to be at the "loose" end from what I've found.
Unless you have split dies, or a die head, you can't adjust the size of the cut. Stainless is horrible stuff to thread at the best of times, you're going to need an HSS die. The type commonly seen in tap and die kits are carbon steel.

They have sent you the right threaded bolt, and you do have the right nuts for it? Check it all.

[spikelovesmetal]

Hello!

Thanks for your reply. My tap and die set is carbon steel - would it be better to try and get an M10 in HSS or, am I likely to run into the same tolerancing issues regardless of the material?

With regards to the nut, it's an A2 stainless DIN 934. It'll quite happily go on to either the threaded rod they sent me or the bolt I purchased (the one I'm trying to extend the thread on). I've also tried a nyloc and that seems happy as well. It's odd that the threaded rod and bolt compared side by side look identical, but as you say the tolerance difference might be in the 0.001s of a mm so that it's not visible but tangible.

Would it be better to try and get a different bolt?

Thanks again!

[Dave54]

I've cleaned up small threads in stainless using carbon steel dies without any damage as far as I could see, but it depends on the stainless. You'll need to lubricate the thread, and go very steadily. Screw in a quarter of a turn or so, screw back out and clear the chips. Cutting a new thread may well be beyond your die.
Split HSS dies are best, they're adjustable to some extent due to the split, but you need the correct type of stock to hold them with the screws to adjust the size.

As I said, stainless is a pain to thread at the best of times.

[Bob225]

Are the nuts tight on the thread or do they have play in them ?

Do you have a thread gauge ?

Has the die been crushed closing up the thread ?

[kellys_eye]

Sure of the thread pitch?? I've seen 1mm, 1.25mm and 1.5mm in my time.

Do you have a matching TAP that you could 'test' through the nut?

[spikelovesmetal]

Sorry for the delay - couldn't get to the garage last night to check.

Bob225 - the nut has a little play on both the threaded rod and on the new bolt, but this is about the same amount; it is perhaps a little easier on the threaded rod to spin the nut on though. I'm afraid I don't have a thread gauge so I can't measure the threads, but I've checked the spec over a few times and everything is ordered to be M10 metric 1.5 thread (I understand that we don't always get what we order though!). I can compare the threads on the rod and the bolt side by side and they line up with no issue. I checked the die itself and the ramps, channels and teeth all seem to be fine without chipping or crushing. It twirled easily onto the threaded rod just now.

kellys_eye - I'm fairly happy that the pitch is 1.5mm metric - both from the orders I've placed, comparing the threads and also being able to spin the nut quite easily onto both. HOWEVER, I did try your tap suggestion and found that my 1.5 tap from the same tap and die set will only turn into the nut as far as the shoulders, and then as soon as it starts getting to the cutting teeth (instead of the setting teeth) it jams just as well as the die did on the bolt.

I think as all three of you have mentioned above that it's likely the tap and die set I have doesn't have the tolerance precision needed by the bolt, but is close enough in tolerance to work on the threaded rod. It's a nice little set and has helped me with work in the past, but by no means is a professional set so this seems the most likely explanation. I'll see if I can get a decent M10 1.5 die and give it another whirl (hopefully it will whirl this time)!

Thank you for all your help - I really appreciate it

[Bob225]

Not had an issue with faithful or soba taps and dies, there is some horrible tat that comes out of some Chinese factories

[Hitch]

You won't get a very tidy transition between the new bit of thread you cut and the original thread.

The threads on bolts are usually rolled, rather than cut with a die. They often end up going off centre when you try and cut them by hand further up a bolt shank.