Problem with M2 thread

I've tapped a hole M2 and inserted a threaded rod, no problem

I've tapped a second hole M2, an M2 nut will go on the threaded rod but the threaded rod will not go into the threaded hole,it won't even start.

Any ideas ?

Did you use the same tap?

Yes, same tap same length of threaded rod

try running the tap down again?

Michael W

I've recently had a similar problem with some M6 brass studding. I cut 2 studs from it and made some knurled thumbnuts tapped M6. These go sweetly on to an M6 bolt; M6 hex nuts go on studding freely; brass nuts bind on to studding as if the thread is wrong. Turned out that one end of the studding (1 metre length) was slightly oversize - the thumbnuts went fine on to the other end.

So, try the other end of your threaded rod in the hole.

One or more of the three items is the wrong size.

Either your tap, the nut or the threaded rod.

You need to find out which and then buy the correct sized item(s). All will be fitting properly, then.

I suspect you are buying uncertificated items as far as dimensions are concerned - probably cheap stuff made in China.

Really?

How many certificated taps have you got?

Neil

Run an M2 die down the threaded rod. Off-the-shelf nuts are often a very loose fit, so not a good guide.

Does threaded rod no 2 fit in the hole where threaded rod no 1 fits? If so then threaded rod no 2 is probably oversize.

I can't try no2 in no 1 hole as no 1 is thread locked in.

I'll try an M 2 die and see what happens.

How many certificated taps have you got?

Hopefully none from China. But I do buy my threaded items (and materials) from a reputable source, where they do have a record of the supply chain, for anything where it is important quality-wise. I pay more but am confident the parts are what was ordered, not a close-ish approximation.

Obviously easier to check the nuts and bolts (or threaded rod) for size, if there is a problem - and if the rod checks out under size at one point and different at another, it is not too dificult to conclude that the rod is not the best quality.

Somehow I doubt if it was the same rod (that threaded in OK) which would not thread into the second hole. If it was, the tapping must have been at fault? Perhaps the tap was worn out after that first use?

I suggest taking a magnifying glass to the threads in the hole and the rod. If the start on either is damaged expect trouble. Even if the hole was tapped OK, it's quite easy to damage small threads on assembly by cross-threading.

You didn't say if you are cutting lengths off the threaded rod and fitting them into the M2 hole. If you are, it's very likely that the thread on the rod will need tidying up with a file before it will fit.

I did a fair few M2 holes and studs on the first model engine I built. After various setbacks, the following worked well for me:

• Tap the holes with a tap-stand or other means of keeping the tap straight
• Take care to remove swarf from the hole
• Run a known good thread on a commercial bolt in and out of the newly threaded hole
• Put a known good nut on the threaded rod before cutting it. After cutting, file the end of the rod flat and remove the nut over the newly cut end. This de-burrs it.
• Screw the studs in by holding them in a pin-vice. A pin vice makes it much easier to keep the stud straight and also to feel when the threads engage.
• A little oil helps.

Dave

I bought some M3 stainless studding off ebay. It was total rubbish, you could push a nut along it without turning it, and looking at it through a loupe it was obvious the thread was hardly there. Got my money back, and made the studs by cutting the heads off long screws.

I used M2 brass to hold my side tanks together for soft soldering. An ancient battery drill made short work of tapping the holes. I got it for nowt as the battery was kaput, so now has a flying lead to a lead acid battery, and can be rigged up with an external reversing switch so you're not using the switch on the drill with the tap screwed in

Anyone got a good supplier for small studding? My local engineer's merchant starts at M6

Edited By duncan webster on 20/05/2017 21:15:30

Edited By duncan webster on 20/05/2017 21:16:32

Before cutting threaded rod, put a nut on it so that after cutting the nut may be unscrewed straightening any bent threads.

Ian S C