stripped rc8t rcm motor mount, which tap to get?
 

title :)


m3 to m4 correct?

If it was an M3, then M4 would be a good choice if you want it all metric.

However, I'd probably find a SAE size - there's bound to be one slightly larger than M3 but smaller than M4.

any advantage to sae? other than smaller hole

Use a helicoil.

I'd try 1/8 SAE, you can use a plug tap & avoid the windings if correcting a stripped M3

Unless you have the equipment and knowledge to correctly put those in, don't bother - you'll just end up pulling it out. Helicoils usually only work ok if you can counterbore the hole, and end up with the pulling direction being such that you would be trying to pull the helicoil through the counter bore.....hope that makes sense....

Call me Mr Obvious, 3.5mm!

we use small helicoils at work, not me personally, yet; is this a standard install?
are helicoils tuff, i like the idea of keeping original size screws all around.
thanks

3.5mm is not really a common size. They can be found but probably better to go up to 4mm, more readily available.

Ditto that. If you can find a 4mm tap somewhere. I've only been able to find metrics in complete sets so far (locally). Make sure you get the correct drill size for it too.
There are two 4mm fine thread sizes 4x.5 and 4x.35, I dont believe the latter is very common. The 4x.5 requires a 3.5mm drill, your hole might already be over that size, but if you can find one, it'll be worth having around.

Dubro makes smaller size metric taps individually and in sets. I have 2, 2.5, 3, and 4mm sizes. They come with a proper size drill bit and the tap. I bought all mine on Ebay.

I buy all my screws at a local bolt and screw supply company. They have a min. purchase but the price of screws is less than 1/4th the hobby price and they are machine grade, they also sell bits and taps. They carry lots of 3.5s. The counter guy said they are used mostly in the electronics field.

As said earlier a 1/8 SAE would be a good size to step up to as it's 3.2mm. I would probably do both screws so that they are the same