One for the engineers...
I need a tap to clear up the threads in my SMax roof rack fixing points due to accumulation of surface rust / dust and grot.
They're a blind hole about 15mm-20mm deep, 6mm metric thread and I need virtually all of the depth.
Is there a special / best type of tap for this?
The top 5mm of thread is sound.
Blind tap of appropriate size.
That said I'd probably use a thread cleaner tap
Could make your own with an appropriate bolt and a grinder. Cut 4 slots vertically up and down at 90 degrees.
M6 plug tap. If you're just cleaning the threads up, you won't need a taper or 2nd tap.
Plug tap or machine tap would be fine. If desperate cut a slot lengthways across the thread with a hacksaw in a longer M6 bolt and wind it in (only for rust\ dirt, not reforming damaged threads)
Plug tap and grind it flat for that extra 0.5 mm 😉
Plug tap as suggested. Sometimes called a bottoming tap. If you can't get one; grinding down a taper or intermediate tap makes a great alternative.
Are these like the Mondeo I used to have? Holes in the roof under little covers? Struck me as a awful design, collecting water and c*** until the roof rusted or there threads got damaged.... So after a thread retapping exercise of my own very early in the cars life (the threads seemed awful from factory) I bought some stainless 6mm grub screws and they lived in the holes, covered with generous amounts of copper slip, whenever the roof rack wasn't fitted.
Thanks all. Got an M6 tap set ordered off eBay that includes a bottom tap.
May have ordered a bearing puller for the FS bike as well 😂
@neilnevill you have smacked the proverbial nail right on the head. I'm going to pick up some M6 marine stainless machine screws and some rubber washers to do exactly that and don't get me started on how useless those plastic drain strip covers are ...
If the threads are rusted, how confident are you that the fixing will be mechanically sound once it's re-tapped?
Try a bottle brush down it first so the tap doesn't get unnecessarily blocked with loose crud.
Glad to be of help.
Awful piece of design from Ford imo, but easily fixed with the stainless grub screws. If it's like the Mondeo they need to be grub screws, a head of any kind fouls on the metal strip/gutter thingy that the plastic covers clip into.
You probably are already aware, but be very careful when nearing the bottom of the thread-it’s really easy to break a plug tap in the thread if you try turning beyond the hole depth. Any significant resistance to turning then stop. And using the half turn forward quarter turn back technique to help clear the swarf/corrosion may well help
