OzVMX Forum
Clubroom => Tech Talk => Topic started by: Kenneth S (222) on November 30, 2014, 08:05:34 pm
-
Hi Guys,
My recent purchase, an 89 Honda CR250RK had one of the front fender mount holes stripped out. I have had the hole filled and now want to re drill and tap it. It is a 6mm bolt. Firstly, Does anyone know what the standard thread pitch is? I have a 6 x 1mm tap which seems to match the bolt, but it doesn't easily screw into one of the other holes.
Thanks,
Kenneth
-
M6 x1 for sure mate
Pre drill 5.0
-
M6 x1 for sure mate
Pre drill 5.0
Cheers
-
For some reason the tap sizes are tight in alloy cases .... if you run a STD tap they are too loose and will strip out easy.
-
My experience is that machine tapping generally gives a tighter thread, possibly due to only 1 tap used & the tap is held steadier by the machine
-
Like a spoke threads in aluminium should be cold forged NEVER cut, that makes the thread weak. Good news is forging taps are cheap on ebay. They are a worthwhile addition to the toolbox as they can be used to repair a thread.
http://www.ebay.com.au/itm/HSS-Thredflo-Fluteless-HAND-TAP-M6-X-1-0-SUTTON-/191265412132?pt=LH_DefaultDomain_15&hash=item2c884e9424
-
For some reason the tap sizes are tight in alloy cases .... if you run a STD tap they are too loose and will strip out easy
The crankcase half and side cover threads on bikes are usually a standard M6 thread.
The threads that highly stressed fasteners, like studs, screw into are generally made with a carefully toleranced undersized tap to give a tighter fit.
There is a series of special taps to take account of this.
I use the 'Threadflow' fluteless taps that Lozza mentioned a lot at work. The tapping hole is drilled larger than for a cutting tap. The tap is wound in the normal way and displaces the aluminium (or steel or stainless steel) cold forming the thread. This gives a high strength slightly work hardened job with a good finish. There are no chips produced so this method is very safe for blind holes. These taps are quite a bit stronger than the usual type because the minor diameter is greater. The taps are more expensive but well worth the extra for fine work.
-
Like a spoke threads in aluminium should be cold forged NEVER cut, that makes the thread weak. Good news is forging taps are cheap on ebay. They are a worthwhile addition to the toolbox as they can be used to repair a thread.
http://www.ebay.com.au/itm/HSS-Thredflo-Fluteless-HAND-TAP-M6-X-1-0-SUTTON-/191265412132?pt=LH_DefaultDomain_15&hash=item2c884e9424
Excellent advice. ;D
-
When I first had a go at redoing threads I got a scrap peice of 10mm thick alloy plate and done a few practice runs first ;) best to get it right the first time on the job you are doing 8)
-
If you are going to use a flute less tap that pre drill will be different for a roll thread
-
If you are going to use a flute less tap that pre drill will be different for a roll thread
You really can't beat a rolled thread......but when in a pinch it seems the fluteless tap will do the job
-
Normaly a cut thread drill size is 5mm for a M6 thread a formed thread the drill size is 5.5mm. Think it is normally almost the root diameter for cut thread and half that for a formed thread
-
Use a bit of kero as a lubricant too. J
-
Use a bit of kero as a lubricant too. J
I use sewing machine oil to start and WD or similar to clean the schwarf away.
-
Bit like sex. Anything will do at a pinch! J
-
Thanks guys, all great info for a guys who only dabbles in his workshop for fun and has never done it for a living. Much appreciated