Bolt Selection thickness

[grain_r]

Good Morning Komatias

Thanks very much for that I will go with 5's and spread the load out to keep things square. and then thread the 3mm.

Thanks

Rob

[cropwell]

I'm thinking about using riv-nuts for the m8 bolts in my build (when I start it !).

Rob

[mekanik]

I'm thinking about using riv-nuts for the m8 bolts in my build (when I start it !).

Rob

[Blackrat]

rob, id go with m6 , m5 are a bugger to tap

they say to utilize the full strength of a high tensile bolt you need 1 1/2x its diameter into steel , or 2x into aluminum

however , you gotta work with what you got ... spreading the load is always going to be stronger, but more work

maybe a pic or two would help :D

[mekanik]

As per the Blackrat M6 is a good option reasonably course thread.
To be on the safe side do a test hole and torque a bolt, if it doesn't strip the base material it should be OK, you could keep incrementing the torque til it does strip then you know your safety factor.
Picture of what you are trying to achieve would be helpfull.
http://www.finaldrives.eu/PartsBoltTorque.htm
Regards
Mike

[grain_r]

Hey Guys

Thank you very much for the replies and I am sorry I haven't updated the thread it didn't let me know that anyone had replied for some reason.
The image below is what I am trying to bolt together.
I have used a 4.2mm Cobalt drill and then used a 5mm tap in the pillar drill and started it to keep the tap straight and then finished it off by hand although the threads aren't very good at all on two of the holes it has only got 1 thread fully around and hardly any on half of the hole which I guess must be an oval hole or something. I'm just not getting the result I should be the main issue seems to be the drill wanderd around using the pillar drill. I have used a big centre punch and then even started with a step drill of 4mm and then swapped to the 4.2 I have even turned the drill by hand and drilled the starter hole before turning the drill on and that doesn't seem great either.

I guess it's most likely the pillar drill that's not up to the job the sad truth is I think I will get a better job using my dewalt hand drill. It is a Kinzo pillar drill so a cheapo unit but I would have thought I should be able to get a hole really maybe its the monkey that's using it blaming his tools



I have my Build thread which has more images on too

http://www.mycncuk.com/threads/7936-...-few-questions

Thanks

Rob

[mekanik]

Hi Rob
Sorry to hear you are having problems.
Are your Drills ground finish and do they run true in the drill chuck?
I have had drills that were totally useless because of being bent.
Drill the holes @ one sitting ie just go for the 4.2mm.
Please don't start drilling your frame until you have perfected your marking out/drilling & tapping technique.
Also you have made a nice job of tacking your plates onto the tube, if i was going to finish weld i would only weld the top & bottom of the plates, if you weld down both sides you will get weld shrinkage that will cause them to bend.
Regards
Mike