Tap the Block to 5/16 UNF :)
Turbo Mini Forums

Well heres how i did it

I first set about getting a block of steel 1x1 will be enough

I found my bit in the garage so just to make sure the surfaces are true i set it up in the lathe machined the faces off both sides making sure to get it flat

You will then need to drilll a hole of 6.9mm in the block straight through doing this with a centre drill on a lathe helps to make sure its flat i then made a hole of 6.9mm wide and counter sunk the top a tiny bit just to make it easier for me to locate the drill when i come to use it.

I then made another hole the width of the tap i was using 5/16th (cant remember what size that was in mm) and countersunk the top of this as well just to help with location when being used

I then set about making a locating pin just to make it that much easier and making sure that when i used the drill to drill the original hole out of the block to make sure that it was inline

You will need to machine about 5mm of the end of this pin down to the internal diameter of the thread on the block (ive completely forgotten) then for the next inch or so make it 6.9.






Then turn your block upside down so the holes are showing and carefully mask up along the block you may need an assistant and then get a sheet of newspaper and fold it in half tape one side down to 1 and the other to the other and tape up any unecessary holes that need doing e.g distributor hole, fuel pump hole.



I then located the first hole put the block onto the bottom of the block making sure the 2 counter sunk sides faced upwards i then used the locating pin to get the block completely central to the hole, i then used a clamp to clamp the block to the bottom of the block.



I then got my drill with my 6.9 drill bit on its slowest setting and went down the 6.9 hole in the block and started to drill the top of the block, first look if you can go all the way through the block then do so this helps with tapping if you cant be careful when drilling down as soon as it feels like its doing a bigger drill than it should be doing stop this will be at the bottom of the thread that was originally their. Use a hoover to get rid of all the bits of swarf that the drill leaves and make sure u clean the block faces everytime you drill and remount it in the different positions


I then went onto tapping each hole, Using the other hole you drilled to 5/16 size, In the sequence of the 3 taps and made sure i turned back quater of a turn every half turn i did to cut the metal off. Make sure you use abit of grease on all 3 taps including the plug tap this will help get all the swarf out of the bottom of the hole.




Once finished make sure you pull the masking tape off as it does become quite sticky even after an hour and make sure life all the tape and news paper to 1 side this will avoid getting shrappnel in the block

I'm extremely happy that you made a "how to do article" on this quite complicated job. Cheers

could have at least used page 3...

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Hey, that's some nice work there but I think you've gone to a lot of trouble. I just drill them in the Drill Press, take your time cause you can still stuff it up and the tap them also in the drill press but not under power, just turn the chuck by hand. No need to tap it all the way like this, just make a good start, about 4 - 5 threads. Do them all like this and then finish them off by hand with a normal tap wrench.

Don't try it without a drill press or as munnracing has shown, a jig.

if you are SKILLED you can do it by hand

Dose that mean you did mine by hand? :)