brake disc retaining screws

Post by **NafemanNathan** » Fri Apr 11, 2014 1:22 pm

Bludge wrote:well after spending half an hour drilling, i have managed to get the head off one bolt.

Sounds like you need a new drill bit and/or drill

Bludge · Post by **Bludge** » Fri Apr 11, 2014 1:33 pm

NafemanNathan wrote:
Bludge wrote:well after spending half an hour drilling, i have managed to get the head off one bolt.
Sounds like you need a new drill bit and/or drill

Both, but can afford neither! infact, i went to screwfix to get the drillbits last night, and they assured me they would be good for drilling metal. i was not impressed and cant imagine that its entirely down to the drill being rubbish.

My thinking was if the wheels are on nice and tight the discs arent gonna move anyway? if i can get them out i will stick in some of those hex key screws instead, grease them and just pinch them up. really dont want to have to do all this again just to get the discs off!!

bb1boy · Post by **bb1boy** » Fri Apr 11, 2014 1:40 pm

I used an impact driver to get mine out, a few hefty whacks with the hammer and out they spun!!

bb1boy · Post by **bb1boy** » Fri Apr 11, 2014 1:41 pm

one of these ^^

mills · Post by **mills** » Fri Apr 11, 2014 3:12 pm

Impact driver with a ph3 screwdriver tip, a bit of wd40 and they would've come out easy enough. But yeah, drilling them out shouldn't have taken half an hour

Sounds like the drill bits were bum droppings or the drill was down on power.

Post by **indigolemon** » Fri Apr 11, 2014 3:19 pm

Drilling metal: 1 - go slow, speed kills the sharpness and 2 - add oil to the tip of the drill bit, engine all is good, keep it lubed.

Bludge · Post by **Bludge** » Fri Apr 11, 2014 4:01 pm

cheers guys. one other question, i need sone of the washers that sit either side of the banjo bolt thing where the brake line connects to the caliper.
are they anything special or can i just match the size with a metal washer down b and q? as i really dont fancy paying the 3.28 each honda quoted!

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Fri Apr 11, 2014 4:15 pm

indigolemon wrote:Drilling metal: 1 - go slow

Not necessarily...

Cutting speed is dependant on the specific metal and the diameter you're drilling. The smaller diameter you're drilling, the faster you actually want to go.

The calc is
S = (1000 x V) / (3.14... x D)
where;
S = Spindle Speed (rpm)
V = specific cutting speed for the material being 'cut' (look up in a data table, think mild steel from memory is 30?)
3.14 = pi (I don't know where that is on a keyboard?

)
D = Diameter being cut (or drilled).

(

Why I remember that so specifically from 20 years ago at college, I'm not entirely sure...

and I haven't been on google to verify if my memory is correct, so @Donald feel free to do your worst... )

EDIT:

thinking a bit more I now recall that (1000 x V) is specific cutting speed for the material being 'cut' and what tool material you're using to cut it (if you use a harder tool material you can run at higher speeds).
1000 x 30 was for cutting mild steel with standard tungsten carbide tool, IIRC

EDIT EDIT: I apologise for boring the jobby out of everyone with this post. I've actually been doing some proper engineering stuff the last couple of days and it seems I can't shake the hard on atm and it's just carrying through everywhere...

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Fri Apr 11, 2014 4:18 pm

Bludge wrote:cheers guys. one other question, i need sone of the washers that sit either side of the banjo bolt thing where the brake line connects to the caliper.
are they anything special or can i just match the size with a metal washer down b and q? as i really dont fancy paying the 3.28 each honda quoted!

You can match them up from anywhere that sells 'em, don't need to be Honda oem.
Just make sure they're copper (or brass) because they need to be soft non-corrosive metal. Steel will just body lemonade out brake fluid everywhere!

Post by **Donald** » Fri Apr 11, 2014 6:21 pm

wurlycorner wrote:( Why I remember that so specifically from 20 years ago at college, I'm not entirely sure... and I haven't been on google to verify if my memory is correct, so @Donald feel free to do your worst... )

Why would you assume the worst? Obviously it's correct... what kind of engineer wouldn't know this off by heart. All I would say is that working to pi 2dp is probably overkill for something like this situation, just use 3. It makes the maths easier too. Obviously for other jobs, decimal places are more appropriate.

If you really want my opinion...

from a 'make it easier to estimate' point of view I would arrange the equation like this:

Where: scs = specific cutting speed, dia = diameter.

Much easier and quicker to estimate 1000 * fraction than [w*x]/[y*z], but that's just IMO of course. We all know everyone calculates differently

As an aside, wurly do you use MathType (used to make image above) with work at all?