Drilling 4mm stainless steel

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david36

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I want to be able to fit a drop nose pin over my anchor when it is sitting in the stemhead. At present there is no hole allowing me to do so. Because I can only access the stemhead from one side, the rollerfurler gets in the way on the other side, I think that I need to drill through the outside plate then continue across the gap and drill the other side without removing the drill. The gap is some 10cm and the sainless steel plates are 4mm. Does such a drill bit exist and what do I have to go and buy or is there a better way of doing this?
 
I suppose the diameter of the hole will have an effect - drill bits get longer as diameter increases. Drilling 4mm stainless should be easy. I used titanium tipped drills, cheap, but did the job very well. Just remember to make a starting mark with a blunt drill and a hammer, otherwise the metal drill will move when starting to drill. You could always, as I have, put the drill bit in the chuck by the bare minimum - sometimes works.

What on the furler is getting in the way on the other side?
 
Drills are available (Long Series) but the problem is to make sure the holes line up and provide a close fit across the top of your anchor.

Have you considered making a couple of "U" shaped guides with the distance between the legs of the "U" the same as the stemhead plates with a hole to suit your drop nose pin drilled straight through the legs near the open end (Drilled in a pillar drill to ensure the holes are perpendicular to the legs), then cut a piece of rod same ø as your pin so as it just fits between the stemhead plates, fit a guide to each end then drop the rod in between the stemhead plates and position where you want the drop nose pin to be and you will then have the exact location on the outside of each stemhead plate to drill the holes needed. one leg of each guide needs to be outside the plates.

I have a similiar arrangement on my boat but the drop nose pin is 8mm ø and even that has been bent on occasion - I will be fitting a 10mm ø pin for this season.
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hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
 
For drilling SS start with a new drill bit. (I hope you find a long one) You need a lot of pressure. So you will need to drill a bit then stop to give your arm a rest. Use lubricant (oil is OK) on the drill as the smoke is an early sign that the drill /job is overheating. Overheating blunts the bit and work hardens the SS so avoid it. You should get lots of metal being cut out all the time. If not press harder and/ or have a new drill bit. good luck olewill
 
The key to drilling stainless (or even mild) steel successfully is to keep the speed of the drill slow. Big diameters are best done by drilling a small diameter pilot hole first but you might struggle to find a long drill with a small diameter.

But anyway, apart from getting hold of a long enough drill bit, this really should just be a few minutes job (at most).

Chris
 
Slow ... real slow and steady .....

HSS drill bit ... possibly buy a couple as they will blunt and as they blunt SS will refuse to yield.

Suggest Mamsahib dribbles water or other bio-degradable liquid over drill tip and work to keep cool.

I like the idea of the pin ... but there is always the temptation to use it while anchoring to keep chain in the stemhead fitting - stop it jumping out .... I advise against that ... I prefer a light cord - which then can be cut easily of chain jams or needs to be set free. A pin can jam by chain pulling up on it etc. (Just a thought ....)
 
Cobalt drill bit needed

Normal HSS drill bits will blunt very quickly. I got a set of cobalt bits from Machine mart. For an extra long bit you'd probably need a specialist tool supplier. As others have said, key is to drill slowly and keep the cutting site cool. For a similar job to yours, I tied the marina hose pipe in position to keep a constant flow over my drill bit tip as I was drilling.

Cheers,

Jerry
 
Cobalt drill bit is definitely the way to go for drilling SS and you won't need a lot of pressure but lubrication always helps /forums/images/graemlins/smile.gif
Full set of cobalts from 1.0 - 10mm is £23.44 from Machine Mart.
If roller furler is in the way just move it...... attach masthead halyard to foredeck...... slacken backstay......... remove roller furler from stemhead fitting.

hope this helps,
Paul.
 
FWIW, I drilled three holes in a 4mm stainless plate at the weekend..... with a brand new HSS bit, going very slowly, and LOTS of pressure, it went through it suprisingly easily...... took me no more than 5 or 6 mins to drill 3 holes of about 8mm diameter....
 
If you don't use a centre punch then you would need to use a drill jig or bush to accurately guide the drill point, and devise some means of clamping this to the workpiece. Personally I'd go for a sharp centre punch and a sharp drill used at slow speed and keep a steady pressure on so that the drill keeps cutting. If it starts to skate over the surface instead of cutting, it will work-harden the stainless steel.

Also it pays to buy good drills and they are not cheap. Engineering firms wouldn't pay high prices for tools if they could get the same results with cheap trash from discount stores
 
Emphasising the sharpness is crucial. This is the most important point to remember when machining S/S, as soon as a drill bit loses it's edge it will start to work-harden the steel very quickly. If your drill isn't cutting, it is hardening the workpiece. The second point is cooling - plenty of it!
In the workshop I use paraffin, this is not practical for the job in hand here so plenty of water....
 
Best lube in the world for drilling stainless steel is condensed milk.
Colin
 
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