Drilling stainless pullpit

[MagicalArmchair]

Over the winter, I want to fit a Selden bowsprit to fly the cruising chute from on our Bavaria 40, like one of these.

To do this I’ll need to fit a mounting ring to the pullpit like the below:

Right now the pullpit looks like the below.

Will I struggle drilling that pullpit? I figure start with a centre punch, then slow speed with cutting fluid and plenty of pressure with an SDS drill and avoid work hardening it. Or will it simply be too hard to drill it in this way?

 

[GregOddity]

Over the winter, I want to fit a Selden bowsprit to fly the cruising chute from on our Bavaria 40, like one of these.

To do this I’ll need to fit a mounting ring to the pullpit like the below:

Right now the pullpit looks like the below.

Will I struggle drilling that pullpit? I figure start with a centre punch, then slow speed with cutting fluid and plenty of pressure with an SDS drill and avoid work hardening it. Or will it simply be too hard to drill it in this way?

Honest answer is that you will struggle either way. Taking it off is a pain so you’re basically better with drilling it in place. You need to spend money on the drill bits. SDS is not what I would recommend for stainless. You’re looking for Cobalt drill bits. The more cobalt the better but it’s all a matter of the size of the wallet. You’re looking at, at least two so if (or when) you kill or break one you got the other. You have to pay attention to temperature as under you got gelcoat and fibreglass. Slow and steady will get it done.

 

[Bodach na mara]

Don't use the SDS hammer action. You will only harden the stainless steel.

 

[Tradewinds]

I heard using a centre punch can harden S/S - is this true?

 

[pandos]

I heard using a centre punch can harden S/S - is this true?

No ..

I have drilled a lot of s/s lately using a box of bits from Amazon and stepped bits from Aldi..

.I was very sceptical (in fact I paid nearly as much for a cobalt bit in a local supplier as I paid for the box of bits...

Good consistent pressure, something to cool the bit and (wd40 or just plain water) worked Everytime....I used my Makita battery drill...

VonHaus 99pc Cobalt Drill Bit Set – Drill Tough Materials Inc. Titanium Alloy, Stainless Steel, Brick, Plastic & Wood – Storage Case Included https://www.amazon.co.uk/dp/B07HY3NFQT/ref=cm_sw_r_cp_apan_glt_fabc_DFKSV7TMF6C3V0WTGQME

 

[Rum Run]

I heard using a centre punch can harden S/S - is this true?

It can. Mark the point of entry with a pen or pencil onto masking tape over the position, then start with a new 3mm drill, quite fast and enough weight to actually cut. Just go in about 3 to 4 mm. Open that up to 5mm same depth, then go in with the actual drill . If the final hole size is over 10mm I'd go through with say 6mm first.
This is definitely a job for a good battery drill with 2 speeds.

 

[vic008]

I seldom centerpunch, use masking tape, perhaps 2 layers. Never skates.

 

[coopec]

I've drilled lots of holes in ss in situ.

I'd agree with Pandos "Good consistent pressure, something to cool the bit and (wd40 or just plain water) worked "

When I first started drilling SS I couldn't put enough pressure on the drill and I work hardened the SS. That made it virtually impossible to drill through.

Then my B-I-L (a diesel fitter by trade) came to my aid and he sharpened up a masonry drill, we put a timber across the back of the drill and while I levered the drill down he operated the drill. The holes drilled quite quickly. (He said that is how they drilled out broken engine studs out of diesel motors. Of course they used drill presses)

You have plenty of anchoring points on the bow for a timber lever so I'd get a mate to put pressure on the back of a drill with a timber lever (not enough to break the drill!) while you operate the drill. And HSS drill bits are OK for SS.

There's stacks of video clips on YouTube on how to use masonry bits on hardened steel.

 

[Daverw]

Whatever type of drill bit used it’s all about constant back pressure and slow speed, you have to keep the drill bit cutting. Using a pillar drill makes this easy but not easy to do on the deck.

 

[penfold]

I wouldn't bother with cobalt, expensive and more brittle than cooking HSS which is a recipe for breakage when using a hand drill rather than a drill press; HSS is quite adequate for stainless steel provided it's sharp, of good quality(Presto or Dormer for preference) and lubricated.

 

[doug748]

I agree HSS are fine and inexpensive. Use new drills. People who do a serious amount of work use this stuff (or things like it):

https://www.mytoolshed.co.uk/rocol-53023-rtd-cutting-compound-500g-tin

It's good.

.

 

[PCUK]

I can't understand the fuss about drilling stainless. We drill it every day wet or dry and never have problems. Just make sure the drill is sharp and coarse and any old bit will do the job.

 

[rotrax]

I have the advantage of being able to sharpen drills by eye on a bench grinder, a black art which has saved me a lot of money over the years.

Coopec has it bang on, sharp drill bits, lots of pressure, slowish speed, plenty of lube.

I once cleared the work hardened skin with a small round abrasive grinding ball in a drill. Once the hardened skin was gone it drilled as normal.

I am just off to the workshop to fabricate 60 X 60 X10mm S/S backing plates for eye bolts to tale sheet blocks for my new reacher. I shall use HSS bits, my old drill press and plenty of lube.

 

[John the kiwi]

I just drilled a dozen stainless steel roller pins /axles for boat trailer rollers. The holes are 3.5 mm to take 3 mm split pins.
The shafts are 20 mm diameter T304 stainless.
Drill bit was plain HSS in a drill press. I did all 12 without re-sharpening, - slow ish speed and steady constant pressure feed. I have done the same job with a battery drill. Choose low speed and keep pressure on.
Natively, SS 304 and 316 are softer than carbon steel. Its the work hardening that messes with amateurs.
I do use a center punch to put a light dot and am aware that it will cause local work hardening, but never had a prob drilling through with a sharp bit, low speed, high pressure.


Top tip for old farts: Get some 3x magnification reading glasses from supermarket or wherever and use these to see what you are doing when sharpening drill bits.

 

[Moodysailor]

As per most of the recommendations above - good, sharp drill bits (HSS, or Cobalt). Start small and work up in size. You will kill a few drill bits doing this, but replacements are cheap, so I personally would go with new HSS index and put it down as part of the cost.

A good quality cutting compound (Rocol, etc) is a wonderful thing, drilling SS dry is fraught with challenges and IMO, requires some experience (red: mistakes) to learn the technique. We had cutting compound next to every drill press when I was an apprentice...

 

[Spirit (of Glenans)]

The first time I tried to drill a stainless fitting on a boat I managed to drill a pilot hole and then enlarge enlarge it to an intermediate size, then had a delay while I mounted the final drill bit in the chuck, unfortunately, when I looked at the final result I discovered that, because of work-hardening, instead of a hole of the required diameter, I had produced a drill-bit that was reduced to the diameter of the intermediate hole
My grandaughter's partner, who is a s/s fabricator has since shown me how to drill the material quite easily with a HSS drill and WD40.

 

[rotrax]

I use a 50/50 mix of TQF and Comma degreaser in a Wesco type pump oilcan.

Smells good when it warms up too................................

Works well, I have always got plenty in stock and cleans up after with a wipe.

 

[MagicalArmchair]

I do have a very good quality stepped drill bit I could use (I think it is HSS). I have only used it before in my pillar drill, however, I could give that a go. I do quite like the look of this guy:

https://www.amazon.co.uk/STROTON-Me...W2,B08RZDLCQY,B01I0RP5OU&srpt=DRILL_BITS&th=1

Nope, I would not use the hammer action on anything but masonry - I was more using the SDS as it has a big flipping handle so I can bear down pressure on it to get the bit cutting.

Thanks for the advice, I'll be sure to use some cutting fluid as I go in there... once I am brave enough!

 

[Spirit (of Glenans)]

Whatever type of drill bit used it’s all about constant back pressure and slow speed, you have to keep the drill bit cutting. Using a pillar drill makes this easy but not easy to do on the deck.

It might just be posible to use a drill stand in that location, (tied on to prevent going overboard). I have found that using one makes a big difference when trying to drill successfuly with a hand drill.

 

[rotrax]

I have just drilled six 10mm holes in some pieces of 6mm 316 under my pillar drill.

Twice the drills stopped cutting. I immediatly re-sharpened them. They started cutting again instantly. Cheapo HSS bits, but with a proper angle at the tip.

I started with a 5mm, then 8mm and finaly the 10mm. Lots of lube, high pressure and slow speed. Centre punch first.

My 50/50 TQF and degreaser worked a treat.