Stuart 10V Hiccup!

Hi All,

Spent a happy few hours in the workshop today getting back to my 10V build, (my first ever!).

Drilled the steam passages in the cylinder and started making the top and bottom covers. All went OK until I broke a centre drill tip in the bottom cover when getting ready to drill through 5/32". Fortunately I used a very small centre drill but still enought to throw the drill off centre when i tried (lightly, to get it out)

My question is: Is it OK to drill and ream through from the other side, say 1/4" and loctite in a piece of 1/4" bronze rod that i have? wait until set and then gently start again keeping it cool as possible to not break the loctite..

Don'y really want to start again as I have no more cast iron bar.

Cheers, Martin and a Merry Xmas to all here !

Was fairly common on full size to have a "neck bush" which would be almost the same as what you are doing, so yes it will be OK.

Worth getting yourself a spotting drill or two as these are better for starting holes and as they don't have the small pilot are not easily broken. I find 1/8" and 3/16" cover most things or 3mm and 5mm if metrically inclined. Keep the ctr drills for when you actually need to run a ctr in the hole.

Even when you need a centre drilled hole to run a centre on it is good practice to shorten the small diameter to prevent breakages. This was shown to me over 50 years ago when I started my tool making apprenticeship and I do it to this day. Jason's tip about using spotting drills is good and they last years.

Could you not drill from the other side & tap out the broken tip then continue? otherwise drill from the back side, drill & tap for 4mm, screw in & Loctite a 4mm hex bolt & cut off flush, then re-pop redrill for 5/32.
I had to do similar on mine when I didn't mark off the tapped holes in the cylinder top face for the top cover correctly & didn't realise until I notice the hole was out of alignment when I put the cover on, worked fine, no need to use bronze rod.

​George.

Thanks guys, will get a couple of spotting drills. Will do what mechman says I think as the threaded 'bush' will be stronger. I have a few small bronze screws that will do and hopefully look nice as well.

Its funny that I get literally dozens and dozens of centre drills and hardly ever a spotting drill in the lots I buy? Clearly not that common?

Martin

Martin , I have some 1/4" square section cast iron for use in welding Ci with oxy-act. You are welcome to a sample piece if it helps . If you PM me your details I will drop you some in the post .

Trevor .

I have tried in the Past to get spotting drills under 1/4 or 6mm but have had no joy, where is a good place to source them?

Michael

The Interstate ones from MSC are reasonably priced from £2.32+VAt for an 1/8" one. Page 17 of the virtual catalogue or pay a bit more for Hertel or Guhring but I find teh interstate fine for hobby use.

Bought a spotting drill from:

http://totoolsupplies.co.uk/

recently but V. expensive (about £20 inc postage etc for a 3mm one)

Be nice if any of our usual suppliers stocked them at a more reasonable price!

Greenwood tools do them at reasonable prices but I have not tried that make though they have a good name

I think the Guhring ones are over tenner when you add on the VAT!

Neil

And that is when they are 50% off in the weekly comic

You may be able to drill out the broken off tip of the centre drill by modifying what is left of the broken centre drill body. Take a Dremel or similar grinding tool with a small, thin cutting disc installed. On the end of the centredrill with broken off tit, cut a slot up the centre of it, about the same width but slightly larger than the diamter of the broken off piece and about the same depth plus a tad more.

If you now drill into the original centre drill hole where the broken off tip is embedded with this tool, it will drill down around the outside of the broken off piece to a depth where the broken off piece of HSS will be left standing proud and can easily be removed with a pliers, scriber etc.

In future, instead of buying hard to find spot drills, you can use a larger centre drill but do not drill all the way down with it in the conventional manner. Just use the tip piece to make a small indent, enough to get your small diamter drill bit started. If you use a large enough centre drill the tip piece diameter will be larger than your small drill bit and so provide a good start, with suitable care taken.