Drilling and tapping holes and general metal working tips

[billysbones]

of course we're interested.

stick with it mate. Don't get downhearted and lose interest.

Buy the best gear you can afford and learn how to use it properly. books, internet. grab as much info as you can, filter it with a healthy dose of common sense and make the best job you can with what you've got.

I've just read that back and realised that whilst I've said what I meant, it sounds a bit patronising. This is not how it is intended!!

keep us posted.

[Gackt]

Lol, not patronising at all, billybones. That's what's awesome about this forum (for the most part), knowledgeable people who are happy to help out the less experienced without being high and mighty gits or flaming the bejebus out of them (if you want that, check out the pinkbike.com cycling forums, that's a bitchy place to be).

I wish I'd done an engineering apprenticeship when I was younger then I wouldn't be floundering at this stuff now. Ah well, hindsight and all that jazz.

A lot of people have said I should've just kept the bike standard and sometimes, having not been on the road for about 3 years or so, I might be inclined to agree. That said, I don't have the money to run (legally) at the moment and the little things that I didn't like about it would really bug me. Whether it takes a month or another three years to get back on the road, I'll be glad of the experience.

Will post updates and pics as it happens but be prepared to watch this space for a looooooooooong time, It'll take me a while to get some decent equipment and learn how to use it properly.

[Alex.]

If your employers are increasing in size and scope every day, then they must be the only ones in the country, seeing as the rest of us are in recession. Nice work if you can get it, and this country is dead as a engineering powerhouse. Toolmakers are going to the wall on a daily basis, seeing as most press and mould tools are now made in China.

I was chatting to a mate about this very subject last night. Both he and I work for major, national/global engineering firms that are getting more new work than we have manpower for. This is both automotive and aerospace engineering.

Virtually all of the work is non-US, that seems to be the issue, the States is in trouble so the rest of the world must be as well!

That said, both of our industries take the long term view and look beyond a 'recession' that may only last 12 months.

Alex.

[Tom Mac]

Just to add my own 2p worth, I have a Clarkes pillar drill as well (bench mounted, £35 thing from Machine mart) and its as accurate as a blind, dead herring.

[billysbones]

This....

..is a brake dics spacer I made a few months ago for my supermoto when I was playing with different discs and caliper combinations.

I turned the ring, out of HE30, on my lathe and used the tool tip to faintly sribe the PCD of the clearance holes. I took the piece from the lathe and I then dug out my Zuess book to get the calculation for the function of the PCD that gives you 6 equally spaced holes. Using a divider I scribed arcs that intersected the PCD to give me my hole centres...

..I then used a centre bit in my pillar drill to mark the hole centre, shown by the intersection of the scribed arcs, and then piloted at 2mm and drilled clearance holes at 6.5mm dia and finished them with a countersink.

But you are saying that I should have drawn a 6.5mm box around the intersections of the scribed arcs - how? - drilled the 2mm pilot - where exactly as I don't appear to know the centre of the hole by your method - and then used the 6.5mm drill bit and if the hole wasn't centred within the box (what are the odds of that? about 100%...) applied lateral pressure and produced a scrappy elongated off-round hole...

Well, I suppose that'll have to do then, if that's the best you could manage.

[abos]

Whilst i agree with a lot of what is being said the original question was about tapping square holes in alloy.

I would do the following.

1. Mark out using engineering blue using a SHARP scriber and engineering square or surface table / plate glass.

2. Pop mark the cross mark you have made with a SHARP punch auto punches are good, i have a optical punch i will post details if anyone is interested i made mine over 20 years ago.

3. Clamp the job to your drill table or even better a milling table place a dead centre in the mandrel or wobbler (10 pound on the net) in the chuck true up the centre to the pop mark.

4. Replace the centre with a centre drill of the same angle as the drill to be used not a centre drill designed for a centre used on a lathe drill to half the fnished diameter.

5. Now drill with drill approx half tapping size eg. 3.5 mm for 6.8mm tapping size for M8 tap.

6. Follow through with final size in this case 6.8 mm.

7. Now i countersink the hole lightly to just less than 8 mm.

8. now comes the intricate bit i place a hard or rotating center in the drill or mill mandrel.

9. With the taper tap in its holder i engage the centre in the centre hole in the back of the tap.

10. Apply light pressure to the drill/ mill handles and turn the tap wrench slowly.

11. when the tap is in 2 - 3 turns relaese pressure fom the drill.

12. continue to tap at a rate 1.5 forward 1 back to clear swarf.

13. Finish off with 2nd and finnally plug top.

Through out this process lubricate with parrifin or tallow.

Sounds complex but it does work you can buy or make from kit, tapping guides i would also reccomend using inserts such as helicoil if you are after greater strength our durability in alloy.

with practice you will be able to produce very accurate threads but i would advise buying a set of HSS taps and HSS drills that you save only for tapping.

buy a zeus bbok great investment and buy a set

[billysbones]

Dead simple really...

HE30 = 6082T6 aluminium. 6000 series aluminium with best all round combination of strength, machinability, weldablity, corrosion resistance etc. Most common aluminium grade used in Europe, sometimes called aerospace grade by idiots who should know better. The yanks use 6061T6 as their version...

Used my lathe to machine the blank ring from a piece of scrap aluminium round section bar and then used the cutting tool to very lightly mark the PCD (the spacing of the brake disc mounting bolts)

Scan of spacer ring showing PCD and the spacing of the holes as a function of PCD on an arc (Edit - have you spotted the delibarate mistake there? I've drawn PCR not PCD. PCR = PCD/2...d'oh!)

Front cover of Zeus book - every fitter/engineer/enthusiatsic amuteur should own one. Full of extremely useful information on everything from common machine code failures, minimum pipe bend radiui, tapping drill sizes for threads, wire and sheet thickness conversion tables. Book costs about £5 and can be bought from any decent book shop or tool factors.

Page from Zeus book (upside down) that shows how to calculate hole spacings around PCD for varying numbers of equally space holes

Left to right - Dividers, counter sink, 6.5mm drill bit, 2mm drill bit and centre drill

*deep breath*

sureley you could have save yourself a lot of work there, mille?

I mean, all you need to do was scribe yourself a nice neat box and shimmy the job about under the drill bit.............?

[eddie]

Mmmh I'm with the "mark out centres, centre punch, pilot drill (if necessary) and drill." group. Never heard of the "mark out a box round the centre" method, but you learn summat new every day!..................not that I'd bother fooking around with that, just do what I wanted at work when boss, is on holiday, gone to a meeting, or gone home!!

25 years + in Engineering, time served, employed currently as aToolmaker. People go out and buy a Landrover, Jaguar,Volvo, Nissan ,Toyota, to keep me employed. Or better buy lots of them and give them to your friends.

Thanks