Router insert plate - drilling/countersinking aluminium

[Mike.S]

I have a 10mm aluminium router plate in which I need to drill and countersink 3 fixing holes, to accept M6 countersunk machine screws. Whilst I'm reasonably comfortable with the marking out (using the Router's phenolic base as a guide) I'm unsure about the best way to drill/countersink the holes and would appreciate advice.

I have a drill press and from my research so far should be using around 2,000rpm for the 6 or 6.5mm holes. I propose making a 4mm pilot hole and then, probably, a 6.5mm final hole (to allow a smidgin of wiggle room for the screw), using HSS drillbits. Does this seem right and do I need to use lubrication?

My main concern is the countersinking (90 degrees angle). Can I use my normal steel rose type countersink or is there some special countersink I should be acquiring? Is it better to countersink after both holes have been drilled or after the first hole, as this may lessen any 'wobble' of the countersink. What speed should I use - I'm thinking the slower the better (think my drill press goes down to about 300rpm).

Finally, any special considerations for larger holes e.g. the 17mm hole I need to drill for the fine adjustment access ratchet (it's a Trend T11 router), or is it just pilot hole, then gradual step up in drill sizes. The 10mm thickness precludes the use of a step drill which, otherwise, would be ideal.

P.S. a local machine shop wanted £75 to do this for me which seems steep (or am I out of touch with prices :? )

 

[wizard]

its aluminium its like drilling butter, just drill without lubricant.

 

[seaco]

You will find that although aluminium is soft it can also be very grippy so it's most important to have the part held firmly clamped is best especially with the countersinking or instead of a nice circle you'll get a threepenny bit as for lubrication you could use WD40. The countersink you speak of should be fine, personally I wouldn't drill a 6mm bolt hole to 6.5mm as really you want the plate as accurate as possible, do it at 6mm and then if for any reason it doesn't work you can always increase the size...

 

[woodfarmer]

I agree with seeco, but would add the following
paraffin is the best lubricant for aluminium but any thin oil will do.
By all means drill the holes at 6mm but you may find you will need to use a round file to ease fitting the third bolt I had to when I made an 8 inch diameter circular shim for the rear sprocket on my bike. not easy drilling in 1,mm thick sheet aluminium, The 10mm plate well clamped will be easier.
mark as well as you can and centre punch. if you have the use of one, start the hole using an engineering centre drill.

I prefer to run all my tools slower than the maximum, for this you need to ease up a little on pressure, just use enough to keep it cutting.

Hope this helps

 

[seaco]

I found these a God send to accurately center holes of up to around 13mm they are well worth the outlay...

http://www.ebay.co.uk/itm/RDG-TOOLS-A-Z ... 566d6c714d

 

[Higon]

I found these a God send to accurately center holes of up to around 13mm they are well worth the outlay...

http://www.ebay.co.uk/itm/RDG-TOOLS-A-Z ... 566d6c714d

Beat me to it! Essential workshop items! don't use the every day but when you do use them they are worth every penny.

Cant remember where I bought mine, but although advertised and the box was marked as being metric, they were actually imperial. Fortunately a friend had a set of metrics and worked imperial so we swapped. But great tools one of those where you wonder how you managed before you had them.

 

[Mike.S]

Thank you all, I now feel more confident with the task.

I'll order some transfer punches and centre drills - both seem useful. Whilst researching I found 'Transfer screws' which seem ideal but unavailable on this side of the pond. Seems nearly everyone makes their own - on a lathe or mill, neither of which I have

Your advice and opinions are much appreciated.

 

[Myfordman]

Counter sinking should be done at very low speeds to reduce chatter. I tend to favour single edge countersink cutters for the best finish.

 

[Mike.S]

Myfordman/Bob

Interesting that you say that as I'd thought the opposite (other than speed) from what I'd read elsewhere!

Certainly in wood, I've found that the old fasioned single edge 'snail' countersink in a hand drill or brace works best. Conversely, the rose type, multi-flute in an electric drill chatters away producing irregular countersinks. I've never countersunk in metal before, so welcome first hand experienced comment. Is there any particular type/brand of single edge countersink you'd recommend?

On speed, I think my drill press will go down to around 250-300 rpm. Slow enough or better to hand drill?

 

[bellringer]

You want a single hole counter sink they are best they have a hole drilled at an angle though them

 

[Mike.S]

You want a single hole counter sink they are best they have a hole drilled at an angle though them

One like this?

or this:

 

[bellringer]

Yes they are the ones they work like a dream

 

[woodpig]

Spotting Drills are better than centre drills for accurate hole location.

 

[Mike.S]

Thanks woodpig. Unaware of these so looked up spotting drills and found this, which describes the situation well I think. Seem to be described by many retailers as stub drills.

For my one-off project I'll make do with the centre drills (as I've already ordered them) - their thickness should at least avoid the wobble of jobber length drills.

 

[SammyQ]

Mike, you do not need an expensive fuedanglewotsitcalled from the States. You really do not. Whack a 5cm length of M6 studding into a pillar drill chuck, exposing, say, 1cm. VERY carefully, apply a file held horizontally (like a sword) but twisted in the hand at 45 degrees to vertical, to the exposed end. Grind until the point pleases you, no great finness needed. COOL and remove. Repeat for other two/three screws. Apply one M6 nut and screw up to point. Cut behind nut to appropriate length, screw off nut at cut end to restore/clean threads. READY TO GO! Put three/four new screw markers into router base holes to same depth/projection, place router on Ali sheet, gentle lovepat on top of router with soft mallet (whatever), bingo, hole position marked!

This method has been used since time immemoriam, when Stephenson, Brunnel et al needed to mark out bolt holes on boiler chests etc. It works, it's cheap, it's fast and accurate.

Sam, who is wondering where he put his.....

PS, If I want a fancy (specific size) hole transfer punch, I lathe up a shaft of that size (if I can't find a length of scrap to fit) and then end bore it to accept a masonry nail, with the head cut off. If you leave the axial hole undersize by a whisker, than heat the shaft and shove in the nail with pliers, it holds the nail tight. Alternatively, solder or epoxy is les fraught if you are lacking in confidence. Do you really need ALL the sizes in a set? Just like you need ALL the Forstner bit sizes? Come on!!

 

[porker]

+1 on making your own transfer screws. Done this a few times. I use my lathe but a drill press will be fine. Don't use a file without a handle though and be careful.

 

[Mike.S]

SammyQ

Thanks for the advice and guidance. But:

1. I've already ordered the fuedanglewotsit (USD40, incl. P&P)
2. My therapist said that it would be unwise to withdraw too quickly from purchasing unnecessary but pretty tools

More seriously, this is the sort of thing that I should make and found another thread (can't find it again though!) on this forum where the same manufacturing method was described. Elsewhere, I found a similar method but using an allen key (sharpen to a point and cut-off a short length) inserted (+ loctite or similar) into the internal hexagonal core of a grub screw. The, say M6, grub screw screws into the hole leaving the pointed allen key above to mark the plate. This can be inserted/removed using an allen socket, with all parts within the 6mm diameter i.e. no nut overhanging the hole edge.

I've learned an awful lot from the responses to my post, both directly and from other avenues explored. Thanks to all.

 

[SammyQ]

Glad it ended well....especially the Therapy!

Lurve the allen screw idea.

Sam

 

[Eric The Viking]

Lurve the allen screw idea.

+1