cjs3
Member
Posts: 7
|
Post by cjs3 on Jul 2, 2008 16:24:46 GMT
It's another drilling topic! I have been recently machining an aluminium block as the base of the vertical cylinder of the Beam engine I am building. I initially regarded 'ally' as being an easy alternative to working with mild steel. I now realise that I was wrong to think this way. I have discovered that there appear to be two specific difficulties to overcome. The tendency of smaller diameter drills to wander off course so that they do not exit from a rectangular block in line with their entry point; and the tendency for the drill to snap within the block. I regard my first attempt as a practice piece as my attempts to remove the embedded stub of a broken drill without spoiling the work were unsuccessful. To produce a 2.2mm finished hole I started with a centre drill; With paraffin lubricant I then used a new 1.5mm drill and at 2500 rev (being the fastest speed on the drill) attempted to drill deeper, clearing the hole of swarf regularly. I think I was too tentative and rather than encouraging the drill to cut I allowed the cutting edge to jam with granular swarf. I suspect that a similar mechanism may encourage the drill to wander off course. Returning to my aluminium block, I continued to drill further holes in the block (hoping to recover from the problem of the broken drill) - I was more successful and had no further breakages. However failing to remove the broken stub I shall have to start again.
Beyond the use of lubricant, high drill speed, medium feed, regular clearance of hole are there any other things I should consider. Aiming for a finished size of 2.2mm would a drill larger than 1.5mm be sensible to use for the first cut in order to reduce the chance of breakage?
|
|
lancelot
Part of the e-furniture
Posts: 471
|
Post by lancelot on Jul 2, 2008 18:21:19 GMT
Hi CJ...if not drilling deep holes, try using ''STUB'' drills...these are a much shorter than normal drill with less of a habit of flexing in the material.
All the best for now,
John.
|
|
|
|
Post by circlip on Jul 2, 2008 18:47:27 GMT
Peck rather than long stroke and use WD40 or equivalent to lube(when we used milk, WD wasn't invented) Oh yes, make sure the lump is supported and gripped firmly.
Regards Ian.
|
|
paul
Member
Posts: 8
|
Post by paul on Jul 2, 2008 20:05:25 GMT
How much of your 1.5mm drill extended from the quill?
Could the work have been accidentally offset slightly after centre drilling causing the bit to wander?
How deep did you go with the centre drill?
How was the block supported/secured?
These are things that might also affect your results. If your 2.2mm is a clearance hole for securing the base I'd go straight to that size from the centre drill. If that's a tapping size I'd probably do what you're doing ;D
Please note: I'm a learner too and I've got next to no experience of aluminium so take with a pinch of salt!
PS Nice to see someone else is posting in Stationary Engines! Which beam engine are you building?
|
|
|
|
Post by circlip on Jul 3, 2008 7:23:27 GMT
QUOTE, "Aluminininium - GIRLY metal " ? ? ? ;D
|
|
paul
Member
Posts: 8
|
Post by paul on Jul 3, 2008 7:33:10 GMT
QUOTE, "Aluminininium - GIRLY metal " ? ? ? ;D That's the stuff ;D I spent about an hour last night turning a 2" flywheel to size from a rectangular lump of 1/2" thick steel - man's work! (I've got the swarf burns and a pile of grinder dust to prove it!) |
|
|
|
Post by circlip on Jul 3, 2008 12:04:34 GMT
NOOOOOOOOOOOOO, you shouldn't use Bauxite derivatives for them, the clue is in the name, "Flywheel" despite Elmer.
|
|
|
|
Post by Paul Boscott on Jul 4, 2008 6:25:26 GMT
You have done all the things that I would have done. I would now be questioning the metal there are many types of aluminium with the alloys designed for as many specific purposes. I have encountered some that when machined give a smooth finish and some that with the same settings produced a finish you could use as a wood file. The alloy that I have had my best results with is referred to as HE30.
Paul
|
|
paul
Member
Posts: 8
|
Post by paul on Jul 4, 2008 8:11:22 GMT
circlip - the wheel is *steel* not ali! ;D
|
|
cjs3
Member
Posts: 7
|
Post by cjs3 on Jul 4, 2008 13:45:01 GMT
Paul & co
It is the Stothert and Pitt beam engine kit from the Cotswold Heritage collection (Modelsteamenginesuk.com). I must confess it was a bit of an impulse buy at the end of a bad day at work a few months ago!
Holes pass right through block - about 15mm. The centre drill only 'developed' the centre punch mark - it didn't go in far enough to widen the hole. Work securely held in the milling vice.
Having read the comments and having drilled six holes successfully in what is now the scrapped first attempt I'm hopeful that with the experience gained I shall be successful on the next attempt.
I think the ally supplied in the kit was HE30 - I'll check when next at home.
Ashley
|
|
paul
Member
Posts: 8
|
Post by paul on Jul 4, 2008 16:45:19 GMT
That's a nice looking engine Ashley, I'll look forward to seeing it! Keep us posted on the build with pictures etc  |
|
|
|
Post by circlip on Jul 4, 2008 17:03:38 GMT
HE30 should have drilled cleanly Ashley, was the drill sharpened correctly? ?
Regards Ian.
Yes Paul, I gathered that, a bit strange cos Elmer seems to use alloy for just about everything.
|
|
paul
Member
Posts: 8
|
Post by paul on Jul 4, 2008 20:17:21 GMT
Yes Paul, I gathered that, a bit strange cos Elmer seems to use alloy for just about everything. He specifies 'any metal' for this particular engine - my guess is it'll need more weight than most of his designs. |
|
