Here is a list of all the postings David Littlewood has made in our forums. Click on a thread name to jump to the thread.
I have found http://www.homeworkshop.org.uk/ a great site for selling (and buying) anything of interest to MEs. It's free, and most stuff seems to sell very quickly. You don't get the advantage of the auction bonus which occasionally happens if two bidders get carried away though.
|Thread: Old lathe, chuck accuracy|
One factor that seems to have been overlooked here is drill runout. Even with a bar held perfectly concentrically (and repeatably) - for example in a collet - there is every chance that the drill bit will deviate if the hole is of any significant length. The amount of this will depend on lots of factors: the accuracy of the lathe bearings, the accuracy of the drill chuck, the accuracy of the starting hole, the adequacy of clearance of swarf from the drill flutes, and (probably most of all) the accuracy with which the drill bit has been sharpened.
As to the latter, if it has been re-sharpened (especially by a novice) or is of less than top-tier quality, there is a chance that the lips will have unequal length. This virtually guaranees that the hole will deviate, and the deeper it is the more it will deviate. Even with top-grade equipment in the hands of an expert, to get a hole to stay concentric at a depth 10x drill diameter takes a lot of care.
The late, and renowned, George Thomas, in his book The Model Engineer's Workshop Manual, sets out a very good discussion of deep hole drilling, and the steps you need to take to do it well. I heartily recommend this book; even if you never make any of the tools he describes, there is a wealth of useful information in it.
Edited By David Littlewood on 09/10/2011 19:36:23
|Thread: Sir William|
Like I said, look in the October monthly sales flyer for the best deals. 2 and 3 mm long-series slot drills (not screwed shank in this case) at £2.35 each:
...and anyone who can't find some other things to make the postage worthwhile has a *lot* more willpower than I do!
|Thread: Collet Chuck set.|
My Emco FB2 mill has an external thread on the upper end of the spindle. The drawbar is a very long hex socket capscrew; to remove, there is a threaded cap (with a hole in the end big enough for an Allen key) which screws on the external thread, then with a big Allen key in the drawbar and a spanner on the flats on the cap, you can force the drawbar up against the cap, which pushes out the 2MT tooling.
One problem is that half the tooling you buy has an M10 thread, the other is 3/8" BSW. I got overt this by making a 3/8" BSW drawbar, with a hole in the upper end, into which I Loctited a turned-down M10 capscrew. Rather to my amazement and gratification, this has survived about 20 years of use.
Edited By David Littlewood on 04/10/2011 18:03:59
|Thread: Sir William|
The J&L price for 2mm long series slot drills (with screw shank) is £10.55 + VAT and postage. Page 233 of the catalogue.
As Graeme said, drill chucks are quite unsuitable for holding milling cutters. however, ER series collets are quite suitable - I frequently use them for this. You should find this gives you a little extra reach with a standard length slot drill.
However, if that does not give you enough reach, you can get long series slot drills from J&L/MSC:
Their prices are not the cheapest, but their speed of delivery is amazing. Also, look in their monthly sales flyer, you can often get what you need at a significant discount.
|Thread: Centring Spindle|
If you try to use Les's first method on a mill without a DRO, relying on the feedscrew dials, you will almost certainly get an unacceptable error because of backlash in the feedscrews.
|Thread: Myford Super 7/7B|
I would definitely recommend you keep the 3 phase and get a VFD. The advantage of this is that you have infinitely variable speeds, and can change on the fly. This means, among other things, that when facing a large diameter piece you can start slow and speed up as the diameter reduces. The motor is also smoother.
I Replaced the 0.5 HP single phase motor on my S7 with a 1 HP 3 phase + VFD (package from Newton Tesla) a couple of years ago, and the improvement is significant.
|Thread: Collet Chuck set.|
Tracy Tools sell sets of screwed shank milling cutters at quite low prices. They are very readily available, though normally not as cheap.
|Thread: modern Digital aids|
This is standard for ISO metric threads - the male thread has a truncated form of exactly nominal diameter (and in practice is often rounded off within this profile) while the female has a root which is rounded and deeper than nominal diameter by at least 0.0504 times the thread pitch. The nut thread crest is likewise truncated (at D - 1.082P) whilst the bolt root is deeper at D - 1.227P. This is done so that there is no risk of interference, even if the tooling is worn. It also has the odd effect that an ISO metric tap actually has a larger diameter than nominal.
Your deformed crests are 0.15 - 0.2 mm outside nominal, which may have been within the nut crest or just slightly more then the 0.08 mm gap in the nut root, but if it was more I would guess that, as a thin deformed crest, the excess was easily removed by the force of the spanner. Was it easier to turn by hand after the first tightening?
I generally screwcut male threads but (unless using a threading tool of exact profile) run a die down to give final form to the thread.
|Thread: Choice of collet mounting|
There are quite a few types of collet which can be used on a Myford S7 (see articles in past MEW magazines) but the two you mention are the most common. The Myford 2MT collets which mount in the headstock taper are excellent in quality and give the lowest (i.e. best) runout, and the lowest possible overhang, hence the highest rigidity. However, there are disadvantages: (1) they only work on material or tools of the exact diameter they are made for; (2) because of the fine taper, the position of the material depends on how hard you tighten the retaining ring; (3) they are b****y expensive, and (4) since the demise of the old Myford, availability is in doubt. They sell on eBay at around the new price. You need to get the closing ring and laoding tube to be able to use them.
The best type of chuck-mounted collets for the use you intend are ER collets. They are designed to hold a small range of sizes, and a full set of them will hold anything (round!) within the upper and lower limits. The ER25 set covers 0.5 mm to 16 mm, which is everything you could reasonably expect to use on a S7. Provided you use the correct tightening spanner and do it up properly, they will hold milling cutters perfectly well; I have used them on my milling machine for years, and only had a cutter pull out once when I got careless with tightening. There are several varieties of chuck for these collets: a 2MT type (which *definitely* requires a drawbar); a backplate mounting type (which can, done correctly, get the best accuracy on your lathe, but you have to fit it yourself, perhaps not the job for a beginner) and the direct mounting type which screws directly to the madrel nose thread. The latter is probably the one you should go for, not quite as accurate in runout as a well-done backplate mounted one, but perfectly good for milling cuttters.
Hope this helps,
|Thread: Clock making materials|
I may be mistaken, but I think the wire used by florists to make armatures for flower arrangements is soft iron. You may find most of it comes plastic coated, but some may not be. Maybe worth asking a florist, anyway. David
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