Member postings for Andrew Johnston

I'm not clear exactly which cutters from Arc are being used? I have not used their HSS cutters, but have tried their premium carbide endmills and was impressed.

The cutting parameters should be fine, but I suspect the mill column isn't stiff enough. Of course HSS cutters are less stiff than carbide so the cutter itself might be flexing as well.

Andrew

Of the austenitic stainless steels 303 and 316 machine very well, but for some reason 304 is a pig. It is possible to get a good finish on 316. However I can see a number of potential issues.

First what is the provenance of the cutters, manufacturer and supplier?

For a 10mm HSS cutter 2000rpm is way too fast, should be more like 500rpm, and that's based on recommended speeds for industry.

Work hardening is a real problem with 316. Taking a relatively shallow depth of cut means you need to feed faster than one might expect due to chip thinning.

The play in the column seems excessive to me.

I suspect the mill simply isn't rigid enough to take the cuts especially with conventional milling where the cutter will be rubbing at the start of the cut. Which is death to the cutter and the finish. It helps to climb mill, although I don't know if the smaller mills will be up to that?

Andrew

Dial test indicators are just that, indicators. They are not intended for measurement. In practical terms the cosine errors will be slightly larger with the larger travel. But not significant, provided the stylus is more or less at right angles to the direction of travel.

Andrew

Exactly what I measured. With the exception of the DTI sitting conveniently on the adjacent milling machine, which is heavier than the machine being measured.

The result is never going to be zero. Considering the results that Jason and I see, the obvious question is how does it affect the milling process? I think the answer is not much, if at all. Since the milling cutter is fixed in the centre of the saddle even if the table pivots around the end of the saddle the movement will be reduced by a factor of four or so, in my case. Assuming that cutting parameters stay constant then cutting forces will be constant, so the table won't be moving in and out with the cut.

My vertical mill is probably around 50 years old and consequently is fairly worn. So I expect that the same test with the table centred may well be worse. But until now i've never noticed, or worried about, the table rocking during a cut.

Andrew

Maybe I have misunderstood what measurement you are making. Let's say the table is central around the saddle. Where are you measuring to get your results; in the centre of the table, or outboard at one end?

Andrew

Out of idle curiosity I measured the movement of my vertical mill table when at one end of its travel. The table is 48" long and the saddle is 18" wide. With one end of the table lined up with the edge of the saddle that gives an overhang the other side of 30". With a reasonable push I could get a DTI on the edge, at the end, of the table to move ±0.1mm. I didn't lock the Y axis so that could be both X & Y movement combined. Dunno if that is good or bad, never measured it before and certainly never worried about it. Given that the cutter is operating in the centre of the saddle I can't see that smallish movements at the end of the table have any effect.

Andrew

Here's an opportunity to start acquiring the skill.

I take the tolerance on the shaft to mean the shaft should be 0.873" to 0.874". It's a rather old school way of specifying a tolerance, and tends to be frowned upon these days. Ideally a tolerance is specified as zero to a smaller/larger number, or as a plus/minus tolerance around a nominal value.

For the application I don't think backlash adjustment is needed. Presumably it is for a tailstock or capstan so the important movement is always in one direction.

Andrew

Given that the CP is rational then the DP has to be irrational. It is unlikely that an off the shelf gear will be found, so it will have to be made.

CP = 0.125 DP = Pi/CP hence DP = 25.1327 or thereabouts, which fits nicely the OD specified on the drawing

It is not clear if the boss below the gear allows a cutter at full depth to pass over it. I wonder if the teeth were formed by shaping?

Andrew

Some thoughts:

There is a certain satisfaction when using machine tools that move smoothly and consistently. A machine tool ought to help one make good parts, not be a hindrance.

The DRO moving when an axis is clamped is a fact of life. On my vertical mill the X axis normally moves 0.005mm, rather more on Y. It's now automatic to position the table to compensate. Plus, my DRO is accurate to 0.01mm, so no point in sweating over the odd 5 microns.

The backlash values on my ex-industrial lathe and vertical mill are generally large, in the 0.1 to 0.4mm range. That doesn't worry me in the slightest. On the lathe one tends to move in one direction only and on the vertical mill I have a 2-axis DRO. No idea what the backlash of the knee is on the mill, but on the odd occasion when I need accuracy the movement is always in the same direction; and the dial seems pretty accurate.

The DRO on the vertical mill is probably the single most useful accessory I have ever bought. I don't have a DRO on the lathe, and don't miss one in the least.

Andrew

Not many professional grade machine tools use traditional slideways and gibs these days. So finding a professional rebuilder will be tricky. Even if one can be found the cost will almost certainly be many times what the milll is worth. You may be lucky and some scraping will fix the problem. Or you might be unlucky and the mill will need some remedial machining.

Andrew

Whatever the solder the choice of flux seems unusual. The A8 flux is intended for soft soldering stainless steel and hence is quite aggressive, ie, contains acid. For brass to low carbon steel I'd use a low temperature silver solder and EasyFlo flux. Depending upon part size a micro torch won't provide enough heat.

Andrew

It's a female dog when turning.

Andrew

Are you sure the die is cutting a full profile thread? It sounds as if the upper part of the thread is being torn away by the die. That can be a problem with some of the softer aluminium alloys. I assume you mean aluminium alloy rather than pure aluminium, and if so which alloy?

Andrew

To an extent, but not always needed. In the picture in my last post the slab mill is cutting two steel blocks, total width of cut is 1.5". The depth of cut was 2.5mm. I tried a DOC of 5mm, but on the initial cut the work was lifted from the vice as there was significantly more upwards force than with a 2.5mm DOC. On the other hand in this picture there is nothing clamping the steel block down to the table:

There is a steel block clamped to the table out of sight on the left to react the horizontal cutting forces. The workpiece is held in place with the three eccentric hexagon clamps on the right. The DOC is shallow, just enough to remove the hot rolled scale. It's all about understanding the magnitude and direction of the cutting forces.

I am envious that you have the universal vertical head. The original thread for the MT3 drawbar will most likely be 3/8" BSW.

On my mill the arbors, and older accessories, are 5/8" BSW whereas for the newer facemills I have needed to make drawbars with M16 threads.

Andrew

It is straightforward to mill hardened HSS with carbide cutters. As shown below; milling an involute form on the end of a HSS toolbit for use in shaping an internal gear:

The question of hardness for a carbide cutter is a moot point, as the cutters are not homogenous. Instead they are made from fine tungsten carbide powder in a metal (usually cobalt) matrix.

Andrew

That's a good solid mill, will have no problem driving slab mills. Universal as well, which is a nice feature to have, especially if you want to make helical gears.

Like Nigel I have a Clarkson T&C grinder with the accessories to sharpen slab mills and S&F cutters. Thus far I've never needed to use it, but the facility is there when I do.

With a horizantal mill you really need to understand the cutting forces and clamp the work accordingly. Slab mills and S&F cutters want to lift the work, especially with deeper cuts. I learnt the hard way that the laissez aller clamping methods I could get away with on the Bridgeport are nowhere near adequate for the horizontal mill.

Andrew

Out of curiosity what is your mill? You need a good few horsepower to get the best from a slab mill:

Andrew

The mill looks to be Adcock & Shipley. I have an A&S 2E which is a universal mill, ie, the table swivels. The 2ER shown looks similar but older style, so I'm guessing 1840s/50s. I can't immediately see how the table swivels, so maybe it doesn't.

Looks to be pretty well equipped, although again there are questions; is the dividing head universal and if so does it have the banjo and gears?

Looking at pictures on the internet the 2ER doesn't seem to have a pickoff on the left hand table side for universal milling. So I wonder if it was a cheap version of the 2E with the universal facility deleted?

I use my A&S 2E a lot, but a horizontal mill is no substitute for a vertical mill. Ideally you need both. Here are some pictures of my 2E in action:

There are two caveats. One, these are heavy mills, mine is 3500lbs, so for me at least that means commercial movers. Two, mine has a two speed, pole switching motor, so to get the best out of it one really needs a proper 3-phase supply.

On the net 2E/2ERs are advertised at £2-3k. Depends how keen your friend is to be shot of the mill, but I'd offer up to about £1k.

If you have the space it might be worth offering a job lot price and taking everything away to be sorted later.

Andrew

Far more likely that the HT isn't exactly 7mm and/or that as the lead is pushed in the rubber coating bunches up and expands slightly. I'd go up in increments of 0.1mm until the lead fitted.

Andrew

For welders radiated emissions might be more of a problem than conducted emissions.

Andrew