Member postings for Pete Rimmer

What's your reasoning for not exceeding 70hz on the drive Neil? Most lathes have 4-pole motors which will happily run at the speed of a 2-pole.

There's no compulsion to use carbide at high speed if the circumstances prevent it. Thread as slow as you like, but beware you might suffer broken edges on the tip of the insert especially if you stop the spindle with the tool in the cut or don't have a groove to run into. I've been cutting 1.5mm threads today at 200rpm with a hand-ground carbide tool (ground from a busted end mill) and I've had to re-grind it several times after breaking the edge. HSS wouldn't stand up to it at any speed in this material. The task doesn't allow for a groove so I've been manually retracting the cross-slide and a couple of times I've missed-timed it then off came the tip.

Howard makes a good point, especially for older lathes now fitted with quick change tool posts. Lathes which originally would have had a lantern toolpost hold the tool on or very near the compound's swivel centre-line so a travelling steady would would be designed to sit just to the left of centre. 4-way toolposts and more recently quick change tool posts have much more width and hold the tool much further to the left, in a position which is likely to clash with the steady.

I've had to fabricate a steel travelling steady for one of my lathes for which I have the original item because of how awkward it was to use when making leadscrews.

Hi David,

The threaded stud on the end of the capacitor canister is simply there for mounting purposes.

When you remove the cover from the terminal box you'll see the two power connection, which you have already identified, and the earth connection which is typically a tapped hole in the casing usually in one corner of the enclosure under the lid. There should be an 'earth' sign cast in the surface right next to the hole. If the motor is really unused there's a high probability it will also have the screw in it.

You're nearly right. The pitch is still 1.25mm, but the LEAD is 2.5mm If you specify 'Thread 8mm, 2.5mm pitch, 2-start you'll' either get a 5mm lead thread or (more likely) an irate phonecall asking what it is you really want.

So ask for 'Thread, 8mm OD, 2.5mm lead, 2-start'

Pull the jaws out of the chuck. Set the chuck so that one jaw slot is perfectly horizontal (at the back or the front) and run a tenth-reading DTI along the jaw guide (with the mag mount set on the cross slide). If the dial reading goes up or down rotate the chuck 180 degrees so the slot is now pointing the opposite way and repeat the test using the slide on the same range of travel i.e. don't wind the cross-slide to the other end, re-position the mag mount.

If you get anything but the same reading with the jaw slot at the front and the rear, your chuck is fubar.

I bought a lathe (also a Bantam, ironically) which had a Pratt Burnerd chuck that produced variable runout in the part between about 8 and 15 thou. The jaws were a good fit in the slots, didn't appear worn and there was nothing obviously 'wrong' with the chuck except that it had runout.

Turned out that the chuck was slightly bell-mouthed. Gently holding a part in the jaws meant that you could rock it around as it was only held on the very back of the jaws. The jaws were perfect, it was the body of the chuck that was deformed. This was a 4-1/2 inch Pratt Burnerd integral camlock chuck so a good quality item, I guess that sometime in the past someone must have really wrenched down on a part held at the end of the jaws or maybe had some other even where the part was torn out, permanently damaging the chuck body..

Soon after I bought a tidy 5" PB chuck that only had outside jaws so I tried the jaws from the bent 4-1/2" chuck in the 5" one and they consistently gave better than 3 thou runout on both the inside and outside sets.

The main point of the story is that it's common to immediately suspect worn jaws or a worn scroll and often the attempted 'cure' is to grind the jaws but don't jump to this conclusion too quickly - hardened steel jaws are tough and slow to wear, iron chuck bodies not so much so do your investigations before grinding parts that might have nothing wrong with them.

If you have a lathe like a Bantam with a pedestal each end firmly bolted to the bed then you should both level (align, actually) and fix the lathe down to eliminate bed twist because it takes no effort at all to twist the bed if it's set on any kind of uneven floor (even floated concrete floor isn't flat).

Currently I'm refurbishing a South Bend lathe which is the old design of headstock base casting and tailstock legs, this absolutely must be levelled and fixed if it's to work as intended and keep doing so.

A few tenths, but not a few thou. You wouldn't even start scraping a few thou of wear unless you had no choice at all, you'd mill or grind it first then scrape it once you were closer than a thou or even half.

Hell no - I learned it s part of the scraping and rebuilding class.

Grinding a mill table can often do more harm than good. A bit of surface pitting won't hurt once you've stoned the surface rust off but milling or grinding it can easily make a banana of what once was a straight table.

As in the dialect they might speak in New York's largest borough?

If this isn't some kind of subtle joke, it's quite funny anyway

Good quality aluminium will hold fine threads no problem. I re-built a bike engine to allow for 3x the power via a turbo and I drilled & tapped the cases for 12mm x 1.25 pitch head bolts which is extra fine (originally M10 fine) and the main bearing bolts (from M9 fine) . They were torqued to 75lbs/ft in 2007 and that engine's still going strong today.

One thing that catches many novices out is that often threading a piece of stock will raise a burr which makes you think that the thread's not deep enough when in fact it's binding on the major diameter when you try the nut. You start to wonder if you've got your sums right because you've hit the full depth and the nut is nowhere near fitting so you keep taking cuts until the nut fits but then you find it's a sloppy fit and you don't know why.

Use a caliper to keep an eye on the OD after you have taken a few passes. If it's started to grow because you've pulled up a burr just carefully run over it with a flat file taking long smooth strokes as the part is turning. On a vee thread it won't take many strokes but on an acme/trapezoidal thread you might have to go at it several times to file the burr down to the correct OD.

A 'crotch centre'.

The negative of the L4 stamping at 8 o'clock on the right side is quite clear to see at 4 o'clock on the left. You have the orientation correct in the pic, just flip one side over on top of the other.

You don't even strictly need a button. I made my first single-point cutter by first making a fly cutter of the same diameter as a button then cutting both sides of a piece of gauge plate with the head of my mill tilted to give the form with some relief.

If you get stuck Frank I could possibly cut those gears for you, though you would have to cut any keyways required as I have yet to lay my hands on a broaching cutter set.

1. Get a decent piece of HSS

2. Grind a RH roughing tool with a ridiculously steep top rake and generous front relief.

3. Watch it slice off material like butter on your low powered lathe.