Member postings for RobCox

Try turners-retreat.co.uk. They have, in stock, a 150x20mm CBN wheel with a 32mm bore, 15mm of coating on the side face.

Oh, the optimism, finding an off the shelf item. I faced the same problem a year ago with my bandsaw. I searched high and low and in the end made a new worm and worm wheel as I concluded the original items were rough and poorly fitted.

The yucky mess once the glittery oil had been mopped out:

The worm wheel was so worn that it wouldn't drive the blade. Fortunately my M300, with the right changegear, can cut worms of specified MODs, so I made a worm and a hob. I made a new wormwheel by the free hobbing method, having gashed the blank first to ensure it started hobbing correctly first time:

And while the gearbox was apart, I changed all the bearings just for good measure. A lot of work, and not what I wanted at the time, but I failed to find an off the shelf spare.

I have a vertical milling head that I acquired a while ago and adapted it to fit the horizontal drive of my Elliott 00 mill, in the mistaken belief that it might make setups a little easier when cutting helical gears, as the normal vertical head swings way over towards the edge of the table leaving precious little room for a dividing head. Here is that head:

If it's of any use, I could be persuaded to part with it for a reasonable sum. It's 3MT in the spindle end, the drive I believe is a keyed 1inch parallel shaft:

The two steel plates make up the adaptor to fit existing screw threads in the mill - two holes partially overlap hence the two plates. I made up this drive shaft using an INT30 endmill holder off ebay:

I never got any further than stripping it down cleaning, greasing the bearings and getting it running on the mill. I have too many projects on the go to do anything else to it.

Please PM me if its any use.

Rob

I have 2.2kW VFDs running both my M300 lathe and Omnimill. Both are in IP66 sealed metal boxes. The Teco unit for the lathe is mounted on the back of the lathe, the WEG unit is in a wall mounted box. Both VFDs have (approximately!) the specified clear air gap above and below to permit air circulation. All the on/off and fwd/rev controls are taken via the control interfaces to remote switches (the original lathe controls in that case).

These have been running for 5 years now and have never given any problems, even with fairly heavy use from time to time.

So to answer to OP's original request, stick the VFD in a large enough metal box with no vents and it'll be fine.

Rob

A couple of places I've dealt with in the past could supply you. m-machine-metals have up to 4 inch square material priced by the inch. aluminiumwarehouse also do the same.

0.02mm play, or around 8 thou in old money, is definately not acceptable. On a deep cut the tool pressure will most likely push the spindle back and give more consistent results. On a light cut the tool pressure will do very little. With that much play, I suspect parting off is nigh on impossible.

I would check the adjustment of the bearings and nip them up, not too tight, just so the play is removed and the spindle gets no more than gently warm after a long period of running.

Bill, if it's any use to you, I found this hiding in a piece of brass offcut:

The threads are about 1/2" long, 0.437" OD 26TPI, the flats fit the spanner it's pictured with. If you want it, PM me with an address and I'll drop it in the post.

Rob

British Standard Brass is used for brass tubing, gas fittings and general brass work (quoting from machinery's handbook here).

It will be 26TPI, Whitworth form. Easy enough to make on the lathe if you've got the wherewithal. Whether you can find one off the shelf that easily is another matter.

From the shape of the guards, the position of the clutch lever and the stroke length indicator, it looks like it's either an Atlas shaper or a clone of one.

A quick google search produced a US website selling 5/8-56 taps with a review stating "needed for gunsmithing", so maybe thats where this thread finds a use.

What about using the old machinist's trick of putting a small piece of rag over the end of the drill whilst drilling. It certainly works for larger drills, say 6mm, but I've never tried it on anything as small as 3mm.

Another vote for using a milling vice to grip the key.

I have a small vice which, with the aid of a spanner, will grip the key sufficiently for the vice to be tapped with a soft blow hammer to gently drift the key out undamaged.

Advancing the feed on the backstroke is the way all of the advice I have read and watched has advised it. It puts less strain on the feed mechanism, especially if you're advancing more than one click on the ratchet.

Additionally, I tilt the clapperbox to ensure that when the tool lifts on the return stroke it moves in an arc such that the tool tip moves away from the cut face. Angle it the wrong way and the tool is forced into the cut edge. You'll know if you've got it wrong as it doesn't sound right and both the tool and the finish suffers.

The backstroke will always drag over uncut material. Whichever stroke the feed is increased on will result in a diagonal trajectory on the workpiece, without feed the trajectory over the work is in line with the ram.

Don't forget that the pawl should drive the feed on the return stroke of the ram and click during the cut

Personally I'm very happy with Weg VFDs. I've got 6 of them running various machines and have proved very reliable.

The instructions are comprehensive and they're in English, not Chinglish. The price is reasonable, not rock bottom or sky high.

Rob

The small triangle is 1/4 the area of the large one I believe.

The circle contacts the large triangle at the midpoints of the lines, so the triangle formed by the contact points has sides half as long as the large triangle. The small triangle must be identical to the contact point triangle being formed in the same circle. Half the linear dimension gives 1/4 the area.

Firstly, any deviation should result in a concave surface, not convex. 0.5mm in 100 sounds terrible to me.

It's not necessarily the carriage or cross slide that's at fault here. It might be that the headstock isn't parallel to the ways.

Correcting this isn't as simple as clamping it on a milling machine or grinder and having at it. Firstly an exhaustive examination of all the parts mentioned above would be in order to determine which part(s) are at fault. Next, removing metal from the saddle v ways would alter its height, resulting in less engagement on the carriage rack. If it's the headstock at fault the tailstock would need attention too.

You might have to decide if it's worth trying to fix as without the required expertise you might make it worse and write it off. If it were bought new I'd be angling for a refund or replacement.

Rob

When the half nuts are engaged the thread dial indicator shouldnt rotate. It indicates the position of the leadscrew relative to the cross slide, which is constant with the lever in the engaged position.

Acme thread cutting is best done single point IMHO. The threads, even 10tpi, would require a lot of effort to cut, and probably wouldnt end up straight. The width of cut becomes quite large and in my experience controlling chatter is an issue.

The change gears are set up for the thread pitch, irrespective of the thread form. Cant help you with the choice of gears though, as I dont have a myford and you havent specified the thread pitch.

Rob

I removed the swarf guard and fitted a replacement pair of half nuts (from arceurotrade if I remember correctly). I wasn't that happy with the off the shelf threading dial so I made my own complete with all of the gears needed for the various metric pitches. Having got use to the threading dial, I'd hate to be without it. It makes screwcutting quicker (and for me) more enjoyable.

Wear on the leadscrew hasn't been an issue... I upgraded to a bigger lathe and the mini lathe has been sat on a bench in the garage ever since, unused and unloved😥

I could try and pretend I'm really whizzy with maths by giving a solution, but I'm not, so I'll instead refer you to a youtube channel I've watched from time to time. The channel creator's name is Presh Talwalker and he solves this exact problem in his video " the ladder and box problem - a classic problem".

Me, I just got bogged down in quadratic equations that looked like they might turn into quartics...