Member postings for old mart

Hi Paul, welcome to the forum. I don't think your ML7 will be much use with brake discs, unless they are for trials bikes. Your swing may be only up to 7" diameter, and even if you had a lathe big enough, the motorcycle discs are pretty thin and flexible for turning, more a job for a cylindrical grinder.

Hi Sandra, welcome, It's nice to get some young blood on the forum. In a few years time you will be giving us advice on how to do things, don't make it too technical.

Are you using inserts designed for aluminium? Grooving inserts seem to be elusive in the sharp grades. Some type of lubricant is required for aluminium, or it tends to stick to the cutters. Some alloys machine much better than others, pure soft aluminium is terrible to work with.

This is the sort of question which might be better on the Practical Machinist forum, they would be able to suggest the most suitable grooving tooling.

Edited By old mart on 24/11/2019 14:49:03

That's a big chunk of aluminium, it looks like you could slide the top and bottom forward to give a couple of inches more throat if required, although the belt drive might not allow it without some redesign.

I use er25 as well as threaded shank with the Osborn Titanic II. I never try to tighten the er collets on the machine, but use the standard length spanners by leaning on them using a worktop. I keep promising to extent the spanners to at least a foot to tighten them on the machine, that being the minimum length I believe would be acceptable for 12 and 16mm cutters. If the shank of threaded cutters is long enough to fit in an er collet beyond the threads, then it is safe to use. The threaded system is easier to use and being self tightening, possibly safer. They are not absolutely guaranteed perfect as the threaded part can snap off in extreme conditions.

As for tool height, if you use industrial type blades, I read the manuals of both Kennametal and Kyocera and both companies recommended 0.004" high if parting off solid stock. This would have been arrived at after the extensive testing that they do with their products.

Here is my version of a rear parting off toolpost for inverted blades. It has a top half which can be turned round for using either 26 or 32mm blades.The edges just have to be aligned parallel to the cross slide by eye or feel when tightening the SHCS for the blade to be at right angles to the axis. I added a rear saddle lock at the same time, using two helps the rigidity.

I think Howard's stiffening rod is the best method, hopefully something that just slides in with the minimum of clearance. It could have a tiny centre in the end for tailstock support. Or a larger diameter at the tailstock end and the shank made to fit in the tube. The tube clamped in the chuck jaws with the rod inside it would be much more secure. A number of tests would have to be carried out to find the optimum cutters, and a fine diamond hand lap to get the sharpest edge on the hss.                                                                                                                                                  As already mentioned, the carbide inserts for aluminium are very sharp, and may be suitable.

Edited By old mart on 19/11/2019 20:06:25

When you get a lathe to fit the cabinet, you will know how thick the raising blocks will need to be for comfort. You have two choices, raise the cabinet, or raise the lathe on the cabinet, the latter would need metal blocks drilled to fit both parts. Or a bit of both. I got the Smart & Brown at the museum lifted up by Rod using the forklift and a 40mm thick prefabricated wood plinth put underneath, it hasn't budged since, despite not being bolted down. The Tom Senior mill is also on a wooden plinth, but is bolted down.

3mm is the commonest size and is certainly my first choice out of 1.6mm, 2mm, 3mm and 5mm that I have. The 5mm are too big for parting on anything other than a very large lathe, but they were so cheap, I couldn't resist them, they may be used for grooving some day.

If you do a lot of threading with small stock, it would be worth getting a cheap ER11 collet with a selection of collets, or even an ER8, these small ones come with collets in 1/2mm increments, and can be bought cheaply on ebay.

I would sell both lots and start with something less proprietary. Sandvik is very good, but expensive, and there are much cheaper alternatives. I use blades in 26 and 32mm with Kennametal and Kyocera, but if starting out, I would get GTN3 inserts and a SPB263 blade. Most are Chinese, but Korloy also makes the inserts. These are 3mm wide, but SPB262 and GTN2 are 2mm wide.

The cheap ones will be just as strong/weak as the expensive ones, I destroyed one end of a Kennametal 1.6mm blade, and still have 9 inserts unused, the work moved in a three jaw chuck, so I prefer to have the extra security of a 4 jaw independent if parting is required. Making a dedicated rear toolpost for inverted blades is a great idea if you have a mill. I also added a rear lock for the saddle to stiffen things up further when using it. If I remember, I will take some pictures of it tomorrow.

I would advise against making an integral blade/post, sooner or later it will get smashed, the blades have two ends and can be replaced easily.

Edited By old mart on 19/11/2019 19:20:37

Edited By old mart on 19/11/2019 19:23:54

Pin vises sometimes require tightening with two pairs of pliers (and undoing).

Clarkson Autolock Osborn Titanic II / Posilock Acramil Small versions of these work with 1/4", 3/8", 1/2" and 5/8" shank threaded hss cutters, with the appropriate size collets and with the metric collets in 6mm, 10mm, 12mm and 16mm. The three types of collet are not interchangeable. Solid carbide cutters are not made owing to the weakness of the threads, but steel shank with inlaid carbide are available, and I have seen some indexable cutters with inserts in the large sizes. Larger versions are not really compatible with smaller milling machines. These types of cutter holder will only work with threaded shank tools.

Edited By old mart on 19/11/2019 17:21:29

A set of pin vises are handy when something small needs holding.

Good repair, if you hadn't described what you did, no one would know as it is invisible.

Good answer, Ian, I had not twigged the lever part. The mounting holes are either three at 120 degrees, or two at 180 degrees. There is no picture of the side of the chuck. And with further scrutiny, the plate with the holes screws to the centre and is locked with an axial grub screw, and two serial numbers match the fitted parts (and the jaws).

Edited By old mart on 18/11/2019 13:55:48

I noticed this brand new 100mm/ 4" Pratt chuck on ebay, which has obviously never been on a lathe, there are no threaded or plain mounting holes. Do you think it was originally a special order? I would have been interested, but I chanced upon a new one myself, by accident which has holes already which will eventually be used for small stuff.

https://www.ebay.co.uk/itm/PRATT-BURNERD-4-3-JAW-WITH-REVERSIBLE-JAWS-CENTRING-LATHE-CHUCK-2-SETS-JAWS/323983382320?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Df6b1c3208d3742eabdc4567fa0076e31%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D323983382320%26itm%3D323983382320%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Aea9e6c50-0a00-11ea-991f-74dbd1804aa7%7Cparentrq%3A7e89656c16e0ac3d187bd756ffeebd2c%7Ciid%3A1

Edited By old mart on 18/11/2019 12:44:45

The motor should have a plate on it which has the voltage, frequency, amps and rpm. You will need this information to program a VFD. A visual inspection of the windings will only be of use to an electrical engineer. You will also have to make sure it is in delta configuration, not star.

That's a good point, I had forgotten about the threads in 1-2-3 blocks.