Member postings for old mart

Can you take the old one apart and show us the works when the new one arrives? I would guess that there is a valve kept open by a very weak spring on the downstream side but I have never heard of one of these. I think they would work well if the pipe was severed, but not so likely if it just leaked.

I am lucky to have some Morse taper sockets for capstan lathes, they are different od's and ground true. Also, I have various sizes of ball race inside and outside elements kept mainly as parallels for milling. With care and testing, even the inexpensive Chinese and Indian chucks can give pretty good results. At the museum, there is a Chinese K11 125mm Huhhot chuck, made in 2003 which is the equal of any of the PB chucks we have. Unfortunately they seem to have gone out of buisiness.

I mark the best socket with a small scratched cross, just in case the sweet spot changes in the future.

Edited By old mart on 04/06/2021 16:00:04

Having a machine that has a mechanical gear reduction, belts and pulleys or gears has an advantage over a machine with only speed control via the motor. With drilling, for instance, the larger the drill the slower speed needed, but also more torque to turn it. Slowing an electric motor to half its nominal speed looses 50% of its power and slower than that its much less. This is where the gearing comes into its own, even if it takes more time to set up.

Welcome, Dan, you should take a look at the Warco, ARC or Chester links on this website. ARC helpfully show the space taken up by their machines, which is good if you have a limited room in the workshop. If buying new and there is a choice, go for an R8 spindle fitting.

Edited By old mart on 04/06/2021 13:12:58

I have never noticed any difference in depths of PB key holes, so after cleaning, the pinions get put in any position when re assembled. It seems a strange thing to have shallow holes, as the 3 positions are intended for convenience when loosening the chuck jaws, saving having to turn the spindle. Six jaw chucks are more likely to have only one key pinion, so that there is no choice either way.

Edited By old mart on 04/06/2021 12:09:17

In the workshop. I have a magnet on a 2 foot long handle, and a smaller one on a telescopic handle.

Robins take on the height of the tailstock is correct, fortunately, as the same applies to worn lathe beds where the tool height varies as the saddle is moved. The error would be relatively greater the smaller the workpiece diameter is, and would also be subject to the distance between the spindle and the tailstock.

It is best to have the tailstock at or less than 0.002", 0.050mm high, as it can make centre drilling easier.

Edited By old mart on 04/06/2021 11:57:37

I had never considered the numbering of the scroll sockets. When I check for the best performing socket, I try with bars of different diameters and choose the socket with the least averaged errors. With a scroll chuck there could be three different master sockets in theory, with inside jaws the clamping is only inwards at the centre, but outwards for the steps. With outside jaws, the clamping should be only inwards, the outer part of the jaws is not intended to hold work. This may not be true if the chuck has two piece reversable jaws.

I have found the best socket, got the chuck body running true, and then set up the jaws for grinding. The best PB 5" is very good for a scroll chuck, 0.001" or better at any diameter when its clean. If better is required, the register is loose for a poor mans set true.

Back in the 70's the small firm I worked for had a Myford ML7 and a new Super 7, they both had Dewhurst switches and no other way of switching the motors on and off. The common no volt safety switches had not appeared that early.

Shame, I bought some of their middling quality ones a few months ago, they are very good.

When you look at the tolerances on both types of chuck and find they are the same, it is obvious that the extra price pays for somebody to do those tests which the buyer could do for themselves just as well. I tend to be suspicious of makers who do not put the country of manufacture on their products, all the P, PB and B chucks that I have are marked made in England.

Edited By old mart on 03/06/2021 18:21:57

You were lucky to break the screw and not the gib, now you need one of those screwdrivers with a ball end hex end.

Welcome, Paul, when I cut external threads, I always take a just visible cut first and then check if I have got the pitch correct.

I often look at the thread charts on thr Motalia website, they can be useful.

https://www.motalia.co.uk/

Edited By old mart on 01/06/2021 21:46:48

That leadscrew on the lathe could do with some protection.

**LINK**

Peak4, the two odd drills are showing the characteristics of solid carbide. Its a shame they are too long for safely starting a hole in hardened steel. You could try a file on the end of their shanks, HSS would file.

I have never seen the MT holders before, but holding straight shank drills or taps without needing a chuck would be my guess.

Looking at the "Lathes UK " website, you should look into ways of raising the spindle height of your lathe to match the tailstock. I think that is the easier option. 0.5mm shim is available and might be used to raise the left hand end of the lathe. Lowering the tailstock would be possible, but harder to do. There are lots of Unimat people on this forum to tell you if this is feasible.

One thing has just occured to me regarding chucks screwed onto dividing heads, or rotary tables, is the danger of the chuck unscrewing if the cutting forces are in the wrong direction. This is certainly a factor with lathes if nothing is done to lock the chuck.

There is no photo showing any female thread, which fooled me as I assumed there was.

An extension will loose the stiffness and be subject to some runout and will only be good rather than very good on any spindle other that the one it had the male threads and register produced on. That one must be a one off made for a special job, but what that job was defeats me.

I have just come across this ebay listing for a Super 7 spindle extension, I recon it is 70mm effective length. What would it be usd for?

**LINK**