Member postings for Andrew Tinsley

Hello Not done it yet!

I am in Edith Weston, I presume you must be in Stamford?

Andrew.

Thanks Bill,

A very kind thought. I should have enough bodies to cope with the moving. I just didn't want to get there and find some sort of monkey puzzle that delays or stops the dismantling!

Very best wishes,

Andrew.

Hello Bill,

Thanks for that. I am in Rutland and the Mill is in Hereford.

Regards,

Andrew.

From photographs, it looks as though the coolant pump is in the bottom RHS of the cabinet, at least that is what I think it is. No sign of a coolant tank, maybe a blessing !

Andrew.

Thanks both!,

Very useful information, I need to put together a toolkit to take with me, so the information that you have given on screw types encountered is much appreciated.

Thanks again,

Andrew.

I will need to do some serious dismantling to get a Centec 2B out of a cellar. I will need to remove the horizontal table and hopefully the knee assembly.

It will probably be obvious how these two components can be removed. But just in case there are any hidden snags, has anyone got any experience / advice on the subject?

The knee assembly is bolted down to the base by 4 (?) bolts. Can you remove these and the vertical gib (Sp?) strip (s) and then lift the assembly up to clear the dovetails on the main column? Assuming a couple of people could lift it! Are the threads Whitworth? If so, I need to search out my Whitworth spanners!

Thanks,

Andrew.

Hello Dave,

I understand from reading the Lathe UK site that the Centec was supplied with either a 3 phase 1400 rpm or a 3 phase 2800 rpm motor as standard. If so the Vertical Head has to be up to taking 2800 rpm, otherwise Centec would not have supplied the 2800 rpm motor.

Where I am confused is that the same write up states that there is a six speed gear box built into the Vertical Head. I need to recheck that, as it seems an odd way of doing things and perhaps I have misread the write up on that point.

Andrew.

I forgot to mention that this is childs stuff as far as potential explosions are concerned. Take a look at the video included in the post on "how do you bend copper tubes into a 5 foot circle". That is the sort of stuff I get involved with for relaxation!

Take a pole transformer and feed 240 volts into the secondary. This produces 11,000v at the primary. feed this into a rotary spark gap of a big Tesla coil and sit back and see 15 foot streamers striking everywhere. Now that is when I feel I would like to be in the next county! Oh you are pulling 50 amps at 240 V when it is working well!

Andrew.

Emgee the phases out of the 240 to 380 volt transformers will be 120 degrees out of phase, provided the 3 transformers are connected in the same way.

John, it also crossed my mind that the extra inductance would help clean up the waveform! VFD isn't required in this instance, so it will be strictly 50 Hertz.

Andrew.

I am the proud owner of a couple of Dickson units and maybe 15 toolholders. Nicely made by the person who used to make them for Myford. I am very pleased with them, but there are some drawbacks.

At least in the Myford size, they are less rigid than the old fashioned Myford clamping system. I do not think this is any deficiency in the manufacturing, simply in design.

The other snag is that if you are doing really precise, repetition work, they don't cut the mustard. I have a GHT 4 position tool holder and this gives appreciable better repetitive results.

I made this GHT design a goodly time ago and was muttering under my breath that I didn't really believe George's claim about the repetition accuracy. Well he was right! I got my Dickson system later on. It is an excellent way of swopping tools especially if you have oddball things.

It really depends on what you are looking for with your toolholder. The Dickson system doesn't have it all its own way! There is room for both systems. and I am honest enough to admit this! So reflect a little and don't divide into two camps over this subject!

Andrew.

A friend of mine is looking for a 240 volt (single phase) to 380 volt 3 phase invertor. They are a touch expensive!

Now I have a spare 240 volt (sp) to 240 volt (3p) invertor. I also have three 240 volt to 380 volt transformers. Can anyone see any objection to using one of these Txs on each of the 3 phases to give the required 380 volt three phase supply?

It looks as though it should work, the power ratings of the invertor and Txs match. Can anyone see a problem?. If not, then my friend has a zero cost (to him) solution.

Andrew.

Hello Andrew,

Thanks for that input. I assume that the quoted lowest speed of 85 rpm for the Centec is for the horizontal arbour. I am unsure about the geared vertical head, but it appears that the fastest speed is the speed of the motor. Until I get the machine I don't really know. According to Lathes UK. The gearing for the vertical mill is actually in the head itself. So quite where the horizontal speeds come from is anyone's guess, until I can get hands on!

If 85 rpm on the horizontal arbour is too slow, then some sort of speed reduction via the pulley belts look like an answer.

Andrew.

I would have returned it to Midland Abrasives, but probably to late now that you have tried to make it balance. A cup wheel should not have these defects. I would not even run it in the state you have it. Far too dangerous, I have had one wheel explode on me and it isn't a pleasant experience!

Best of luck,

Andrew.

Hello "Not done it yet"

I now have 3 phase, so using 3 phase motors isn't a problem, the ones I have can be connected in star or delta. I am a bit reluctant to half the speed on a 1400 rpm motor, cooling always bothers me. I suppose once I get it up and running, I can see if 85 rpm does the job and if not then I can always use a VFD. Suck it and see and don't worry until I have to!

Thanks,

Andrew.

I don't have a problem with high speeds for drills. I have a 3 phase, dual speed motored, high speed drilling machine for that purpose. I am not sure of the manufacturer. But the drill quill is supported by a vertical dovetail slide. It came out of a shadow factory that made Merlin magnetos. It was left there when the place was sold off and I eventually purchased it.

I am a little confused (as always!). I was under the impression that the Centecs came with a choice of 3 phase motors, both 1400 and 2800 rpm, these were supplied from new. So I suppose that 2800 rpm will be a safe maximum?

Looking at some ME books on vertical milling it seems that speeds as low as 30 rpm are recommended for some vertical milling. So Maybe I should go for the 1400 rpm motor and eventually use a VFD to cut the speed back.

As for horizontal milling, I suppose you do the speed calculation for the cutter diameter in the same way as for vertical milling. I am anxious to try out horizontal milling as it seem to be out of favour with model engineers. But then I do have a shaper and I just love to have an excuse to use it, so maybe I shall not be using the horizontal milling as much as I would like! Shapers are just great, I could sit and watch them for hours!

Andrew.

Thanks Jason.

You certainly are not kidding! There seems to be a couple of stones the right size. I imagine that I would want the finest grade? Which is the orange / brown material or perhaps the harder grain black variety?

My old stone could be either, but I suspect it might have been orange/brown in the first place!

Thank you,

Andrew.

Most experts recommend using a slipstone to fettle a lathe tool after grinding to shape.

I still have my father's "India" stone, at least that is was what he called it. It is approximately 4" x 1" x 3/8" and now appears to be grey, but that is probably due to usage and staining. I have used this to fettle my lathe tools after grinding and it gives a good finish to the tool and the work therefrom.

Now is this a slipstone, oft referred to for this particular job?

It is getting very worn and grooved and I would like to retire it from service, It must be at least 60 years old and owes me nothing. Where can I get another one or two of these useful stones?

Andrew.

Thanks Simon,

I suppose I was too lazy to do the cutter speed calculations! Well to be honest. I am always a little leary of the cutting speed in feet per minute, which are oft quoted. I suspect that the "industrial" speeds given, are for full flood cooling and pretty deep cuts. I am not really sure how to derate these speeds for amateur use! I tend to be a small cut man on most things. I don't like risking it on the "average" amateur jobs!

So 1400 rpm motor is the way to go. Thanks for that! I usually waste too much time in setting up machine tools and that has saved me half an hours extra work!

Andrew.

I shall soon be collecting a Centec 2B mill, together with the Mk 3 vertical head.

I have the choice of a couple of 0.75kW motors. The 1400 rpm version will give me spindle speeds of 85 to 1400 rpm (six speeds in all), while the 2800 rpm motor will give 170 to 2800 rpm.

So which is the most useful choice of motor. I have heard that things can get a little warm at 2800 rpm, so maybe the 1400 rpm motor may be the best choice?

This is my first mill, so I don't know much about useful spindle speeds.

Regards,

Andrew.

Edited By Andrew Tinsley on 01/10/2017 19:36:43

Thanks everyone,

Looks like Arc are going to get my order for the ER20 collet chuck. Thanks everyone for being so helpful!

Regards,

Andrew.