bantam 1600 electronic problem

[Andrew CresseyParticipant @andrewcressey80402]

Thanks Jason i use wd-40 as a lubricant i know it doesn't cool but helps cut.So you are saying 800rpm is to slow,why does it move so quick then is that normal for it to take about 4 sec to do 100mm

[Howard LewisParticipant @howardlewis46836]

The finest feed that I use works out bat 0.0025" /rev, with either replaceable carbide tips or HSS.

My lathe (NOT a Colchester ) was built with 12 speeds (including Back Gear ) by a 2 sheave motor pulley, and three sheave pulleys inside the Headstock .

The original single phase motor was a 2 hp, but for the VFD with a 240V three phase motor, I chose 1.5 hp

Only one sheave of the pulley on the 3 phase motor can be used..

So far, cannot recall taking a cut deeper than 0.100" ( 2.5 mm ) deep.

Being idle, I usually leave the belt on the middle sheave, and vary speed by means of the VFD, although, often it runs at full speed.

In top "gear" it becomes clear that the drive train is is not in perfect balance (Probably the spring loaded driving pin in the bull gear throws things out of balance ).

FWIW my advice is worth, put things back to original, as much as possible but fit a VFD and 240V three phase motor, of the same power as the original. The VFD will give you an almost infinite variety of speeds. Since the VFD can run upto 75 Hz you might need to change the motor and driven pulleys, to limit top speed to 1600 rpm..

HTH

Howard

[Andrew CresseyParticipant @andrewcressey80402]

Thank you Howard i have another question for you all.I live in a council house so if i need a 16amp fuse it will cost £500 by the council to fit.I enquired with numerous electricians and they wouldn't touch me because of regulations with the council.Will a VFD run this lathe on 13 amp ?

[JasonBModerator @jasonb]

Sounds like you have a very coarse screwcutting feed selected and are engaging the leadscrew half nuts rather than the feedshaft. The middle of your 3 shafts should be turning when cutting not the leadscrew at the top

May also be you have a screwcutting gear train rather than a feed one which will mean the input speed to the gearbox is far too fast. You need to take off the end cover and see what gear train you have. You want one of the gear trains bottom left of the headstock charts

Edited By JasonB on 22/12/2021 19:14:58

[Howard LewisParticipant @howardlewis46836]

My VFD runs off a suppressed 13 Amp socket on single phase ring main, fed from a RCD in the house.

It has run like this since installation in September 2003 without any problems

The socket is suppressed to prevent any nasty spikes that might go back into the mains and upset our house, or any other on the same phase.. Probably an overkill..

1.5 hp plus losses in the VFD will probably amount to less than 2 Kw (Just over 8 Amps ) total, so a 13 Amp single phase socket will be below its maximum loading of 3.2 Kw.

When measured, the current draw has been well below 8 amps, nearer half of that, so I have not been using the full power of the motor.

So you don't need a 16 Amp feed for VFD, just plug it into a 13 Amp socket..

Howard.

[Howard LewisParticipant @howardlewis46836]

Unless screwcutting, you should be using the gears to set the feed rate.

0.004" /rev will do for finishing cuts, possibly 0.016" / rev for roughing.

Most of the time you will not be making 4 tpi Leadscrews!.

The coarsest thread that I cut was 4 mm pitch, x 1.5 mm deep, and for that, i used Back Gear to keep speeds low.

Your Colchester may not have back gear, but at minimum speed, especially with VFD will probably be slow enough to cut threads without a need for lightning fast reactions, WHEN you get to that stage, which is unlikely to be for a while.

become familiar with the machine before doing anything complicated with it.

Read a few books on lathe work, for guidance, even if they deal with hobby lathes rather than an ex industrial machine like yours. The principles are the same, just that the details will be different.

Buy a set of Zeus Charts – an invaluable reference

.Ian Bradley, "The Amateurs Workshop"

L H Sparey "The Amateurs Lathe".

Harold hall – "Lathework"

Neil Wyatt "Lathework"

Later buy Tubal Cain "Model Engineers Handbook"

What you spend on books may save you wasting material, or damaging the machine, and will teach you the way to go about things.

HTH

Howard

[JasonBModerator @jasonb]

Howard, the input speed to the gearbox needs to be set with change gears for feed rates, there are three change gear options N, P & Q. You can then use the gearbox to get six speeds for each of those change gear combinations.

If the change gears are one of the combinations for screwcutting then the input to the gearbox will be far too fast and no matter what position the "joystick" is in the carriage will move far to fast.

I hope the lathe came with it's change gears

[EmgeeParticipant @emgee]

There's no need to faff with pulleys to limit max speed if you are running with a VFD, adjust max Hz in the parameters.

Plenty of choice of feedrates provided the correct gear train is fitted.

Emgee

Edited By Emgee on 22/12/2021 19:49:33

[JasonBModerator @jasonb]

It's a Mk2 so different charts.

Here is why it is important to engage the feed screw for turning and not the lead screw.

On the left are metric screw pitches, on the right metric feeds. I've highlighted gear train "P" , 3 position knob in "S" and joystick in "2"

If you engage the feed shaft the carriage will move at 0.15mm per rev, if you mistakenly engage the leadscrew when you actually want to cut it will move at 1.75mm per rev. Now if you apply that to the 800rpm being used in 4 secons your tool will move 93mm in 4 seconds which is close to what Andrew says he got when it should have been a sedate 0.15mm/per rev which would have covered 8mm in the same time.

For feeds you should be using the lever middle bottom of the apron and for screw cutting the lever on the left of the apron

Edited By JasonB on 22/12/2021 20:23:26

[Andrew CresseyParticipant @andrewcressey80402]

Thank you well at least i can use a 13 amp socket thats one thing sorted.As for cutting i always use the bottom middle and the same for the cross feed.I will check the change gears to see what gears he has been using.

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