Member postings for Philip Sewell

I'm get a reading of 1.7 ohms across the leads John.

There isn’t continuity between the leads and the frame so to my logic the frame isn’t part of the circuit (please correct me if this is the wrong assumption). There is continuity between the leads which I wasn’t expecting, I need to gen up on how a dc motor actually works. The motor is magnetic.

I think designing a pwm circuit is probably beyond me but thanks for the idea.

I’m going to follow your advice John, I’ll be able to mount the power supply out of the way and have the potentiometer and a 3 way switch in the operating zone.

Thanks everyone, another learning experience for me.

Philip.

Thanks Martin. I had the dial set to the lowest, can you explain the initial split second of rotation and why it tripped the RCD when on the machine. I did wire it up to an old 12v lawn mower motor I've inherited, it again didn't start but made noises as if it was trying!

Philip.

I've had ideas to add a power feed to the z axis of my mill. I have a 12v dc motor off a golf trolley cart and rigged that up with a car battery to see if it would work and have the power to lift the apron and at what speed. All worked ok so I've made mounts for the motor and am ready to hook it up to permanent power.

I bought this from ebay

I temporarily wired it up this morning to the motor mounted on the mill but without the drive chain. The motor ran for a split 2nd then the RCD tripped.

I then took the motor off the machine and put it on the floor on a bit of carpet. It didn't trip the RCD this time, the motor ran for a moment then nothing happened. Obviously this isn't going to work, but I'd like to know why if anyone could let me know.

The unit is rated for 400w, the motor is 150w. Just done some calculations and the motor (I think) will be drawing 12.5A

As this unit is spec'd at 0 to 2.2 amps presumably that's why it's not working.

Ok, any ideas for running this motor, looks like I can forget about speed control.

Thanks, Phil,

Ok I now understand how the pull stud works, it helps when you know the name of something to google it, thanks.

I'll check the height of the l/h tool tomorrow, I wonder why the r/h tool is turned to a point. Also, why have flats been machined on the bases, and grooves machined in those flats.

Philip.

These parts came with a mill I bought and I've never found out what they are. I realise one of the parts screws into the int 40 tool holder, how does a draw bar connect onto it.

I've no idea what the other things are.

Any ideas,

Thanks

Philip.

Edited By Philip Sewell on 18/10/2019 21:53:12

Edited By Philip Sewell on 18/10/2019 21:57:21

I understand what you mean now Howard, I didn't appreciate that the gearbox bolted to the headstock was called a Norton gearbox. I subsequently googled it and all became clear.

Philip.

I obviously misinterpreted Howard's post. I have had the lathe for 15 odd years so it's not new to me. It has always been my ambition to strip it right down and replace worn/broken parts and get the lubrication system working properly and get it looking top notch. There are no issues with the feeds/threads gearbox, the problems were in the gearbox driven from the motor.

Philip.

Sorry for the confusion, the pinion gear was made very kindly for me by Pete.

I have added the images of the CVA lathe as this was the project that I needed the gear for and I all but finished it at the weekend (in hindsight perhaps I should have started a new thread).

Howard, thanks for your comments. I must confess I didn't appreciate locking the gearbox into one speed and using a VFD to control headstock speed would mean I couldn't get certain thread pitches. I assumed the speed from the gearbox controls the rate at which the thread is cut but the gearbox on the headstock controls the ratio between leadscrew and saddle speed.

Could you give me an example where you would have to set the gearbox driven from the motor to a specific speed to cut a certain thread so I can better understand you.

Many thanks

Philip.

Just to give some context to the gear thread I've posted some images of the lathe the gear is fitted to, now I've finally finished doing it up. The gear works very well by the way so thanks again Pete.

I'm not an engineer so I've learn't a lot about how a lathe is put together. As the gears in the gearbox were pretty mashed up I decided to lock the box into one speed (I put different pulleys on as well) and fit a VFD. I mounted the potentiometer where the change wheel for the gearbox would normally be. Nearly all the original switches etc have been removed although I've kept the one for the suds pump.

I plan on adding a DRO when finances allow.

Thanks again for all the advice about the gear, it's something I want to have a go at when I get the right kit for my mill.

Philip.

This is a lovely surprise Peter, really kind thing to do.

I have pm'd you re address details.

Many thanks for everyone's help.

Philip.

Good suggestion Nigel, I'm not really kitted out to accurately grind a fly cutter to match the gear profile. I think I'll do as you suggest with a suitable involute cutter as plan A, if that's not successful go on to trying to grind a cutter.

So it's fly cutting with a cutter ground to match the unworn profile of the gear.

Could you explain the term hobbing please, how is it different from cutting with an involute cutter.

Thanks for taking the time to research this for me Peter, much appreciated.

So just to clarify, I will be able to cut a replacement gear with a 14 DP number 7 involute gear cutter.

Depth of cut =3.8.

Philip.

Peter I am now in Norfolk working for much of this month (I am based in Leicestershire) so haven't got the part with me. I did use a gauge block fitting in the root of a tooth to get a measurement across the gear (ie caliper measurement minus gauge block width) and off the top of my head I think it came to 3.7mm, so the root diameter is (I think) OD minus 7.4mm

Hope that makes some sense to you,

Philip.

Thanks for all the input, I've got various options to think about. It seems that a 14 DP number 7 isn't going to work though. Fair comment about an imperial caliper, I've grown up on metric so not very comfortable with imperial and tend to convert if I can. I put a cheap dro on the cross slide of the lathe so I can work in mm, I'm intending on putting a proper one on the lathe when it's back together. Same issues with the mill which is also imperial, I have put a 3 axis dro on that which was well worth it.

Phil.

My method is to use 2 fences and a 12mm router bit. in a 1/2" router, I plunge cut so as not to put side pressure on the bit. I go onto a 1/4" router freehand for the face plate (not sure of the technical name). Having marked out the position of the plate with knife and marking gauge I freehand as close as I can to the lines and finish off with a sharp chisel. Using 2 fences is a great way of controlling the router and all but eliminates a mistake. If I make door linings I'll make the lining fit the door so I'm not messing about with heavy doors too much on site. I made 12 solid ash doors and linings for a mates farm house recently, I'd quite happily never make and fit another house door in my life!

Last question on this now that we have ascertained the dp. To cut this gear can you confirm this is the involute cutter I need.

14DP number 7

**LINK**

Phil.

Apologies Andrew the caliper reads 57mm, it is lined up as best as I could but being a tapered edge there's a bit of guess work but it's close (it's the camera angle making it look off position).

The same with the diameter on the gear, it's a bit chewed up so again the measurement might be slightly out, yes I measured the uncut part.

The pinion did work but the teeth are almost at a point. As I have the saddle off the machine I thought it would be a good idea to replace it if I can. Both the cross slide and compound lead screws are very worn. I have replaced the worn screw on the cross slide as it was a standard size, the compound apparently isn't. I was quoted £150 + vat for a one off so will have a go at making one when the lathe is back together.

Great to get advice from people that know, thanks all.