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Member postings for RobCox

Here is a list of all the postings RobCox has made in our forums. Click on a thread name to jump to the thread.

Thread: What are members thoughts on Gap Bed lathes ?
03/10/2019 13:15:58

I don't see a problem with a gap bed. For hobby use you're probably not going to be pushing it hard enough for the gap to make a difference. From a rigidity perspective, I would have thought that the bed with or without the gap piece would be much more rigid than the tool fixing, toolholder fixing, topslide and probably the saddle gibs too.

Whether you'll ever need the gap is another question that only you can answer Maybe, like a lot of tools that I have, great for one job every few years.

Rob

Thread: Brown & Sharpe 2L surface grinder - drive gear teeth pitch?
20/09/2019 21:19:39

As you have a rack, you should be able to determine the PA with a protractor. I'm in a similar position to yourself in that I have an Eagle surface grinder that I'm putting back together. In my case, the rack and gear are just worn, but there are enough good teeth on the end of the rack to determine it's MOD 2 with a 14 deg PA.

20/09/2019 21:11:47

See the first link in Brian's post above. That's exactly the material the commercial offering would be made from.

Thread: Mill hand wheel upgrade
20/08/2019 09:02:30

When I renovated my elliott mill I junked the original handles as they were plastic and looking tatty. I replaced them with some nice cast iron ones from wdsltd.co.uk (usual disclaimer, no connection, just a satisfied customer).

They do a range of sizes, materials etc. Just one word of warning - the keyway will cost you! I bought mine without a hole as I needed to bore it to fit an imperial shaft and cut a keyway on the lathe (doubleboost style). As an example, a 100mm dia cast iron wheel is £11 + VAT without keyway, £25 + VAT with!

Rob

Thread: lathe part supplier asking questions over my head...help
14/08/2019 10:51:09

Hi Chris,

Not surprised they don't stock such a thing. There's an infinity of possibilities for the radii and whether it's to cut an internal or external radius, hence the suggestion of grinding your own.

A radius gauge is kind of like a feeler gauge, but instead of the thickness being the calibrated dimension, it will have either a protrusion or cutouts with a specified radius. To use it, you'd grind a curve on your tool then hold it in the cutout in the gauge up to the light to see how well the tool matches the gauge curve and grind the tool to adjust as required.

Rob

Thread: My bench grinder let out the magic smoke
14/08/2019 08:25:33

Saturday, as I was grinding some HSS toobits for a boring job I needed to do, my bench grinder got very hot on the case. Can't do without it, so I carried on. A short while later there was a small pop! followed by a puff of smoke.

I turned it off pronto, thinking how long was it going to take me to get a new grinder if the motor windings had cooked. I dismantled it from the stand and took the base off to look for problems and there it was..

20190810_152720.jpg

The windings looked ok through the cable hole in the base of the case, so I guessed it was just the cap that had popped. I had a 2uF motor run cap handy, so I wired that in, and the grinder started up, albeit slowly, enabling me to finish the job.

The cap had let go so the value on the case had conveniently been erased by the goo that leaked out, so I emailed Warco, in hope rather than expectation, as to what value cap is fitted.

Hats off to them! Got a reply back on Tuesday. 10uF 450V. Have acquired one for RS, now fitted with a shiny new bracket rather than a bendy p-clip. The grinder starts as before the incident.

20190813_175827.jpg

Rob

Thread: Harrison M300 or M250 pulley/belts problem
09/08/2019 11:12:49

I replaced the belts on mine whilst I was renovating it. I don't remember having any difficulties there, other than adjusting the motor, as the bolts are inaccessible. I certainly didn't have to remove bolts that hold the headstock to the bed. If I had, I'd probably have lifted off the head and cleaned out the ton of swarf thats jammed in under it.

If you could post a picture of what's causing you trouble I'll compare it with mine and let you know what I did.

Rob

Thread: Any uses for an old tired lathe bed
03/08/2019 16:55:54

Raw material for your next project?

Thread: Aldi bargain laser level
15/07/2019 09:17:32

Concerning the use of acronyms, we had a case at work where one of my colleagues complained to a customer that their documentation contained too many TLAs that they hadn't defined. Their response was "what's a TLA?".

QED

Rob

Thread: Using a pillar drill for milling?
22/06/2019 21:22:53

If you want to find out how good a drill will mill, try searching youtube for AvE - turning a drill press into a s__tty mill. He does exactly that.

Thread: Horizontal mill cutter
18/06/2019 08:14:15

Hi George, when I acquired my Elliott horiz/vert milling maching I also got a TC grinder to go with it with the intention of buying used dull horizontal cutters and sharpening them. So far it's worked well. Blunt cutters are cheap and my restored Union grinder sharpens them well.

If your cutters have a 1" bore I might be able to help you out. All my horiz cutters are 1" - smaller bores would require new tooling to fit the grinder.

As for your motor, my mill has a 2hp motor for the horizontal drive, with pulley & belt speed reduction to 100rpm minimum, driven by a vfd. The minimum speed is a tad on the high side, although with the way I have the vfd configured I can use that to slow it down a bit without losing torque. Even with sharp cutters, the mill struggles with cuts deeper than about 40 thou on a 1/2" wide cutter. There's a whole host of things that could be wrong here, starting with the user(!), but I'm guessing blunt tools plus an underpowered spindle may contribute to your problems.

If you PM me maybe I'll be able to help you out. May take a while though, because I don't get too much shop time these days..

Rob

Thread: Door knob collar
15/05/2019 19:34:14

A form tool might be too much of an ask for that large a curve, so I'd opt for shaping it freehand with a graver. Depends how confident you are with freehand turning. I've 20+ years of woodturning experience and have used that to shape machine handles from steel, so a bit of brass shouldn't be too difficult.

Rob

Thread: Cheap DRO for Mill
25/04/2019 09:22:31

I fitted a 3 axis DRO from Machine-DRO to an SX2 mill a few years ago. I bought magnetic scales as they were more suited to the size of machine. When I sold the mill (minus the DRO!) I moved the DRO onto my Elliott mill. I only needed to buy new magnetic scales - which are comparatively cheap - to adapt the different travel lengths. The read heads are the expensive bits and they just needed new custom mounting brackets to suit.

Thread: Colchester student 2500/harrison m300 feed gearbox cams
28/03/2019 08:31:54

Hi Damian,

I took my M300 gearbox off a couple of years ago when I gave the whole lathe a clean up and fixed broken/worn out bits. I took a lot of photos of the gearbox at the time in each of the selector positions.

I'll try and dig out the photos tonight and post them in an album. They may help you deduce which cam goes where.

Regards

Rob

Thread: Filing A Curve
28/01/2019 08:09:19

I was taught to file curves the second way you describe, with the file following an arc in the opposite direction to the arc you're filing on the workpiece. I guess you're trying to use more of the length of the file, rather than clogging up one short section with the waste.

When drawfiling on the other hand the arc of the file follows the arc on the workpiece, but then the file's perpendicular to the work so rolling it the other way ends up digging in the file edges and less material is being removed anyway.

Rob

Thread: VFD recommendations
15/01/2019 08:54:13

Hi Peter, If you run two motors on one VFD you'll probably have to start and stop them at the same time. VFDs don't like switched loads downstream.

The coolant pump is probably <100W - mine is - and all you need to get that to spin is a capacitor and a double pole switch. The connection is as follows:

steinmetz.jpg

The capacitor value I used was 8uF, 440Vac. I used a motor run capacitor from RS, which will only cost you a fiver plus the switch. My pump motor has 440V star connected windings with no provision for configuring to delta, but it still runs just fine on 240V.

This will enable you to optimize the VFD settings for the main motor (startup, run-down time). I wouldn't be without the variable speed - it saves a lot of belt changing - and if you have chatter you can drop the speed quickly without having to stop a cut, so I'd stick with the 3-phase motor and a VFD rather than go single phase.

14/01/2019 09:37:32

Sounds like you want to do a similar thing that I did to my Elliot mill. In my case, I stripped out the spaghetti that was the original wiring, junked the original control switches and effectively started from scratch with the electrics.

I started with a pair of WEG inverters - 230V types. The motors are not reconfigurable to delta, so I used the tehcnique described in the inverterdrive.com link to set the parameters. One VFD drives the horiz/vert spindle motors (a 3 pole 2-way switch changes over the motor connected to the VFD but you can't change whilst it's running - but why would you!), the other drives the table feed motor. I located the VFDs, fuses and a NVR relay in a wall mounted enclosure with two umbilical conduits - one carries 3 phase to the motors and the other carries all the control wires to the control box. I relocated the controls (the original controls were at knee-height which brings your face closer to the "action" when turning on/off). I had two goes at the design of the control box before I was happy with it.

I chose the WEG inverters as the control inputs enabled me to control the motors as I wanted - start, stop, jog (rapid feed for table) fwd/rev and a speed control pot. I have a separate switch to disable everything at knee height for safety/emergency.

For the coolant pump, which works but I haven't used it yet in anger, I used a Steinmetz capacitor to provide the 3rd phase. Cheaper than a VFD and you don't need the variable speed on the coolant!

Some pictures for reference:

ctrl_box.jpg

controls.jpg

mill.jpg

Rob

Thread: Clean hands?
28/05/2018 20:22:31

From the looks of it I'm the only one who uses liquid soap - the sort from a pump action dispenser. No water at first, just soap and an old non-stick washing up sponge as a mild scrubbing brush. Once the soap has lifted the oil and grime, it washes off with water.

I sometimes use nitrile gloves, but they set off my eczema, so they're reserved for jobs using solvents eg white spirit.

There's an additional benefit too - the springs in the dispensers come in handy for projects later once they're empty.

Rob

Thread: Heating Tapes for Machine Tools
18/04/2018 13:48:57

Not such a daft idea - there's a posting on another forum in which the OP describes exactly that scheme that he has implemented:

**LINK**

Thread: new to the hobby - first lathe
02/03/2018 13:13:54

I wouldn't be put off by transport - for less than £100 a time I've had two old machines delivered. The last lorry had a 30t capacity crane which popped the mill right on the workshop doorstep.

Personally I'm more in favour of a good old machine that a new one - you'll get more for your money if you're prepared to spend some time doing it up. Agreed, if it doesn't have the accessories that's a downside.

As for the QC gearbox, I started with a Sieg minilathe. Allen keys required every time you wanted to change feed rate or thread pitch, and no cross slide power feed. The old M300 I have now is luxury by comparison - just twiddle the knobs for feed change & metric/imperial threads. The power feeds give a better more repeatable finish too than I ever got by hand.

Rob

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