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Member postings for Pete Rimmer

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

Thread: Paint for Colchester Lathe
21/05/2018 20:31:14
Posted by pa4c pa4c on 21/05/2018 08:43:11:

The only problem nowadays is finding good brushes at the right price. Surprisingly to me, rollers work well too.

What constitutes a 'good' brush? I've always run away from any kind of painting job partly because I find it tedious and partly because I always seem to struggle to get any kind of a good result. It could be that I have never tried to paint with a good quality brush.

21/05/2018 07:26:40

You can get decent results with roller and brush. It's how this was painted:

https://www.dropbox.com/s/1jizgb3szllic6h/bantamafter.JPG?dl=0

 

Edited By Pete Rimmer on 21/05/2018 07:28:25

Thread: Myford Super 7 VFD Controls & Clutch Switch
12/05/2018 20:35:04

What is the microswitch for Nick? An electrical interlock for the belt lever?

Thread: Metric ML10 lead screw threadform
25/04/2018 16:38:33

If you hand-grind a threading tool to within the half-degree difference between acme and trapezoidal flank angles you're some kind of superhuman. It's only half a thou difference at the tip of the thread at the pitch we're discussing.

25/04/2018 10:51:23

I just found a NOS set of half-nuts on eBay and the thread is quite roughly cast into the metal (zamak, possibly) half-nut. I guess that makes the half a degree half-angle difference immaterial.

https://www.ebay.co.uk/itm/MYFORD-ML10-HALF-NUTS-3-0-PITCH-FOR-METRIC-LEADSCREW-/352300339399

25/04/2018 10:05:37
Posted by not done it yet on 25/04/2018 09:30:22:

ACME is TPI and metric trapezoidal is pitch and never the twain shall meet - or at least they shouldn’t!

True that, but then my Denford lathe had a cross slide screw that was 1/2" OD x 2.5mm pitch. They just used the same material and cut a 2.5mm thread in place of 10tpi. Weird things happen.

25/04/2018 09:30:04

Pretty easy to get the angle with a gear tooth caliper and some basic trig. I guess I'll grind a 30 degree tool in preparation and check the original screw when it gets here.

25/04/2018 08:52:57

It's certainly 3mm pitch.

 Assuming the screws were made in house, they could easily have used the same tooling for both.

That's what concerns me, or rather that they might have used a 8tpi insert and set the lead to 3mm.

 

 

Edited By Pete Rimmer on 25/04/2018 08:53:27

25/04/2018 07:09:43

I thought the same thing about them all being 8tpi because of the ML7 being so but the screw is certainly 3mm pitch. It's confirmed on the lathes page that they did make metric ones.

I can't think why they would make a metric pitch screw with ACME form but you just never know.

24/04/2018 20:01:14

Evening!

Does anyone know if the metric lead screw for the ML10 is trapezoidal thread or ACME? OD is 16mm with 3mm pitch but I don't know the form or if it's full form or stub form.

If someone had a factory print that would make my day!

Pete.

Thread: Silver soldering contradiction
12/04/2018 23:30:48

In my work we have a guy that re-tips drill bits with silver solder. There's a spring clamp that presses the tips hard against the drill to solder them. These things see extreme duty and they are soldered with no gap.

Thread: Argon gas
08/04/2018 17:57:28

You can only get argoshield light on the hobby deal, not heavy.

08/04/2018 09:20:24

If you are using it for your hobby then BOC do a deal which is a lot cheaper than list. Current hobby price for argoshield size y is £47/yr rental and £35.71 fill with 79p surcharge. Plus Vat.

If you're a very light user and mean to keep the bottle for a long time then a rent-free would be better.

Thread: Trying to find some D1-3 back plates
01/04/2018 12:42:30

I've made a couple from steel and also from barbell weights but the weights tend to be too thin so the pin threads poke through. You also have to be careful with the locking screw hole because at first glance they appear to be on the same PCD as the stud holes but they are not. For my own use I tend not to even bother with locking pins I just drill and tap for the studs, screw them in and use it.

As for the taper I tend to make it snug. It's almost as shallow as a Morse taper and you can see those visibly move when you set a taper in your tailstock with a soft drift even after setting itin by hand, so there's more tolerance than you might think. A loose fit of course is intolerable for the camlock taper.

Thread: Correcting an off bored cylinder
23/03/2018 06:38:48

Is the hole in your chuck bigger than the cylinder hole? If so, turn and bore a piece of round or flat stock that plugs into the centre register of the chuck and superglue in in place on the flat end of the cylinder. Now use that plate to locate the cylinder centrally on the chuck, hold it tight against the chuck face using the tailstock ram and and snug up the four jaws with the soft packing until you have it held for boring.

Thread: Does 4 jaw chuck quality matter
19/03/2018 22:46:30

Not only does quality matter but suitability does too. I have a couple of Burnerd lightweight 4-jaws and whilst you can't question the pedigree of the chuck you do have to be careful how much you tighten the jaws or it's easy to put a deflection in the chuck face. I guess that's why they made them with such small screws and chuck key.

Thread: Lathe chuck not true.
02/03/2018 18:24:17

Grinding the jaws should only be a last resort IMHO and only after careful checks have been made. If you think about it, jaws are hardened steel and a very compact and strong shape. Chuck face is essentially a flat disc of cast iron with three slots milled in it. If something's going to go out of shape when abused it's more likely to be the soft iron chuck not the hard steel jaws.

I had a 4 5" PB chuck with severe runout that varied between 8-15 thou and I suspected the jaws until I put them into another similar PB chuck and they were perfectly fine. Turns out the slots in the front face of the chuck were dished and it was holding the jaws bell-mouthed, probably from being abused by over-clamping something held at the extremities of the jaws.

Consider also the commonly accepted statement that grinding the jaws is only good for the diameter they are ground at. That is exactly what you would expect if the chucks jaw guides were dished or domed.

Edited By Pete Rimmer on 02/03/2018 18:24:30

Edited By Pete Rimmer on 02/03/2018 18:25:01

Thread: Diamond grinding wheels
01/03/2018 00:56:22

I use diamond for stellite, usually I use it for grinding threading tools as it holds an edge so well. You can get it sharp enough that you have to handle it with care. Doesn't seem to bother the diamond, once again if used at slow rpm. Bit hard to find stellite now though.

28/02/2018 19:37:43

You can use diamond wheels to put an edge on HSS all day long so long as you turn the wheel slowly enough and even better if you use a little coolant. Electroplated diamond products have an initially aggressive cut but settle down to their 'normal' cutting rate quite quickly and stay there a long time so long as you don't overheat them.

Once worn beyond their normal usable life they can still be used to put a very fine honed edge on something but the material removal rate will be minimal.

Thread: Problem with Little John Mk2
25/02/2018 09:00:37

If you run the test cut again with a larger diameter part and you're still getting a taper then take a look at this video done by a friend of mine a year ago. He doesn't mention how or if you can adjust the spindle angle but I could ask him for you if it turns out you're turning a taper due to a mis-aligned headstock. Many lathes can be adjusted on the clamp bolts:

https://youtu.be/OfjVroJxs9U

 

Edited By Pete Rimmer on 25/02/2018 09:03:20

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