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Member postings for John Baron

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

Thread: Using Counterbores
04/06/2020 21:14:09

Hi Guys,

One thing that that needs to be accounted for when counter boring for cap head screws is that the shoulder under the head is a fraction larger than the clearance diameter. So the counter bore pilot is bigger to allow for that.

 

Edited By John Baron on 04/06/2020 21:14:27

Thread: Boxford AUD motor drive wheel plus reverse switch issue
02/06/2020 17:49:22
Posted by Fergus Davidson on 02/06/2020 17:25:56:

img_20200531_151341.jpg

Hi Furgus, I would have drilled and tapped the pulley directly over the key. That would stop any movement of both the key and the pulley.

Having said that I've also seen a screw put into a shaft to stop a pulley moving. In the old days a tapered key would have been used and hammered in. You might have seen them on old machinery, they had a raised section on the end so they could be extracted.

Thread: Belt Up
02/06/2020 17:21:39

Hi Guys,

I used to think that line shaft pulleys were flat, until you stood one up on a flat surface and it leaned to one side or the other !

Thread: internal grooves for o rings
02/06/2020 16:51:17

Hi Larry, Guys,

Making an internal boring bar and grooving cutter is not rocket science !

05-04-2020-002.jpg

This is a piece of 3 mm square HSS, ground to cut a 2 mm wide by 1.5 mm deep groove inside a 12.5 mm diameter hole.

05-04-2020-000.jpg

This picture shows the parts used to make the tool. As you can see it was made from and off cut of 8 mm all thread. Threaded bar for those that don't know what it is. The grub screw is M5 X 6 mm.

05-04-2020-005.jpg

This last picture shows the grind on the tip. Its a bit difficult to see here but the top has about 5 degrees of rake.

This tool is intended to cut grooves for Teflon "O" rings with a 12.1 mm bore, so they are only 2 mm square cross section.

 

Edited By John Baron on 02/06/2020 16:52:18

Thread: Belt Up
02/06/2020 16:01:35

Hi Guys,

If you think that the pulley is flat, lay a straight edge across it !

Thread: Removing nylon plug from carbon fibre tube
01/06/2020 14:05:32

Hi Sam,

You've got it about right ! Really sharp tools, about 350-400 rpm, maybe a bit less for that diameter and a nice steady feed. I usually go for about 6 thou per turn. If you do it by hand watch out for the tool biting in and dragging the saddle.

01/06/2020 06:57:07

Good Morning Sam,

Be careful machining plastics ! The plastics are quite abrasive and will cause the tool to get hot very quickly. The danger is that the hot tool no longer cuts but starts to melt the plastic. A flow of water based coolant helps tremendously.

I've used router bits many times to mill steel and brass. The problem with those is that because there is no rake on the cutting edge they shear the material off. This is fine for brasses and alloys, it works on steel but to get a good finish requires fine cuts. I've never cut plastic with one but I imagine you would need a fairly high speed and fine cuts.

Deralin/Acetal machines quite well when turned.

HTH.

Thread: Pratt Burnerd 4 jaw Chuck jaw alignment
31/05/2020 21:00:47

Opps, Sorry wrong thread !

Thread: Myford Lubrication... yet again!
31/05/2020 20:37:04
Posted by Maurice Taylor on 28/05/2020 19:55:38:

Why not make an end for your gun that fits nipple correctly.Put a small o ring in the end to seal it.

+1

That is what I've done for mine. However the oil also leaks out of the other end of the Myford oil gun. So I made a proper piston with an "O" ring ! It still weeps, but nowhere as badly.

In my opinion a poor design, and way too expensive !

Thread: Lathe work
31/05/2020 20:25:56

Hi Guys,

To close this thread.

In my case all four of the jaws all had different amounts of taper to the back. I've simply reground mine parallel.

However I've also recently discovered that PB deliberately grind the jaws with a 2 to 3 thou backwards taper. Apparently to allow for grinding tolerances in the guides.

Anyway having reground them I can now set the test bar true at the chuck and it is still true within two tenths of a mm 150 mm away. So I'm very happy with that.

If I need to grind the compensation for guide wear back in all I have to do is reverse the jaw, clamp it against the inside so that it can't move and regrind the jaw face with the chuck locked so that the jaws are parallel to the bed and lock the chuck so it cannot move.

26-05-2020-001.jpg

The general setup.

26-05-2020-006.jpg

Ready to start grinding.

Thread: Pratt Burnerd 4 jaw Chuck jaw alignment
31/05/2020 19:37:17
Posted by lfoggy on 20/10/2019 20:37:26:

I've recently acquired an 8 inch Pratt Burnerd 4 jaw independent chuck. It is stamped 'Made in England' and I think it was manufactured in the 80s. It seems to be unused or virtually unused as there are no marks on the chuck whatsoever and the D1-3 camlock fitting shows no signs of ever having been attached. The jaws have a perfect ground finish and are unmarked with no detectable play in their slots. When I fitted the chuck to my lathe to test trueness I found the chuck body to run true to <0.01 runout.both on the periphery and on the face. The clamping surface of the jaws however are not parallel. They are the opposite of 'bell- mouthed' as in the pic below. The taper is consistent on all four jaws. This may not matter too much for many applications but is definitely apparent when trying to grip a long and accurately machined workpiece.

What is the explanation for this? Were the jaws deliberately given a taper to accommodate wear or do I just have a badly made chuck? I am suspecting the latter.

I do reaslise that this taper would be easy to correct by the in situ grinding of the chuck jaws and I may well resort to this.

pic7.jpg

Hi Ifoggy,

I have recently had a similar issue ! But in my case the jaws all had different amounts of taper to the back. I've simply reground mine parallel. However I've also recently discovered that PB deliberately grind the jaws with a 2 to 3 thou backwards taper. Apparently to allow for grinding tolerances in the guides.

Thread: Removing nylon plug from carbon fibre tube
31/05/2020 19:26:48

Hi Sam,

Thank you for your reply.

I did wonder. Unfortunately I don't have any large diameter Deralin bar or I would have offered you some. Sanding varnish off something is a right royal pain, particularly when you can't get a sander on it. Anyway I'm interested in how you get on.

31/05/2020 17:56:29

Hi Sam,

Did you get the plug out ?

Thread: Belt Up
31/05/2020 17:04:41

Hi Martyn, Guys,

Tension will cause the belt to climb up the slope of the crown until its running centrally on top of the crown. Have a look at some of the old line shaft pulleys. The crowning was all that kept them on the pulley.

Thread: Surface Plate & Height Gauge recommendations
31/05/2020 16:17:37

Hi Lee, Guys,

When I wanted a height gauge I made one ! I used a digital vernier, one of the cheap Aldi one that they sell for about £8. A few bits of scrap, a couple of salvaged bearings from an old hard drive. More than accurate enough. My surface plate is a piece of broken granite headstone.

Here is a picture, I did a build log for this a couple or so years ago.

assembly-01.jpg

That brass knob drives the M6 leadscrew. A nice fine 1 mm per turn which you can actually measure on the readout.

assembly-03.jpg

A close up view.

More pictures in my album.

Thread: Parting tip breakage
30/05/2020 20:50:45

Posted by Tony Pratt 1 on 30/05/2020 20:33:46:

Why would you put such rubbish on you tube, oh hold on we aren't meant to criticise.

Tony

Hi Tony,

I agree with you !

If you were going to demonstrate parting off, you would at least attempt to do it properly !

Thread: Simple CAD App - Advice Please
30/05/2020 20:45:32

Hi Nick,

You could always use "Libre Office" and the drawing part.

Thread: Boxford AUD motor drive wheel plus reverse switch issue
30/05/2020 20:42:20

Hi Fergus, Guys,

Are you sure there is not a second grub screw under that one ?

Doubling securing screws is very common.

Thread: Parting tip breakage
30/05/2020 20:10:46

Hi Guys,

That video should be called "How not to part off" !

Thread: Thread cutting - Apron does not engage with the lead screw
28/05/2020 06:55:03

Does the leadscrew turn at all on its own when the chuck is turning ? If not have you got the tumbler gear lever in the down position ? The tumbler gear lever is the one on the left of the headstock.

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