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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: Wall Chart
24/07/2021 17:16:13

Hi Derek,

Cromwells do a free on request A3 size one on a paper backing,

Worth a phone call !

Thread: Old lathe tools
22/07/2021 08:02:19

Hi Dan, Guys,

I would pinch the knurls from the push knurling tool and make a pinch or scissor type tool to use them on. The knurls on those are usually good quality ones !

Thread: Setting up rear parting tool properly
22/07/2021 07:57:16

Hi Guys,

This is a picture of my "Norman" patent rear tool holder with a 12mm X 2mm blade in a holder. It is horizontal and set exactly at centre height. The tool holder can be used on the front tool post as well.

31-07-2019x002.jpg

Thread: 12 volt motor speed controller
19/07/2021 20:15:50

Hi John, Guys,

When I built my window screen wiper motor driven mill table drive, I used a variable voltage lab type power supply. Mine supplies 30 volts at 3 amps. I just use the whole 30 volts for fast traverse and around 7 volts for actual milling.

My direction control is via a tumbler gear very similar to the one found on a Myford lathe, giving me forward/stop/ and reverse directions.

mill-table-drive.jpg

This is a picture of mine mounted on the left hand side of the table. I just pull the white knob out and lift or lower the lever to select the direction or neutral. It also has the advantage that I can still use the handwheel at the other end when neutral is selected.

All the gears were salvaged from printers. photocopiers and the like. The motor unit is a "Trico" one salvaged from the local scrapyard.

Thread: Taps and Dies
14/07/2021 13:48:27
Posted by Michael Gilligan on 14/07/2021 06:17:06:

Thanks for that, John Baron

All looks good yes

Have you bought any screw pitch gauges from them ?

… I feel the urge to treat myself to a set.

**LINK**

MichaelG.

Edited By Michael Gilligan on 14/07/2021 06:31:39

Hi Michael,

Yes I bought a metric set from them quite some time ago ! Good quality, but I didn't pay today's price, in fact if I remember correctly only about £4.00 + vat, vat was only 15% then.

14/07/2021 04:59:29

I've started to buy my taps and dies from

www.avontapdie.co.uk

Good quality HSS UK made.

No relationship just a happy customer.

Thread: Can't get the hang of HSS!
13/07/2021 16:31:02

The tool on the right is too sharp and pointed for brass.

I would use a round nose, maybe 1/2 mm radius with zero rake on the top and left side and about 10 degrees on the front.

I do agree that in the second picture it looks like a very fine thread !

Thread: Tool post height
12/07/2021 15:46:25

Hi Guys,

I agree with the comments that Tangential lathe tools are quite easy to male and use. I made one quite a while ago.

Easy to set up and easy to sharpen. You get a good finish too.

This is a drawing of one that I made. Just scale to suit whatever HSS or carbide you want to use.

tangentel tool.jpg

09-06-2020-014.jpg

09-06-2020-015.jpg

09-06-2020-017.jpg

As you can see the finish is not too bad.

09-06-2020-016.jpg

Certainly better than my photography smile

Thread: Power feeds for Chinese mills
12/07/2021 15:25:49
Posted by duncan webster on 12/07/2021 11:42:34:

Many moons ago I made a drive for the Naerok miller using a DC motor and a train of gears. This had two disadvantages:

  1. When the cut started and more load went on the motor it all slowed down, by quite a lot, in fact if set for a very slow feed it would just stop.. I can wax lyrical about why, but not here
  2. you had to disconnect the drive to do manual feed.

I overcame the first by incorporating a feedback loop. I suspect people using windscreen wiper motors just have a lot of oomph to spare so it doesn't slow down as much.

The setup on my Centec uses a stepper with tooth belt drive. It is so much easier. If you use one of the pulse generator things referred to above it is just buy some bits, make up a mounting bracket, join the bits together and go. No need for a clutch, just wind the motor round. No need to know anything technical about steppers or controllers. Mine is a bit cleverer as it incorporates acceleration ramps

Hi Duncan,

I made mine using a car window screen wiper motor. They just don't stop, at all ! They are amazingly powerful.

I actually twisted the centre out of the primary gear on mine by forgetting that I had locked the table. Fortunately I had a spare gear.

I drive mine from a 3 amp 30 volt variable voltage power supply. Usually at about 7 volts. But I have put the full 30 volts on the motor several times for rapid feed without any issue.

Thread: Tool post height
08/07/2021 20:35:29

Hi Guys,

Just in case there are those that don't know what the "Norman" patent tool post looks like. This is the one that I made and use. The tool slot will hold a 1/2" inch tool and the height is adjusted by altering the silver M6 cap screw that bears on the surface below. The tool holder is secured by a spilt cotter using an M6 thread. It takes about a quarter of a turn on the cotter screw to go from locked to loose.

25-09-2018-006.jpg

Drawings for the Myford size one are in my album !

08/07/2021 15:17:34
Posted by Tony Pratt 1 on 08/07/2021 13:54:10:
Posted by Roderick Jenkins on 08/07/2021 13:50:14:

Lots of "theory" on here about the lack of rigidity of QCTPs. I have never had a problem with mine on my S7. I have a Gibraltar post and have only ever used that with a boring bar that is too big for the tool holder (and for my J&S knurling tool which has a shank which is too big).

Rod

I agree, if you tighten a QCTP correctly there should be no problem with lack of rigidity.

Tony

Its nothing to do with how much you tighten a QCTP ! The problem is with the amount of overhang some have. The tool needs to be within the footprint of the cross slide for maximum rigidity.

07/07/2021 20:02:44

Hi Guys,

I'm not an advocate for QCTP at all having used one and got rid of it in favour of the "Norman" patent tool post and holder. I can use 1/2" inch tools without a problem ! I don't need shims and can set tool height in a fraction of the time it takes to set a new tool using a QCTP. Particularly since I predominantly use HSS tools.

Myford also used the "Norman" patent tool post in the earlier days as did RR in their workshops. I've still got the original Myford four way but its in a box and not used any more.

I do agree about the loss of rigidity with a QCTP particularly the extra overhang that it has.

Thread: Split cotters
04/07/2021 09:47:47
Posted by Howard Lewis on 04/07/2021 08:43:34:

John Baron,

That was exactly the point that i was making, that when clamped to the bar angular and linear movement is prevented. The whole purpose for using split cotters, surely?

Howard

Yes I agree ! I misread your post then couldn't edit mine. I do apologise.

03/07/2021 18:09:17
Posted by Howard Lewis on 03/07/2021 17:32:27:

From a practical standpoint, split cotters would seem to prevent movement of the main bar, in two ways.

1 ) The two halves of the split cotter grip the bar like brake shoes, and being a close fit in their bore prevent rotary or linear movement of the bar.

2 ) By clamping against the bar, and having a gap between the ends, there would be a wedging action which exerts a force between the one side of the collets and their bore, forcing the bar outwards against the bore in which it is located. The frictional forces resulting will tend to prevent the bar from angular or linear movement.

If either of these hypotheses is correct, the split cotter does what is required of it, in preventing movement in any plane, once clearances have been taken up.

If anyone is so inclined, reference to the dimensions of a particular arrangement can allow the forces to be calculated, having made assumptions about the coefficients of friction of the materials and threads involved.

Howard

No it doesn't prevent rotary motion, nor linear motion until the two halves are pulled together. As long as there is a few thou of gap between the halves when tightened they will firmly clamp whatever they are pressed against.

As far as a diameter for the cotter is concerned a larger area for the clamping surface simply means that the force required to lock a shaft is less than a small area.

16-09-2018-015.jpg

This is 14 mm diameter cotter intended to secure the block to a 35 mm diameter post using an M6 screw. That gap is just under 2 mm.

26/06/2021 08:14:36

Good Morning Guys,

I understand both points of view !

Only if one side of the cotter is longer than the other could there be any possibility of wedging, this could happen if the cotter were cut off centre or the cotter was a very loose fit.

Since a cut in the centre of the cotter would remove material and make both halves shorter by equal amounts the very fine taper on each would be removed.

Any burr on the cut edges will dig into the shaft being clamped and cause sticking and shaft damage so it must be removed.

I agree that the cotter provides a linear clamping action rather than a wedging one ! However as shown in the diagram that Michael posted the red arrows showing the force direction that will be directed at the back of the bore that the cotter slides in.

25/06/2021 16:53:54
Posted by John Baron on 25/06/2021 15:19:08:

Hi Guys,

Michael is right, facing off the inside ends would only tend to reduce or remove the burrs that the saw or parting blade left. FWIW I just use the bandsaw to cut the cotter across its centre. This usually leaves a 30 thou gap in the middle. Occasionally I face the inner ends if the cut is a bit rough.

? How about considering a split cotter clamping a square cross section !

Quite right, my error !

Since it wont let me edit my original post, error corrected.

I do understand where you are going Martin, but the cotter wont work if there is no gap between the halves. So the risk of any locking is non existent. As far a CAD package is concerned, I use Qcad. The community edition is free but a perpetual licence is only £30.

Thread: dirty clutch trick
25/06/2021 15:27:37

Hi Brian, Guys,

I've not heard any horror stories about Myford clutches, but slipping a belt is a useful trick ! I deliberately run mine a little loose.

Thread: Split cotters
25/06/2021 15:19:08

Hi Guys,

Michael is right, facing off the inside ends would only tend to reduce or remove the burrs that the saw or parting blade left. FWIW I just use the bandsaw to cut the collet across its centre. This usually leaves a 30 thou gap in the middle. Occasionally I face the inner ends if the cut is a bit rough.

? How about considering a split collet clamping a square cross section !

25/06/2021 11:04:36

Hi Guys,

The clamping angle varies very little for a given collet diameter and ultimately depends upon the diameter of the clamped part.

split cotter.jpg

This drawing of a 12 mm cotter with an M6 clamping screw shows the angles for a 20 mm diameter and a 50 mm diameter shaft. The blue lines representing the collet, whilst the red lines the diameter of the clamped item. There is barely 7 degrees between them. A larger collet diameter will only make a small difference. Hardly a locking taper.

As I mentioned earlier the sharp edge on the scallop edge will cause binding and should be removed. I few swipes with a stone is enough.

24/06/2021 16:31:23
Posted by derek hall 1 on 24/06/2021 14:55:19:

Hi everyone, thanks for your input !

In the Hemingways instruction in building the Quorn the offset is given by:-

D = bore being clamped, d = the diameter of the clamping bolt that squeezes the two collets together (NOT the diameter of the collets as I presumed it to be)

D/2 + d/2 + 0.02" = the centre to centre dimension for the split collet and bore.

Now I checked this with the GHT articles on his kit and his offset is 0.01" larger than suggested by Hemingway, that is:

GHT method is:- D/2 + d/2 + 0.03 = the centre to centre dimension of the clamping bolt and bore.

So both methods seems to suggest that an offset anywhere between 0.02" and 0.03" is the optimum

Without boring you too much more, GHT does say that "while the clamping effect is very powerful, the 2 halves of the collet may not separate when the clamping pressure is removed. This is down to one or both of these reasons (a) the offset between the bore and the clamping bolt is too large and (b) the shortening of the back of one of the collets was insufficient".

In addition GHT mentions that this offset is important and is recommended that it is held to within 15 thou (0.015"

Well I have lots of these to do on my Quorn so I feel confident that this offset works without stuffing up any castings!

Kind regards

Derek

Hi Derek, Guys,

Whilst the formula are basically correct I just add a couple of MM to the clamp screw diameter. However one thing that you do need to be aware of in cast iron. Split collets exert a great deal of pressure and whilst very effective at clamping that pressure has to be contained. So take very great care that the wall thickness directly opposite to the split collet is adequate to contain the pressure.

In Steel it isn't a problem, but I've seen castings broken by excessive tightening of a spilt collet ! One way round this is to use a small/smaller diameter material for the collet. Virtually all mine are in steel, I've only one in cast iron and one in aluminium.

HTH.

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