Member postings for Macolm

On checking, the Camlock taper is in fact 1 in 8 on the radius, so 1 in 4 on the diameter.

It occurs to me that, provided the gap when the cams are correctly done up is indeed only 2 thou (0.05mm), then only a bit more than half at thou would need to be removed from the taper diameter. I think this would be within the scope of lapping, and suggest a tool roughly as below to carry probably wet and dry paper, which is thin and uniform. This would need to be cut as an arc so as to fit the conical surface. It could be retained in place with pegs in slotted holes as shown.

This would sidestep the near impossibility (except in a tool room) to get the taper true enough to the precision necessary for grinding. It would not maintain the exactness of the original machining of the taper, but this could only be wrong by less than the amount removed. The taper provides a location, the faces in contact ensure the axis is correct.

I only suggested paper as a one off check to see if getting the faces parallel fixes the problem. Then it would need the correct thickness of steel shim as a working fix. Unfortunately, thin shim stock is not at all robust, and in my experience, bonding thin items does not have a good long term success rate unless additionally protected. Hence the suggestion for a way to provide that. I suspect the shim would indeed need to be bonded as well to prevent ingress of swarf.

I think the Camlock taper is 7 in 24, so a 0.04mm shim would change the diametric fit by only 0.01mm! The configuration is extremely rigid with neither part likely to flex on the diameter.

I suggest you verify things simply, with ordinary copier paper which is about 0.1mm for 80gm weight. Other weights of paper are roughly pro rata thickness. If that fixes the run out then it is worth making a proper shim.

The back (Camlock) face of my PB chuck is flat right across, so a shim made with a larger outside diameter could be held in place with a ring of thicker material fastened with small screws tapped into the back plate. The holes for the screws could go right through, provided the screws do not project inside. Obviously the ring ID needs to clear the spindle OD. This scheme would be easy to do, and give good protection, even if the shim was also bonded.

This diagram is a very quick concept and not correct in detail.

Edited By Macolm on 22/11/2022 22:12:06

This Camlock problem would seem to be separate from the issue of the stiff jaws.

A correctly sized Camloc interface certainly works very well for accurate concentricity. The configuration uses a taper for location in combination with face to face contact. The taper interface is really just a location press fit, but with the benefit that disengagement occurs over a very short travel. Unfortunately, the taper makes measurement extremely difficult, the total difference in diameters between free and press fit being probably about a thou. The manufacturer presumably has precision go-nogo gauges.

I faced the easily tackled defect that the taper was not tight when the faces were in contact. The opposite defect would need metal removed from the taper, quite a different matter. I think the suggestion by Hopper to try a shim is good. A quick way is to use paper, as thin as possible. This may still be too thick for the taper to grab, but if the result is good concentricity then the problem is identified.

Another approach may be to remove the Camlock pins, and explore the “feel” as the two parts are brought together.

It is a bit confusing, but the numbering of the various sizes of this series of toolposts all start 250-. The 250-0xx is the smallest, the next is 250-1xx or AXA, then 250-2xx or BXA etc. The dimensions of the 250-000 toolpost can be found on the Arceurotrade website which also indicates suitability for mini lathes.

Do ensure you get a wedge design rather than piston type because the positioning of the cutting edge is much more consistent when removed and replaced. An advantage of the 250- design is that it is fairly simple to make your own toolholders.

Buying from a UK vendor usually means that someone has vetted the supplier to provide reasonable quality.

Edited By Macolm on 14/11/2022 21:14:17

Edited By Macolm on 14/11/2022 21:17:07

Edited By Macolm on 14/11/2022 21:17:31

My similar PB chuck has the camlock features integral with the back plate.

I believe (without any actual maker’s information) that with a Camlock interface, the taper and the face should be in hard contact when done up. You can check that a fine feeler or cigarette paper is nipped by lightly tightening the cams. However, I did once need to lap a new faceplate by about 0.03mm to achieve this. The aim is that after undoing the three fully tightened cams, you should be able to dislodge it from the spindle by a light blow from your fist. This ensures that it gives very repeatable fitting.

I would still suspect that the chuck has been dropped on to a jaw, and the front face bent in slightly. This would cause the run out observed. Check with a good straight edge for a slight depression. Since the affected jaws would be moving over a very slight curve, the run out pattern would presumably vary as a function of the diameter of bar being held. The same pattern could also result from warping of the casting.

That’s what comes from scanning the thread to see what has been suggested rather than careful re-reading of the original post. That narrows the possibilities, the most likely being that the casting escaped proper seasoning and subsequently warped, or that the chuck has been dropped.

I have a very similar PB chuck, and looking at it you would be very unlucky to distort it without other evidence. However, if the inside jaws were quite far out, or the outside jaws nearly in, it does look possible to bend the track about half way along with enough force. It would need to be dropped a long way, and onto a wooden floor for there to be no marks.

I suggest checking the front face for distortion (with the jaws removed). This is easier said than done, but a good straight edge and a light may show something up. It would only need to be a couple of thou.

Edited By Macolm on 04/11/2022 15:54:28

If it is as tight as that, you should be able to see the tight spots. Wipe off all oil on the jaws and slots, then look for polished patches, though could also be a torn surface. As both inside and outside sets stick, this looks like the chuck body is distorted, but try the jaws in the "wrong" slots and note what is free and what sticks. Does the tightness reduce if you slightly slacken the back plate to allow the scroll a few thou extra back and forth clearance? Also check the D1-3 pin threads do not project through so as to rub on the scroll. Beware of removing metal other than the tight spots. It is easy to end up with too much slack.

The tapered gibs are probably similar to my mill/drill. One had about a millimetre backlash between the gib and adjuster, and surprisingly this was enough to nearly lock the table in one direction when it was correctly adjusted for the other. I fixed this with a washer that took this out the slack. Thereafter, if you are left with any tight spots, the gib can be filed, assuming you can work out where. Use a good single cut file to retain adequate surface finish. It does not need much removed.

Andy-G is quite right, 1mm stainless sheet is about the limit of the technique I described, and it will need more than chipboard or MDF. The two pieces of steel sound OK, and a layer of masking tape usually protects against marking. Remember stiffness is a cube law, 0.5mm should be 8 times easier to bend than 1mm! As he says, a hard hardwood piece (eg beech, oak) to make the corner of the bend is indicated, Mahoganoid will be no better than softwood.

If the bend angle is made too great, place the corner edge on a flat (expendable) piece of wood, put a bar 10mm or 15mm diameter inside the corner, and hammer it via a another wood board to “draw" the angle (this will spoil the bar for precision purposes).

On grooving the bend line, this will certainly concentrate the bending. Best would be to mill it with a ball nose cutter, avoid a very narrow groove which may result in cracking. Unless you can keep an angle grinder very straight, the wavering will show on the other side when bent.

Or perhaps start with 0.5mm stainless sheet.

I sometimes need to do this sort of thing, without cosmetic damage. What works well is to hold the sheet in the vice between pieces of wood or better, faced kitchen type chipboard. This usually needs to be cut specially to fit. Align the chipboard edges and the fold line. The chipboard is potentially sacrificial.

Now press a third bit of chipboard so as to produce the bend. However, this will make a curve not a fold, so using a mallet, hammer the chipboard as near the fold line as possible. You can form a good but not fully sharp fold this way, without marking the metal.

Sorry drawing is a bit big!

Edited By Macolm on 27/10/2022 22:11:32

Not quite relevant to the present requirement, but many years ago we used a chemical disintegrant for cured epoxy resin. It was Ardrox branded, and various products are still available. I recall that it had a protective liquid floating on top, and the article was hung by a wire through into the active fluid. No doubt something as useful will long since be banned!

Try link again.

**LINK**

While predictable, tidal energy is anything but continuous, and worse, a large variation between spring and neap tides. The good news is that the installation laste a long time, so that eventually the high costs are recovered. The French La Rance facility is about 250MW max and 60MW average, so you would need quite a lot of similar projects to make much difference.

**LINK**

What I have done to remove metal outer oil seals is to carefully drill a small hole about 1mm or 1.5mm diameter through the flange part, then screw in a very small self tapper or perhaps a wood screw. Then use a tack lifter etc to pull it out. If awkward, it may need two screws diametrically opposite.

See

**LINK**

UK electricity prices are made considerably worse by the concocted “market”. This was designed when there was surplus fossil fuel capacity and to give renewables an advantage. Now that dispatchable capacity only just covers demand, the market has become unstable. See the graphs extracted from National Grid. Some of the time generators are prepared to supply at 26p per unit, but it spikes to 74p per unit for no obvious cause.

Edited By Macolm on 23/08/2022 21:32:10

To trip a simple RCD (one that does not include overload protection), it needs something to contact the frame (which is earth connected). The symptoms described suggest a spurious contact at or near that end of the start winding that connects to live at forward, and to neutral at reverse. This could indeed be a fault in the switch, but equally could be a chafed wire touching frame, and so on.

I would suggest you try to find the fault before simply disturbing everything to change the switch. It is all too easy to temporally dislodge the fault only for it to return a month or three later.

I am not sure I have picked up the spindle design details. If the quill extends and it has a vertical slot for a morse ejection wedge, then there might still be hope to eject it that way. In this situation where things have been over tightened, poor tooling is very unlikely to succeed, it must be as solid as feasible..

Plan A. Suppose the drawbar thread is M10, and the drawbar hole is 13mm diameter. Get an M10 cap screw, turn down the head to go inside 13mm, remove the drawbar, attach a hex bit to something long, eg some plastic tubing, and manipulate the cap screw down the spindle and screw into the morse arbour so that the head makes solid contact. It need not be tightened, though that might improve chances.

Now use a proper morse wedge to attempt release. The real article is correctly heat treated, and the top edge fits the slot radius. File tangs are dangerous and much less effective! Try smearing the ejection wedge with moly grease to minimise friction. You may still need to hit the wedge pretty hard.

Plan B. Turn up a T piece from 0.250 thick steel (for MT2 slot) that slides inside the arbour thread at one end, and the top of the T about 0.560 in wide and similar in height to the non existent tang. Poke this into the ejection slot and manipulate down into position, then try to eject as in Plan A.

Edited By Macolm on 21/08/2022 19:01:18

If a lathe is available, I suggest making an aluminium or brass sleeve to be clamped up with the collet nut as before. It needs to be good and solid, and the nut tightened once again as hard as possible. If it only catches on the spindle by a little, make a steel support spacer and split it with a saw so that it can be fitted to support the sleeve, and both clamped.

Now run the spindle slowly, and heat the sleeve with preferably two blow torches to something like 250C. It needs to be as quick as possible so that only the sleeve gets hot. This should produce expansion of 20 parts per million times 200C – about 4 thou per inch. A medium thump on the drawbar at the same time is worth a try.