Member postings for Ian P

Out of interest I dug out some of the cutters I have and measured the included angle of each cutter. All the proper ones are 20 degrees and the Chinese Ti coated one is 17 or 17.5 degrees. (largest one is 30mm)

All are a quite a way from the 1:2 taper Andy measured (so 28.03 degrees inclusive).

Jason's hand filed option is definitely the best suggestion, best too because it can be fine tuned with blue to get good contact withe the cotter.

Ian P

Step drilling will definitely make it easier for the conical cutter. I just looked at the RS one suggested and its probably too small for this job if hole at the small end is about 10mm. I have collected an assortment of cone cutters so have a range of sizes (up to about 40mm) most of them are of cheap eastern origin but work as well as genuine conecut ones do.

I'm quite happy to loan you one (where are you?) as I think its a relatively lot of work to make a D bit.

Unless I misunderstood Michaels approach, I dont think a joint in a milling machine column is a good idea from a rigidity point of view.

I think Emco intended the shoulder where the column changes diameter to be the feature that in combination with a close diametrical fit, holds the column dead square to the base casting when it is pulled down tight by the wedging action.

Ian P

I would go for the cone cut option to create the tapered hole in the column. Whilst they are intended to be used on sheet metal they do cut over the whole cutting edge so with care can be used to create the hole you need.

I would definitely do the cross drilling and tapered hole before reducing the column diameter. The 20mm spigot needs to be accurately on axis so hold the bar in a collet if it will pass through the headstock, or use a fixed steady with the 'top' end of the column set true in the 4 jaw.

Getting the position of the shoulder in the right place will be easier than putting the tapered hole in the right place if you turn the spigot first.

Ian P

I'm glad that Steve has solved his stuck adapter problem but there are two points I am not clear on.

What metal Is this 3 jaw chuck made from? I have a sneaking feeling its not the usual steel or cast iron.

Also I have not come across ANC threads, is that the same as UNC?

Ian P

I have another thought on this stuck adapter.

Looking at the picture of the chuck that Jason posted, it appears that the hole in the face of the chuck is larger than the 3/4" thread, therefore I would assume that the adapter (if the threads were not binding) would pass right through.

If that is the case then there is no need to waste time unscrewing the adapter, what it really needs is 'tightening' from the back.

I'm not sure which way Steve has been turning the slotted end but if a 3/8" nut and a small diameter washer or two were put on the adapter it could then be rotated clockwise (looking at the back of the chuck) with virtually unlimited torque using a spanner on the nut and the chuck jaws held by any method.

Or have I missed the bleedin obvious?

Ian P

What wrong with using a well fitting screwdriver?

Ian P

I did consider that the chuck thread might not run all the way through the chuck (it would be unusual though) but why the adapter would jam so tightly is a mystery. How tight it actually is something is depends on the person judging it and the method of applying the force. To anyone with a reasonable size vice on a strong bench, removing the adapter looks to be fairly easy, in Steve's case though he says he has a kitchen table workshop so just holding the vice and screwdriver in alignment whilst applying the turning force could be challenging.

Its not easy to see the state of the slot or the end of the screwdriver but neither look good. Not much can be done to improve the slot now that it is at the bottom of a recess, but the screwdriver looks quite rounded.

Unless the adapter to chuck thread has galled a good fitting screwdriver and some means of holding everything aligned should be all that is needed. I would think that the slot is potentially capable of imparting higher torque than anything gripping the short 3/8" thread.

Ian P

We know small objects can be surfaced by moving them around in figure of eight pattern on wet and dry carborundum paper stuck to a flat surface.

Maybe you could use the same idea with your anvil by turning it upside down on a concrete road surface and then with a rope around its waist, tow it for few miles

Ian P

Without wanting to take this thread off topic I am curious about the security of fastening a relatively large chuck to a rotary table by means of such a coarse small-ish diameter thread.

Quite rightly, on this and other forum there are frequent warnings about chucks becoming loose when a lathe is run in reverse. Surely the potential for a chuck held on a rotary table to come loose is (depending on the actual machining operation) is far greater.

The chuck in question looks to be ideal for attaching to a rotary table by clamps in the groove on perimeter of the chuck body, no worries then about it moving or stuck adapters.

Ian P

I would still like to know why a headless screw can jam in the parallel (through?) thread of the chuck.

Ian P

Thanks Michael, your link shows what that the adapter larger diameter thread fits the chuck body.

I now assume that the chuck thread has a shoulder or restriction (where the thread runs into the smaller tapping diameter) otherwise the adapter would pass right through the chuck body. If not what is it jammed against?

Ian P

I am not familiar with Sherline lathes but it seems odd that its mandrel has a 3/8" UNC internal thread rather than the conventional male thread and register for the chuck/faceplate etc.

In any event does the screw with a slotted head actually have a shoulder at some point or does it just like a large grub screw that converts the UNC to the chuck thread?

I know the above does not solve the problem, but AIUI (or dont understand it) what it the screw stuck against?

Ian P

I missed the rotary table mention. Still not sure if there are two different threads on the adapter thing

Edited By Ian P on 06/01/2020 21:07:15

I think a clue to the problem was the 'pronounced dish' in the blade.

It sounds as if the arbor is not clamping the blade properly. I have seen slitting saw blades that were eccentric but never come across one that is not flat.

Ian P

Paul Kemp's reply says it all!

Until Chris TT addresses Paul's points I think its pointless offering advice and prolonging the agony as it were.

There are reason and places where two particular materials are best not combined so there is nothing wrong with Chris asking the question so we can offer advice in the right context.

Ian P

I can see the connection, the spring is vaguely modeled on a colon

Ian P

It is with deep embarrassment that I have to admit I have wasted everybody's time on my caliper problem!

To cut a longer story short, it WAS the battery.

The calipers are ones that are somewhat better than the usual Aldi and Lidl offerings and came from a respected advertiser on this site. They use a 3 Volt Lithium cell which I think I have replaced once since I bought them. What fooled me was that the calipers with the usual 1.55 Volt LR44 type button cell, give warning of the battery state by the fact that the display becomes feint. The display and all operations on this caliper were completely normal until this weird 'not setting to zero' fault occurred, I did have a spare battery but never thought to try that first.

This pair of calipers are on my desk and have never been in the workshop so I knew it was not a damp problem. This evening I was going to dismantle them and check the board carefully under magnification but after taking out three of the four screws, paused and remembered the advice I was given here so tried the battery.

Surprisingly the 3Volt coin cell measured 1.64 Volts so I am amazed that it functioned as well as it did.

Thanks everyone.

Ian P

I think the site MG linked to is one where I learned some of the info about they work, I've just had quick look but not yet found anything relevant.

Dismantling and cleaning the calipers (which I have just done) has not changed them at all. I did see that that it has three solder-bridge jumper options (only No2 was linked) so now I'm curious and might experiment. (Maybe one of then disables the annoying auto-off feature)

Ian P

Purely out of curiosity, please could you re-phrase what you meant to say.

I assume it has something to do with heat shrink sleeving, but darned if I can see what

Ian P

One of the digital calipers I have which has worked perfectly for about 3 or 4 years will not zero now.

At switch-on the display does show 0.00 but it the zero button is pressed without moving anything it sets the display to -0.02

Its totally consistent and always -0.02 Oddly when the zero button is held down it shows 0.00 but goes to -0.02 when released.

I have reasonable understanding of electronics and how these Chinese calipers work but I cannot work out what could cause this fault. I'm pretty sure its not mechanical as its the same when its locked solid.

Ian P

PS I've not identified the supplier but wondered if anyone else has seen the same problem

Waste of time?

Obviously a big variation as to what people do with their machines and what type of work they are doing.

I find the very low speeds absolutely indispensable particularly for tapping. I regularly tap M2 and M2.5 without a tapping head, I tap up to M10-M12 also but if harder than aluminium finish off with a tap wrench or just the chuck key as a lever so adding (manual) power assistance.

Ian P