Member postings for John C

I will add my total satisfaction with A&R tooholders; I have several, and will probably buy more.......And the beauty is, they are almost the same price as the 'others'.

John

Edited By John Corden on 25/01/2015 19:41:51

Oh Neil! You have done it now. It won't be long before someone jumps on a hobby horse (wearing suitable PPE of course) and points out that hot swarf could ignite that cardboard breastplate and THERE ARE NO QUICK RELEASE FASTENERS TO JETTISON IT! Please modify your design forthwith.

John

Glad to hear it Maurice! I found using a ball bearing closing nut - obtainable from the usual suppliers on here - made tightening much easier.

Here is an example - make sure you get the correct size for your collets!

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners

John

Have you tightened them enough? The specified tightening load is quite high! There are tables on the internet. Is the 4 thou runout consistent at all distances from the collet nose?

John

John B

I will put myself forward as 'anyone', as over the years I have spent many enjoyable hours reading your posts, and learning from them. So please do make them available.

Best wishes,

(another) John

And there's the rub...

I have made parting tools from standard hacksaw blades. Grind off the teeth so you don't damage your holder. I put some top rake on, abut 7 degrees, and relieve the front. The blades are not stiff, so take it very easy!

John

Mac with Google Chrome works fine for me. The 'new 2014' Catalogue downloaded in about 5 secs.

I use the tapping drill sizes quoted by Tubal Cain in the Workshop Practice series book no 12: Drills, taps and Dies. I usually use 60% engagement. There are many threads debating how much engagement to use, but the consensus seems to be that 60% is plenty for most home shop uses.

John

Hex head delrin bolt, turn head down to fit press on knurled cap, attach with suitable adhesive?

John

Edited for fat fingers!

Edited By John Corden on 01/01/2015 16:55:51

I too have both types of collet. A point worth noting is that 5C collets will grip short lengths right at the nose of the collet, where ER collets need a fair bit of shank to grip. Makes each type have advantages!

Rgds,

John

I have found Emkay very helpful.

John

Well, I have just upgraded my MEW subscription to print and digital, and will renew both in 3 months. I like the direction the magazine is going and want (amongst other things) to be able to look at any articles originally associated with the excellent series of free plans.

John

Very kind of you to take the trouble to do this - PM sent,

John

Neil,

This is just the sort of thing that I originally subscribed to MEW for. Thanks for publishing the article on line, and rest assured that there is interest in this sort of thing.

I remember that JS did a write-up of a lever action tailstock mod.  A quick search for 'Tailstock' on this forum turned up several articles related to tailstock mods - all interesting and worth a read, but no JS submission. Perhaps you could coerce him ( with the promise of £2) to reproduce his articles here too?

John

Edited By John Corden on 21/08/2014 18:25:04

Edited By John Corden on 21/08/2014 18:31:35

My pleasure Rod - it exercised the old grey matter a bit!

John

Keith - yes, it is an extreme case - but it was to show that there is an error. Your results may differ....

John

I think that this is a case where everyone can be right about the effect of measurement height on the taper - it depends on the accuracy you require.

To put it into perspective here are some numbers and the justification:

R is the radius of the taper at the chosen section.

h is the vertical error in positioning the measuring device.

d is the horizontal error caused by h.

A is the angle between sides R and R-d.

h will remain constant for all measurements.

What we want is d, the difference caused by h

R sin A = h

Sin A = h/R

A = Inv Sin h/R

R cos A = R-d

(R cos A) - R = R-d-R

d = R - (R cos A)

So to put some numbers in, for a sharp taper and large height error:

R = 10mm

h = 5 mm

A = inv sin 0.5 = 30 deg

d = 10 - (10 cos 30)

d = 1.339 mm

Now at the larger end of the taper

R = 20 mm

h still = 5 mm

A = 14.47 deg

d now = 0.635mm

So there is a radius difference of 0.704 mm, or 1.4 mm on the diameter.

This is just to show that an error will occur.

Now for MT2.

Small dia = 15.3 mm R = 7.65mm

Say h = 1mm

A = inv sin 1/7.65 = 7.51 deg

d= 0.065mm

Large dia = 17.7mm R = 8.85mm

A = 6.488 deg

d = 0.0566mm

Difference = 0.0083 mm on radius, or 0.016mm on diameter

That’s 6 tenths of a thou!

So measurement height does make a difference - whether it is significant depends on what you are doing!

Steve - I happened to have a set of 4c collets!! I have a 5c chuck and collet set which I use far more than the 4c. M

Making the headstock bush was more of an exercise really.

John

Edited By John Corden on 01/08/2014 14:12:11

The STS 10 - 20 headstock taper is a unique Boxford one! You can get an adapter to take 3MT but sit down before you check the price! I did make my own adapter to take 4c Collets with a drawbar.

John