Member postings for Chris Heapy

I tried to make a video of this center finder in operation (although I really needed 3 hands to do it so it's a bit wobbly!). The video starts with the workpiece already aligned as best I could - less than one division movement, the workpiece is just a scrap piece of aluminium with a counterbore machined into it.

Then I move the piece 0.001" on the handwheel dial to observe the difference on the indicator dial, and attempt to move it back again (difficult with the backlash in the handwheel - and whilst trying to film the whole thing at the same time). Anyway it was obvious that 0.001" movement causes a significant change in the deflection of the needle. I think. Sorry about the crap commentary but my voice always sounds terrible on vids like this.

Edited By Chris Heapy on 12/06/2013 14:12:50

I bought a new drill chuck the other day - also from Rotagrip - but what arrived wasn't quite what I expected. I wanted a larger capacity (16mm/5/8" ) keyless chuck but with integrated R8 shank so that it sits as close to the end of the spindle as possible. I had ordered the Vertex version but when it arrived there was no upper knurled ring - just the chuck body and the shank. So I installed it and was scratching my head as to how the heck you were supposed to hold it to tighten/loosen it with no spindle lock on the mill? Even if there WAS a spindle lock it would be a PITA to have to operate it every time you want to insert a drill. So I phoned Ian up and he quickly sent a replacement - this time an Albrecht 5/8" chuck. I must admit it looks to be superior quality and importantly has the upper knurled ring you can hold when loosening and tightening it. I never realised some chucks were made like that so something to watch out for.

Chris

Edited By Chris Heapy on 12/06/2013 12:56:44

I made one for my mill, used a Chicken-Head knob for direction (green forward, red reverse), and a numbered skirt on the pot for speed. However I find I never use the numbered skirt but simply judge speed by eye and ear.

I guess you could use a multi-turn pot if you wanted more precise control.

Edited By Chris Heapy on 12/06/2013 11:40:47

There doesn't seem to be much that Ian @rotagrip doesn't know about lathe chucks. Very helpful fellow.

Chris

Do you want one? I'm sure I have some nice collet knobs in a draw. Any colour you like so long as it's black

Edit: Actually, I found some brown ones too - and either yellow or black pointers The flash photo has done them no favours, their condition is pretty good.

Edited By Chris Heapy on 11/06/2013 21:13:28

Years of dismantling scrap electrical devices lifted from skips means I never have to buy that sort of thing - mind, all that stuff takes room to store and index (and most will likely never be used for anything).

I meant to mention the logic behind using a 2MT test bar to 'tune' the chuck alignment (mentioned earlier). As it turned out the process was not necessary with the TOS 6-jaw because the chuck proved to be very accurate straight off, in fact - about as good as you can reasonably expect from any scroll chuck. Certainly better than the 'reasonably priced' (to quote Top Gear) ER32 collet chuck set I have anyway.

Chucks are assembled from pre-machined parts and I'm not certain how much work is done after assembly to correct for possible errors. Perhaps the more expensive chucks are tweaked (like Pratt-Burnerd 'super accuracy' versions) and will be tested to ensure they fall within defined accuracy parameters but remember, chuck jaws are available as spares and are expected to fit right in and produce the same accuracy as the originals (just as the inside jaw set are expected to provide the same accuracy as the outside set), so there isn't much that will be done on an idividual basis post-assembly. On cheaper chucks it's a certainty you'll get whatever accuracy is present post-assembly, there simply isn't the production profit available with inexpensive chucks to pay for that kind of QC. I didn't know how good a TOS chuck would turn out to be - I was assuming 'middle-road' - but I discovered later TOS actually make Pratt-Burnerd chucks

Anyway, the idea with the test bar was to correct for any axial misalignment rather than run-out (the latter can be compensated for when mating to the backplate, and this should be carried out first in any case). The procedure depends on your lathe being perfectly setup and aligned (headstock spindle parallel to lathe bed, tailstock aligned to headstock) - you'll be wasting your time if that is not the case. Ideally, the 2MT test bar needs to be able to pass through the center of the chuck and be supported at the tailstock end with a live or superior quality rotating center. The bar is inserted into the spindle, the new chuck (without backplate) is mounted facing the spindle close to it, and the jaws tightened onto the bar, whilst the tailstock is brought up to support the other end. In this position a skim can be taken across the mating surface at the rear of the chuck body - the thinnest necessary to face it off cleanly - then it can be removed and re-assembled.

Doing this ensures that when a workpiece is gripped by the jaws it now lies exactly parallel with spindle (and lathe bed) and corrects for any potential inaccuracy within the chuck body/jaw assembly. Testing run-out on round work should now not rapidly deteriorate with distance from the chuck jaws and will be as good as possible with this type of chuck.

Well those were my thoughts (FWIW )

Chris

PS., I didn't mention I bought the chuck from Rotagrip Online who were a good company to deal with.

Edited By Chris Heapy on 11/06/2013 19:26:43

Yes Oak contains a lot of Tannic acid (Oak Apples being an excellent source and an extract was used in the past for tanning leather). That is the reason you should not use steel screws in oak. I use Pine with a few coatings of acrylic varnish to seal it (mainly to stop it warping). My single garage doesn't have a constant heat source so in winter it can get very cold in there, although condensation has not been a serious problem over the years.

Chris

Agreed Steve, hanging high on a wall is not the best idea ever but limited space restricts my options. However a bit of 'risk management' and realisation as to what could happen if mistakes are made ensures accident avoidence If you're an accident-prone sort of person best stay out of the workshop!

I do use an ordinary domestic vacuum cleaner, an old Electrolux that was replaced for use in the house. I didn't expect it to last but it has performed well for 10 years sucking up swarf from the the lathe and mill (and workshop floor generally). It wasn't made for the job for sure but I thought I may as well use it until it expired. You can buy industrial cleaners designed for the job of course but they are expensive. It uses replaceable paper bags which is a better idea because the bags sometimes get saturated in cutting oil.

Bob: I haven't seen any rust in my workshop and some of those chucks have been there for 30 years, so I figure it isn't a serious issue to be concerned about. Added to which, I now use (in the last 5 years or so) a product called ACF50 and a wipe over with a rag impregnated with that and you could spray them with saltwater and they won't rust.

You raise a couple of fair points Stephen, but I don't think it is the actual storage method used that is of concern - materials like alloy/wood/Delrin are not going to damage the register even if it does rest on it. Swarf and muck will work its way into the scrolls mainly whilst in use on the lathe machining stuff (and opening and closing the jaws drags it into the scroll), but not when it is sitting in a rack in storage. Personally, I always clean my chucks after use with a vacuum hose which removes any loose material, and wipe out the register with a rag before it's mounted onto the lathe. Maybe once a year I will strip and clean the chucks depending on the amount of use each has.

However that raises another point - lubricating chucks. I note even Pratt-Burnerd specify a ceramic grease for their chucks, but I wouldn't put any sort grease on a lathe chuck. Grease attracts and holds particles of swarf so it won't fall out and you can't suck it out either so a full strip down is needed to clean it. Machining cast iron would be quite destructive with a grease-filled chuck. I use a light oil instead (and only just enough to do the job). Yes, it tends to spray out when the chuck is turning at high speed but that is a minor irritation.

Chris

Edited By Chris Heapy on 11/06/2013 00:39:50

The best rust inhibitor I've used is a product called ACF50 - a bit like WD40 on steroids. It is an oily coating but posses a strong resistance to wiping off (unlike simple oil), and it also actively creeps into crevices and even neutralises existing corrosion. Only a very thin smear of of this stuff is required for effective and lasting protection - the parts are not left dripping in the stuff.

Chris

Originally I used wood dowels knocked into 4x3" timber to hold my chucks but upon inspection I found one had split meaning there was a risk of it breaking and falling off. Not good. So I removed all the wood dowels (with the exception of the one for a small 4" 4-jaw which weighs little) and replaced them with Delrin rods screwed into alloy flanges. The other advantage of doing this was each mount could be re-positioned if required as my collection of chucks changed. The Delrin rods are screwed into the flanges with an nice fat thread (0.75" x 18tpi) so no chance of them working loose or falling off

I found a couple lengths of Stubbs silver steel 40mm diameter so tried one of those. TIR was about 0.08mm 12 inches from jaws.

(5) Use an ER collet chuck instead of the 3-jaw

I fitted the backplate and tested the chuck this afternoon. Maybe I was just lucky but there is negligable run-out near the chuck jaws and about 0.06mm TIR about 4 inches out. I don't know that I could make any improvements on that so I'll just use it for a while and check again.

Another attempt at a video

Edited By Chris Heapy on 07/06/2013 17:24:15

There are so many fine and absorbing projects waiting for you it can be very difficult to choose, particularly as each represents a significant investment in time and effort - so you want some reward at the end of it (and some guarantee of success). Another factor, if you're new there are a lot of techniques to learn, and it really helps on your first project if you have a step-by-step build sequence to follow. Once that first project is under your belt you can move on with your newly aquired knowledge.

For the reasons above I would suggest looking at various books on constructing specific models, many old favourites exist (Tich, Juliet, Rob Roy locos, Minnie traction engine, some stationary engines) which offer both worthwhile experience and produce a great model. The books would be worth buying just for the information they contain and perhaps reading them one will inspire you to make a decision on your project.

Chris

Jim - great idea, I hadn't thought of that one

Ian, the reference point(s) were the first step not the tips of the jaws, those must surely be concentric otherwise these outside jaws couldn't work at all.

Chris

The closest I got was to use a small copper coin placed against the first tooth of the jaws (i.e., not the gripping surface but just beyond it) and lightly tighten the jaws onto that. This configuration leaves the whole length free for grinding. Unfortunately, although it tensions the jaws correctly, with it being right at the back of the jaws it also causes the jaws to take up all clearances in one direction only - an unnatural bias, and if the slots are slightly worn you still end up with a slight bell-mouth.

Chris