Here is a list of all the postings Dave S has made in our forums. Click on a thread name to jump to the thread.
|Thread: Optimising the Life of Cut-Off Wheels|
There is little difference between a surface grinder wheel and a bench stone.
Think of abrasives as tiny cutting tools, taking a very small DOC on multiple teeth. (Somewhat true)
At that point you can see that to remove much material you have to make a lot of cuts - and to do that in a reasonable time your speed has to increase. Hence the general use of 'high' spindle speeds.
|Thread: Small saw. Proxxon or something else|
My surface grinder is supposed to run 71/2” wheels iirc, so I didn’t look at that.
Homebrew cutter grinder:
Has a 4” cup in it currently, also runs a 4” saucer.
Also just under 3000 rpm.
I have never needed to run a slitting disk on either, but I don’t doubt that with a thin wheel at that speed both would still work. Of course it would need to be the right wheel. Abrasive wheels are cutting tools, and much like different types of carbide or HSS there are different types of wheel. A wheel designed to run at 10000 rpm is built differently to one with a slower maximum speed.
I do wonder if John S is trolling or just indecisive.
Seems to me if you had a small mill, somewhat like a sherline 5000, where the head can be set over at an angle then you could just use a slitting saw on an arbor.
As a bonus that machine could also do all sorts of milling things, and probably make precision V blocks with 90 degree included angles as well
|Thread: Precision V-blocks (32mm & 7") - any UK buying advice ?|
Did a little measuring. The SPi blocks are as expected within 0.0001” in their pairs. The included angle is 89 degrees and 40 mins on the larger and 89 degrees and 50 mins on the smaller. So pretty close to 90, but just under.
The well used Brown and Sharpe pair are within 0.0003” of each other, but their angle is 91 degrees.
The vernier protractor measures 90 spot on with my “master square “ so whilst not traceable or calibrated I believe it for the roughness of these measurements.
Will 10 or 20 mins matter is something that the OP must decide, but clearly unless there is a spec and tolerance stated on the groove angle it might not be “exactly 90 degrees”
This is something to be aware of if you are planning to use a “precision” item for its none intended precision operation. Just because it was made with precision doesn’t mean it has the actual precision you need - unless the spec sheet says otherwise (and you can trust the spec sheet, but that is a different matter...)
Hope that is useful
Funny how people use tools differently.
Tjose ones are SPI from MSC and are, I would say, middle of the road on the price / performance scale - about £90 for 2 pairs of different sizes, claimed match to 0.0005”. They are numbered and I suspect match better than that as if you finish grind in a pair they really should be dead on.
Remember that V blocks are fixtures for holding things in the V and so the V may be 90 degrees, but is not usually specified. The only time 90 matters in the normal use of a V is if you are fixing square stock, and in that case a slightly more closed V might actually be better as it will have 2 line contacts, where as unless the stock is actually 90 degrees and perfectly finished it might seat in an unrepeatable manner.
I have 3 pairs about the size you are looking at I can measure the angle of later.
For angle fixturing you really want an angle fixture of some sort - like a sine table (for instance)
|Thread: Newbie: Can you buy a "desktop CNC Milling machine" for cutting steel?|
Have a look at FreeCAD as well whilst you are deciding.
it has most of the features you need and isn’t beholden to having a network connection unlike Fusion.
|Thread: 5C collet chuck with integral DI-3 backplate,anyone bought one?|
I have just realised that collet chuck means scroll chuck like tightening.
Both my collet chucks are really collet adaptors.
The CVA is an uncommon Jarno taper IIRC.
The one which came with the lathe:
This would only work if you can get 5c into the headstock taper.
I acquired from John Stevenson when he scrapped out his CVA.
I have both a d1-3 “nosepiece” and an internal sleeve for 5c for my CVA.
I usually use the sleeve as it’s direct in the taper, and the drawtube is a little shorter.
Thats useful because there is a wall just to the left of the lathe headstock.
Ill grab a couple pics later. I don’t remember there being any noticeable accuracy difference
|Thread: Work Shop Talk - Cleaning Sanding Belts & Sanding Discs Easily|
No such thing as 1, and everyone knows skips are for finding stuff in, not putting stuff in...
Guess my video would be a bit shorter...
|Thread: CVA LATHE|
This is mine, just after I got it into place. Its considerably more 'surrounded' now:
The saddle leaves no doubt about its intentions to be a precision machine:
The gearbox for feeds / threads is pretty comprehensive:
Mine is an Imperial machine, which I managed to pick up pretty well equipped, including most of the metric changegears:
Im missing 55 and 65, but have yet to need them in I dont know how many years of ownership (its over 5).
Threading is a doddle on it, even metric. There is a single tooth clutch on the leadscrew which runs both forward and reverse, ITs the lever above the round gearbox dial in teh first photo. That means you can just thread up, pullout the crossslide (to the integral stop), flip the clutch to reverse and power back to the other end , then wind in and go again. This works so well I usually do it for imperial threads as well (rather than using the halfnuts)
The surface finish it can give it beautiful:
Mine is still very accurate, even tho its not exactly 'new'. IIRC this test cut was parallel to 0.0001" over the length.
It might be a 'big' lathe, but in my experience it is very sensitive. This boring bar:
Was to open out the bore on some pinions I made:
And I did that in the CVA, partially because of the power feeds - no bumping the tool.
(Anvil for scale )
I am very happy with mine, and will continue to use it as long as I can. If it should develop a terminal fault Im not sure what I would replace it with, but I do know I'd be *very* sad...
|Thread: What's the general consensus please?|
I haven’t had a pillar drill since I bought my mill about 15 years ago.
I would get rid of you have no space.
|Thread: CVA LATHE|
I have a CVA and it’s an excellent machine. John Stevenson (late of this parish) used to run one and put me into them.
They don’t have the “following” of more traditional ME lathes, and are somewhat heavy to move.
As a result they tend to be cheaper than an equivalent Colchester or Harrison in spite of being a much better machine.
Screwcutting on one is a joy, the single tooth clutch means metric on an imperial lathe is trivial.
I’ll dig out some pics later.
|Thread: Variable rpm control for watchmakers lathe|
I have a VFD and induction motor on my watchmakers lathe. The control box has speed pot and jog functions, plus reverse. I called Newton Tesla and spoke to them - they put together a set - watchmakers lathes requirements being a bit different to a larger bench lathe.
|Thread: Lathe Rigidity Issues - Modification Opinions|
My first thought looking at the photos is that your grooving tool has a lot of stickout.
If your saddle isn’t in contact with the bed properly I suspect there is a
potential for “bounce” for want of a better description - the saddle dips as the cut comes on, then as the chip peels it lifts, changing the tool angle, which causes it to dip again....
Can you add ball bearing gibs like on a 10ee to the back of the saddle?
|Thread: Advice on Heat Treating|
The critical point is to get it hot enough, and heat it long enough to allow the transition from face centered to body centred (or the other way - I forget which).
I always quench to full cold then temper. Tubal Cain actually writes quench to not more than 50 degrees - I.e. cooler than 50.
I did have a deep fat fryer - turned up to 190 and again little risk of over temperature. Not good for higher temperatures, but “yellow” for most things I do seems enough. The parts don’t change colour unless exposed to air as the colour is caused by the thickness of the oxide forming on the surface.
There is no problem with the length of time at temper temperature as far as I know, just that higher temps draw the temper more.
|Thread: Brazing silver steel: any caveats/recommendations?|
You don’t say who your supplier is, but I would call Coventry Grinders.
Says they do none standard sizes.
|Thread: Leaky 540 plain bearing spindle|
my J&S 540 has decided to go all British on me and is leaking.
It has a palin bearing head, and the the rear seals for the wheel headset I think the culprit.
The parts manual is not much help - the front seal is 1” Oil Seal and the rear is 1 3/8” oil seal.
|Thread: Where to find a *good* optically flat mirror?|
According to this **LINK** - lambda/100
or Very Very Flat
might be a cheap alternative
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