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Member postings for Dave S

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
25/04/2021 08:47:38

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.

Dave

Thread: Small saw. Proxxon or something else
23/04/2021 19:41:49

@Dave S -
Interesting to know that 3000 RPM at 4inch diametre makes for good grinding. Whether that makes for good CUTTING on a 1mm abrasive disc I don't know.

Cutting with a grinding disk is grinding

I have some thin wheels for my surface grinder, which IIRC runs at a similar speed in terms of rpm. It’s surface speed is slightly more, as it has bigger wheels when new.
Angle grinder disks are reinforced to cope with gorillas mishandling them in the cut. Even so I think a 1mm angle grinder cut off wheel would run and cut fine at much lower rpm than a typical angle grinder runs. I’d go and try it if I really thought you would take any notice...

But given those numbers, can you explain why are all the circular table saw manufactures are all so adamant that their machines can't cut steel? If just don't make sense...

Product liability would be the first thing. If I designed a machine to use a course toothed saw to cut wood which is fairly soft I wouldn’t say it could cut metal which isn’t - that would lay you wide open to claims for failure.

Cutting metal generally involves higher forces, and most tools are built with cost as a major consideration. All then”cheap” table saws I’ve seen have pressed tables and large gaps around the blade. Not what you want for cutting thin bendy stuff. Wood at least will destruct as it tries to wedge into the blade / table gap.


> I do wonder if John S is trolling or just indecisive.
Back off. Absolutely not trolling.

I am a newbie but learning fast. However it seems that every time I am about to make a decision I get new information that renders what I was about to do a poor decision.

As I said somewhere in one of your threads the best decision, especially if you are up against a deadline, is to make one. So far I have seen something like 4 threads where you jump off into another line of investigation without having seemingly actually done anything with the information from the previous ones. You have impossible yet also imprecise specifications and don’t seem to listen when people say you can have that, but this compromise applies - usually it’s because you seem to want a Rolls Royce but only pay Robin Reliant prices or some other unicorn fantasy. You might be better to sub contract your machining, you won’t get new toys to play with, but your device could be finished. That would however mean properly specifying what you actually want and I’m not sure you know this.
Dave

23/04/2021 16:56:38


To slow for grinding appears to be a case of “internet knowledge”

My surface grinder is supposed to run 71/2” wheels iirc, so I didn’t look at that.

However:

77b25010-66ad-4f0f-a18e-15a2f8b3692a.jpeg
Bog standard bench grinder from B&Q. Takes 150mm wheels, runs at just under 3000 rpm.

Homebrew cutter grinder:

b437c0d6-cac1-4a6c-9e95-18975067cff4.jpeg

Has a 4” cup in it currently, also runs a 4” saucer.

Speed:

eae922b6-260e-4332-90c1-5f4f23803e9b.jpeg

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.

Dave

23/04/2021 12:42:00

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

Dave

Thread: Precision V-blocks (32mm & 7") - any UK buying advice ?
20/04/2021 19:12:42

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

Dave

20/04/2021 12:43:25

Funny how people use tools differently.
I use my V blocks all the time. So much so that I bought another 2 pairs.

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.

Dave

20/04/2021 08:12:03

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)

Dave

Thread: Newbie: Can you buy a "desktop CNC Milling machine" for cutting steel?
15/04/2021 18:24:03

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.

Dave

Thread: 5C collet chuck with integral DI-3 backplate,anyone bought one?
14/04/2021 19:16:16


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:

1f637ba0-3070-482e-a74d-7ecfaa89d710.jpeg
d9e34a1f-9031-4861-9da6-4a5ad9c64447.jpeg

This would only work if you can get 5c into the headstock taper.

07cda6bd-a2b2-4848-9497-92cacf59f6d7.jpeg

This one:3d147f2d-0b2b-46c5-ac6c-4969454ee34b.jpeg

I acquired from John Stevenson when he scrapped out his CVA.

89521e03-7d56-4693-b94d-06e972e02c8f.jpeg

is D1-3 and I think would work as long as you can get the drawtube through.
I haven’t measured the runout on either, but both do work good enough for my needs.

Dave

14/04/2021 08:43:38

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

Dave

Thread: Work Shop Talk - Cleaning Sanding Belts & Sanding Discs Easily
25/03/2021 14:56:05
Posted by Mike Hurley on 25/03/2021 09:00:15:

Probably. Similarly I just wonder when someone will come out with a video to mirror Stacey Solomon's TV prog about decluuttering your house (how much instruction do you need to throw crap away?) i.e how to declutter your workshop!

2 hour video telling you to

1. Find stuff you don't need and is of no use (and not recyclable of course)

2. Put in skip

Getting off topic - I do apologise

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...

Dave

Thread: CVA LATHE
24/03/2021 21:43:02

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...

Dave

Thread: What's the general consensus please?
24/03/2021 12:54:05

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.

Dave

Thread: CVA LATHE
24/03/2021 12:33:38

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.

Dave
.

Thread: Variable rpm control for watchmakers lathe
19/03/2021 09:28:34

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.

Dave

Thread: Lathe Rigidity Issues - Modification Opinions
18/03/2021 08:19:44

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?
Dave

Thread: Advice on Heat Treating
17/03/2021 22:16:46

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.
Now I have a kiln I tend to use that - it’s got good control and I can bung the parts in and ignore them without risking overheating the tempering.

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.

Dave

Thread: Brazing silver steel: any caveats/recommendations?
07/03/2021 08:11:50

You don’t say who your supplier is, but I would call Coventry Grinders.

**LINK**

Says they do none standard sizes.

Dave

Thread: Leaky 540 plain bearing spindle
24/02/2021 20:55:52

Evening all,

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.
Has anyone replaced these?

The parts manual is not much help - the front seal is 1” Oil Seal and the rear is 1 3/8” oil seal.

Dave

Thread: Where to find a *good* optically flat mirror?
24/02/2021 12:16:37
Posted by Anthony Knights on 24/02/2021 09:21:21:

Sheer speculation-how flat is a hard drive disk?

According to this **LINK** - lambda/100

or Very Very Flat

might be a cheap alternative

Dave

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