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Member postings for lfoggy

Here is a list of all the postings lfoggy has made in our forums. Click on a thread name to jump to the thread.

Thread: New three jaw chuck suggestions
12/11/2019 21:24:26

I am going to treat my lathe to a new high quality three jaw chuck. Looking for a 125mm chuck with a D1-3 Camlock fitting. I want new chuck rather than second hand. Would be grateful for some advice.

I’m thinking a Pratt-Burnerd ‘super precision’ or maybe a ‘Grip-Tru’. How consistent are the ‘super precision’ chucks? PB website says max runout 25µ. What about the Grip-Tru - is that worth the extra complication compared to a good standard scroll chuck? Bison do a premium scroll chuck that claims a maximum runout of 15µ which seems unrealistic for a scroll chuck but then it is very expensive. That would be a three-jaw chuck with the concentricity of a collet system though.

Also considering two-piece jaws to allow aluminium soft jaws to be fitted more easily but have never used these so wondering how practical they are.

Thread: Pratt Burnerd 4 jaw Chuck jaw alignment
27/10/2019 17:57:29

I have now ground the chuck jaws using the setup below.

20191027_161042.jpg

Grinding wheel rotating at 5000rpm (too low I know) and lathe chuck rotating at 1000rpm. Removed 0.02mm at a time. Lots of sparks but otherwise uneventful. The finish on the jaws was very good.

The chuck is new and the jaws are a very firm fit in the slots with no discernible movement so I don't think much 'cocking' has taken place although i fully acknowledge the logic of grinding them tensioned in the closed direction.

Testing the newly ground jaws as below shows that the clamping face of the jaws is at right angles to the slots to within <0.01mm as below.

20191027_162134.jpg20191027_162122.jpg

I know some people suggested a slight taper on the jaws which is logical but hard to achieve so I just ground them straight.

I can now hold a test bar securely and accurately in the chuck - much better than before. I'm very pleased with the result and was surprised how easy this was to do.

23/10/2019 17:21:03

The jaws are a firm sliding fit in the slots with no discernible play so I am hoping that they will remain aligned during grinding.

I don't have a surface grinder but another option is to use a cupped diamond wheel in the milling machine with the jaws held in the milling chuck. I have used this setup to grind small amounts off hardened components in the past and it has worked.

I will try to get this sorted over the weekend and will post an account of success or failure....

Thread: End mill regrinding
22/10/2019 13:23:07

In my experience its the corner that wears out first and the edge of the flutes stays sharp for much longer. I usually sharpen just the ends but periodically give the edge of the flutes a very light grind. This does of course change the diameter of the cutter slightly.

I recently purchased a Chinese copy of the Deckel SO tool and cutter grinder which can grind both ends and flutes of cutters with ease. Best thing I've bought for the shop in years...

Thread: Pratt Burnerd 4 jaw Chuck jaw alignment
22/10/2019 13:04:51
Posted by Pete Rimmer on 22/10/2019 00:43:31:

I have I think 3 sets of 4-jaw chuck jaws of unknown provenance. Put up some basic dims of your jaws and I'll check the ones I have. In the unlikely event that one of those set match, you can have it.

Very kind offer. Let me try the grinding first but if that goes pear shaped then I may be in contact !

22/10/2019 13:02:02

Quick 'back of the envelope' suggests that at 1000rpm there will be a 50N radial force on each jaw, i.e. 5Kg . Cutting forces will generally be in the same direction as well. Maybe a bad idea though ! I'm sure a rummage through my scrap box will unearth a suitable ring against which to clamp the jaws.

22/10/2019 12:27:11

I was planning to position all four jaws the same distance from the centre using a dti, then set the chuck rotating and grind all four jaws at once with a pneumatic die grinder held on the cross slide and rotating in the opposite direction to the chuck. I was assuming that centrifugal force would hold the jaws in position. I only need to remove 0.1mm.

Does that sound reasonable?

21/10/2019 13:17:29

Many thanks for all the suggestions. Sounds like I just have a 'Friday afternoon' chuck. I'm told most days were Fridays in some factories in the 70s and 80s !

Will try regrinding the jaws.

21/10/2019 07:57:47

The chuck body runs true on all faces to <0.01mm runout with no distortion of the body. There is nothing to suggest the jaws have been reground (but who knows).

I've removed the chuck jaws and held them with the clamping face against a true vertical surface as below. Running a dti along the slot in the jaw confirms that the slot is not at right angles to the jaw face. All four jaws are out by the exact same ammount. This seems very odd. That degree of consistent inaccuracy cannnot be manufacturing error.

20191021_073817.jpg20191021_073829.jpg

20/10/2019 22:30:06

I've already stripped, cleaned and re-oiled. Apart from some congealed grease there was nothing to remove, not even a speck of swarf. The register is an integral camlock D1-3 and the chuck body runs perfectly true. All looks good apart from the issue described...

20/10/2019 20:37:26

I've recently acquired an 8 inch Pratt Burnerd 4 jaw independent chuck. It is stamped 'Made in England' and I think it was manufactured in the 80s. It seems to be unused or virtually unused as there are no marks on the chuck whatsoever and the D1-3 camlock fitting shows no signs of ever having been attached. The jaws have a perfect ground finish and are unmarked with no detectable play in their slots. When I fitted the chuck to my lathe to test trueness I found the chuck body to run true to <0.01 runout.both on the periphery and on the face. The clamping surface of the jaws however are not parallel. They are the opposite of 'bell- mouthed' as in the pic below. The taper is consistent on all four jaws. This may not matter too much for many applications but is definitely apparent when trying to grip a long and accurately machined workpiece.

What is the explanation for this? Were the jaws deliberately given a taper to accommodate wear or do I just have a badly made chuck? I am suspecting the latter.

I do reaslise that this taper would be easy to correct by the in situ grinding of the chuck jaws and I may well resort to this.

pic7.jpg

Thread: Cast iron cabinet theft
10/10/2019 18:23:19
Posted by An Other on 10/10/2019 17:54:21:

A guilty admission - In days gone by I (and many of my friends) got rid of old engine oil by putting it into the new oil tin, then 'accidentally' leaving it just behind the car, usually in a supermarket carpark, or some such, then walk away for a few minutes - the 'new' can of old oil invariably disappeared. Not a good thing to do, I know, but I often hoped the thieving s**s put the old il in their cars. Some people will nick anything.

Problem there is the thieves, when they realise they have nicked a can of old engine oil, will just pour it down the drain. You might as well just pour it down the drain yourself....

Thread: Exactly...
09/10/2019 15:06:00

Has anyone read this?

Exactly: How Precision Engineers Created the modern world. By Simon Winchester.

https://www.amazon.co.uk/Exactly-Precision-Engineers-Created-Modern-ebook/dp/B076FTNNXN

Have just ordered it and am looking forward to reading it...

Thread: Kennedy Hexacut 90 Power Hacksaw
19/09/2019 09:59:29

I had one of these in my workshop for a couple of years and I was very glad to see the back of it when I replaced it with a bandsaw. Mine was painfully slow with limited capacity and sometimes it just wouldn't cut at all unless you hung weights on the bow to increase downforce. Really only useful if you have a lot of patience and small amounts to cut !

Thread: Myford 254 thread dial indicator
09/09/2019 23:52:44

There are two gears on the indicator and you choose the one appropriate for the pitch you are cutting. The gear is selected by undoing a nut, removing and replacing the gear. As stated above, as long as the tooth count is correct it wont matter too much if the tooth profile on the gears is not perfect. If you are planning to do a lot of thread cutting I think making an indicator is definitely a realistic prospect.

09/09/2019 17:34:47

I have a metric 254 with the 3mm pitch leadscrew and it has an indicator fitted for cutting metric threads. It is a simple device and it would be possible to make one. It is basically a metal body which holds a gear against the leadscrew. There are two gears to choose from (28 and 30 tooth) depending on what pitch you are cutting. There is a dial with divisions connected to the gears that then indicates when to re-engage the half nuts. The metal body would be basic machining and you would need to be able to cut the gears You would need to find an original to copy, particularly for the divisions on the dial.

If you are anywhere near Birmingham you are welcome to inspect and measure up mine....

Thread: Knurling wheels (for the Hemingway Sensitive Knurling Tool)
28/08/2019 19:35:17

I purchased several sets of knurling wheels for my Hemingway tool from Zoro.co.uk. These are excellent quality. I now have fine. medium, coarse diamond knurls and fine straight knurls. The tool struggles with the coarse knurls on steels but is OK on brass and aluminum. The fine and medium cut well on steel. I seem to recall that Hemingway were only selling fine knurls, at least when I purchased my kit a few years ago.

Thread: ARC Euro Trading Great service
24/08/2019 20:55:45

I ordered a set of ER collets from ARC a few months ago and they sent me the wrong sizes. Although apologetic they said they could only replace them once they had received the incorrect ones back and asked me to post them. As I work full time this was a significant inconvenience. I did suggest that they arrange for the replacement items to be delivered and the wrong items collected at the same time but this was rejected. I was slightly disappointed that they were essentially transferring the hassle of remedying their error to me. Did eventually receive the correct items but still waiting for the promised refund of the return postage.......

Thread: English style bracket clock by John Tyler
24/08/2019 20:22:22

Yes, there is a long discourse on the theory of the fusee curve and the text does state the diameter at the big end and the small end of the fusee but there is no actual plan of either fusee and details of the recess for the maintaining power on the time fusee is left out. I did wonder is there were some pages missing from my book but i dont think so.

The dimensions are all very odd as well. My favourite so far is a part that calls for a 3.658mm hole. I know modern drills are accurate but that could be a challenge. Presumably that is some converted Imperial dimension...

Anyway, plates and pillars now complete, barrels and fusees next.

22/08/2019 20:44:53

I've just made a start on building the English style bracket clock described by John Tyler and am wondering if anyone else has built this?

I've made a few clocks before and purchased the book more for the plans than for the instructions. In spite of the rather long and wordy nature of the book I am finding it a little difficult to follow. There is a distinct lack of dimensioned drawings, a bizarre use of metric dimensions (which are just direct conversion of imperial dimensions often given to three decimal places!) and almost complete lack of any assembly diagrams. The two fusees for example are described in the text but there are no drawings of them which is odd.

I am anticipating lots of head scratching ahead. If anyone has any detailed photographs or plans of the movement, that would be very helpful, as would any other tips or advice.

Incidentally, I am also planning to use ball races instead of pivots on this clock like I did with an English regulator I completed a few years ago. This worked very well.

Thanks

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