A & R Precision ‘Dickson’ Toolpost — Screws Used

[joegibParticipant @joegib]

Hi,

I picked up one of these toolposts plus some toolholders a few weeks ago and I'm pretty happy with the kit. But, I'd like to replace the capscrews supplied with grubscrews. The screw diameter measures about 4.90mm so I assume these are M5 x 0.80mm pitch.

Unfortunately, I've mislaid my Metric screw gauge so I can't verify this. Can anyone who's already made this change confirm that the screws are indeed M5, please?

Thanks

Joe

[joegibParticipant @joegib]

[Brian WoodParticipant @brianwood45127]

Hello Joe,

I've just checked mine and get a good match for 0.8mm pitch.

Just a word of caution though, M5 can be mistaken for 3/16 BSF at 32 TPI; 0,8mm pitch is equivalent to 31.75 TPI and the diameters are close, so I would say older holders might be Imperial, newer will certainly be Metric

Brian

[joegibParticipant @joegib]

Hi Brian,

Your reply led me to look around a bit more. I gather the M5 'major diameter' is 4.91 which is more or less spot on with the A & R screw I measured. As it happens I rooted out some nominally M5 screws I'd forgotten (obtained from Lidl!). These measured 4.88mm and were a slightly more 'wiggly' fit in the toolholder. I looked up the 3/16 BSF specs following your reply and these show a major diameter of 4.763mm which would make for an even more wiggly fit. That pretty much settles the issue for me — M5 it is.

Thanks for your trouble.

Joe

[ZiggarParticipant @ziggar]

or you could just email them and ask……

[JohnFParticipant @johnf59703]

Joe, Why are you changing to grub screws?

They are indeed 5mm and the original Myford ones are 3/16 BSF, I have both types plus some others of variouse parentage, Myford and A & R being the best by far.

John

[Mike PooleParticipant @mikepoole82104]

2BA is another thread very close to M5x0.8. Myford use both on the ML7R cross slide adjusment and locking screws be careful not to mix them up.

Mike

Edited By Michael Poole on 22/04/2013 23:25:02

[joegibParticipant @joegib]

Hi gents,

Well, I've some sympathy with the view that Dickson toolposts have too many 'sticking-up bits'. When looking at DavoJ's project to make 40+ Dickson-type toolholders posted a week or so ago I was struck by how the use of grubscrews rather than capscrews neatened up the appearance of the units.

In particular, use of a capscrew as the locking screw for the height adjuster looks a bit clumsy to me — I'd rather use a grubscrew that disappears within the head of the adjuster. But I accept this is a taste and fancy thing and probably doesn't bother most people.

Joe

[Mike PooleParticipant @mikepoole82104]

I find the biggest irratation with cap screws is that the socket fills with swarf, the larger sizes use square heads and don't retain swarf.

mike

[David Clark 13Participant @davidclark13]

Hi Michael

Fill the hexagon with a blob of plasticine,

Keeps the swarf out.

regards David

[Peter TuckerParticipant @petertucker86088]

Hi Michael,

I keep a piece of blu-tack secreted about my machine for cleaning swarf from places like cap screw sockets.

Peter.

[Sub MandrelParticipant @submandrel]

Surely grub screws are even more vulnerable to swarf than cap screws? I can see that square topped screws would work well.

Personally I like the convenience being able to use the same 5mm long handle allen key for most machine adjustments.

Neil

[Ian PParticipant @ianp]

I may as well add my 0.02p to this thread since it has long since answered the original question. I think the choice of screws used in quick change toolholders is partly to do with personal preferences and partly to do with what is available.

In my case I prefer the square headed bolts (5/16" UNC) but I accept that these are probably not available in 2BA or M5. I do have some toolholders with grub screws and I use those for tools that never need to be changed (indexable tips/parting blade etc). Because I dont have many holders the square headed bolts are a boon because they never get filled with swarf.

As regards putting plasticene in hex sockets! words nearly fail me, it falls into the 'shake and vac' category (throw stuff on the carpet and then remove it!). May as well screw a plate over the front door letterbox to stop draughts, you can always remove it when the postman comes. With Dickson type toolholders just unclamp and tip out the swarf.

Maybe someone should write an article showing how to make a set of polished brass dome topped, O ring sealed covers for protecting cap head bolts. (put in ME though as I take MEW)

I think 'sticking up bits' are what make Dickson toolpost so useful, and far less hazardous than the three (usually two) sharp tools poking out of 4 way toolposts.

Ian P

 

 

 

 

 

 

Edited By Ian Phillips on 23/04/2013 22:06:42

[LynneParticipant @lynne]

A & R Precision tell me that the bore of their qctp is 16mm. The toolpost on my Myford lathe lathe is 7/16" I am puzzled why the popularity with Myford owners, or am I missing something glaringly obvious. Regards DLJ

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Phillips on 23/04/2013 22:05:00:

In my case I prefer the square headed bolts (5/16" UNC) but I accept that these are probably not available in 2BA or M5.

… the square headed bolts are a boon because they never get filled with swarf.

… As regards putting plasticene in hex sockets! words nearly fail me

.

I'm with you there, Ian

An interesting "modern" alternative to Square Head might be 12 point

… I haven't yet found a UK stockist, but they are made in M5

MichaelG.

[joegibParticipant @joegib]

(1) The unit is supplied with a 7/16" 'top hat' adaptor for the Myford topslide post.

(2) It's British-made, conforms to the original spec (as opposed to some of the Chinese clones) and from A & R Precision, at least, is reasonably priced.

(3) I quite liked the look of some of the American-made alternative styles but they're not generally available over here.

In the end I decided to use grubscrews for the height adjusters only.

Joe

[geoff walker 1Participant @geoffwalker1]

I recently bought a Dickson tool post with 4 holders from A&R precision.

All seems well until I clamp the tool holder in the tool post.

The "problem" is that it clamps too soon, nowhere near TDC on the eccentric.

The holder locks in place but it just doesn't feel right, not really secure?

Is there an optimum clamping position for an eccentric. Should it be close to TDC?

I can see a solution to the "problem", if indeed it is a problem.

Any thoughts anyone

[LambtonParticipant @lambton]

Geoff,

If the clamp locked out too near TDC then even slight wear or stretching of the clamping system parts would mean permanently loose clamping as even going a little past TDC would be detrimental. . Over the years even genuine Dickson clamping "bolts" become a bit distorted and flare out a little. I would not worry about the situation unless tool holders become loose which being used.

[LambtonParticipant @lambton]

Geoff,

I forgot to ask if you have spoken to A & R about your concerns if so what was their opinion.

[Harry WilkesParticipant @harrywilkes58467]

Mine are the imperial ones

H

Posted by JohnF on 22/04/2013 23:15:42:

Joe, Why are you changing to grub screws?

They are indeed 5mm and the original Myford ones are 3/16 BSF, I have both types plus some others of variouse parentage, Myford and A & R being the best by far.

John

[Roderick JenkinsParticipant @roderickjenkins93242]

Hi Geoff,

I had a similar problem with some spare holders recently purchased from A&R: the flange on the bottom of the height adjusting nut was too thick. These nuts are hardened, or at least toughened, but I managed to skim the bottom with a TC tool. I was a little disappointed . Still, they're OK now.

Rod

[John Stevenson 1Participant @johnstevenson1]

I used to have a large TOS lathe with a big Dickson type holder on it 4 or 5 size and I got that fed up with swarf wrapping round the stick up bits I reverted to allen grub screws and cut the hight screws down as much as possible.

It made it a far easier and safer lathe to use.

[geoff walker 1Participant @geoffwalker1]

Hi gents

Thank you for your replies.

I did ring A&R, there view was that clamping pressure is uniform at all points on the eccentric. I’m not so sure, it currently locks a good 45 deg. from TDC, which as I’ve said just doesn’t feel right.

A small amount skimmed off the inside face of the shoulder on the spring loaded clamping bush will draw the bush in a little more and the eccentric will get closer to TDC.

I am still mulling it over a may give that a try. I do take your point about getting to close to TDC, that would be detrimental.

Some years ago I made GH Thomas spring loaded retracting tool holder and found that the eccentric locked the tool securely (and felt right) about 10 deg from TDC.

Thanks again geoff

[Clive FosterParticipant @clivefoster55965]

Checking my T2 size Dickson and Rapid tool posts with "various makes" holder collection the real thing seems to go 60° or 70° (ish) between fully slack (BDC) and locked. Dickson being more 60° and Rapid more 70° (and a bit sometimes). Much less would surely adversely affect height setting as the setting flange would not be properly supported by the snail groove.

I guess the industrial boys would know best as you need a good lock with a hefty cut going on.

Socket head screws in a swarf area. Barf!!

If the sticky up bits are a problem with swarf its time to look to the tool chip breaker. Not futz around re-engineering the QC system to make it less convenient to use. As I've said before the conventional QC system is more than a little illogical. Given a modicum of engineering intellect it being as easy to arrange equally rapid interchange of loaded tool blocks. So if you have a mega swarf problem, as with nylon for example, some nice 50's fashion streamlined blocks could be made with minimal projections.

Clive

[Neil WyattModerator @neilwyatt]

Hi Geoff,

As a dispassionate observer, i suspect that it doesn't feel right simply because it's different to what you were used to.

The real test is does it hold firm under an interrupted cut.

Neil

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