chuck spares

[Perko7Participant @perko7]

I've somehow managed to break one of the screws used to tighten the jaws on a 1920-something Burnerd 4-jaw independent chuck. I know it's a bit old, but was in fairly good condition, until now. Seems like some swarf might have jammed in the thread at the bottom end of the screw as i was loosening it. It was pretty tight and hard to turn. Then result is that the screw has parted at the 'waist' which engages with the fingers on the back of the chuck jaw.

Is it likely that anything like this would be obtainable as a spare part? (sound of furious straw-clutching here…..). The screw is 12tpi and 1/2" external diameter.

I'm already resigned to making one but thought i should at least pose the question 'just in case'

[Perko7Participant @perko7]

[MalcBParticipant @malcb52554]

Geoff,

Most if not all imperial Burnerd chucks are now obsolete and sourcing chuck spares other than from Ebay is difficult. I have had limited success in the past from Thame Engineering, Rotagrip and Universal Workholding Ltd in Netherton. There may also be some milage in giving Myford a call as they always seem to have some odds & ends knocking about.

[Martin KyteParticipant @martinkyte99762]

Can't you make one or repair the original ?

Martin

[Chris Evans 6Participant @chrisevans6]

!/2" 12 TPI may well be a standard whitworth form. Can you tell us the size of the chuck ? I have a couple of really old chucks knocking around, where are you in the country ?

[John Stevenson 1Participant @johnstevenson1]

The hard bit and the bit you haven't mentioned is the chuck key fitting.

Usually it's a blind square which is quite hard to replicate but some do have hex heads.

At 1/2" x 12 sounds like a standard whit thread and so possible to make or adapt out of a piece of 1/2" whit studding.

At work at moment and short on time but I'll post a bit more on this later

[RobboParticipant @robbo]

Geoff,

You don't say what size this chuck is. If it is one of the smaller, 3" – 4", these use 1/2" x 12 tpi BSW thread.

You can make a replacement yourself using a 1/2" BSW grub screw, this will, of course, have a hex socket "head".

They are usually 1¼" long.

Like Chris, above, I've got an old 3" 4-jaw with one broken screw waiting to be repaired. It has been waiting about 5 years now! But I would want to replace all 4 screws with the 1/2" grub screws so they match. Point is there would be a screw or two spare.

Think we need full measurements of your chuck and screw.

PS:  strange it has broken at the "waist", it's usually the square socket that splits its sides.

PPS  I saw this on ebay and bookmarked it, I know its the wrong size but include the Link for general info –http://www.ebay.co.uk/itm/201694271987?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Edited By Robbo on 22/03/2017 14:12:42

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, one Norman Hurst wrote an article in MEW 175 page 56, about making new screws from 1/2" x 1 1/4" Witworth socket grub screws, he addressed the chuck key issue by making a new key, using an Allen type key.

There is also a thread about a broken square hole on a four jaw chuck and reference was made to Normans article. **LINK**

Regards Nick.

[RobboParticipant @robbo]

Just remembered that Rotagrip used to sell the 1/2" x 12 tpi screws, with a hex hole. The downside was they cost, as I remember, about £18 each.

[davebParticipant @daveb17630]

I bought some 1 1/2 X 1/2 grub screws to replace the broken screws on my Pratt Burnerd 4" 4 jaw chuck, cut the waist on the lathe and made a new hex chuck key.

[Perko7Participant @perko7]

Thanks for all the helpful responses, also had a similar reply from Tony at lathes.co.uk.

The chuck was 4 1/2" diameter, and the screws match the dimensions for 1/2" Withworth.

Looks like i'll be making 4 new ones from suitable grub screws (if i can get ones long enough) or from threaded rod. If i have to use the threaded rod I might try making a 1/4" (6mm) hex head on the end so I can use a 1/4" drive socket of the style which fits into a battery drill/screwdriver.

Will let you know how I get on.

I'm in Brisbane, Australia so not much chance of taking advantage of any offers for assistance from UK, but thanks to those who offered anyway.

Cheers, Geoff P.

[Perko7Participant @perko7]

Today I purchased six 1/2" BSW x 1 1/2" long grubscrews, plus a t-handled Allen (or is it Allan?) key to tighten them with. Total cost A$22.70. Just need to machine a waist on them, trim to length and they're ready to go.

[Chris Evans 6Participant @chrisevans6]

Good result Geoff.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Geoff Perkins 1 on 24/03/2017 02:46:00:

Today I purchased six 1/2" BSW x 1 1/2" long grubscrews, plus a t-handled Allen (or is it Allan?) key to tighten them with. Total cost A$22.70. Just need to machine a waist on them, trim to length and they're ready to go.

.

Good decision, Geoff

… and yes they are named after Mr Allen

MichaelG.

[RobboParticipant @robbo]

Geoff,

If you want to see Norman Hurst's article from MEW about doing this, then PM me.

Though I made several screws before he wrote that, and it isn't difficult.

[Perko7Participant @perko7]

I bought the grub screws from Blackwoods, a general tool industrial supplies outlet. Other specialist bolt & nut suppliers also had them but were further away.

Thanks Robbo, i had a look at the link provided in the post by Nicholas Farr, and it seems that my solution should be fairly straight-forward too, but if i get stuck i'll be sure to PM you!

Won't have time to work on it this weekend though, got the grandchildren over so another type of 'playing' is the order of the day.

[Engine BuilderParticipant @enginebuilder]

I have the same issue with my 4 jaw. Does anyone know a supplier of 1/2 x 1 1/4 BSW grubscrew in the UK?

[TrickyParticipant @tricky]

GWR fasteners list them here

Richard

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, just bought some cap head bolts off GWR Fasteners through ebay, very good and prompt service.

Regards Nick.

[RobboParticipant @robbo]

Posted by Tricky on 26/03/2017 16:57:34:

GWR fasteners list them here

Richard

They are just the ones, and at a reasonable price too. Availability of these seems to vary, I have provided several people with them because they couldn't find any commercially. Time to augment my stock I think – thanks Richard.

[Engine BuilderParticipant @enginebuilder]

Thanks, order placed.

[Perko7Participant @perko7]

After a few days away to attend an interstate funeral I've finally got back to repairing my chuck. I've turned the grub screws to matching lengths, and now need to turn the groove/neck which engages with the fingers on the back of the chuck jaws.

Being a relative newbie I'm not sure how to go about it. I've learnt from past experience that driving a wide tool directly in can be hazardous to one's health, so a narrow tool is the way to go, but it needs to be stiff enough to not be disturbed by the threads on the grub screw as it is presented to the work .

Should I machine them off first using a different tool? (I'm assuming I should but happy to be corrected)

Should I make several overlapping full depth cuts, or shallower cuts from side to side to the required width of the groove/neck?

The grub screws are very hard, probably HT steel, so any tips on making cutting easier using carbide-tipped tools? My lathe is not set up for coolant so I usually turn things dry when using tipped tools.

[davebParticipant @daveb17630]

I wrapped some copper shim around the screw to protect the threads (brass, tin or alloy would do), held it in the 3 jaw chuck and cut the groove with a parting tool, cut to depth then adjust width to suit. The HT screws cut OK with sharp HSS tools. Dave

[RobboParticipant @robbo]

Geoff

I made a mandrel of 1" round bar, drilled through and tapped the thread of the grub screws. The screw to be machined was adjusted to protrude the right amount, and locked in place by another screw inserted from the other end. Mandrel in 3-jaw chuck as usual

Turned off the unwanted threads with a wide parting tool in the rear toolpost, one at a time, then smoothed off at the correct diameter.

[Perko7Participant @perko7]

Job done, mounted each grub screw in the 3-jaw, faced off the end, measured the required distance to the groove, made one deepish cut with a parting tool then advanced the tool progressively by about half it's width each time to take successive cuts to the required width of the groove. Repeated that until the groove was the required depth. Then did the same for the remaining 3 grub screws. Total time required about 1 hour, probably could be done faster but no need to rush it. HSS parting tool worked fine, no lubricant required, nice smooth finish for the chuck jaws to bear against, very happy with the outcome. 4-jaw now back in operation.

Thanks for the assistance.

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