chuck spares

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'

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.

Can't you make one or repair the original ?

Martin

!/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 ?

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

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

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.

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.

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.

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.

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 result Geoff.

.

Good decision, Geoff

... and yes they are named after Mr Allen

MichaelG.

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.

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.

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?

GWR fasteners list them here

Richard

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

Regards Nick.

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.

Thanks, order placed.