Chuck Backplate reprise

Is there enough space behind the backplate to use nuts?

Dave

You haven't made clear what the screw are binding on. Do they fit easily in the chuck body, including the counterbore?

I've drilled the body of a TOS chuck with no problem, for mounting to a rotary table. I doubt yours will be hardened, but you'll soon find out if you try

If it's not hard, it's your choice which you do. Probably depends whether the counterbores are big enough for the M10 caps.

Probably not.

What, I should think.

Cheers Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Yes, they do fit easily into the body, heads and all. The problem is that the threaded holes in the backplate aren't perfectly aligned (they're not far off though I say it myself) and so there is binding at the interface between the chuck and the backplate. Basically I think the problem is the screws are slightly bigger than allowed for in the design of the chuck mounting system.

True enough. I may try this but I don't know how well my cheapo pillar drill will cope with boring out a hole by a mm or so. Also I'll need to check the hole depth - my drill only has 50mm of quill travel.

Thanks for the reassurance,

David

A man with a plan ! :-)

I will have a look tonight, it may certainly be easier than the alternatives. Locking washers be an idea too do you think ?

Thanks,

David

Move it round 45 degrees and drill a new set of holes.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

I thought of that, but the holes I've got are about as good as I can do. I did them by spotting through then drilling and if I look through the holes in the chuck at the holes in the backplate they align OK as far as a visual can tell. I really think that I'd need to use M9 or

3/8" cap screws to improve the odds but I don't know where I can obtain either of these ? (Always assuming the heads are no bigger than M10 cap screws, presumeably true for M9 anyway).

Another alternative would be to tap the chuck body and drill out clearance in the backplate but it's have to be M12 and I don't think there's enough room between the holes and the register to make a good job of this.

David

3/8" cap head are a lot smaller than M10. Just been and measured some up, 3/8" are 14mm on the head, M10's are 16.25mm but these can vary a bit maker to maker What length 3/8" cap heads do you want, probably got some here, just measured 4 2-1/2" long ones up and probably got 3"

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Thanks for that very kind offer. I have a look tonight and see what room fthere is. I may try the idea of nuts on the end of longer M10 bolts first if they'll fit and unless someone speaks out against the idea. I'm pretty sure there will be room. Otherwise I'll take you up on your offer - M9 would give more room to manouvre but I don't know if they even make them. Using nuts will save having to buy another tap as well ;-)

Thanks again,

David

Probably a stupid suggestion, but, have you tried the back plate in every 90 deg. position ? I am always being caught out by this! When you spot drill through you must always use the same orientation as that used to drill the hole, in the case in question I would have made a mark with a felt pen on the back plate and on the chuck. It is often better to fit one screw and tap its hole before proceeding with the subsequent holes. The job can then be secured with the first screw and will not shift during the machineing of the subsequent holes. I prsume you spotted the back plate through with a drill that only just fitted the hole in the chuck, if you spotted through with the tapping size drill then your hole will certainly be out by about the height of the thread, which is why when one is drilling the holes through two parts to be bolted together it is normal to drill through both parts with the tapping size drill and then drill through the upper part with the clearance drill.

Regards Brian

Another thought:

If the shank 10 mm tap will pass through the hole in the chuck:

Tap through the chuck into the back plate using the chuck as a guide Insert one bolt and tighten. Repeat for the remaining bolts

Job done! It is a bit of a bodge but the slightly elongated holes should still have more than enough strength. Examine the tapped holes if they are not obviously awfull you should be OK. If not then follow John's advise and drill another set of holes at 45 deg. to the originals but follow my advise in the previous post. Incidently when I say "spot" I mean touch the large drill through sufficiently to for a decent cone to centre the following tapping drill.

My objection to putting long bolts with nuts is that it is an accident waiting to happen. Eventually in an unguarded moment your hand is going to wander into the path of the nuts and the resulting thwack will make your eyes water! Admittedly the jaws of the chuck may well hit you first which will be even more painfull, but it is better to avoid unnecessary risks, there are plenty that you have not thought to catch without leving predictable one! We have all been there!

When I was in apprenticeship I was assigned for a time to a department called "Tool Developement" which was nothing to do with nasty devices advertised on the WEB but which trouble shot production problems. When it reported to the foreman we had a 10 minute interview during which his hands were were on his desk the left on top the right, Finally he lifted his left hand revealing his right hand which had one finger missing and another half length. He presented this to within a few inches of my face and said "AND I WANT NONE OF THIS! IT WAS ENTIRELY MY OWN FAULT!" It was a dramatic to instill a sence of safty which which has stood me in good sted for the rest of my life

Regards Brian

Turn and harden a transfer punch to fit the holes in the chuck closely and use it to mark out the new set of holes.

Mark Rand RTFM

Thanks to all who answered. A variant on the above got me off the hook

- the original bottoming tap I had was a little on the large size and I ran this through the threads. This opened them up enough to get the screws in. Not ideal but it worked and it seems OK from the quick job I turned afterwards.

Thanks again,

David