Independant 4 jaw chuck butchery

I have a 125mm independent 4 jaw chuck which came with my WARCO WM250-VF lathe. It is marked with a manufacturers initial "H". This chuck as you will know if you have one, is rear mounting but I would like to make it front mounting if it is possible.

I would like to use the existing threaded blind holes on the back as a guide and drill right through them and out to the front following which the front would be counterbored to take new caphead fixing screws.

I have spoken to two people at WARCO, the first one said the chuck would be to hard to drill (I don't believe that). The second asked me how much of a chance I wanted to take, I told him that I did not want to take any chance at all. His very helpful reply was "then don't drill it". I felt that that sort of reply is what you would expect from someone who doesn't know what he is talking about.

So I'll rely on the forum. Can I go ahead without causing internal damage?

Rik

Rik, I would say that as long as it is easily drillable, you should have no problem. Ian S C

Just been playing with my 4 jaw,125 dia. Chinese made, M8 fixing. One fixing hole is right in line with a jaw screw so a no-go. Chuck body seems drillable and maybe the 3 holes can be re-positioned, maybe your chuck is different. I had considered fitting 3 drive dowels in the rear holes and drilling 3 smaller holes thru' from the front and tapping ,say M6, into the mandrel flange.

Surely the easy answer to this is to strip the chuck down, plot where the holes you intend to drill are going and then establish if they are going to interfere in any way with the workings of the chuck. If in doubt don't proceed.

I can quite understand the response from WARCO and think it is quite reasonable as this is not something that I would expect them to have any knowledge of and is well outside of their remit. There is no reason why he/she should have any knowledge of what could go wrong if you decide to make a non standard modification to your chuck

Martin

Just had a look at the 5" that came with my 280 chinese charicters on lable, the 4 mounting holes are equispaced between the jaws so not a problem there and as there is no scrol etc like a 3-jaw can't really see what would be in the way. A quick file test suggests if it is hardened then it is only very slightly done.

Whats your reason for front mounting? going to use it on a rotary table or something

J

Safest to strip and check. Make sure there is room and depth for the counterbore to take the head of the socket screw. Hard to visualise a chuck that doesn't have room but we all know about ASSumptions. Its always the silly, "too obvious to check" stuff which gets me!

Many front mount four jaws have the fixings at about 1/3 rd to 1/2 radius from the centre rather than out on the rim. Leaving aside the big industrial A series mounting stuff is this just a different way of going about things or are there specific advantages and disadvantages relative to rimwards fixing which may be worth considering depending on the planned application.

Clive

Hi Ric,

I don't want to sound unhelpful, but Warco's response sounds like that of a company who have been asked to replaced equipment damaged by customers who said 'I was only following your advice'.

If it works, do me short write up on what, why and how

Neil

Thanks all for the mostly helpful advice. Jason, the idea as you suspect is to mount it directly on my 4 slot rotary table. Neil, if the job can be done I'll willingly do a short piece for you.

Rik

Edited By Rik Shaw on 08/08/2014 13:48:53

Have just had another look at my 4 jaw. The backplate is held on by 4 screws and carries the 3 M8 fixing screws. I t looks as if the backplate could be rotated to allow for thu' drilling.

I drilled some extra holes in a Chinese 3 jaw, I can't remember what for. It was a little on the tough side but nothing special. Use a good make of drill, preferably newly sharpened drill and you should be okay.

David

There is carbide drills these days that will drill holes in steel to 58 Rc, failing that, it can be easily edm drilled also.

Neil

Hi Clive

Advantage of holes placed close to the OD of the chuck allow the front fixing chuck to be removed from a lathe with greater diameter workpiece still in situ as turned, thus ensuring concentricity of the part when the chuck is transferred for the next op on a RT or in my case a dividing head.

Emgee

Rik, the only thing you need to look out for is the thickness of the casting between the jaws, as the back of the chuck is hollow, although the threaded holes from the back could be taken right through. There may not be enough metal in some parts to take the counter bore. Ian S C

UPDATE:

Job done no problems.

Rik