'Dickson' T3 tool holder help

[Smouser]

On my Elliott Omnispeed lathe, I have a T3 quick change toolpost.

I have been looking for more T3 tool holders on eBay, but they don't seem to come up very often (for £50 or less per tool holder).

I found a listing by 'Bluefox' on eBay (an Indian company) for 5 x T3 tool holders which worked out at £46 per tool holder delivered and I placed the order.

This morning they arrived all individually packaged.

Excitedly, I opened one up and ran over to the lathe to see how the tool holder would fit.

Unfortunately, it seems that the tool holders don't fit too well

Here is a photo of one of the new tool holders.

There is a gap between the new tool holder and the toolpost (circled in red).

This is how my existing tool holders fit.

Nice and flush on the old or original tool holders.


The gap between the new tool holder and toolpost is approx 0.55mm.

Side-by-side comparison

I placed the two bottoms of an old and new tool holder on each other to compare the difference.
The old tool holder is on the bottom, and the new on the top.

The 'V's seem to align perfectly (although the outside edges of the new one are slightly longer.

The problem seems to be that the flat part of the new ones is ever so slightly 'thicker' than the old ones (circled in red).

Further demonstrated by holding a flat edge against the surfaces.

How do I fix this?

As far as I can see I have 3 options.
1. Use a face mill to take off ~0.5mm on the new holder (something I can do 'immediately').
2. Get my SG up and running properly and then grind ~0.5mm off (I will need to level the SG again, balance the wheel, learn how to operate a SG and then have a go).
3. Send the holders back and keep looking for holders (least preferred).

 

[Agroshield]

There are many suppliers of the Dickson-type toolposts.

To the best of my knowledge, there has never been a specification or drawing published by any authoritative source of their dimensions.

That means different suppliers wil have different ideas of what is correct and the best you can hope for is that everything from the same supplier will fit together.

In your photo, the surface against which the scale is resting should not touch anything. When clamped up, there should be a gap between that surface and the face of the toolpost.

I think what you should determine first is the centre-to-centre distance of the Vees. I am not altogether sure how you measure that on the toolpost itself*, but try to do so for all three positions (and perhaps take an average).

Measuring the same on the holders is a little easier with two ground pins. Measure over their outside and deduct one diameter. Measure all your 'good' holders and all the new holders. Once you know how the land lies, you can make all those distances the same. Then start removing other material to allow the holder to seat and clamp up correctly.

* Maybe two pairs of pins, each pair clamped together so they touch and then sit the post on top of the two pairs and again measure outside-to-outside, deducting two diameters.

 

[Smouser]

In your photo, the surface against which the scale is resting should not touch anything. When clamped up, there should be a gap between that surface and the face of the toolpost.

Thank you @Agroshield.

I looked at the old tool holder and there is a gap of 0.2mm between the tool holder's surface and the toolpost when clamped up. That means the 'V's do all the alignment and 'touching' of surfaces between the tool holder and toolpost.

On the new tool holder, that surface is too 'thick' or high which prevents the 'V's from properly engaging.

As it is now clear that those two surfaces on the tool holders are not critical for alignment, I might have a go at using a face mill to take a little off.

 

[Smouser]

Face mill fitted.

One side done.

Second side done.

Burs

Burs removed.

No more gap!

I cobbled a quick video together.

Only 4 more tool holders to go

I have not looked at the face mill's inserts yet. The tool holder seemed a bit hard.......

 

[thecroman]

I've got some (probably) T3 holders spare, trying to get T2 and these arriving instead. From the top of my head it's either two straight shank holders, or a straight and a morse taper holder. It'll be in the new year as they're in storage, but if you're interested I'll dig them out and get dimensions and you can have a pair for half what you're paying in your original post

 

[Smouser]

I've got some (probably) T3 holders spare, trying to get T2 and these arriving instead. From the top of my head it's either two straight shank holders, or a straight and a morse taper holder. It'll be in the new year as they're in storage, but if you're interested I'll dig them out and get dimensions and you can have a pair for half what you're paying in your original post

Great!
I would love to take you up on your offer!

Thank you very much.

 

[addjunkie]

Can you popup a link to these, so I can compare to mine. I need more.

 

[Smouser]

Can you popup a link to these, so I can compare to mine. I need more.

Sure.

Pardon our interruption...

The description and photos of the tool holders leave a little to be desired...

I offered £230 which I felt was a fair price and the seller accepted.

I still need to check the other 4 for fitment.

Got distracted watching rugby.

 

[Smouser]

All done.

I will get some tools in them and change the square bolts over to allen key ones to match my other tool holders.

I don't think I have enough allen key bolts, will probably need to order a few more.

I checked the inserts on the face mill.

None seem to be chipped, always a bonus.

 

[RichardM]

What size are the socket heads, 8 or 10?

 

[Agroshield]

Square head bolts are good as they do not have recessed heads that become filled up with swarf or coolant or both.

Socket head bolts are good as they do not have square heads that attract stringy swarf.

If you change them, it is wise to use dog point grub screws, as the ends can swell under clamping pressure and are then difficult to remove from the holder should you ever need to do so.

 

[RichardM]

Just turn a couple of threads off the end for the same benefit.

 

[Smouser]

What size are the socket heads, 8 or 10?

They are M12 socket heads. The ones on the existing tool holders are 45mm long.

I do have a load of longer M12 socket head bolts - I could shorten them but it seems like hard work.

Square head bolts are good as they do not have recessed heads that become filled up with swarf or coolant or both.

Socket head bolts are good as they do not have square heads that attract stringy swarf.

If you change them, it is wise to use dog point grub screws, as the ends can swell under clamping pressure and are then difficult to remove from the holder should you ever need to do so.

I prefer the socket head bolts.

The point of having a load of tool holders is that I don't need to change tools often. Just swap the tool holder and tool.
That means I will rarely undo the socket head bolts and can deal with the swarf that may be stuck in there.

If I do shorten the existing M12 socket head bolts I have, I might as well make them dog-point screws/turn a few threads off at the bottom.

 

[minimutly]

Dog point screws, everyday's a schoolday here...
FWIW I would go with socket heads, they would easily be cleaned by removing the holding and tapping upside down.

 

[Smouser]

I chose the silly way to do things.

I could have bought 30 x dog point screws from Zoro for £7.50. I would have had to order a few other bits too to get free delivery but I have been looking to get some cheap 'WD 40 equivalent' sprays.

These look like a great deal.

Anyway, as I said, I went the hard route.

Got some of the too long hex screws I had and marked them up where they needed cutting.

I then grabbed a grinder ond chopped them shorter.

Tape removed.

Stuck them in the lathe to make them dog point screws.

The ends of the thread got 'folded over' after they came out of the lathe and they did not want to screw into the holders easily/at all.

Ran them all through a Die which did the trick.

All fitted.

Tools fitted in the new holders.