I also have a Dickson toolpost on a wm280, and there was a lack of sufficient clamping force onto the topslide, I fitted a needle roller thrust bearing and suitable washers which helped.

Should I find a round tuit, then I will be fitting a larger diameter post to the topslide, as it is too spindly IMO, I think this will cure the problem.

I don't think changing the toolpost type will help much, it would only assist if it reduces overhang, and sometimes, eg boring, the overhang will be much the same anyway and the problem will resurface.

Edited By Cabinet Enforcer on 05/01/2020 18:28:23

From the original post it looks like the toolholders are moving, not the toolpost.

I've found the Arc ones very good but check 'dimension H' suits your machine.

Neil

Even without a stop pin in the hole it shouldn't move with the sort of cuts that lathe can manage.

Verify that the slide surface and toolpost base are actually flat and that the toolpost stud is perpendicular to the topslide. Use a bit of engineers blue to see where its actually touching. Shouldn't be an issue with a fairly new machine but I've seen enough older machines with such problems to always check.

Centre stud out of perpendicular is the easy one to miss. Doesn't take terribly serious knock to put them out a little. If the hole in the centre of the toolpost has minimal clearance the toolpost will never sit down well. First time I saw that stud issue I didn't notice until we were getting desperate and decided to wind the stud out to re-machine the topslide top as the blue showed poor contact. Whereupon it wobbled as it turned and we said "Ahah, gotcha".

I usually put a thin aluminium shim underneath to give better grip. Other folk prefer thin card but that needs changing every year as it tends to pick up oil.

Clive

I had a problem with a Dickinson type holder coming loose and I realised that they were some replacements that I had bought at the show at Doncaster. I had a closer look at one of the ones that came loose and found that the cam action was not going round as far as the originals. With closer inspection there was a step between the two and I then milled the excess material off with a carbide end mill. Problem solved I have had no holders coming loose since.

David

You have just highlighted the main reason why I am still using the original four way toolpost on the Smart & Brown model A. It can hold two tools securely, not 4, that's a joke, and as all the tools are the same height, no shimming is required.

I have made a second toolpost for the lathe which can hold a 12mm shank boring bar, (there are several solid carbide shank ones to choose from with different style and grade of inserts), and also, a 26mm parting blade, both with close to zero looseness.

As Cabinet Enforcer says probably better to verify that the Dickson clone is properly made and everything is fitting properly first. Standard checks are pretty straightforward although they are more usually employed to verify that different makers interpretation of the Dickson design are actually fully compatible.

1) Locking lever travel from released to lock should be around 90°. Much more and it will be going past centre so lock force is reduced, much less and it won't come up to full lock. On real Dickson and industrial standard clones full release is around 10° or so past centre in the release direction so, judging by mine, effective travel is likely to be of the order of 80°- 85°. Look at the holding tongue movement without a toolholder fitted and it should be clear whats going on. Mark the full lock angle of the handle with a holder fitted first.

2) Height adjustment screw not perpendicular.

3) Collar in the height adjuster a poor fit in locking shaft groove.

4) Height adjusting collar too large so it tries to push the holder away from the post.

3, 4, and 5 should be obvious if you look closely from the side.

5) Registration Vees misaligned or wrong centre distance. Offer up the holder by hand and check with engineers blue. So long as one side on each male and female Vee has a decent fit over most of its length it should work fine. (There are limits to the precision that is practical at an affordable price.) Partial fit usually indicates something is at an angle. Fit on two sides of one Vee only means it will almost certainly be insufficiently stable although a small error may well pull up OK. A couple of mine are imperfect when tested but perform fine.

6) Grot in the body. Very common, my industrial standard ones need cleaning out every year. Seem to be a magnet for itsy bitsy teensy weeny swarf.

7) Poor fit, contact or other errors in the actuating cam system. Inexpensive clones sometimes aren't as well de-burred as you'd ideally like. Easy enough to pop the actuator out by setting at the right angle and pushing the locking tongue back against the spring so the shaft can be withdrawn. Sorry I can't tell you the right angle. My hands know what to do but the brain gets confused so I just do it and try not to think.

8) Mounting technique. Proper way to use a Dickson is to push the toolholder into place against the toolpost Vees then lock it up. Relying on the tongue to pull things up square is bad practice as there is considerable friction invoked. It can also bend the adjuster stud. ("I used to be a toolmaker" Paul got an earful for doing that to one of mine where brand X and Rigid Tipo were a bit short on clearances.)

Old Mart makes an excellent point about the simple reliability of the four, two in practice, way block. Especially if you are primarily a carbide tool user so the cutting edge height doesn't get altered by re-sharpening.

I'm always surprised that lathe makers, or a canny aftermarket guy, didn't come up with a simple quick change system for loaded toolblocks. Especially as so many of the higher end machines had a face ratchet alignment system under the standard fourway post. Quick release by interrupted thread, 1/3 rd turn locking cam et al would seem relatively easy for a manufacturer to arrange. If I ever figure a simple to make in the home shop version my Dicksons / Rapids will be history. Hmm 18 holders and 3 S2 posts to sell. I'll be rich!

Clive

Go for the Arc provided its dimensions (dovetail is most important) are close to those of Aloris. They are quite forgiving of the dimensions of the dovetailed tool holders while still giving excellent repeatability. Extra tool holders are very inexpensive. The Warco style requires the Vs be precisely spaced and parallel for repeatability. I doubt the Asian manufacturers will maintain the level of precision to allow you to buy replacement tool holders that fit properly.

looks like you won't be able to use cutting tools larger than 12mm shank (12.5 + 12 = 24.5) . depending on your knurling tool design it may work and I'd also take a close look at any parting tools.  Stud should knock out so you can make a new one or modify existing though there raised area of the topslide around the stud may also need to be taken into account (don't know the ID of the bottom of the ARC unit.

As Said check the fit of your existing holders particularly any bought from other sources as one factory's version can differ from another, the few I have had for my Dickson that did not fit when bought have all been adjusted so they are OK.

The same may well apply to any "cheaper source" extra holders for the ARC one that may not be to exactly the same spec

Edited By JasonB on 06/01/2020 07:50:44

I fitted a wedge type tool-post to my WM250 some years ago and it works very well. The WM250 is just a little smaller than your lathe but I found the AXA or 100 series to be the right size. Only difficulty I had fitting was replacing the the main tool-post stud which was somewhat larger than the original. Difficulty was mainly down to a raised boss on the top-slide which was too big to fit in the tool-post block and had to be removed. You can't bore out the wedge type tool-post as you can with the piston type.

I did a write up of fitting on Journeyman's Workshop this also details making a cross-slide adapter so that the tool-post can be used without the top-slide in place, very rigid.

John

Edited By Journeyman on 06/01/2020 09:46:11

Did you find the 2nd page the photo is on there!

Check carefully with the larger 200 series that the tool-holders do not bottom out before the tool is on centre.

John