Making 46 Dickson style quick change tool post holders (picture heavy)

Sorry will try again

Edited By DavoJ on 07/04/2013 08:51:17

Hi Davo,

Are you having a problem with pictures?

Neil

If its the same post you have made on other forums then copy & pasting the whole thing won't work on here. You can't use teh IMG codes so will have to load each image url using the image icon along the top of the reply window

J

Why not just link to a previous post on another forum ?

Like this.

**LINK**

Hi Davo

That is certainly impressive! 46 holders though - I have 16 and sometimes have difficulty finding the right one - with 46 you may be in danger of Quick Change, Slow Find!

John - thanks for giving us the facility to view Davo's project I don't think this site could cope with that volume of images in any way that would provide a readily followed sequence.

Cheers

Norman

Edited By NJH on 07/04/2013 11:06:16

That would be easier to do, thanks for the tip.

**LINK**

It was a lot of work, but so was posting it all with text. All up 52 photos and that took hours to upload.

Dave

Edit, oops I should read a little better as you already provided a link. My link is to another forum.

Thanks again

Edited By DavoJ on 07/04/2013 13:27:02

Hi Dave,

I picked up a Dickson-type toolpost and 4 holders for my Myford lathe a few weeks ago. While the standard holders are not unduly expensive here (UK - around £15) your excellent write-up has inspired me to consider making special toolholder types that are not commercially available.

Obviously, all aspects of making the toolholders need care in the set-ups used. The one feature that I find intimidating, though, is that the distance between the female Vees machined on the holders must exactly match that between the male Vees formed by the toolpost corners.

In Photo 22 of your sequence titled "Finishing the V's" you show the final machining of the female Vees on the holder. You're apparently using an endmill in a vertical head set over at 45 degrees. I presume you finish machined one Vee and then, leaving the milling head at the original setting, retracted the vice and moved the table the required distance to machine the second Vee. If that's right can you please tell us a bit about how you established (a) the first Vee setting and (b) the exact distance to the second Vee setting to match the toolpost Vee spacing exactly?

Thanks

Joe

Edited By joegib on 08/04/2013 14:31:03

In my previous post I asked Dave how he ensured that the distance between the Vees on the toolholders was exactly right. I see he's since dealt with exactly the same question over on the HSM forum so to save him the trouble of posting here I'm quoting his answer below:

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I used the DRO wich has 0.005mm glass scales, the V's are exactly 60mm apart on this one so I was working to a round number at least.

Once I set the head over to a true 45 degree using ground angle blocks and checked with a degree gauge to be sure, I picked up center with the first holder set in the vise with a secure stop and it was just a matter of locking all axis's other than the Y and going 30mm either side of center and they came out spot on.
One the first one I did marked the face of the V with a marker texta and then turned it around to see if it was truly cutting at 45 degrees just to be sure.

One side (on each side) of the V is cut with the side of the end mill and the mating side is cut with the bottom, so all done in one set up. The end mill worked perfectly as the V's are 90 degree V's.

With the parallels in the vise that gave the correct distance for the depth of the V's, and after each one came off the mill I would check it on the lathe to make sure the handle locked in the same position for each one as I had marked the tool post with a marker.

About halfway through the post I mentioned a couple that where colored red and blue by me. They where slightly under size by around 0.2-0.5mm (from memory) on the outside as something went on when band sawing those couple, so these where done on there own after the others. It was either take all the blocks down to match them or just leave it as was, which was a lot less work and I left those holders as the the spare blanks anyway.

I think I mentioned earlier that after hogging them out I used a nice new Dormer 20mm end mill to finish the V's with plenty of coolant. I don't have a grinder so I had to get the best surface finish I could from the mill.

I went to the extra trouble to triple check the set ups as once you start loading them in there is no putting it back one, and I didn't want 46 blocks of scrap metal.

I hope that explains it all

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Hope you don't mind me doing this Dave.

Joe

Thanks Joe, I just found this post and I don't mind at all.

I am glad it has inspired you to make a few special ones yourself and it's good to see that as it was a lot of work putting it that post together with 52 pictures and adding text for them.

I think they are easier to make than the dovetail ones, though a lot of people think otherwise.With these it's just basic tooling other than the key seat cutter but it's a lot more durable than a dovetail cutter with it's delicate tips.

Dave

Hi Davo

Have I sprung another OZ?

The Lock tool knurl in one of your photos..... They used to be down the road in Lygon St Brunswick A suburb of Melbourne It was great to watch them forge the tools.

Cheers

John (Melbourne)

Although the basic shapes involved in creating Dickson style tool carriers are quite simple the accuracy requirements are stringent and tolerances small. Due to the overhung nature of the cutting loads you need at least simultaneous line contact on all four sides of the Vee faces over pretty much all of the Vee length. The ideal is full area contact on all faces but that level of precision is for the likes of Moore Tool & Jig and similar companies. Even they struggle.

Incomplete contact considerably reduces holder stability making it likely to tip under heavy cutting loads or parting tool type jam ups. Even factory products can suffer. I've demonstrated this a time or two with the T2 size set on my Smart & Brown 1024 when the HSS blade type parting tool jammed up. Surprisingly the tool didn't break although the first time an unnoticed crack in the blade carrier opened up and a 3/8 inch (ish) section of the lower blade holding ledge broke away. Clearly the carrier had suffered similar mishaps in a previous users care. Repair was "interesting" but the cost of a new blade carrier provided plenty of incentive.

The wide spacing and large areas of the registration Vees make the Dickson style the most rigid and stable of QC system designs but performance in practice can be a little disappointing. They work well enough, especially if kept properly clean, but the results never seem to be as good as they ought. Inexpensive (and expensive!) no name clones have a fairly well documented reputation for instability due to excessive tolerance spread. One day I shall blue up my tool posts (3) and carriers (17) to see exactly what the factory Dickson and Rapid brand fits are like. On current schedules this will probably be somewhere north of 2025!

Interestingly the double Vee lathe bed, as used by SouthBend, is much more relaxed over tolerances. Theoretically as few as 3 points of contact is sufficient for adequate saddle guidance although 5, suitably spaced, ones is a more practical minimum. Especially on small Southbend machines which lack an anti rise gib under the front of the saddle. Not having to deal with overhung loads makes a big difference. Its always surprised me that more makes didn't do things the SouthBend way especially as a bit of running in wear soon bumps up the contact area.

Clive

Edited By Clive Foster on 11/04/2013 18:48:35