Modifying multifix tool holders

[Dave Sawdon 1Participant @davesawdon1]

I’ve got an A size original multifix tool post and holders from a previous lathe which are one size too large for my 254S. Having just taken some measurements, it seems I could use it if I reduced the bottom of the tool holders from 9 mm to 6mm. I presume the steel will be hardened so it would need grinding.

This seems a bit radical, and suspect that it’s better to sell the A size and buy new, but wondered whether any else has taken the same step.

[Graham MeekParticipant @grahammeek88282]

Having read your earlier post and having many years experience of the Multifix tool system. I would not entertain trying to modify the toolholders. From memory these are case hardened steel. Removal of 3 mm of material from the tool slot will leave a soft clamping area for the tooling.

Removal of this amount of material from the base of each toolholder, such as to retain the versatility of the system does not come without problems.

You may find the removal of this material distorts the ground mounting face which may affect the repeatability. For my part I would sell this item and obtain something more suitable. Or use smaller tooling.

When I had my own 254, Myford supplied it with a fitted Dickson system.

Regards

Gray,

 

[Mark RandParticipant @markrand96270]

I tried the underside of a genuine Multifix toolholder and it’s about 40HRc, so easily machinable with carbide or with HSS at a lower speed.

[DC31kParticipant @dc31k]

[Michael GilliganParticipant @michaelgilligan61133]

Thankfully, there is a far superior option being discussed in the concurrent ‘topic’

MichaelG.

[JasonBModerator @jasonb]

How many tools do you have that are too tall? Is skimming some material off the bottom of those an option, most insert holders are not so hard that carbide won’t cut them.

Back to the tool holders again I have seen Dickson and Aloris types have their bottoms reduced with carbide insert tooling so may not need to go as far as grinding.

Like DC I have also suggested machining the topslide in the other thread and for once I kind of agree with him about the surface the tool sits on, if you are anything like me the tool goes into the holder once and does not come out again except for a couple I keep for little used tools and they are generally small HSS specials. So lack of cas ehardening would not really be an issue as there is little wear.

[Graham MeekParticipant @grahammeek88282]

My observations for most part were why I would not modify the system. Of course it is up to the individual at the end of the day what they do.

I too have seen Dickson tool holders which have been locally machined on the base, to clear the topslide. With a fixed 90 degree separation between the mount faces on the main body. This approach will not compromise the usage. However turn the main body to an oblique angle and it will cause a problem.

The Multifix system on the other hand has 40 positions and thus all the base needs machining. Unless the user wants to compromise further and make the system a Dickson type. (The multi-positions have been of great help to me in the past when doing jobs).

I also do not doubt the soft mounting face in the toolholder would present too many problems, to the average home machinist, but again it is an observation. Multifix deemed that this surface should be hardened and ground square to the serrations for a reason. It certainly ensures the tool geometry is presented to the work correctly. This seems like a good policy to me.

Machining the bases of any insert tooling would be my choice and harks back to my advise to use smaller tooling.

Regards

Gray,

 

[PeteParticipant @pete41194]

I’ve not really read anything Gray has ever posted I’d disagree with. I’m sure he’s forgotten more than I’ll ever know. Compared to the ubiquitous 4 way tool post design, the weak link with qctp’s is that tool holder hanging out in space with no rigid connection between the tool holders bottom and the top slide surface. The actual cutting tool rigidity verses it’s cross section would still be far stiffer and much more resistant to our cutting loads than almost any of us would ever be subjecting them to on our more hobby sized lathes, against just how rigid those tool holders are. I’d modify the cutting tools height before ever touching the tool post or tool holders. It’s obviously a whole lot harder to put metal back on than it is to take it off should you ever need the tool post and tool holders for use on another lathe. Modify the cheapest and smallest part first is a fairly good general rule in my opinion.

I bought a left hand replaceable tip tool manufactured by Mitsubishi some years ago. It was a couple of mm’s too large to fit my Emco compact 5 tool holders and still be on the lathes center line. All I had for a mill was the little C5 round column and HSS end mills. Instead I just slowly fly cut that tool the necessary amount with a cheap braised carbide tool. If that mill can modify industrial grade and hardened lathe tool shanks, then doing the same on the lathe itself or with any other small mill, it should certainly be possible. I’ve not found even good brand name lathe tool shanks that were extremely hard. I doubt they ever would be. Yes there still hardened a fair amount for durability and toughness, but using some logic, then too hard would seriously risk the tool breaking during use.

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