lathe tool post advice

[Arbalist]

If you mean a grinding jig Chris, then yes, I use this one.



The little black one comes with the commercial tool but I prefer mine!

I must apologise for hijacking this thread somewhat, it was not my intention! 

[rotorhead]

That's just what I meant, life in our inner sanctum is much easier with purpose made gear.

As for hijacking, I'm just as guilty, but the intention was good, if not just to dispel the virtues of the 4 way...

[Andrew Wildman]

hijack away.  Its all good reading and ideas for the round-tuit list 

[Arbalist]

I first heard of the Tangential tool holder in MEW magazine and set about making a small example to see how well it worked. It's the little one on the right in the picture. It's didn't cut very well and in hindsight I'm pretty sure I just got the angle wrong on the tool bit. Some months later I was happily using an insert tool but ended up breaking several inserts on a job. With retirement not too distant I considered the cost of inserts compared to HSS and thoughts again turned to the Tangential tool. I decided this time to buy the commercial tool, it's the black one second from the right. It worked very well but this early model had to be set at an odd angle* in order to both turn and face without moving the tool. I decided to make my own that could simply be dropped into my four way at right angles. The third tool from the right was the second tool I made and works fine but I wanted more clearance around the tool bit resulting in the final MKIII version on the left.

* The commercial version has now been changed and can simply be placed in a four way at 90° like mine to both turn and face at the same setting. The reason for the odd angle on the original was something to do with using the tool for thread cutting I believe.




Ps that's a piece of solid carbide in the commercial holder so it can be used to take the skin off cast iron and the like if needed! 

[rotorhead]

Hi Arbalist,

They look very effective and a well presented finish.

Do you mind my asking what grade/spec steel do you use, I used to make mine from discarded hgv trailer brake camshafts, quite good stuff for nowt...

[Houtenkrullen]

If you mean a grinding jig Chris, then yes, I use this one.

The commercial one has a flat side down, your jig is turned 45 degrees (corner down) right?
May I ask what angle your jig presents the tool to the grinder? (I assume horizontal angle is square, vertical angle is ?)

Thanks for the nice pictures and info!
Peter

[Arbalist]

Peter, the table of my belt sander is set at 90° to the belt so the bottom of my jig is also 90°. The included angle at the top of the jig is 60°.

The tools are made from some old weights from a gym machine that was going to the scrap yard. No idea what type but it is steel of some description rather than cast iron. It cuts pretty well but there have been one or two hard inclusions in a couple of pieces but I've had that in gauge plate before.

I've only got a small 8 x 14 lathe and it hasn't got a lot of oomph so I don't (can't) generally take large cuts but the other day I was using my Tangential tool to take a fairly large cut on a long bar and I had a string of swarf coming off the work red hot so these things can remove a lot of metal if you need them to. It did occur to me that the design might struggle with interrupted cuts but I've had no problem with this so far.

[PekkaNF]

Just one fast one in between OT:s

One thing that might be of consequense (or not) is how you like to use DRO. If DRO has easy way to input tool (and finds the offset) then mechanical quality (repeatability) is fairly high on the list. And so is the price.

Then again if workflow is such that there is no need to swap tools in between cuts, then it's possible to zero (or dial in diameter for) each tool when needed and good repeatability is not such a problem.

I bought two QC-toolpost and I mounted the first one that way, that second one can be adjusted same relative centre heigt, making it possble to use QC-tools on both lathe without disturbing the tool height adjustment. In my opinion ease of tool chance is convenice only if you need to set the height only once.

I have used cheap Fourway TP and they don't work for me....I use a whole lot boring bars, rest of tools are always on my way, if I need porkypine I rather had it on tail end than cross slide.

O-O

Pekka

[Andrew Wildman]

So the tool post arrived from Arc today.  opened up the parcel and was impressed with the quality.  I took the old post off and mocked up the new one in position and....realised it was probably a bit small for the wide top slide on the L5. 

I ummed and aarred for a bit and then bit the bullet and packaged it back up again to exchange for the 200 size.  Arc were happy to take the tool post back.  Now just have to wait for the bigger one to arrive.

It was the right size for the centre height but the tools would have to hung out quite a way to clear the top slide.

[Houtenkrullen]

OK, on topic then :'(
:-)
I use a quick change toolpost most of the time (multifix). But I exchange it for some dedicated toolpost I have. For example one for cutting threads (quick retract: metric threads on imperial leadscrew...)
I think a fourway toolpost is quicker than a quick change if all the tools can be fitted to it. So for repetitive/specialized work it might actually be better to swap toolpost!?
A Morse taper tailstock is also quick change in a way, but 0sometimes a tailstock turret is more appropriate isn't it?

Still !I would not be without my qc toolpost!
Andrew, success with your new toolpost once it arrives, I am sure you won't regret the change.

Peter

[Jonny]

Previous lathe I used to gang up the cutters in several 4 way and boring bar type tool posts but did away with the 90 degree indexing. Harrison fitting on T slot, just slacken off and slide the lot out for the quick change type on its own T slot slab.

Liked it that much milled the M300 the same and done away with the 90 degree indexing. Sold the Dickson that bought 6 cheap 250 series holders.

[PekkaNF]

.....

It was the right size for the centre height but the tools would have to hung out quite a way to clear the top slide.

My Chinese lathe had really bad topslide, I removed it and replaced with a 20 or 25 mm square spacer , where I drilled and tapped two M16 or whatever that central post bolt is holes. The holes were spaced only about 20-30 mm away from each others, but designed that way that:
* Tool tip will be placed stable side of the lathe guideways, no cantilever load on cross slide front shear
* AND with a conservative tool shank overhang big piece would clear the topslide and make it possible to turn just a little part that does not go over the cross slide, but you can get close to it. My lathe has central height of 125 mm or so, this is limitting factor many times.
* Possible to use limited travel of the cross slide to do some right/left hand boring/threading + do all external turning on one setup
* possible to turn the TP "ways" outside (towards you) and do a little oversize turning near the chuck. Handy if you have one big lefthand facing tool - it's used here as plain turning tool and right hand facing.

It's funny how much even 10 mm move on tool post central bolt has influence on how close you can get. This was very important, because I traded rigidy over top slide, but I can imagine that it does not hurt to do a little dry run with a few favorite tools on the TP before mounting it permanently.

Pekka

[Jonny]

They do vary quite a lot Pekka, current M300 has far less cross travel than the old 140 probably around 2", so much so have to slide tool post across in T slot for knurling and boring when i put an angle on the cutter.

Weirdly the M300 gone the other way over previous lathes, even minimal overhang its a rarity top slide will foul tail stock or even a large J&S  revolving centre.

[Andrew Wildman]

Tool post arrived and it looks like it will fit well. Just got to make a nut and/ or stud to fit the l5. Update coming.....

[Jonny]

It will fit but too small, even these were small used for 10 yrs http://www.arceurotrade.co.uk/imagecache/bf7b8c8b-20ae-4fd4-8170-a34900ede141_700x323.jpg

http://pic20.picturetrail.com/VOL15/728921/1252422/311844089.jpg

[Andrew Wildman]

So the tool post is installed on the Harrison.  I took the advice and made a tangential toolholder,
.  Seems to work well, although I have only ground the tool free-hand.  Next job is to make an adaptor for the tool grinder to fit 1/4" hss.

The design sits on the cross slide for max stiffness.  The single screw holding the tool in place looks a bit weak, but the bit of hss is a tight fit in the slot and I don't think it will move.  It is all about as simple as it can get.

Row o toolholders:


While I was at it (and waiting for some screws to complete the slip roll project) I made some more toolholders for the small lathe (the natural colour ones):



I bought the tool post for the small lathe about 4 years ago from Chronos.  When I tried recently to buy some more toolholders, the ones they sent would not fit as the design had changed very slightly.  The only option was to churn a few out on the mill and shaper.

[chipenter]

A toolholder for a dial guage makes it quick to set up , my one flipes thruogh 90 degrees .

[howsitwork?]

  Cracking idea Jeff

[Jonny]

Have had that trouble a few times Andrew. Post may have an 100 series or AXA stamping, only buy stating that.

The better ones will have marking on the tool holders ie 250-201 which is BXA known by others. Some retailers have no idea and go by centre height, the blocks may measure ok but dovetail something else.
Its only a problem when retailer sells unbranded/marked.

[seadog]

Just to clarify, the 250-100 and 250-200 are different sizes. The tool holders aren't interchangeable. Make sure you buy 250-1xx for the 100 size and 250-2xx for the 200 size.

[Andrew Wildman]

I had a bit of a fiddle with the TCG and grind tangential lathe tools:



jobs a good-un!

[Arbalist]

Nice job!