Myford Super7 Chuck and Tool Holder points

Hello again Gentlemen!

So I have spent some time getting my lathe setup and true. Without going on too much, there are 2 main questions I have: (plus some bonus sub-questions!)

1) Myford sell a 100mm small bore and a 125mm big bore 3 Jaw for the Super7. Both can be supplier fitted with a Small Bore super7 backplate of 1&1/8x12tpi.

On the Myford website, it states in the 125mm chuck (without backplate) listing that the 125mm chuck is NOT SUITABLE FOR 2MT (small bore) lathes as it is too heavy.

I called Myford. They said it is fine, and that loads of people have that fitted. On this forum, there are multiple threads discussing this, but with no real conclusion. Myford assure me it is fine, and that there will be no excessive wear after many years use. Has anyone heard / experienced the contrary?

1.a) Bonus Q: Can you think of any reason why I would be better off with the 100mm vs the 125mm? For the extra £25ish, I think it's worth being able to hold slightly larger parts. (Although the majority of my work is going to be at least for the time being, smaller parts.)

1.b) Bonus Q2: The Pratt Bernard chucks by Myford get a LOT of praise. However, many people discuss/voice opinions that cast iron is more flexible than steel and various other arguments. The PB chucks are around £220ish. RDG sell HBM and other makes for ~£70 ish for comparable sizes. Are they to be avoided given the choice?? Why would you buy a PB today for almost 3x the price? Are they really that much better generally speaking.

2) Lathe tooling. Due to the access I have to a Warco lathe, I already purchased a bunch of 12mm tools over the year before getting my S7. The S7 has a 4-way toolpost, which only works with an 8mm tool plus a ~1.2mm shim.

Myford advised me to buy the ML10 ONLY toolpost as the toolholders are more adjustable and can take a12mm tool. Has anyone done this? Is it workable / practical / sturdy? (Thicker tools vs ?thinner? tool holder) Ideally I dont want to have to re-buy a full set of tools as it's about the same price as a quick-change toolpost which brings all it's own advantages .

Everybody is stating to get a Quick-change toolpost, both on multiple threads here and elsewhere. Additionally, on here, none of the threads on S7 tool sizes mentioned being able to quite easily be able to use a 12mm tool...! Is this a new development?

Lastly, there is lots of conflicting information on Myfords website, and Ebay, forums etc. I'm looking for proven facts people on here may know, as I am not sure what information to go on from online. (Also, many of the tools/gauges etc use stock images of other tools, so often even the images aren't a reliable source of info!!) Everything I've been told by one of the very helpful gents at Myford seems to make sense, I am just curious if anyone else has done the same as what I am planning. (125mm PB 3Jaw, and QC ML10 toolpost on my S7 to hold 12mm tools.)

That is about all. Thanks in advance!

Many thanks.

Del

On the Myford website, it states in the 125mm chuck (without backplate) listing that the 125mm chuck is NOT SUITABLE FOR 2MT (small bore) lathes as it is too heavy.

I called Myford. They said it is fine ...

.

Myford advised me to buy the ML10 ONLY toolpost ...

Edited By Michael Gilligan on 13/08/2019 17:04:18

I bought a Pratt Bernard chuck and it is superb it repeats within a couple of thou and also have a HBM CHUCK ON MY rotary table which is ok but I can clock up the rotary table one to centre when need be. The one I would buy is the Pratt Bernard any day and I would try Rotagrip as well for a price to compare.

David

Go for the PB larger one, the only slight drawback is a small loss of bed length as the body will be longer. Also the larger bore comes in handy at times when the job is a bit bigger. The chuck bodies which screw directly on to the spindle without a backplate will save a little length.

You may be beating yourself up Del!

1. Putting a heavy chuck on a small lathe will cause excessive wear. Assuming the bearings are in good nick, does the extra wear matter if the lathe lasts longer than you do? Maybe not. If the bearings are already on the way out, running a heavy chuck ain't going to help, but then perhaps it's time to fix the bearings anyway. The nature of wear is such that no-one can give a straight answer. It's your risk. Personally I don't like overloading equipment without good reason, and it doesn't sound as if you have a good reason - 'the majority of my work is going to be at least for the time being, smaller parts. '

2. You have an S7 that can't take 12mm tools. Not surprising as it's a smallish lathe. I think messing with tool-post options to fit large tools just because you happen to have a few is the tail wagging the dog. Get new tools to fit the lathe instead.

3. A QTCP saves time. I manage without one. Buy when you need one, which might be never. Depends on what the lathe is used for. When the time is right you will know!

4. Pratt Bernard are nice chucks. For amateur use they may be worth the extra money. Smooth operation and probably, but not necessarily more accurate. They confer considerable boasting rights as well. Actually I think all 3-jaw chucks are unreliable because repeatable re-centring requires a 4-jaw or collets. I get on fine with an HBM. Personal psychology matters here: I'm a bodger who likes making things other than models. Provided tools do the job I don't care about much about them. Others enjoy having 'quality' tools and are thoroughly irritated by second class cheapos! Act depending on your personality type because it's your hobby. If you hanker after 'quality' and have the spare cash, why not?

I think you have an unusual requirement. Be interesting to see if anyone else has ever fitted a heavy chuck and a ML10 QCTP in order to use 12mm tools! I'd guess not.

Dave

Arc sell a model 000 quick change tool post suitable for the Myford, the 13mm tool gap will only just accomodate a 12mm tool. With the toolholder set to its lowest point, the base of the tool will be 4mm above the topslide. As a result, the top of your 12mm tool will be 16mm above the topslide.

Geo. H. Thomas in his book "The Model Engineer's Workshop Manual", gives the centre height over the topslide as 0.646' or 16.4mm which will allow for only 0.4mm play.
But he also mentions that this distance may vary from lathe to lathe so you may or may not only just manage to get your 12mm tools at centre height using this particular QCTP.

So if you are determined to use your 12mm tools then your best bet would be to place them directly on the top-slide, shimmed up as necessary to centre height, using the standard Myford clamp type toolpost to hold them down.

Clive

If I were starting from scratch again, I'd probably do the same as I did first time round with my S7, which came tool-less and chuck-less. I was on a tight budget as I'd just bought my first house and interest rates were then 15% on the mortgage.

I picked up a 4" (100mm) 3 SC jaw and a 6" (150mm) independent slimline lightweight 4 jaw. My theory was that the 3 jaw was smaller and lighter and would suffice for most work, I'd need a 4 jaw anyway, so a larger lightweight design would supplement the 3 jaw nicely.

I was fortunate in that I dropped on a Griptu for the 3 jaw, and later added some external and soft jaws as I came across them at reasonable prices. The 4 jaw is one of the Pratt Burnard ones with 4 hollows in the main casting and a small backplate, just big enough to support the chuck properly and get all the screws in.

Because the latter has a backplate, it provides a small step behind the chuck, to I can fit a washer and drawbar through the headstock and thus safely run the lathe in reverse for screwcutting away from the headstock.

Toolpost wise I was initially using the original Myford single tool clamp and kept a set of shims with each tool, but found it all a bit of a faff.

I bought a quick change toolpost with one holder, but one of the very simple ones. Essentially a steel cylinder bolted vertically to the standard topslide bolt. On that there slides a simple steel block, bored to suit and then split to enable a clamping bolt to nip it up at the correct height. One side is slotted to accept the cutting tools in the conventional manner. I then found a length of steel, chopped it up and more or less duplicated a few more QC toolholders, some slotted as per original and a couple drilled to accept boring bars.

Because of the lathe centre height, and to leave enough of the steel toolholder below the slot, 10mm is about the biggest toolbits which will fit; a problem of which you are clearly aware.

I was able to source a couple of 1/2" carbide insert toolholders, and milled a bit off the bottom of each, so they would fit my toolholder.
That still left me with the problem of how to hold lengths of 1/2" HSS bars. For these, rather than cutting a slot for the tool, I effectively cut a rebate. i.e. a horizontal slot with no base to clamp the toolbit onto.

Next job was to source a bit of bedframe angle iron and weld it across the rebate, effectively making a square hole, on the lower left hand end to house the HSS bar. Not conventional perhaps, but it served my putposes for many years and cost very little other than time. I never did get round to dressing all the surfaces to make it look pretty, so can't really write it up as an article, but you should get the gist.

I've just had a quick look on the web for suitable photos and spotted This Article, which is more or less the same design. http://www.swarfer.co.za/lathe/toolpost.php

Bill

If you feel the need to use He-Man insert style tooling on the 7, the easy way is to just determine the shim requirement and superglue the required thickness of material to the bottom of the 12mm tools so they can be directly off the top slide with the original clamp fitting. Simple and quick.

Get some 10mm tooling for use with a quick set tool post. No prizes for guessing which tools you will use most of the time!

If you are desperate to use 12mm tooling in a quick set format, then some people have adopted the expedient of milling down the top slide to suit. Wouldn't be my first choice ( neither would milling the bottom od the 12mm tool because, er, um, it wouldn't be a 12 mm tool any longer).

Myford started listing the 5” SC chuck so big bore users could make full use of the 26mm hole and 4MT taper in the spindle. On a small bore lathe you will only be able to hold shortish stock before it bottoms out in the 2MT socket. So the benefit will be limited.

I rarely use the 5” chuck on my big bore lathe as I find the 4” more manageable but I guess it all depends on what you use it for. You could always use the 6” independent chuck or an ER40 collet chuck for larger stock. I believe ER32 collets are now available in the range 20-26mm too.

The Dickson style toolholders can be modified to take 12mm tools, see Steve Jordan’s video on YouTube "Easy method of modifying Myford Dixon quick change tool holders". The material is tough so doing several holders may be hard work.

Another alternative would be to remove the compound slide and substitute your own base with some gain in rigidity for heavy turning. Some have machined such a base using a 5” backplate casting (see post on this forum "Toolpost base for Myford cross slide". The compound slide is then reserved for turning tapers. You can machine the new base lower so the QCTP will accommodate 12mm tooling without further modification.

Edited By Andrew Moyes 1 on 13/08/2019 21:54:44

Edited By Andrew Moyes 1 on 13/08/2019 21:55:28