Basic Myford practice

[ccfpcl]

Hi all

Just got my first 'proper' lathe (Super7) after years getting by with a Hobbymat. I'd like some advice from the experts please (I've tried all the usual books and several websites to no avail)

My question concerns how best to take (manual) traversing cuts. I now have 3 choices (leadscrew, saddle rack, topslide). I always used the leadscrew with the hobbymat, but it's now rather further away and so less convenient to use while watching the work.

One opinion I've had is 'always cut with the topslide'. The majority view (?) seems to be to cut with the leadscrew. The 'easiest' seems to be to use the saddle handle (particularly as mine has a nice vernier scale fitted).

Of these, I'm inclined to reject the saddle handle (reluctantly) unless I don't need an accurate endpoint (eg no shoulder), as there's nothing to stop the work pushing the saddle back with the halfnuts loose. You could lock the carriage each time with the locknut but this seems rather fiddly.

Presumably if you are to use the topslide the halfnuts must be engaged (otherwise we have the same problem as the saddle). In theory more precise than the leadscrew (10tpi plays 8 for the leadscrew, and less backlash on mine), and certainly lots of 'feel' however the leadscrew scale is much bigger and easier to set to the thou. Other problem with topslide of course is you have to ensure it's set parallel - another potential source of error. On mine, even when parallel the DTI 'wanders' when tracking with the topslide, but is rock steady with the saddle.

Further, people talk of setting the topslide over eg 6degrees to allow more accurate fine cuts, which seems like a good idea but obviously rules it out for general traversing cuts to a shoulder.

Leadscrew is fairly difficult to turn smoothly (I have a gearbox so there's lots of cogs to move) which seems to argue against it. However it wins on all other counts.

There must be an agreed 'right way' surely? Please do tell!

Many thanks, Chris.

[Richmond]

Hi,

"Leadscrew is fairly difficult to turn smoothly (I have a gearbox so there's lots of cogs to move) which seems to argue against it. However it wins on all other counts."

If you put the tumbler reverse into neutral ( and the gearbox too ) the saddle handwheel should turn very freely - mine does.

Topslide should only be used as a last resort, and yes lock the saddle.

6 degree setover is used when you want 1/10th thou cuts. At 6 deg. each 1 thou on topslide represents 1/10th of a thou.

In theory this should be 5.735 deg approx ;D But we are talking a 1% defference in 1/10th thou here, so is inconsequential.

My best advice is to cut under power ( gearbox fine feed ), and buy or make yourself a saddle stop.

rgds
Keith

[ravensworth2674]

I think that Keith and the many satisfied users of Myfords will agree that you may be using the wrong books!

Going over your remarks with a fine tooth comb, two points emerged. Keith spotted the saddle stop and the locking of the topslide. Both are amply covered in George Thomas's Model Engineers Workshop Manual and Jack Radford's one. I spotted the possibility of overhang which is again in GHT's tome.

I hope that these pointers will add immeasureably to your future enjoyment.

( Keith, Ken Metcalf's autostop- do you have the relevant ME, please?)

We are all on a learning curve

Cheers

Norman

[Tony K]

Agree with all the above.
For me, the most important reason to use the leadscrew, either manually or driven, is that it eliminates any error in the setting of the topslide.
Enjoy your new lathe.

[dickdastardly40]

Chris,

'Perfect practise' probably says to lock the saddle every time you stop and make a cut with the cross slide. I personally use the saddle hand wheel for most of the time and only use the wheel on the lead screw when milling. When roughing to size I hardly ever lock any slide. You can only use the half nuts to lock the saddle whan the tumble reverse is in neutral.

If unsure, try seeing if your perception of the work pushing the saddle back is actually happening. If there is little slop it shouldn't be the case. As most things it's horses for courses and ultimately you do what you prefer. As you have a gearbox, feed for your longditudinal cuts is straightforward. I feed up to just of the shoulder, knock the leadscrew off and come up to the shoulder on the compound.

Hope that this is of some help.

Al

[circlip]

Nip the saddle for cross cuts and taper turning using the topslide,
For long horizontal cuts - Saddle handwheel,or half nuts engaged,
Screwcutting - Saddle half nuts,
Milling - saddle half nuts engaged but tumbler disengaged.
Mine's a Maximat, but same operations. There is no expert or right way to do it Chris, Everyone has their own way, many roads to Rome and all that, YOU pick the most scenic for you. Regards Ian.

Alan, is it possible to update the Smilie library? I think we could do with one that shows a burning stick of Dynamite.

[ccfpcl]

Thank you all for your advice. Looks like there are as many approaches as there are lathe users.

I've ordered the 2 books recommended by Norman.

Keith: I investigated further and it's actually the saddle not the gearbox that makes the leadscrew harder to turn (it's easy with the halfnuts disengaged). Specifically it feels like it's the need for the rack to move the saddle handle that causes most resistance. The saddle glides smoothly using the saddle handle so it's not binding.

Al: Your approach and your comments suggest that my concerns over the saddle moving if not engaged with the leadscrew may be overstated. In particular your suggestion to knock the saddle out of engagement to stop the power feed, then finish up to the shoulder with the topslide (by implication with the power still driving the leadscrew, and thus the saddle free) means you're trusting that the saddle won't move in reaction to the cut.

Thanks again all, Chris.

[chris vine]

Hi Chris,

There is a position using the top lever on the myford gearbox which gives a very free neutral. In fact there may be two positions, between the engaged ones.

For turning the leadscrew by hand I always use this method.

Chris.

[dickdastardly40]

Apr 23, 2008 17:30:17 GMT ccfpcl said:

Thank you all for your advice. Looks like there are as many approaches as there are lathe users.

Al: Your approach and your comments suggest that my concerns over the saddle moving if not engaged with the leadscrew may be overstated. In particular your suggestion to knock the saddle out of engagement to stop the power feed, then finish up to the shoulder with the topslide (by implication with the power still driving the leadscrew, and thus the saddle free) means you're trusting that the saddle won't move in reaction to the cut.

Indeed I am trusting that the saddle won't move in reaction to the cut, I often have the leadscrew rotating even if I am not using feed or threading. Even if the saddle moves away from the shoulder slightly under backlash to the saddle rack, I am not going to 'drive' it away by coming to the shoulder with the compound. Due to using the compound any movement there might be is accounted for as the size of the job dictates how much I feed it in.

I am not trying to preach how it should be done, just explain how I do it, which gives me no detriment to final size.

As I said it's horses for courses and you do what you feel most comfortable with. My erstwhile experience is that I do as I've described. I do however lock the saddle whan facing and coming to tight tolerance sizes.

Again as I said, I suggest you see how much your saddle moves away from the headstock to see if your perception matches the actuallity. If there is movement always lock the saddle my some means most convenient.

Regards

Al

[Richmond]

Norman,

Best thing to do is use colin ushers site for the Model Engineer index utility and find the saddle stop from there : www.colinusher.info/Indexes/index.html

Alternativiely, someone has made an archive copy of Chris Heapy's site and has the plans for a multi-saddle stop :

kansai.anesth.or.jp/gijutu/kousaku/easyweb.easynet.co.uk/chrish/multstop.htm

Rgds
Keith

[ravensworth2674]

Thanks Keith but I was refering to the automatic stop which was development(?) of the one in Jack Radford's book. I have Colin Usher's and Chris Heapy's and Martin Cleeve's but clicking off is what I want. After all, the comic who had my S7B stripped part of the gears and went through the gearbox casing. Mind you, he also used mahogany dust in the gearbox. Well, that was what I found!

The mind boggles! Cheers and thanks

Norman

[Richmond]

Norman

If you find it, let me know pls. Would be intereseted in it as well. Someone has attempted a partial version on my lathe and I would like to get the full thing working too

Keith

[wayne]

You may want to try this to check your lead screw alignment

Turn the lead screw buy hand so the saddle half nuts engage straight away, with the carriage in the middle of the bed. If the lead screw moves in the horizontal plane, its not lined up correctly, also repeat at the gear box end and tailstock end. The lead screw should not move. This check is one that Myford themselves use, in addition they have a technique for bolting the gearbox, apron and lead screw bracket so everything is lined up correctly, this worked a treat on my Ml 7

Hope this helps Wayne

[ccfpcl]

Sorry Wayne not sure I follow your instructions - could you clarify for my slow brain please?

You said "Turn the lead screw buy hand so the saddle half nuts engage straight away, with the carriage in the middle of the bed. If the lead screw moves in the horizontal plane, its not lined up correctly, also repeat at the gear box end and tailstock end. The lead screw should not move"

Did you mean:
1) Engage the saddle with the leadscrew
2) Try to shake the screw axially to test for play in the mountings at each end (yes mine has a little)?

Thanks, Chris.

[ravensworth2674]

This opens a can of 'worms'
Movement of the saddle can arise from any number of causes.
The simplest is that the clasp nuts are not fully engaged. The second is because engagement cannot be achieved because they are clogged with grease/turnings etc. The third is that old enemy called wear. It can and does appear in all sorts of guises but going into a discussion on wear and its correction is not going to be achieved in 'a two liner here.'

regards

Norman

[wayne]

Norman who mentioned movement of the saddle moving?, however I do agree that the lead screw and half nuts should be clean

The test I am describing checks the lead screw is aliened horizontally (up and down movement of the lead screw) also no shaking, forcing, pushing or pulling of any part is required

Simply engage the half nuts on to the lead screw via the handle, the lead screw should not move either up or down in the horizontal plain at any point along the bed.

In reference to turning the lead screw by hand, this Is don only till the half nuts will engage. Then open and close the nuts without touching the lead screw or carriage position. If the lead screw is not aligned it will move every time the nuts are engaged and disengaged.

Also note that if Myford fit the gearbox they pin the lead screw bracket on the right of your lathe, has your bracket been pined

In addition it is a fairly easy task to reline everything if don the Myford way, and as I stated before this test is one of Myford tests after fitting a gearbox, lead screw and apron prior to pining the lead screw bracket (demonstrated to me by Myford fitters and subsequently used on my own lathe, which indicted my lead screw bracket was out, re alinged everything now amaised at how freely my lead screw turns by hand on a very early ML7 with MK1 Gearbox)

[ravensworth2674]

Wayne,
Do forgive me but I would re-iterate that I am talking of wear as well as alignment.
Years ago, I did up a S7B and then a ML7 which went to a MEW postbag and now I am doing up a ML7 and a S7B. What has to be remembered is that all ML7's are more than 30 years old and could be 52. In each of my efforts, I refered back to classical lathe overhaul considerations which I believe are pertinent.

Regards

Norman

[wayne]

As you say Norman MLs are long in the tooth as is mine 58 years old to be exact, my lead screw is now as free on my ml7 as it is on my connoisseur. what in my opinion can not be deigned the Myford fitters no loads of different tricks and knacks that are in no manual, after all, they are rebuilding all types of sevens every day. All i have offered is a non destructive or disruptive test for alignment that works, slight movement of the lead screw bracket will cause serious binding of the lead screw even in neutral as will miss alignment of the gear box, this is why for years Myford pin the bracket as its the most common to move.

[ravensworth2674]

It was not my plan to go off at a tangent but my experiences with Myford decades ago are more bitter than Wayne's. Consequently, I went back to first principles. Old Connelly is still readable, Schlesinger is there to test the best and point to the worst. Thomas, Radford, 'Cleeve', 'Tubal Cain' and the terrible twins of Duplex and the list increases.
Somewhere in the vast array, is 'me'. I can get ML7 to half a thou in 6" which isn't bad.
Frankly, playing about with lathes is a hobby. I have had other more challenging things in my 23 years of retirement!
Ravensworth2674 is but a small part of the World's largest charity!

[wayne]

I fail to see the point you are trying to make in your last thread Norman, Please by all means provide some solutions whitch will address the lads origonal problem of a stiff lead screw