Workshop Machinery and Techniques

[Magnetoman]

Allright, even clever people on here won´t tell me what´s so clever setting the top slide at any angle for all year long.

If for some odd reason I had a DRO connected to the compound rather than to the cross slide there would be a reason to always have the compound aligned parallel to the cross slide, but that would defeat the usefulness of having a compound.

Since most of the time the angle makes no practical difference, my compound sits at whatever angle I last set it at until I need to reset it to a different angle for some practical reason, like threading, then it sits at that angle until I have some practical reason to move it to another angle. I don't leave the compound at some setting for a clever reason, I leave it there because there's no reason not to leave it there. The angle has nothing to do with a DRO or quick change tooling holders.

 

[Vincent Brake]

top silde is always at 0,00 paralell to main slide.
and if threadding with HSS than
depth say 0,1mm each cut and top slide at 0,05 further.
following.
30-60-90 degree triangle.

but with carbide tips it doesnt matter at all, only a to low cutting speed when on conventional lathe...

 

[Cyborg]

top silde is always at 0,00 paralell to main slide.
and if threadding with HSS than
depth say 0,1mm each cut and top slide at 0,05 further.
following.
30-60-90 degree triangle.

but with carbide tips it doesnt matter at all, only a to low cutting speed when on conventional lathe...

Again, I don’t have any formal training, but it is my understanding that most people on this side of the world are taught (during their apprenticeship) to use 29.5 or 30 degrees to reduce load on the cutting tool and prevent chatter. Not necessary on your lathe, but certainly helps with my clapped out South Bend 9A. I don’t understand what you mean by 30-60-90. Could you or Vic give me a link to a continental thread cutting video? Hopefully before this thread gets locked.
I still think this forum should have its own dedicated Tool & Machinery “section”. It could/should be of interest to those that don’t have lathes or make their own tools. Then when you take your Vincent part to the machinist, you have a better understanding of what’s going on? Know what to ask for… what questions to ask… know when you’re getting screwed?

example….

 

[Vincent Brake]

with old syle HSS chisels: the idea is to cut thread only with the left side of the cissel, as the right hand side has a negative ship corner.
so one feeds in and than simultaniously a bit to the left side, keeping the chisel just clear from the right side thread flank, thats why the triangle trick for.

note Mr Bananaman will have to do the trick with 27,5-62.5-90 degree trigangle.

cheers?
or wine?

 

[oexing]

As said, I never bothered about setting top slide to 30 degreers for thread cutting. Just use the cross sllide and have each cutting depth at 0.10-0.20 mm , not much slower than in the video clip above. So why care for disturbing the top slide at all. With HSS tools I like some minimal rake like 5 degrees for easier chip forming conditions, not more as you´d get incorrect flanks in the thread. Yes, with no lateral motions of lathe tool while thread cutting you´ll see two chips forming, on both sides of the tip - isn´t a factor, just keep lubrication plentiful.
Having the top slide at a bigger angle like 45 degrees all year long I see an unsafe condition when roughing bigger bores: You never know if the tool holder walks into the positive direction of top slide or not, by some vibration or other forces. If it does walk , you´d get a deeper bore hole bottom and a smaller inner diameter than expected. Not so with parallel top slide: You always have frontal force on the tool tip , no deviation from any angle effects , so a more predictable size , especially in combination with DRO and calibrated tool holders. So no desire for me to set top slide at angle for most of the time, unless I´d have to do a real deep and coarse locomotive thread - or due to some clearance troubles from the top slide handle and tailstock.

Vic

 

[Monkeypants]

It seems that when I set the top slide at 90 degrees (parallel to the ways) I frequently run into that clearance trouble with the tailstock. Plus often I need the extra travel in the Y axis with the 9” lathe. I do understand what you are saying. I keep the gib snug (maybe I should install a lock?) and keep the backlash taken up. Instead of buying a second (old) lathe, I should have sold the little one and bought one newer decent sized one.

Anyway… back on topic. Shoes turned…. on to painting.
View attachment 47678

Those old machines were skookum. Perhaps your McDougall has had a hard life.
I find the old Monarch to be a far better lathe than I am machinist!
Still finding cool features on it.
The reversing lead screw and autostops make threading very easy and fast.
I haven't seen any modern lathe with this feature, perhaps the cost is too high today?
Some very clever lathe designer came up with the single tooth dog clutch for the leadscrew.
Monarch used it on their toolroom models as did Hendy, another very heavily built American machine.

Glen

 

[litnman]

On my old Craftsman the dials are very small and hard to read. I use the tool post grinder chart to set the compound. The more degrees it's rotated
the finer the adjustment can be.
My first lathe was a Monarch

 

[Cyborg]

The McDougall had a hard life, but I knew that going in. I was looking for something cheap that had the ability to remove metal in a hurry. Then finishing (in most cases) could be done on the small lathe. It has several issues, most of which can be addressed. I just decided to use it as is and then decide if it makes sense to sort it out…. assuming I can live with the wear in the ways. No regrets as far as what I paid etc, just thinking I should have dipped into the kids inheritance and gone for broke.

 

[oexing]

In case the dials on the old lathe are unsatisfying I would spend a few hours and get new nice scales with graduation suitable to the thread on the machine. 0 - 100 per revolution could be metric or your choice of imperial units. Certainly a DRO upgrade would be best, a few hundred €€ gets you the counter plus glass scales. On small lathes typical glass scales may be less desirable due to size. Magnetic bands and sensors a better option then.

Vic
lathe scale rings:
lathe scale rings

magnetic linear encoder plus mag. tape

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[Cyborg]

Thanks,
I didn’t know those scale rings were sold like that. Mine are “ok”… nothing a pair of reading glasses and some light can’t fix, but it would be nice to have a larger one on that dreaded top slide on the big lathe. I have DRO on the mill which I installed shortly after inheriting it. I’d go absolutely insane without it. It is a Mitutoyo, but only X and Y, so I added another to the quill. I haven’t really felt the urge to add one to the lathe, although I know it will make life easier. Even if it’s just pushing a button to zero instead of try to figure out what I did with that little screwdriver. Actually there isn’t a good excuse for not having one on the lathe. They are so inexpensive now… at least for the Chinese ones.