Production drilling in the lathe.

This is just a small word for anyone who may be considering making a batch of small components on the lathe, especially when it comes to drilling them.

In my experience it is better to clamp up the tailstock and drill the component from a fixed point, center drill and nominal size as follows, (excluding any reaming operations you may do).

Moving the tailstock to drill further and further into the bar makes the drill liable to wandering, and it's resulting effect is only apparent much later. So it is better to part off at the end of the hole and make a new hole again, don't continue with the previous one.

Any soft materials such as plastics cannot withstand high heat usually and if swarf binds up in the flutes it can leave a nasty surface finish (which pretty much cannot be remedied). so it is better to retract the drill frequently to keep it clear.

Also when parting off, the thinner HSS blades, although good, if too much of it is exposed from it's shank it will deflect and part off in a radial movement rather than a straight one.

Hope this may be useful to somebody.

Oh, and you might want to consider a ram-style tailstock, as you'll get really bored of winding the wheel. 

Michael W

Edited By Michael Walters on 29/06/2016 18:20:09

I agree with Michael; many years ago, i was making some steam pipes with six hole bolting flanges. I thought I could drill the holes in a piece of brass bar, then part off six pipe flanges. Wrong!! Only the first two were usable. The last of the batch was so bad that it looked as though it had been drilled free-hand. Lesson learned.

Maurice

Oddly enough my repetition lathe is worse for the drill wandering off centre than my manual centre lathe. That may be because the repetition lathe tailstock capstan isn't overly rigid.

The choice of tooling is really a matter of time. For some multiple parts it is quicker to make them on the manual lathe. For other parts it is quicker overall to take the time to set up the capstan unit on the manual lathe, or use the repetition lathe. At the moment I am making 6 off brass oilers for the eccentric straps on my traction engines. I am using the manual lathe, without capstan, as I judge this to be the quickest. That's partly because I'm screw cutting the 5/16" x 32 ME thread rather than using a die.

Andrew

Hows our Britan man doing?

I'm still Incredible Hulk Green whenever I think about him

sorry to go off a bit.

what is a repitition lathe?

Basically a commercial lathe for the repetative tasks of making batches of parts that are all the same, have a look at Andrews post about it and also look in his albums for some of teh batches of items produced

To save people the trouble of searching the forum this is the Britan repetition lathe, with annotations:

It's about the same footprint, possibly a bit shorter, as a Myford ML7. It is more versatile than a capstan lathe, but less capable than a cam auto lathe. A fuller description is in MEW issue 235.

I've used the lathe to make quite a number of parts for my traction engines, such as studs:

Nuts and lock nuts:

Hex head bolts:

And square head bolts:

Andrew

Edited By Andrew Johnston on 30/06/2016 11:45:21

I used to use one of these all the time, i love the tool carosel/quick change mechanism. Nothing quite like it for a compact machine, very fond of them still. 

Michael W

Edited By Michael Walters on 30/06/2016 11:55:02

Interesting; I find setting the tools for overhang and centre height a bit of a faff, ideally one would need three hands. But once set they seem to run fine, even with quite high DOC and feedrates. The exception is parting tools. I'm still having trouble with these. Unless the appropriate bolts are very tight the toolbit seems to move, albeit I have been cutting a lot of hex and square stock so the initial cuts are interrupted. There seems to be a delicate balance between feeding fast enough so the toolbit doesn't rub and feeding too fast so that one breaks the toolbit.

Any hints or advice?

Andrew

You could have prefaced this with the widely known fact that Twist Drills deviate and that should someone be using a Gun Drill that your advice may prove spurious?

Deviation is about the drill bit, not the tailstock (unless it's egregiously misaligned) and it is indeed good practice to face and re-centre between components where alignment is critical if using bits prone to deviation,

- Nick

It is true that twist bits are not the sturdiest of drills. But they are the most commonly used. The type of drills you are talking about will set you back a pretty penny, certainly not worth the cost for us.

The other thing is for absolute accuracy with guns, they are pulled through the lathe, not drilled forward, so it is a completely different procedure.

I also defy you to be able to lock up a tailstock, drill move forward and clamp up again in exactly the same spot each and every time. You will always be slightly off if you change the position. For most of us twist drills is about as good as it's going to get.

Michael W

I had a job that required accurate deep1/4" holes, I tried some solid carbide bits, followed up with a reamer, worth every penny.
I wouldn't want to pay for a full set though :-/

Any idea for a lever operated tailstock for ML7 other then original one, which one can buy for 150- 200 pounds on ebay.

It is easy enough to make an off-hand project of that but maybe something of particular merit is known for other members here.

I would be very greatful for any ideas regarding that item.

This hand wheel is really not good enough.

Have a look at Gadgetbuilder's site for his lever operated tailstock chuck
http://www.gadgetbuilder.com/DrillSharp.html#Lever_Drill

That may give you some ideas.

Dave
The Emerald Isle

That would be good but unfortunately a strike of tailstock longer than 1 inch is required.

Assemblies set on the rear of the barrel can give 3-4 inches of strike and something like that is what I would aim for.

Of course there is nothing particularly challenging in designing one of your own but may be some clever & tested designs, perhaps resembling Myford original are available around.

As well as the drilling issue Michael Walters also wrote :-

"Also when parting off, the thinner HSS blades, although good, if too much of it is exposed from it's shank it will deflect and part off in a radial movement rather than a straight one."

Beginners question : how much is too much?

Steve

Martin

There are drawings and a write up of an ML7 lever feed tailstock in MEW 16 page 30.

Dennis

Here I can help.

If lenght of blade can be adjusted, try to advance this blade from its holder only sufficiently to complete parting.

Anything up to 3/4 inch (including Hastelloy B3 bar, titanium Al6V4 and high tensile stainless from A4-80 bolts) can be parted off using ML7 lathe and RDG tools 3/32" blade with their holder and cut is square if care was taken to set blade square at the first place (bring it to your chuck...)

Part off blade should also be carefully sharpened as lack of symmetry on the business end will translate into conical cuts (or into broken blade).

First two materials were also parted off with the same blade at 1" diameter, but cuts were conical and facing was required. All with front tooling.

Stainless 316 at 2" diameter was parted off with home made blade, about 1/4 inch wide, with rear tooling. Former blade with front tooling also succided, but there was much struggle of blade and its operator.

Thinner blades, about 1/16 inch, work well on all common and many exotic materials at diameter below 1/2".

Anyway, after parting you still usually proceed with facing, unless your stuff is rather trivial.

Dennis R,

Thanks a lot.

Martin D, thanks for your reply.

Steve