Another metal lathe decision

[lign]

Hi Folks,
Sorry to add another thread about metal lathes. I have spent many hours reading the many posts about metal lathes and it has tremendously helped me become informed about my choices. I currently have a micro metal lathe that lacks power feed. I'm trying to decide between the 7x16 MicroMark (for the length and ¾ HP hi-torque motor) and a 9x20 or 10x22 (Grizzly). It's not cost that is making me lean toward the 7x lathe.

I specifically want a metal lathe for triple lead threading. I've read many excellent posts on here, including Skiprat's wonderful tutorials on threading. Threading is 85% of what I expect to use it for, at least initially.

Hopefully some of you can address the following questions/issues. 1) Are gear changes easier on the 9x/10x for threading? From my in-person examination (with manuals in-hand) of a 7x10 and 9x20 at two local stores, I can't tell if gear changes are much easier on the 9x20 in spite of its "quick change" features. 2) MMark and LMS 7x lathes have variable speed and MUCH lower bottom end speed (50-60 RPM with no torque loss) versus 130-150RPM for the 9x/10x. I don't think a 9x or 10x variable speed is available in the U.S. 3) 7x lathes have cheaper and better ubiquity of bolt-on, no-modification accessories (cam-lock tailstock, Quick Change TP, milling attachments, DRO, etc) 4) Greater thread range on the 7x lathes (I know they do many more than spec'd – not sure if the 9x/10x can do more also).

I've even considered saving a while for a 12x36 gear head, but at some point I do a reality check and remember this behemoth is for pens. It seems that you have to go that large to get all the features of the 7x lathes.

 

[randyrls]

Hopefully some of you can address the following questions/issues. 1) Are gear changes easier on the 9x/10x for threading?

No; both are a PITA.

From my in-person examination (with manuals in-hand) of a 7x10 and 9x20 at two local stores, I can't tell if gear changes are much easier on the 9x20 in spite of its "quick change" features.

Both lathes require gear changes to change TPI.

2) MMark and LMS 7x lathes have variable speed and MUCH lower bottom end speed (50-60 RPM with no torque loss) versus 130-150RPM for the 9x/10x. I don't think a 9x or 10x variable speed is available in the U.S.

When starting to thread, a hand crank is a good idea to start with.

3) 7x lathes have cheaper and better ubiquity of bolt-on, no-modification accessories (cam-lock tailstock, Quick Change TP, milling attachments, DRO, etc) 4) Greater thread range on the 7x lathes (I know they do many more than spec'd – not sure if the 9x/10x can do more also).

The 9x20 can do many more threads that those listed on the plates, but so can the 7. If you get the 7X, make sure to get the longest bed you can afford.

Join the YAHOO 9x20Lathe and the 7x12minilathe groups. Lots of good information both places.

 

[holmqer]

I think Randy provided good answers to the questions, so I will make more broad observations.

Regarding the whole mechanical advance of the carraige for threading and turning.

For general turning, you will want the slowest advance of the carraige vs spindle your lathe can provide. The gearing of the Micromark mini-lathes results in 256 tpi IIRC. Every time you finish threading, you end up switching back to this gearing.

For threading pens, you will most likely have a small number of pitches you will end up using. You may settle on a 3 or 4 start 12 tpi for all your cap threads.

Under this scenario, you could make a jig that I saw somewhere, but can't find the plans for at the moment that essentially results in the 7x lathes being much quicker to change gearing on. You make a gear bracket assembly for your common pitches and leave the gears on. You then just swap this gear cartirdge rather then fool with all the messy adjustments. The last time I turned a 10 tpi thread, it took me several times longer fooling with the gears than actually cutting the thread. The gears are cheap enough that you could just make a few gear cartridges and leave them all populated.

The 7x lathes come with the ability to turn the leadscrew in either direction relative to the spindle or uncouple it from the spindle. The 9x lathes only have one direction or uncoupled. Since most threading is RH, the 9x is designed with this in mind which advances the carraige towards the headstock. An easy mistake to make when distracted is to fail to disengage the half nut on time, and end up driving the cutter into the chuck or a shoulder.

One can make a tumbler reverse mod for the 9x lathes that allows you to advance the carraige towards the tailstock instead, to give them the same capability as the 7x. When practical, I use this direction of advance on my 7x.

A good example of this is when I make a between center bushing. I chuck the stock, and turn the tenon, running the cutter off the piece as it advances toward the tailstock.

I hand crank the carraige back until the cutter rubs on the shoulder, advance the cutter 5 to 10 mills and engage the half nut over and over till I get to desired dimension. At any point, I can crank the carraige far enough away to test fit a tube over the tenon. Once the tenon is perfect, I reverse the piece and turn the large diameter and center drill. This way I never power feed towards a shoulder or chuck jaw. I may not be using the most efficient cutter orientation, and thus getting greater tool wear, but for the low volume of parts involved, that's OK.

The larger supply of 7x lathes in the home shop market does make parts and add-ons more available than th 9x, but the 9x design has been around for a long time, most modern 9x are clones of an old design and thus also has decent availability of parts and add ons.

 

[lign]

So to put this another way, if the 7x16 MicroMark was the same price as the 9x20 or 10x22, which would you buy if the only use was pens (i.e. small stuff)? At first, that sounds like a no-brainer, but think about it. Is it worth giving up the 7x16's variable speed, much lower bottom end speed, and reverse if capacity is not an issue? Is the bigger machine simply a nicer, better quality tool? (That makes a big difference and is the reason I own a Powermatic wood lathe.) I might some day want the extra capacity, but I kind of doubt it. The cost difference for the 7x16 vs the 9x20 is only $200-300, so for a long-term investment like this it's not the primary consideration.

 

[holmqer]

I personally have the 7x14 and have had no limitations with pen turning and making small fixtures for other turning. My woodlathe is a Nova DVR XP, and I have regular access to Oneway lathes.

The 7x14 has ample rigidity for the size stock that you would use to make anything pen related and just about anything you might want to make to support your more general turning. The 7x16 should be just as good or better with it's stronger motor.

I like the smaller size of the 7x14 and the 7x16 would be just as good in that regard. My 7x14 sits atop a tool cabinet. There would be ample room for the 7x16 on my tool cabinet.

If I felt that the 7x14/16 was not adequate, I would most likely skip the 9x and go strait to something much bigger that had the features I needed.

 

[lign]

It's funny you mention that because it's what I've started thinking the last few days. If the 7x16 won't do what I want, then I should go to a 12x24 or 12x36. The mid size lathes are a good compromise between cost and features, but I think they would really bother me with their feature limitations for my particular needs. I think I will most likely go with the 7x16.