Small Lathe

[mikiek]

I have a Sherline arriving next week. I have to say their Customer Service is very responsive. Sent them an email with a few questions and got a reply within the hour. That raised a few more questions which I emailed back and those were answered in about 30 minutes.

[Matle]

The Sherline motor and controller units are good buys (at least were 10-15 years ago, when I bought mine). I am driving my watchmakers lathes and one milling machine with them.

 

Boley WW-style lathes are compatible with all 8 mm watchmakers lathe equipment. There may an issue with the thread on collets and in draw-bars. However, in recent years taps and dies for these rather special threads have become available again from model engineering suppliers, so that can be solved. You can also buy again collets and chucks originating in China at a reasonable price. They may be at the limit for high-precision watchmaking, but certainly are good enough for model engineering needs. Be aware, that the Chinese have decided to put a metric 7 mm thread on the spindle tooling of their watchmakers lathes, rather than the standard 6.85 mm x 40 t.p.i. thread. Howver, the Chines also make spindle tooling with the 'normal' thread.

 

If you are looking at a Boley D-bed lathe (the bed has 20 mm diameter with a flat on top) make sure to stay clear of the ones with 6.5 mm spindle bore. They have been rare at all times (never understood, why Boley and a few other manufacturers made them, considering that the same manufacturers also made 6 mm lathes, which became pretty much a standard together with the 8 mm lathes). Spindle tooling with 6.5 mm diameter is very difficult to find second-hand and virtually non-existent in the modern after-sales market.

 

Many thanks for this advice, it is clear I need to study more before making this investment. The Boley in question was indeed a D-bed. I'm not sure what the bore was, but the seller wasn't either so I stayed clear. Going to keep looking for either watchmakers lathe or one of the old Austrian unimats. I'm not in a rush, so I'd rather wait for a good opportunity.

[druxey]

Most Boleys are 8mm but a few older ones are 6mm, Matle.

[PAnderson]

I have an Emco Compact 8. It is a metal cutting lathe with threading built in. I really understand the need for a small lathe but being a machinist for almost 40 years I couldn't bring myself to by a tiny machine. This, to me is a perfect size but not something you can take on and off a table. Emco made some great machines and they made smaller ones too. They were made in the same fashion as the bigger industrial lathes. I would look around for this or the smaller Compact 5, which would be a pretty sweet machine. The pic attached is NOT my exact machine, just a pic of the one I have. I got a bunch of attachments, chucks, cutting tools for $600. Look around, well worth the investment

 

[Nirvana]

That's a nice lathe, and wow the prices for a used one...... really expensive!

But Austrian made you will get what you pay! Just like a Swiss watch these machines must be one of the top of the line machines.

[wefalck]

In any case, I would look for a lathe that can take collets directly. This so much more handy, safer, and precise than a three-jaw chuck for many of the small pieces we are working on.

[PAnderson]

My lathe has an MT #4 taper in the spindle nose. I have an ER40 collet adapter in it. I have a set of colllets from 1/8" to 1". That is what I am using at the moment. I can also put a ER11 adapter into the ER40 with collets from .010 to 1/4". I don't like a chuck for this kind of work either. But it can take a 3 jaw, 4 jaw and a face plate, which I have. The Emco's got caught between a hobby lathe and a real lathe. Too big for hobby use and laughed at by machinists for being too small. But in reality it is the perfect hobby lathe because there is not much you can't do with it. Emco still makes them as desktop CNC machines, but no more manual machines.

 

Paul

[Gaetan Bordeleau]

To make it short, there are 3 kinds of lathe small, tool room and industrial.

 

Small: watchmaker's lathe, easy to handle, max turning in 1 pass 0,001'' with micro moves to turn the handles. These lathe are made to turn small parts.

 

Toolroom: standard turning in 1 pass 0,01'' means 10 times faster  than the small one, not made to be move. Emco lathe is a perfect example. These lathe can as well turn small parts.

 

Personally I do not like to use a small lathe, too long to turn a part! I have a big lathe for precision work but my preferred one is the tool room which is the most versatile with accessories. The same thing would be possible with the big lathe but the price would be bigger too. I bought a used Myford  Super 7 from UK and had it ship by plane in Canada.

 

A small lathe can easily cost $1000. For the used Myford, I paid $900, the weight was about 225 pounds. I did a lot of tools with this lathe  and a milling machine. Usually everybody buy a lathe before a milling machine.

 

When you build metal tools, a milling machine  will be more useful than the lathe. 

 

Do you really need a milling machine for wood? The answer is easy and is No. The milling machine was created to mill metal not wood. But still there are few occasions where a milling machine can be useful like turning 6 sides in a  winch frame. These occasions are very limited. to make the buying of a milling machine profitable, we find other occasions but most of the these occasions, a wood tool will do it.

Edited December 12, 2015 by Gaetan Bordeleau

[wefalck]

I would like to have a toolroom lathe too, could think of some high-class manufacturers, but it is a question of space, when you are living in an appartment, there are limitations 

 

Most milling machines run too slow for good-quality wood milling. However, I have seen excellent work done with them on hardwoods. There are tiny high-speed mills, such as the PROXXON MF70, that can be used to good effect on wood. They would be some sort of micro-morticing machine and for miling-on flats, dividing work, and similar.

[tkay11]

This is an interesting point for me, Wefalk, as I'm trying to decide between a standard small mill such as a Sherline, and a Proxxon MF70.

 

I'm still a little puzzled by the speed effect. I've read about feed rates and the need to match mill diameter, number of flutes and rpm, and it seems that the smaller the mill bit, higher revs allow a higher feed rate.

 

So, for a 3mm mill bit, with 2 flutes, allowing a plunge depth of 3mm, 2000rpm allows a feed rate in hard woods of 6mm/15secs. Putting the rpm up to 12000 allows a feed rate of 36mm/15secs.

 

Conversely, with a 0.6mm mill bit, the feed rate goes down to 7.2mm/15secs at 12000rpm, but only 1.2mm/15sec at 2000rpm

 

My puzzle is whether, when using a lower speed mill, it makes any difference to the smoothness of the cut or level of burning if you just feed the wood at a slow rate. Is it that the only difference is the patience you need to feed the wood slowly, or is it that there are other disadvantages to milling wood with very small mill bits (e.g. 0.6mm, 1mm, 2mm)  at low rpm?

 

I've seen wonderful work with the MF70 in several scratch builds on this forum, but equally so with Sherlines and other standard small mills that only turn at up to 2200rpm.

 

Any comments or advice will be very appreciated!

 

Tony

[gjdale]

Sherline make a high speed pulley set for the mill (available as an accessory). Fitting it is a relatively simple job.

[tkay11]

Thanks, Grant. Good idea, and not very expensive. I'd still like to hear a reply about the problems of using low speeds with small cutters in wood.

 

Tony

[PAnderson]

Feed rates with small cutters do not directly correlate with bigger cutters. They are not as strong. A 3MM cutter with 4 flutes may only run at .001-.002 per flute while a larger cutter may run at .005-,010 per flute. In wood you also have to worry about the flutes packing with chips or dust at higher feed rates. Use all of the RPM's you are comfortable with but be very careful when it comes to feed rates. Also, harder woods and woods with a lot of resin will not cut as nicely. Trying things and seeing with your own eyes what works is the best way to run. If you are cutting metal, the above is even more important. Download a speed and feed app for your phone or computer and pay very close attention to the surface speed each material type is able to run at and start slow and work your way up. Keep in mind this is not production. You want a successful part not broken cutters or parts.

 

Paul

[tkay11]

Aaah! Lovely words of wisdom, Paul, and not the kind we get out of trawling the web.

 

Thanks a lot!

 

Interestingly, though, nobody's commenting on why some people say that using ordinary mills at low rpm is not as good when milling wood. Or is that not really a problem?

 

Tony

[PAnderson]

Wood needs RPM to get a good finish. Habit has shown me that using a cutter at low RPM's, the tendency is still to crank the feed handle fast. Impatience is the problem, maybe. And, unless your cutter is razor sharp, wood will just tear and splinter. This is why, in the day of carbide cutters, that high speed steel is a better option. It can be ground to a sharper edge than carbide. It may not last as long though. HSS can also be custom ground easier and to the correct geometry for cutting wood. Carbide, not so much. I use HSS in my lathe because I can hand grind the blanks easier and they can be redressed to a sharp edge with a fine stone. I use carbide exclusively for metal. Inserted cutters with inserts ground for aluminum, which are razor sharp. This seems to work the best in a small lathe where you are probably feeding the tool by hand versus power feed.

 

Paul

[tkay11]

Wow! Now that's the cream on the cake! Great and full answer, so thanks again, Paul! Now I feel I really do get it!

 

Tony

[NMBROOK]

Hi Tony,I totally agree with Paul,You need RPM to get a good finish on wood especially running small cutters.There is good reason why woodworking routers run up to 30,000 RPM and this is using cutters up to 25mm in diameter.

Incidentally fitting the high speed kit to the Sherline mill will void the warranty as I understand it.

 

Kind Regards

 

Nigel

[tkay11]

Thanks, Nigel. I looked up the parts for the higher speeds at http://www.sherline.com/4335pg.htm, and there's no mention of warranty void. In fact they seem to encourage it. The only statement is that the mod is designed only for the DC motors from 1993 onwards.

 

In the UK, Millhill supplies give a price of £78 for the pulley set alone at http://www.millhillsupplies.co.uk/catalogue/catalogue-sherline-accessories/.

 

Tony

[NMBROOK]

This may be a different kit Tony,it was Mark Taylor that told me the kit he was using voided the warranty.He may be able to shed a little light on this  

 

My personal opinion is that there isn't a one size fits all mill.For really small detail work with small cutters the MF70 is ideal.For larger work and metals,I would go for the Sherline or a larger Proxxon.I have seen the small yellow mill available from machine mart in the flesh and it looks like a decent bit of kit for the money if you want something.larger and slower  Might be worth investigating.

 

Kind Regards

 

Nigel

[tkay11]

That's interesting, Nigel. I was looking at the Sieg mills in Arc Eurotrade on line, but I now see that Machine Mart is in Edmonton, which is quite close to me. So I may well go and have a look.

 

I don't really intend to work with metal, but I've learnt from many other comments that once you enter this dark world of grown up toys you are easily sucked in deeper.

Tony

[mtaylor]

I'll expand on what Nigel said.  I have the (now discontinued) MM Micro Milling Machine.  Stock it turns maximum of 2500 rpm.  I snooped around the web and discovered the Sherline kit. At that time, there was a warning to monitor the bearings for temperature and also, that a "broken in machine" was best for the upgrade. 

 

I looked over my machine and figured it was doable.  Just needed to keep an eye on bearing temps and remachine the gears to fit. I did check with MM to see if they had different gears and was told that ANY modification voided the warranty. 

 

My warranty period was up, so I modified it.  Basically swapped the gears from motor to spindle and vice-versa.  Not that simple but the deed was done.  I can now crank out about +/-11,000 rpm.  I run a fairly slow feed rate anyway but the higher rpm provides a better finish.  Also, on some woods like cherry, I make multiple passes with a slower feed rate as they tend to splinter otherwise.

 

Routers need the high rpms as most are being used in some production work and the people using them are used to feeding wood through their saws, etc. a lot faster than what we might.

 

I hope this helps.

[PAnderson]

I'll expand on what Nigel said.  I have the (now discontinued) MM Micro Milling Machine.  Stock it turns maximum of 2500 rpm.  I snooped around the web and discovered the Sherline kit. At that time, there was a warning to monitor the bearings for temperature and also, that a "broken in machine" was best for the upgrade. 

 

I looked over my machine and figured it was doable.  Just needed to keep an eye on bearing temps and remachine the gears to fit. I did check with MM to see if they had different gears and was told that ANY modification voided the warranty. 

 

My warranty period was up, so I modified it.  Basically swapped the gears from motor to spindle and vice-versa.  Not that simple but the deed was done.  I can now crank out about +/-11,000 rpm.  I run a fairly slow feed rate anyway but the higher rpm provides a better finish.  Also, on some woods like cherry, I make multiple passes with a slower feed rate as they tend to splinter otherwise.

 

Routers need the high rpms as most are being used in some production work and the people using them are used to feeding wood through their saws, etc. a lot faster than what we might.

 

I hope this helps.

This is exactly what happens. Speeds and feeds were developed for production and all materials cut differently. Can you run a slower RPM and slower feed rate? Absolutely! Don't get wrapped up in the data that is there because most of it doesn't apply to us hobbyists. If you only have 2500 RPM, use it to your advantage and realize slower is better. It's not like we are talking minutes versus hours for any given cut but maybe only 2 minutes instead of one.

 

Mark is right, more cuts for finishing is the way to go. The important thing is to learn what YOUR machine can do and use it to it's potential.

 

Paul

[PAnderson]

Also, don't forget that some woods cut closer to metal than wood. Very dense wood can and will burn up a cutter before you realize it. Cutters are expensive and expendable. The idea is to make them last as long as possible.

 

Paul

[tkay11]

Great, sensible comments, Mark and Paul. I'm really grateful for your experience.

 

Tony

[Q A's Revenge]

I've cut softwood on my mill at its top speed of 2540 and it's doable with a slow feed but not ideal. There's a nice little Sieg X1 mill and clones out there that run at a speed of 100-5000 rpm which may be a better bet for those intending to cut a wide range of different materials.

[wefalck]

I gather the problem is that wood is elastic, so the cutting edge has to be fast to cut, rather than to push the wood sideways and rip it. This why one needs (in theory) a sharp cutter and high rpms. Slower feed rates mean that shorter and thus less elastic fibres can be cut (my theory). 

[tkay11]

Very interesting and a good idea, wefalck. It's really enjoyable reading thoughtful comments like that.

 

I'd also forgotten a discussion on this forum in 2013 (http://modelshipworld.com/index.php/topic/4200-milling-machine/), when Chuck chimed in (http://modelshipworld.com/index.php/topic/4200-milling-machine/?p=123846) saying, in relation to the Sherline he bought after a Microlux:

 

Do I need more power and more speed (RPM)???   I dont really know...but the 2500-2800 rpm on the Sherline seems to be more than enough. The finish and clean surface of the wood (boxwood and Swiss Pear) tells me that the the speed is just fine. I think its important to recognize what the proper feed speed of your work should be and not rush the operations...that will give you a problem.  Once again I am really abusing these machines.   They are being used 4 or 5 days a week for hours at a time.   My 17 year old son uses it with less care than I do...it has been holding up well and I literally make 20,000 blocks per month on it.  I cut wood anywhere from 1/16" thick to 3/16" thick...the larger sizes require multiple passes with the endmills....Before making a decision I recommend visiting a friends shop to sit and use theirs and discuss the pros and cons...you have to see and feel the machine at work.

 

It may be that a very sharp cutter as well as a well clamped and aligned mill bit can make up for a lack of speed. But then it may be that Chuck was using larger mill bits. I seem to remember he bought an extra special mill bit for the blocks.

 

This discussion continues to be interesting, and I wouldn't be surprised if more will be said!

 

Tony

Edited December 19, 2015 by tkay11

[Q A's Revenge]

I was using a 3/4" cutter in softwood on my mill at 2540, I doubt my smallest 1/16" bit would cut very well at that speed but I've not tried it.

[PAnderson]

By industry standards, all materials are cut using a base number called Surface feet per minute. Here is a comparison. Soft steel using HSS cutters are cut around 60-100 SFM. Let's say you are using a 1/4 inch cutter. The formula is SFM X 3.82 divided by the cutter diameter. So 100 SFM X 3.82 / .25 equals 1,528 RPM.

 

Wood on the other hand is much softer, let's say 500 SFM. So, 500 SFM X 3.82 / .25 equals 7,640 RPM. These are conservative numbers but you see where this is going. No hobby machine (nothing against hobby machines, LOL) will go this high.

 

Feedrate is RPM X feed per tooth X number of teeth. Above example: 7,640 X .002 X 4 flutes. equals 61 inches per minute. Granted, without a readout on your machine you will never know but 61 IPM is pretty fast.

 

This is also why you don't need carbide but carbide lasts 100 times longer if it is not abused. Carbide in wood is probably about 1500 SFM, guessing here. I would have to look it up. The above example would be almost 23,000 RPM. 23,000 X .002 X 4 flutes equals 183 IPM. You can't crank a handle that fast.

 

As your cutter gets smaller, your RPM approaches infinity. A 1/16 cutter would run at about 92,000 RPM and 740 IPM. Ain't gonna happen. Our machines at work won't even do this so we adjust accordingly.

 

I only use these examples because this is the industry standard in production shops and that is what people would try to attain for efficiency sakes.

 

Rather unimportant in our little shops but the point is you have to adjust your methods for your capabilities and because the given RPM can't be attained, your feed will be divided accordingly.

 

The other comments above are correct. It comes down do feel and getting to know your machine, your cutters and the kind of wood you are cutting. I imagine cutting Balsa would give you a heck of a time (too soft) while cutting Oak would be like cutting some soft steel.

 

Paul

[GuntherMT]

Wood on the other hand is much softer, let's say 500 SFM. So, 500 SFM X 3.82 / .25 equals 7,640 RPM. These are conservative numbers but you see where this is going. No hobby machine (nothing against hobby machines, LOL) will go this high.

 

Paul

 

Actually, Sherline sells a kit to allow their machines to run up to 10,000 rpm, and the Proxxon MF70 mill will go up to 20,000 rpm.