Trying to size a first mill

[davidpbest]

135 deg drill bit will require 140 deg spoting drills which are available on Amazon but they are a LOT more expensive.

I think you're looking in the wrong place. Here are a few of 140° spotting drills I use:

5/16 x 140 degree Carbide Spotting Drill TiAlN MariTool

www.maritool.com

3/8 x 140 degree Carbide Spotting Drill TiAlN MariTool

www.maritool.com

1/2 x 140 degree Carbide Spotting Drill TiAlN MariTool

www.maritool.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Can't beat those prices for solid carbide. Hope this helps.

 

[Dabbler]

@krby the advice that has appeared above is really great! I started waaaay before the internet and advice like this. So I spent a LOT more on machines and tooling that I needed to.

No matter what you get, the important thing is to make chips. a lot of them. Your own experience is your best teacher. I have a friend with 13 lathes, for 3 watchmakers' lathes to several Taig and Sherline ones, up to a 24X40 VDF monster lathe. I've used most of them and loads of other lathes owned by my friends and employers.

Here's the crux of the matter: You can learn a lot on most any quality machine - but the Taig and Sherline machines will limit you to very small stuff, and make you dive into the you-have-to-make-accomodation-for-not-having-a-rigid-machine problem that you won't face (much) on a larger cast iron machine.

The minimum milling machine I recommend is the RF25 or RF30 style mini-mill. you can take a decent cut on those, even if you cannot do really big work on them. The practical work envelope on them is around 4" W 12" L and 5" H (when you take into account a vise and tooling) On a mill you can get away with something this small, but as @DavidR8 will attest, you can also grow out of them pretty quickly.

For lathes, this gets really tricky. You shouldn't buy a lathe by size, unless you *know* the size of the work you will be doing. Buy a machine that is at LEAST 475lbs. Why? because the rigidity of a lathe depends on the bed being rigid, and this includes 3 sets of ways which all have flex and play in them. There is a lot of leverage on the lathe bed, and the only remedy is a beefy bed. Some days I feel limited in what I am doing on a 3600lb 15X60" lathe. I've used a bunch of lathes, and your entry level lathe 'golden boy' is a South Bend (or clone) 9A. it is a 475 lb bench top 9X30 lathe that really can do good work - I used one, off and on, over a 30 year period.

- all the lathes that I have used in the smaller sizes, when cutting steel have taken a very long time, and it was very difficult to hold a consistent chip, and get a predictable and accurate result. A Taig lathe, for instance, is mostly limited to short parts in soft materials.

HOWEVER if you have a very specific interest, such as clock making or RC models, and you are using soft materials, you can go smaller than these recommendations. The problem is that it is much harder to learn on a less rigid machine.

I just don't want to see what happened to a curling friend of mine, to happen to you. He spent 1500$ on a 7X20 lathe and learned to hate machining, because it was too difficult to hold tolerance. I have a few friends that have that same lathe, and they have a LOT more patience for learning on a small machine than he had.

 

[davidpbest]

I'll second the vote for RF25 or RF30 to give yourself some upward expansion capability. Same with the 500 pound or bigger lathe.

 

[DavidR8]

I think the key in choosing machinery is having a reasonably good idea of the kind of work you want to do. For me, I make moto and bicycle bits, some tooling for my woodworking machines and parts for machines I make (CNC router and CNC plasma cutter) so my machines need not be large.
If I did work on car engine parts or long objects that would require bigger machines.

 

[Aukai]

Confucius says, that the machines you buy first will not be big enough.

 

[mikey]

I think the key in choosing machinery is having a reasonably good idea of the kind of work you want to do.

This really is the key to choosing a machine for the shop.

I live in a city and make parts for all the hobbies I have - cars, sport bikes, archery, fishing, photography, lawn equipment restoration and others. I used a Sherline lathe and mill to make everything I needed for these activities and while there were a few times when I had to push the envelope, I was just fine for over 20 years with just these little machines. Did a lot of work for other car/bike/archery/fishing buddies, too, and had no problems making do with my machines. I learned almost everything I know about machining from my Sherline machines.

I only stepped up to a larger lathe because my dream lathe turned up on my local CL and my RF-31 dropped in lap for free from my neighbor. If not for these events I would very likely still be happy working with my Sherline tools.

I don't disagree that bigger machines allow you to do bigger stuff but not everybody does bigger stuff. I also don't disagree that you can make small parts on a big machine but you cannot make big parts on a small machine, but it is also true that making small parts on a small machine is often easier, faster and more accurate. I would posit that the vast majority of work done on bigger machines would easily fit on much smaller ones if they are sufficiently rigid/powerful/fast enough, and that the occasional larger part that takes advantage of the machine's capacity is an infrequent occurrence. If this is so, and it is, then you are spending more money on a potential capacity that isn't used that often, along with accessories that cost a lot more as the machines get bigger. Plus, you need more space and power to use this stuff.

We encourage our new guys to get the biggest machine they can fit/find/afford all the time. In a job shop, this is good advice. In a hobby shop, sizing the machine to suit the majority of the work the user will do makes more sense to me.

 

[Radical]

Hi Everyone, This is my first post.

I'm building a small home shop with the goal of being able to prototype ideas mostly within the shop. I've recently bought some equipment and made some mistakes and observations, so I'm hoping while the lessons are fresh in my mind, I can help someone ask the right questions and be happy with what they buy.

Before I got into software development 30 years ago, I was a Precision Sheet Metal Mechanic for about 6 1/2 years, and spent a good deal of that time programming CNC punch presses, and planning out production for most parts and assemblies that came through the shop. The rest of the time, I was making parts! I did spend some time on manual mills and a lathe, but not a whole lot. So I'm kind of a newbie on those.

Although there are some tools you can skimp on, I agree with everyone on here recommending to buy quality over quantity.
You're going to use these tools and machines for many years, so every time you use one of them, you'll either be glad you bought quality, or wish you had bought quality, even if it meant delaying the purchases, or delaying purchase of something else.

I have an LMS 3990 mini-mill from a project my Dad and I did a few years ago, and about a year and a half ago, I bought an LMS 7350 mini-lathe to match. I bought the mini-lathe because without overanalyzing it, I expected the capabilities of the mini-lathe to match those of the mini-mill.
I was wrong (and I should've done my homework a little better).
As soon as I opened the crate, I thought Wow! This machine is tiny! I immediately wished I had bought a bigger machine and maybe skipped buying tools that could've waited.
For me, it seems having the next size up on the lathe is more important than upsizing the mini-mill.

I'm agreeing that within reason and mostly within budget, buying the machine you really think is best for you is worth the extra cost. I'm not suggesting to always buy the bigger machine, because there are other considerations: space, power requirements (I don't have access to 220V), anticipated possible uses (estimate on the big side), if you move a lot, and of course cost, but if you can, get the right machine first, or at minimum consider how much extra it'll cost, and if you'd be better off delaying purchase of something else so you can start with the right base machine.

I like the LMS 7350 mini-lathe. It seems like one of the best in its class, but I know that in the future I'll be upsizing, and I wish I had bought the right size the first time. That size may be fine for your needs. Mini-lathes are great for the right projects, but there is better rigidity in the bigger lathes, not only in the base, but in the cross slide, etc...

I'm planning on buying or converting a mill to CNC in the coming months and will most likely upgrade the mill too.
After looking at costs of prebuilt CNC machines, I believe I'm going to end up with better bang for the buck by converting a machine myself.
I can convert my mini-mill to CNC, but I feel that in the long run, I really want a larger machine, and to be able to make faster cuts than the 3990 supports.

My immediate gauge of size is that one of the parts I'd like to make for my motorcycles is roughly 6" x 6", and with the mini-mill, I'd have to mill one half, then flip the part around and re-align, then mill the other half. I'll make other things with CNC, but that's kind of my indicator.

So, to eventually have the capacity I want in a CNC mill, if I convert my 3990, then upgrade to a bigger machine later, I'll be able to reuse the motors and the electronics/software, but the cost of the conversion kit/ballscrews for the mini-mill would mostly be lost when I sell it.

So, if I can swing it, I'm thinking in the long run it'll be better to upgrade to a larger mill first, then convert the new mill to CNC.

I'm looking at the Grizzly G0704, the PM-25MV, the LMS 6500, or (what I really want) the PM-728V.

I've read every article I could find, and watched a ton of videos comparing the machines, and the information conflicts. Mostly everyone likes the quality of the PM over Grizzly, say good things about the LMS 6500, but don't really say where it stands in terms of rigidity compared to the other 2. On one site a guy who has both says that despite the lower weight and how the column mounts to the base, the G0704 is more rigid than the PM-25 and better for CNC conversion and cutting steel.
The 6500 is interesting because it's the only one of the 3 that has a fixed column, and I'd love to know if that makes it more rigid than the Grizzly or PM-25.

It seems either of the first 3 machines are going to make a good CNC conversion, but it would be nice to know what's the best machine and why.

Then there's the PM-728VT. This machine is about 100 lbs heavier than the PM-25, and about $1200 more expensive. It runs on 120V, has an OEM CNC ballscrew conversion kit, spindle speed kit, and DRO available for purchase directly from PM, plus it has a lot of great features, and a 5 year warranty. It seems to be the best machine in this class from what I can find. To convert it to CNC would require the OEM CNC Ballscrew kit and Speed control from PM, plus motors, electronics, and software from elsewhere. I believe this would be a very capable, rigid machine, but with all of the options it costs more than I'd like to spend right now. I'd love to hear what you guys think of this machine, good or bad.

With the 4 machines I'm considering, one of things steering me toward the Precision Matthews machines is that they have 36 month financing.

To favor quality over quantity, while staying sort of within budget, I'm considering picking up the PM-728VT with the deluxe CNC Ballscrew conversion kit, and speed control, and probably skip the DRO for now, then finance it over 36 months if I can get a decent interest rate.
It'll be a quality base that I can build on, that I believe will suit my needs for a very long time almost no matter what I want to build.

I can then sell my 3990 mini-mill to cover a good portion of the electronics and motors to finish the CNC conversion.

As budget permits and possibly not until I pay off the machine, I'll buy the DRO and other upgrades.

Doing it this way, I end up with the right machine from the get go, or, err, second go, and won't lose money upgrading the 3990 that I plan to replace anyway.
I may also decide that the PM-25/G0704/6500 is really the right size or you might too, or might decide a small Sherline is best.
I'm simply suggesting that if you can, buy the machine you want/need on the first go, and favor quality over quantity. It'll be cheaper and more enjoyable in the long run.

Have a great day!
Radical

 

[addertooth]

You will likely be quite happy with the PM728-vt. I have one, so I may be biased.
If you are limited to 110v power, take a peek at the PM-1228VF-LB lathe.

​

 

[Dabbler]

@Radical I like your reasoning...

In this hobby I started with a 12X37 weighing 750 lbs, and built a stand for it. I'm still using it occasionally. I upgraded to a 14 X 40 with a D1-4 spindle (1700 lbs), but it was a basket case, and I have yet to make chips with it. I then lucked into a 15X60 lathe weighing twice what the other two lathes put together. My mill progression has been similar, but that's another story...

Since you are changing the lead screws to ball screws for CNC, let me further complicate your reasoning If you have the luxury of time (you have working machines, after all) see if you can find a used PM728. If Matt knows you are going to do the upgrade with his kit, he may be able to help you find one, or search Craigslist or Kijiji. You might just end up with something in your price range that is better that new...

 

[Aaron_W]

Interesting, my experience has been the opposite, I found small mills to be more limited than small lathes. I guess much depends on the projects and the specific machine.