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Lathe Rigidity Testing (determine upgrade benefits)

opensourcefan

opensourcefan

OSF
So... My little 8x16 isn't the stiffest machine around. It came with 10mm indexable tool holders. I've upgraded the tool post to an "A" type Multifix.

Possible plans to increase rigidity:

1. Remove the compound and fix tool post directly to the cross slide (with a solid riser block) until the compound is needed.

2. Increase the size of my cutter holders to 12x12, 16x16. Multifix holders will take 20mm.

3. Bed stiffness modification of some sort. Ya, crazy I know but there's gotta be some bridge building physics that can be applied somewhere.

However, all grandiose plans aside, do you guys have any techniques for testing rigidity in advance of doing all the work? I thought about physically clamping the compound down to see if it'll help at all. As well as temporarily bracing the bed.
 
@opensourcefan , for what its worth a couple of positive suggestion that help with machining. A lock on the carriage and the same for your compound slide when in use. My Busy Bee Craftex 10"x18" lathe came with a good carriage lock so I added a lock to the cross slide following Steve Jordan's style found in his video. Check them out here, good luck!


 
@opensourcefan I think you are doing all the right things. Here's a few thoughts:

If you make a solid tool post, the very next thing is the adjustment on the cross slide gibbs. If you can get them 'just snug' you will feel less vibration.

I think you won't get much better performance going to larger shank tools. It will improve, but not very much. I still do a fair amount of work with 1/4" and 3/8" HSS tooling... Better quality tools that are properly heat treated vibrate with less intensity. That's because properly heat treated tooling is stiffer, due to having higher tensile strength. You might consider getting a single 'best quality' tool in a size you can use, and compare.

"Dave M" on youtube has 2 of these small lathes in this category and he does great work with them. It is all too easy to be seduced by the 'bigger lathe syndrome' (boat owners call it twofootitis) A bigger lathe won't substitute for skill.

That being said, a lot of my turning is bigger than 2" in diameter, and having bigger lathes makes it easier to get good finishes and take bigger chips. I like my big machines, but for doing tiny work, they suck.
 
Dabbler said:
@opensourcefan You might consider getting a single 'best quality' tool in a size you can use, and compare.
Click to expand...
I second this. I have a cheap set of 1/2" shank insert tool holders and import inserts but decided to splurge on a decent tool holder. Drooped some change on a Micro100 SCLCR CCMT 1/2" shank holder and some Iskar inserts. I tried the import inserts in the new holder and the finish is slightly better. The new inserts in the old holders are also slightly better. The combination of the new tool and new inserts is quite remarkable.

Edited to add the tool shank size.
 
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Dabbler said:
@opensourcefan I think you are doing all the right things. Here's a few thoughts:

If you make a solid tool post, the very next thing is the adjustment on the cross slide gibbs. If you can get them 'just snug' you will feel less vibration.

I think you won't get much better performance going to larger shank tools. It will improve, but not very much. I still do a fair amount of work with 1/4" and 3/8" HSS tooling... Better quality tools that are properly heat treated vibrate with less intensity. That's because properly heat treated tooling is stiffer, due to having higher tensile strength. You might consider getting a single 'best quality' tool in a size you can use, and compare.

"Dave M" on youtube has 2 of these small lathes in this category and he does great work with them. It is all too easy to be seduced by the 'bigger lathe syndrome' (boat owners call it twofootitis) A bigger lathe won't substitute for skill.

That being said, a lot of my turning is bigger than 2" in diameter, and having bigger lathes makes it easier to get good finishes and take bigger chips. I like my big machines, but for doing tiny work, they suck.
Click to expand...

Yeah, if I do not stick out cheap 3/8 insert holders too far they are fine on a lathe with about 4x the mass. I have stuff up to 3/4 if I need it. For boring bars I managed to get 1 1/4 holder on AXA.

Generally machine struggles to take a cut on say more then 80 thou per side on mild steel bar 2" with feed say 0.004 running at around 500 - 600 rpm. These are standard positive inserts.

Generally on larger lathe its more of an issue with the cross slide setup (even on the smaller one sometimes) flexing then actual tooling flexing. I.e. on my big lathe with 1" tooling when going with heavy cut with negative insert I can see visually flex in the tool post to cross slide attachment (!) With interrupted cut its terrible - so have to take light passes.

I do most of my work on the small lathe - main issues are with say limited bore size on smaller lathe or needing to remove a lot of metal quick - luck of power.
 
On my little 10x22 lathe I believe most of the flex is in the compound and not so much in the tooling. However I really like my diamond tool holder and hss inserts on tool holders that normally take carbide inserts.
 
About four years ago I replaced the compound on my BB 10x18 with a solid toolpost. The solid post has an eccentric so I can snug the toolbit very close to centre, or far outboard.

I haven’t used the compound since.

Photos of various versions (including mine) are at

Solid Toolpost and Rear Toolpost​

 
@opensourcefan - I second what @Dabbler said.

But I'd be more emphatic about not bothering with trying to stiffen up the bed of your lathe. It will take HUGE changes for only very minor incremental improvements.

If you want you can add some weight to dampen vibrations but even that won't change the fact that you have a small lathe.

Overall, I'd suggest that you celebrate your small lathe for how great it is for small work and don't try and use it like a the big lathe it is not. For big stuff, just take small cuts. For hobbiests like us, there is no rush. The joy is in doing.

I know lots disagree with me, but I really do believe you will also love the way SHARP HSS cuts on a small lathe. I usually prefer it even on my 14x40.

Btw, Arthur Warner makes small indexable HSS inserts and tooling (including threading tools) so you can have the best of both worlds if you want it. Their bits are razor sharp right out of the box!

 
Solid tool post, tighten up your spindle bearings, sharp HSS tools for the win on small lathes. If you take a look at Tyrally's videos on YT with a Sherline and HSS tools you will be amazed.

I'm about to grind up some more 8mm diameter HSS for cutting some drill rod :-) on my 1022 lathe
 
David_R8 said:
I second this. I have a cheap set of insert tool holders and import inserts but decided to splurge on a decent tool holder. Drooped some change on a Micro100 SCLCR CCMT holder and some Iskar inserts. I tried the import inserts in the new holder and the finish is slightly better. The new inserts in the old holders are also slightly better. The combination of the new tool and new inserts is quite remarkable.
Click to expand...

You don't mention the size of the CCMT shank used?
 
Thanks for all the info fellas!

I already have the HSS inserts ready to go, they're shiny and sharp.
I'm going to add those compound lock screws cause that's super easy.
I will buy one high end holder and use it as my general go to and see how it is. Where's the best place to buy in Canada?, can't seem to find much north of the 49.
Before I mess with adding more locks though I need to consider a DRO first, will need to work around the scales.
 
opensourcefan said:
Thanks for all the info fellas!

I already have the HSS inserts ready to go, they're shiny and sharp.
I'm going to add those compound lock screws cause that's super easy.
I will buy one high end holder and use it as my general go to and see how it is. Where's the best place to buy in Canada?, can't seem to find much north of the 49.
Before I mess with adding more locks though I need to consider a DRO first, will need to work around the scales.
Click to expand...

Good stuff.

Doesn't your lathe already have locks?

FWIW, I've been holding off of putting a DRO on my lathe. I've used lathes for over 20 years without one and done just fine. I'm not sure the pain is worth it.

But I would put a DRO on my mill again in a heart beat!

I have a number of concerns on the lathe.

1. How to mount a scale on the cross-slide that won't interfere with the tailstock when I'm drilling.

2. How to mount a scale on the bed that won't interfere with a taper attachment.

3. The DRO I have on my mill has a lathe mode. The lathe mode has an automatic calculation for the compound angle setting. Very attractive. But the compound is small. How do I mount a scale on the compound without getting in my own way? I wish they made a teeny tiny scale for that.

Anyway, my point is really that I'd be focussing on my lathe technique and tooling before I worried about installing a DRO.

In my mind, my lathe priority is an upgraded VFD Ready motor so I can get speeds under 70rpm.

But who knows, after I put a DRO on my lathe I might wonder how I lived without it. Which is pretty much how I feel about the DRO on my mill.
 
@Susquatch

It's funny you say that because initially I didn't want one (and might not still) because I really wanted to just go manual. That is why I went through the trouble to make this an imperial machine. Maybe I'll just install a dial indicator stop for the time being.
 
Artisan Makes on Youtube has a 7 x 14 mini lathe. He did a video about a month ago on stiffening his headstock. Not sure if applicable to your 8 x 16, but his videos are quite well done:
 
opensourcefan said:
Where's the best place to buy in Canada?,
Click to expand...
I have a bunch of offshore tool holders, and a bunch of Kinnemetal, some Sandvik, and one or two Seco. I bought all my holders new, so my local Kinnemetal dealer. My first tool holder was a king's ransom, but now K tool holders are a lot more reasonably priced (than in 1980)

I'd try my local K dealer frist, then try online. You could also try ebay.ca, but you need to be sure what you are looking for, and (small) risk of getting fakes.
 
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opensourcefan said:
Maybe I'll just install a dial indicator stop for the time being.
Click to expand...

Now that particular improvement I totally endorse. It is on my list of projects. I've looked at a few different versions but I have not actually decided how I want to do it. As soon as I decide, it will become a priority project.

And while we are on that subject, I also want to make an adjustable one for the quill of my tailstock.
 
The Logan lathe I just sold I cut 4140 with a 1/2HP motor and carbide tooling. I used HS tooling where I needed custom cutters.

You need to learn how to grind your own HS tooling, master this and a lot of your problems diminish. Learn feeds and speeds that work best with your machine. Sometimes increase sometimes decrease, what ever gives the best cut and least vibration.
 
I would stay away from some more exotic ways to stiffen the lathe. I tried that with a mini mill and it was a waste. If your lathe after some minor changes is not stiff enough, just get a bigger machine.
 
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