If you have ever wondered why some machinists insist on working “between centers” for critical jobs, you have found the right answer. Most online lists give you a few cryptic bullet points. This guide gives you the full, practical knowledge that separates precision work from guesswork.
What “Between Centers” Actually Means
Working between centers means your workpiece is supported at both ends by the lathe’s centers:
- Headstock center (driven by the lathe spindle, usually with a “dog” or driving carrier)
- Tailstock center (free-spinning or rotating, providing support)
The workpiece has center holes drilled at both ends. That’s it. No chuck. No collet. Just two precisely aligned points.
The core principle that nobody explains: When you work between centers, the workpiece’s rotation axis is defined entirely by your center holes. The lathe spindle only provides rotation power through a dog. This decouples part accuracy from the chuck’s runout.
✅ The Real Advantages (Expanded & Explained)
The original source listed five advantages. Here is what they actually mean in a real workshop:
1. Remove and Reinstall Parts Without Losing Concentricity
What this means for you: You can take a partially machined part out of the lathe, inspect it, measure it, or even take it to another machine, then put it back between the same centers. The part will run true to within 0.0005″ – no re-indication needed.
Practical example: You are making a precision shaft. You turn the first diameter, then need to check a fit with a mating part. Remove the shaft, test the fit, return it to the lathe between centers. Resume machining. The second diameter will be perfectly concentric with the first.
The hidden workflow benefit: This enables batch inspection mid-process. Machine five parts halfway, inspect all five, then finish them. No setup time penalty.
2. Transfer Work Between Different Machines
What this means for you: A shaft machined between centers on a lathe can be moved to a cylindrical grinder (also using centers) without losing concentricity. The center holes become your universal datum.
Real-world application: Rough turn a shaft on a heavy-duty lathe. Send it to heat treatment (center holes protected by plugs). Finish grind on a precision grinder. The final part runs true because every operation referenced the same center holes.
What the original article meant by “without defeat of concentricity” – “Defeat” is a typo. It should read “without loss of concentricity.” This is the single biggest advantage: centers create a permanent, repeatable datum.
3. Reverse the Part Without Losing Alignment
What this means for you: Need to machine both ends of a long shaft? Work between centers, machine one end, then simply flip the part end-for-end. The center holes ensure the second end is perfectly aligned with the first.
The pro technique: When you reverse a part, the headstock center now goes into what was the tailstock center hole. Because both center holes were drilled in the same setup (or using a center drill in the tailstock), they are perfectly coaxial.
Comparison to chuck method: In a chuck, reversing a part requires re-indicating the runout. It takes 5-10 minutes and still may not be perfect. Between centers, it takes 30 seconds and is automatically perfect.
4. Machine the Full Length of Your Lathe Bed
What this means for you: A part held between centers can be as long as the distance from your headstock spindle nose to your tailstock ram’s maximum extension. That is typically the full rated center distance of your lathe.
Practical example: You have a lathe with 40″ between centers. You can turn a 40″ long shaft between centers. In a chuck, that same shaft would have 6-8″ inside the chuck jaws, so only 32-34″ would extend out – and it would vibrate badly.
The stiffness advantage (contrary to the disadvantage list): A long part between centers with a steady rest is actually more rigid than a chuck-held part of the same length. The steady rest supports the middle, and both ends are constrained.
5. Ease of Workpiece Setup
What this means for you: Setting up a part between centers is brutally simple:
- Drill center holes (30 seconds with a center drill in the tailstock).
- Install a drive dog on one end.
- Mount between centers.
- Tighten the tailstock.
- Go.
The time comparison:
- Chuck setup (round stock): 1-2 minutes, but runout of 0.002-0.005″ is typical.
- 4-jaw chuck indicating: 5-10 minutes for 0.001″ runout.
- Between centers: 1 minute for 0.0005″ runout.
The unspoken truth: For precision work, centers are actually faster than indicating a 4-jaw chuck.
❌ The Real Disadvantages (Expanded & Explained)
The original source listed five disadvantages. Here is the complete, honest assessment:
1. Limited Cutting Speed Unless Using a Live Center
What this means for you: A dead center (solid steel, no bearings) in the tailstock cannot handle high speeds. Friction generates heat, which can burn the center hole and seize the part.
The solution (and what the original missed): Use a live center (rotating center with bearings). Modern live centers handle 3000-5000 RPM easily. The disadvantage becomes irrelevant if you spend $50-150 on a quality live center.
Pro tip: For heavy cuts, use a carbide-tipped dead center with high-pressure lubrication. For general work, buy a live center. Problem solved.
2. Center Holes Must Be Drilled Before Starting
What this means for you: Every part requires an extra operation: drilling center holes. For very short parts (under 2″ long), this may not be worth it.
The workaround (pro secret): For soft materials (aluminum, brass, mild steel), you can use a center drill in the tailstock to drill the hole while the part is already between centers. Center the part roughly, drill one end, flip, drill the other end. No separate setup.
When it’s a real problem: Production runs of 100+ short parts. The extra drilling operation adds real time. In this case, a collet chuck or soft jaws may be faster.
3. Limited Operations on the Bar End
What this means for you: The end of the part held by the headstock center is occupied by the center hole and the drive dog. You cannot machine that face or drill deeply into that end without re-mounting.
The clarification: The original said “Just allowable can be execute on the end of bar” – this is garbled. It means “Only limited work can be done on the end of the bar.” Specifically, you cannot face off the center hole completely or bore a deep hole from that end.
The solution: If you need both ends fully machined, work between centers, machine one end completely (including facing off the center hole), then reverse the part. The second end’s center hole is still intact. Face it off last.
4. Cannot Perform Boring Operations
What this means for you: Boring requires holding the workpiece in a chuck or fixture while a boring bar enters from the end. Between centers, the tailstock center blocks access to the part’s bore.
Is this always true? Yes for through-boring. But for internal tapers (like a Morse taper socket), you can mount the workpiece between centers and use a taper attachment to bore from the tailstock end – if you remove the tailstock center and support the boring bar externally. It’s awkward but possible.
The honest answer: For boring, use a chuck or a faceplate. Between centers is for external turning only.
5. Lack of Stiffness (The Myth vs. Reality)
What this means for you: A thin, long part between centers can deflect under heavy cutting forces because it is only supported at the ends.
The nuance that most sources miss: Stiffness depends entirely on the length-to-diameter ratio:
- L/D less than 4:1 – Between centers is very rigid.
- L/D between 4:1 and 8:1 – Use a steady rest for support.
- L/D greater than 8:1 – Use a follower rest or switch to a chuck with a spider.
The comparison to chuck holding: A part held in a chuck with 4″ of stick-out has a cantilever – it acts like a diving board. A part between centers has both ends supported – it acts like a bridge. For the same L/D ratio, centers are stiffer until the part becomes very slender.
The original’s “lack of stiffness” warning applies only to: Very long, thin parts (L/D > 10:1) without a steady rest. Add a steady rest, and this disadvantage disappears.
📊 Between Centers vs. Other Methods: Which Wins?
| Criteria | Between Centers | 3-Jaw Chuck | 4-Jaw Chuck | Collet Chuck |
|---|---|---|---|---|
| Concentricity | ±0.0005″ | ±0.003″ | ±0.001″ (indicated) | ±0.001″ |
| Max part length | Full bed length | ~80% of bed | ~80% of bed | ~70% of bed |
| Setup time | 1-2 min | 30 sec | 5-10 min | 1 min |
| Remount repeatability | Perfect | Poor | Fair | Good |
| Boring capability | No | Yes | Yes | Limited |
| Cost (tooling) | $50-200 | Included | Included | $200-1000 |
The bottom line: For shafts, long parts, and any job requiring remounting or transfer between machines, centers are unbeatable. For short parts, boring jobs, or high-volume production, chucks or collets may be better.
🔧 Pro-Level Knowledge: The 3 Center Work Hacks
Hack #1: The “Combination Center” for Facing
Need to face the end of a part that has a center hole? Use a half-center (a center with one side ground flat). The flat allows a facing tool to cut across the end without hitting the center. These are commercially available or you can grind your own from a dead center.
Hack #2: Protecting Center Holes During Heat Treatment
Pack the center holes with clay or screw in center hole plugs (tapered steel plugs). This prevents scale formation and distortion. After heat treatment, the center holes need only light cleaning, not re-drilling.
Hack #3: The “Floating Center” for Misalignment
If you are working between centers but suspect your tailstock is slightly misaligned, use a floating center in the tailstock. It has internal radial compliance (rubber or spring elements) that allow it to self-center. This is a $200 tool that saves hours of tailstock alignment.
Also Read : Lathe Taper Turning Attachments: The Ultimate Guide to Precision Angled Cuts
Final Verdict: When to Use Between Centers
Use between centers when:
- The part is long (over 12″ or more than 3x the diameter)
- Concentricity matters (within 0.001″)
- You need to remove and re-mount the part
- The part will go to a grinder after turning
- You are making multiple identical shafts
Skip between centers when:
- The part is very short (under 2″ or L/D < 2:1)
- You need to bore or drill deeply into the end
- You are doing high-volume production (over 50 parts)
- The material is too soft to hold a center hole (e.g., pure copper – use a padded center)
The smart machinist’s rule: When in doubt about concentricity, work between centers. The extra minute to drill center holes is nothing compared to the hours saved avoiding scrap from runout.
Quick Reference: Center Types & Their Best Use
| Center Type | Best For | Max Speed | Cost |
|---|---|---|---|
| Dead center (HSS) | Low-speed roughing | 500 RPM | $10-20 |
| Dead center (carbide tipped) | Heavy cuts, high heat | 1000 RPM | $30-50 |
| Live center (standard) | General turning | 3000 RPM | $40-100 |
| Live center (heavy-duty) | Production, high speeds | 5000+ RPM | $150-300 |
| Half-center | Facing operations | Same as base type | $25-60 |
Pro tip: Buy a good quality live center (brands like Riten, Rohm, or Bison). The cheap $20 live centers have excessive runout (0.002-0.005″) that defeats the purpose of working between centers.
