Does anyone know what tolerance the Logan and the Craftsman lathes usually hold? Im trying to do a project that requires about +/- 0.001
You can make any lathe much more accurate. Rotating the compound slide to a 45 degree will make each turn 50% of the dial reading allowing you to take very accurate cuts. I will lock my main and rotate the compound when I have to hold very tight tolerance. Hope that idea helps you out. You can rotate further to take even smaller cuts, but it isn’t as easy to calc in your head as 50%.
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From: Michael Arnao via MakeICT Forum
Sent: Tuesday, October 4, 2022 6:52 AM
To: jeff@makeict.org
Subject: [MakeICT] [Metalshop] Lathe tolerance
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MichaelArnao MakeICT Member
October 4
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Does anyone know what tolerance the Logan and the Craftsman lathes usually hold? Im trying to do a project that requires about +/- 0.001
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So if you dropped it to a 9 degree cut it then becomes 10% and makes it way more accurate, and you just have to move the decimal place one place over?
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On Tue, Oct 4, 2022, 07:03 Jeff Eck via MakeICT Forum <noreply@talk.makeict.org> wrote:
| jeff MakeICT Member
October 4 |
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You can make any lathe much more accurate. Rotating the compound slide to a 45 degree will make each turn 50% of the dial reading allowing you to take very accurate cuts. I will lock my main and rotate the compound when I have to hold very tight tolerance. Hope that idea helps you out. You can rotate further to take even smaller cuts, but it isn’t as easy to calc in your head as 50%.
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| MichaelArnao MakeICT Member
October 4 |
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Does anyone know what tolerance the Logan and the Craftsman lathes usually hold? Im trying to do a project that requires about +/- 0.001
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Rotating the compound helps with better resolution but technique extends being that for working to right tolerances. Tool geometry can have a great effect, for example. It’s near impossible to take a thou off with most inexpensive carbide inserts. HSS or custom ground carbide can help though. Taking approximately the same doc on the last couple passes will allow you to get a better idea what the doc needs to be on the finish pass. The material matters too. For example, hrs can send up with an awful finish, so if I need to turn it, I will leave about a thou and make a couple light passes with a file.
Don’t confuse accuracy with precision. Terribly inaccurate parts can be made with great precision!
I’m assuming were talking .001 inches.
“It depends” is probably the most correct answer. Assuming a relatively experienced operator with the aid of a practice piece or two, appropriate tooling and measuring tools then I’d say relatively simple parts can be made with that kind of accuracy.
Hopefully you’re using relatively soft stock like aluminium or brass as that will make things easier.
If you need to drill a hole with that type of spec then you might run into some challenges.
that’s one of my problems, drilling a hole with a tighter tolerance. I noticed last time I tried drilling on the lathe, there was so much flex/deflection. I am curious what kind of tolerance is possible with that.
Hole tolerance of which type?
Location tolerance? Diameter? Taper? Roundness? Perpendicularity?
Bored? Reamed? Tapered?
The equipment, tools, materials, lubrication, and operator are all factors.
Repeatability needed? Or is it a single part? Is the starting stock something inexpensive that failures can be discarded?
Really it’s impossible to answer your question without knowing considerably more than the original post.
Making a round hole to a spec should never be done using a drill. All of the issues that Mike listed are characteristic of a drill. The one that shouldn’t happen on a lathe is location. A drill should self center in a lathe, but you should still start with a spot drill or a center drill. Otherwise, if a hole most be “to spec” it should be completed with a boring or reaming operation. Keep in mind that a reamer is not magical and can still create a bell mouthed or lobed hole.
I’ll also mention that if you are using the drills at makeict, many of those in the box are in need of grinding. Even brand new, because of the quality of the drills, many are so badly ground that they will never work. That’s one of the things I go over in my drill sharpening class. But the point is, you should make sure the drill you choose is capable of making a hole close to on size before using it.
If you want to meet at the space sometime let me know and I’ll see if I can help you diagnose the issue you have.
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