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View Full Version : Cutting Bolts in the lathe.



Boucher
02-23-2013, 01:13 PM
How do you hold bolts and screws to modify or part to length in the lathe?
For most small ones I generally cut them with an abrasive disc on the dremel and finish on the belt sander.
For larger bolts I generally hold them in a coupling nut or similar and machine on the back side to tighten the threads. Cutting off to length gets to be a little more difficult so I was curious how others do it?
Would a split nut held in the chuck have enough grip to hold the part from turning if parted from the front?

Jaakko Fagerlund
02-23-2013, 01:22 PM
Split nut is one option, though for modifications I use a cutoff machine. It has a small V-jaw that has holds the bolts/pins/etc. while cutting. Another option is a block with different thicknesses and threaded holes tapped in to the steps, just run your bolt in and cutoff from the other side of the step.

Tony Ennis
02-23-2013, 01:27 PM
Hacksaw. No, really. If I had to do a lot, I'd find a better way.

Black_Moons
02-23-2013, 01:38 PM
The only use for a 3 jaw chuck: holding hex heads on bolts securly.

Ron of Va
02-23-2013, 03:33 PM
My favorite way is to use a 5C collet and a hexagonal collet block in a 3 or 6 jaw.

I have also used a coupling with a jam nut.

(Sometimes I use a hacksaw in a vise. I always try to put a nut at the top of the bolt I am cutting so when I remove the nut it chases the threads I have just boggered up. With a hacksaw, always move your thumb before you lean into it, because it sometimes wants to jump around)
http://www.hunt101.com/data/500/Thumb1.jpg

EVguru
02-23-2013, 04:40 PM
Lantern chuck.

rws
02-23-2013, 05:28 PM
I don't part off much, unless it's aluminum. The most popular hand tool in my shop is a port-a-band saw. I cut to rough length, then finish off the end in the lathe, 3 jaws are great for this.

KiddZimaHater
02-23-2013, 06:04 PM
Bench vise and hacksaw.

mikey553
02-23-2013, 07:03 PM
I use a hacksaw with a vise or lathe chuck holding the bolt. Then finish the end on the lathe, using a specially made split nut.

oldtiffie
02-23-2013, 07:20 PM
Get a bit of 3" or 4" square hollow ection (SHS) say 8">10" long. Square the ends up on your band-saw (if necessary).

Get (say) 2 bits of 1/2" or 3/8" plate cut to suit the ends of the SHS.

Drill and tap as many of your commonly used threads into the end-pieces.

Weld the end pieces to each end of the SHS.

Job done.

To cut any screwed section, spin on a bolt to sit the bolt etc. to be cut and spin the bolt etc. into therequired thread/s in the end piece/s.

Clamp the SHS in the vise on your band saw.

Adjust the bolt length to suit using you band-saw blade as a zero/gauge.

Tighten the (lock) nut and re-check.

Cut the bolt/s.

Job done.

Use any effective variations to suit your circumstances.

Start the band saw.

Job done.
Weld (say) a 1/2" or 3/8" pla

PixMan
02-23-2013, 07:36 PM
The only use for a 3 jaw chuck: holding hex heads on bolts securly.

What? You mean the fact that I've been using them for over 35 year to hold and turn round stock into good parts is all wrong?


I don't part off much, unless it's aluminum. The most popular hand tool in my shop is a port-a-band saw. I cut to rough length, then finish off the end in the lathe, 3 jaws are great for this.

Why is this? Is the something about parting off steels or other materials that is problematic on a lathe? This is an area that I just can't understand the mystery of doing it. Get the right tools and it's easy as pie. Use the least optimal tools (old HSS blades on a lantern tool post) and it can be tricky to dangerous.

darryl
02-23-2013, 08:17 PM
Cutting bolts to length is something I do fairly often. Done on the bandsaw, a piece of scrap is drilled and tapped, then the bolt screwed in. Depending on the length needed, there's either a spacer on the bolt, or the scrap is the right thickness. In some cases I drill a hole through a block of scrap, then insert the bolt to be cut- sometimes there's a kerf cut into the block at the right distance from the bolt head. In these cases, the bolt is loose, so I prevent it from turning using a wrench, sometimes vise grips, sometimes a socket. This is probably the method I use most, though for very short bolts I drill and tap the hole to hold it. Backing the bolt out tends to force the burr outwards, which makes it easier to sand off on the belt or drum sander.

Doing it on a lathe- I've long wanted to build a cutoff attachment which might be a powered hacksaw. Lately I've been thinking that I'd like a disc with hacksaw teeth on it- it would be run at low speed and also be an attachment. You would position it where you want the cut, then it would lower like a chop saw basically. I'm thinking that I'd have guides set up to control the side to side flex (like a bandsaw) and they would be adjustable. Most often they would be set quite near the edge- just far enough back to clear the workpiece.

I use bi-metal bandsaw blades- no reason why a disc with similar teeth wouldn't do the job just as well. Where would I get such a disc?

JCHannum
02-23-2013, 08:24 PM
When using the lathe to cut off or otherwise machine threaded stock or bolts, screws etc, I just use two nuts. Grip one in the three jaw chuck, thread the stock through the second one and install in the chucked nut. Adjust the stock so the desired cut off point is just outside of the second nut, lock the free nut in place and cut, face or machine as desired.

iMisspell
02-23-2013, 09:13 PM
Another way....

Pretty sure i seen his name posting here, Frank Ford:
http://www.frets.com/HomeShopTech/Tooling/ScrewShortenChuck/screwshortenchuck.html

_

oldtiffie
02-23-2013, 10:18 PM
How do you hold bolts and screws to modify or part to length in the lathe?
For most small ones I generally cut them with an abrasive disc on the dremel and finish on the belt sander.
For larger bolts I generally hold them in a coupling nut or similar and machine on the back side to tighten the threads. Cutting off to length gets to be a little more difficult so I was curious how others do it?
Would a split nut held in the chuck have enough grip to hold the part from turning if parted from the front?

If you are getting serious,why not get a "cold saw" as it will solve a lot of other matters in the shop as well.

http://www.machineryhouse.com.au/S830

http://www.machineryhouse.com.au/Metal-Cutting-Coldsaws-Ferrous

If I really needed one I'd buy it but with the small size stock I use and relatively few cuts I make I will stick to my 6 x 4 band-saw for now.

Lew Hartswick
02-23-2013, 10:20 PM
http://www.modelenginemaker.com/index.php/topic,1542.0.html

Try this link since I can't upload the pix here. :-)
...lew...

Don Young
02-23-2013, 11:59 PM
For bolts too short to grip with the 3 jaws totally on the shank, I thread a nut on and grip both the head and nut in the chuck.

Tony Ennis
02-24-2013, 12:05 AM
For bolts too short to grip with the 3 jaws totally on the shank, I thread a nut on and grip both the head and nut in the chuck.

I was doing this then found that the head and nut were different sizes causing the bolt to wobble.

Paul Alciatore
02-24-2013, 02:36 AM
For small screws I use a tool like this:

http://media.digikey.com/photos/Tyco%20Photos/696202-1.JPG

There are many such crimping tools that do an excellent job of cutting small diameter screws.

For 1/4" and above I screw a nut on the bolt and position it one or two threads above the point where I intend to cut it. This provides two points of support instead of the single one provided by the head. It can then be clamped in a vise and cut by hand or power hacksaw. It could also be chucked in a three jaw (with hex head and nut) chuck in a lathe and turned off. It may be necessary to add a turn or two of tape on the nut to insure that it grips tighter than the bolt's head. The bolt's head, even if a bit lose, will prevent the bolt from turning in the three jaw chuck. A chamfer is turned on the freshly cut end and then the nut comes off easily.

If I had a lot of them to do, I would set up some kind of stop to position each one in the same location.

Jaakko Fagerlund
02-24-2013, 04:26 AM
The only use for a 3 jaw chuck: holding hex heads on bolts securly.
?? If your chuck is in good shape, there is no reason why you can't use it for just about anything.

Arcane
02-24-2013, 05:13 AM
Lantern chuck.

Some time back I volunteered to make some new screws for a friend's wife's towel rack. I only needed to make 3 of them but they were a # 10 flathead screw made to fit an 82 degree counter sink. They had to be short, about 5/16" overall length and the threaded end had to have a 90 degree point. I made a lantern chuck to hold them and it worked great!