PDA

View Full Version : best way to cut bolts?



chylld
20th September 2005, 11:06 PM
heyas,

what's the best way to cut 3/16" (4.8mm) zinc-plated bolts? the 2 best options i can think up are bolt cutters and a dremel with a fibreglass-reinforced cutting wheel. cost is a very big concern and i think the bolt cutters will work out to be much cheaper, but will they be able to handle new bolts? all the discussion i've found says they work wonders for rusted bolts but i need to trim new bolts to solve clearance problems.

Wood Butcher
20th September 2005, 11:13 PM
why not cut them with a hacksaw and clean up with a file later???

JDarvall
20th September 2005, 11:15 PM
Have you got a lot bolts to cut ?

The quickest way I know (and I'm no metalworker, ok) is to use 1mm cutoff disks in a normal hand grinder. "flexit" I think the brands called. Might have got that mixed up. Anycase, easy to get,,,,,I get them at my local mitre 50 (no, thats not a mistake)
so, bolt head in vise, nut wound up past cutoff line, rippppppppp, wind nut off.

Should you not know the 'nut' trick.(I'm just so proud of this nut trick)...... Before you cut off, wind a nut past the cutoff line first. So that after you've cut off, winding the nut off will reform the start of the thread ; else the thread may be too damaged at cutofff.

chylld
20th September 2005, 11:22 PM
thanks for the fast replies! :)

woodbutcher - that's my usual method, however this time around i have several dozen of them to do (nearly 100) and that'd take too long. ideally i'd like to have each one done and dusted in a few seconds.

cutoff disks in a hand grinder - sounds like it could work :) i don't have a hand grinder at the moment though, how are they priced in comparison to a good pair of bolt cutters?

the 'nut trick' is VERY useful though - i can't believe i didn't think of that before. i always used my half-round to try to manually reform the thread and then put the nut on!

chylld
20th September 2005, 11:25 PM
i guess i should say: these are brand new bolts for a project i'm just starting. the design calls for bolts to be no longer than a certain length otherwise they foul various moving parts. so the bolts, being brand new in the box, can be tortured in any way they need to be; they aren't stuck in existing material or anything.

JDarvall
20th September 2005, 11:34 PM
cutoff disks in a hand grinder - sounds like it could work :) i don't have a hand grinder at the moment though, how are they priced in comparison to a good pair of bolt cutters?

I don't know how much bolt cutters are.... A good pair, I'd imagine would approach $100 at least wouldn't it ?

A powered hand grinders are quite cheap. And you'll always have use for one. I guess you'd appreciate a tool that can be used for more than just cutting bolts. Cheap ones are often fine......Something like $30 at bunning.

the 'nut trick' is VERY useful though - i can't believe i didn't think of that before. i always used my half-round to try to manually reform the thread and then put the nut on

yep....I didn't know about it for a long time,,, so no more fiddling about trying to fix thread with files.

I don't know what your project is exactly, but if fouling bolt heads is a concern and your bolting metal together, then tapping holes may be an option.

Might help . :)

chylld
20th September 2005, 11:41 PM
i just looked around online, the good bolt-cutters seem to be pretty expensive indeed. i'm hoping that bunnings will have a <$10 cheap unit that can handle 3/16" bolts - i'd imagine it'd be a gamble though.

funnily enough i've never ever needed a hand-grinder before, the closest i think i've come to 'needing' it was when i saw a kit that converted one to a biscuit joiner - most of my work is with wood so that caught my attention :)

tapping holes is an idea i played around with before, unfortunately i don't think 6mm MDF will tap nicely :) what i'm building at the moment is a prototype for a DIY projector so keeping costs down is a high priority, i actually crossed the 4-digit mark today but having spent the last 3.5 months designing the thing in a CAD program i'm fairly confident of what i'm doing :)

gatiep
20th September 2005, 11:50 PM
Wouldn't ordering the bolts in the right length be a simpler and cheaper solution. Good luck with the $10 boltcutter. Maybe use the $10 to buy some fuel for your car because you'll probably need it to do another trip to the hardware store to get a good boltcutter. One is lucky nowadays if you can buy 2 'good quality' hacksaw blades for $10.

JDarvall
20th September 2005, 11:53 PM
All the best with it.

I don't know about $10.....Sounds too cheap :rolleyes: :D I don't know. Shorely it would last for 100 bolts anyway, then, maybe, take it back :D

Forgot to mention, regarding those 1mm disks. Because there so thin their very quick for cutting off,,,,, but, this also means they are also unforgiving on your flesh.
I reakon one of these could easily cut a finger off, if you forget yourself. Just something to remember. You might get a little complacent nearing that 100th bolt. I know I probably would.
Sometimes they wear very quickly as well, depending on the material. So, I'd buy at least 2 disks.

need to sleep

Goodnight.

RETIRED
20th September 2005, 11:58 PM
Do you need to use bolts? Would screws work? Not a joke but curious why you need bolts in MDF.

Sturdee
20th September 2005, 11:59 PM
Should you not know the 'nut' trick.(I'm just so proud of this nut trick)...... Before you cut off, wind a nut past the cutoff line first. So that after you've cut off, winding the nut off will reform the start of the thread ; else the thread may be too damaged at cutofff.

Used to do that trick, and three nuts did work better than one :D , but now I just round over the cut edges on the small belt sander.

Only takes a few seconds, looks good and works a treat and it is just as if they are made that size. Just make sure you wear eye protection in case of sparks.


Peter.

chylld
21st September 2005, 12:01 AM
where can i order bolts made to a custom length? for my project i'd need like 2 of 9mm length, 3 of 11mm, 1 of 12mm, etc etc. i.e. it gets ridiculous. the project is already running over-schedule and the time needed to calculate the required length of each of the ~132 bolts isn't something i have... which is why i figured i'd just buy 200 bolts of various lengths from bunnings and trim them down as i need them.

but yeah - $10 bolt cutters, what was i thinking. i remember buying cheap tin snips which binded after about 10-15 cuts. went back to the shop and exchanged them for wiss ones which have made several hundred cuts and are still going strong.

on a side note, i did some quick calcs just then and it turns out it costs me over a dollar in fuel to make the return trip to the local bunnings - what sucks even more i guess is the 20 minutes lost and the tedium of it all. one day i made 4 such trips, by the end of it i didn't even feel like going into my workshop anymore hehe

chylld
21st September 2005, 12:09 AM
Do you need to use bolts? Would screws work? Not a joke but curious why you need bolts in MDF.

no offence taken, it's a sensible question. main reason i don't want to use screws is because i don't like the idea of screwing into 6mm MDF 'endgrain' for something that needs structural strength. also some parts pivot around the bolts (i've bought nyloc nuts for this purpose).

the project is only a prototype but the need to keep costs down and thus the choice of 6mm MDF as a secondary structural material (primary = 3mm thick Al bar) led to a lot of problems - exactly how does one join 6mm MDF pieces together at a right angle such that they're strong enough to carry the equivalent of >2kg loads in 2 directions/axes? (sometimes 3?) that's why i chose to resort to right-angle steel brackets and a billion bolts - if anyone knows of a good box-joint jig for a router (without a router table) i'd certainly like to hear it! :)

cheers for the tip sturdee, i don't have a belt sander but i get the principle of what you're doing. i'll stick 3 bolts on anyway before i start cutting; the 'triple nut trick' :)

Cliff Rogers
21st September 2005, 12:15 AM
Don't suppose you have a brad gun or a staple gun?

I'd make the rightangle MDF joints with a bit of quad, a wipe of glue & a few brads or staples to hold it while it dried.

RETIRED
21st September 2005, 12:15 AM
Ok then.

If you have a look at some crimping pliers that are used in automotive electrical work they have bolt threads in the circular hinge part. If you use these they do an excellent job of shearing the bolt cleanly so that a nut just goes straight on.

A little more expensive but I would use brass bolts, they cut easier.

RETIRED
21st September 2005, 12:16 AM
Don't suppose you have a brad gun or a staple gun?

I'd make the rightangle MDF joints with a bit of quad, a wipe of glue & a few brads or staples to hold it while it dried.
Or even big rubber bands.

chylld
21st September 2005, 12:32 AM
sorry cliff, what do you mean by 'quad'?

: i'll keep an eye out for those pliers. i've yet to come across any pliers with any resemblance of bolt-cutting capacity, but if what you describe does exist then i'll definitely be wanting one :)

thanks for all your help so far everyone, turning in for the night. a whole forum page worth of posts in little over an hour! first i've ever seen it :P

RETIRED
21st September 2005, 12:35 AM
Repco or supercheap will have them.

Bed time for me too.

Cliff Rogers
21st September 2005, 12:39 AM
sorry cliff, what do you mean by 'quad'? ...

It's a 1/4 round corner strip of timber, you can get it from the hardware in Tassie Oak or Meranti or Pine. The 2 flat faces are at 90° to each other.
You glue & nail one flat surface along one edge with the other flat surface in line with the edge facing out & then you glue & nail the other sheet on as a but joint to the first sheet & the strip of timber forms the corner & holds it nice & strong & square.

I'll see if I can find a picture for you.

Section view....
http://www.glosswood.com.au/images/quad-19-x-19.jpg

Lots of profiles here... Quad is at the top of page 8.
http://www.tabma.com.au/NSW/profile%20bklt%20dft32.pdf

bsrlee
21st September 2005, 12:58 AM
Really cheap bolt cutters are only good for cutting nails - I've gone thru' a few sets making small solid rivets from clout & flat head nails.

Bigger bolt cutters that can cut 3/16 and up will tend to mash the cut part of the bolt, as well as being more expensive. 'Gal' bolts are made from a soft 'Free Machining' alloy and bend & squish much more than blackened 'Hi-Tensile' bolts. And you'll have to do quite a bit of cleanup, so you will need a power tool anyway.

The thin blades for angle grinders are also available from/for Bosch - they have a new cordless angle grinder that uses them. You probably should make some sort of jig to hold the bolts when you cut them so your fingers are out of the way - I've used 'Vice Grip' type pliers when just cutting a few, but they always seem to let the bolt twist some of the time.

Another possibility for your construction is/are 'Pop Rivets' - pretty cheap if you can find someone with a setting gun that they can lend you. You just have to but a pack of rivets - some include the drill bit too - and a big pack of washers to suit. Drill thru the angle & MDF in one go, put rivet thru, washer on the inside & 'POP' - its done. Bunnies & M10 usually have cheap kits of pop rivet guns, but you will need longer rivets than come in the kit. Then you'll only need the longer bolts for your pivot bolts.

Cliff Rogers
21st September 2005, 01:19 AM
More pics.

GAP COVERS

http://www.readersdigest.co.uk/diy/icons/IMG_152_1.jpg/$FILE/IMG_152_1.jpg</IMG>
Either quadrant or scotia mouldings can be used to cover an expansion gap between a wood floor and the skirting board around the room. The moulding is pinned to the skirting board, not the floor, and allows the wood to expand and contract according to damp or dry weather conditions.

The mouldings can also be used to stop draughts at the base of a window frame.



http://www.readersdigest.co.uk/diy/icons/IMG_153_7.jpg/$FILE/IMG_153_7.jpg</IMG>

Quadrant

Use for covering gaps between floors and skirting, and between wooden windows and the windowsill

Also to retain glass in windows and doors.

Type of wood and sizes Hardwood or softwood. 9 x 9mm, 15 x 15mm, 21 x 21mm.

Skew ChiDAMN!!
21st September 2005, 01:24 AM
I'm lazy and try to avoid extra steps when possible... ;) I'd avoid bolt-cutters, especially for light gauge bolts 'cos as well as damaging thread they can deform the bolt resulting in ovalling. They create more work to clean everything up...

If the job allows it I'd use an angle-grinder with either cut-off or grinding wheels but first I'd assemble the job and then cut off or grind back the extra thread. If there's not enough room one way, try inserting the bolts from the other side. This way ya don't have to worry about holding the bolts to cut 'em, nor is there any risk in cutting at the wrong spot. The same method's good when hacksawing!

BTW, I think all the above is an extra step too far... methinks cliff has the right of it. Quad or something similar. Far less effort, good result.

Cliff Rogers
21st September 2005, 01:26 AM
Yanks seem to call it '1/4 round corner moulding'
Poms seem to call it 'Quadrant'
We call it 'Quad' & you'll find it in the cover strip section of the hardware store.

Simomatra
21st September 2005, 01:31 AM
Ok then.

If you have a look at some crimping pliers that are used in automotive electrical work they have bolt threads in the circular hinge part. If you use these they do an excellent job of shearing the bolt cleanly so that a nut just goes straight on.

A little more expensive but I would use brass bolts, they cut easier.

AsRobbo sayus these plyers will do the job they have different size holes for the different thickness of bolt.

At 3/16 you will have no trouble also use the nut method to help keep the threads ok

Cheers Sam

rick_rine
21st September 2005, 01:45 AM
[QUOTE=Cliff Rogers]It's a 1/4 round corner strip of timber, you can get it from the hardware in Tassie Oak or Meranti or Pine.



It's interesting to hear a Queenslander refer to Tassie oak . I just thought it was our local timber used here in Tasmania . Don't you all have your own gum trees ? Is it really Tasmanian Gum you are using or is it just a generic term for eucalyptus ?
Interested to know .
Rick

Cliff Rogers
21st September 2005, 10:19 AM
Tasmanian Oak Eucalyptus delegatensis FTA
Tasmanian Oak Eucalyptus obliqua FTA
Tasmanian Oak Eucalyptus regnans FTA

Bodgy
21st September 2005, 10:28 AM
Don't even think about $10 bolt cutters, these would be the toy ones, only good for cutting wire. Even the medium size ones have great difficulty cutting even mild steel around 3/16 as seen in concrete mesh. THey also have cheap steel jaws which will blunt/deform long before you've got half way. Adequate, quality cutters will cost you $200 plus?

You can get a cheap hand angle grinder for around $20. A 'sacrificial' tool. Throw it when finished. Buy a few packs of cut off wheels tho, you'll be surprised how quickly they wear down. Also wear eye protection.

rod1949
21st September 2005, 10:41 AM
A month or two ago now I picked up a 100mm angle grinder from Bunnings for about $12 (240volts) 12 months warranty etc.

You can get 1mm thick cut-off disc's for about $2, and they are absolutly fantastic. You would probably only need one disc but get two.

Problem solved.

chylld
21st September 2005, 01:16 PM
the quad seems like an interesting idea, but unfortunately i don't have a nailgun. also i'd prefer it to be undoable as the various parts of the assembly will need to be dismantled for transportation (and also because i hardly get things right first time)

i thought about using rivets before and i actually bought a rivet gun for this very purpose. however as it turns out i'm quite pathetic with that tool and even when i do manage to snap the rivet, half the time the head ends up half-way into the MDF :( i did however take the suggestion of putting a washer onto it before snapping it and it did seem to help in that respect, but then it won't do for the ones that i need to be slightly loose, and also the ones that need to be countersunk.

i feel bad for knocking back both your ideas, but the need to dismantle parts is a fairly high priority so i'd like to stick with bolts at least for the prototype. if the design makes it into production then i'll definitely be looking for a more permanent method where i know reversibility won't be an issue :)

so back to the issue of cutting bolts - it looks like i'll be steering very clear of the cheap bolt-cutters :) the crimping/cutting tool sounds like the best option, however i'm having trouble picturing how it works and none of my searches come up with any useful pics/info. what's the proper name for that tool? does anyone have a pic of it? (does bunnings have it?) :)

save that, a cheap angle grinder might be my best bet. there'd be lots of sparks flying though so i'd prefer not to assemble it before cutting :)

Zed
21st September 2005, 01:56 PM
FWIW, I'd use a 5 inch angle grinder with the wheels, if you use a bolt cutter it will damage the end threads and you'll need to file it anyway. If you use an angle grinder its not only quicker and easier on your hands, but you can also "file" the end of the bolt with the wheel to get the burrs off.. This may be a good applicaiotn for a ozsheeto or gmc cheapo angle grinder.

barnsey
21st September 2005, 02:27 PM
Chylld

If you are using zinc plated screws and nuts because you don't want them to rust then remember that cutting them will destroy the protection and you will need to address that.

132 Bolts with a hack saw or bolt cutters seems like you would need to be a well heeled masochist. Buy the best quality 100mm angle grinder you can afford, a couple of disks and go for it. I think Supercheap or Crazys do 'em for under $20.

Sparks!!?
If you are worried about what they might do use a bit of scrap metal to protect the areas around where you are cutting.

Me - I'd do the bolts up tight first and grind the ends off flush with the nuts. If you need to protect as above a dob of paint would suffice (cold gal paint would be best). If not the nuts will tend to be locked tight after grinding anyway. ;)

FWIW

Jamie

chylld
21st September 2005, 03:24 PM
i ended up getting some kincrome crimper/cutters from bunnings for 13 bucks, they work just as well as i imagined. the bolts are 3/16" (4.76mm) but i chucked them into the M5 hole in the cutters and it was surprisingly easy to shear the end clean off! the bolt tilted a bit owing to it not being the right size for the hole, but it's still a very acceptable result. the nut trick would probably fix the tilt problem as well as serve as a means to clean up the end of the thread... in fact i'll give that a shot now since it's so fun :)

*tries it*

yes... that works much better indeed :) much squarer cut. trimmed a 25mm bolt a couple of times, now it belongs in the 16mm box! heheh

thanks for the paint/rust protection tip, i never thought of that; yes i am using zinc-plated bolts.

power tools are pretty much out of the question now, i can't do it with the thing assembled due to proximity to very expensive electronics, so i have to do it before it goes in. with the cutters i just bought i can do each bolt straight out of the box, indoors, and in about 10 seconds per bolt which is plenty fast :)

ozsheeto... lol.

bsrlee
22nd September 2005, 12:51 AM
A tip about pop rivets - if you want them to be a bit loose, just put a large paper or thin card washer under the metal washer. Punch a hole in the paper washer with a small hole punch (rotating plier punch) and make a slit from the hole towards the edge. When the rivet is set tight, you can then rip the paper washer free. A card washer just makes the rivet looser.

This also works with solid, pound over rivets.

If the washer won't all come out, just work the joint a few times & the left behind paper will crumble & fall out in little bits.

chylld
22nd September 2005, 01:06 AM
thanks for the tip bsrlee. even though the pliers i just bought solved my bolt cutting problem, i'd like to hone my skills with my rivet gun because to be honest i'm just pathetic at using it! i don't know if i'm just weak or what, i have no trouble at all cutting steel with tin snips or using the pliers to shear bolts, but the rivet gun... nup. as much as i hate to admit it, i think i'm afraid of it going 'SNAP' when the shaft breaks free - something i haven't prioritised conquering especially given that i can bolt it together just as quickly!

Andy Mac
22nd September 2005, 09:57 AM
Hi chylld,
It sounds like you've solved your immediate problem, but I'll chime in with few ideas anyway! I would have searched for the right lengths to start with:D
I got a nice medium sized set of bolt-cutters from a local tool supply shop, on special, for $30 (A little tweaking to align the cutting edges) which will easily cut 8mm bolts, and I'd prefer to use them than a grinder. The deformed section is relatively easy to grind into shape on a bench grinder/file. A thread file is a wonderful thing!
Further to Apricot trippers nut-on-the-thread-before-cutting tip, using either cut-off wheel or hacksaw: if the bolt is hex head, both head and nut can be clamped in the vice which will keep it all steady and protect the thread. I usually have a set of soft jaws handy, which are just aluminium angle, to slip over the standard jaws. If the head is countersunk or some other type, clamping in the vice can damage the head, so I clamp the offcut end of the thread firmly in the vice... damage there is irrelevant.
Pop rivetting...one of my favourite joining techniques to teach students! They come in a handy range of length (rivets not students) up to 32mm grip length!, diam, head, and material. Even the snap-off stem can be got in steel, s/steel, copper and aluminium.The choice of material is prolly causing your problem, 3.2mm diam in soft aluminium shouldn't pull into the MDF if you use washers, or the new larger head type. I've even rivetted drafting film (paper) and rubber onto wood with these. It also helps to have one of these pneumatic rivet guns, but then I've done thousands of the things at a go, for surface texture!!
Cheers,

chylld
22nd September 2005, 12:43 PM
hehe well i did buy 12mm, 16mm and 25mm long bolts, since i have so many bolts of required lengths of 12, 13, 14mm etc. i figured it'd be best to buy the popular sizes and then cut them down, instead of having to order 32 12mm ones, 18 13mm ones, 22 14mm ones etc. But yeah thankfully the problem is solved :) (and i got a new tool so i'm happy)

i'm using 2 types of bolts, square ones and hex nyloc ones; square ones cos they come with the bolts :) i found that if i wind the nut onto the bolt first, then screw the bolt into the cutter, then wind the nut down to the cutter and tighten it a little bit, that works wonders in keeping the bolt straight and the cleanup afterwards is a trivial case of totally unwinding the nut. given the speed and cleanliness (?) of the whole process, i really couldn't ask for better! i'm glad i came to the forum to ask for help though, wouldn't ever have guessed crimping pliers would be the thing to look for.

yeh using washers helped the pull-in problem, i still don't like the manual gun though. now that i think about it, maybe it's because i bought a cheap one - my friend's one worked better, but it might just be a case of differing mechanical advantage. a pneumatic one would be the best though! if i go into production i'll most probably be taking that approach.

thousands of rivets for surface texture - that's... interesting :)

Paddy
23rd September 2005, 12:36 AM
Buy yourself a cheap 4 inch angle grinder at Bummies for about $50 and an a few 1mm abrasive wheels.You will have to go to a real tool shop for the disks!

One of the most usefull tools in the workshop, hardly use the hacksaw these days..will cut corrugated roof sheets..frequently cut small items from 4mm steel sheet.. 10mm rod. One good feature is that if you miss-treat the blade it just shears off around the boss without any real drama! with a bit of practice you can cut curves as well!

Bought a cheap mount from Bummies also $60 which turned it into a docking saw, cut hundreds of 45 degree cuts on 15 mm*2mm steal tubes.

Paddy