Looking for suggestions.....

[Hellbender]

I need a way to cut/grind the heads on some grade 8 bolts (lots of 400 each)

They are 3/8"Dia.x 1" thread length, standard hex head.

I need one side of the hex head removed even with the shank (nothing critical, it's just for clearance). It's being done w/ a bench grinder one at a time now, but it's a slow PITA.

Thanks for any suggestions,

HB

------------------
NRA Lifetime Member

[Rob Frink]

HB,

How about a heavy belt grinder?

http://beaumontmetalworks.com/kmg1pics/kmg-10.jpg

With a hard serrated contact wheel and belt speeds up to about 7000ft/min, these babies will grind 1" bar as fast as you can push it into the wheel. Modern abrasive belts have way more material removal performance than hard stone wheels. These are commonly found in foundry clean-up rooms for removing gates and risers.

Just some food for thought.

Rob

[Ragarsed Raglan]

How about some real H/D bolt croppers, the ones the motorcycle thieves use for cutting through hardened security chain, then clean up on a linisher???

Just don't get caught by the 'local chapter' with them though....

RR

[Thrud]

Rob

That is a beauty, who, where, why, whow wmuch? You are making me drool, man - stop it! http://bbs.homeshopmachinist.net//biggrin.gif

[Hellbender]

RR-Tried that already, I have a 36" and a 48" pair, but there isn't enough "head" on the bolt to get a bite with the big, thick jaws.

Rob-Damn, that's nice! Wish I had one!

[Paul Gauthier]

I think I would make a fixture to hold them and mill it in one pass. Although I have tried turning grade 8 bolts before and they are tough. But with good rigidity and a solid carbide end mill it should work.
Just a thought......

------------------
Paul G.

[John Stevenson]

Get a piece of square metal about 1 1/2" square 6" long.
Drill a series of thru holes in a row 3/8" down from the top. Space these out so they are just greater than the across corner width of your bolts.
Drop two bolts in at opposite ends and turn so they are level top and bottom.
Mark a line off at the bottom face and then mill a small flat along the work to form a step wher the bolt head fits. No too deep, about 1/8". This is so the heads have a register position.
To use, load with as many bolts as you can, place in vise and run a milling cutter down the top exposed bolt heads, release and reload.
HTH.

John S.

[Hellbender]

John S.--We thought about something like what you are describing, only we were gonna make it so it had a row of bolt heads on both sides of the vise jaws (bolt threaded section lying horizontally).

BUT, the bolt's head thickness is not very uniform (the markings on top, I guess) and we were afraid the vise jaws would not hold all the bolts rigidly enough for a carbide cutter.

Anyone--I don't have one, but would a magnetic chuck (put a spacer plate under the threaded part and another supporting the heads)hold these well enough for a surface grinder?? Or would that take forever?

Thanks again,

HB

[alsinaj]

Rob,

Belt grinder looks REAL interesting. Are plans/more pictures available?

Will all abrasive belts handle 7000 sfpm, or do you have to get special ones?

Where can one get a hard serrated contact wheel?

Thanks, John
----------------------


<font face="Verdana, Arial" size="2">Originally posted by Rob Frink:
HB,

How about a heavy belt grinder?

http://beaumontmetalworks.com/kmg1pics/kmg-10.jpg

With a hard serrated contact wheel and belt speeds up to about 7000ft/min, these babies will grind 1" bar as fast as you can push it into the wheel. Modern abrasive belts have way more material removal performance than hard stone wheels. These are commonly found in foundry clean-up rooms for removing gates and risers.

Just some food for thought.

Rob

</font>

[John Stevenson]

HB,
Good point about the markings.
In that case make it taller and thinner so it sticks out the top of the vise and put nuts on the exposed threads.
Air wrench for speed???

Don't think a mag table will hold on this small surface area plus it will take forever and a day.

John S.

[Rob Frink]

My company builds these belt grinders. The tooling can be quickly changed over by sliding the tooling arm out and the next arm in. My primary customers are foundries, fabricators, blacksmiths, and custom knifemakers, cowboy spur makers and metal smiths in general.

http://beaumontmetalworks.com/kmg1pics/kmg-1214_2.jpg


http://beaumontmetalworks.com/kmg1pics/kmg-pl-3.jpg


I have a variety of different tools, cona=tact wheels from 1/2" to 14" diameters, slack belt attachment, rigid platen attachment, rotary platen attachment, ...and all sorts of special designed fixtures and attachments for customer requirements.

http://www.beaumontmetalworks.com/rotaryplaten/Mvc-017.jpg

http://beaumontmetalworks.com/kmg1pics/kmg-sba5.jpg


John, belt speeds should vary with the grit, material, and abrasive type, and task. Speeds upto 10,000ft/min are not unheard of. There is a wide range of abrasive belt types for metal removal with specialty abrasives such as ceramics, polycrystaine, Alumina Oxide,...etc. Also there are different types of binders and backing. Some belts have a lubricant film. Because the belts are light weight, speeds are almost limit less. Coarse grit belts run best at higher speeds and finer grits must be slowed down to control the temperature. Common belt speeds are about 4000-6000ft/min for 60 grit cutting steel, 200-500ft/min for a 600grit on steel.

Smooth faces contact wheels provide better surface finishes while serrated wheels have a more aggressive cutting action. The serrated wheels also run cooler and provide more contact pressure by reducing the contact area. This effectively drives the abrasive deeper into the work piece for faster cutting. With some abrasives, the serrated wheels provide better belt life by allowing the abrasive grains to fracture and regenerate cutting edges.

The horse power requirements are from about 1hp to 5hp depending on the type of work and performance expected. DC variable speed motors are the motors of choice for home shop craftsmen while AC invertors are the choice for industrial applications....and of course single speed motors.

Wow, that was more than I was planning on getting into....

I don't want to corrupt the board with commercials, ads and shameless plugs... so feel free to contact me offline for more info.

Sincerely,
Rob

[Hellbender]

John, The problem is the time, I need these made cheaply, I hate to put $1 labor in a 10 cent bolt that I can only get 50 cents for, know what I mean?

I think some form of higher speed grinding (like Rob's belt grinder) may be the answer.

Thanks again,

HB

[Rob Frink]

HB,
I just thought of another idea. I did this for a short run prototype order a few years ago....it was kinda similiar.

I used a shaper and made a fixure to hold the work piece in the head where the tool holder normally goes. Them I clamped a broach in the vice. For your job, make a simple fixture to hold the bolt in the tool holder, then get a large broach say 3/4 width or a couple of 3/8 clamped side by side in the vice. When the shaper goes through the power stroke, then the hex on the bolt is cleanly cut away by the broach. Stop and reload...repeat.

[Peter S]

Rob,
Thats a clever idea, not sure about this application, but I like it.

Interesting about smooth and serrated wheels. I have always used serrated wheels, I wonder if thats why I've found belts no good for sharpening drills, unlike others on this newsgroup. Have found that the belt tends to round off cutting edge (in a minute fashion, that is). Much prefer grinding wheels for cutting tools.
Actually, apart from cutting tools, I haven't used a grinding wheel for years. For general grinding, a belt (I know them as linishing belts) is about ten times better. One of the essential workshop tools, I think. I use the 3'x2" type that fits directly onto one end of a 8" bench grinder.

HB,
If you are looking at 1000s of these ("lots of 400 each" you say), you may as well get a quote from a bolt manufacturer. I have quite often had specials made, though admittedly, I've never asked for a weird head.
A large, powerful belt grinder would do this job well, but with 1" of thread, you would need someway of holding the bolt so you can really lean on it and grind it off in a few seconds. I think if you put the bolt into a tube type holder, the bolt head would roll on the belt when you push hard...can't think of an answer to that at present.

[spaceace]

take a piece of steel, say 16" long x 1"wide , put it in your mill vise and tap a line of holes to fit your bolts. screw the bolts in and torque them down. use a left hand endmill and mill the to size.

[lynnl]

That last post by spaceace raises a question I've wondered about before.

Are commercial high quality bolts/screws/etc (such as grade 8) made so that the threads start at the same position, relative to the flats? I've assumed most threads are stamped or rolled in the commercial mfg process, and would not expect any such consistency in ordinary hardware store fasteners.

[Hellbender]

Peter S--Minimum production runs on grade 8 bolts run in the 10,000+ range, if the $$$/quantity was there, that would be the way to go. On the grinding, I was thinking of placing the top of the bolt head on the table with the threaded part sticking up, slide a tube over the threads, and push the head in w/ a pushstick. That's what we do on the grinder now.

spaceace--lynnl raised the problem w/ doing this....the threads are not consistant w/ the head. I need one of the flats enlarged, your method would have no consistancy (although I realized I did not state this as being a requirement, I guess I should be more specific next time).

lynnl--your assumption is correct.

Thanks all,

HB

[Thrud]

HB

I think the least expensive way may be to machine some soft jaws for a milling vise and hog the one flat off. Grinding will work of course, but the abrasive costs may not make it worth doing. The soft jaw could be machined so that 2 bolts are milled at one time with a mill run between them. Great job for the old horizontal you were using for a paper weight! http://bbs.homeshopmachinist.net//biggrin.gif

[spaceace]

ok, say your threads are not uniform, and are not even close. do exactly as i said before, but this time make 2 steel bars with threaded holes and put a nut on the bolt before putting it in the hole, with 2 wrenches lock the bolt where you want it.
this will give you time to load the second
steel bar as the 1st cuts.

[John Stevenson]

HB,
OK we are in for speed and ease.
How about this ?
Take a steel disk 6 to 8" dia by 1" thick.
Drill say 8 holes right on the outer egde so that nearly break thru the outer rim.
Then drop one bolt in and mark the inside flat.
Transfer to lathe and turn a recess equal to this marked line. Finally fit bearing or pivot to the centre.
To use, drop 8 bolts in the holes to locate against the turned lip, offer up to belt grinder and spin the plate past it.
Either do 8 at a time and reload or motorise it and unload / load two handed.

John S.