bandsawing steel stock - what am I doing wrong?

[Andre]

Everything else has been covered. My Hardinge lathe starts up so fast,I once wasn't paying attention,and started it backwards. The metal was spinning so fast,I couldn't tell the rotation direction. Then,I wondered why I couldn't get the tool to cut. Only momentary,but,stuff can happen,even after many years as a machinist!!

Your bandsaw needs to go 75 FPM to cut steel .

I needed to use a dovetail cutter, and it had a 5/8" shank. My 7 Brown and Sharpe taper mill only holds 1/2" so I used a friends BP. Plopped a half inch endmill in there (had to thin down the stock first) so I got familiar with all the knobs on the head, swapped the speed direction lever to hi and went away. For the life of me I couldn't figure out why it wouldn't cut and the chips were welding to the edge. Dumbo moment, didn't know I had to swap the fwd/rev button when moving out of backgear....

He was watching over my shoulder the whole time.....if he eventually hires me I hope he doesn't remember that moment!

After that it was fun running a 1 1/4" dovetail cutter 2200 RPM :biggrin: Given it was nearly 3 times the recommended speed for that cutter, it left a great finish and the cutter was still scalpel sharp after.

 

[george wilson]

I was using a collet chuck on the Hardinge,which made it even harder to tell the direction. I had switched the lathe to reverse to run a collet in by holding the rear bakelite piece,and forgot.

 

[Jamiethesquid]

As was said, its a wood saw and youll have to reduce the speed a lot. I put a triple reduction on mime (jackshaft) and now it cuts steel great. I have the formula, pulley sizes, pics, but not right now on tablet.

It would be great to see the info on the triple reduction, I have a Shopsmith Bandsaw that I am planning on making into a Stand alone metal saw. I am also palnning on building a power hacksaw that is going to run off my lathe. Craftsman Atlas 6"

 

[xalky]

The OP never returned back to the thread he started. What's up with that??

 

[higgite]

I went to cut the stock, put cutting oil on it, etc, and it didn't cut... period. I didn't pressure it into the blade, let it just let it take its time, but after about 4 minutes, I had cut into the plate about .030", and am sure the blade is now dull.

What's going wrong? Any advice is appreciated.

Thanks,
Jim

I'm still in my infancy as a hobby machinist, so pardon if this is a dumb question. Could the 1020 steel possibly have work hardened due to heat build up from too slow of a feed rate or wrong blade speed? Hence, the lack of cutting action?

Tom

 

[Jim Mass]

A good range for a metal cutting bandsaw would be to aim for 70-300 FPM
Hard steels, or thick stock, low end of range. Softer alloys and brasses, higher end of range. Aluminium can be cut faster than that but it just makes the reduction more difficult to set up.
Basic math will get you there. Dia of wheel (in inches) x Pi divide by 12, gets you feet per revolution.

Cheers Phil

Hi Everybody,
Thanks for all the advice. So far, we have...
1) wood bandsaw, too fast?
2) teeth pointing down?
3) tpi too high?
4) lube not a step in the right direction
5) blade tension wrong

So, out of those I can eliminate 2). Blade is put on correctly. Matter of fact, if it was put on any other way, the teeth would be facing the back of the machine, right? Anyway, to be clear, this blade does fine with aluminum - just having trouble with the steel.
I think I can also eliminate 5). Blade is tensioned to the indicator on the Jet tensioning mech, and at least appears to run smooth, straight and stable (no noticable flutter, etc). Or, is there something to be known about differences in tension between metal-cutting blades and wood-cutting blades that isn't taken into account on the Jet tension mechanism?
As for 1), I'm sure this is a wood bandsaw (bought it used at a great price). After reading your posts, I went out and tried to estimate the blade surface speed. Best I can tell (very blurry), the wheel is going at about 4 rev/sec. So, converted, that turns out to be in the neighborhood of 875ft/min. Does that sound about right for a wood bandsaw? Anyway, a far cry from the 70-300 FPM ideal that Phil quoted.
As for 3), that would be another step in the wrong direction?
As for 4), don't know. I could easily try without lube, but have the feeling I may have damaged the blade already. It still seems to cut aluminum OK, although more slowly than before my steel cutting episode.
Fabrikator, you mentioned triple reduction (jackshaft), pully changeout, etc. If you could share that info, I'd be grateful.
Thanks,
Jim

 

[JimDawson]

So, out of those I can eliminate 2). Blade is put on correctly. Matter of fact, if it was put on any other way, the teeth would be facing the back of the machine, right?

Jim

Nope, counting facing teeth to the back, there are 4 ways the blade could be installed.

Teeth front, point up
Teeth front, pointing down (correct)
Teeth back, pointing up
Teeth back, pointing down

The blade will turn inside out so it is possible to install it with the teeth pointing up. Sometimes you get a blade out of the box that needs to be turned inside out.

My guess is that the saw just needs to run slower.

 

[Frank Ford]

As for 1), I'm sure this is a wood bandsaw
Jim

There's the end to it.

Wood bandsaw runs on the order of ten times faster than steel cutting speed, so at the first touch, the teeth are dulled, and the cutting experience is over. Just hit a finishing nail in a piece of wood, and the blade is pretty much toast. Hit a serious chunk of steel at that speed and there's nothing left of even the best blade's teeth.

Now, if you limit your metal cutting to aluminum, you can use the saw for both wood and metal. Aluminum cuts readily at wood cutting speed. When I cut thick aluminum on my wood cutting saw, I like to lubricate the blade with an occasional touch of paraffin - it really keeps the cutting action free and avoids the aluminum welding itself to the blade teeth:

 

[Bill Gruby]

WOW -- If that blade is running at the speed to cut wood you are lucky there is a blade at all. Maybe even some of it in you. Steel cutting is slow.

"Billy G"

 

[Jim Mass]

OK, thanks to all again.

Looks like there's agreement on the cause - the high speed.
Jim, thanks for pointing out the 'inside out' blade = upside-down teeth possibility. In future, I won't take that for granted, maybe prevent another ruined blade.
So, where to go from here? I'm space-limited, would really like to have a one-size-fits-all bandsaw, and I really like this Jet (except for it being wrong for steel - right now).
Maybe a few possible routes:
1) permanent speed reduction?
- (like Fabrickator's suggestion) jackshaft type; like he said, probably get a 3:1 reduction going that route), and use existing motor; maybe in the neighborhood of $150-$200 cost if I did one myself (bearings, sprockets, shafts, plates, a bit of chain, new v-belt). Seems like it's still higher than ideal speed by a factor of 2 or more.
- speed reducer; can get bigger reduction, but may not necessarily be able to use same motor; probably custom new motor mount. Has anyone done this? War stories?
2) Change to a variable speed drive? This thought is very compelling, offering possibility of best of both worlds (unless the devil is in the details).
- what are pros and cons? has anyone done this for a reasonable cost? (My current motor is 1HP, 110V; I currently only have 110V available)
3) Get rid of this saw, and get a correct one for cutting steel (at maybe 10X or more of my current investment)

Thoughts appreciated.

If this discussion is beating dead horses, would appreciate if you point me to the carcasses.

Thanks again, and hope I can help you at some point.

Jim