Tool Arm size?

What size tool arm would you choose?

  • Total voters
    27
  • Poll closed .
K

Ken H>

Joined
Dec 31, 2011
Messages
4,651
Hello All - got a question, what is the preferred tool arm size? I know there's one top end grinder using 1.25" for the tool arm, but it seems like most are using 1.5" tool arms. I just found another vendor (https://www.ebay.com/itm/152758651156?) using 1.6" saying the choice was made because 1.6" is "more rigid".

What size tool arm do ya'll prefer? Myself, I like 1.5" because it's a standard size I can order from most any metal supplier.

So, come on folks - vote even if you don't post. The vendor and I have exchanged a couple of emails today with me preferring 1.5". He felt folks buying would prefer the 1.6" because it's "more rigid". I told him I'd open a poll and go by the results..... even if it wouldn't change my preference;)
 
I'm no structural engineer but my hunch is that there will be negligible benefit to the 1.6" over the 1.25" for our purposes as far as rigidity goes. The 1.25" would be cheaper but if 1.5" is much more widely available that might be the way to go. I think I have one of them "top end grinders" that use the 1.25" so that is what I would use personally.
 
I think the "rigidity" is BS marketing. Pretty sure travis uses 1.25 ALUMINUM in the tw90. I use 1.5in no problem like you said for availability and "industry standard "
 
I don't want a grinder that needs tool arms milled to size or that appears to be designed to have the tracking hinge at a 45 degree angle.
 
Sounds like a marketing tactic that proposes to solve a problem that simply does not exist. (Unless your problem is trying to sell your own proprietary tool arm.) Yes, by definition, an extra .100" of material will add some rigidity compared to a smaller cross section, but 1.5" is well above the necessary rigidity to begin with, for this application. Show me the flex in a 1.5" vs 1.6" tool arm, with even 200 lbs of tension, and I'd hazard a guess that it's negligible. Now what's is the tension from that gas strut? 35 lbs? 45 lbs? With a few inches of stick out from the grinder frame? Yeah, you're not going to see any flex, even on a 1.25" arm.

I do like the marketing speak for the .0001 "capable" cnc machine. You're telling me that this grinder holds tolerances of .0001 of an inch? Now THAT is impressive. The bearings in the pivot arm are also a nice touch. How many RPM are they rated for?
 
To me it’s along the lines of availablity! Like 2 X 72” Belts ... 1.5” And there would be no difference for our purposes, between 1.5” & 1.6” and, I’m not a papered engineer.
 
Last edited:
knife to a gunfight said:
I do like the marketing speak for the .0001 "capable" cnc machine. You're telling me that this grinder holds tolerances of .0001 of an inch? Now THAT is impressive. The bearings in the pivot arm are also a nice touch. How many RPM are they rated for?
Click to expand...

I agree, and while a decent CNC machine can hold tolerances of 1/10 of a thou, is there any need for that type of tolerances? Just think, if that tooling arm is machined to 1.600" exactly, and the slot to slide in is machined to 1.605", when new it's be slick sliding in with no slack. Once it's used a few times trash, dust, etc are going to prevent it from sliding in very good. I desire a bit of slop in my tooling arm for use. bolt to tighten down on tooling arm is going to take out any slack.
 
FWIW, I've only heard of one maker ever bending a 1.25" tool arm, and I'd really like to have been there when it happened. My only hesitation with 1.25" arms is that most available accessories are designed to work on a 1.5" tool arm, though I'm sure most or all can be modified easily enough. At any rate, if my options are buying a grinder with an odd sized tool arm, or buying one of dozens of other makes or models that take a standard sized arm, I'm going with the standard, every time.
 
I have two Bader 3s with 1.25 tooling arms. My local metal distributor carries 1.25 in cold roll and aluminum.
 
My opinion... either 1.25 or 1.5 is fine. Bader grinders and Travis Wuertz uses 1.25 and most other grinders use 1.5. I like 1.5 but I have a Travis Wuertz surface grinder attachment so I had a 1.5 tool arm milled down by 1.4" on two sides to make the last eight inches 1.25 which works perfect with my grinders. I think the more important question is in choosing a grinder with an extra tool arm slot so as to provide unlimited work rests and other attachments. Just my opinion. Larry
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The 1.25" arms on my Esteem are plenty ridgid. If I ever bent one, I imagine I would have be doing something pretty stupid, which is possible I guess.
1.5 seems to be the new standard, but I'll take a bit of weight reduction.
 
1.25” is plenty. Ask every Esteem, TW-90, and Bader owner. If someone wants to argue about it walk away and don’t waste anymore time worrying about it.
 
I’ve used a grinder with a 3/4 x 1.5 alum arm and i would bet money no one here could bend a 12-20 long piece with just their body weight.

Sounds to me like he made it to fit a 1.5” arm but didn’t like the slop so made then 1.6 to be tight. Like was said above that’s great when the machine is clean, but he gets it’s a machine that turns materials into dust....
 
Oh, I wanted to make one more comment on this subject that I forgot before. I make all my tool arms from aluminum stock. A standard KMG tool arm weighs about 13 lbs but an aluminum replacement weighs only about 3 pounds. With the weight of the contact wheels or platen and chiller those arms can get heavy and tiresome. I love aluminum. Larry
 
All my arms are made of 40mm square bar mild steel (about 1.6”). I like them solid for rigidity.

But my latest arms are in 40mm square bar aluminium instead. They are just as rigid, but less cumbersome to move around.
 
I think 1.25 is better because it is smaller, lighter and as said above, not any less rigid from 1.5. I voted for 1.5, though, because it is much more readily available. 1.25 is great, but if you need to look longer for what you need and possibly spend more, just go with 1.5
 
Please allow me to clarify my feelings here - I agree 100% that 1.25" is plenty rigid, heck - even 1" bar would be VERY difficult to flex under use. My thinking on 1.5" is availability. I used 1.5" because it seemed that most all the other grinders used 1.5" and I wished to match them. At the time I built my first grinder I wasn't aware of Travis's or any of the other grinders using a different size.

The main idea of this poll was to see how many folks felt the vendor's choice of 1.6" tooling arm was a good idea. I don't know the person, don't even know his (her?) name. I happened to see the grinder yesterday on fleabay, thought it was a good price, got to reading the specs, got to the 1.6" machined tooling arm..... What? 1.6" Why? So, I msg'd the vendor asking about the why of 1.6" and said that would almost be deal breaker for me. Vendor couldn't imagine anybody being concerned about the choice of 1.6" size. So, I decided to post a poll and see if the he (she?) was right. It seems everybody here agrees with me - NO to the idea of 1.6" tooling arm.

Ken H>
 
I have 1.5" because that's the grinder I bought. If I had more money I would have bought the 1.25". I wouldn't go with a grinder that has 1.6" though. You'd have to modify everything or have a bunch of slop and could change the alignment of the wheels.
 
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