Stihl USG Square Grinding attachment

[Del_]

I bought this new back in 1992 or so and have been it's only user. It's seen light duty mostly round grinding. I'm going to post some photos and answer questions that I can and post more photos and measurements when asked. This unit came out of Norfolk, I believe. A fellow named Brian came to our business in Delaware as a Stihl rep and taught us a little about tree felling, saws, and chain sharpening. He mentioned square grinding and I had read a little about it and he mentioned that Stihl had a USG square grinding attachment and I bought it.

Back in the early 90's we would get a 100 ft. roll of Stihl RS 3/8 .050 and I'd spin up the whole roll making 20 inch and 36 inch loops for our tree business. As each chain became dull I would store them up until I would run through 20 or so at a time. I would keep them in batches and do the a whole batch on the left side cutters and then do the whole batch right side cutters. This meant a lot less adjusting on the USG and greatly reduced my time spent sharpening. Of course if you didn't get the left and right sides exact it meant a whole batch was screwed. Not that it ever happened to me, LOL!

I make no claims at being an expert in the area of chain sharping but I do have a keen interest. I've gather dozens of photos of great looking square filed cutters over the years and have no idea who originally posted them. I knew they were good photos because people who I respected on the forums had said so. I use and still use those and newer photo as visual guides. I've played with hand square filing with some limited success.

These photos I've posted here and elsewhere before.

 

[Del_]

 

[davidwyby]

I saw a fellow once said he managed to square grind without the attachment with a lot of “stuffing about”. I think the main advantage to the attachment is the wheel profiling part. I think Squarejig does that by angling the head. Maybe I could do the same, or build a USG squarejig…

 

[Del_]

I saw a fellow once said he managed to square grind without the attachment with a lot of “stuffing about”. I think the main advantage to the attachment is the wheel profiling part. I think Squarejig does that by angling the head. Maybe I could do the same, or build a USG squarejig…

The square file base is spring loaded. The wheel is pulled down and then the chain in it's holder is advanced into the grinding wheel and can be 'bounced' there several times if desired until no fines are thrown, then the chain holder is allowed to spring return about 1/8 inch or so moving the chain away from the grinding wheel, then the grinding wheel is allowed to slowly spring return to its up position. There are two photos of this base spring. In one it is hanging down, in an inactive position.

In the one photo I have a hand on each knob, one on the chain holder, and one on the cutter wheel head. It's a two handed coordinated motion that is easy to learn.

That's the difference between the square grinding attachment base and the round grind base.

 

[Del_]

The USG manual.

 

[Del_]

Stihl USG parts list.

 

[Del_]

Another pdf.

 

[Del_]

A little larger file size for some reason for the Manual. It may or may not be identical to the first one I posted.

 

[Philbert]

Thank you for posting photos of the Unicorn!

Philbert

 

[chipper1]

That's cool Del, I was surprised I remembered who had it, especially when half the time I can't remember what I have . How does that work anyway .
I have seen some of those pics, maybe on opeforum, that I can't remember lol.

 

[Del_]

That's cool Del, I was surprised I remembered who had it, especially when half the time I can't remember what I have . How does that work anyway .
I have seen some of those pics, maybe on opeforum, that I can't remember lol.

Yes I've posted those same photo elsewhere.

It works pretty good but I've never used or even seen in person another square grinder so I have nothing to compare it to.

 

[kaare]

Do you have any photo of the finished chain/grind ?

 

[Del_]

Do you have any photo of the finished chain/grind ?

Welcome!

I don't have any good photos but I'll get some the next time I use it.

How did you find us?

 

[kaare]

Thanks - found the site googleing square grinding. I am searching for a Silvey grinder (cdm 4 or pro sharp). ordered a Stihl usg yesterday and will try to use/ modify this for square grinding.

 

[Philbert]

The square file base is spring loaded. The wheel is pulled down and then the chain in it's holder is advanced into the grinding wheel and can be 'bounced' there several times if desired until no fines are thrown, then the chain holder is allowed to spring return about 1/8 inch or so moving the chain away from the grinding wheel, then the grinding wheel is allowed to slowly spring return to its up position. There are two photos of this base spring. In one it is hanging down, in an inactive position.

In the one photo I have a hand on each knob, one on the chain holder, and one on the cutter wheel head. It's a two handed coordinated motion that is easy to learn.

That's the difference between the square grinding attachment base and the round grind base.

Do you suppose that a reasonably skilled machinist could produce copies of those?

CNC, instead of cast?

Seems to be s lot of interest.

@Homelite410 ?
@srcarr52 ?

Philbert

 

[Squareground3691]

Be interesting to see a tutorial video of it being used, it could be made , just cost ?

 

[John Lyngdal]

If Baltic Abrasives made a CBN wheel for square grinding on a USG, would that simplify the conversion of the grinder by removing the dressing components?
Is the spring advance of the chain a required feature, or just a helpful feature?
I'd just make the base from 6061 bar stock and forgo the cooling and mass reduction mechanical features used in the cast part.
I know where there is a Mori Seiki CNC available for use if someone made the files.

 

[Del_]

If Baltic Abrasives made a CBN wheel for square grinding on a USG, would that simplify the conversion of the grinder by removing the dressing components?
Is the spring advance of the chain a required feature, or just a helpful feature?
I'd just make the base from 6061 bar stock and forgo the cooling and mass reduction mechanical features used in the cast part.
I know where there is a Mori Seiki CNC available for use if someone made the files.

I like how you are thinking.

The chain is advanced into the wheel by hand and the spring returns it away from the cutter wheel. If the chain is not withdrawn 1/8" or so the wheel will grind off some of the top plate of the tooth as the motor/wheel moves upwards. It's the machining to allow the base to swing that short distance towards the wheel and then it's withdraw that is the important feature of the square grind base. I believe my photos above tells the story. I can't find the original non moving base part of the machine and it has been off of the machine for over 25 years.

Wheels can also be dressed by hand without those attachments.

The movable base casting has the same numbers on both stock and square grind versions so I imagine machining the stock base would be easier.

I'm willing to work with someone who has those abilities.

 

[Philbert]

There have been a few threads, over the years, about custom, CBN wheels for square grinding.

A couple of points came up:

- the durability of that critical corner profile (versus flat or rounded profiles);

- the fixed angles: prevents fine tuning, and adjustments to the cutting angles (although, basic angles could be tweaked with a file).

EDIT: Here is a link to one, related thread:

https://www.arboristsite.com/thread...r-wheel-specs-considering-a-cbn-wheel.229210/
Philbert

 

[Del_]

There have been a few threads, over the years, about custom, CBN wheels for square grinding.

A couple of points came up:

- the durability of that critical corner profile (versus flat or rounded profiles);

- the fixed angles: prevents fine tuning, and adjustments to the cutting angles (although, basic angles could be tweaked with a file).

EDIT: Here is a link to one, related thread:

https://www.arboristsite.com/thread...r-wheel-specs-considering-a-cbn-wheel.229210/
Philbert

That 'critical corner' wearing just a bit may enhance longevity!

....and could be easily touched up with a file.

I do have a CBN square grind wheel that I got custom made years ago for my USG.

I'll dig it out and post photos.