Author Topic: Starrett No.94 combination square  (Read 215 times)

Carpenter84

Starrett No.94 combination square
« on: September 11, 2019, 08:56:33 AM »
I own probably 6 combination squares.. all garbage... Never owned one I liked or wasn't a Chinese piece of junk.
So, I spent some money and bought a Starrett #94. eBay. Also came with the centering gauge, which I left at home in the shop as I won't use at work.
The bubble is shockingly sensitive and accurate(repeatable).
But the blade isn't square with the various planes.

Any suggestions on correcting? The blade/scale is not warped. It seems to be sitting in the seat crooked. It was thoroughly cleaned. I'm assuming I would need to lap the blade seat.
I'll take it home and maybe run it through some paces on the surface plate and see if the square body is actually square with the world and prove the blade seat is, in fact, out of align. I also don't want to lose the accuracy of the bubble by modifying the flat surfaces.

I'm open to suggestions.

(The pencil lines are the usual carpenters squareness test, drawing and line and flipping the square and drawing another line. This is not my only test. When I recieved the square I tested it to a few other squares in the shop and found the same result but just stuffed it in my work bag anyways...)
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: Starrett No.94 combination square
« Reply #1 on: September 11, 2019, 09:09:34 AM »
Hum..... I've never checked any of the Starrett combo squares I have.  Got me wondering, I'll do some checking and report back.  As for fixing the FU, not going to be easy.  Do you have a square knee that you can set up on your surface grinder to hold it for regrinding the bottom surface square to the slot?  Once done, regrind the 45 degree angle?
Ken

woodchucker

Re: Starrett No.94 combination square
« Reply #2 on: September 11, 2019, 09:11:28 AM »
so the problem is that you have the hardened head. I am surprised it is not square. you checked your reference piece, it's straight on the edge right?


I assume you checked for garbage in the bottom of the head. if not clean it out.


So get yourself a thin diamond file it has to be square, not rounded on the edges, that's the tough part.
remove the locking screw.
Put some tape on the flats of the file so only the edge is visible... you might have to use scotch tape ...
carefully remove material.. one stroke check.
it will be slow, but it should fix it. 
I have fixed my empires like that.  My starrett is dead on.. I bought a new satin blade for it at a farm show.
it's nice, but I only use it for certain tasks. I take out my small ones for small work. The empires are 4 or 6 inch blades.


I have another from Athol machine the company Starrett sued over his patent infringement... he wound up owning that company.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

chips and more

Re: Starrett No.94 combination square
« Reply #3 on: September 11, 2019, 09:35:03 AM »
First you must have a good square reference. And yes, I always check my squares. And yes, I have corrected a few combination squares in my day. Shame on that fleabay seller! My gut says the seller knew it was bad. I would rant on the seller! VERY carefully check for a burr(s) in the square slot!!! And check the scale for straight (never seen a not straight one?). If you do need to lap. You will need two scales. One sacrificial for the lapping. And the other for normal use. Don’t use any kind of diamond lap. Lapping won’t take long. It’s just a little protrusion in the center of the track that needs attention. USE FINESSE!!! No rocking when lapping. You can get a very successful result or a totally worthless POS!...Good Luck, Dave.

4GSR

Re: Starrett No.94 combination square
« Reply #4 on: September 11, 2019, 09:57:48 AM »
One thing I would do, is check it against something that has a dead straight edge to it, like a piece of flat ground stock.  Better yet, use the edge of your mill table and do the same test.  I wouldn't trust that piece of marble or what ever it is.

chips and more

Re: Starrett No.94 combination square
« Reply #5 on: September 11, 2019, 10:25:50 AM »
For a “square”, I find the contractors square (pic) surprisingly very accurate!

woodchucker

Re: Starrett No.94 combination square
« Reply #6 on: September 11, 2019, 11:31:35 AM »
actually the test Shawn did is the proper test when one does not have super accurate test blocks.


I will use a knife to scribe the line, and my test will often be right next to it.
That way I can see if they deviate at all. The eye is capable of picking up angles quite well.
Yes I do the direct overlay too, as a first check.
But I always do a side by side too.


The only thing about the test is the piece must be straight.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts