Request For Quote- Qty 2, square shaft, tight tolerances

2 attached pdfs show a difficult part that I've been trying to make. "Process 1" shows the blank, "Process 2" shows the desired part.

I had a few of these blanchard ground. They hit the dimensional tolerances, but not the straightness/flatness. They were flat to 0.003 or 0.004. I imagine that the magnetic base held the part flat.

I got a quote from somebody who was sure he could nail the tolerances. He said he would grind down to 1.420 x 1.420, then stress-relieve, then finish the grind. But he wants $600 for 2 parts.

I can't pay $300 per part. I would like to pay no more than half that.

I could supply a stress-relieved blank that is 1.420 x 1.420 ±0.005 if anyone thinks they could finish the job for $50 or $75.

I would also be willing to make sacrifices if necessary to bring the price down:

1) change the 1.400±0.001 to 1.400±0.002

2) change the Flat and Perpendicular tolerances from 0.001 to 0.002


Also, I may fab the blank from 1/4" plates, with 4 welds rather than the square tubing if we think that will make a more stable blank.

Please note that this will not be a fast cash job. I'm playing around with the out-of-spec blanks I already have, and I won't need more for about 2 months.

thank you

I would say someone needs a nice grinder with a super strong magnet for this one. I would be real leery of bargain hunting if you want a good part.

What do you mean by stress relief? Also, How many parts were you wanting? 2 ?

From http://www.efunda.com/processes/heat_treat/matl_modify/stress_relieving.cfm :


"Machining induces stresses in parts. The bigger and more complex the part, the more the stresses. These stresses can cause distortions in the part long term. If the parts are clamped in service, then cracking could occur. Also hole locations can change causing them to go out of tolerance. For these reasons, stress relieving is often necessary.

Typically, the parts that benefit from stress relieving are large and complex weldments, castings with a lot of machining, parts with tight dimensional tolerances and machined parts that have had a lot of stock removal performed.

Stress relieving is done by subjecting the parts to a temperature of about 75 ºC (165 ºF) below the transformation temperature,line A1 on the diagram, which is about 727 ºC (1340 ºF) of steel—thus stress relieving is done at about 650 ºC (1202 ºF) for about one hour or till the whole part reaches the temperature. This removes more than 90% of the internal stresses. Alloy steels are stress relieved at higher temperatures. After removing from the furnace, the parts are air cooled in still air."


Yes, I am still making these 2 at a time.

You need more mass.
Make it out of solid stock.

Obviously making it out of solid stock would be cheaper and easier. The purpose of the design is to LESSEN mass...

It is surprising how many people do not see the obvious.

It needs more mass to be worked to your specs and remain stable.