Material for fixtures

[Bob W.]

I have been building a lot of my fixtures from aluminum for my horizontal machine and I am finding that some of the higher use fixtures are just wearing out from the volume. I plan to re-make some of these fixtures from a high grade steel and I would like a recommendation for an alloy that will have a very long life and will be very tough (resist dings/ scratches, etc...). Do most shops heat treat high volume fixtures? If so, what hardness? Warping an issue? Finish machine after heat treat?

[K2csq7]

4140 HT

[specv]

we use A36 for most of our fixtures, but our parts are almost 95% aluminum, so they almost never wear out.

[crazy^millman]

I have made most out of A36 as well. Cut Hard Steels and 10-2-3 Ti on them for years without issue. I think you will be surprised how much dampening you will get out of the A-36 verse going in a different direction. You start going to an alloy and welding becomes more expensive and heat treating and then yes everything you are thinking about now. High Wear places I use hardened bushings or wear pads, but that is about it. Full Heat treat plates I think will cause more issues that it will solve.

[Newbeeee™]

Bob - take the easy way out and skim your important faces and sink in some gauge plate. Use these as wear strips.

Making 'proper' steel fixtures would be a last resort for me - roughing hardening grinding blah blah. Wear plates are the best way unless you're into automotive volumes imo.

[Newbeeee™]

Bob - take the easy way out and skim your important faces and sink in some gauge plate. Use these as wear strips.

Making 'proper' steel fixtures would be a last resort for me - roughing hardening grinding blah blah. Wear plates are the best way unless you're into automotive volumes imo.

[Bob W.]

The main fixtures that are giving me issues are the Raptor style dovetail vises we made. These were made out of aluminum and we use them all the time for prototype and production. We recently ran a production run of hardened steel (RC45) and these aluminum vises just weren't strong or hard enough to take the force. This is a repeat job and I need to make a new set of vises. I want them to last forever.

[Guyinthedesert]

I make simple fixtures from aluminum, but rotary and high use fixtures I use torchcut A-36 or J-20. Once I have a fixture drawn up, I email the outline of the pieces to our torchcutter. In a few days they show up all cut to size and Blanchard ground nice and flat for less than I could just order hot rolled plate for.

[Bob W.]

I make simple fixtures from aluminum, but rotary and high use fixtures I use torchcut A-36 or J-20. Once I have a fixture drawn up, I email the outline of the pieces to our torchcutter. In a few days they show up all cut to size and Blanchard ground nice and flat for less than I could just order hot rolled plate for.

 

Does machining the torch cut parts kill your cutters?

[crazy^millman]

Bob those jaws I would make out of HT material. I am thinking 20" x 30" plates of 4140 HT is going to be expensive. Get some double disked or Blanchard ground like suggested and build from there. Small sutff yse, but I would never think to grab any heat treated part with Aluminum.

[Joe788]

 

Making 'proper' steel fixtures would be a last resort for me a pretty much guarantee that the order will never repeat again.

 

Life experience fix.

[Guyinthedesert]

Does machining the torch cut parts kill your cutters?

 

No, not at all. It looks to me like they T/C them underwater, I assume that might help keep the edges from hardening. They will grind all six sides, if you want, but obviously that costs more. If you have any big holes, they can cut those through, saves a ton of time. I've had 6" thick steel plates cut 1/8" over, and it's amazing how straight and square they come out.

[Pilot Plant Supervisor]

I've been cutting some flame cut blanchard ground A36 lately. Unfortunately, one of our engineers ordered the material and had them flame cut to size. When just trying to skim a surface to get something to locate off of, it eats carbide. If you get an extra 1/8" per side so you can get the cutter under the hard edge, its no problem.

[crazy^millman]

TCI Precision does that kind of work. Send them your blanks requirements and they will 6 side it for you at a reasonable cost.

 

http://tciprecision....ne-ready-blanks

[Newbeeee™]

The main fixtures that are giving me issues are the Raptor style dovetail vises we made. These were made out of aluminum and we use them all the time for prototype and production. We recently ran a production run of hardened steel (RC45) and these aluminum vises just weren't strong or hard enough to take the force. This is a repeat job and I need to make a new set of vises. I want them to last forever.

In this case yes- go for hardened.

I was specifically talking fixture fixtures, not vices

[Sticky]

In general, for production fixtures, if the surfaces are smooth/machined that I am clamping too I am comfortable with 4140 annealed for less then 5000pcs/year. Anything over that, or anything with rough edges I get the same 4140 annealed, machine everything within .01", get it heat treated, install it, and finish machine in place.

[The_kid]

Having the flame cut under water will make a huge difference. and I'd use a fine pitch rougher or an older reg end mill then go back to finish it. Get under the burn Using hardened inserts that can be ground is the way to go. I have seen fixture plates that have hardened bushing and the fixtures have bushings for locating holes and you can incorporate several jobs onto a single plate to reduce set up times.

 

Let me know if you need anything ground I have access to surface grinders that will do pretty much anything that will fit into your machines. I can do ID and OD grinding as well.

[jeff]

The ONLY soft jaw/fixture that I have for repeat jobs that is made out of aluminum is a fixture for some delrin parts.

Running with aluminum soft jaws is just asking for headaches unless it's a 1 or 2 piece job..

All of my soft jaws/fixture are made out of steel. 1018,4140,4150,8620 etc... whatever I can find on the steel rack.

[mkd]

ASTM A36 will never get hard from flame cutting as it doesn't have the requisite carbon to allow it. This seems fine for all but the highest wear items.

 

If you want to make something real strong/ wear resistant, some mildly pre-hardend P20 would come to mind. If you want to step it up in terms of hardness Finkel's FX-T2 (40ish Rc) would do it.

[cincy k]

I would use 4140 HT or pre-hard (same thing). Easyish to work with and wears extremely well. I use Diehl Steel as my local provider though they will ship any where. They presquare all my material including larger plates on their Amada machines. It comes in the door square and to size. All i have to do is start machining. If you need something harder use 17-4 SS hardened to H900.

 

www.diehlsteel.com