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powder coating scraped and fit parts?

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Ski

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#1
Hi ,I thought I would ask this question here. I have been restoring a 13" south bend and have been using powder coat on many parts. I have not used it on any scraped in parts. I am considering powder coating the tailstock [not the base] the gear box case and the apron housing. I would appreciate it if those that do scraping would weigh in on this.
The powder coat process is heat the cleaned part to 350F. to cook out any oils. Cool and coat with powder and heat to 350F. for 20 minutes. All machined areas are taped off as well as drilled and tapped holes ect... . I am concerned that the heat may cause some permanent distortion. I like the powder coat though even if I can only use it on certain areas. Tough stuff. I was thinking that powder coat on these items would be beneficial since these are bumped easily with tooling ,hand tools ect... The gear box is right in front ,apron right on the chip tray ,tail stock is right up there as well. all easily chipped, scratched ect. Recognizing this is a machine tool and this will happen, my intent is to minimize damage.Ski
 

astjp2

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#2
I would not do anything on a machine that requires that kind of heat unless its a stress relief process. Tim
 

Ski

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#3
I would not do anything on a machine that requires that kind of heat unless its a stress relief process. Tim
Thank you Tim, I apreciate your comments .Ski
 

kadams4458

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#4
I am just a new guy here, but I actually have years of experience powder coating machined aluminum, pot metal, and cast iron machine components, so I will leave my two cents on the subject here. I am more than happy to share my knowledge and experience on the subject of powder coating.

Aluminum castings and pot metal stuff are actually the trickiest parts to not mess up. (Yep, I killed a few of them in the beginning.) Old properly seasoned cast iron pieces are actually fairly forgiving of the process, provided they are properly supported during the heating process, and most importantly, they are brought up to temp slowly and cooled back down even slower. Modern day powders that are overbake stable make this possible. High production powder coat shops, however won't typically want to take the time to do it.

Ideally, machining and scraping happens after coating, but I have had pretty good luck luck coating everything from Powermatic drill press head castings to Delta table saw tops to engine cylinder heads with no warping. That said, a lathe bed might give me pause, but nothing about any other part of a lathe would likely worry me.

The only cast iron/cast steel component that ever warped on me during coating was a Harbor Freight drill press vice that a guy insisted he wanted coated to match the rest of his old american-made drill press, despite my resistance. Somehow I don't think that casting was seasoned for very long between casting and machining.
 
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Ski

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#5
I am just a new guy here, but I actually have years of experience powder coating machined aluminum, pot metal, and cast iron machine components, so I will leave my two cents on the subject here. I am more than happy to share my knowledge and experience on the subject of powder coating.

Aluminum castings and pot metal stuff are actually the trickiest parts to not mess up. (Yep, I killed a few of them in the beginning.) Old properly seasoned cast iron pieces are actually fairly forgiving of the process, provided they are properly supported during the heating process, and most importantly, they are brought up to temp slowly and cooled back down even slower. Modern day powders that are overbake stable make this possible. High production powder coat shops, however won't typically want to take the time to do it.

Ideally, machining and scraping happens after coating, but I have had pretty good luck luck coating everything from Powermatic drill press head castings to Delta table saw tops to engine cylinder heads with no warping. That said, a lathe bed might give me pause, but nothing about any other part of a lathe would likely worry me.

The only cast iron/cast steel component that ever warped on me during coating was a Harbor Freight drill press vice that a guy insisted he wanted coated to match the rest of his old american-made drill press, despite my resistance. Somehow I don't think that casting was seasoned for very long between casting and machining.
Can you elaborate a bit on what you mean by "properly supported " ? My cousins method hangs the part in a 6 foot oven. The parts I am talking about is the twin shifter gear box iron case or body as well as the iron apron. These are disassembled and of 1978 assembly date. I would guess South Bend did season Iron parts as well. Ski
 

12bolts

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#6
Heat treating of cast iron occurs in the 800-1000 C for hardening and tempering.
Stress relieving is achieved around the 600 C mark
Cast Iron is renowned for its stability and ability to be repeatiably heated and cooled and still maintain dimensional stabilty. I would have no doubt that CI could be safely taken to 150-160 C without any issues.

Cheers Phil
 

Ski

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#7
Heat treating of cast iron occurs in the 800-1000 C for hardening and tempering.
Stress relieving is achieved around the 600 C mark
Cast Iron is renowned for its stability and ability to be repeatiably heated and cooled and still maintain dimensional stabilty. I would have no doubt that CI could be safely taken to 150-160 C without any issues.

Cheers Phil
Thank you for the input Phil !
 

vtcnc

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#8
We have grey cast iron parts powder coated after machining in a production run environment. We have never had any issues with fit or dimensional tolerances in post cool-down.
 

Inflight

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#9
I powder coated my lathe's compound, cross slide, carriage, tailstock (including base) over 8 years ago and it's worked out very well. My oven is lot large enough for the bed or the headstock, so those are hand painted and have since chipped.
 

4gsr

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#10
12bolts is right. You have to get up above 900 degree F. before distorting cast iron. And even then, your not going to distort CI unless it was never seasoned in the beginning. This applies to machine tool components like the beds, tables, compounds, cross slides, etc.
 
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