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PostPosted: April 16, 2018, 9:42 pm 
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Hi all,

I've poured through the forum, bookmarking, researching, reading. One of the biggest concerns I've had for this whole project is the steering rack.

I dove in today, finally. I've put it off but now need to get it done to keep moving forward. Measured the optimum rack length if I mount it at a similar height to the original Haynes plan, and came up with removing 127mm. I sectioned the housing and I'm happy with how that turned out. I also welded up the remaining power steering feed (one was taken out with the section) and it looks like it was made that way.

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Now that I'm at the rack, I have a decision to make. Which brings me to questions!

The old method was to section the rack, which obviously introduces the threat of warping. So I've read a few more threads that showed a couple of folks who just cut the length needed off the non-toothed end and tapped for the tie rod. It seems they are not rolled threads from the factory, but cut. So it really seems like that would be the safer way to go...

A couple questions though:

Do I need the chamfer/smaller diameter at the end of the rack as pictured below (first shot is the entire rack for reference, then the non-toothed end with the reduced diameter end in question)?

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Second, I've seen different numbers for which is the correct tap. I have an M18x1.5, and I know that isn't right. Can someone say for sure what the correct tap is (I am using a 1993 power steering rack if that matters)?

Finally, does anyone have any reason not to just cut off the total length reduction and tap rather than section?

THANK YOU FOR YOUR TIMELY HELP!!

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PostPosted: April 17, 2018, 12:35 am 
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One of the above questions solved - hopefully it helps someone!

Power Steering model Miata racks use an M17x1.0 for the inner tie rod.

Manual model Miata racks use an M18x1.5 for the inner tie rod.

Still need help with the rest!!

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PostPosted: April 17, 2018, 1:09 am 
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Location: BC, Canada. eh?
If it helps, I had my rack cut & the free end re-tapped, and it came out great. I had a machine shop do the 4.5" cut & thread, as I didn't have a lathe at the time.

The beauty of it was that, being lathe cut, the new end threads are absolutely perfectly concentric, which can be an issue when using a tapping die (it's easy to be a bit off, and end up with slightly deeper threads on one side than the other).

I had the housing sectioned on the lathe as well, & TIG welded, as my housing (it's a GM unit from a Chevette) is aluminum. The end product is a flawless rack assembly which looks like it came from the factory this way.

I agree that sectioning the rack itself might be inadvisable due to the possibility of warping, crystallization, etc. Not ideal on a critical item like a steering rack :shock:

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PostPosted: April 17, 2018, 11:34 am 
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I shortened an RX-7 rack so things may be a bit different. I simply cut off the end with an cutoff wheel, drilled a clearance hole following the hollow center already there using a hand drill, and manually tapped that new hole. I had absolutely no issues by doing it myself in my shed (garage). YMMV but not by much I would presume.

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Last edited by rx7locost on April 17, 2018, 6:58 pm, edited 1 time in total.

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PostPosted: April 17, 2018, 6:48 pm 
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Piece of cake. I was very intimidated during the researching phase but it all was a very easy process after I made the first cut. Pictures at the bottom of page two of my build. http://www.locostusa.com/forums/viewtopic.php?f=35&t=7370&start=15

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PostPosted: April 17, 2018, 8:18 pm 
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Thanks! More info on the "cut and hand ground" the end to accept the locking washer from the inner tie rod. How did you do that? Which tools, methods, etc...

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PostPosted: April 17, 2018, 10:15 pm 
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RandyBMC wrote:
Thanks! More info on the "cut and hand ground" the end to accept the locking washer from the inner tie rod. How did you do that? Which tools, methods, etc...


It's been a few years but no special tools other than a bench grinder and a set of hand files. If I remember correctly I just hand held the shaft and rotated it against the grinder wheel until I got to the same diameter as the stock end. Slow and steady and you'll be there before you know it. Hand file the slots to the same dimensions as the stock end. All it has to do is accept the lock ring. Focus you worries on getting the housing (I use the cut-out section to practice) welded up square and retapping the threads. Spend the money and/or borrow a good tap to cut the threads. Not the time or place to use your Harbor Freight tap and die set.

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PostPosted: April 17, 2018, 11:52 pm 
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jaf wrote:
Spend the money and/or borrow a good tap to cut the threads. Not the time or place to use your Harbor Freight tap and die set.


Boy I'll second that! I tried tapping with a $9 tap, was good for about 5 threads then I could 'feel' the tap starting to twist instead of cutting. Went and bought a $30 tap, what a difference, cut the rest of the threads like going through butter.

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PostPosted: April 18, 2018, 9:38 am 
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Thanks again guys. I have the housing done - used the rack and slug to keep things centered in a piece of angle. Perfect!

I've ordered the tap from drill and cutters as well as a tap level - pretty cool piece - to be sure it is straight.

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PostPosted: April 18, 2018, 9:41 am 
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On a slightly different but related topic, how high did you mount the rack, and what distance from the front did you mount it - in other words, what dimensions did you come up with for the mount? I obviously have the Haynes measurements, but that is for using the Sierra hub, not the MX5. Thanks in advance for the outstanding support (see what I did there - support, like the rack support :D )!!!

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PostPosted: April 18, 2018, 2:26 pm 
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Location: BC, Canada. eh?
I'm picturing "rack support", as we speak!! :twisted: :P :cheers:

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PostPosted: April 18, 2018, 2:53 pm 
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zetec7 wrote:
I'm picturing "rack support", as we speak!! :twisted: :P :cheers:

What dimensions are yours? :cheers:

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PostPosted: April 18, 2018, 10:31 pm 
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:cheers: :lol:

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PostPosted: April 19, 2018, 8:08 am 
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zetec7 wrote:
I'm picturing "rack support", as we speak!! :twisted: :P :cheers:
Attachment:
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Bra Design.jpg [ 37.35 KiB | Viewed 833 times ]
Are your thoughts wandering in this ^ direction, or is it just me?

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PostPosted: April 19, 2018, 8:21 am 
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