stem is in

Questions and comments about converting to beefier forks..
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KDX220PHIL
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Post by KDX220PHIL »

It would be possible to use something called a forming tap.

A forming tap is used like a regular tap, but instead of cutting material it displaces it. There may be forming taps available that are close to the required size, just enough to displace the material in the TT, instead of knurling the stem.

The one on the right is a forming tap, the other is a cutting tap:
http://www.thefabricator.com/Articles/P ... 7/Fig1.jpg

Anyone know the approx. hole size, and the approx. stem size for some of the setups, I can check on the taps, I may have the right sizes.
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Post by Green Hornet »

The Diehead looks like the thing a ma jig that they bore tunnels with
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Post by KDX220PHIL »

Best of all, anyone can use it with a tap wrench, oil, and little muscular persuasion.
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Post by canyncarvr »

The forming tap will put the impressions in oriented to the wrong axis. They should be parallel to the axis of insertion of the stem.

Well, imo and all.

Yeah. Easily argued the other way I suppose. As I said...imo and all.

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Post by KDX220PHIL »

Why must they be colinear to the axis? I personnaly wouldn't use this method anyway but i was thinking in terms of options for the modifiers.

What would be wrong with using a diamond shaped pattern for knurling, why was straight used? Is there any advantage/disadvantage, can dirt and water enter the edges of the stem? If so maybe a diamond pattern would be better?
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Post by m0rie »

I don't think it would make any real difference as the knurling is not (AFAIK) what holds the stem in. The c-clip on the stem does that and the nut on the top of the stem. The knurling just keeps it from doing the hoola hoop. Am I completely off base here?
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Post by skipro3 »

The knurling must be lenthwise through the hole and not ribbed so that the stem won't spin on the lower tree. That is the problem: in a crash, the lower tree gets out of alignment with the upper tree. If the stem spun on the lower tree, it would be knocked out of alignment with the upper. Vertical knurling will keep the lower stem from spinning. The clamping action of bolting the whole thing together will keep the stem from migrating back out of it's pressed in hole.
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Post by KDX220PHIL »

I would think that if the stem is pressed in with great force, regardless of the pattern running verticalhorixontaldiagonal, it will have difficulty spinning. Once the stem is pressed in the lower clamp, the material that is touching the stem (the new pressed hole) will be round. How does vertical knurling eliminate rotation?

I like the sound of the "square hole" in the stem that KDX'r was mentionong, I think that is what he said?
A notch in the tree and a hole in the stem would isolate that freedom of motion, no possibility of rotation, of course the stem would have to be oreiented properly when pressed in.
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Post by m0rie »

Trev's stem had a roll pin installed. Seems to be an aussie thing as none of the other people who have done the kx conversion had the roll pin on their stem. A roll pin would certainly keep the stem orientated.
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Post by skipro3 »

Best way I can think of to discribe knurling so the stem won't slip in the clamp is to compare it to a chain and sprocket. A chain could slip sideways off a sprocket but it's not going to be able to skip a tooth. (unless the sproket is VERY worn).

So a knurled clamp should be oriented verticaly; so the stem won't slip or spin in the clamp. The knurls are like the teeth of a sprocket and would prevent spinning but not the action of sliding in and out of the stem to the clamp.
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Post by Indawoods »

I was under the impression the knurling was simply for interference fit. Since the stem is smaller than the bore on the KX clamp.

I really don't think it matters how the knurling is done. I mean if the size was the same on both, nothing but the green loc-tite agent would be used.

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Not all clamps will require this step, check fit before attempting any machining.
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Post by m0rie »

>|<>QBB<
Indawoods wrote:I was under the impression the knurling was simply for interference fit. Since the stem is smaller than the bore on the KX clamp.
This was my general impression as well. If that is truly the case then any type of knurling should be fine.
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Post by KDX220PHIL »

Skipro, did you press a steel stem into an aluminium bore, forcing the knurl to cut the bore? Forming it to the shape of the knurl?

If someone had a steel stem knurled deep and pressed into an aluminium bore than that would do as Skipro mentioned, the opposite would not be true. you could not knurl the clamp and expect the same result due to steel being harder than al.
It also would not work on an Al. stem. Is this what is going on? :shock:
Is the stem being knurled so deep that the grooves are cutting/forming the material in the clamp? Making the parts useless as KX and KDX parts?
I was thinking that the knurl was the weakest material, and was just there to reshape when being pressed in.
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Post by skipro3 »

I had the option of having the stem knurled or the clamp. It was my opinion that if the stem was knurled and being steel, would cut the clamp and form an almost gear/spline type of mating surface. Whereas if the clamp was knurled, it would mash the rises onto the steel stem with enough force to grip the stem without cutting any material at all; just re-forming it. My final decision was to go with the knurled clamp opening and not the stem because the machinist didn't have a knurling tool for a shaft, only for a hole. He used the tool he uses on pistons. (With a piston he knurls the pin holes so that the wrist pin is a tight fit and the wrist pin won't rotate on the piston holes.
If a tool for knurling the stem had been available, I would have gone that way for sure.
Last edited by skipro3 on 02:27 pm Dec 03 2005, edited 1 time in total.
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Post by KDX220PHIL »

With:
Aluminium clamp with ridges,
Steel stem without ridges,

Well, when pushing the stem into the ridged hole, the steel is harder then the aluminium causing the ridges to be pushed away. Aluminium cannot form steel.
Smash a piece of aluminium on a piece of steel ( with both sharing the same charecteristics except weight) and see wich one dents worse.
Same with the piston, if the piston is aluminium and a steel wrist pin is pressed in, the steel will push the aluminium away, the piston will not ridge the pin. This would be evident when the pin was removed. I guarantee if the psiton was aluminium, that steel pin would come out with no scars.
What is happening here is the star-like hole (that now has a smaller minor diameter) is being opened up to the actual size of the shaft, or an interference fit as Inda mentioned.
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Post by skipro3 »

Exactly.

So, which is "better"? The steel stem knurled and carving a spline/gear mating surface, or the aluminum clamp knurled, mashing the two surfaces together for a tight friction grip?
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Post by KDXGarage »

Has anyone who has had his stem or clamp knurled and the KX forks fit, then had it pressed back out? (switching back to KDX forks to sell the bike, etc.) I am curious as to what it looks like afterward.
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Post by KDX220PHIL »

I am not sure wich is better, I believe my KDX might be like KDXR's and have abuilt in rotational restrictor.

Factory, the Clamps do not require knurling to keep them from rotating, so maybe it is not necessary, maybe a pressed fit is adequate. Although from a design stand point of view, I prefer something to lock it in place.

Look in my gallery and you will see some diagrams of what we have been discussing, the knurling of the clamp with the stem pressed in afterwards. I have not figured out how to post pics within the thread yet, so you'll have to go diggin'.
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Post by KDXGarage »

I think Kawasaki has spent a lot more R&D Dollars on this than I could ever dream to, so a press fit sounds great to me. I just follow their lead. :grin:

Sorry for any confusion, but I know the basics of knurling. I am wanting to see the OD of the stem and the ID of the lower clamp after it has been knurled, pressed in, ridden for a while, then pressed back out. I just don't have hands on experience with knurling to see the after effects.

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Post by Indawoods »

That's an expensive experiment....
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