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Boring Delrin Bushing

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Kroll

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#1
Guys I installed a Delrin bushing in my pulley so now I need to bore it to size.Right now its about 1 1/4 so the opening is kinda small.I do have boring bars but they take inserts.This being some kind of plastic I figure the tool has to be real sharp so that would be HSS.Well I don't have a boring bar for HSS so what do I need to look for in boring bar and since this is a small opening I guess the cutting tool also needs to be small.Would that be say 1/4 x 1/4 HSS and a bar that is made for this size cutting tool?If you have any ideals and links to what I need please let me know.I have purchase from Shars before and they seem to have good prices,maybe something is there?Thanks guys
 

magicniner

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#2
You can use one flute on a HSS endmill, just think of it as a boring tool and set the flute edge horizontal and at the right height.
 

WarrenP

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#3
You didnt say how big the hole is your boring, but....I have this hss boring bar which works well on small diameter holes, the bar is 3/8" with a 1/8" blade. I just cut the hss blade down on one side so it doesn't stick out of the opposite end to have clearance. ($10.95).
http://www.grizzly.com/products/Double-Ended-Boring-Bar-4-1-2-/H2996
 
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RJSakowski

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#4
If the hole depth isn't too great, a boring bar can be made from a broken tap or a drill bit. For boring Delrin, you could probably get by with mild steel rod. An old rat tail or triangular file can be modified as well.
 

derf

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#5
I bore delrin all the time with carbide inserts, no problems.
 

benmychree

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#6
There are not tricks to bore Delrin, it works easily and with good finish, the tool, of whatever type should be sharp and with a small corner radius. Delrin is about the easiest plastic to work with, no stringy chips ----
 

Kroll

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#7
Thanks guys,I wanted to ask this bushing cost me 76.00 so that kinda makes me nervous.But reading all the replys I will look around find something that can grind a sharp edge.
 

jonesn7

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#8
I've used old Allen keys to make small boring bars with good success. Just grind it down to what you need. No need to heat treat for Delrin.
 

Tozguy

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#9
I would buy the largest cement nail that will fit the bill and grind the head for boring plastic.
Cement nails are very stiff. You can get an amazingly sharp edge on cement nails that is tough as .........nails.
 

homebrewed

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#10
"You can use one flute on a HSS endmill, just think of it as a boring tool and set the flute edge horizontal and at the right height."

I have used this approach as well when my standard boring bars were too big for the hole I wanted to bore out. I've used the method on brass, aluminum and plastic with good results. I was concerned that the large positive rake would be a problem with brass (which has a tendency to self-feed in some circumstances), but no problems so far.
 

Kroll

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#11
Guys tomorrow going to give it a try using an end mill.For some reason I have couple that came in a box yrs ago at estate sale
 

Kroll

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#12
Guys,I tried to find something that I could bore the bushing but have nothing that is long enough to bore 2".So I tried my Shars boring bar which the insert is kinda rolled down some so guessing this makes the tip of the insert more of a negative than being at 0.I am trying an insert that is for fine finish for steel but its just not doing the job.Seems like its just riding on the surface instead of cutting.I just don't have anything that will work so that leaves me with shopping.Which I really didn't want to spend more money but if I destroy this bushing then there goes 76.00 plus alot of time.Guys would it be possible for someone to point me toward correct boring bar or what is needed to bore out say 2"-2.5" dept and get a smooth finish?This pulley has to slide up/down on shaft which is for a BP.Oh guys is it normal for boring bars such as this one from Shars to have the insert rolled downward?The bar itself has 4 flat areas that fits in the tool holder IMG_0523.jpg
 

markba633csi

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#13
You can also use the edge of a sharp drill bit as a boring bar- I've done it several times in a pinch. You need to set the cutting edge a bit above center for it to cut well. I wouldn't try it for steel, but for cutting aluminum and plastics it works fine. Takes a little experimenting and adjusting but it works. Try about a 5/16" or 3/8" size drill; place it at an angle approximately like the picture above, take light cuts
mark
 

Kroll

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#14
Yahooooo! It work,Plan C did the trick using the file.I don't know if this is what ya'll talking about but it work.The blue pieces I just set up there for pictures.Guys it also fits the shaft,guys if ya'll will if this is not what talking about please explain how I should do for the next time.
IMG_0524.jpg IMG_0525.jpg
 

markba633csi

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#15
Any port in a storm :) glad you got it done by hook or by crook (or by file)
 

Kroll

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#16
Mark I did look to see if I had any drill bits that were long enough but that ideal come up short.But next time I come across some long drill bits at garage sale I will not pass them up.
 

Profkanz

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#18
Guys,I tried to find something that I could bore the bushing but have nothing that is long enough to bore 2".So I tried my Shars boring bar which the insert is kinda rolled down some so guessing this makes the tip of the insert more of a negative than being at 0.I am trying an insert that is for fine finish for steel but its just not doing the job.Seems like its just riding on the surface instead of cutting.I just don't have anything that will work so that leaves me with shopping.Which I really didn't want to spend more money but if I destroy this bushing then there goes 76.00 plus alot of time.Guys would it be possible for someone to point me toward correct boring bar or what is needed to bore out say 2"-2.5" dept and get a smooth finish?This pulley has to slide up/down on shaft which is for a BP.Oh guys is it normal for boring bars such as this one from Shars to have the insert rolled downward?The bar itself has 4 flat areas that fits in the tool holder View attachment 277493
With a thicker carbide insert yes it's normal for the insert to be rolled down like that. It provides the additional bottom clearance for the bore.
 

BaronJ

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#19
Guys,I tried to find something that I could bore the bushing but have nothing that is long enough to bore 2".So I tried my Shars boring bar which the insert is kinda rolled down some so guessing this makes the tip of the insert more of a negative than being at 0.I am trying an insert that is for fine finish for steel but its just not doing the job.Seems like its just riding on the surface instead of cutting.I just don't have anything that will work so that leaves me with shopping.Which I really didn't want to spend more money but if I destroy this bushing then there goes 76.00 plus alot of time.Guys would it be possible for someone to point me toward correct boring bar or what is needed to bore out say 2"-2.5" dept and get a smooth finish?This pulley has to slide up/down on shaft which is for a BP.Oh guys is it normal for boring bars such as this one from Shars to have the insert rolled downward?The bar itself has 4 flat areas that fits in the tool holder View attachment 277493
Good grief, is that what they are charging for those bushings !
I would have bought some thick wall Delrin tube and machined it to suit. I know plastics have taken a jump in price, but for that money you could have 10 feet of tube. Plenty to make mistakes with.

Anyway, congratulations on a job well done !:eagerness:
 
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