Need Info On Reamers

Have you tried this style of adjustable reamer in polyethylene?

Adjustable reamers can be preset to any size, thus allowing for any amount
of spring back. You can start by adjusting it to slightly polish a drilled
hole, and just keep adjusting it out, and making additional passes unitl you
get what you want.

If he is trying to hold .002" oversize, an oversized drill is going to be
much less predictable, probably more difficult to find and a good bit more
expensive.

I'll be the first to admit, I don't recall ever using one in polyethylene -
but I have used them with good results in delrin.


"Cy Galley" wrote in message
news:ArVsh.1152041$084.63830@attbi_s22...
Reamers as another said just don't work on these self-lubing plastics. It
just pushes away and then springs back. Sharp over size drills some times
work.



"Maxwell" wrote in message
...

"DonMorrisey" wrote in message
oups.com...
I'm trying to figure out how and where to buy reamers. I need to
create some 5/8" and 1/2" holes in ultra high molecular weight
polyethylene blocks for my control system. The aileron push tubes
slide thorugh the blocks and the aileron actuators mount in the blocks
as well. The mounting component of my aileron actuator is 5/8", so
when buying the .6250" reamer is that already slightly oversized? I
have been told the holes should be oversized by .002". I have looked
for reamers on line but don't know if what I'm buying is the right
size, there is little or no description for them.

Can someone tell me what I should look for in buying these tools and
where may be the best place to do so?

Thanks. Don


You might want to consider adjustable reamers Don.

http://wttool.resultspage.com/search...eamers&x=0&y=0

If the long link won't work, just go to http://www.wttool.com/ and do a
search on adjustable reamers.

"Maxwell" wrote

If he is trying to hold .002" oversize, an oversized drill is going to be
much less predictable, probably more difficult to find and a good bit more
expensive.

The key is the type of bit he is advocating dressing and using.

A wood cutting Forsner style drill bit eliminates any possible springback,
as it cuts only on a straight line from the center to the diameter, and
pretty much level across the hole. It has no flutes to try to dress, and a
small area to dress. It is the ideal bit to re-size.
--
Jim in NC

"Morgans" wrote in message
...

"Maxwell" wrote

If he is trying to hold .002" oversize, an oversized drill is going to be
much less predictable, probably more difficult to find and a good bit
more expensive.

The key is the type of bit he is advocating dressing and using.

A wood cutting Forsner style drill bit eliminates any possible springback,
as it cuts only on a straight line from the center to the diameter, and
pretty much level across the hole. It has no flutes to try to dress, and
a small area to dress. It is the ideal bit to re-size.
--
Jim in NC

He didn't say what type of drill bit, and forstner bits do not eliminate any
possibility of spring back, try drilling rubber or felt.

Also, how do you easily resize a forstner bit? Are you sure the others are
not talking
about spade drills?

DonMorrisey wrote:
I'm trying to figure out how and where to buy reamers. I need to
create some 5/8" and 1/2" holes in ultra high molecular weight
polyethylene blocks for my control system. The aileron push tubes
slide thorugh the blocks and the aileron actuators mount in the blocks
as well. The mounting component of my aileron actuator is 5/8", so
when buying the .6250" reamer is that already slightly oversized? I
have been told the holes should be oversized by .002". I have looked
for reamers on line but don't know if what I'm buying is the right
size, there is little or no description for them.

Can someone tell me what I should look for in buying these tools and
where may be the best place to do so?

Thanks. Don

I'd try drilling the holes with the nominal size drills & then touching
them up with some sandpaper on a dowel..

On 20 Jan 2007 18:40:24 -0800, "DonMorrisey"
wrote:

I'm trying to figure out how and where to buy reamers. I need to
create some 5/8" and 1/2" holes in ultra high molecular weight
polyethylene blocks for my control system. The aileron push tubes
slide thorugh the blocks and the aileron actuators mount in the blocks
as well. The mounting component of my aileron actuator is 5/8", so
when buying the .6250" reamer is that already slightly oversized? I
have been told the holes should be oversized by .002". I have looked
for reamers on line but don't know if what I'm buying is the right
size, there is little or no description for them.

Can someone tell me what I should look for in buying these tools and
where may be the best place to do so?

Don, you've already had others say what I'll say, but hole sizes in
UHMW have not, in my experience, matched drill or reamer sizes very
closely as contrasted to metals. It has been my experience, as well,
that taking 0.005 out via reaming UHMW gives a different size hole
than taking 0.030 out. I'm with the camp who suggest adjustable
reamers if you feel the need to ream, otherwise, use a drill and be a
little oversize. Remember that the expansion of materials is
different, binding would not be a good thing.

I'd definitely pre-ream(drill) to a specific size before finish
reaming(drilling). I'd run the tool very slowly and "lube" with only
compressed air.

"GeorgeB" wrote in message
...
On 20 Jan 2007 18:40:24 -0800, "DonMorrisey"
wrote:
...
little oversize. Remember that the expansion of materials is
different, binding would not be a good thing.


Would you then suggest that it would be a good idea to test the fit of the
sample parts after the plastic and aluminum have spent the night in the
deep-freeze and again after a couple hours in a 150 F. oven (about how hot
it can get with the sun beating on a closed structure?)?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

DonMorrisey wrote:

I'm trying to figure out how and where to buy reamers. I need to
create some 5/8" and 1/2" holes in ultra high molecular weight
polyethylene blocks for my control system. The aileron push tubes
slide thorugh the blocks and the aileron actuators mount in the blocks
as well. The mounting component of my aileron actuator is 5/8", so
when buying the .6250" reamer is that already slightly oversized? I
have been told the holes should be oversized by .002". I have looked
for reamers on line but don't know if what I'm buying is the right
size, there is little or no description for them.

Remember polyethylene blocks may creep under load.
You need some clearance between hole and tube. I don't think you kneed
to buy a reamer, a new drill will do the job with proper clearance.


By
--
Pub: http://www.slowfood.fr/france
Philippe Vessaire Ò¿Ó¬

"Philippe Vessaire" wrote

Remember polyethylene blocks may creep under load.
You need some clearance between hole and tube. I don't think you kneed
to buy a reamer, a new drill will do the job with proper clearance.

To OP: was there a +/- type of allowable clearance given, as a recommended
range?

It would seem like a necessary range of fits would have to be given. As
this poster pointed out, the coefficients of expansion for these two
different materials would be wildly different, and the clearances would have
to change for the temperature spread an aircraft would be subjected to.

I agree that a freezer/oven test needs to happen, and clearances measured,
or at least calculated clearances for the different temperatures.

Anyone got a favorite source for materials expansion coefficients?
--
Jim in NC

To OP: was there a +/- type of allowable clearance given, as a recommended
range?


Jim, it was suggested that I oversize the hole by .002. There is great
information in this post and I thank everyone for contributing.

Don.

I have had great results drilling UHMWPE with wood workers Forstner bits.
Just as with wood, these bits cut holes with very straight, smooth sides in
UHMWPE. OTOH, metal twist drills tend to push material aside which then
rebounds to make the hole smaller than the nominal size of the drill. I
replaced the nylon pushrod fairleads in my sailplane with UHMWPE using
Forstner bits to drill the holes slightly bigger than the pushrod OD.

Bill Daniels

"DonMorrisey" wrote in message
oups.com...

To OP: was there a +/- type of allowable clearance given, as a
recommended
range?


Jim, it was suggested that I oversize the hole by .002. There is great
information in this post and I thank everyone for contributing.

Don.