I hate reamers!

[Mike Stevenson]

OSM,

I think the bent reamers come from cheap tool companies baiting and switching your tools with cheap crap and guys in your shop who bend them and then throw them back in the box with the good ones.

[little bubba]

Take a ball bearing of something roundish and larger than your hole, place it over the hole and give it a whack with a hammer. This should peen the edges in a little bit and should hold your dowel pin no problem.

I'll one up your trick, run a form tap down the hole(not my idea, came from a forum). A .187 I do believe is a #10. It will support your dowel the entire way down the hole, not just at the top.

For the record, I only use this in house on fixtures that require press and slips, I only need to find and use one reamer to get the press and the slip. Parts that go out would never ever receive this treatment.

[Mike Stevenson]

Bubba,

That's new to me but I will try anything once.

[shawncnelson]

Here's what has worked for me:
1. Make sure the collet is the correct size, if the reamer has a reduced shank, you might want to try one size smaller collet.
2. Extend the reamer out as far as you can, only chuck on as much as is needed.
3. Place the indicator as far down the shank as you can, just above the flutes. It also helps me to place the indicator on the "front" side of the reamer, facing me.
4. Instead of the hammer method, try gently pulling the reamer while the indicator is still on the shank, this will let you watch the results.

[Mike Stevenson]

The bottom line is reaming is always a finesse thing. Dependant on the tool's runout, the pressure difference between the undersized drill hole and the reamer, and the feeds and speeds used. But once it does work it will continue to work repeatedly.

[handlewanker]

The biggest problem with a reamer is that it will FOLLOW an existing drilled hole.

When you have a close tolerence location for a hole position, then it is bored not reamed.

Like I said before, a reamer is a production tool that cuts time when producing holes to the same dimension in multiple items.

Unless you're allowing the reamer to "float" as it penetrates, it will be influenced by the rigidity of the spindle, which will hold it in a straight line, and the position of the drilled hole which could be off centre.

You cannot produce accurate work with methods that were designed to save time.

That you CAN make an accurate reamed hole is up to the skill of the user.

For dowel holes where the dowel has to be a tight fit in the one part with the other part mated to it and a slight clearance, I use a hand reamer, but in the machine.

A hand reamer has about 1/4 of its length tapered to make it easier to get it started in a hole by hand.

If you ream the hole nearly to the bottom then when the dowel is knocked in it will lock tight on the last bit which is tapered, otherwise if you ream with an undersized reamer all the way for a press fit there is a danger that the dowel will start at an angle as it enters the hole and raises a burr on one side.

I allow a maximum of .010" per inch of diam for a reamed hole, which means for a 1/4" hole it has .002" undersize.

As a tradesman I always had a set of reamers in my box that I kept and maintained so that I always knew what I was working with.

One of the best reamers I came across was the David Brown type of reamer, that had two floating and adjustable blades, usually carbide tipped but not always, and these I swore by for many years.

They would produce mirror finish holes in Mehanite cast iron consistently.

The whole business of reamed holes is a combination of machine/holder/tool/user, and the factors that influence the end product occur in each one.

Anyone make "D" bit reamers?
Not hard to do, but it takes a bit of explaining if you've never seen or used one.
Ian.

[shawncnelson]

You cannot produce accurate work with methods that were designed to save time.

I guess this explains why cnc machines produce so much inaccurate work.

[Mike Stevenson]

LOL

[dertsap]

when it comes to tight positional tolerances handlewanker is absolutely correct , reamers would be worthless , so are many typical lower end cnc production machines for that matter , boring heads are the thing to be using for such applications ,and in extreme cases many times probing and a recently tweaked and adjusted machine are an absolute must to uphold positional tolerances within .0003 or better on multiple bores

[Larry83301]

My $0.02 --- I've reamed many a hole with reamers held solid in tool holders. We used the DRILL, BORE, REAM method on anything that had to be close. Drill .01 under, Bore .002 under finish size, and ream whatever you want, slip or press fit. We used this in all types of material and never had a problem. Holes in Aerospace parts need to be right, thats what our inspectors told us. LOL

Larry83301

[shawncnelson]

when it comes to tight positional tolerances handlewanker is absolutely correct , reamers would be worthless , so are many typical lower end cnc production machines for that matter , boring heads are the thing to be using for such applications ,and in extreme cases many times probing and a recently tweaked and adjusted machine are an absolute must to uphold positional tolerances within .0003 or better on multiple bores

Read the original post fellas, he says nothing about positional accuracy being a problem, only hole size. Furthermore, the center drill-pilot drill-ream method will give you hole location AND size results at least as good as your boring head, given the size he's talking about (.1875).

[dertsap]

I guess this explains why cnc machines produce so much inaccurate work.

then what was the point of saying this

i was just stickin up for handlewanker

[Mike Stevenson]

Actually it's Center Drill, Drill, Ream, Bore for geometric hole perfection. When you center drill your position it's perfect at the top of the hole. If for any reason the drill walks or creates an out of round hole you do not have a good true position hole. The reamer fixes the roundness but has no choice but to follow the drill hole. It is the Boring head which cuts the hole to its final size and makes it perfectly round, straight and perpendicular to the fixture or machine table. With it's single point cutting it's exactly like boring on a lathe.

[dertsap]

, the center drill-pilot drill-ream method will give you hole location AND size results at least as good as your boring head, given the size he's talking about (.1875).

the hole will wander to a certain extent , it will not be near as accurate as a boring head

[Mike Stevenson]

Exactly.

[shawncnelson]

He was asking about hole size!!! NOT LOCATION!!! Focus people.

[Mike Stevenson]

Originaly posted by shawncnelson
He was asking about hole size!!! NOT LOCATION!!! Focus people.

Take it easy. Sometimes threads take a change for the better or worse. But we are all talking about a related subject.

[dertsap]

, the center drill-pilot drill-ream method will give you hole location AND size (.1875).

????

you said it ?

its just nice to look at things from all angles and prespectives sometimes thats all

[robclemson]

Does anyone know any kind of lathe equipment that I can use for small size graphite part turning ?

[shawncnelson]

Take it easy. Sometimes threads take a change for the better or worse. But we are all talking about a related subject.

Fair enough. Just trying to address the original question, which was about reamer run-out and over-sized holes. Almost every post after that solved the not-mentioned problem of hole position.