reamer question

[tk]

I have a Gingery lathe I built many years ago and I have been able to do pretty accurate work including boring. In order to make things a little easier I have been trying to (for the first time) use a reamer to finsh bored holes. I believe that I am doing everything the way the textbooks describe. I put the reamer against the 60 degree tailstock ram and then advance it into the bored hole. However, I always end up with a straight hole, but it's always oversized by the time I get done. The tailstock lines up with the turning center of the headstock (according to my test bar). What could I be doing wrong? Thank-you!

 

[aonemarine]

Put a DTI on the headstock spindle and check the tail stock alignment. That way you can see if the height of the tail stock is dead on. You say your teaming a bored hole, not drilled correct? If drilled drill 1/32 under then ream twice in 64th incroments to the finished size. Helps with drilled holes...

 

[chrsbrbnk]

the reamer may be over sized there are a couple brands we just quit buying at work because of that always reaming large. a cutting fluid helps lots of it if pulling the reamer out to clear chips make sure it dosen't catch a chip under a flute and sorta shim itself out low rpm helps say like 1/10 the drilling speed and luck helps too

 

[tk]

I didn't expect such quick responses! They sound like they are based on a lot of experience too.
Should I be pulling the reamer out periodically in order to clear chips?
Thanks again!

 

[chrsbrbnk]

you can, or need to sometimes but there is a risk of the cutter messing up mor so with a reamer thats running out in the chuck

 

[Tin Falcon]

I used to work in a precision grinding shop . so we were used to working in close tolerances.

getting truly accurate sized holes take experience and possibly experimentation .
speed , feed material and lubricant used, sharpness of the tool. can all effect the size.

Tin

 

[goldstar31]

Two issues arise( in addition to those given)

The first is that a hand reamer is not the most desirable of tools and a machine reamer is recommended. Again, the reamer will be- or was when new -oversize and there cannot cut to nominal size.

Others may have their own opinions.

 

[cheepo45]

Try drilling or boring the hole within .007-.010 of the finished size. The less material you remove, the better chance you have of the reamer cutting on size.
cheepo45

 

[tk]

I will try these things. I have indeed been using hand reamers in the lathe for this and they are basically new. Whether I need to solve a basic problem or I need to get the hang of something here I expect it to finally be pretty useful. Hopefully, my head will soon stop hurting from beating it on the wall! Thank-you all again!

 

[goldstar31]

What I was trying to get over was the fact that you will always cut 'oversize' depending on just how well you use a new hand reamer. Initially, you cut a taper but at the end you are always cutting oversize. I'm sorry but that is how I was given to understand the problem.

Frankly, if I was boring parallel tight enough for an almost interference fit, I have used an inline boring bar.

Others may differ. However, I have a full set of imperial hand reamers up to 1" and that is MY approach.

 

[MachineTom]

No one asked so I will, How fast was the spindle turning when you reamed, Likely way to fast. I to sometimes use hand reamers rather than machine reamers. The only difference between them is the lead on a hand reamer is about 1 x D, and a machine reamer the lead is 1/4 x D. The lead is a tapered portion of the reamer to help get it centered and straight.

If turning too fast the flutes tend to open the hole up from the flexing of th reamer, If chips are clogging the flutes, even more rubbing. Think how fast you can turn the reamer by hand that is the kind of speed to aim for, even 2 or 3X that speed. Small machines as a group are way to fast for reaming. Just lock the spindle and do it by hand.

 

[tk]

I was turning the work with a hand crank I made - so, very slowly, because I didn't know you could use hand-reamers under power. I have tried several times but I have not used any more lubricant than I use for tapping.
Goldstar31 - I don't quite understand, are you saying that from your experience with a large set of imperial reamers that you don't recommend using them and bore it out instead?
Thank-you all for the continued advice!

 

[jgedde]

I had a similar problem. Turns out it was the reamers.

A high grade reamer always cut on size, the cheapies always cut oversize. Turns out the flutes were cut unevenly. I was able to fix them with a stone.

Also, technique plays a big part... Feeds and speeds, use of a lubricant, the initial hole size, etc.

John

 

[MachineTom]

Not sure to whom you directed you question TK. I have a mix of hand and machine reamers. Nothing wrong with using hand reamers under power, as my machines can turn slow enough.

Since your hand cranking your reamer, I would lean towards chip packing or poor sizing of the reamer. Try reaming a piece of similar scrap with a starting hole size of reamer -.020, -.010 and check the results. For that you can figure process or tool for the cause of the oversize.

 

[Larry S]

How are you measuring the size of the reamed hole to know it's oversize ?
and how much oversize ?
Larry S
Fort Wayne, IN

 

[tk]

Larry S, I'm usng a a dial caliper (Sterret), and it's off by varying amounts - a few thousandths.

 

[Larry S]

A Dial Caliper (inside measure) is not a good way to get an accurate
measurement of the diameter of a hole. How accurate does the hole
need to be ? I wouldn't bet that you could get an ID dimension of
the hole to less than 2 thou either way. Also since the jaws of the caliper are not rounded you would get an automatic error there. I know, the Inside jaws
are pretty narrow but there is a flat there.
For my application I always use Chucking Reamers to drill "Precision Dowel"
holes of nominal 1/4" diam. Now the specs on the hardened steel dowels
call for minus 0, plus 0.0003". So that's between exact 0.2500" and 0.2503".
Sometimes a dowel is a slip fit up to pretty snug. Every once in awhile I get a dowel that has to be hammered in. That's too tight as I need
a snug sliding fit for adjustment. So I have to hammer that too tight dowel
all the way through and replace with another one.
When I mic that dowel it will be 4 or 5 tenths over 0.2500".
So 1 or 2 tenths over spec. is way too tight. That's a pretty small tolerance.
Those are US made Holokrome Dowel pins. If I use the Brighton Best imports
I have to toss out about a 4th of the pins as out of spec. Either too big or too small.
I used to think that my reamed holes were screwed up but finally realized that
it was the dowels (cheap imports) that were fubar.

As to what your exact problem with the reamer is I can't really tell. With
a reamer you should get the same sized hole each time. Not a range of a few
thou. That's why I asked how you were measuring the reamed hole

Larry S

 

[robcas631]

Tailstock alignment is key for a great many issues.

 

[tornitore45]

Boring is a far superior operation than reaming, it guarantee round hoel on axix.

If you have bored the hole, why don't you keep boring to size instead of reaming?

A caliper is nor sufficiently accurate to detect an oversize reamer, assuming we are talkind about 0.0002 to 0.0005.

 

[goldstar31]

A Between Centres Boring Bar will create a bore which is parallel and concentric-- regardless of the alignment of the tailstock.

What seems to be appearing is the wrong use of a hand reamer which is better suited to a task away from the refinements and inherent accuracy of the lathe.

Others are welcome to disagree.