How is this possible.

[Corrado]

Yes....how is this possible?
I have a 4 year old Optimum BF20L Milling Machine with DRO fitted. (Photo attached)
When I set up a job to be milled in the centre of the work such as steam engine ports I will use the DRO with the edge finder ....locate the exact edge & move into the centre of the work with the DRO & mill away.
The problem is that when I use this method for drilling holes it is spot on accurate.......however when I attach the Milling arbor (ER 32) it is .5 mm out on the X axis!!!!
I originally thought I was setting up wrong and have rechecked everything over & over. I have rechecked the diameter of the Edge Finder shank..all ok.
Then when I put the drill chuck back in place...everything is spot on again. What the F##K!
Has anyone here come across this issue?

 

[kadora]

I have the same bf 20 mill and had the same problem then I found Z axis was not perfectly perpendicular to the mill table.so different lenghts of chuck and ER arbor did this problem.

 

[SmithDoor]

Bad news it nothing new.

Dave

Yes....how is this possible?
I have a 4 year old Optimum BF20L Milling Machine with DRO fitted. (Photo attached)
When I set up a job to be milled in the centre of the work such as steam engine ports I will use the DRO with the edge finder ....locate the exact edge & move into the centre of the work with the DRO & mill away.
The problem is that when I use this method for drilling holes it is spot on accurate.......however when I attach the Milling arbor (ER 32) it is .5 mm out on the X axis!!!!
I originally thought I was setting up wrong and have rechecked everything over & over. I have rechecked the diameter of the Edge Finder shank..all ok.
Then when I put the drill chuck back in place...everything is spot on again. What the F##K!
Has anyone here come across this issue?

 

[Corrado]

I have the same bf 20 mill and had the same problem then I found Z axis was not perfectly perpendicular to the mill table.so different lenghts of chuck and ER arbor did this problem.

Hi Kadora,
Did truing up the Z axis resolve the issue?

 

[Chiptosser]

Have you put a travel indicator in the spindle and trammed the head?
Swing the spindle 360 degrees on the table.

 

[kadora]

truing Z axis help me a lot . But I think that tuning Z angle is quite delicate operation because Z angle setting is not solid enough on this mill. I have to check Z angle quite often.
In spite of this I am happy with this mill.

 

[SmithDoor]

I use good old dial indicator.
It works ever time.

Dave

truing Z axis help me a lot . But I think that tuning Z angle is quite delicate operation because Z angle setting is not solid enough on this mill. I have to check Z angle quite often.
In spite of this I am happy with this mill.

 

[Corrado]

Have you put a travel indicator in the spindle and trammed the head?
Swing the spindle 360 degrees on the table.

Chiptosser....you are 100% right.
I Trammed the Head/Table & it was 5.0...yes 5.0 mm out!!

 

[BaronJ]

Hi Corrado, Guys,

I also have a BF20LB clone and have made some mods to it which improves it tremendously !

One of the first things that I did was to make this tool. As you can see here the tram is within 1 thou.

Note: that the tram does vary as you move the head up and down ! But that is mainly due to the rather horrible banana shaped gib strip. Flattening that gib strip out and replacing both locking pins (the ones under the locking screws) removed most of that variation.

I also did the three bolt modification. This not only makes it easier to tram the head but also makes locking the head more secure.

Adding an adjusting screw on each side of the head also improves the ability to set and hold the tram. Once set you can rotate the head and get it back to an almost perfect tram afterwards.

Just in case you don't have the details for the three bolt modification here is the drawing for it. I just glued it to the head and drilled the three holes. The bolts were coach bolts with the heads filed so that they fit into the slot without fouling.

Simple changes that make the mill much nicer to use.

HTH.

 

[goldstar31]

Hi BaronB
Thanks for the jolt.
The Multi position Saddle stop HK1840 from Hemingwaykits is here and I'm trying to make the additional is slowly being attempted.
Oh dear. the precision with this alnost non existent eyesight

If I manage , I will have 6 position stops on the Myford


Cheers

N

 

[BaronJ]

Hi BaronB
Thanks for the jolt.
The Multi position Saddle stop HK1840 from Hemingwaykits is here and I'm trying to make the additional is slowly being attempted.
Oh dear. the precision with this alnost non existent eyesight

If I manage , I will have 6 position stops on the Myford


Cheers

N

Hi Norman, I've sent you a PM.

 

[goldstar31]

Hi Norman, I've sent you a PM.

Many thanks

I hope my reply is Coherent

Keep going

Norman

 

[ajoeiam]

Hi Corrado, Guys,

I also have a BF20LB clone and have made some mods to it which improves it tremendously !

snip

Just in case you don't have the details for the three bolt modification here is the drawing for it. I just glued it to the head and drilled the three holes. The bolts were coach bolts with the heads filed so that they fit into the slot without fouling.

Simple changes that make the mill much nicer to use.

HTH.

I don't recognize the term 'coach bolts' - - - - - - a pic would be useful.
(Guessing they are what is called carriage head bolts here. (domed top coming to a flat that has a square feature where the shank hits the head. The square is used to give a locking feature in the tightening of the nut on the threads.)

English speakers are "often divided by the use of a common language" .

 

[IanN]

I don't recognize the term 'coach bolts' - - - - - - a pic would be useful.
(Guessing they are what is called carriage head bolts here. (domed top coming to a flat that has a square feature where the shank hits the head. The square is used to give a locking feature in the tightening of the nut on the threads.)

English speakers are "often divided by the use of a common language" .

Hi ajoeiam,

You are right - what you call a “carriage bolt” we call a “coach bolt”

All the best,
Ian

 

[BaronJ]

Hi Guys,

Thanks Ian !

Yes ! If you look at the picture carefully you can just make out the flats below the head.

 

[ajoeiam]

Hi ajoeiam,

You are right - what you call a “carriage bolt” we call a “coach bolt”

All the best,
Ian

Thank you for confirming my 'guess'.

Hopefully not sounding like an idjiot but the most common such on this side of the water are rated at only a 36k psi yield strength.
Grade 5 and 8 are supposedly available but in quite a few years of 'playing' with these suckers I've only run into some that look forged and seem to be mostly for railroad (I think) use that are stouter never the grade 5 or 8.

Mentioning because the shown use is to hold a machine tool head in position - - - - someplace where I don't want movement unless I'm moving it (and having 'enjoyed' watching a 3" square (75 mm) section flange some 12" (300 mm) OD flange come off the piece I was machining missing me by hairs and flying across the shop - - - - I was rather jittery for a few hours after that!).

 

[johnwm]

In the UK commercial usage the term for this carriage bolt is "Cup and square"

 

[BaronJ]

Thank you for confirming my 'guess'.

Hopefully not sounding like an idjiot but the most common such on this side of the water are rated at only a 36k psi yield strength.
Grade 5 and 8 are supposedly available but in quite a few years of 'playing' with these suckers I've only run into some that look forged and seem to be mostly for railroad (I think) use that are stouter never the grade 5 or 8.

Mentioning because the shown use is to hold a machine tool head in position - - - - someplace where I don't want movement unless I'm moving it (and having 'enjoyed' watching a 3" square (75 mm) section flange some 12" (300 mm) OD flange come off the piece I was machining missing me by hairs and flying across the shop - - - - I was rather jittery for a few hours after that!).

Hi Joe, Guys,

The coach bolts are perfectly adequate in this application ! Don't forget that there are four bolts, three M12 and one M14 holding this head in place. Normally there would only be three. The issue with three is that the head is pulled when there are only two bolts that are offset from the center. The extra bolt ensures that the head is pulled square onto the face.

 

[goldstar31]

Hi Guys

50 years ago today, I married the 2nd Lady Fellow in dentistry at the Royal college of Surgeons at bEdinburgh. She had spent from 1956 learing to drill and fill holes and would continue to do it until she was too expensive and learned to plsay the barisaxophone and create yet another little one who would follow her Mum- and would do it on Ilkley Moor B'aht Hat.

I\ve digresses but one of our members has summarised it all into 6 lines writte in bad Engllish of how he drilled holes

Sorry but - Xoach bolts!!!!! @3ll, they are no diffrent to carriage bolts. I could never differentiate when it was a coach and when it was a carriage but the village blacksmith made them along with nails right back -- to the Iron Age and no doubt before that.

The heads were square because saolrs especially were found of showing their brawny muscles-- and twisted the heads off. Beieve it or believe it not the Lords of Admiralty actuall specified just how BIG they bolts should be.
It was much later in the Industrial Revoltion that things were round or hexagon and made on the anvil originally with a 'Bob and Aunty'. Do I have to explain what Bob and Aunty did when the rest of the family were abed and not watching.

Well that is the vstory. What went on after the start of many many years has nothing to do with coach bolts


Norman- now a widower nudging 91 years

 

[ShopShoe]

FYI: Historical Comment:

Another piece of information regarding blacksmith forging of carriage bolts is contained in an episode of "The Woodwright's Shop" on American PBS. Season 36, Episode 12, starting about 19:00.

video;_ylt=AwrE19iT9ahgOIIACQ1XNyoA;_ylu=Y29sbwNiZjEEcG9zAzEEdnRpZAMEc2VjA3Nj

What the blacksmith presents in this video seems logical to me as well. Simpler for a smith to do than making a bolt head for a wrench.

--ShopShoe