MadModder

The Shop => Tools => Topic started by: Brass_Machine on February 04, 2011, 12:47:55 PM

Title: 16TPI vs 20TPI
Post by: Brass_Machine on February 04, 2011, 12:47:55 PM

Have to replace some pieces on my mill. Basically my Y axis bit the dust... In the process of finding the parts for my mill, I see there is a choice between 16TPI and 20TPI on the lead screws. Since I am going to replace both X & Y (getting the longer lead screw for X), which is a better option? I have 16TPI now...

Thoughts? I am going to order this afternoon, so whatever advice I can get.

Eric

Title: Re: 16TPI vs 20TPI
Post by: Bogstandard on February 04, 2011, 01:00:03 PM

Eric,

Rather than having to replace your dial handles as well, it will be better for you to stick with the 16TPI, otherwise the graduations on the original handles won't be correct if you swap over to a 20TPI screw.


John

Title: Re: 16TPI vs 20TPI
Post by: Andrew_D on February 04, 2011, 01:41:12 PM

Are the graduations correct now anyways? Are the leadscrews 16tpi or 1.5mm...very close.

My X2 has 16tpi screws and 62.5 division handwheels. Sure it's accurate, but counting in increments of 62.5 gets to be a pain. I sometimes wish it had 20 tpi screws so that I could count in multiples of 50. Plus it moves the table a little slower for the same turning speed, so may improve finish, etc.


Andrew

Title: Re: 16TPI vs 20TPI
Post by: Bernd on February 04, 2011, 02:25:56 PM

This may be a little late but I'll post it anyway.  LINKY (http://www.kingstonemodeleng.com/MachineShop/minimill/minimill.htm)

This is what I did to my Grizzly.

Bernd

Title: Re: 16TPI vs 20TPI
Post by: bambuko on February 04, 2011, 03:27:28 PM

Thanks for the link Bernd,
Changing to 20tpi makes perfect sense, the only thing that confuses me is:

"...MiniMill comes with 16TPI lead screws. One turn of the dial moves the table .063". So for 16 turns of the dial your table will travel 1.008"..."

If it is indeed 16tpi thread, than one turn of the dial moves the table .0625", and for 16 turns of the dial the table will travel 1"
On the other hand (I guess because the dial is rounded up to .063" per turn?) 1" of table travel will show on the dial as 16x.063"=1.008" - but it will still be 1" of table travel...?
You could mark the dial in 1/16" or 1/32" or 1/64" and there would be no error in display  :thumbup: - just your mental arithmetic would get a bit more complicated  :clap:

So, it's a good idea to use 20tpi simply because one turn of the dial moves the table .050" and it is easy to mark the dial in 50 divisions.
The problem with 16tpi is not the table travel, but the difficulty of marking the dial with 62,5 divisions.

Chris

Title: Re: 16TPI vs 20TPI
Post by: 75Plus on February 04, 2011, 03:59:33 PM

This is the LMS kit to convert to 20 tpi. I put it on my HF X-2 and have been happy with it.

http://littlemachineshop.com/products/product_view.php?ProductID=1764&category=879658189

Bambuko, the last division on the collar is half width. 16 turns = exactly 1 inch as measured with a dial caliper.

Joe

Edited to add Pic of collar.

Title: Re: 16TPI vs 20TPI
Post by: bambuko on February 04, 2011, 04:13:18 PM

Thanks Joe (and I see that Andrew_D has also mentioned 62,5)
So for 16 turns the table will travel 1" not 1.008"  :thumbup:

Chris

Title: Re: 16TPI vs 20TPI
Post by: Brass_Machine on February 04, 2011, 05:54:21 PM

Well... I got an offer that will help me fix my mill! Sticking with 16TPI for now.

Many thanks guys!

Eric

Title: Re: 16TPI vs 20TPI
Post by: 1hand on February 04, 2011, 10:37:46 PM

You wouldn't have an X3 would ya? I got all 3 axis left over from my mill.

Matt

Title: Re: 16TPI vs 20TPI
Post by: 1hand on February 04, 2011, 10:43:57 PM

It looks like you have a x2 from your shop pics. I have everything. handwheels, leadscrews,and screw blocks. Might beable to retrofit??? if your other idea don't work

Matt